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-rw-r--r--kernel/rcu/Kconfig171
-rw-r--r--kernel/rcu/Kconfig.debug48
-rw-r--r--kernel/rcu/Makefile7
-rw-r--r--kernel/rcu/rcu.h112
-rw-r--r--kernel/rcu/rcu_segcblist.c239
-rw-r--r--kernel/rcu/rcu_segcblist.h59
-rw-r--r--kernel/rcu/rcuscale.c (renamed from kernel/rcu/rcuperf.c)451
-rw-r--r--kernel/rcu/rcutorture.c1843
-rw-r--r--kernel/rcu/refscale.c898
-rw-r--r--kernel/rcu/srcutiny.c81
-rw-r--r--kernel/rcu/srcutree.c910
-rw-r--r--kernel/rcu/sync.c6
-rw-r--r--kernel/rcu/tasks.h1914
-rw-r--r--kernel/rcu/tiny.c96
-rw-r--r--kernel/rcu/tree.c2814
-rw-r--r--kernel/rcu/tree.h115
-rw-r--r--kernel/rcu/tree_exp.h411
-rw-r--r--kernel/rcu/tree_nocb.h1607
-rw-r--r--kernel/rcu/tree_plugin.h1664
-rw-r--r--kernel/rcu/tree_stall.h497
-rw-r--r--kernel/rcu/update.c472
21 files changed, 10475 insertions, 3940 deletions
diff --git a/kernel/rcu/Kconfig b/kernel/rcu/Kconfig
index 1cc940fef17c..d471d22a5e21 100644
--- a/kernel/rcu/Kconfig
+++ b/kernel/rcu/Kconfig
@@ -8,6 +8,8 @@ menu "RCU Subsystem"
config TREE_RCU
bool
default y if SMP
+ # Dynticks-idle tracking
+ select CONTEXT_TRACKING_IDLE
help
This option selects the RCU implementation that is
designed for very large SMP system with hundreds or
@@ -70,13 +72,63 @@ config TREE_SRCU
help
This option selects the full-fledged version of SRCU.
-config TASKS_RCU
- def_bool PREEMPTION
+config TASKS_RCU_GENERIC
+ def_bool TASKS_RCU || TASKS_RUDE_RCU || TASKS_TRACE_RCU
select SRCU
help
+ This option enables generic infrastructure code supporting
+ task-based RCU implementations. Not for manual selection.
+
+config FORCE_TASKS_RCU
+ bool "Force selection of TASKS_RCU"
+ depends on RCU_EXPERT
+ select TASKS_RCU
+ default n
+ help
+ This option force-enables a task-based RCU implementation
+ that uses only voluntary context switch (not preemption!),
+ idle, and user-mode execution as quiescent states. Not for
+ manual selection in most cases.
+
+config TASKS_RCU
+ bool
+ default n
+ select IRQ_WORK
+
+config FORCE_TASKS_RUDE_RCU
+ bool "Force selection of Tasks Rude RCU"
+ depends on RCU_EXPERT
+ select TASKS_RUDE_RCU
+ default n
+ help
+ This option force-enables a task-based RCU implementation
+ that uses only context switch (including preemption) and
+ user-mode execution as quiescent states. It forces IPIs and
+ context switches on all online CPUs, including idle ones,
+ so use with caution. Not for manual selection in most cases.
+
+config TASKS_RUDE_RCU
+ bool
+ default n
+ select IRQ_WORK
+
+config FORCE_TASKS_TRACE_RCU
+ bool "Force selection of Tasks Trace RCU"
+ depends on RCU_EXPERT
+ select TASKS_TRACE_RCU
+ default n
+ help
This option enables a task-based RCU implementation that uses
- only voluntary context switch (not preemption!), idle, and
- user-mode execution as quiescent states.
+ explicit rcu_read_lock_trace() read-side markers, and allows
+ these readers to appear in the idle loop as well as on the
+ CPU hotplug code paths. It can force IPIs on online CPUs,
+ including idle ones, so use with caution. Not for manual
+ selection in most cases.
+
+config TASKS_TRACE_RCU
+ bool
+ default n
+ select IRQ_WORK
config RCU_STALL_COMMON
def_bool TREE_RCU
@@ -87,7 +139,7 @@ config RCU_STALL_COMMON
making these warnings mandatory for the tree variants.
config RCU_NEED_SEGCBLIST
- def_bool ( TREE_RCU || TREE_SRCU )
+ def_bool ( TREE_RCU || TREE_SRCU || TASKS_RCU_GENERIC )
config RCU_FANOUT
int "Tree-based hierarchical RCU fanout value"
@@ -111,10 +163,12 @@ config RCU_FANOUT
config RCU_FANOUT_LEAF
int "Tree-based hierarchical RCU leaf-level fanout value"
- range 2 64 if 64BIT
- range 2 32 if !64BIT
+ range 2 64 if 64BIT && !RCU_STRICT_GRACE_PERIOD
+ range 2 32 if !64BIT && !RCU_STRICT_GRACE_PERIOD
+ range 2 3 if RCU_STRICT_GRACE_PERIOD
depends on TREE_RCU && RCU_EXPERT
- default 16
+ default 16 if !RCU_STRICT_GRACE_PERIOD
+ default 2 if RCU_STRICT_GRACE_PERIOD
help
This option controls the leaf-level fanout of hierarchical
implementations of RCU, and allows trading off cache misses
@@ -142,28 +196,10 @@ config RCU_FANOUT_LEAF
Take the default if unsure.
-config RCU_FAST_NO_HZ
- bool "Accelerate last non-dyntick-idle CPU's grace periods"
- depends on NO_HZ_COMMON && SMP && RCU_EXPERT
- default n
- help
- This option permits CPUs to enter dynticks-idle state even if
- they have RCU callbacks queued, and prevents RCU from waking
- these CPUs up more than roughly once every four jiffies (by
- default, you can adjust this using the rcutree.rcu_idle_gp_delay
- parameter), thus improving energy efficiency. On the other
- hand, this option increases the duration of RCU grace periods,
- for example, slowing down synchronize_rcu().
-
- Say Y if energy efficiency is critically important, and you
- don't care about increased grace-period durations.
-
- Say N if you are unsure.
-
config RCU_BOOST
bool "Enable RCU priority boosting"
- depends on RT_MUTEXES && PREEMPT_RCU && RCU_EXPERT
- default n
+ depends on (RT_MUTEXES && PREEMPT_RCU && RCU_EXPERT) || PREEMPT_RT
+ default y if PREEMPT_RT
help
This option boosts the priority of preempted RCU readers that
block the current preemptible RCU grace period for too long.
@@ -186,6 +222,20 @@ config RCU_BOOST_DELAY
Accept the default if unsure.
+config RCU_EXP_KTHREAD
+ bool "Perform RCU expedited work in a real-time kthread"
+ depends on RCU_BOOST && RCU_EXPERT
+ default !PREEMPT_RT && NR_CPUS <= 32
+ help
+ Use this option to further reduce the latencies of expedited
+ grace periods at the expense of being more disruptive.
+
+ This option is disabled by default on PREEMPT_RT=y kernels which
+ disable expedited grace periods after boot by unconditionally
+ setting rcupdate.rcu_normal_after_boot=1.
+
+ Accept the default if unsure.
+
config RCU_NOCB_CPU
bool "Offload RCU callback processing from boot-selected CPUs"
depends on TREE_RCU
@@ -195,19 +245,70 @@ config RCU_NOCB_CPU
Use this option to reduce OS jitter for aggressive HPC or
real-time workloads. It can also be used to offload RCU
callback invocation to energy-efficient CPUs in battery-powered
- asymmetric multiprocessors.
+ asymmetric multiprocessors. The price of this reduced jitter
+ is that the overhead of call_rcu() increases and that some
+ workloads will incur significant increases in context-switch
+ rates.
This option offloads callback invocation from the set of CPUs
specified at boot time by the rcu_nocbs parameter. For each
such CPU, a kthread ("rcuox/N") will be created to invoke
callbacks, where the "N" is the CPU being offloaded, and where
- the "p" for RCU-preempt (PREEMPTION kernels) and "s" for RCU-sched
- (!PREEMPTION kernels). Nothing prevents this kthread from running
- on the specified CPUs, but (1) the kthreads may be preempted
- between each callback, and (2) affinity or cgroups can be used
- to force the kthreads to run on whatever set of CPUs is desired.
+ the "x" is "p" for RCU-preempt (PREEMPTION kernels) and "s" for
+ RCU-sched (!PREEMPTION kernels). Nothing prevents this kthread
+ from running on the specified CPUs, but (1) the kthreads may be
+ preempted between each callback, and (2) affinity or cgroups can
+ be used to force the kthreads to run on whatever set of CPUs is
+ desired.
- Say Y here if you want to help to debug reduced OS jitter.
+ Say Y here if you need reduced OS jitter, despite added overhead.
Say N here if you are unsure.
+config RCU_NOCB_CPU_DEFAULT_ALL
+ bool "Offload RCU callback processing from all CPUs by default"
+ depends on RCU_NOCB_CPU
+ default n
+ help
+ Use this option to offload callback processing from all CPUs
+ by default, in the absence of the rcu_nocbs or nohz_full boot
+ parameter. This also avoids the need to use any boot parameters
+ to achieve the effect of offloading all CPUs on boot.
+
+ Say Y here if you want offload all CPUs by default on boot.
+ Say N here if you are unsure.
+
+config RCU_NOCB_CPU_CB_BOOST
+ bool "Offload RCU callback from real-time kthread"
+ depends on RCU_NOCB_CPU && RCU_BOOST
+ default y if PREEMPT_RT
+ help
+ Use this option to invoke offloaded callbacks as SCHED_FIFO
+ to avoid starvation by heavy SCHED_OTHER background load.
+ Of course, running as SCHED_FIFO during callback floods will
+ cause the rcuo[ps] kthreads to monopolize the CPU for hundreds
+ of milliseconds or more. Therefore, when enabling this option,
+ it is your responsibility to ensure that latency-sensitive
+ tasks either run with higher priority or run on some other CPU.
+
+ Say Y here if you want to set RT priority for offloading kthreads.
+ Say N here if you are building a !PREEMPT_RT kernel and are unsure.
+
+config TASKS_TRACE_RCU_READ_MB
+ bool "Tasks Trace RCU readers use memory barriers in user and idle"
+ depends on RCU_EXPERT && TASKS_TRACE_RCU
+ default PREEMPT_RT || NR_CPUS < 8
+ help
+ Use this option to further reduce the number of IPIs sent
+ to CPUs executing in userspace or idle during tasks trace
+ RCU grace periods. Given that a reasonable setting of
+ the rcupdate.rcu_task_ipi_delay kernel boot parameter
+ eliminates such IPIs for many workloads, proper setting
+ of this Kconfig option is important mostly for aggressive
+ real-time installations and for battery-powered devices,
+ hence the default chosen above.
+
+ Say Y here if you hate IPIs.
+ Say N here if you hate read-side memory barriers.
+ Take the default if you are unsure.
+
endmenu # "RCU Subsystem"
diff --git a/kernel/rcu/Kconfig.debug b/kernel/rcu/Kconfig.debug
index 4aa02eee8f6c..1b0c41d490f0 100644
--- a/kernel/rcu/Kconfig.debug
+++ b/kernel/rcu/Kconfig.debug
@@ -23,12 +23,11 @@ config TORTURE_TEST
tristate
default n
-config RCU_PERF_TEST
+config RCU_SCALE_TEST
tristate "performance tests for RCU"
depends on DEBUG_KERNEL
select TORTURE_TEST
select SRCU
- select TASKS_RCU
default n
help
This option provides a kernel module that runs performance
@@ -45,7 +44,6 @@ config RCU_TORTURE_TEST
depends on DEBUG_KERNEL
select TORTURE_TEST
select SRCU
- select TASKS_RCU
default n
help
This option provides a kernel module that runs torture tests
@@ -57,6 +55,22 @@ config RCU_TORTURE_TEST
Say M if you want the RCU torture tests to build as a module.
Say N if you are unsure.
+config RCU_REF_SCALE_TEST
+ tristate "Scalability tests for read-side synchronization (RCU and others)"
+ depends on DEBUG_KERNEL
+ select TORTURE_TEST
+ select SRCU
+ default n
+ help
+ This option provides a kernel module that runs performance tests
+ useful comparing RCU with various read-side synchronization mechanisms.
+ The kernel module may be built after the fact on the running kernel to be
+ tested, if desired.
+
+ Say Y here if you want these performance tests built into the kernel.
+ Say M if you want to build it as a module instead.
+ Say N if you are unsure.
+
config RCU_CPU_STALL_TIMEOUT
int "RCU CPU stall timeout in seconds"
depends on RCU_STALL_COMMON
@@ -68,6 +82,19 @@ config RCU_CPU_STALL_TIMEOUT
RCU grace period persists, additional CPU stall warnings are
printed at more widely spaced intervals.
+config RCU_EXP_CPU_STALL_TIMEOUT
+ int "Expedited RCU CPU stall timeout in milliseconds"
+ depends on RCU_STALL_COMMON
+ range 0 21000
+ default 0
+ help
+ If a given expedited RCU grace period extends more than the
+ specified number of milliseconds, a CPU stall warning is printed.
+ If the RCU grace period persists, additional CPU stall warnings
+ are printed at more widely spaced intervals. A value of zero
+ says to use the RCU_CPU_STALL_TIMEOUT value converted from
+ seconds to milliseconds.
+
config RCU_TRACE
bool "Enable tracing for RCU"
depends on DEBUG_KERNEL
@@ -91,4 +118,19 @@ config RCU_EQS_DEBUG
Say N here if you need ultimate kernel/user switch latencies
Say Y if you are unsure
+config RCU_STRICT_GRACE_PERIOD
+ bool "Provide debug RCU implementation with short grace periods"
+ depends on DEBUG_KERNEL && RCU_EXPERT && NR_CPUS <= 4 && !TINY_RCU
+ default n
+ select PREEMPT_COUNT if PREEMPT=n
+ help
+ Select this option to build an RCU variant that is strict about
+ grace periods, making them as short as it can. This limits
+ scalability, destroys real-time response, degrades battery
+ lifetime and kills performance. Don't try this on large
+ machines, as in systems with more than about 10 or 20 CPUs.
+ But in conjunction with tools like KASAN, it can be helpful
+ when looking for certain types of RCU usage bugs, for example,
+ too-short RCU read-side critical sections.
+
endmenu # "RCU Debugging"
diff --git a/kernel/rcu/Makefile b/kernel/rcu/Makefile
index 82d5fba48b2f..0cfb009a99b9 100644
--- a/kernel/rcu/Makefile
+++ b/kernel/rcu/Makefile
@@ -3,11 +3,16 @@
# and is generally not a function of system call inputs.
KCOV_INSTRUMENT := n
+ifeq ($(CONFIG_KCSAN),y)
+KBUILD_CFLAGS += -g -fno-omit-frame-pointer
+endif
+
obj-y += update.o sync.o
obj-$(CONFIG_TREE_SRCU) += srcutree.o
obj-$(CONFIG_TINY_SRCU) += srcutiny.o
obj-$(CONFIG_RCU_TORTURE_TEST) += rcutorture.o
-obj-$(CONFIG_RCU_PERF_TEST) += rcuperf.o
+obj-$(CONFIG_RCU_SCALE_TEST) += rcuscale.o
+obj-$(CONFIG_RCU_REF_SCALE_TEST) += refscale.o
obj-$(CONFIG_TREE_RCU) += tree.o
obj-$(CONFIG_TINY_RCU) += tiny.o
obj-$(CONFIG_RCU_NEED_SEGCBLIST) += rcu_segcblist.o
diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h
index 05f936ed167a..be5979da07f5 100644
--- a/kernel/rcu/rcu.h
+++ b/kernel/rcu/rcu.h
@@ -12,10 +12,6 @@
#include <trace/events/rcu.h>
-/* Offset to allow distinguishing irq vs. task-based idle entry/exit. */
-#define DYNTICK_IRQ_NONIDLE ((LONG_MAX / 2) + 1)
-
-
/*
* Grace-period counter management.
*/
@@ -23,6 +19,11 @@
#define RCU_SEQ_CTR_SHIFT 2
#define RCU_SEQ_STATE_MASK ((1 << RCU_SEQ_CTR_SHIFT) - 1)
+/* Low-order bit definition for polled grace-period APIs. */
+#define RCU_GET_STATE_COMPLETED 0x1
+
+extern int sysctl_sched_rt_runtime;
+
/*
* Return the counter portion of a sequence number previously returned
* by rcu_seq_snap() or rcu_seq_current().
@@ -118,6 +119,18 @@ static inline bool rcu_seq_done(unsigned long *sp, unsigned long s)
}
/*
+ * Given a snapshot from rcu_seq_snap(), determine whether or not a
+ * full update-side operation has occurred, but do not allow the
+ * (ULONG_MAX / 2) safety-factor/guard-band.
+ */
+static inline bool rcu_seq_done_exact(unsigned long *sp, unsigned long s)
+{
+ unsigned long cur_s = READ_ONCE(*sp);
+
+ return ULONG_CMP_GE(cur_s, s) || ULONG_CMP_LT(cur_s, s - (2 * RCU_SEQ_STATE_MASK + 1));
+}
+
+/*
* Has a grace period completed since the time the old gp_seq was collected?
*/
static inline bool rcu_seq_completed_gp(unsigned long old, unsigned long new)
@@ -167,7 +180,7 @@ static inline unsigned long rcu_seq_diff(unsigned long new, unsigned long old)
# define STATE_RCU_HEAD_READY 0
# define STATE_RCU_HEAD_QUEUED 1
-extern struct debug_obj_descr rcuhead_debug_descr;
+extern const struct debug_obj_descr rcuhead_debug_descr;
static inline int debug_rcu_head_queue(struct rcu_head *head)
{
@@ -198,12 +211,26 @@ static inline void debug_rcu_head_unqueue(struct rcu_head *head)
}
#endif /* #else !CONFIG_DEBUG_OBJECTS_RCU_HEAD */
+extern int rcu_cpu_stall_suppress_at_boot;
+
+static inline bool rcu_stall_is_suppressed_at_boot(void)
+{
+ return rcu_cpu_stall_suppress_at_boot && !rcu_inkernel_boot_has_ended();
+}
+
#ifdef CONFIG_RCU_STALL_COMMON
extern int rcu_cpu_stall_ftrace_dump;
extern int rcu_cpu_stall_suppress;
extern int rcu_cpu_stall_timeout;
+extern int rcu_exp_cpu_stall_timeout;
int rcu_jiffies_till_stall_check(void);
+int rcu_exp_jiffies_till_stall_check(void);
+
+static inline bool rcu_stall_is_suppressed(void)
+{
+ return rcu_stall_is_suppressed_at_boot() || rcu_cpu_stall_suppress;
+}
#define rcu_ftrace_dump_stall_suppress() \
do { \
@@ -218,6 +245,11 @@ do { \
} while (0)
#else /* #endif #ifdef CONFIG_RCU_STALL_COMMON */
+
+static inline bool rcu_stall_is_suppressed(void)
+{
+ return rcu_stall_is_suppressed_at_boot();
+}
#define rcu_ftrace_dump_stall_suppress()
#define rcu_ftrace_dump_stall_unsuppress()
#endif /* #ifdef CONFIG_RCU_STALL_COMMON */
@@ -291,6 +323,8 @@ static inline void rcu_init_levelspread(int *levelspread, const int *levelcnt)
}
}
+extern void rcu_init_geometry(void);
+
/* Returns a pointer to the first leaf rcu_node structure. */
#define rcu_first_leaf_node() (rcu_state.level[rcu_num_lvls - 1])
@@ -325,7 +359,8 @@ static inline void rcu_init_levelspread(int *levelspread, const int *levelcnt)
* Iterate over all possible CPUs in a leaf RCU node.
*/
#define for_each_leaf_node_possible_cpu(rnp, cpu) \
- for ((cpu) = cpumask_next((rnp)->grplo - 1, cpu_possible_mask); \
+ for (WARN_ON_ONCE(!rcu_is_leaf_node(rnp)), \
+ (cpu) = cpumask_next((rnp)->grplo - 1, cpu_possible_mask); \
(cpu) <= rnp->grphi; \
(cpu) = cpumask_next((cpu), cpu_possible_mask))
@@ -335,7 +370,8 @@ static inline void rcu_init_levelspread(int *levelspread, const int *levelcnt)
#define rcu_find_next_bit(rnp, cpu, mask) \
((rnp)->grplo + find_next_bit(&(mask), BITS_PER_LONG, (cpu)))
#define for_each_leaf_node_cpu_mask(rnp, cpu, mask) \
- for ((cpu) = rcu_find_next_bit((rnp), 0, (mask)); \
+ for (WARN_ON_ONCE(!rcu_is_leaf_node(rnp)), \
+ (cpu) = rcu_find_next_bit((rnp), 0, (mask)); \
(cpu) <= rnp->grphi; \
(cpu) = rcu_find_next_bit((rnp), (cpu) + 1 - (rnp->grplo), (mask)))
@@ -359,7 +395,11 @@ do { \
smp_mb__after_unlock_lock(); \
} while (0)
-#define raw_spin_unlock_rcu_node(p) raw_spin_unlock(&ACCESS_PRIVATE(p, lock))
+#define raw_spin_unlock_rcu_node(p) \
+do { \
+ lockdep_assert_irqs_disabled(); \
+ raw_spin_unlock(&ACCESS_PRIVATE(p, lock)); \
+} while (0)
#define raw_spin_lock_irq_rcu_node(p) \
do { \
@@ -368,7 +408,10 @@ do { \
} while (0)
#define raw_spin_unlock_irq_rcu_node(p) \
- raw_spin_unlock_irq(&ACCESS_PRIVATE(p, lock))
+do { \
+ lockdep_assert_irqs_disabled(); \
+ raw_spin_unlock_irq(&ACCESS_PRIVATE(p, lock)); \
+} while (0)
#define raw_spin_lock_irqsave_rcu_node(p, flags) \
do { \
@@ -377,7 +420,10 @@ do { \
} while (0)
#define raw_spin_unlock_irqrestore_rcu_node(p, flags) \
- raw_spin_unlock_irqrestore(&ACCESS_PRIVATE(p, lock), flags)
+do { \
+ lockdep_assert_irqs_disabled(); \
+ raw_spin_unlock_irqrestore(&ACCESS_PRIVATE(p, lock), flags); \
+} while (0)
#define raw_spin_trylock_rcu_node(p) \
({ \
@@ -393,12 +439,6 @@ do { \
#endif /* #if defined(CONFIG_SRCU) || !defined(CONFIG_TINY_RCU) */
-#ifdef CONFIG_SRCU
-void srcu_init(void);
-#else /* #ifdef CONFIG_SRCU */
-static inline void srcu_init(void) { }
-#endif /* #else #ifdef CONFIG_SRCU */
-
#ifdef CONFIG_TINY_RCU
/* Tiny RCU doesn't expedite, as its purpose in life is instead to be tiny. */
static inline bool rcu_gp_is_normal(void) { return true; }
@@ -412,6 +452,11 @@ bool rcu_gp_is_expedited(void); /* Internal RCU use. */
void rcu_expedite_gp(void);
void rcu_unexpedite_gp(void);
void rcupdate_announce_bootup_oddness(void);
+#ifdef CONFIG_TASKS_RCU_GENERIC
+void show_rcu_tasks_gp_kthreads(void);
+#else /* #ifdef CONFIG_TASKS_RCU_GENERIC */
+static inline void show_rcu_tasks_gp_kthreads(void) {}
+#endif /* #else #ifdef CONFIG_TASKS_RCU_GENERIC */
void rcu_request_urgent_qs_task(struct task_struct *t);
#endif /* #else #ifdef CONFIG_TINY_RCU */
@@ -422,6 +467,8 @@ void rcu_request_urgent_qs_task(struct task_struct *t);
enum rcutorture_type {
RCU_FLAVOR,
RCU_TASKS_FLAVOR,
+ RCU_TASKS_RUDE_FLAVOR,
+ RCU_TASKS_TRACING_FLAVOR,
RCU_TRIVIAL_FLAVOR,
SRCU_FLAVOR,
INVALID_RCU_FLAVOR
@@ -435,6 +482,7 @@ void do_trace_rcu_torture_read(const char *rcutorturename,
unsigned long secs,
unsigned long c_old,
unsigned long c);
+void rcu_gp_set_torture_wait(int duration);
#else
static inline void rcutorture_get_gp_data(enum rcutorture_type test_type,
int *flags, unsigned long *gp_seq)
@@ -452,6 +500,7 @@ void do_trace_rcu_torture_read(const char *rcutorturename,
#define do_trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c) \
do { } while (0)
#endif
+static inline void rcu_gp_set_torture_wait(int duration) { }
#endif
#if IS_ENABLED(CONFIG_RCU_TORTURE_TEST) || IS_MODULE(CONFIG_RCU_TORTURE_TEST)
@@ -479,32 +528,59 @@ void srcutorture_get_gp_data(enum rcutorture_type test_type,
#endif
#ifdef CONFIG_TINY_RCU
+static inline bool rcu_dynticks_zero_in_eqs(int cpu, int *vp) { return false; }
static inline unsigned long rcu_get_gp_seq(void) { return 0; }
static inline unsigned long rcu_exp_batches_completed(void) { return 0; }
static inline unsigned long
srcu_batches_completed(struct srcu_struct *sp) { return 0; }
static inline void rcu_force_quiescent_state(void) { }
+static inline bool rcu_check_boost_fail(unsigned long gp_state, int *cpup) { return true; }
static inline void show_rcu_gp_kthreads(void) { }
static inline int rcu_get_gp_kthreads_prio(void) { return 0; }
static inline void rcu_fwd_progress_check(unsigned long j) { }
+static inline void rcu_gp_slow_register(atomic_t *rgssp) { }
+static inline void rcu_gp_slow_unregister(atomic_t *rgssp) { }
#else /* #ifdef CONFIG_TINY_RCU */
+bool rcu_dynticks_zero_in_eqs(int cpu, int *vp);
unsigned long rcu_get_gp_seq(void);
unsigned long rcu_exp_batches_completed(void);
unsigned long srcu_batches_completed(struct srcu_struct *sp);
+bool rcu_check_boost_fail(unsigned long gp_state, int *cpup);
void show_rcu_gp_kthreads(void);
int rcu_get_gp_kthreads_prio(void);
void rcu_fwd_progress_check(unsigned long j);
void rcu_force_quiescent_state(void);
extern struct workqueue_struct *rcu_gp_wq;
+#ifdef CONFIG_RCU_EXP_KTHREAD
+extern struct kthread_worker *rcu_exp_gp_kworker;
+extern struct kthread_worker *rcu_exp_par_gp_kworker;
+#else /* !CONFIG_RCU_EXP_KTHREAD */
extern struct workqueue_struct *rcu_par_gp_wq;
+#endif /* CONFIG_RCU_EXP_KTHREAD */
+void rcu_gp_slow_register(atomic_t *rgssp);
+void rcu_gp_slow_unregister(atomic_t *rgssp);
#endif /* #else #ifdef CONFIG_TINY_RCU */
#ifdef CONFIG_RCU_NOCB_CPU
-bool rcu_is_nocb_cpu(int cpu);
void rcu_bind_current_to_nocb(void);
#else
-static inline bool rcu_is_nocb_cpu(int cpu) { return false; }
static inline void rcu_bind_current_to_nocb(void) { }
#endif
+#if !defined(CONFIG_TINY_RCU) && defined(CONFIG_TASKS_RCU)
+void show_rcu_tasks_classic_gp_kthread(void);
+#else
+static inline void show_rcu_tasks_classic_gp_kthread(void) {}
+#endif
+#if !defined(CONFIG_TINY_RCU) && defined(CONFIG_TASKS_RUDE_RCU)
+void show_rcu_tasks_rude_gp_kthread(void);
+#else
+static inline void show_rcu_tasks_rude_gp_kthread(void) {}
+#endif
+#if !defined(CONFIG_TINY_RCU) && defined(CONFIG_TASKS_TRACE_RCU)
+void show_rcu_tasks_trace_gp_kthread(void);
+#else
+static inline void show_rcu_tasks_trace_gp_kthread(void) {}
+#endif
+
#endif /* __LINUX_RCU_H */
diff --git a/kernel/rcu/rcu_segcblist.c b/kernel/rcu/rcu_segcblist.c
index 5f4fd3b8777c..c54ea2b6a36b 100644
--- a/kernel/rcu/rcu_segcblist.c
+++ b/kernel/rcu/rcu_segcblist.c
@@ -7,10 +7,10 @@
* Authors: Paul E. McKenney <paulmck@linux.ibm.com>
*/
-#include <linux/types.h>
-#include <linux/kernel.h>
+#include <linux/cpu.h>
#include <linux/interrupt.h>
-#include <linux/rcupdate.h>
+#include <linux/kernel.h>
+#include <linux/types.h>
#include "rcu_segcblist.h"
@@ -88,23 +88,135 @@ static void rcu_segcblist_set_len(struct rcu_segcblist *rsclp, long v)
#endif
}
+/* Get the length of a segment of the rcu_segcblist structure. */
+static long rcu_segcblist_get_seglen(struct rcu_segcblist *rsclp, int seg)
+{
+ return READ_ONCE(rsclp->seglen[seg]);
+}
+
+/* Return number of callbacks in segmented callback list by summing seglen. */
+long rcu_segcblist_n_segment_cbs(struct rcu_segcblist *rsclp)
+{
+ long len = 0;
+ int i;
+
+ for (i = RCU_DONE_TAIL; i < RCU_CBLIST_NSEGS; i++)
+ len += rcu_segcblist_get_seglen(rsclp, i);
+
+ return len;
+}
+
+/* Set the length of a segment of the rcu_segcblist structure. */
+static void rcu_segcblist_set_seglen(struct rcu_segcblist *rsclp, int seg, long v)
+{
+ WRITE_ONCE(rsclp->seglen[seg], v);
+}
+
+/* Increase the numeric length of a segment by a specified amount. */
+static void rcu_segcblist_add_seglen(struct rcu_segcblist *rsclp, int seg, long v)
+{
+ WRITE_ONCE(rsclp->seglen[seg], rsclp->seglen[seg] + v);
+}
+
+/* Move from's segment length to to's segment. */
+static void rcu_segcblist_move_seglen(struct rcu_segcblist *rsclp, int from, int to)
+{
+ long len;
+
+ if (from == to)
+ return;
+
+ len = rcu_segcblist_get_seglen(rsclp, from);
+ if (!len)
+ return;
+
+ rcu_segcblist_add_seglen(rsclp, to, len);
+ rcu_segcblist_set_seglen(rsclp, from, 0);
+}
+
+/* Increment segment's length. */
+static void rcu_segcblist_inc_seglen(struct rcu_segcblist *rsclp, int seg)
+{
+ rcu_segcblist_add_seglen(rsclp, seg, 1);
+}
+
/*
* Increase the numeric length of an rcu_segcblist structure by the
* specified amount, which can be negative. This can cause the ->len
* field to disagree with the actual number of callbacks on the structure.
* This increase is fully ordered with respect to the callers accesses
* both before and after.
+ *
+ * So why on earth is a memory barrier required both before and after
+ * the update to the ->len field???
+ *
+ * The reason is that rcu_barrier() locklessly samples each CPU's ->len
+ * field, and if a given CPU's field is zero, avoids IPIing that CPU.
+ * This can of course race with both queuing and invoking of callbacks.
+ * Failing to correctly handle either of these races could result in
+ * rcu_barrier() failing to IPI a CPU that actually had callbacks queued
+ * which rcu_barrier() was obligated to wait on. And if rcu_barrier()
+ * failed to wait on such a callback, unloading certain kernel modules
+ * would result in calls to functions whose code was no longer present in
+ * the kernel, for but one example.
+ *
+ * Therefore, ->len transitions from 1->0 and 0->1 have to be carefully
+ * ordered with respect with both list modifications and the rcu_barrier().
+ *
+ * The queuing case is CASE 1 and the invoking case is CASE 2.
+ *
+ * CASE 1: Suppose that CPU 0 has no callbacks queued, but invokes
+ * call_rcu() just as CPU 1 invokes rcu_barrier(). CPU 0's ->len field
+ * will transition from 0->1, which is one of the transitions that must
+ * be handled carefully. Without the full memory barriers after the ->len
+ * update and at the beginning of rcu_barrier(), the following could happen:
+ *
+ * CPU 0 CPU 1
+ *
+ * call_rcu().
+ * rcu_barrier() sees ->len as 0.
+ * set ->len = 1.
+ * rcu_barrier() does nothing.
+ * module is unloaded.
+ * callback invokes unloaded function!
+ *
+ * With the full barriers, any case where rcu_barrier() sees ->len as 0 will
+ * have unambiguously preceded the return from the racing call_rcu(), which
+ * means that this call_rcu() invocation is OK to not wait on. After all,
+ * you are supposed to make sure that any problematic call_rcu() invocations
+ * happen before the rcu_barrier().
+ *
+ *
+ * CASE 2: Suppose that CPU 0 is invoking its last callback just as
+ * CPU 1 invokes rcu_barrier(). CPU 0's ->len field will transition from
+ * 1->0, which is one of the transitions that must be handled carefully.
+ * Without the full memory barriers before the ->len update and at the
+ * end of rcu_barrier(), the following could happen:
+ *
+ * CPU 0 CPU 1
+ *
+ * start invoking last callback
+ * set ->len = 0 (reordered)
+ * rcu_barrier() sees ->len as 0
+ * rcu_barrier() does nothing.
+ * module is unloaded
+ * callback executing after unloaded!
+ *
+ * With the full barriers, any case where rcu_barrier() sees ->len as 0
+ * will be fully ordered after the completion of the callback function,
+ * so that the module unloading operation is completely safe.
+ *
*/
-static void rcu_segcblist_add_len(struct rcu_segcblist *rsclp, long v)
+void rcu_segcblist_add_len(struct rcu_segcblist *rsclp, long v)
{
#ifdef CONFIG_RCU_NOCB_CPU
- smp_mb__before_atomic(); /* Up to the caller! */
+ smp_mb__before_atomic(); // Read header comment above.
atomic_long_add(v, &rsclp->len);
- smp_mb__after_atomic(); /* Up to the caller! */
+ smp_mb__after_atomic(); // Read header comment above.
#else
- smp_mb(); /* Up to the caller! */
+ smp_mb(); // Read header comment above.
WRITE_ONCE(rsclp->len, rsclp->len + v);
- smp_mb(); /* Up to the caller! */
+ smp_mb(); // Read header comment above.
#endif
}
@@ -120,26 +232,6 @@ void rcu_segcblist_inc_len(struct rcu_segcblist *rsclp)
}
/*
- * Exchange the numeric length of the specified rcu_segcblist structure
- * with the specified value. This can cause the ->len field to disagree
- * with the actual number of callbacks on the structure. This exchange is
- * fully ordered with respect to the callers accesses both before and after.
- */
-static long rcu_segcblist_xchg_len(struct rcu_segcblist *rsclp, long v)
-{
-#ifdef CONFIG_RCU_NOCB_CPU
- return atomic_long_xchg(&rsclp->len, v);
-#else
- long ret = rsclp->len;
-
- smp_mb(); /* Up to the caller! */
- WRITE_ONCE(rsclp->len, v);
- smp_mb(); /* Up to the caller! */
- return ret;
-#endif
-}
-
-/*
* Initialize an rcu_segcblist structure.
*/
void rcu_segcblist_init(struct rcu_segcblist *rsclp)
@@ -149,10 +241,12 @@ void rcu_segcblist_init(struct rcu_segcblist *rsclp)
BUILD_BUG_ON(RCU_NEXT_TAIL + 1 != ARRAY_SIZE(rsclp->gp_seq));
BUILD_BUG_ON(ARRAY_SIZE(rsclp->tails) != ARRAY_SIZE(rsclp->gp_seq));
rsclp->head = NULL;
- for (i = 0; i < RCU_CBLIST_NSEGS; i++)
+ for (i = 0; i < RCU_CBLIST_NSEGS; i++) {
rsclp->tails[i] = &rsclp->head;
+ rcu_segcblist_set_seglen(rsclp, i, 0);
+ }
rcu_segcblist_set_len(rsclp, 0);
- rsclp->enabled = 1;
+ rcu_segcblist_set_flags(rsclp, SEGCBLIST_ENABLED);
}
/*
@@ -163,16 +257,18 @@ void rcu_segcblist_disable(struct rcu_segcblist *rsclp)
{
WARN_ON_ONCE(!rcu_segcblist_empty(rsclp));
WARN_ON_ONCE(rcu_segcblist_n_cbs(rsclp));
- rsclp->enabled = 0;
+ rcu_segcblist_clear_flags(rsclp, SEGCBLIST_ENABLED);
}
/*
- * Mark the specified rcu_segcblist structure as offloaded. This
- * structure must be empty.
+ * Mark the specified rcu_segcblist structure as offloaded (or not)
*/
-void rcu_segcblist_offload(struct rcu_segcblist *rsclp)
+void rcu_segcblist_offload(struct rcu_segcblist *rsclp, bool offload)
{
- rsclp->offloaded = 1;
+ if (offload)
+ rcu_segcblist_set_flags(rsclp, SEGCBLIST_LOCKING | SEGCBLIST_OFFLOADED);
+ else
+ rcu_segcblist_clear_flags(rsclp, SEGCBLIST_OFFLOADED);
}
/*
@@ -182,7 +278,7 @@ void rcu_segcblist_offload(struct rcu_segcblist *rsclp)
bool rcu_segcblist_ready_cbs(struct rcu_segcblist *rsclp)
{
return rcu_segcblist_is_enabled(rsclp) &&
- &rsclp->head != rsclp->tails[RCU_DONE_TAIL];
+ &rsclp->head != READ_ONCE(rsclp->tails[RCU_DONE_TAIL]);
}
/*
@@ -245,7 +341,7 @@ void rcu_segcblist_enqueue(struct rcu_segcblist *rsclp,
struct rcu_head *rhp)
{
rcu_segcblist_inc_len(rsclp);
- smp_mb(); /* Ensure counts are updated before callback is enqueued. */
+ rcu_segcblist_inc_seglen(rsclp, RCU_NEXT_TAIL);
rhp->next = NULL;
WRITE_ONCE(*rsclp->tails[RCU_NEXT_TAIL], rhp);
WRITE_ONCE(rsclp->tails[RCU_NEXT_TAIL], &rhp->next);
@@ -274,6 +370,7 @@ bool rcu_segcblist_entrain(struct rcu_segcblist *rsclp,
for (i = RCU_NEXT_TAIL; i > RCU_DONE_TAIL; i--)
if (rsclp->tails[i] != rsclp->tails[i - 1])
break;
+ rcu_segcblist_inc_seglen(rsclp, i);
WRITE_ONCE(*rsclp->tails[i], rhp);
for (; i <= RCU_NEXT_TAIL; i++)
WRITE_ONCE(rsclp->tails[i], &rhp->next);
@@ -281,21 +378,6 @@ bool rcu_segcblist_entrain(struct rcu_segcblist *rsclp,
}
/*
- * Extract only the counts from the specified rcu_segcblist structure,
- * and place them in the specified rcu_cblist structure. This function
- * supports both callback orphaning and invocation, hence the separation
- * of counts and callbacks. (Callbacks ready for invocation must be
- * orphaned and adopted separately from pending callbacks, but counts
- * apply to all callbacks. Locking must be used to make sure that
- * both orphaned-callbacks lists are consistent.)
- */
-void rcu_segcblist_extract_count(struct rcu_segcblist *rsclp,
- struct rcu_cblist *rclp)
-{
- rclp->len = rcu_segcblist_xchg_len(rsclp, 0);
-}
-
-/*
* Extract only those callbacks ready to be invoked from the specified
* rcu_segcblist structure and place them in the specified rcu_cblist
* structure.
@@ -307,6 +389,7 @@ void rcu_segcblist_extract_done_cbs(struct rcu_segcblist *rsclp,
if (!rcu_segcblist_ready_cbs(rsclp))
return; /* Nothing to do. */
+ rclp->len = rcu_segcblist_get_seglen(rsclp, RCU_DONE_TAIL);
*rclp->tail = rsclp->head;
WRITE_ONCE(rsclp->head, *rsclp->tails[RCU_DONE_TAIL]);
WRITE_ONCE(*rsclp->tails[RCU_DONE_TAIL], NULL);
@@ -314,6 +397,7 @@ void rcu_segcblist_extract_done_cbs(struct rcu_segcblist *rsclp,
for (i = RCU_CBLIST_NSEGS - 1; i >= RCU_DONE_TAIL; i--)
if (rsclp->tails[i] == rsclp->tails[RCU_DONE_TAIL])
WRITE_ONCE(rsclp->tails[i], &rsclp->head);
+ rcu_segcblist_set_seglen(rsclp, RCU_DONE_TAIL, 0);
}
/*
@@ -330,11 +414,15 @@ void rcu_segcblist_extract_pend_cbs(struct rcu_segcblist *rsclp,
if (!rcu_segcblist_pend_cbs(rsclp))
return; /* Nothing to do. */
+ rclp->len = 0;
*rclp->tail = *rsclp->tails[RCU_DONE_TAIL];
rclp->tail = rsclp->tails[RCU_NEXT_TAIL];
WRITE_ONCE(*rsclp->tails[RCU_DONE_TAIL], NULL);
- for (i = RCU_DONE_TAIL + 1; i < RCU_CBLIST_NSEGS; i++)
+ for (i = RCU_DONE_TAIL + 1; i < RCU_CBLIST_NSEGS; i++) {
+ rclp->len += rcu_segcblist_get_seglen(rsclp, i);
WRITE_ONCE(rsclp->tails[i], rsclp->tails[RCU_DONE_TAIL]);
+ rcu_segcblist_set_seglen(rsclp, i, 0);
+ }
}
/*
@@ -345,7 +433,6 @@ void rcu_segcblist_insert_count(struct rcu_segcblist *rsclp,
struct rcu_cblist *rclp)
{
rcu_segcblist_add_len(rsclp, rclp->len);
- rclp->len = 0;
}
/*
@@ -359,6 +446,7 @@ void rcu_segcblist_insert_done_cbs(struct rcu_segcblist *rsclp,
if (!rclp->head)
return; /* No callbacks to move. */
+ rcu_segcblist_add_seglen(rsclp, RCU_DONE_TAIL, rclp->len);
*rclp->tail = rsclp->head;
WRITE_ONCE(rsclp->head, rclp->head);
for (i = RCU_DONE_TAIL; i < RCU_CBLIST_NSEGS; i++)
@@ -379,10 +467,10 @@ void rcu_segcblist_insert_pend_cbs(struct rcu_segcblist *rsclp,
{
if (!rclp->head)
return; /* Nothing to do. */
+
+ rcu_segcblist_add_seglen(rsclp, RCU_NEXT_TAIL, rclp->len);
WRITE_ONCE(*rsclp->tails[RCU_NEXT_TAIL], rclp->head);
WRITE_ONCE(rsclp->tails[RCU_NEXT_TAIL], rclp->tail);
- rclp->head = NULL;
- rclp->tail = &rclp->head;
}
/*
@@ -405,6 +493,7 @@ void rcu_segcblist_advance(struct rcu_segcblist *rsclp, unsigned long seq)
if (ULONG_CMP_LT(seq, rsclp->gp_seq[i]))
break;
WRITE_ONCE(rsclp->tails[RCU_DONE_TAIL], rsclp->tails[i]);
+ rcu_segcblist_move_seglen(rsclp, i, RCU_DONE_TAIL);
}
/* If no callbacks moved, nothing more need be done. */
@@ -416,15 +505,16 @@ void rcu_segcblist_advance(struct rcu_segcblist *rsclp, unsigned long seq)
WRITE_ONCE(rsclp->tails[j], rsclp->tails[RCU_DONE_TAIL]);
/*
- * Callbacks moved, so clean up the misordered ->tails[] pointers
- * that now point into the middle of the list of ready-to-invoke
- * callbacks. The overall effect is to copy down the later pointers
- * into the gap that was created by the now-ready segments.
+ * Callbacks moved, so there might be an empty RCU_WAIT_TAIL
+ * and a non-empty RCU_NEXT_READY_TAIL. If so, copy the
+ * RCU_NEXT_READY_TAIL segment to fill the RCU_WAIT_TAIL gap
+ * created by the now-ready-to-invoke segments.
*/
for (j = RCU_WAIT_TAIL; i < RCU_NEXT_TAIL; i++, j++) {
if (rsclp->tails[j] == rsclp->tails[RCU_NEXT_TAIL])
break; /* No more callbacks. */
WRITE_ONCE(rsclp->tails[j], rsclp->tails[i]);
+ rcu_segcblist_move_seglen(rsclp, i, j);
rsclp->gp_seq[j] = rsclp->gp_seq[i];
}
}
@@ -446,7 +536,7 @@ void rcu_segcblist_advance(struct rcu_segcblist *rsclp, unsigned long seq)
*/
bool rcu_segcblist_accelerate(struct rcu_segcblist *rsclp, unsigned long seq)
{
- int i;
+ int i, j;
WARN_ON_ONCE(!rcu_segcblist_is_enabled(rsclp));
if (rcu_segcblist_restempty(rsclp, RCU_DONE_TAIL))
@@ -477,10 +567,22 @@ bool rcu_segcblist_accelerate(struct rcu_segcblist *rsclp, unsigned long seq)
* Also advance to the oldest segment of callbacks whose
* ->gp_seq[] completion is at or after that passed in via "seq",
* skipping any empty segments.
+ *
+ * Note that segment "i" (and any lower-numbered segments
+ * containing older callbacks) will be unaffected, and their
+ * grace-period numbers remain unchanged. For example, if i ==
+ * WAIT_TAIL, then neither WAIT_TAIL nor DONE_TAIL will be touched.
+ * Instead, the CBs in NEXT_TAIL will be merged with those in
+ * NEXT_READY_TAIL and the grace-period number of NEXT_READY_TAIL
+ * would be updated. NEXT_TAIL would then be empty.
*/
- if (++i >= RCU_NEXT_TAIL)
+ if (rcu_segcblist_restempty(rsclp, i) || ++i >= RCU_NEXT_TAIL)
return false;
+ /* Accounting: everything below i is about to get merged into i. */
+ for (j = i + 1; j <= RCU_NEXT_TAIL; j++)
+ rcu_segcblist_move_seglen(rsclp, j, i);
+
/*
* Merge all later callbacks, including newly arrived callbacks,
* into the segment located by the for-loop above. Assign "seq"
@@ -508,13 +610,24 @@ void rcu_segcblist_merge(struct rcu_segcblist *dst_rsclp,
struct rcu_cblist donecbs;
struct rcu_cblist pendcbs;
+ lockdep_assert_cpus_held();
+
rcu_cblist_init(&donecbs);
rcu_cblist_init(&pendcbs);
- rcu_segcblist_extract_count(src_rsclp, &donecbs);
+
rcu_segcblist_extract_done_cbs(src_rsclp, &donecbs);
rcu_segcblist_extract_pend_cbs(src_rsclp, &pendcbs);
+
+ /*
+ * No need smp_mb() before setting length to 0, because CPU hotplug
+ * lock excludes rcu_barrier.
+ */
+ rcu_segcblist_set_len(src_rsclp, 0);
+
rcu_segcblist_insert_count(dst_rsclp, &donecbs);
+ rcu_segcblist_insert_count(dst_rsclp, &pendcbs);
rcu_segcblist_insert_done_cbs(dst_rsclp, &donecbs);
rcu_segcblist_insert_pend_cbs(dst_rsclp, &pendcbs);
+
rcu_segcblist_init(src_rsclp);
}
diff --git a/kernel/rcu/rcu_segcblist.h b/kernel/rcu/rcu_segcblist.h
index 5c293afc07b8..431cee212467 100644
--- a/kernel/rcu/rcu_segcblist.h
+++ b/kernel/rcu/rcu_segcblist.h
@@ -15,6 +15,9 @@ static inline long rcu_cblist_n_cbs(struct rcu_cblist *rclp)
return READ_ONCE(rclp->len);
}
+/* Return number of callbacks in segmented callback list by summing seglen. */
+long rcu_segcblist_n_segment_cbs(struct rcu_segcblist *rsclp);
+
void rcu_cblist_init(struct rcu_cblist *rclp);
void rcu_cblist_enqueue(struct rcu_cblist *rclp, struct rcu_head *rhp);
void rcu_cblist_flush_enqueue(struct rcu_cblist *drclp,
@@ -50,19 +53,53 @@ static inline long rcu_segcblist_n_cbs(struct rcu_segcblist *rsclp)
#endif
}
+static inline void rcu_segcblist_set_flags(struct rcu_segcblist *rsclp,
+ int flags)
+{
+ WRITE_ONCE(rsclp->flags, rsclp->flags | flags);
+}
+
+static inline void rcu_segcblist_clear_flags(struct rcu_segcblist *rsclp,
+ int flags)
+{
+ WRITE_ONCE(rsclp->flags, rsclp->flags & ~flags);
+}
+
+static inline bool rcu_segcblist_test_flags(struct rcu_segcblist *rsclp,
+ int flags)
+{
+ return READ_ONCE(rsclp->flags) & flags;
+}
+
/*
* Is the specified rcu_segcblist enabled, for example, not corresponding
* to an offline CPU?
*/
static inline bool rcu_segcblist_is_enabled(struct rcu_segcblist *rsclp)
{
- return rsclp->enabled;
+ return rcu_segcblist_test_flags(rsclp, SEGCBLIST_ENABLED);
}
-/* Is the specified rcu_segcblist offloaded? */
+/*
+ * Is the specified rcu_segcblist NOCB offloaded (or in the middle of the
+ * [de]offloading process)?
+ */
static inline bool rcu_segcblist_is_offloaded(struct rcu_segcblist *rsclp)
{
- return rsclp->offloaded;
+ if (IS_ENABLED(CONFIG_RCU_NOCB_CPU) &&
+ rcu_segcblist_test_flags(rsclp, SEGCBLIST_LOCKING))
+ return true;
+
+ return false;
+}
+
+static inline bool rcu_segcblist_completely_offloaded(struct rcu_segcblist *rsclp)
+{
+ if (IS_ENABLED(CONFIG_RCU_NOCB_CPU) &&
+ !rcu_segcblist_test_flags(rsclp, SEGCBLIST_RCU_CORE))
+ return true;
+
+ return false;
}
/*
@@ -75,10 +112,22 @@ static inline bool rcu_segcblist_restempty(struct rcu_segcblist *rsclp, int seg)
return !READ_ONCE(*READ_ONCE(rsclp->tails[seg]));
}
+/*
+ * Is the specified segment of the specified rcu_segcblist structure
+ * empty of callbacks?
+ */
+static inline bool rcu_segcblist_segempty(struct rcu_segcblist *rsclp, int seg)
+{
+ if (seg == RCU_DONE_TAIL)
+ return &rsclp->head == rsclp->tails[RCU_DONE_TAIL];
+ return rsclp->tails[seg - 1] == rsclp->tails[seg];
+}
+
void rcu_segcblist_inc_len(struct rcu_segcblist *rsclp);
+void rcu_segcblist_add_len(struct rcu_segcblist *rsclp, long v);
void rcu_segcblist_init(struct rcu_segcblist *rsclp);
void rcu_segcblist_disable(struct rcu_segcblist *rsclp);
-void rcu_segcblist_offload(struct rcu_segcblist *rsclp);
+void rcu_segcblist_offload(struct rcu_segcblist *rsclp, bool offload);
bool rcu_segcblist_ready_cbs(struct rcu_segcblist *rsclp);
bool rcu_segcblist_pend_cbs(struct rcu_segcblist *rsclp);
struct rcu_head *rcu_segcblist_first_cb(struct rcu_segcblist *rsclp);
@@ -88,8 +137,6 @@ void rcu_segcblist_enqueue(struct rcu_segcblist *rsclp,
struct rcu_head *rhp);
bool rcu_segcblist_entrain(struct rcu_segcblist *rsclp,
struct rcu_head *rhp);
-void rcu_segcblist_extract_count(struct rcu_segcblist *rsclp,
- struct rcu_cblist *rclp);
void rcu_segcblist_extract_done_cbs(struct rcu_segcblist *rsclp,
struct rcu_cblist *rclp);
void rcu_segcblist_extract_pend_cbs(struct rcu_segcblist *rsclp,
diff --git a/kernel/rcu/rcuperf.c b/kernel/rcu/rcuscale.c
index da94b89cd531..3ef02d4a8108 100644
--- a/kernel/rcu/rcuperf.c
+++ b/kernel/rcu/rcuscale.c
@@ -1,6 +1,6 @@
// SPDX-License-Identifier: GPL-2.0+
/*
- * Read-Copy Update module-based performance-test facility
+ * Read-Copy Update module-based scalability-test facility
*
* Copyright (C) IBM Corporation, 2015
*
@@ -12,6 +12,7 @@
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/init.h>
+#include <linux/mm.h>
#include <linux/module.h>
#include <linux/kthread.h>
#include <linux/err.h>
@@ -37,19 +38,20 @@
#include <asm/byteorder.h>
#include <linux/torture.h>
#include <linux/vmalloc.h>
+#include <linux/rcupdate_trace.h>
#include "rcu.h"
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Paul E. McKenney <paulmck@linux.ibm.com>");
-#define PERF_FLAG "-perf:"
-#define PERFOUT_STRING(s) \
- pr_alert("%s" PERF_FLAG " %s\n", perf_type, s)
-#define VERBOSE_PERFOUT_STRING(s) \
- do { if (verbose) pr_alert("%s" PERF_FLAG " %s\n", perf_type, s); } while (0)
-#define VERBOSE_PERFOUT_ERRSTRING(s) \
- do { if (verbose) pr_alert("%s" PERF_FLAG "!!! %s\n", perf_type, s); } while (0)
+#define SCALE_FLAG "-scale:"
+#define SCALEOUT_STRING(s) \
+ pr_alert("%s" SCALE_FLAG " %s\n", scale_type, s)
+#define VERBOSE_SCALEOUT_STRING(s) \
+ do { if (verbose) pr_alert("%s" SCALE_FLAG " %s\n", scale_type, s); } while (0)
+#define SCALEOUT_ERRSTRING(s) \
+ pr_alert("%s" SCALE_FLAG "!!! %s\n", scale_type, s)
/*
* The intended use cases for the nreaders and nwriters module parameters
@@ -60,20 +62,25 @@ MODULE_AUTHOR("Paul E. McKenney <paulmck@linux.ibm.com>");
* nr_cpus for a mixed reader/writer test.
*
* 2. Specify the nr_cpus kernel boot parameter, but set
- * rcuperf.nreaders to zero. This will set nwriters to the
+ * rcuscale.nreaders to zero. This will set nwriters to the
* value specified by nr_cpus for an update-only test.
*
* 3. Specify the nr_cpus kernel boot parameter, but set
- * rcuperf.nwriters to zero. This will set nreaders to the
+ * rcuscale.nwriters to zero. This will set nreaders to the
* value specified by nr_cpus for a read-only test.
*
* Various other use cases may of course be specified.
+ *
+ * Note that this test's readers are intended only as a test load for
+ * the writers. The reader scalability statistics will be overly
+ * pessimistic due to the per-critical-section interrupt disabling,
+ * test-end checks, and the pair of calls through pointers.
*/
#ifdef MODULE
-# define RCUPERF_SHUTDOWN 0
+# define RCUSCALE_SHUTDOWN 0
#else
-# define RCUPERF_SHUTDOWN 1
+# define RCUSCALE_SHUTDOWN 1
#endif
torture_param(bool, gp_async, false, "Use asynchronous GP wait primitives");
@@ -82,15 +89,16 @@ torture_param(bool, gp_exp, false, "Use expedited GP wait primitives");
torture_param(int, holdoff, 10, "Holdoff time before test start (s)");
torture_param(int, nreaders, -1, "Number of RCU reader threads");
torture_param(int, nwriters, -1, "Number of RCU updater threads");
-torture_param(bool, shutdown, RCUPERF_SHUTDOWN,
- "Shutdown at end of performance tests.");
+torture_param(bool, shutdown, RCUSCALE_SHUTDOWN,
+ "Shutdown at end of scalability tests.");
torture_param(int, verbose, 1, "Enable verbose debugging printk()s");
torture_param(int, writer_holdoff, 0, "Holdoff (us) between GPs, zero to disable");
-torture_param(int, kfree_rcu_test, 0, "Do we run a kfree_rcu() perf test?");
+torture_param(int, kfree_rcu_test, 0, "Do we run a kfree_rcu() scale test?");
+torture_param(int, kfree_mult, 1, "Multiple of kfree_obj size to allocate.");
-static char *perf_type = "rcu";
-module_param(perf_type, charp, 0444);
-MODULE_PARM_DESC(perf_type, "Type of RCU to performance-test (rcu, srcu, ...)");
+static char *scale_type = "rcu";
+module_param(scale_type, charp, 0444);
+MODULE_PARM_DESC(scale_type, "Type of RCU to scalability-test (rcu, srcu, ...)");
static int nrealreaders;
static int nrealwriters;
@@ -100,12 +108,12 @@ static struct task_struct *shutdown_task;
static u64 **writer_durations;
static int *writer_n_durations;
-static atomic_t n_rcu_perf_reader_started;
-static atomic_t n_rcu_perf_writer_started;
-static atomic_t n_rcu_perf_writer_finished;
+static atomic_t n_rcu_scale_reader_started;
+static atomic_t n_rcu_scale_writer_started;
+static atomic_t n_rcu_scale_writer_finished;
static wait_queue_head_t shutdown_wq;
-static u64 t_rcu_perf_writer_started;
-static u64 t_rcu_perf_writer_finished;
+static u64 t_rcu_scale_writer_started;
+static u64 t_rcu_scale_writer_finished;
static unsigned long b_rcu_gp_test_started;
static unsigned long b_rcu_gp_test_finished;
static DEFINE_PER_CPU(atomic_t, n_async_inflight);
@@ -117,7 +125,7 @@ static DEFINE_PER_CPU(atomic_t, n_async_inflight);
* Operations vector for selecting different types of tests.
*/
-struct rcu_perf_ops {
+struct rcu_scale_ops {
int ptype;
void (*init)(void);
void (*cleanup)(void);
@@ -133,19 +141,19 @@ struct rcu_perf_ops {
const char *name;
};
-static struct rcu_perf_ops *cur_ops;
+static struct rcu_scale_ops *cur_ops;
/*
- * Definitions for rcu perf testing.
+ * Definitions for rcu scalability testing.
*/
-static int rcu_perf_read_lock(void) __acquires(RCU)
+static int rcu_scale_read_lock(void) __acquires(RCU)
{
rcu_read_lock();
return 0;
}
-static void rcu_perf_read_unlock(int idx) __releases(RCU)
+static void rcu_scale_read_unlock(int idx) __releases(RCU)
{
rcu_read_unlock();
}
@@ -155,15 +163,15 @@ static unsigned long __maybe_unused rcu_no_completed(void)
return 0;
}
-static void rcu_sync_perf_init(void)
+static void rcu_sync_scale_init(void)
{
}
-static struct rcu_perf_ops rcu_ops = {
+static struct rcu_scale_ops rcu_ops = {
.ptype = RCU_FLAVOR,
- .init = rcu_sync_perf_init,
- .readlock = rcu_perf_read_lock,
- .readunlock = rcu_perf_read_unlock,
+ .init = rcu_sync_scale_init,
+ .readlock = rcu_scale_read_lock,
+ .readunlock = rcu_scale_read_unlock,
.get_gp_seq = rcu_get_gp_seq,
.gp_diff = rcu_seq_diff,
.exp_completed = rcu_exp_batches_completed,
@@ -175,23 +183,23 @@ static struct rcu_perf_ops rcu_ops = {
};
/*
- * Definitions for srcu perf testing.
+ * Definitions for srcu scalability testing.
*/
-DEFINE_STATIC_SRCU(srcu_ctl_perf);
-static struct srcu_struct *srcu_ctlp = &srcu_ctl_perf;
+DEFINE_STATIC_SRCU(srcu_ctl_scale);
+static struct srcu_struct *srcu_ctlp = &srcu_ctl_scale;
-static int srcu_perf_read_lock(void) __acquires(srcu_ctlp)
+static int srcu_scale_read_lock(void) __acquires(srcu_ctlp)
{
return srcu_read_lock(srcu_ctlp);
}
-static void srcu_perf_read_unlock(int idx) __releases(srcu_ctlp)
+static void srcu_scale_read_unlock(int idx) __releases(srcu_ctlp)
{
srcu_read_unlock(srcu_ctlp, idx);
}
-static unsigned long srcu_perf_completed(void)
+static unsigned long srcu_scale_completed(void)
{
return srcu_batches_completed(srcu_ctlp);
}
@@ -206,78 +214,80 @@ static void srcu_rcu_barrier(void)
srcu_barrier(srcu_ctlp);
}
-static void srcu_perf_synchronize(void)
+static void srcu_scale_synchronize(void)
{
synchronize_srcu(srcu_ctlp);
}
-static void srcu_perf_synchronize_expedited(void)
+static void srcu_scale_synchronize_expedited(void)
{
synchronize_srcu_expedited(srcu_ctlp);
}
-static struct rcu_perf_ops srcu_ops = {
+static struct rcu_scale_ops srcu_ops = {
.ptype = SRCU_FLAVOR,
- .init = rcu_sync_perf_init,
- .readlock = srcu_perf_read_lock,
- .readunlock = srcu_perf_read_unlock,
- .get_gp_seq = srcu_perf_completed,
+ .init = rcu_sync_scale_init,
+ .readlock = srcu_scale_read_lock,
+ .readunlock = srcu_scale_read_unlock,
+ .get_gp_seq = srcu_scale_completed,
.gp_diff = rcu_seq_diff,
- .exp_completed = srcu_perf_completed,
+ .exp_completed = srcu_scale_completed,
.async = srcu_call_rcu,
.gp_barrier = srcu_rcu_barrier,
- .sync = srcu_perf_synchronize,
- .exp_sync = srcu_perf_synchronize_expedited,
+ .sync = srcu_scale_synchronize,
+ .exp_sync = srcu_scale_synchronize_expedited,
.name = "srcu"
};
static struct srcu_struct srcud;
-static void srcu_sync_perf_init(void)
+static void srcu_sync_scale_init(void)
{
srcu_ctlp = &srcud;
init_srcu_struct(srcu_ctlp);
}
-static void srcu_sync_perf_cleanup(void)
+static void srcu_sync_scale_cleanup(void)
{
cleanup_srcu_struct(srcu_ctlp);
}
-static struct rcu_perf_ops srcud_ops = {
+static struct rcu_scale_ops srcud_ops = {
.ptype = SRCU_FLAVOR,
- .init = srcu_sync_perf_init,
- .cleanup = srcu_sync_perf_cleanup,
- .readlock = srcu_perf_read_lock,
- .readunlock = srcu_perf_read_unlock,
- .get_gp_seq = srcu_perf_completed,
+ .init = srcu_sync_scale_init,
+ .cleanup = srcu_sync_scale_cleanup,
+ .readlock = srcu_scale_read_lock,
+ .readunlock = srcu_scale_read_unlock,
+ .get_gp_seq = srcu_scale_completed,
.gp_diff = rcu_seq_diff,
- .exp_completed = srcu_perf_completed,
+ .exp_completed = srcu_scale_completed,
.async = srcu_call_rcu,
.gp_barrier = srcu_rcu_barrier,
- .sync = srcu_perf_synchronize,
- .exp_sync = srcu_perf_synchronize_expedited,
+ .sync = srcu_scale_synchronize,
+ .exp_sync = srcu_scale_synchronize_expedited,
.name = "srcud"
};
+#ifdef CONFIG_TASKS_RCU
+
/*
- * Definitions for RCU-tasks perf testing.
+ * Definitions for RCU-tasks scalability testing.
*/
-static int tasks_perf_read_lock(void)
+static int tasks_scale_read_lock(void)
{
return 0;
}
-static void tasks_perf_read_unlock(int idx)
+static void tasks_scale_read_unlock(int idx)
{
}
-static struct rcu_perf_ops tasks_ops = {
+static struct rcu_scale_ops tasks_ops = {
.ptype = RCU_TASKS_FLAVOR,
- .init = rcu_sync_perf_init,
- .readlock = tasks_perf_read_lock,
- .readunlock = tasks_perf_read_unlock,
+ .init = rcu_sync_scale_init,
+ .readlock = tasks_scale_read_lock,
+ .readunlock = tasks_scale_read_unlock,
.get_gp_seq = rcu_no_completed,
.gp_diff = rcu_seq_diff,
.async = call_rcu_tasks,
@@ -287,7 +297,54 @@ static struct rcu_perf_ops tasks_ops = {
.name = "tasks"
};
-static unsigned long rcuperf_seq_diff(unsigned long new, unsigned long old)
+#define TASKS_OPS &tasks_ops,
+
+#else // #ifdef CONFIG_TASKS_RCU
+
+#define TASKS_OPS
+
+#endif // #else // #ifdef CONFIG_TASKS_RCU
+
+#ifdef CONFIG_TASKS_TRACE_RCU
+
+/*
+ * Definitions for RCU-tasks-trace scalability testing.
+ */
+
+static int tasks_trace_scale_read_lock(void)
+{
+ rcu_read_lock_trace();
+ return 0;
+}
+
+static void tasks_trace_scale_read_unlock(int idx)
+{
+ rcu_read_unlock_trace();
+}
+
+static struct rcu_scale_ops tasks_tracing_ops = {
+ .ptype = RCU_TASKS_FLAVOR,
+ .init = rcu_sync_scale_init,
+ .readlock = tasks_trace_scale_read_lock,
+ .readunlock = tasks_trace_scale_read_unlock,
+ .get_gp_seq = rcu_no_completed,
+ .gp_diff = rcu_seq_diff,
+ .async = call_rcu_tasks_trace,
+ .gp_barrier = rcu_barrier_tasks_trace,
+ .sync = synchronize_rcu_tasks_trace,
+ .exp_sync = synchronize_rcu_tasks_trace,
+ .name = "tasks-tracing"
+};
+
+#define TASKS_TRACING_OPS &tasks_tracing_ops,
+
+#else // #ifdef CONFIG_TASKS_TRACE_RCU
+
+#define TASKS_TRACING_OPS
+
+#endif // #else // #ifdef CONFIG_TASKS_TRACE_RCU
+
+static unsigned long rcuscale_seq_diff(unsigned long new, unsigned long old)
{
if (!cur_ops->gp_diff)
return new - old;
@@ -295,74 +352,75 @@ static unsigned long rcuperf_seq_diff(unsigned long new, unsigned long old)
}
/*
- * If performance tests complete, wait for shutdown to commence.
+ * If scalability tests complete, wait for shutdown to commence.
*/
-static void rcu_perf_wait_shutdown(void)
+static void rcu_scale_wait_shutdown(void)
{
cond_resched_tasks_rcu_qs();
- if (atomic_read(&n_rcu_perf_writer_finished) < nrealwriters)
+ if (atomic_read(&n_rcu_scale_writer_finished) < nrealwriters)
return;
while (!torture_must_stop())
schedule_timeout_uninterruptible(1);
}
/*
- * RCU perf reader kthread. Repeatedly does empty RCU read-side
- * critical section, minimizing update-side interference.
+ * RCU scalability reader kthread. Repeatedly does empty RCU read-side
+ * critical section, minimizing update-side interference. However, the
+ * point of this test is not to evaluate reader scalability, but instead
+ * to serve as a test load for update-side scalability testing.
*/
static int
-rcu_perf_reader(void *arg)
+rcu_scale_reader(void *arg)
{
unsigned long flags;
int idx;
long me = (long)arg;
- VERBOSE_PERFOUT_STRING("rcu_perf_reader task started");
+ VERBOSE_SCALEOUT_STRING("rcu_scale_reader task started");
set_cpus_allowed_ptr(current, cpumask_of(me % nr_cpu_ids));
set_user_nice(current, MAX_NICE);
- atomic_inc(&n_rcu_perf_reader_started);
+ atomic_inc(&n_rcu_scale_reader_started);
do {
local_irq_save(flags);
idx = cur_ops->readlock();
cur_ops->readunlock(idx);
local_irq_restore(flags);
- rcu_perf_wait_shutdown();
+ rcu_scale_wait_shutdown();
} while (!torture_must_stop());
- torture_kthread_stopping("rcu_perf_reader");
+ torture_kthread_stopping("rcu_scale_reader");
return 0;
}
/*
- * Callback function for asynchronous grace periods from rcu_perf_writer().
+ * Callback function for asynchronous grace periods from rcu_scale_writer().
*/
-static void rcu_perf_async_cb(struct rcu_head *rhp)
+static void rcu_scale_async_cb(struct rcu_head *rhp)
{
atomic_dec(this_cpu_ptr(&n_async_inflight));
kfree(rhp);
}
/*
- * RCU perf writer kthread. Repeatedly does a grace period.
+ * RCU scale writer kthread. Repeatedly does a grace period.
*/
static int
-rcu_perf_writer(void *arg)
+rcu_scale_writer(void *arg)
{
int i = 0;
int i_max;
long me = (long)arg;
struct rcu_head *rhp = NULL;
- struct sched_param sp;
bool started = false, done = false, alldone = false;
u64 t;
u64 *wdp;
u64 *wdpp = writer_durations[me];
- VERBOSE_PERFOUT_STRING("rcu_perf_writer task started");
+ VERBOSE_SCALEOUT_STRING("rcu_scale_writer task started");
WARN_ON(!wdpp);
set_cpus_allowed_ptr(current, cpumask_of(me % nr_cpu_ids));
- sp.sched_priority = 1;
- sched_setscheduler_nocheck(current, SCHED_FIFO, &sp);
+ current->flags |= PF_NO_SETAFFINITY;
+ sched_set_fifo_low(current);
if (holdoff)
schedule_timeout_uninterruptible(holdoff * HZ);
@@ -376,8 +434,8 @@ rcu_perf_writer(void *arg)
schedule_timeout_uninterruptible(1);
t = ktime_get_mono_fast_ns();
- if (atomic_inc_return(&n_rcu_perf_writer_started) >= nrealwriters) {
- t_rcu_perf_writer_started = t;
+ if (atomic_inc_return(&n_rcu_scale_writer_started) >= nrealwriters) {
+ t_rcu_scale_writer_started = t;
if (gp_exp) {
b_rcu_gp_test_started =
cur_ops->exp_completed() / 2;
@@ -397,7 +455,7 @@ retry:
rhp = kmalloc(sizeof(*rhp), GFP_KERNEL);
if (rhp && atomic_read(this_cpu_ptr(&n_async_inflight)) < gp_async_max) {
atomic_inc(this_cpu_ptr(&n_async_inflight));
- cur_ops->async(rhp, rcu_perf_async_cb);
+ cur_ops->async(rhp, rcu_scale_async_cb);
rhp = NULL;
} else if (!kthread_should_stop()) {
cur_ops->gp_barrier();
@@ -414,21 +472,19 @@ retry:
*wdp = t - *wdp;
i_max = i;
if (!started &&
- atomic_read(&n_rcu_perf_writer_started) >= nrealwriters)
+ atomic_read(&n_rcu_scale_writer_started) >= nrealwriters)
started = true;
if (!done && i >= MIN_MEAS) {
done = true;
- sp.sched_priority = 0;
- sched_setscheduler_nocheck(current,
- SCHED_NORMAL, &sp);
- pr_alert("%s%s rcu_perf_writer %ld has %d measurements\n",
- perf_type, PERF_FLAG, me, MIN_MEAS);
- if (atomic_inc_return(&n_rcu_perf_writer_finished) >=
+ sched_set_normal(current, 0);
+ pr_alert("%s%s rcu_scale_writer %ld has %d measurements\n",
+ scale_type, SCALE_FLAG, me, MIN_MEAS);
+ if (atomic_inc_return(&n_rcu_scale_writer_finished) >=
nrealwriters) {
schedule_timeout_interruptible(10);
rcu_ftrace_dump(DUMP_ALL);
- PERFOUT_STRING("Test complete");
- t_rcu_perf_writer_finished = t;
+ SCALEOUT_STRING("Test complete");
+ t_rcu_scale_writer_finished = t;
if (gp_exp) {
b_rcu_gp_test_finished =
cur_ops->exp_completed() / 2;
@@ -443,30 +499,30 @@ retry:
}
}
if (done && !alldone &&
- atomic_read(&n_rcu_perf_writer_finished) >= nrealwriters)
+ atomic_read(&n_rcu_scale_writer_finished) >= nrealwriters)
alldone = true;
if (started && !alldone && i < MAX_MEAS - 1)
i++;
- rcu_perf_wait_shutdown();
+ rcu_scale_wait_shutdown();
} while (!torture_must_stop());
if (gp_async) {
cur_ops->gp_barrier();
}
- writer_n_durations[me] = i_max;
- torture_kthread_stopping("rcu_perf_writer");
+ writer_n_durations[me] = i_max + 1;
+ torture_kthread_stopping("rcu_scale_writer");
return 0;
}
static void
-rcu_perf_print_module_parms(struct rcu_perf_ops *cur_ops, const char *tag)
+rcu_scale_print_module_parms(struct rcu_scale_ops *cur_ops, const char *tag)
{
- pr_alert("%s" PERF_FLAG
+ pr_alert("%s" SCALE_FLAG
"--- %s: nreaders=%d nwriters=%d verbose=%d shutdown=%d\n",
- perf_type, tag, nrealreaders, nrealwriters, verbose, shutdown);
+ scale_type, tag, nrealreaders, nrealwriters, verbose, shutdown);
}
static void
-rcu_perf_cleanup(void)
+rcu_scale_cleanup(void)
{
int i;
int j;
@@ -479,11 +535,11 @@ rcu_perf_cleanup(void)
* during the mid-boot phase, so have to wait till the end.
*/
if (rcu_gp_is_expedited() && !rcu_gp_is_normal() && !gp_exp)
- VERBOSE_PERFOUT_ERRSTRING("All grace periods expedited, no normal ones to measure!");
+ SCALEOUT_ERRSTRING("All grace periods expedited, no normal ones to measure!");
if (rcu_gp_is_normal() && gp_exp)
- VERBOSE_PERFOUT_ERRSTRING("All grace periods normal, no expedited ones to measure!");
+ SCALEOUT_ERRSTRING("All grace periods normal, no expedited ones to measure!");
if (gp_exp && gp_async)
- VERBOSE_PERFOUT_ERRSTRING("No expedited async GPs, so went with async!");
+ SCALEOUT_ERRSTRING("No expedited async GPs, so went with async!");
if (torture_cleanup_begin())
return;
@@ -494,30 +550,30 @@ rcu_perf_cleanup(void)
if (reader_tasks) {
for (i = 0; i < nrealreaders; i++)
- torture_stop_kthread(rcu_perf_reader,
+ torture_stop_kthread(rcu_scale_reader,
reader_tasks[i]);
kfree(reader_tasks);
}
if (writer_tasks) {
for (i = 0; i < nrealwriters; i++) {
- torture_stop_kthread(rcu_perf_writer,
+ torture_stop_kthread(rcu_scale_writer,
writer_tasks[i]);
if (!writer_n_durations)
continue;
j = writer_n_durations[i];
pr_alert("%s%s writer %d gps: %d\n",
- perf_type, PERF_FLAG, i, j);
+ scale_type, SCALE_FLAG, i, j);
ngps += j;
}
pr_alert("%s%s start: %llu end: %llu duration: %llu gps: %d batches: %ld\n",
- perf_type, PERF_FLAG,
- t_rcu_perf_writer_started, t_rcu_perf_writer_finished,
- t_rcu_perf_writer_finished -
- t_rcu_perf_writer_started,
+ scale_type, SCALE_FLAG,
+ t_rcu_scale_writer_started, t_rcu_scale_writer_finished,
+ t_rcu_scale_writer_finished -
+ t_rcu_scale_writer_started,
ngps,
- rcuperf_seq_diff(b_rcu_gp_test_finished,
- b_rcu_gp_test_started));
+ rcuscale_seq_diff(b_rcu_gp_test_finished,
+ b_rcu_gp_test_started));
for (i = 0; i < nrealwriters; i++) {
if (!writer_durations)
break;
@@ -526,10 +582,10 @@ rcu_perf_cleanup(void)
wdpp = writer_durations[i];
if (!wdpp)
continue;
- for (j = 0; j <= writer_n_durations[i]; j++) {
+ for (j = 0; j < writer_n_durations[i]; j++) {
wdp = &wdpp[j];
pr_alert("%s%s %4d writer-duration: %5d %llu\n",
- perf_type, PERF_FLAG,
+ scale_type, SCALE_FLAG,
i, j, *wdp);
if (j % 100 == 0)
schedule_timeout_uninterruptible(1);
@@ -568,36 +624,35 @@ static int compute_real(int n)
}
/*
- * RCU perf shutdown kthread. Just waits to be awakened, then shuts
+ * RCU scalability shutdown kthread. Just waits to be awakened, then shuts
* down system.
*/
static int
-rcu_perf_shutdown(void *arg)
+rcu_scale_shutdown(void *arg)
{
- do {
- wait_event(shutdown_wq,
- atomic_read(&n_rcu_perf_writer_finished) >=
- nrealwriters);
- } while (atomic_read(&n_rcu_perf_writer_finished) < nrealwriters);
+ wait_event(shutdown_wq,
+ atomic_read(&n_rcu_scale_writer_finished) >= nrealwriters);
smp_mb(); /* Wake before output. */
- rcu_perf_cleanup();
+ rcu_scale_cleanup();
kernel_power_off();
return -EINVAL;
}
/*
- * kfree_rcu() performance tests: Start a kfree_rcu() loop on all CPUs for number
+ * kfree_rcu() scalability tests: Start a kfree_rcu() loop on all CPUs for number
* of iterations and measure total time and number of GP for all iterations to complete.
*/
torture_param(int, kfree_nthreads, -1, "Number of threads running loops of kfree_rcu().");
torture_param(int, kfree_alloc_num, 8000, "Number of allocations and frees done in an iteration.");
torture_param(int, kfree_loops, 10, "Number of loops doing kfree_alloc_num allocations and frees.");
+torture_param(bool, kfree_rcu_test_double, false, "Do we run a kfree_rcu() double-argument scale test?");
+torture_param(bool, kfree_rcu_test_single, false, "Do we run a kfree_rcu() single-argument scale test?");
static struct task_struct **kfree_reader_tasks;
static int kfree_nrealthreads;
-static atomic_t n_kfree_perf_thread_started;
-static atomic_t n_kfree_perf_thread_ended;
+static atomic_t n_kfree_scale_thread_started;
+static atomic_t n_kfree_scale_thread_ended;
struct kfree_obj {
char kfree_obj[8];
@@ -605,20 +660,24 @@ struct kfree_obj {
};
static int
-kfree_perf_thread(void *arg)
+kfree_scale_thread(void *arg)
{
int i, loop = 0;
long me = (long)arg;
struct kfree_obj *alloc_ptr;
u64 start_time, end_time;
+ long long mem_begin, mem_during = 0;
+ bool kfree_rcu_test_both;
+ DEFINE_TORTURE_RANDOM(tr);
- VERBOSE_PERFOUT_STRING("kfree_perf_thread task started");
+ VERBOSE_SCALEOUT_STRING("kfree_scale_thread task started");
set_cpus_allowed_ptr(current, cpumask_of(me % nr_cpu_ids));
set_user_nice(current, MAX_NICE);
+ kfree_rcu_test_both = (kfree_rcu_test_single == kfree_rcu_test_double);
start_time = ktime_get_mono_fast_ns();
- if (atomic_inc_return(&n_kfree_perf_thread_started) >= kfree_nrealthreads) {
+ if (atomic_inc_return(&n_kfree_scale_thread_started) >= kfree_nrealthreads) {
if (gp_exp)
b_rcu_gp_test_started = cur_ops->exp_completed() / 2;
else
@@ -626,18 +685,32 @@ kfree_perf_thread(void *arg)
}
do {
+ if (!mem_during) {
+ mem_during = mem_begin = si_mem_available();
+ } else if (loop % (kfree_loops / 4) == 0) {
+ mem_during = (mem_during + si_mem_available()) / 2;
+ }
+
for (i = 0; i < kfree_alloc_num; i++) {
- alloc_ptr = kmalloc(sizeof(struct kfree_obj), GFP_KERNEL);
+ alloc_ptr = kmalloc(kfree_mult * sizeof(struct kfree_obj), GFP_KERNEL);
if (!alloc_ptr)
return -ENOMEM;
- kfree_rcu(alloc_ptr, rh);
+ // By default kfree_rcu_test_single and kfree_rcu_test_double are
+ // initialized to false. If both have the same value (false or true)
+ // both are randomly tested, otherwise only the one with value true
+ // is tested.
+ if ((kfree_rcu_test_single && !kfree_rcu_test_double) ||
+ (kfree_rcu_test_both && torture_random(&tr) & 0x800))
+ kfree_rcu(alloc_ptr);
+ else
+ kfree_rcu(alloc_ptr, rh);
}
cond_resched();
} while (!torture_must_stop() && ++loop < kfree_loops);
- if (atomic_inc_return(&n_kfree_perf_thread_ended) >= kfree_nrealthreads) {
+ if (atomic_inc_return(&n_kfree_scale_thread_ended) >= kfree_nrealthreads) {
end_time = ktime_get_mono_fast_ns();
if (gp_exp)
@@ -645,21 +718,23 @@ kfree_perf_thread(void *arg)
else
b_rcu_gp_test_finished = cur_ops->get_gp_seq();
- pr_alert("Total time taken by all kfree'ers: %llu ns, loops: %d, batches: %ld\n",
+ pr_alert("Total time taken by all kfree'ers: %llu ns, loops: %d, batches: %ld, memory footprint: %lldMB\n",
(unsigned long long)(end_time - start_time), kfree_loops,
- rcuperf_seq_diff(b_rcu_gp_test_finished, b_rcu_gp_test_started));
+ rcuscale_seq_diff(b_rcu_gp_test_finished, b_rcu_gp_test_started),
+ (mem_begin - mem_during) >> (20 - PAGE_SHIFT));
+
if (shutdown) {
smp_mb(); /* Assign before wake. */
wake_up(&shutdown_wq);
}
}
- torture_kthread_stopping("kfree_perf_thread");
+ torture_kthread_stopping("kfree_scale_thread");
return 0;
}
static void
-kfree_perf_cleanup(void)
+kfree_scale_cleanup(void)
{
int i;
@@ -668,7 +743,7 @@ kfree_perf_cleanup(void)
if (kfree_reader_tasks) {
for (i = 0; i < kfree_nrealthreads; i++)
- torture_stop_kthread(kfree_perf_thread,
+ torture_stop_kthread(kfree_scale_thread,
kfree_reader_tasks[i]);
kfree(kfree_reader_tasks);
}
@@ -680,23 +755,20 @@ kfree_perf_cleanup(void)
* shutdown kthread. Just waits to be awakened, then shuts down system.
*/
static int
-kfree_perf_shutdown(void *arg)
+kfree_scale_shutdown(void *arg)
{
- do {
- wait_event(shutdown_wq,
- atomic_read(&n_kfree_perf_thread_ended) >=
- kfree_nrealthreads);
- } while (atomic_read(&n_kfree_perf_thread_ended) < kfree_nrealthreads);
+ wait_event(shutdown_wq,
+ atomic_read(&n_kfree_scale_thread_ended) >= kfree_nrealthreads);
smp_mb(); /* Wake before output. */
- kfree_perf_cleanup();
+ kfree_scale_cleanup();
kernel_power_off();
return -EINVAL;
}
static int __init
-kfree_perf_init(void)
+kfree_scale_init(void)
{
long i;
int firsterr = 0;
@@ -705,13 +777,15 @@ kfree_perf_init(void)
/* Start up the kthreads. */
if (shutdown) {
init_waitqueue_head(&shutdown_wq);
- firsterr = torture_create_kthread(kfree_perf_shutdown, NULL,
+ firsterr = torture_create_kthread(kfree_scale_shutdown, NULL,
shutdown_task);
- if (firsterr)
+ if (torture_init_error(firsterr))
goto unwind;
schedule_timeout_uninterruptible(1);
}
+ pr_alert("kfree object size=%zu\n", kfree_mult * sizeof(struct kfree_obj));
+
kfree_reader_tasks = kcalloc(kfree_nrealthreads, sizeof(kfree_reader_tasks[0]),
GFP_KERNEL);
if (kfree_reader_tasks == NULL) {
@@ -720,13 +794,13 @@ kfree_perf_init(void)
}
for (i = 0; i < kfree_nrealthreads; i++) {
- firsterr = torture_create_kthread(kfree_perf_thread, (void *)i,
+ firsterr = torture_create_kthread(kfree_scale_thread, (void *)i,
kfree_reader_tasks[i]);
- if (firsterr)
+ if (torture_init_error(firsterr))
goto unwind;
}
- while (atomic_read(&n_kfree_perf_thread_started) < kfree_nrealthreads)
+ while (atomic_read(&n_kfree_scale_thread_started) < kfree_nrealthreads)
schedule_timeout_uninterruptible(1);
torture_init_end();
@@ -734,35 +808,34 @@ kfree_perf_init(void)
unwind:
torture_init_end();
- kfree_perf_cleanup();
+ kfree_scale_cleanup();
return firsterr;
}
static int __init
-rcu_perf_init(void)
+rcu_scale_init(void)
{
long i;
int firsterr = 0;
- static struct rcu_perf_ops *perf_ops[] = {
- &rcu_ops, &srcu_ops, &srcud_ops, &tasks_ops,
+ static struct rcu_scale_ops *scale_ops[] = {
+ &rcu_ops, &srcu_ops, &srcud_ops, TASKS_OPS TASKS_TRACING_OPS
};
- if (!torture_init_begin(perf_type, verbose))
+ if (!torture_init_begin(scale_type, verbose))
return -EBUSY;
- /* Process args and tell the world that the perf'er is on the job. */
- for (i = 0; i < ARRAY_SIZE(perf_ops); i++) {
- cur_ops = perf_ops[i];
- if (strcmp(perf_type, cur_ops->name) == 0)
+ /* Process args and announce that the scalability'er is on the job. */
+ for (i = 0; i < ARRAY_SIZE(scale_ops); i++) {
+ cur_ops = scale_ops[i];
+ if (strcmp(scale_type, cur_ops->name) == 0)
break;
}
- if (i == ARRAY_SIZE(perf_ops)) {
- pr_alert("rcu-perf: invalid perf type: \"%s\"\n", perf_type);
- pr_alert("rcu-perf types:");
- for (i = 0; i < ARRAY_SIZE(perf_ops); i++)
- pr_cont(" %s", perf_ops[i]->name);
+ if (i == ARRAY_SIZE(scale_ops)) {
+ pr_alert("rcu-scale: invalid scale type: \"%s\"\n", scale_type);
+ pr_alert("rcu-scale types:");
+ for (i = 0; i < ARRAY_SIZE(scale_ops); i++)
+ pr_cont(" %s", scale_ops[i]->name);
pr_cont("\n");
- WARN_ON(!IS_MODULE(CONFIG_RCU_PERF_TEST));
firsterr = -EINVAL;
cur_ops = NULL;
goto unwind;
@@ -771,39 +844,39 @@ rcu_perf_init(void)
cur_ops->init();
if (kfree_rcu_test)
- return kfree_perf_init();
+ return kfree_scale_init();
nrealwriters = compute_real(nwriters);
nrealreaders = compute_real(nreaders);
- atomic_set(&n_rcu_perf_reader_started, 0);
- atomic_set(&n_rcu_perf_writer_started, 0);
- atomic_set(&n_rcu_perf_writer_finished, 0);
- rcu_perf_print_module_parms(cur_ops, "Start of test");
+ atomic_set(&n_rcu_scale_reader_started, 0);
+ atomic_set(&n_rcu_scale_writer_started, 0);
+ atomic_set(&n_rcu_scale_writer_finished, 0);
+ rcu_scale_print_module_parms(cur_ops, "Start of test");
/* Start up the kthreads. */
if (shutdown) {
init_waitqueue_head(&shutdown_wq);
- firsterr = torture_create_kthread(rcu_perf_shutdown, NULL,
+ firsterr = torture_create_kthread(rcu_scale_shutdown, NULL,
shutdown_task);
- if (firsterr)
+ if (torture_init_error(firsterr))
goto unwind;
schedule_timeout_uninterruptible(1);
}
reader_tasks = kcalloc(nrealreaders, sizeof(reader_tasks[0]),
GFP_KERNEL);
if (reader_tasks == NULL) {
- VERBOSE_PERFOUT_ERRSTRING("out of memory");
+ SCALEOUT_ERRSTRING("out of memory");
firsterr = -ENOMEM;
goto unwind;
}
for (i = 0; i < nrealreaders; i++) {
- firsterr = torture_create_kthread(rcu_perf_reader, (void *)i,
+ firsterr = torture_create_kthread(rcu_scale_reader, (void *)i,
reader_tasks[i]);
- if (firsterr)
+ if (torture_init_error(firsterr))
goto unwind;
}
- while (atomic_read(&n_rcu_perf_reader_started) < nrealreaders)
+ while (atomic_read(&n_rcu_scale_reader_started) < nrealreaders)
schedule_timeout_uninterruptible(1);
writer_tasks = kcalloc(nrealwriters, sizeof(reader_tasks[0]),
GFP_KERNEL);
@@ -813,7 +886,7 @@ rcu_perf_init(void)
kcalloc(nrealwriters, sizeof(*writer_n_durations),
GFP_KERNEL);
if (!writer_tasks || !writer_durations || !writer_n_durations) {
- VERBOSE_PERFOUT_ERRSTRING("out of memory");
+ SCALEOUT_ERRSTRING("out of memory");
firsterr = -ENOMEM;
goto unwind;
}
@@ -825,9 +898,9 @@ rcu_perf_init(void)
firsterr = -ENOMEM;
goto unwind;
}
- firsterr = torture_create_kthread(rcu_perf_writer, (void *)i,
+ firsterr = torture_create_kthread(rcu_scale_writer, (void *)i,
writer_tasks[i]);
- if (firsterr)
+ if (torture_init_error(firsterr))
goto unwind;
}
torture_init_end();
@@ -835,9 +908,13 @@ rcu_perf_init(void)
unwind:
torture_init_end();
- rcu_perf_cleanup();
+ rcu_scale_cleanup();
+ if (shutdown) {
+ WARN_ON(!IS_MODULE(CONFIG_RCU_SCALE_TEST));
+ kernel_power_off();
+ }
return firsterr;
}
-module_init(rcu_perf_init);
-module_exit(rcu_perf_cleanup);
+module_init(rcu_scale_init);
+module_exit(rcu_scale_cleanup);
diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 1aeecc165b21..503c2aa845a4 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -7,7 +7,7 @@
* Authors: Paul E. McKenney <paulmck@linux.ibm.com>
* Josh Triplett <josh@joshtriplett.org>
*
- * See also: Documentation/RCU/torture.txt
+ * See also: Documentation/RCU/torture.rst
*/
#define pr_fmt(fmt) fmt
@@ -20,7 +20,7 @@
#include <linux/err.h>
#include <linux/spinlock.h>
#include <linux/smp.h>
-#include <linux/rcupdate.h>
+#include <linux/rcupdate_wait.h>
#include <linux/interrupt.h>
#include <linux/sched/signal.h>
#include <uapi/linux/sched/types.h>
@@ -45,23 +45,27 @@
#include <linux/sched/sysctl.h>
#include <linux/oom.h>
#include <linux/tick.h>
+#include <linux/rcupdate_trace.h>
+#include <linux/nmi.h>
#include "rcu.h"
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Paul E. McKenney <paulmck@linux.ibm.com> and Josh Triplett <josh@joshtriplett.org>");
-
/* Bits for ->extendables field, extendables param, and related definitions. */
-#define RCUTORTURE_RDR_SHIFT 8 /* Put SRCU index in upper bits. */
-#define RCUTORTURE_RDR_MASK ((1 << RCUTORTURE_RDR_SHIFT) - 1)
+#define RCUTORTURE_RDR_SHIFT_1 8 /* Put SRCU index in upper bits. */
+#define RCUTORTURE_RDR_MASK_1 (1 << RCUTORTURE_RDR_SHIFT_1)
+#define RCUTORTURE_RDR_SHIFT_2 9 /* Put SRCU index in upper bits. */
+#define RCUTORTURE_RDR_MASK_2 (1 << RCUTORTURE_RDR_SHIFT_2)
#define RCUTORTURE_RDR_BH 0x01 /* Extend readers by disabling bh. */
#define RCUTORTURE_RDR_IRQ 0x02 /* ... disabling interrupts. */
#define RCUTORTURE_RDR_PREEMPT 0x04 /* ... disabling preemption. */
#define RCUTORTURE_RDR_RBH 0x08 /* ... rcu_read_lock_bh(). */
#define RCUTORTURE_RDR_SCHED 0x10 /* ... rcu_read_lock_sched(). */
-#define RCUTORTURE_RDR_RCU 0x20 /* ... entering another RCU reader. */
-#define RCUTORTURE_RDR_NBITS 6 /* Number of bits defined above. */
+#define RCUTORTURE_RDR_RCU_1 0x20 /* ... entering another RCU reader. */
+#define RCUTORTURE_RDR_RCU_2 0x40 /* ... entering another RCU reader. */
+#define RCUTORTURE_RDR_NBITS 7 /* Number of bits defined above. */
#define RCUTORTURE_MAX_EXTEND \
(RCUTORTURE_RDR_BH | RCUTORTURE_RDR_IRQ | RCUTORTURE_RDR_PREEMPT | \
RCUTORTURE_RDR_RBH | RCUTORTURE_RDR_SCHED)
@@ -71,73 +75,90 @@ MODULE_AUTHOR("Paul E. McKenney <paulmck@linux.ibm.com> and Josh Triplett <josh@
torture_param(int, extendables, RCUTORTURE_MAX_EXTEND,
"Extend readers by disabling bh (1), irqs (2), or preempt (4)");
-torture_param(int, fqs_duration, 0,
- "Duration of fqs bursts (us), 0 to disable");
+torture_param(int, fqs_duration, 0, "Duration of fqs bursts (us), 0 to disable");
torture_param(int, fqs_holdoff, 0, "Holdoff time within fqs bursts (us)");
torture_param(int, fqs_stutter, 3, "Wait time between fqs bursts (s)");
-torture_param(bool, fwd_progress, 1, "Test grace-period forward progress");
+torture_param(int, fwd_progress, 1, "Number of grace-period forward progress tasks (0 to disable)");
torture_param(int, fwd_progress_div, 4, "Fraction of CPU stall to wait");
-torture_param(int, fwd_progress_holdoff, 60,
- "Time between forward-progress tests (s)");
-torture_param(bool, fwd_progress_need_resched, 1,
- "Hide cond_resched() behind need_resched()");
+torture_param(int, fwd_progress_holdoff, 60, "Time between forward-progress tests (s)");
+torture_param(bool, fwd_progress_need_resched, 1, "Hide cond_resched() behind need_resched()");
torture_param(bool, gp_cond, false, "Use conditional/async GP wait primitives");
+torture_param(bool, gp_cond_exp, false, "Use conditional/async expedited GP wait primitives");
+torture_param(bool, gp_cond_full, false, "Use conditional/async full-state GP wait primitives");
+torture_param(bool, gp_cond_exp_full, false,
+ "Use conditional/async full-stateexpedited GP wait primitives");
torture_param(bool, gp_exp, false, "Use expedited GP wait primitives");
-torture_param(bool, gp_normal, false,
- "Use normal (non-expedited) GP wait primitives");
+torture_param(bool, gp_normal, false, "Use normal (non-expedited) GP wait primitives");
+torture_param(bool, gp_poll, false, "Use polling GP wait primitives");
+torture_param(bool, gp_poll_exp, false, "Use polling expedited GP wait primitives");
+torture_param(bool, gp_poll_full, false, "Use polling full-state GP wait primitives");
+torture_param(bool, gp_poll_exp_full, false, "Use polling full-state expedited GP wait primitives");
torture_param(bool, gp_sync, false, "Use synchronous GP wait primitives");
torture_param(int, irqreader, 1, "Allow RCU readers from irq handlers");
-torture_param(int, n_barrier_cbs, 0,
- "# of callbacks/kthreads for barrier testing");
+torture_param(int, leakpointer, 0, "Leak pointer dereferences from readers");
+torture_param(int, n_barrier_cbs, 0, "# of callbacks/kthreads for barrier testing");
torture_param(int, nfakewriters, 4, "Number of RCU fake writer threads");
torture_param(int, nreaders, -1, "Number of RCU reader threads");
-torture_param(int, object_debug, 0,
- "Enable debug-object double call_rcu() testing");
+torture_param(int, object_debug, 0, "Enable debug-object double call_rcu() testing");
torture_param(int, onoff_holdoff, 0, "Time after boot before CPU hotplugs (s)");
-torture_param(int, onoff_interval, 0,
- "Time between CPU hotplugs (jiffies), 0=disable");
+torture_param(int, onoff_interval, 0, "Time between CPU hotplugs (jiffies), 0=disable");
+torture_param(int, nocbs_nthreads, 0, "Number of NOCB toggle threads, 0 to disable");
+torture_param(int, nocbs_toggle, 1000, "Time between toggling nocb state (ms)");
+torture_param(int, read_exit_delay, 13, "Delay between read-then-exit episodes (s)");
+torture_param(int, read_exit_burst, 16, "# of read-then-exit bursts per episode, zero to disable");
torture_param(int, shuffle_interval, 3, "Number of seconds between shuffles");
torture_param(int, shutdown_secs, 0, "Shutdown time (s), <= zero to disable.");
torture_param(int, stall_cpu, 0, "Stall duration (s), zero to disable.");
-torture_param(int, stall_cpu_holdoff, 10,
- "Time to wait before starting stall (s).");
+torture_param(int, stall_cpu_holdoff, 10, "Time to wait before starting stall (s).");
+torture_param(bool, stall_no_softlockup, false, "Avoid softlockup warning during cpu stall.");
torture_param(int, stall_cpu_irqsoff, 0, "Disable interrupts while stalling.");
-torture_param(int, stat_interval, 60,
- "Number of seconds between stats printk()s");
+torture_param(int, stall_cpu_block, 0, "Sleep while stalling.");
+torture_param(int, stall_gp_kthread, 0, "Grace-period kthread stall duration (s).");
+torture_param(int, stat_interval, 60, "Number of seconds between stats printk()s");
torture_param(int, stutter, 5, "Number of seconds to run/halt test");
torture_param(int, test_boost, 1, "Test RCU prio boost: 0=no, 1=maybe, 2=yes.");
-torture_param(int, test_boost_duration, 4,
- "Duration of each boost test, seconds.");
-torture_param(int, test_boost_interval, 7,
- "Interval between boost tests, seconds.");
-torture_param(bool, test_no_idle_hz, true,
- "Test support for tickless idle CPUs");
-torture_param(int, verbose, 1,
- "Enable verbose debugging printk()s");
+torture_param(int, test_boost_duration, 4, "Duration of each boost test, seconds.");
+torture_param(int, test_boost_interval, 7, "Interval between boost tests, seconds.");
+torture_param(bool, test_no_idle_hz, true, "Test support for tickless idle CPUs");
+torture_param(int, verbose, 1, "Enable verbose debugging printk()s");
static char *torture_type = "rcu";
module_param(torture_type, charp, 0444);
MODULE_PARM_DESC(torture_type, "Type of RCU to torture (rcu, srcu, ...)");
+static int nrealnocbers;
static int nrealreaders;
static struct task_struct *writer_task;
static struct task_struct **fakewriter_tasks;
static struct task_struct **reader_tasks;
+static struct task_struct **nocb_tasks;
static struct task_struct *stats_task;
static struct task_struct *fqs_task;
static struct task_struct *boost_tasks[NR_CPUS];
static struct task_struct *stall_task;
-static struct task_struct *fwd_prog_task;
+static struct task_struct **fwd_prog_tasks;
static struct task_struct **barrier_cbs_tasks;
static struct task_struct *barrier_task;
+static struct task_struct *read_exit_task;
#define RCU_TORTURE_PIPE_LEN 10
+// Mailbox-like structure to check RCU global memory ordering.
+struct rcu_torture_reader_check {
+ unsigned long rtc_myloops;
+ int rtc_chkrdr;
+ unsigned long rtc_chkloops;
+ int rtc_ready;
+ struct rcu_torture_reader_check *rtc_assigner;
+} ____cacheline_internodealigned_in_smp;
+
+// Update-side data structure used to check RCU readers.
struct rcu_torture {
struct rcu_head rtort_rcu;
int rtort_pipe_count;
struct list_head rtort_free;
int rtort_mbtest;
+ struct rcu_torture_reader_check *rtort_chkp;
};
static LIST_HEAD(rcu_torture_freelist);
@@ -148,10 +169,13 @@ static DEFINE_SPINLOCK(rcu_torture_lock);
static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_count);
static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_batch);
static atomic_t rcu_torture_wcount[RCU_TORTURE_PIPE_LEN + 1];
+static struct rcu_torture_reader_check *rcu_torture_reader_mbchk;
static atomic_t n_rcu_torture_alloc;
static atomic_t n_rcu_torture_alloc_fail;
static atomic_t n_rcu_torture_free;
static atomic_t n_rcu_torture_mberror;
+static atomic_t n_rcu_torture_mbchk_fail;
+static atomic_t n_rcu_torture_mbchk_tries;
static atomic_t n_rcu_torture_error;
static long n_rcu_torture_barrier_error;
static long n_rcu_torture_boost_ktrerror;
@@ -161,8 +185,12 @@ static long n_rcu_torture_boosts;
static atomic_long_t n_rcu_torture_timers;
static long n_barrier_attempts;
static long n_barrier_successes; /* did rcu_barrier test succeed? */
+static unsigned long n_read_exits;
static struct list_head rcu_torture_removed;
static unsigned long shutdown_jiffies;
+static unsigned long start_gp_seq;
+static atomic_long_t n_nocb_offload;
+static atomic_long_t n_nocb_deoffload;
static int rcu_torture_writer_state;
#define RTWS_FIXED_DELAY 0
@@ -171,10 +199,24 @@ static int rcu_torture_writer_state;
#define RTWS_DEF_FREE 3
#define RTWS_EXP_SYNC 4
#define RTWS_COND_GET 5
-#define RTWS_COND_SYNC 6
-#define RTWS_SYNC 7
-#define RTWS_STUTTER 8
-#define RTWS_STOPPING 9
+#define RTWS_COND_GET_FULL 6
+#define RTWS_COND_GET_EXP 7
+#define RTWS_COND_GET_EXP_FULL 8
+#define RTWS_COND_SYNC 9
+#define RTWS_COND_SYNC_FULL 10
+#define RTWS_COND_SYNC_EXP 11
+#define RTWS_COND_SYNC_EXP_FULL 12
+#define RTWS_POLL_GET 13
+#define RTWS_POLL_GET_FULL 14
+#define RTWS_POLL_GET_EXP 15
+#define RTWS_POLL_GET_EXP_FULL 16
+#define RTWS_POLL_WAIT 17
+#define RTWS_POLL_WAIT_FULL 18
+#define RTWS_POLL_WAIT_EXP 19
+#define RTWS_POLL_WAIT_EXP_FULL 20
+#define RTWS_SYNC 21
+#define RTWS_STUTTER 22
+#define RTWS_STOPPING 23
static const char * const rcu_torture_writer_state_names[] = {
"RTWS_FIXED_DELAY",
"RTWS_DELAY",
@@ -182,7 +224,21 @@ static const char * const rcu_torture_writer_state_names[] = {
"RTWS_DEF_FREE",
"RTWS_EXP_SYNC",
"RTWS_COND_GET",
+ "RTWS_COND_GET_FULL",
+ "RTWS_COND_GET_EXP",
+ "RTWS_COND_GET_EXP_FULL",
"RTWS_COND_SYNC",
+ "RTWS_COND_SYNC_FULL",
+ "RTWS_COND_SYNC_EXP",
+ "RTWS_COND_SYNC_EXP_FULL",
+ "RTWS_POLL_GET",
+ "RTWS_POLL_GET_FULL",
+ "RTWS_POLL_GET_EXP",
+ "RTWS_POLL_GET_EXP_FULL",
+ "RTWS_POLL_WAIT",
+ "RTWS_POLL_WAIT_FULL",
+ "RTWS_POLL_WAIT_EXP",
+ "RTWS_POLL_WAIT_EXP_FULL",
"RTWS_SYNC",
"RTWS_STUTTER",
"RTWS_STOPPING",
@@ -209,12 +265,6 @@ static const char *rcu_torture_writer_state_getname(void)
return rcu_torture_writer_state_names[i];
}
-#if defined(CONFIG_RCU_BOOST) && !defined(CONFIG_HOTPLUG_CPU)
-#define rcu_can_boost() 1
-#else /* #if defined(CONFIG_RCU_BOOST) && !defined(CONFIG_HOTPLUG_CPU) */
-#define rcu_can_boost() 0
-#endif /* #else #if defined(CONFIG_RCU_BOOST) && !defined(CONFIG_HOTPLUG_CPU) */
-
#ifdef CONFIG_RCU_TRACE
static u64 notrace rcu_trace_clock_local(void)
{
@@ -248,7 +298,7 @@ static atomic_t barrier_cbs_invoked; /* Barrier callbacks invoked. */
static wait_queue_head_t *barrier_cbs_wq; /* Coordinate barrier testing. */
static DECLARE_WAIT_QUEUE_HEAD(barrier_wq);
-static bool rcu_fwd_cb_nodelay; /* Short rcu_torture_delay() delays. */
+static atomic_t rcu_fwd_cb_nodelay; /* Short rcu_torture_delay() delays. */
/*
* Allocate an element from the rcu_tortures pool.
@@ -295,22 +345,42 @@ struct rcu_torture_ops {
void (*read_delay)(struct torture_random_state *rrsp,
struct rt_read_seg *rtrsp);
void (*readunlock)(int idx);
+ int (*readlock_held)(void);
unsigned long (*get_gp_seq)(void);
unsigned long (*gp_diff)(unsigned long new, unsigned long old);
void (*deferred_free)(struct rcu_torture *p);
void (*sync)(void);
void (*exp_sync)(void);
- unsigned long (*get_state)(void);
+ unsigned long (*get_gp_state_exp)(void);
+ unsigned long (*start_gp_poll_exp)(void);
+ void (*start_gp_poll_exp_full)(struct rcu_gp_oldstate *rgosp);
+ bool (*poll_gp_state_exp)(unsigned long oldstate);
+ void (*cond_sync_exp)(unsigned long oldstate);
+ void (*cond_sync_exp_full)(struct rcu_gp_oldstate *rgosp);
+ unsigned long (*get_gp_state)(void);
+ void (*get_gp_state_full)(struct rcu_gp_oldstate *rgosp);
+ unsigned long (*get_gp_completed)(void);
+ void (*get_gp_completed_full)(struct rcu_gp_oldstate *rgosp);
+ unsigned long (*start_gp_poll)(void);
+ void (*start_gp_poll_full)(struct rcu_gp_oldstate *rgosp);
+ bool (*poll_gp_state)(unsigned long oldstate);
+ bool (*poll_gp_state_full)(struct rcu_gp_oldstate *rgosp);
+ bool (*poll_need_2gp)(bool poll, bool poll_full);
void (*cond_sync)(unsigned long oldstate);
+ void (*cond_sync_full)(struct rcu_gp_oldstate *rgosp);
call_rcu_func_t call;
void (*cb_barrier)(void);
void (*fqs)(void);
void (*stats)(void);
+ void (*gp_kthread_dbg)(void);
+ bool (*check_boost_failed)(unsigned long gp_state, int *cpup);
int (*stall_dur)(void);
+ long cbflood_max;
int irq_capable;
int can_boost;
int extendables;
int slow_gps;
+ int no_pi_lock;
const char *name;
};
@@ -320,6 +390,11 @@ static struct rcu_torture_ops *cur_ops;
* Definitions for rcu torture testing.
*/
+static int torture_readlock_not_held(void)
+{
+ return rcu_read_lock_bh_held() || rcu_read_lock_sched_held();
+}
+
static int rcu_torture_read_lock(void) __acquires(RCU)
{
rcu_read_lock();
@@ -339,7 +414,7 @@ rcu_read_delay(struct torture_random_state *rrsp, struct rt_read_seg *rtrsp)
* period, and we want a long delay occasionally to trigger
* force_quiescent_state. */
- if (!rcu_fwd_cb_nodelay &&
+ if (!atomic_read(&rcu_fwd_cb_nodelay) &&
!(torture_random(rrsp) % (nrealreaders * 2000 * longdelay_ms))) {
started = cur_ops->get_gp_seq();
ts = rcu_trace_clock_local();
@@ -374,12 +449,18 @@ static bool
rcu_torture_pipe_update_one(struct rcu_torture *rp)
{
int i;
+ struct rcu_torture_reader_check *rtrcp = READ_ONCE(rp->rtort_chkp);
- i = rp->rtort_pipe_count;
+ if (rtrcp) {
+ WRITE_ONCE(rp->rtort_chkp, NULL);
+ smp_store_release(&rtrcp->rtc_ready, 1); // Pair with smp_load_acquire().
+ }
+ i = READ_ONCE(rp->rtort_pipe_count);
if (i > RCU_TORTURE_PIPE_LEN)
i = RCU_TORTURE_PIPE_LEN;
atomic_inc(&rcu_torture_wcount[i]);
- if (++rp->rtort_pipe_count >= RCU_TORTURE_PIPE_LEN) {
+ WRITE_ONCE(rp->rtort_pipe_count, i + 1);
+ if (rp->rtort_pipe_count >= RCU_TORTURE_PIPE_LEN) {
rp->rtort_mbtest = 0;
return true;
}
@@ -437,28 +518,50 @@ static void rcu_sync_torture_init(void)
INIT_LIST_HEAD(&rcu_torture_removed);
}
+static bool rcu_poll_need_2gp(bool poll, bool poll_full)
+{
+ return poll;
+}
+
static struct rcu_torture_ops rcu_ops = {
- .ttype = RCU_FLAVOR,
- .init = rcu_sync_torture_init,
- .readlock = rcu_torture_read_lock,
- .read_delay = rcu_read_delay,
- .readunlock = rcu_torture_read_unlock,
- .get_gp_seq = rcu_get_gp_seq,
- .gp_diff = rcu_seq_diff,
- .deferred_free = rcu_torture_deferred_free,
- .sync = synchronize_rcu,
- .exp_sync = synchronize_rcu_expedited,
- .get_state = get_state_synchronize_rcu,
- .cond_sync = cond_synchronize_rcu,
- .call = call_rcu,
- .cb_barrier = rcu_barrier,
- .fqs = rcu_force_quiescent_state,
- .stats = NULL,
- .stall_dur = rcu_jiffies_till_stall_check,
- .irq_capable = 1,
- .can_boost = rcu_can_boost(),
- .extendables = RCUTORTURE_MAX_EXTEND,
- .name = "rcu"
+ .ttype = RCU_FLAVOR,
+ .init = rcu_sync_torture_init,
+ .readlock = rcu_torture_read_lock,
+ .read_delay = rcu_read_delay,
+ .readunlock = rcu_torture_read_unlock,
+ .readlock_held = torture_readlock_not_held,
+ .get_gp_seq = rcu_get_gp_seq,
+ .gp_diff = rcu_seq_diff,
+ .deferred_free = rcu_torture_deferred_free,
+ .sync = synchronize_rcu,
+ .exp_sync = synchronize_rcu_expedited,
+ .get_gp_state = get_state_synchronize_rcu,
+ .get_gp_state_full = get_state_synchronize_rcu_full,
+ .get_gp_completed = get_completed_synchronize_rcu,
+ .get_gp_completed_full = get_completed_synchronize_rcu_full,
+ .start_gp_poll = start_poll_synchronize_rcu,
+ .start_gp_poll_full = start_poll_synchronize_rcu_full,
+ .poll_gp_state = poll_state_synchronize_rcu,
+ .poll_gp_state_full = poll_state_synchronize_rcu_full,
+ .poll_need_2gp = rcu_poll_need_2gp,
+ .cond_sync = cond_synchronize_rcu,
+ .cond_sync_full = cond_synchronize_rcu_full,
+ .get_gp_state_exp = get_state_synchronize_rcu,
+ .start_gp_poll_exp = start_poll_synchronize_rcu_expedited,
+ .start_gp_poll_exp_full = start_poll_synchronize_rcu_expedited_full,
+ .poll_gp_state_exp = poll_state_synchronize_rcu,
+ .cond_sync_exp = cond_synchronize_rcu_expedited,
+ .call = call_rcu,
+ .cb_barrier = rcu_barrier,
+ .fqs = rcu_force_quiescent_state,
+ .stats = NULL,
+ .gp_kthread_dbg = show_rcu_gp_kthreads,
+ .check_boost_failed = rcu_check_boost_fail,
+ .stall_dur = rcu_jiffies_till_stall_check,
+ .irq_capable = 1,
+ .can_boost = IS_ENABLED(CONFIG_RCU_BOOST),
+ .extendables = RCUTORTURE_MAX_EXTEND,
+ .name = "rcu"
};
/*
@@ -492,6 +595,7 @@ static struct rcu_torture_ops rcu_busted_ops = {
.readlock = rcu_torture_read_lock,
.read_delay = rcu_read_delay, /* just reuse rcu's version. */
.readunlock = rcu_torture_read_unlock,
+ .readlock_held = torture_readlock_not_held,
.get_gp_seq = rcu_no_completed,
.deferred_free = rcu_busted_torture_deferred_free,
.sync = synchronize_rcu_busted,
@@ -541,6 +645,11 @@ static void srcu_torture_read_unlock(int idx) __releases(srcu_ctlp)
srcu_read_unlock(srcu_ctlp, idx);
}
+static int torture_srcu_read_lock_held(void)
+{
+ return srcu_read_lock_held(srcu_ctlp);
+}
+
static unsigned long srcu_torture_completed(void)
{
return srcu_batches_completed(srcu_ctlp);
@@ -556,6 +665,21 @@ static void srcu_torture_synchronize(void)
synchronize_srcu(srcu_ctlp);
}
+static unsigned long srcu_torture_get_gp_state(void)
+{
+ return get_state_synchronize_srcu(srcu_ctlp);
+}
+
+static unsigned long srcu_torture_start_gp_poll(void)
+{
+ return start_poll_synchronize_srcu(srcu_ctlp);
+}
+
+static bool srcu_torture_poll_gp_state(unsigned long oldstate)
+{
+ return poll_state_synchronize_srcu(srcu_ctlp, oldstate);
+}
+
static void srcu_torture_call(struct rcu_head *head,
rcu_callback_t func)
{
@@ -583,14 +707,20 @@ static struct rcu_torture_ops srcu_ops = {
.readlock = srcu_torture_read_lock,
.read_delay = srcu_read_delay,
.readunlock = srcu_torture_read_unlock,
+ .readlock_held = torture_srcu_read_lock_held,
.get_gp_seq = srcu_torture_completed,
.deferred_free = srcu_torture_deferred_free,
.sync = srcu_torture_synchronize,
.exp_sync = srcu_torture_synchronize_expedited,
+ .get_gp_state = srcu_torture_get_gp_state,
+ .start_gp_poll = srcu_torture_start_gp_poll,
+ .poll_gp_state = srcu_torture_poll_gp_state,
.call = srcu_torture_call,
.cb_barrier = srcu_torture_barrier,
.stats = srcu_torture_stats,
+ .cbflood_max = 50000,
.irq_capable = 1,
+ .no_pi_lock = IS_ENABLED(CONFIG_TINY_SRCU),
.name = "srcu"
};
@@ -615,14 +745,20 @@ static struct rcu_torture_ops srcud_ops = {
.readlock = srcu_torture_read_lock,
.read_delay = srcu_read_delay,
.readunlock = srcu_torture_read_unlock,
+ .readlock_held = torture_srcu_read_lock_held,
.get_gp_seq = srcu_torture_completed,
.deferred_free = srcu_torture_deferred_free,
.sync = srcu_torture_synchronize,
.exp_sync = srcu_torture_synchronize_expedited,
+ .get_gp_state = srcu_torture_get_gp_state,
+ .start_gp_poll = srcu_torture_start_gp_poll,
+ .poll_gp_state = srcu_torture_poll_gp_state,
.call = srcu_torture_call,
.cb_barrier = srcu_torture_barrier,
.stats = srcu_torture_stats,
+ .cbflood_max = 50000,
.irq_capable = 1,
+ .no_pi_lock = IS_ENABLED(CONFIG_TINY_SRCU),
.name = "srcud"
};
@@ -634,6 +770,7 @@ static struct rcu_torture_ops busted_srcud_ops = {
.readlock = srcu_torture_read_lock,
.read_delay = rcu_read_delay,
.readunlock = srcu_torture_read_unlock,
+ .readlock_held = torture_srcu_read_lock_held,
.get_gp_seq = srcu_torture_completed,
.deferred_free = srcu_torture_deferred_free,
.sync = srcu_torture_synchronize,
@@ -642,11 +779,56 @@ static struct rcu_torture_ops busted_srcud_ops = {
.cb_barrier = srcu_torture_barrier,
.stats = srcu_torture_stats,
.irq_capable = 1,
+ .no_pi_lock = IS_ENABLED(CONFIG_TINY_SRCU),
.extendables = RCUTORTURE_MAX_EXTEND,
.name = "busted_srcud"
};
/*
+ * Definitions for trivial CONFIG_PREEMPT=n-only torture testing.
+ * This implementation does not necessarily work well with CPU hotplug.
+ */
+
+static void synchronize_rcu_trivial(void)
+{
+ int cpu;
+
+ for_each_online_cpu(cpu) {
+ rcutorture_sched_setaffinity(current->pid, cpumask_of(cpu));
+ WARN_ON_ONCE(raw_smp_processor_id() != cpu);
+ }
+}
+
+static int rcu_torture_read_lock_trivial(void) __acquires(RCU)
+{
+ preempt_disable();
+ return 0;
+}
+
+static void rcu_torture_read_unlock_trivial(int idx) __releases(RCU)
+{
+ preempt_enable();
+}
+
+static struct rcu_torture_ops trivial_ops = {
+ .ttype = RCU_TRIVIAL_FLAVOR,
+ .init = rcu_sync_torture_init,
+ .readlock = rcu_torture_read_lock_trivial,
+ .read_delay = rcu_read_delay, /* just reuse rcu's version. */
+ .readunlock = rcu_torture_read_unlock_trivial,
+ .readlock_held = torture_readlock_not_held,
+ .get_gp_seq = rcu_no_completed,
+ .sync = synchronize_rcu_trivial,
+ .exp_sync = synchronize_rcu_trivial,
+ .fqs = NULL,
+ .stats = NULL,
+ .irq_capable = 1,
+ .name = "trivial"
+};
+
+#ifdef CONFIG_TASKS_RCU
+
+/*
* Definitions for RCU-tasks torture testing.
*/
@@ -664,6 +846,11 @@ static void rcu_tasks_torture_deferred_free(struct rcu_torture *p)
call_rcu_tasks(&p->rtort_rcu, rcu_torture_cb);
}
+static void synchronize_rcu_mult_test(void)
+{
+ synchronize_rcu_mult(call_rcu_tasks, call_rcu);
+}
+
static struct rcu_torture_ops tasks_ops = {
.ttype = RCU_TASKS_FLAVOR,
.init = rcu_sync_torture_init,
@@ -673,9 +860,10 @@ static struct rcu_torture_ops tasks_ops = {
.get_gp_seq = rcu_no_completed,
.deferred_free = rcu_tasks_torture_deferred_free,
.sync = synchronize_rcu_tasks,
- .exp_sync = synchronize_rcu_tasks,
+ .exp_sync = synchronize_rcu_mult_test,
.call = call_rcu_tasks,
.cb_barrier = rcu_barrier_tasks,
+ .gp_kthread_dbg = show_rcu_tasks_classic_gp_kthread,
.fqs = NULL,
.stats = NULL,
.irq_capable = 1,
@@ -683,47 +871,108 @@ static struct rcu_torture_ops tasks_ops = {
.name = "tasks"
};
+#define TASKS_OPS &tasks_ops,
+
+#else // #ifdef CONFIG_TASKS_RCU
+
+#define TASKS_OPS
+
+#endif // #else #ifdef CONFIG_TASKS_RCU
+
+
+#ifdef CONFIG_TASKS_RUDE_RCU
+
/*
- * Definitions for trivial CONFIG_PREEMPT=n-only torture testing.
- * This implementation does not necessarily work well with CPU hotplug.
+ * Definitions for rude RCU-tasks torture testing.
*/
-static void synchronize_rcu_trivial(void)
+static void rcu_tasks_rude_torture_deferred_free(struct rcu_torture *p)
{
- int cpu;
-
- for_each_online_cpu(cpu) {
- rcutorture_sched_setaffinity(current->pid, cpumask_of(cpu));
- WARN_ON_ONCE(raw_smp_processor_id() != cpu);
- }
+ call_rcu_tasks_rude(&p->rtort_rcu, rcu_torture_cb);
}
-static int rcu_torture_read_lock_trivial(void) __acquires(RCU)
+static struct rcu_torture_ops tasks_rude_ops = {
+ .ttype = RCU_TASKS_RUDE_FLAVOR,
+ .init = rcu_sync_torture_init,
+ .readlock = rcu_torture_read_lock_trivial,
+ .read_delay = rcu_read_delay, /* just reuse rcu's version. */
+ .readunlock = rcu_torture_read_unlock_trivial,
+ .get_gp_seq = rcu_no_completed,
+ .deferred_free = rcu_tasks_rude_torture_deferred_free,
+ .sync = synchronize_rcu_tasks_rude,
+ .exp_sync = synchronize_rcu_tasks_rude,
+ .call = call_rcu_tasks_rude,
+ .cb_barrier = rcu_barrier_tasks_rude,
+ .gp_kthread_dbg = show_rcu_tasks_rude_gp_kthread,
+ .cbflood_max = 50000,
+ .fqs = NULL,
+ .stats = NULL,
+ .irq_capable = 1,
+ .name = "tasks-rude"
+};
+
+#define TASKS_RUDE_OPS &tasks_rude_ops,
+
+#else // #ifdef CONFIG_TASKS_RUDE_RCU
+
+#define TASKS_RUDE_OPS
+
+#endif // #else #ifdef CONFIG_TASKS_RUDE_RCU
+
+
+#ifdef CONFIG_TASKS_TRACE_RCU
+
+/*
+ * Definitions for tracing RCU-tasks torture testing.
+ */
+
+static int tasks_tracing_torture_read_lock(void)
{
- preempt_disable();
+ rcu_read_lock_trace();
return 0;
}
-static void rcu_torture_read_unlock_trivial(int idx) __releases(RCU)
+static void tasks_tracing_torture_read_unlock(int idx)
{
- preempt_enable();
+ rcu_read_unlock_trace();
}
-static struct rcu_torture_ops trivial_ops = {
- .ttype = RCU_TRIVIAL_FLAVOR,
+static void rcu_tasks_tracing_torture_deferred_free(struct rcu_torture *p)
+{
+ call_rcu_tasks_trace(&p->rtort_rcu, rcu_torture_cb);
+}
+
+static struct rcu_torture_ops tasks_tracing_ops = {
+ .ttype = RCU_TASKS_TRACING_FLAVOR,
.init = rcu_sync_torture_init,
- .readlock = rcu_torture_read_lock_trivial,
- .read_delay = rcu_read_delay, /* just reuse rcu's version. */
- .readunlock = rcu_torture_read_unlock_trivial,
+ .readlock = tasks_tracing_torture_read_lock,
+ .read_delay = srcu_read_delay, /* just reuse srcu's version. */
+ .readunlock = tasks_tracing_torture_read_unlock,
+ .readlock_held = rcu_read_lock_trace_held,
.get_gp_seq = rcu_no_completed,
- .sync = synchronize_rcu_trivial,
- .exp_sync = synchronize_rcu_trivial,
+ .deferred_free = rcu_tasks_tracing_torture_deferred_free,
+ .sync = synchronize_rcu_tasks_trace,
+ .exp_sync = synchronize_rcu_tasks_trace,
+ .call = call_rcu_tasks_trace,
+ .cb_barrier = rcu_barrier_tasks_trace,
+ .gp_kthread_dbg = show_rcu_tasks_trace_gp_kthread,
+ .cbflood_max = 50000,
.fqs = NULL,
.stats = NULL,
.irq_capable = 1,
- .name = "trivial"
+ .slow_gps = 1,
+ .name = "tasks-tracing"
};
+#define TASKS_TRACING_OPS &tasks_tracing_ops,
+
+#else // #ifdef CONFIG_TASKS_TRACE_RCU
+
+#define TASKS_TRACING_OPS
+
+#endif // #else #ifdef CONFIG_TASKS_TRACE_RCU
+
+
static unsigned long rcutorture_seq_diff(unsigned long new, unsigned long old)
{
if (!cur_ops->gp_diff)
@@ -731,32 +980,13 @@ static unsigned long rcutorture_seq_diff(unsigned long new, unsigned long old)
return cur_ops->gp_diff(new, old);
}
-static bool __maybe_unused torturing_tasks(void)
-{
- return cur_ops == &tasks_ops;
-}
-
/*
* RCU torture priority-boost testing. Runs one real-time thread per
- * CPU for moderate bursts, repeatedly registering RCU callbacks and
- * spinning waiting for them to be invoked. If a given callback takes
- * too long to be invoked, we assume that priority inversion has occurred.
+ * CPU for moderate bursts, repeatedly starting grace periods and waiting
+ * for them to complete. If a given grace period takes too long, we assume
+ * that priority inversion has occurred.
*/
-struct rcu_boost_inflight {
- struct rcu_head rcu;
- int inflight;
-};
-
-static void rcu_torture_boost_cb(struct rcu_head *head)
-{
- struct rcu_boost_inflight *rbip =
- container_of(head, struct rcu_boost_inflight, rcu);
-
- /* Ensure RCU-core accesses precede clearing ->inflight */
- smp_store_release(&rbip->inflight, 0);
-}
-
static int old_rt_runtime = -1;
static void rcu_torture_disable_rt_throttle(void)
@@ -783,89 +1013,108 @@ static void rcu_torture_enable_rt_throttle(void)
old_rt_runtime = -1;
}
-static bool rcu_torture_boost_failed(unsigned long start, unsigned long end)
+static bool rcu_torture_boost_failed(unsigned long gp_state, unsigned long *start)
{
- if (end - start > test_boost_duration * HZ - HZ / 2) {
+ int cpu;
+ static int dbg_done;
+ unsigned long end = jiffies;
+ bool gp_done;
+ unsigned long j;
+ static unsigned long last_persist;
+ unsigned long lp;
+ unsigned long mininterval = test_boost_duration * HZ - HZ / 2;
+
+ if (end - *start > mininterval) {
+ // Recheck after checking time to avoid false positives.
+ smp_mb(); // Time check before grace-period check.
+ if (cur_ops->poll_gp_state(gp_state))
+ return false; // passed, though perhaps just barely
+ if (cur_ops->check_boost_failed && !cur_ops->check_boost_failed(gp_state, &cpu)) {
+ // At most one persisted message per boost test.
+ j = jiffies;
+ lp = READ_ONCE(last_persist);
+ if (time_after(j, lp + mininterval) && cmpxchg(&last_persist, lp, j) == lp)
+ pr_info("Boost inversion persisted: No QS from CPU %d\n", cpu);
+ return false; // passed on a technicality
+ }
VERBOSE_TOROUT_STRING("rcu_torture_boost boosting failed");
n_rcu_torture_boost_failure++;
+ if (!xchg(&dbg_done, 1) && cur_ops->gp_kthread_dbg) {
+ pr_info("Boost inversion thread ->rt_priority %u gp_state %lu jiffies %lu\n",
+ current->rt_priority, gp_state, end - *start);
+ cur_ops->gp_kthread_dbg();
+ // Recheck after print to flag grace period ending during splat.
+ gp_done = cur_ops->poll_gp_state(gp_state);
+ pr_info("Boost inversion: GP %lu %s.\n", gp_state,
+ gp_done ? "ended already" : "still pending");
- return true; /* failed */
+ }
+
+ return true; // failed
+ } else if (cur_ops->check_boost_failed && !cur_ops->check_boost_failed(gp_state, NULL)) {
+ *start = jiffies;
}
- return false; /* passed */
+ return false; // passed
}
static int rcu_torture_boost(void *arg)
{
- unsigned long call_rcu_time;
unsigned long endtime;
+ unsigned long gp_state;
+ unsigned long gp_state_time;
unsigned long oldstarttime;
- struct rcu_boost_inflight rbi = { .inflight = 0 };
- struct sched_param sp;
VERBOSE_TOROUT_STRING("rcu_torture_boost started");
/* Set real-time priority. */
- sp.sched_priority = 1;
- if (sched_setscheduler(current, SCHED_FIFO, &sp) < 0) {
- VERBOSE_TOROUT_STRING("rcu_torture_boost RT prio failed!");
- n_rcu_torture_boost_rterror++;
- }
+ sched_set_fifo_low(current);
- init_rcu_head_on_stack(&rbi.rcu);
/* Each pass through the following loop does one boost-test cycle. */
do {
- /* Track if the test failed already in this test interval? */
- bool failed = false;
+ bool failed = false; // Test failed already in this test interval
+ bool gp_initiated = false;
- /* Increment n_rcu_torture_boosts once per boost-test */
- while (!kthread_should_stop()) {
- if (mutex_trylock(&boost_mutex)) {
- n_rcu_torture_boosts++;
- mutex_unlock(&boost_mutex);
- break;
- }
- schedule_timeout_uninterruptible(1);
- }
if (kthread_should_stop())
goto checkwait;
/* Wait for the next test interval. */
- oldstarttime = boost_starttime;
- while (ULONG_CMP_LT(jiffies, oldstarttime)) {
+ oldstarttime = READ_ONCE(boost_starttime);
+ while (time_before(jiffies, oldstarttime)) {
schedule_timeout_interruptible(oldstarttime - jiffies);
- stutter_wait("rcu_torture_boost");
+ if (stutter_wait("rcu_torture_boost"))
+ sched_set_fifo_low(current);
if (torture_must_stop())
goto checkwait;
}
- /* Do one boost-test interval. */
+ // Do one boost-test interval.
endtime = oldstarttime + test_boost_duration * HZ;
- call_rcu_time = jiffies;
- while (ULONG_CMP_LT(jiffies, endtime)) {
- /* If we don't have a callback in flight, post one. */
- if (!smp_load_acquire(&rbi.inflight)) {
- /* RCU core before ->inflight = 1. */
- smp_store_release(&rbi.inflight, 1);
- call_rcu(&rbi.rcu, rcu_torture_boost_cb);
- /* Check if the boost test failed */
- failed = failed ||
- rcu_torture_boost_failed(call_rcu_time,
- jiffies);
- call_rcu_time = jiffies;
+ while (time_before(jiffies, endtime)) {
+ // Has current GP gone too long?
+ if (gp_initiated && !failed && !cur_ops->poll_gp_state(gp_state))
+ failed = rcu_torture_boost_failed(gp_state, &gp_state_time);
+ // If we don't have a grace period in flight, start one.
+ if (!gp_initiated || cur_ops->poll_gp_state(gp_state)) {
+ gp_state = cur_ops->start_gp_poll();
+ gp_initiated = true;
+ gp_state_time = jiffies;
+ }
+ if (stutter_wait("rcu_torture_boost")) {
+ sched_set_fifo_low(current);
+ // If the grace period already ended,
+ // we don't know when that happened, so
+ // start over.
+ if (cur_ops->poll_gp_state(gp_state))
+ gp_initiated = false;
}
- stutter_wait("rcu_torture_boost");
if (torture_must_stop())
goto checkwait;
}
- /*
- * If boost never happened, then inflight will always be 1, in
- * this case the boost check would never happen in the above
- * loop so do another one here.
- */
- if (!failed && smp_load_acquire(&rbi.inflight))
- rcu_torture_boost_failed(call_rcu_time, jiffies);
+ // In case the grace period extended beyond the end of the loop.
+ if (gp_initiated && !failed && !cur_ops->poll_gp_state(gp_state))
+ rcu_torture_boost_failed(gp_state, &gp_state_time);
/*
* Set the start time of the next test interval.
@@ -874,11 +1123,13 @@ static int rcu_torture_boost(void *arg)
* interval. Besides, we are running at RT priority,
* so delays should be relatively rare.
*/
- while (oldstarttime == boost_starttime &&
- !kthread_should_stop()) {
+ while (oldstarttime == READ_ONCE(boost_starttime) && !kthread_should_stop()) {
if (mutex_trylock(&boost_mutex)) {
- boost_starttime = jiffies +
- test_boost_interval * HZ;
+ if (oldstarttime == boost_starttime) {
+ WRITE_ONCE(boost_starttime,
+ jiffies + test_boost_interval * HZ);
+ n_rcu_torture_boosts++;
+ }
mutex_unlock(&boost_mutex);
break;
}
@@ -886,15 +1137,15 @@ static int rcu_torture_boost(void *arg)
}
/* Go do the stutter. */
-checkwait: stutter_wait("rcu_torture_boost");
+checkwait: if (stutter_wait("rcu_torture_boost"))
+ sched_set_fifo_low(current);
} while (!torture_must_stop());
/* Clean up and exit. */
- while (!kthread_should_stop() || smp_load_acquire(&rbi.inflight)) {
+ while (!kthread_should_stop()) {
torture_shutdown_absorb("rcu_torture_boost");
schedule_timeout_uninterruptible(1);
}
- destroy_rcu_head_on_stack(&rbi.rcu);
torture_kthread_stopping("rcu_torture_boost");
return 0;
}
@@ -909,11 +1160,12 @@ rcu_torture_fqs(void *arg)
{
unsigned long fqs_resume_time;
int fqs_burst_remaining;
+ int oldnice = task_nice(current);
VERBOSE_TOROUT_STRING("rcu_torture_fqs task started");
do {
fqs_resume_time = jiffies + fqs_stutter * HZ;
- while (ULONG_CMP_LT(jiffies, fqs_resume_time) &&
+ while (time_before(jiffies, fqs_resume_time) &&
!kthread_should_stop()) {
schedule_timeout_interruptible(1);
}
@@ -924,48 +1176,76 @@ rcu_torture_fqs(void *arg)
udelay(fqs_holdoff);
fqs_burst_remaining -= fqs_holdoff;
}
- stutter_wait("rcu_torture_fqs");
+ if (stutter_wait("rcu_torture_fqs"))
+ sched_set_normal(current, oldnice);
} while (!torture_must_stop());
torture_kthread_stopping("rcu_torture_fqs");
return 0;
}
+// Used by writers to randomly choose from the available grace-period primitives.
+static int synctype[ARRAY_SIZE(rcu_torture_writer_state_names)] = { };
+static int nsynctypes;
+
/*
- * RCU torture writer kthread. Repeatedly substitutes a new structure
- * for that pointed to by rcu_torture_current, freeing the old structure
- * after a series of grace periods (the "pipeline").
+ * Determine which grace-period primitives are available.
*/
-static int
-rcu_torture_writer(void *arg)
+static void rcu_torture_write_types(void)
{
- bool can_expedite = !rcu_gp_is_expedited() && !rcu_gp_is_normal();
- int expediting = 0;
- unsigned long gp_snap;
- bool gp_cond1 = gp_cond, gp_exp1 = gp_exp, gp_normal1 = gp_normal;
- bool gp_sync1 = gp_sync;
- int i;
- struct rcu_torture *rp;
- struct rcu_torture *old_rp;
- static DEFINE_TORTURE_RANDOM(rand);
- int synctype[] = { RTWS_DEF_FREE, RTWS_EXP_SYNC,
- RTWS_COND_GET, RTWS_SYNC };
- int nsynctypes = 0;
-
- VERBOSE_TOROUT_STRING("rcu_torture_writer task started");
- if (!can_expedite)
- pr_alert("%s" TORTURE_FLAG
- " GP expediting controlled from boot/sysfs for %s.\n",
- torture_type, cur_ops->name);
+ bool gp_cond1 = gp_cond, gp_cond_exp1 = gp_cond_exp, gp_cond_full1 = gp_cond_full;
+ bool gp_cond_exp_full1 = gp_cond_exp_full, gp_exp1 = gp_exp, gp_poll_exp1 = gp_poll_exp;
+ bool gp_poll_exp_full1 = gp_poll_exp_full, gp_normal1 = gp_normal, gp_poll1 = gp_poll;
+ bool gp_poll_full1 = gp_poll_full, gp_sync1 = gp_sync;
/* Initialize synctype[] array. If none set, take default. */
- if (!gp_cond1 && !gp_exp1 && !gp_normal1 && !gp_sync1)
- gp_cond1 = gp_exp1 = gp_normal1 = gp_sync1 = true;
- if (gp_cond1 && cur_ops->get_state && cur_ops->cond_sync) {
+ if (!gp_cond1 &&
+ !gp_cond_exp1 &&
+ !gp_cond_full1 &&
+ !gp_cond_exp_full1 &&
+ !gp_exp1 &&
+ !gp_poll_exp1 &&
+ !gp_poll_exp_full1 &&
+ !gp_normal1 &&
+ !gp_poll1 &&
+ !gp_poll_full1 &&
+ !gp_sync1) {
+ gp_cond1 = true;
+ gp_cond_exp1 = true;
+ gp_cond_full1 = true;
+ gp_cond_exp_full1 = true;
+ gp_exp1 = true;
+ gp_poll_exp1 = true;
+ gp_poll_exp_full1 = true;
+ gp_normal1 = true;
+ gp_poll1 = true;
+ gp_poll_full1 = true;
+ gp_sync1 = true;
+ }
+ if (gp_cond1 && cur_ops->get_gp_state && cur_ops->cond_sync) {
synctype[nsynctypes++] = RTWS_COND_GET;
pr_info("%s: Testing conditional GPs.\n", __func__);
- } else if (gp_cond && (!cur_ops->get_state || !cur_ops->cond_sync)) {
+ } else if (gp_cond && (!cur_ops->get_gp_state || !cur_ops->cond_sync)) {
pr_alert("%s: gp_cond without primitives.\n", __func__);
}
+ if (gp_cond_exp1 && cur_ops->get_gp_state_exp && cur_ops->cond_sync_exp) {
+ synctype[nsynctypes++] = RTWS_COND_GET_EXP;
+ pr_info("%s: Testing conditional expedited GPs.\n", __func__);
+ } else if (gp_cond_exp && (!cur_ops->get_gp_state_exp || !cur_ops->cond_sync_exp)) {
+ pr_alert("%s: gp_cond_exp without primitives.\n", __func__);
+ }
+ if (gp_cond_full1 && cur_ops->get_gp_state && cur_ops->cond_sync_full) {
+ synctype[nsynctypes++] = RTWS_COND_GET_FULL;
+ pr_info("%s: Testing conditional full-state GPs.\n", __func__);
+ } else if (gp_cond_full && (!cur_ops->get_gp_state || !cur_ops->cond_sync_full)) {
+ pr_alert("%s: gp_cond_full without primitives.\n", __func__);
+ }
+ if (gp_cond_exp_full1 && cur_ops->get_gp_state_exp && cur_ops->cond_sync_exp_full) {
+ synctype[nsynctypes++] = RTWS_COND_GET_EXP_FULL;
+ pr_info("%s: Testing conditional full-state expedited GPs.\n", __func__);
+ } else if (gp_cond_exp_full &&
+ (!cur_ops->get_gp_state_exp || !cur_ops->cond_sync_exp_full)) {
+ pr_alert("%s: gp_cond_exp_full without primitives.\n", __func__);
+ }
if (gp_exp1 && cur_ops->exp_sync) {
synctype[nsynctypes++] = RTWS_EXP_SYNC;
pr_info("%s: Testing expedited GPs.\n", __func__);
@@ -978,14 +1258,103 @@ rcu_torture_writer(void *arg)
} else if (gp_normal && !cur_ops->deferred_free) {
pr_alert("%s: gp_normal without primitives.\n", __func__);
}
+ if (gp_poll1 && cur_ops->start_gp_poll && cur_ops->poll_gp_state) {
+ synctype[nsynctypes++] = RTWS_POLL_GET;
+ pr_info("%s: Testing polling GPs.\n", __func__);
+ } else if (gp_poll && (!cur_ops->start_gp_poll || !cur_ops->poll_gp_state)) {
+ pr_alert("%s: gp_poll without primitives.\n", __func__);
+ }
+ if (gp_poll_full1 && cur_ops->start_gp_poll_full && cur_ops->poll_gp_state_full) {
+ synctype[nsynctypes++] = RTWS_POLL_GET_FULL;
+ pr_info("%s: Testing polling full-state GPs.\n", __func__);
+ } else if (gp_poll_full && (!cur_ops->start_gp_poll_full || !cur_ops->poll_gp_state_full)) {
+ pr_alert("%s: gp_poll_full without primitives.\n", __func__);
+ }
+ if (gp_poll_exp1 && cur_ops->start_gp_poll_exp && cur_ops->poll_gp_state_exp) {
+ synctype[nsynctypes++] = RTWS_POLL_GET_EXP;
+ pr_info("%s: Testing polling expedited GPs.\n", __func__);
+ } else if (gp_poll_exp && (!cur_ops->start_gp_poll_exp || !cur_ops->poll_gp_state_exp)) {
+ pr_alert("%s: gp_poll_exp without primitives.\n", __func__);
+ }
+ if (gp_poll_exp_full1 && cur_ops->start_gp_poll_exp_full && cur_ops->poll_gp_state_full) {
+ synctype[nsynctypes++] = RTWS_POLL_GET_EXP_FULL;
+ pr_info("%s: Testing polling full-state expedited GPs.\n", __func__);
+ } else if (gp_poll_exp_full &&
+ (!cur_ops->start_gp_poll_exp_full || !cur_ops->poll_gp_state_full)) {
+ pr_alert("%s: gp_poll_exp_full without primitives.\n", __func__);
+ }
if (gp_sync1 && cur_ops->sync) {
synctype[nsynctypes++] = RTWS_SYNC;
pr_info("%s: Testing normal GPs.\n", __func__);
} else if (gp_sync && !cur_ops->sync) {
pr_alert("%s: gp_sync without primitives.\n", __func__);
}
+}
+
+/*
+ * Do the specified rcu_torture_writer() synchronous grace period,
+ * while also testing out the polled APIs. Note well that the single-CPU
+ * grace-period optimizations must be accounted for.
+ */
+static void do_rtws_sync(struct torture_random_state *trsp, void (*sync)(void))
+{
+ unsigned long cookie;
+ struct rcu_gp_oldstate cookie_full;
+ bool dopoll;
+ bool dopoll_full;
+ unsigned long r = torture_random(trsp);
+
+ dopoll = cur_ops->get_gp_state && cur_ops->poll_gp_state && !(r & 0x300);
+ dopoll_full = cur_ops->get_gp_state_full && cur_ops->poll_gp_state_full && !(r & 0xc00);
+ if (dopoll || dopoll_full)
+ cpus_read_lock();
+ if (dopoll)
+ cookie = cur_ops->get_gp_state();
+ if (dopoll_full)
+ cur_ops->get_gp_state_full(&cookie_full);
+ if (cur_ops->poll_need_2gp && cur_ops->poll_need_2gp(dopoll, dopoll_full))
+ sync();
+ sync();
+ WARN_ONCE(dopoll && !cur_ops->poll_gp_state(cookie),
+ "%s: Cookie check 3 failed %pS() online %*pbl.",
+ __func__, sync, cpumask_pr_args(cpu_online_mask));
+ WARN_ONCE(dopoll_full && !cur_ops->poll_gp_state_full(&cookie_full),
+ "%s: Cookie check 4 failed %pS() online %*pbl",
+ __func__, sync, cpumask_pr_args(cpu_online_mask));
+ if (dopoll || dopoll_full)
+ cpus_read_unlock();
+}
+
+/*
+ * RCU torture writer kthread. Repeatedly substitutes a new structure
+ * for that pointed to by rcu_torture_current, freeing the old structure
+ * after a series of grace periods (the "pipeline").
+ */
+static int
+rcu_torture_writer(void *arg)
+{
+ bool boot_ended;
+ bool can_expedite = !rcu_gp_is_expedited() && !rcu_gp_is_normal();
+ unsigned long cookie;
+ struct rcu_gp_oldstate cookie_full;
+ int expediting = 0;
+ unsigned long gp_snap;
+ struct rcu_gp_oldstate gp_snap_full;
+ int i;
+ int idx;
+ int oldnice = task_nice(current);
+ struct rcu_torture *rp;
+ struct rcu_torture *old_rp;
+ static DEFINE_TORTURE_RANDOM(rand);
+ bool stutter_waited;
+
+ VERBOSE_TOROUT_STRING("rcu_torture_writer task started");
+ if (!can_expedite)
+ pr_alert("%s" TORTURE_FLAG
+ " GP expediting controlled from boot/sysfs for %s.\n",
+ torture_type, cur_ops->name);
if (WARN_ONCE(nsynctypes == 0,
- "rcu_torture_writer: No update-side primitives.\n")) {
+ "%s: No update-side primitives.\n", __func__)) {
/*
* No updates primitives, so don't try updating.
* The resulting test won't be testing much, hence the
@@ -993,11 +1362,12 @@ rcu_torture_writer(void *arg)
*/
rcu_torture_writer_state = RTWS_STOPPING;
torture_kthread_stopping("rcu_torture_writer");
+ return 0;
}
do {
rcu_torture_writer_state = RTWS_FIXED_DELAY;
- schedule_timeout_uninterruptible(1);
+ torture_hrtimeout_us(500, 1000, &rand);
rp = rcu_torture_alloc();
if (rp == NULL)
continue;
@@ -1015,7 +1385,40 @@ rcu_torture_writer(void *arg)
if (i > RCU_TORTURE_PIPE_LEN)
i = RCU_TORTURE_PIPE_LEN;
atomic_inc(&rcu_torture_wcount[i]);
- old_rp->rtort_pipe_count++;
+ WRITE_ONCE(old_rp->rtort_pipe_count,
+ old_rp->rtort_pipe_count + 1);
+
+ // Make sure readers block polled grace periods.
+ if (cur_ops->get_gp_state && cur_ops->poll_gp_state) {
+ idx = cur_ops->readlock();
+ cookie = cur_ops->get_gp_state();
+ WARN_ONCE(cur_ops->poll_gp_state(cookie),
+ "%s: Cookie check 1 failed %s(%d) %lu->%lu\n",
+ __func__,
+ rcu_torture_writer_state_getname(),
+ rcu_torture_writer_state,
+ cookie, cur_ops->get_gp_state());
+ if (cur_ops->get_gp_completed) {
+ cookie = cur_ops->get_gp_completed();
+ WARN_ON_ONCE(!cur_ops->poll_gp_state(cookie));
+ }
+ cur_ops->readunlock(idx);
+ }
+ if (cur_ops->get_gp_state_full && cur_ops->poll_gp_state_full) {
+ idx = cur_ops->readlock();
+ cur_ops->get_gp_state_full(&cookie_full);
+ WARN_ONCE(cur_ops->poll_gp_state_full(&cookie_full),
+ "%s: Cookie check 5 failed %s(%d) online %*pbl\n",
+ __func__,
+ rcu_torture_writer_state_getname(),
+ rcu_torture_writer_state,
+ cpumask_pr_args(cpu_online_mask));
+ if (cur_ops->get_gp_completed_full) {
+ cur_ops->get_gp_completed_full(&cookie_full);
+ WARN_ON_ONCE(!cur_ops->poll_gp_state_full(&cookie_full));
+ }
+ cur_ops->readunlock(idx);
+ }
switch (synctype[torture_random(&rand) % nsynctypes]) {
case RTWS_DEF_FREE:
rcu_torture_writer_state = RTWS_DEF_FREE;
@@ -1023,23 +1426,80 @@ rcu_torture_writer(void *arg)
break;
case RTWS_EXP_SYNC:
rcu_torture_writer_state = RTWS_EXP_SYNC;
- cur_ops->exp_sync();
+ do_rtws_sync(&rand, cur_ops->exp_sync);
rcu_torture_pipe_update(old_rp);
break;
case RTWS_COND_GET:
rcu_torture_writer_state = RTWS_COND_GET;
- gp_snap = cur_ops->get_state();
- i = torture_random(&rand) % 16;
- if (i != 0)
- schedule_timeout_interruptible(i);
- udelay(torture_random(&rand) % 1000);
+ gp_snap = cur_ops->get_gp_state();
+ torture_hrtimeout_jiffies(torture_random(&rand) % 16, &rand);
rcu_torture_writer_state = RTWS_COND_SYNC;
cur_ops->cond_sync(gp_snap);
rcu_torture_pipe_update(old_rp);
break;
+ case RTWS_COND_GET_EXP:
+ rcu_torture_writer_state = RTWS_COND_GET_EXP;
+ gp_snap = cur_ops->get_gp_state_exp();
+ torture_hrtimeout_jiffies(torture_random(&rand) % 16, &rand);
+ rcu_torture_writer_state = RTWS_COND_SYNC_EXP;
+ cur_ops->cond_sync_exp(gp_snap);
+ rcu_torture_pipe_update(old_rp);
+ break;
+ case RTWS_COND_GET_FULL:
+ rcu_torture_writer_state = RTWS_COND_GET_FULL;
+ cur_ops->get_gp_state_full(&gp_snap_full);
+ torture_hrtimeout_jiffies(torture_random(&rand) % 16, &rand);
+ rcu_torture_writer_state = RTWS_COND_SYNC_FULL;
+ cur_ops->cond_sync_full(&gp_snap_full);
+ rcu_torture_pipe_update(old_rp);
+ break;
+ case RTWS_COND_GET_EXP_FULL:
+ rcu_torture_writer_state = RTWS_COND_GET_EXP_FULL;
+ cur_ops->get_gp_state_full(&gp_snap_full);
+ torture_hrtimeout_jiffies(torture_random(&rand) % 16, &rand);
+ rcu_torture_writer_state = RTWS_COND_SYNC_EXP_FULL;
+ cur_ops->cond_sync_exp_full(&gp_snap_full);
+ rcu_torture_pipe_update(old_rp);
+ break;
+ case RTWS_POLL_GET:
+ rcu_torture_writer_state = RTWS_POLL_GET;
+ gp_snap = cur_ops->start_gp_poll();
+ rcu_torture_writer_state = RTWS_POLL_WAIT;
+ while (!cur_ops->poll_gp_state(gp_snap))
+ torture_hrtimeout_jiffies(torture_random(&rand) % 16,
+ &rand);
+ rcu_torture_pipe_update(old_rp);
+ break;
+ case RTWS_POLL_GET_FULL:
+ rcu_torture_writer_state = RTWS_POLL_GET_FULL;
+ cur_ops->start_gp_poll_full(&gp_snap_full);
+ rcu_torture_writer_state = RTWS_POLL_WAIT_FULL;
+ while (!cur_ops->poll_gp_state_full(&gp_snap_full))
+ torture_hrtimeout_jiffies(torture_random(&rand) % 16,
+ &rand);
+ rcu_torture_pipe_update(old_rp);
+ break;
+ case RTWS_POLL_GET_EXP:
+ rcu_torture_writer_state = RTWS_POLL_GET_EXP;
+ gp_snap = cur_ops->start_gp_poll_exp();
+ rcu_torture_writer_state = RTWS_POLL_WAIT_EXP;
+ while (!cur_ops->poll_gp_state_exp(gp_snap))
+ torture_hrtimeout_jiffies(torture_random(&rand) % 16,
+ &rand);
+ rcu_torture_pipe_update(old_rp);
+ break;
+ case RTWS_POLL_GET_EXP_FULL:
+ rcu_torture_writer_state = RTWS_POLL_GET_EXP_FULL;
+ cur_ops->start_gp_poll_exp_full(&gp_snap_full);
+ rcu_torture_writer_state = RTWS_POLL_WAIT_EXP_FULL;
+ while (!cur_ops->poll_gp_state_full(&gp_snap_full))
+ torture_hrtimeout_jiffies(torture_random(&rand) % 16,
+ &rand);
+ rcu_torture_pipe_update(old_rp);
+ break;
case RTWS_SYNC:
rcu_torture_writer_state = RTWS_SYNC;
- cur_ops->sync();
+ do_rtws_sync(&rand, cur_ops->sync);
rcu_torture_pipe_update(old_rp);
break;
default:
@@ -1064,18 +1524,25 @@ rcu_torture_writer(void *arg)
!rcu_gp_is_normal();
}
rcu_torture_writer_state = RTWS_STUTTER;
- if (stutter_wait("rcu_torture_writer") &&
- !READ_ONCE(rcu_fwd_cb_nodelay) &&
+ boot_ended = rcu_inkernel_boot_has_ended();
+ stutter_waited = stutter_wait("rcu_torture_writer");
+ if (stutter_waited &&
+ !atomic_read(&rcu_fwd_cb_nodelay) &&
!cur_ops->slow_gps &&
- !torture_must_stop())
+ !torture_must_stop() &&
+ boot_ended)
for (i = 0; i < ARRAY_SIZE(rcu_tortures); i++)
if (list_empty(&rcu_tortures[i].rtort_free) &&
rcu_access_pointer(rcu_torture_current) !=
&rcu_tortures[i]) {
- rcu_ftrace_dump(DUMP_ALL);
+ tracing_off();
WARN(1, "%s: rtort_pipe_count: %d\n", __func__, rcu_tortures[i].rtort_pipe_count);
+ rcu_ftrace_dump(DUMP_ALL);
}
+ if (stutter_waited)
+ sched_set_normal(current, oldnice);
} while (!torture_must_stop());
+ rcu_torture_current = NULL; // Let stats task know that we are done.
/* Reset expediting back to unexpedited. */
if (expediting > 0)
expediting = -expediting;
@@ -1098,26 +1565,91 @@ rcu_torture_writer(void *arg)
static int
rcu_torture_fakewriter(void *arg)
{
+ unsigned long gp_snap;
+ struct rcu_gp_oldstate gp_snap_full;
DEFINE_TORTURE_RANDOM(rand);
VERBOSE_TOROUT_STRING("rcu_torture_fakewriter task started");
set_user_nice(current, MAX_NICE);
+ if (WARN_ONCE(nsynctypes == 0,
+ "%s: No update-side primitives.\n", __func__)) {
+ /*
+ * No updates primitives, so don't try updating.
+ * The resulting test won't be testing much, hence the
+ * above WARN_ONCE().
+ */
+ torture_kthread_stopping("rcu_torture_fakewriter");
+ return 0;
+ }
+
do {
- schedule_timeout_uninterruptible(1 + torture_random(&rand)%10);
- udelay(torture_random(&rand) & 0x3ff);
+ torture_hrtimeout_jiffies(torture_random(&rand) % 10, &rand);
if (cur_ops->cb_barrier != NULL &&
torture_random(&rand) % (nfakewriters * 8) == 0) {
cur_ops->cb_barrier();
- } else if (gp_normal == gp_exp) {
- if (cur_ops->sync && torture_random(&rand) & 0x80)
- cur_ops->sync();
- else if (cur_ops->exp_sync)
+ } else {
+ switch (synctype[torture_random(&rand) % nsynctypes]) {
+ case RTWS_DEF_FREE:
+ break;
+ case RTWS_EXP_SYNC:
cur_ops->exp_sync();
- } else if (gp_normal && cur_ops->sync) {
- cur_ops->sync();
- } else if (cur_ops->exp_sync) {
- cur_ops->exp_sync();
+ break;
+ case RTWS_COND_GET:
+ gp_snap = cur_ops->get_gp_state();
+ torture_hrtimeout_jiffies(torture_random(&rand) % 16, &rand);
+ cur_ops->cond_sync(gp_snap);
+ break;
+ case RTWS_COND_GET_EXP:
+ gp_snap = cur_ops->get_gp_state_exp();
+ torture_hrtimeout_jiffies(torture_random(&rand) % 16, &rand);
+ cur_ops->cond_sync_exp(gp_snap);
+ break;
+ case RTWS_COND_GET_FULL:
+ cur_ops->get_gp_state_full(&gp_snap_full);
+ torture_hrtimeout_jiffies(torture_random(&rand) % 16, &rand);
+ cur_ops->cond_sync_full(&gp_snap_full);
+ break;
+ case RTWS_COND_GET_EXP_FULL:
+ cur_ops->get_gp_state_full(&gp_snap_full);
+ torture_hrtimeout_jiffies(torture_random(&rand) % 16, &rand);
+ cur_ops->cond_sync_exp_full(&gp_snap_full);
+ break;
+ case RTWS_POLL_GET:
+ gp_snap = cur_ops->start_gp_poll();
+ while (!cur_ops->poll_gp_state(gp_snap)) {
+ torture_hrtimeout_jiffies(torture_random(&rand) % 16,
+ &rand);
+ }
+ break;
+ case RTWS_POLL_GET_FULL:
+ cur_ops->start_gp_poll_full(&gp_snap_full);
+ while (!cur_ops->poll_gp_state_full(&gp_snap_full)) {
+ torture_hrtimeout_jiffies(torture_random(&rand) % 16,
+ &rand);
+ }
+ break;
+ case RTWS_POLL_GET_EXP:
+ gp_snap = cur_ops->start_gp_poll_exp();
+ while (!cur_ops->poll_gp_state_exp(gp_snap)) {
+ torture_hrtimeout_jiffies(torture_random(&rand) % 16,
+ &rand);
+ }
+ break;
+ case RTWS_POLL_GET_EXP_FULL:
+ cur_ops->start_gp_poll_exp_full(&gp_snap_full);
+ while (!cur_ops->poll_gp_state_full(&gp_snap_full)) {
+ torture_hrtimeout_jiffies(torture_random(&rand) % 16,
+ &rand);
+ }
+ break;
+ case RTWS_SYNC:
+ cur_ops->sync();
+ break;
+ default:
+ WARN_ON_ONCE(1);
+ break;
+ }
}
stutter_wait("rcu_torture_fakewriter");
} while (!torture_must_stop());
@@ -1131,6 +1663,62 @@ static void rcu_torture_timer_cb(struct rcu_head *rhp)
kfree(rhp);
}
+// Set up and carry out testing of RCU's global memory ordering
+static void rcu_torture_reader_do_mbchk(long myid, struct rcu_torture *rtp,
+ struct torture_random_state *trsp)
+{
+ unsigned long loops;
+ int noc = torture_num_online_cpus();
+ int rdrchked;
+ int rdrchker;
+ struct rcu_torture_reader_check *rtrcp; // Me.
+ struct rcu_torture_reader_check *rtrcp_assigner; // Assigned us to do checking.
+ struct rcu_torture_reader_check *rtrcp_chked; // Reader being checked.
+ struct rcu_torture_reader_check *rtrcp_chker; // Reader doing checking when not me.
+
+ if (myid < 0)
+ return; // Don't try this from timer handlers.
+
+ // Increment my counter.
+ rtrcp = &rcu_torture_reader_mbchk[myid];
+ WRITE_ONCE(rtrcp->rtc_myloops, rtrcp->rtc_myloops + 1);
+
+ // Attempt to assign someone else some checking work.
+ rdrchked = torture_random(trsp) % nrealreaders;
+ rtrcp_chked = &rcu_torture_reader_mbchk[rdrchked];
+ rdrchker = torture_random(trsp) % nrealreaders;
+ rtrcp_chker = &rcu_torture_reader_mbchk[rdrchker];
+ if (rdrchked != myid && rdrchked != rdrchker && noc >= rdrchked && noc >= rdrchker &&
+ smp_load_acquire(&rtrcp->rtc_chkrdr) < 0 && // Pairs with smp_store_release below.
+ !READ_ONCE(rtp->rtort_chkp) &&
+ !smp_load_acquire(&rtrcp_chker->rtc_assigner)) { // Pairs with smp_store_release below.
+ rtrcp->rtc_chkloops = READ_ONCE(rtrcp_chked->rtc_myloops);
+ WARN_ON_ONCE(rtrcp->rtc_chkrdr >= 0);
+ rtrcp->rtc_chkrdr = rdrchked;
+ WARN_ON_ONCE(rtrcp->rtc_ready); // This gets set after the grace period ends.
+ if (cmpxchg_relaxed(&rtrcp_chker->rtc_assigner, NULL, rtrcp) ||
+ cmpxchg_relaxed(&rtp->rtort_chkp, NULL, rtrcp))
+ (void)cmpxchg_relaxed(&rtrcp_chker->rtc_assigner, rtrcp, NULL); // Back out.
+ }
+
+ // If assigned some completed work, do it!
+ rtrcp_assigner = READ_ONCE(rtrcp->rtc_assigner);
+ if (!rtrcp_assigner || !smp_load_acquire(&rtrcp_assigner->rtc_ready))
+ return; // No work or work not yet ready.
+ rdrchked = rtrcp_assigner->rtc_chkrdr;
+ if (WARN_ON_ONCE(rdrchked < 0))
+ return;
+ rtrcp_chked = &rcu_torture_reader_mbchk[rdrchked];
+ loops = READ_ONCE(rtrcp_chked->rtc_myloops);
+ atomic_inc(&n_rcu_torture_mbchk_tries);
+ if (ULONG_CMP_LT(loops, rtrcp_assigner->rtc_chkloops))
+ atomic_inc(&n_rcu_torture_mbchk_fail);
+ rtrcp_assigner->rtc_chkloops = loops + ULONG_MAX / 2;
+ rtrcp_assigner->rtc_ready = 0;
+ smp_store_release(&rtrcp->rtc_assigner, NULL); // Someone else can assign us work.
+ smp_store_release(&rtrcp_assigner->rtc_chkrdr, -1); // Assigner can again assign.
+}
+
/*
* Do one extension of an RCU read-side critical section using the
* current reader state in readstate (set to zero for initial entry
@@ -1144,55 +1732,87 @@ static void rcutorture_one_extend(int *readstate, int newstate,
struct torture_random_state *trsp,
struct rt_read_seg *rtrsp)
{
- int idxnew = -1;
- int idxold = *readstate;
+ unsigned long flags;
+ int idxnew1 = -1;
+ int idxnew2 = -1;
+ int idxold1 = *readstate;
+ int idxold2 = idxold1;
int statesnew = ~*readstate & newstate;
int statesold = *readstate & ~newstate;
- WARN_ON_ONCE(idxold < 0);
- WARN_ON_ONCE((idxold >> RCUTORTURE_RDR_SHIFT) > 1);
+ WARN_ON_ONCE(idxold2 < 0);
+ WARN_ON_ONCE((idxold2 >> RCUTORTURE_RDR_SHIFT_2) > 1);
rtrsp->rt_readstate = newstate;
/* First, put new protection in place to avoid critical-section gap. */
if (statesnew & RCUTORTURE_RDR_BH)
local_bh_disable();
+ if (statesnew & RCUTORTURE_RDR_RBH)
+ rcu_read_lock_bh();
if (statesnew & RCUTORTURE_RDR_IRQ)
local_irq_disable();
if (statesnew & RCUTORTURE_RDR_PREEMPT)
preempt_disable();
- if (statesnew & RCUTORTURE_RDR_RBH)
- rcu_read_lock_bh();
if (statesnew & RCUTORTURE_RDR_SCHED)
rcu_read_lock_sched();
- if (statesnew & RCUTORTURE_RDR_RCU)
- idxnew = cur_ops->readlock() << RCUTORTURE_RDR_SHIFT;
+ if (statesnew & RCUTORTURE_RDR_RCU_1)
+ idxnew1 = (cur_ops->readlock() & 0x1) << RCUTORTURE_RDR_SHIFT_1;
+ if (statesnew & RCUTORTURE_RDR_RCU_2)
+ idxnew2 = (cur_ops->readlock() & 0x1) << RCUTORTURE_RDR_SHIFT_2;
- /* Next, remove old protection, irq first due to bh conflict. */
+ /*
+ * Next, remove old protection, in decreasing order of strength
+ * to avoid unlock paths that aren't safe in the stronger
+ * context. Namely: BH can not be enabled with disabled interrupts.
+ * Additionally PREEMPT_RT requires that BH is enabled in preemptible
+ * context.
+ */
if (statesold & RCUTORTURE_RDR_IRQ)
local_irq_enable();
- if (statesold & RCUTORTURE_RDR_BH)
- local_bh_enable();
if (statesold & RCUTORTURE_RDR_PREEMPT)
preempt_enable();
- if (statesold & RCUTORTURE_RDR_RBH)
- rcu_read_unlock_bh();
if (statesold & RCUTORTURE_RDR_SCHED)
rcu_read_unlock_sched();
- if (statesold & RCUTORTURE_RDR_RCU)
- cur_ops->readunlock(idxold >> RCUTORTURE_RDR_SHIFT);
+ if (statesold & RCUTORTURE_RDR_BH)
+ local_bh_enable();
+ if (statesold & RCUTORTURE_RDR_RBH)
+ rcu_read_unlock_bh();
+ if (statesold & RCUTORTURE_RDR_RCU_2) {
+ cur_ops->readunlock((idxold2 >> RCUTORTURE_RDR_SHIFT_2) & 0x1);
+ WARN_ON_ONCE(idxnew2 != -1);
+ idxold2 = 0;
+ }
+ if (statesold & RCUTORTURE_RDR_RCU_1) {
+ bool lockit;
+
+ lockit = !cur_ops->no_pi_lock && !statesnew && !(torture_random(trsp) & 0xffff);
+ if (lockit)
+ raw_spin_lock_irqsave(&current->pi_lock, flags);
+ cur_ops->readunlock((idxold1 >> RCUTORTURE_RDR_SHIFT_1) & 0x1);
+ WARN_ON_ONCE(idxnew1 != -1);
+ idxold1 = 0;
+ if (lockit)
+ raw_spin_unlock_irqrestore(&current->pi_lock, flags);
+ }
/* Delay if neither beginning nor end and there was a change. */
if ((statesnew || statesold) && *readstate && newstate)
cur_ops->read_delay(trsp, rtrsp);
/* Update the reader state. */
- if (idxnew == -1)
- idxnew = idxold & ~RCUTORTURE_RDR_MASK;
- WARN_ON_ONCE(idxnew < 0);
- WARN_ON_ONCE((idxnew >> RCUTORTURE_RDR_SHIFT) > 1);
- *readstate = idxnew | newstate;
- WARN_ON_ONCE((*readstate >> RCUTORTURE_RDR_SHIFT) < 0);
- WARN_ON_ONCE((*readstate >> RCUTORTURE_RDR_SHIFT) > 1);
+ if (idxnew1 == -1)
+ idxnew1 = idxold1 & RCUTORTURE_RDR_MASK_1;
+ WARN_ON_ONCE(idxnew1 < 0);
+ if (WARN_ON_ONCE((idxnew1 >> RCUTORTURE_RDR_SHIFT_1) > 1))
+ pr_info("Unexpected idxnew1 value of %#x\n", idxnew1);
+ if (idxnew2 == -1)
+ idxnew2 = idxold2 & RCUTORTURE_RDR_MASK_2;
+ WARN_ON_ONCE(idxnew2 < 0);
+ WARN_ON_ONCE((idxnew2 >> RCUTORTURE_RDR_SHIFT_2) > 1);
+ *readstate = idxnew1 | idxnew2 | newstate;
+ WARN_ON_ONCE(*readstate < 0);
+ if (WARN_ON_ONCE((*readstate >> RCUTORTURE_RDR_SHIFT_2) > 1))
+ pr_info("Unexpected idxnew2 value of %#x\n", idxnew2);
}
/* Return the biggest extendables mask given current RCU and boot parameters. */
@@ -1202,7 +1822,7 @@ static int rcutorture_extend_mask_max(void)
WARN_ON_ONCE(extendables & ~RCUTORTURE_MAX_EXTEND);
mask = extendables & RCUTORTURE_MAX_EXTEND & cur_ops->extendables;
- mask = mask | RCUTORTURE_RDR_RCU;
+ mask = mask | RCUTORTURE_RDR_RCU_1 | RCUTORTURE_RDR_RCU_2;
return mask;
}
@@ -1213,19 +1833,45 @@ rcutorture_extend_mask(int oldmask, struct torture_random_state *trsp)
int mask = rcutorture_extend_mask_max();
unsigned long randmask1 = torture_random(trsp) >> 8;
unsigned long randmask2 = randmask1 >> 3;
+ unsigned long preempts = RCUTORTURE_RDR_PREEMPT | RCUTORTURE_RDR_SCHED;
+ unsigned long preempts_irq = preempts | RCUTORTURE_RDR_IRQ;
+ unsigned long bhs = RCUTORTURE_RDR_BH | RCUTORTURE_RDR_RBH;
- WARN_ON_ONCE(mask >> RCUTORTURE_RDR_SHIFT);
+ WARN_ON_ONCE(mask >> RCUTORTURE_RDR_SHIFT_1);
/* Mostly only one bit (need preemption!), sometimes lots of bits. */
if (!(randmask1 & 0x7))
mask = mask & randmask2;
else
mask = mask & (1 << (randmask2 % RCUTORTURE_RDR_NBITS));
- /* Can't enable bh w/irq disabled. */
- if ((mask & RCUTORTURE_RDR_IRQ) &&
- ((!(mask & RCUTORTURE_RDR_BH) && (oldmask & RCUTORTURE_RDR_BH)) ||
- (!(mask & RCUTORTURE_RDR_RBH) && (oldmask & RCUTORTURE_RDR_RBH))))
- mask |= RCUTORTURE_RDR_BH | RCUTORTURE_RDR_RBH;
- return mask ?: RCUTORTURE_RDR_RCU;
+
+ // Can't have nested RCU reader without outer RCU reader.
+ if (!(mask & RCUTORTURE_RDR_RCU_1) && (mask & RCUTORTURE_RDR_RCU_2)) {
+ if (oldmask & RCUTORTURE_RDR_RCU_1)
+ mask &= ~RCUTORTURE_RDR_RCU_2;
+ else
+ mask |= RCUTORTURE_RDR_RCU_1;
+ }
+
+ /*
+ * Can't enable bh w/irq disabled.
+ */
+ if (mask & RCUTORTURE_RDR_IRQ)
+ mask |= oldmask & bhs;
+
+ /*
+ * Ideally these sequences would be detected in debug builds
+ * (regardless of RT), but until then don't stop testing
+ * them on non-RT.
+ */
+ if (IS_ENABLED(CONFIG_PREEMPT_RT)) {
+ /* Can't modify BH in atomic context */
+ if (oldmask & preempts_irq)
+ mask &= ~bhs;
+ if ((oldmask | mask) & preempts_irq)
+ mask |= oldmask & bhs;
+ }
+
+ return mask ?: RCUTORTURE_RDR_RCU_1;
}
/*
@@ -1258,8 +1904,11 @@ rcutorture_loop_extend(int *readstate, struct torture_random_state *trsp,
* no data to read. Can be invoked both from process context and
* from a timer handler.
*/
-static bool rcu_torture_one_read(struct torture_random_state *trsp)
+static bool rcu_torture_one_read(struct torture_random_state *trsp, long myid)
{
+ bool checkpolling = !(torture_random(trsp) & 0xfff);
+ unsigned long cookie;
+ struct rcu_gp_oldstate cookie_full;
int i;
unsigned long started;
unsigned long completed;
@@ -1272,15 +1921,19 @@ static bool rcu_torture_one_read(struct torture_random_state *trsp)
struct rt_read_seg *rtrsp1;
unsigned long long ts;
+ WARN_ON_ONCE(!rcu_is_watching());
newstate = rcutorture_extend_mask(readstate, trsp);
rcutorture_one_extend(&readstate, newstate, trsp, rtrsp++);
+ if (checkpolling) {
+ if (cur_ops->get_gp_state && cur_ops->poll_gp_state)
+ cookie = cur_ops->get_gp_state();
+ if (cur_ops->get_gp_state_full && cur_ops->poll_gp_state_full)
+ cur_ops->get_gp_state_full(&cookie_full);
+ }
started = cur_ops->get_gp_seq();
ts = rcu_trace_clock_local();
p = rcu_dereference_check(rcu_torture_current,
- rcu_read_lock_bh_held() ||
- rcu_read_lock_sched_held() ||
- srcu_read_lock_held(srcu_ctlp) ||
- torturing_tasks());
+ !cur_ops->readlock_held || cur_ops->readlock_held());
if (p == NULL) {
/* Wait for rcu_torture_writer to get underway */
rcutorture_one_extend(&readstate, 0, trsp, rtrsp);
@@ -1288,9 +1941,10 @@ static bool rcu_torture_one_read(struct torture_random_state *trsp)
}
if (p->rtort_mbtest == 0)
atomic_inc(&n_rcu_torture_mberror);
+ rcu_torture_reader_do_mbchk(myid, p, trsp);
rtrsp = rcutorture_loop_extend(&readstate, trsp, rtrsp);
preempt_disable();
- pipe_count = p->rtort_pipe_count;
+ pipe_count = READ_ONCE(p->rtort_pipe_count);
if (pipe_count > RCU_TORTURE_PIPE_LEN) {
/* Should not happen, but... */
pipe_count = RCU_TORTURE_PIPE_LEN;
@@ -1309,8 +1963,27 @@ static bool rcu_torture_one_read(struct torture_random_state *trsp)
}
__this_cpu_inc(rcu_torture_batch[completed]);
preempt_enable();
+ if (checkpolling) {
+ if (cur_ops->get_gp_state && cur_ops->poll_gp_state)
+ WARN_ONCE(cur_ops->poll_gp_state(cookie),
+ "%s: Cookie check 2 failed %s(%d) %lu->%lu\n",
+ __func__,
+ rcu_torture_writer_state_getname(),
+ rcu_torture_writer_state,
+ cookie, cur_ops->get_gp_state());
+ if (cur_ops->get_gp_state_full && cur_ops->poll_gp_state_full)
+ WARN_ONCE(cur_ops->poll_gp_state_full(&cookie_full),
+ "%s: Cookie check 6 failed %s(%d) online %*pbl\n",
+ __func__,
+ rcu_torture_writer_state_getname(),
+ rcu_torture_writer_state,
+ cpumask_pr_args(cpu_online_mask));
+ }
rcutorture_one_extend(&readstate, 0, trsp, rtrsp);
- WARN_ON_ONCE(readstate & RCUTORTURE_RDR_MASK);
+ WARN_ON_ONCE(readstate);
+ // This next splat is expected behavior if leakpointer, especially
+ // for CONFIG_RCU_STRICT_GRACE_PERIOD=y kernels.
+ WARN_ON_ONCE(leakpointer && READ_ONCE(p->rtort_pipe_count) > 1);
/* If error or close call, record the sequence of reader protections. */
if ((pipe_count > 1 || completed > 1) && !xchg(&err_segs_recorded, 1)) {
@@ -1334,7 +2007,7 @@ static DEFINE_TORTURE_RANDOM_PERCPU(rcu_torture_timer_rand);
static void rcu_torture_timer(struct timer_list *unused)
{
atomic_long_inc(&n_rcu_torture_timers);
- (void)rcu_torture_one_read(this_cpu_ptr(&rcu_torture_timer_rand));
+ (void)rcu_torture_one_read(this_cpu_ptr(&rcu_torture_timer_rand), -1);
/* Test call_rcu() invocation from interrupt handler. */
if (cur_ops->call) {
@@ -1370,13 +2043,13 @@ rcu_torture_reader(void *arg)
if (!timer_pending(&t))
mod_timer(&t, jiffies + 1);
}
- if (!rcu_torture_one_read(&rand) && !torture_must_stop())
+ if (!rcu_torture_one_read(&rand, myid) && !torture_must_stop())
schedule_timeout_interruptible(HZ);
if (time_after(jiffies, lastsleep) && !torture_must_stop()) {
- schedule_timeout_interruptible(1);
+ torture_hrtimeout_us(500, 1000, &rand);
lastsleep = jiffies + 10;
}
- while (num_online_cpus() < mynumonline && !torture_must_stop())
+ while (torture_num_online_cpus() < mynumonline && !torture_must_stop())
schedule_timeout_interruptible(HZ / 5);
stutter_wait("rcu_torture_reader");
} while (!torture_must_stop());
@@ -1390,6 +2063,53 @@ rcu_torture_reader(void *arg)
}
/*
+ * Randomly Toggle CPUs' callback-offload state. This uses hrtimers to
+ * increase race probabilities and fuzzes the interval between toggling.
+ */
+static int rcu_nocb_toggle(void *arg)
+{
+ int cpu;
+ int maxcpu = -1;
+ int oldnice = task_nice(current);
+ long r;
+ DEFINE_TORTURE_RANDOM(rand);
+ ktime_t toggle_delay;
+ unsigned long toggle_fuzz;
+ ktime_t toggle_interval = ms_to_ktime(nocbs_toggle);
+
+ VERBOSE_TOROUT_STRING("rcu_nocb_toggle task started");
+ while (!rcu_inkernel_boot_has_ended())
+ schedule_timeout_interruptible(HZ / 10);
+ for_each_online_cpu(cpu)
+ maxcpu = cpu;
+ WARN_ON(maxcpu < 0);
+ if (toggle_interval > ULONG_MAX)
+ toggle_fuzz = ULONG_MAX >> 3;
+ else
+ toggle_fuzz = toggle_interval >> 3;
+ if (toggle_fuzz <= 0)
+ toggle_fuzz = NSEC_PER_USEC;
+ do {
+ r = torture_random(&rand);
+ cpu = (r >> 4) % (maxcpu + 1);
+ if (r & 0x1) {
+ rcu_nocb_cpu_offload(cpu);
+ atomic_long_inc(&n_nocb_offload);
+ } else {
+ rcu_nocb_cpu_deoffload(cpu);
+ atomic_long_inc(&n_nocb_deoffload);
+ }
+ toggle_delay = torture_random(&rand) % toggle_fuzz + toggle_interval;
+ set_current_state(TASK_INTERRUPTIBLE);
+ schedule_hrtimeout(&toggle_delay, HRTIMER_MODE_REL);
+ if (stutter_wait("rcu_nocb_toggle"))
+ sched_set_normal(current, oldnice);
+ } while (!torture_must_stop());
+ torture_kthread_stopping("rcu_nocb_toggle");
+ return 0;
+}
+
+/*
* Print torture statistics. Caller must ensure that there is only
* one call to this function at a given time!!! This is normally
* accomplished by relying on the module system to only have one copy
@@ -1404,32 +2124,35 @@ rcu_torture_stats_print(void)
int i;
long pipesummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
long batchsummary[RCU_TORTURE_PIPE_LEN + 1] = { 0 };
+ struct rcu_torture *rtcp;
static unsigned long rtcv_snap = ULONG_MAX;
static bool splatted;
struct task_struct *wtp;
for_each_possible_cpu(cpu) {
for (i = 0; i < RCU_TORTURE_PIPE_LEN + 1; i++) {
- pipesummary[i] += per_cpu(rcu_torture_count, cpu)[i];
- batchsummary[i] += per_cpu(rcu_torture_batch, cpu)[i];
+ pipesummary[i] += READ_ONCE(per_cpu(rcu_torture_count, cpu)[i]);
+ batchsummary[i] += READ_ONCE(per_cpu(rcu_torture_batch, cpu)[i]);
}
}
- for (i = RCU_TORTURE_PIPE_LEN - 1; i >= 0; i--) {
+ for (i = RCU_TORTURE_PIPE_LEN; i >= 0; i--) {
if (pipesummary[i] != 0)
break;
}
pr_alert("%s%s ", torture_type, TORTURE_FLAG);
+ rtcp = rcu_access_pointer(rcu_torture_current);
pr_cont("rtc: %p %s: %lu tfle: %d rta: %d rtaf: %d rtf: %d ",
- rcu_torture_current,
- rcu_torture_current ? "ver" : "VER",
+ rtcp,
+ rtcp && !rcu_stall_is_suppressed_at_boot() ? "ver" : "VER",
rcu_torture_current_version,
list_empty(&rcu_torture_freelist),
atomic_read(&n_rcu_torture_alloc),
atomic_read(&n_rcu_torture_alloc_fail),
atomic_read(&n_rcu_torture_free));
- pr_cont("rtmbe: %d rtbe: %ld rtbke: %ld rtbre: %ld ",
+ pr_cont("rtmbe: %d rtmbkf: %d/%d rtbe: %ld rtbke: %ld rtbre: %ld ",
atomic_read(&n_rcu_torture_mberror),
+ atomic_read(&n_rcu_torture_mbchk_fail), atomic_read(&n_rcu_torture_mbchk_tries),
n_rcu_torture_barrier_error,
n_rcu_torture_boost_ktrerror,
n_rcu_torture_boost_rterror);
@@ -1438,23 +2161,28 @@ rcu_torture_stats_print(void)
n_rcu_torture_boosts,
atomic_long_read(&n_rcu_torture_timers));
torture_onoff_stats();
- pr_cont("barrier: %ld/%ld:%ld\n",
- n_barrier_successes,
- n_barrier_attempts,
- n_rcu_torture_barrier_error);
+ pr_cont("barrier: %ld/%ld:%ld ",
+ data_race(n_barrier_successes),
+ data_race(n_barrier_attempts),
+ data_race(n_rcu_torture_barrier_error));
+ pr_cont("read-exits: %ld ", data_race(n_read_exits)); // Statistic.
+ pr_cont("nocb-toggles: %ld:%ld\n",
+ atomic_long_read(&n_nocb_offload), atomic_long_read(&n_nocb_deoffload));
pr_alert("%s%s ", torture_type, TORTURE_FLAG);
if (atomic_read(&n_rcu_torture_mberror) ||
+ atomic_read(&n_rcu_torture_mbchk_fail) ||
n_rcu_torture_barrier_error || n_rcu_torture_boost_ktrerror ||
n_rcu_torture_boost_rterror || n_rcu_torture_boost_failure ||
i > 1) {
pr_cont("%s", "!!! ");
atomic_inc(&n_rcu_torture_error);
WARN_ON_ONCE(atomic_read(&n_rcu_torture_mberror));
+ WARN_ON_ONCE(atomic_read(&n_rcu_torture_mbchk_fail));
WARN_ON_ONCE(n_rcu_torture_barrier_error); // rcu_barrier()
WARN_ON_ONCE(n_rcu_torture_boost_ktrerror); // no boost kthread
WARN_ON_ONCE(n_rcu_torture_boost_rterror); // can't set RT prio
- WARN_ON_ONCE(n_rcu_torture_boost_failure); // RCU boost failed
+ WARN_ON_ONCE(n_rcu_torture_boost_failure); // boost failed (TIMER_SOFTIRQ RT prio?)
WARN_ON_ONCE(i > 1); // Too-short grace period
}
pr_cont("Reader Pipe: ");
@@ -1478,7 +2206,8 @@ rcu_torture_stats_print(void)
if (cur_ops->stats)
cur_ops->stats();
if (rtcv_snap == rcu_torture_current_version &&
- rcu_torture_current != NULL) {
+ rcu_access_pointer(rcu_torture_current) &&
+ !rcu_stall_is_suppressed()) {
int __maybe_unused flags = 0;
unsigned long __maybe_unused gp_seq = 0;
@@ -1487,16 +2216,17 @@ rcu_torture_stats_print(void)
srcutorture_get_gp_data(cur_ops->ttype, srcu_ctlp,
&flags, &gp_seq);
wtp = READ_ONCE(writer_task);
- pr_alert("??? Writer stall state %s(%d) g%lu f%#x ->state %#lx cpu %d\n",
+ pr_alert("??? Writer stall state %s(%d) g%lu f%#x ->state %#x cpu %d\n",
rcu_torture_writer_state_getname(),
rcu_torture_writer_state, gp_seq, flags,
- wtp == NULL ? ~0UL : wtp->state,
+ wtp == NULL ? ~0U : wtp->__state,
wtp == NULL ? -1 : (int)task_cpu(wtp));
if (!splatted && wtp) {
sched_show_task(wtp);
splatted = true;
}
- show_rcu_gp_kthreads();
+ if (cur_ops->gp_kthread_dbg)
+ cur_ops->gp_kthread_dbg();
rcu_ftrace_dump(DUMP_ALL);
}
rtcv_snap = rcu_torture_current_version;
@@ -1519,6 +2249,56 @@ rcu_torture_stats(void *arg)
return 0;
}
+/* Test mem_dump_obj() and friends. */
+static void rcu_torture_mem_dump_obj(void)
+{
+ struct rcu_head *rhp;
+ struct kmem_cache *kcp;
+ static int z;
+
+ kcp = kmem_cache_create("rcuscale", 136, 8, SLAB_STORE_USER, NULL);
+ if (WARN_ON_ONCE(!kcp))
+ return;
+ rhp = kmem_cache_alloc(kcp, GFP_KERNEL);
+ if (WARN_ON_ONCE(!rhp)) {
+ kmem_cache_destroy(kcp);
+ return;
+ }
+ pr_alert("mem_dump_obj() slab test: rcu_torture_stats = %px, &rhp = %px, rhp = %px, &z = %px\n", stats_task, &rhp, rhp, &z);
+ pr_alert("mem_dump_obj(ZERO_SIZE_PTR):");
+ mem_dump_obj(ZERO_SIZE_PTR);
+ pr_alert("mem_dump_obj(NULL):");
+ mem_dump_obj(NULL);
+ pr_alert("mem_dump_obj(%px):", &rhp);
+ mem_dump_obj(&rhp);
+ pr_alert("mem_dump_obj(%px):", rhp);
+ mem_dump_obj(rhp);
+ pr_alert("mem_dump_obj(%px):", &rhp->func);
+ mem_dump_obj(&rhp->func);
+ pr_alert("mem_dump_obj(%px):", &z);
+ mem_dump_obj(&z);
+ kmem_cache_free(kcp, rhp);
+ kmem_cache_destroy(kcp);
+ rhp = kmalloc(sizeof(*rhp), GFP_KERNEL);
+ if (WARN_ON_ONCE(!rhp))
+ return;
+ pr_alert("mem_dump_obj() kmalloc test: rcu_torture_stats = %px, &rhp = %px, rhp = %px\n", stats_task, &rhp, rhp);
+ pr_alert("mem_dump_obj(kmalloc %px):", rhp);
+ mem_dump_obj(rhp);
+ pr_alert("mem_dump_obj(kmalloc %px):", &rhp->func);
+ mem_dump_obj(&rhp->func);
+ kfree(rhp);
+ rhp = vmalloc(4096);
+ if (WARN_ON_ONCE(!rhp))
+ return;
+ pr_alert("mem_dump_obj() vmalloc test: rcu_torture_stats = %px, &rhp = %px, rhp = %px\n", stats_task, &rhp, rhp);
+ pr_alert("mem_dump_obj(vmalloc %px):", rhp);
+ mem_dump_obj(rhp);
+ pr_alert("mem_dump_obj(vmalloc %px):", &rhp->func);
+ mem_dump_obj(&rhp->func);
+ vfree(rhp);
+}
+
static void
rcu_torture_print_module_parms(struct rcu_torture_ops *cur_ops, const char *tag)
{
@@ -1530,16 +2310,22 @@ rcu_torture_print_module_parms(struct rcu_torture_ops *cur_ops, const char *tag)
"test_boost=%d/%d test_boost_interval=%d "
"test_boost_duration=%d shutdown_secs=%d "
"stall_cpu=%d stall_cpu_holdoff=%d stall_cpu_irqsoff=%d "
+ "stall_cpu_block=%d "
"n_barrier_cbs=%d "
- "onoff_interval=%d onoff_holdoff=%d\n",
+ "onoff_interval=%d onoff_holdoff=%d "
+ "read_exit_delay=%d read_exit_burst=%d "
+ "nocbs_nthreads=%d nocbs_toggle=%d\n",
torture_type, tag, nrealreaders, nfakewriters,
stat_interval, verbose, test_no_idle_hz, shuffle_interval,
stutter, irqreader, fqs_duration, fqs_holdoff, fqs_stutter,
test_boost, cur_ops->can_boost,
test_boost_interval, test_boost_duration, shutdown_secs,
stall_cpu, stall_cpu_holdoff, stall_cpu_irqsoff,
+ stall_cpu_block,
n_barrier_cbs,
- onoff_interval, onoff_holdoff);
+ onoff_interval, onoff_holdoff,
+ read_exit_delay, read_exit_burst,
+ nocbs_nthreads, nocbs_toggle);
}
static int rcutorture_booster_cleanup(unsigned int cpu)
@@ -1566,13 +2352,25 @@ static int rcutorture_booster_init(unsigned int cpu)
if (boost_tasks[cpu] != NULL)
return 0; /* Already created, nothing more to do. */
+ // Testing RCU priority boosting requires rcutorture do
+ // some serious abuse. Counter this by running ksoftirqd
+ // at higher priority.
+ if (IS_BUILTIN(CONFIG_RCU_TORTURE_TEST)) {
+ struct sched_param sp;
+ struct task_struct *t;
+
+ t = per_cpu(ksoftirqd, cpu);
+ WARN_ON_ONCE(!t);
+ sp.sched_priority = 2;
+ sched_setscheduler_nocheck(t, SCHED_FIFO, &sp);
+ }
+
/* Don't allow time recalculation while creating a new task. */
mutex_lock(&boost_mutex);
rcu_torture_disable_rt_throttle();
VERBOSE_TOROUT_STRING("Creating rcu_torture_boost task");
- boost_tasks[cpu] = kthread_create_on_node(rcu_torture_boost, NULL,
- cpu_to_node(cpu),
- "rcu_torture_boost");
+ boost_tasks[cpu] = kthread_run_on_cpu(rcu_torture_boost, NULL,
+ cpu, "rcu_torture_boost_%u");
if (IS_ERR(boost_tasks[cpu])) {
retval = PTR_ERR(boost_tasks[cpu]);
VERBOSE_TOROUT_STRING("rcu_torture_boost task create failed");
@@ -1581,8 +2379,6 @@ static int rcutorture_booster_init(unsigned int cpu)
mutex_unlock(&boost_mutex);
return retval;
}
- kthread_bind(boost_tasks[cpu], cpu);
- wake_up_process(boost_tasks[cpu]);
mutex_unlock(&boost_mutex);
return 0;
}
@@ -1593,6 +2389,7 @@ static int rcutorture_booster_init(unsigned int cpu)
*/
static int rcu_torture_stall(void *args)
{
+ int idx;
unsigned long stop_at;
VERBOSE_TOROUT_STRING("rcu_torture_stall task started");
@@ -1601,26 +2398,44 @@ static int rcu_torture_stall(void *args)
schedule_timeout_interruptible(stall_cpu_holdoff * HZ);
VERBOSE_TOROUT_STRING("rcu_torture_stall end holdoff");
}
- if (!kthread_should_stop()) {
+ if (!kthread_should_stop() && stall_gp_kthread > 0) {
+ VERBOSE_TOROUT_STRING("rcu_torture_stall begin GP stall");
+ rcu_gp_set_torture_wait(stall_gp_kthread * HZ);
+ for (idx = 0; idx < stall_gp_kthread + 2; idx++) {
+ if (kthread_should_stop())
+ break;
+ schedule_timeout_uninterruptible(HZ);
+ }
+ }
+ if (!kthread_should_stop() && stall_cpu > 0) {
+ VERBOSE_TOROUT_STRING("rcu_torture_stall begin CPU stall");
stop_at = ktime_get_seconds() + stall_cpu;
/* RCU CPU stall is expected behavior in following code. */
- rcu_read_lock();
+ idx = cur_ops->readlock();
if (stall_cpu_irqsoff)
local_irq_disable();
- else
+ else if (!stall_cpu_block)
preempt_disable();
- pr_alert("rcu_torture_stall start on CPU %d.\n",
- smp_processor_id());
+ pr_alert("%s start on CPU %d.\n",
+ __func__, raw_smp_processor_id());
while (ULONG_CMP_LT((unsigned long)ktime_get_seconds(),
stop_at))
- continue; /* Induce RCU CPU stall warning. */
+ if (stall_cpu_block) {
+#ifdef CONFIG_PREEMPTION
+ preempt_schedule();
+#else
+ schedule_timeout_uninterruptible(HZ);
+#endif
+ } else if (stall_no_softlockup) {
+ touch_softlockup_watchdog();
+ }
if (stall_cpu_irqsoff)
local_irq_enable();
- else
+ else if (!stall_cpu_block)
preempt_enable();
- rcu_read_unlock();
- pr_alert("rcu_torture_stall end.\n");
+ cur_ops->readunlock(idx);
}
+ pr_alert("%s end.\n", __func__);
torture_shutdown_absorb("rcu_torture_stall");
while (!kthread_should_stop())
schedule_timeout_interruptible(10 * HZ);
@@ -1630,7 +2445,7 @@ static int rcu_torture_stall(void *args)
/* Spawn CPU-stall kthread, if stall_cpu specified. */
static int __init rcu_torture_stall_init(void)
{
- if (stall_cpu <= 0)
+ if (stall_cpu <= 0 && stall_gp_kthread <= 0)
return 0;
return torture_create_kthread(rcu_torture_stall, NULL, stall_task);
}
@@ -1684,10 +2499,14 @@ struct rcu_fwd {
unsigned long rcu_fwd_startat;
struct rcu_launder_hist n_launders_hist[N_LAUNDERS_HIST];
unsigned long rcu_launder_gp_seq_start;
+ int rcu_fwd_id;
};
-struct rcu_fwd *rcu_fwds;
-bool rcu_fwd_emergency_stop;
+static DEFINE_MUTEX(rcu_fwd_mutex);
+static struct rcu_fwd *rcu_fwds;
+static unsigned long rcu_fwd_seq;
+static atomic_long_t rcu_fwd_max_cbs;
+static bool rcu_fwd_emergency_stop;
static void rcu_torture_fwd_cb_hist(struct rcu_fwd *rfp)
{
@@ -1699,8 +2518,8 @@ static void rcu_torture_fwd_cb_hist(struct rcu_fwd *rfp)
for (i = ARRAY_SIZE(rfp->n_launders_hist) - 1; i > 0; i--)
if (rfp->n_launders_hist[i].n_launders > 0)
break;
- pr_alert("%s: Callback-invocation histogram (duration %lu jiffies):",
- __func__, jiffies - rfp->rcu_fwd_startat);
+ pr_alert("%s: Callback-invocation histogram %d (duration %lu jiffies):",
+ __func__, rfp->rcu_fwd_id, jiffies - rfp->rcu_fwd_startat);
gps_old = rfp->rcu_launder_gp_seq_start;
for (j = 0; j <= i; j++) {
gps = rfp->n_launders_hist[j].launder_gp_seq;
@@ -1798,13 +2617,16 @@ static void rcu_torture_fwd_prog_nr(struct rcu_fwd *rfp,
unsigned long stopat;
static DEFINE_TORTURE_RANDOM(trs);
- if (cur_ops->call && cur_ops->sync && cur_ops->cb_barrier) {
+ pr_alert("%s: Starting forward-progress test %d\n", __func__, rfp->rcu_fwd_id);
+ if (!cur_ops->sync)
+ return; // Cannot do need_resched() forward progress testing without ->sync.
+ if (cur_ops->call && cur_ops->cb_barrier) {
init_rcu_head_on_stack(&fcs.rh);
selfpropcb = true;
}
/* Tight loop containing cond_resched(). */
- WRITE_ONCE(rcu_fwd_cb_nodelay, true);
+ atomic_inc(&rcu_fwd_cb_nodelay);
cur_ops->sync(); /* Later readers see above write. */
if (selfpropcb) {
WRITE_ONCE(fcs.stop, 0);
@@ -1834,11 +2656,13 @@ static void rcu_torture_fwd_prog_nr(struct rcu_fwd *rfp,
cver = READ_ONCE(rcu_torture_current_version) - cver;
gps = rcutorture_seq_diff(cur_ops->get_gp_seq(), gps);
WARN_ON(!cver && gps < 2);
- pr_alert("%s: Duration %ld cver %ld gps %ld\n", __func__, dur, cver, gps);
+ pr_alert("%s: %d Duration %ld cver %ld gps %ld\n", __func__,
+ rfp->rcu_fwd_id, dur, cver, gps);
}
if (selfpropcb) {
WRITE_ONCE(fcs.stop, 1);
cur_ops->sync(); /* Wait for running CB to complete. */
+ pr_alert("%s: Waiting for CBs: %pS() %d\n", __func__, cur_ops->cb_barrier, rfp->rcu_fwd_id);
cur_ops->cb_barrier(); /* Wait for queued callbacks. */
}
@@ -1847,7 +2671,7 @@ static void rcu_torture_fwd_prog_nr(struct rcu_fwd *rfp,
destroy_rcu_head_on_stack(&fcs.rh);
}
schedule_timeout_uninterruptible(HZ / 10); /* Let kthreads recover. */
- WRITE_ONCE(rcu_fwd_cb_nodelay, false);
+ atomic_dec(&rcu_fwd_cb_nodelay);
}
/* Carry out call_rcu() forward-progress testing. */
@@ -1867,13 +2691,14 @@ static void rcu_torture_fwd_prog_cr(struct rcu_fwd *rfp)
unsigned long stopat;
unsigned long stoppedat;
+ pr_alert("%s: Starting forward-progress test %d\n", __func__, rfp->rcu_fwd_id);
if (READ_ONCE(rcu_fwd_emergency_stop))
return; /* Get out of the way quickly, no GP wait! */
if (!cur_ops->call)
return; /* Can't do call_rcu() fwd prog without ->call. */
/* Loop continuously posting RCU callbacks. */
- WRITE_ONCE(rcu_fwd_cb_nodelay, true);
+ atomic_inc(&rcu_fwd_cb_nodelay);
cur_ops->sync(); /* Later readers see above write. */
WRITE_ONCE(rfp->rcu_fwd_startat, jiffies);
stopat = rfp->rcu_fwd_startat + MAX_FWD_CB_JIFFIES;
@@ -1902,7 +2727,7 @@ static void rcu_torture_fwd_prog_cr(struct rcu_fwd *rfp)
rfp->rcu_fwd_cb_head = rfcpn;
n_launders++;
n_launders_sa++;
- } else {
+ } else if (!cur_ops->cbflood_max || cur_ops->cbflood_max > n_max_cbs) {
rfcp = kmalloc(sizeof(*rfcp), GFP_KERNEL);
if (WARN_ON_ONCE(!rfcp)) {
schedule_timeout_interruptible(1);
@@ -1912,8 +2737,11 @@ static void rcu_torture_fwd_prog_cr(struct rcu_fwd *rfp)
n_launders_sa = 0;
rfcp->rfc_gps = 0;
rfcp->rfc_rfp = rfp;
+ } else {
+ rfcp = NULL;
}
- cur_ops->call(&rfcp->rh, rcu_torture_fwd_cb_cr);
+ if (rfcp)
+ cur_ops->call(&rfcp->rh, rcu_torture_fwd_cb_cr);
rcu_torture_fwd_prog_cond_resched(n_launders + n_max_cbs);
if (tick_nohz_full_enabled()) {
local_irq_save(flags);
@@ -1925,6 +2753,7 @@ static void rcu_torture_fwd_prog_cr(struct rcu_fwd *rfp)
n_launders_cb_snap = READ_ONCE(rfp->n_launders_cb);
cver = READ_ONCE(rcu_torture_current_version) - cver;
gps = rcutorture_seq_diff(cur_ops->get_gp_seq(), gps);
+ pr_alert("%s: Waiting for CBs: %pS() %d\n", __func__, cur_ops->cb_barrier, rfp->rcu_fwd_id);
cur_ops->cb_barrier(); /* Wait for callbacks to be invoked. */
(void)rcu_torture_fwd_prog_cbfree(rfp);
@@ -1937,11 +2766,14 @@ static void rcu_torture_fwd_prog_cr(struct rcu_fwd *rfp)
n_launders + n_max_cbs - n_launders_cb_snap,
n_launders, n_launders_sa,
n_max_gps, n_max_cbs, cver, gps);
+ atomic_long_add(n_max_cbs, &rcu_fwd_max_cbs);
+ mutex_lock(&rcu_fwd_mutex); // Serialize histograms.
rcu_torture_fwd_cb_hist(rfp);
+ mutex_unlock(&rcu_fwd_mutex);
}
schedule_timeout_uninterruptible(HZ); /* Let CBs drain. */
tick_dep_clear_task(current, TICK_DEP_BIT_RCU);
- WRITE_ONCE(rcu_fwd_cb_nodelay, false);
+ atomic_dec(&rcu_fwd_cb_nodelay);
}
@@ -1952,25 +2784,42 @@ static void rcu_torture_fwd_prog_cr(struct rcu_fwd *rfp)
static int rcutorture_oom_notify(struct notifier_block *self,
unsigned long notused, void *nfreed)
{
- struct rcu_fwd *rfp = rcu_fwds;
+ int i;
+ long ncbs;
+ struct rcu_fwd *rfp;
+ mutex_lock(&rcu_fwd_mutex);
+ rfp = rcu_fwds;
+ if (!rfp) {
+ mutex_unlock(&rcu_fwd_mutex);
+ return NOTIFY_OK;
+ }
WARN(1, "%s invoked upon OOM during forward-progress testing.\n",
__func__);
- rcu_torture_fwd_cb_hist(rfp);
- rcu_fwd_progress_check(1 + (jiffies - READ_ONCE(rfp->rcu_fwd_startat)) / 2);
+ for (i = 0; i < fwd_progress; i++) {
+ rcu_torture_fwd_cb_hist(&rfp[i]);
+ rcu_fwd_progress_check(1 + (jiffies - READ_ONCE(rfp[i].rcu_fwd_startat)) / 2);
+ }
WRITE_ONCE(rcu_fwd_emergency_stop, true);
smp_mb(); /* Emergency stop before free and wait to avoid hangs. */
- pr_info("%s: Freed %lu RCU callbacks.\n",
- __func__, rcu_torture_fwd_prog_cbfree(rfp));
- rcu_barrier();
- pr_info("%s: Freed %lu RCU callbacks.\n",
- __func__, rcu_torture_fwd_prog_cbfree(rfp));
- rcu_barrier();
- pr_info("%s: Freed %lu RCU callbacks.\n",
- __func__, rcu_torture_fwd_prog_cbfree(rfp));
+ ncbs = 0;
+ for (i = 0; i < fwd_progress; i++)
+ ncbs += rcu_torture_fwd_prog_cbfree(&rfp[i]);
+ pr_info("%s: Freed %lu RCU callbacks.\n", __func__, ncbs);
+ cur_ops->cb_barrier();
+ ncbs = 0;
+ for (i = 0; i < fwd_progress; i++)
+ ncbs += rcu_torture_fwd_prog_cbfree(&rfp[i]);
+ pr_info("%s: Freed %lu RCU callbacks.\n", __func__, ncbs);
+ cur_ops->cb_barrier();
+ ncbs = 0;
+ for (i = 0; i < fwd_progress; i++)
+ ncbs += rcu_torture_fwd_prog_cbfree(&rfp[i]);
+ pr_info("%s: Freed %lu RCU callbacks.\n", __func__, ncbs);
smp_mb(); /* Frees before return to avoid redoing OOM. */
(*(unsigned long *)nfreed)++; /* Forward progress CBs freed! */
pr_info("%s returning after OOM processing.\n", __func__);
+ mutex_unlock(&rcu_fwd_mutex);
return NOTIFY_OK;
}
@@ -1981,6 +2830,10 @@ static struct notifier_block rcutorture_oom_nb = {
/* Carry out grace-period forward-progress testing. */
static int rcu_torture_fwd_prog(void *args)
{
+ bool firsttime = true;
+ long max_cbs;
+ int oldnice = task_nice(current);
+ unsigned long oldseq = READ_ONCE(rcu_fwd_seq);
struct rcu_fwd *rfp = args;
int tested = 0;
int tested_tries = 0;
@@ -1990,19 +2843,38 @@ static int rcu_torture_fwd_prog(void *args)
if (!IS_ENABLED(CONFIG_SMP) || !IS_ENABLED(CONFIG_RCU_BOOST))
set_user_nice(current, MAX_NICE);
do {
- schedule_timeout_interruptible(fwd_progress_holdoff * HZ);
- WRITE_ONCE(rcu_fwd_emergency_stop, false);
- register_oom_notifier(&rcutorture_oom_nb);
- rcu_torture_fwd_prog_nr(rfp, &tested, &tested_tries);
- rcu_torture_fwd_prog_cr(rfp);
- unregister_oom_notifier(&rcutorture_oom_nb);
+ if (!rfp->rcu_fwd_id) {
+ schedule_timeout_interruptible(fwd_progress_holdoff * HZ);
+ WRITE_ONCE(rcu_fwd_emergency_stop, false);
+ if (!firsttime) {
+ max_cbs = atomic_long_xchg(&rcu_fwd_max_cbs, 0);
+ pr_alert("%s n_max_cbs: %ld\n", __func__, max_cbs);
+ }
+ firsttime = false;
+ WRITE_ONCE(rcu_fwd_seq, rcu_fwd_seq + 1);
+ } else {
+ while (READ_ONCE(rcu_fwd_seq) == oldseq && !torture_must_stop())
+ schedule_timeout_interruptible(1);
+ oldseq = READ_ONCE(rcu_fwd_seq);
+ }
+ pr_alert("%s: Starting forward-progress test %d\n", __func__, rfp->rcu_fwd_id);
+ if (rcu_inkernel_boot_has_ended() && torture_num_online_cpus() > rfp->rcu_fwd_id)
+ rcu_torture_fwd_prog_cr(rfp);
+ if ((cur_ops->stall_dur && cur_ops->stall_dur() > 0) &&
+ (!IS_ENABLED(CONFIG_TINY_RCU) ||
+ (rcu_inkernel_boot_has_ended() &&
+ torture_num_online_cpus() > rfp->rcu_fwd_id)))
+ rcu_torture_fwd_prog_nr(rfp, &tested, &tested_tries);
/* Avoid slow periods, better to test when busy. */
- stutter_wait("rcu_torture_fwd_prog");
+ if (stutter_wait("rcu_torture_fwd_prog"))
+ sched_set_normal(current, oldnice);
} while (!torture_must_stop());
/* Short runs might not contain a valid forward-progress attempt. */
- WARN_ON(!tested && tested_tries >= 5);
- pr_alert("%s: tested %d tested_tries %d\n", __func__, tested, tested_tries);
+ if (!rfp->rcu_fwd_id) {
+ WARN_ON(!tested && tested_tries >= 5);
+ pr_alert("%s: tested %d tested_tries %d\n", __func__, tested, tested_tries);
+ }
torture_kthread_stopping("rcu_torture_fwd_prog");
return 0;
}
@@ -2010,18 +2882,29 @@ static int rcu_torture_fwd_prog(void *args)
/* If forward-progress checking is requested and feasible, spawn the thread. */
static int __init rcu_torture_fwd_prog_init(void)
{
+ int i;
+ int ret = 0;
struct rcu_fwd *rfp;
if (!fwd_progress)
return 0; /* Not requested, so don't do it. */
- if (!cur_ops->stall_dur || cur_ops->stall_dur() <= 0 ||
+ if (fwd_progress >= nr_cpu_ids) {
+ VERBOSE_TOROUT_STRING("rcu_torture_fwd_prog_init: Limiting fwd_progress to # CPUs.\n");
+ fwd_progress = nr_cpu_ids;
+ } else if (fwd_progress < 0) {
+ fwd_progress = nr_cpu_ids;
+ }
+ if ((!cur_ops->sync && !cur_ops->call) ||
+ (!cur_ops->cbflood_max && (!cur_ops->stall_dur || cur_ops->stall_dur() <= 0)) ||
cur_ops == &rcu_busted_ops) {
VERBOSE_TOROUT_STRING("rcu_torture_fwd_prog_init: Disabled, unsupported by RCU flavor under test");
+ fwd_progress = 0;
return 0;
}
if (stall_cpu > 0) {
VERBOSE_TOROUT_STRING("rcu_torture_fwd_prog_init: Disabled, conflicts with CPU-stall testing");
- if (IS_MODULE(CONFIG_RCU_TORTURE_TESTS))
+ fwd_progress = 0;
+ if (IS_MODULE(CONFIG_RCU_TORTURE_TEST))
return -EINVAL; /* In module, can fail back to user. */
WARN_ON(1); /* Make sure rcutorture notices conflict. */
return 0;
@@ -2030,12 +2913,51 @@ static int __init rcu_torture_fwd_prog_init(void)
fwd_progress_holdoff = 1;
if (fwd_progress_div <= 0)
fwd_progress_div = 4;
- rfp = kzalloc(sizeof(*rfp), GFP_KERNEL);
- if (!rfp)
+ rfp = kcalloc(fwd_progress, sizeof(*rfp), GFP_KERNEL);
+ fwd_prog_tasks = kcalloc(fwd_progress, sizeof(*fwd_prog_tasks), GFP_KERNEL);
+ if (!rfp || !fwd_prog_tasks) {
+ kfree(rfp);
+ kfree(fwd_prog_tasks);
+ fwd_prog_tasks = NULL;
+ fwd_progress = 0;
return -ENOMEM;
- spin_lock_init(&rfp->rcu_fwd_lock);
- rfp->rcu_fwd_cb_tail = &rfp->rcu_fwd_cb_head;
- return torture_create_kthread(rcu_torture_fwd_prog, rfp, fwd_prog_task);
+ }
+ for (i = 0; i < fwd_progress; i++) {
+ spin_lock_init(&rfp[i].rcu_fwd_lock);
+ rfp[i].rcu_fwd_cb_tail = &rfp[i].rcu_fwd_cb_head;
+ rfp[i].rcu_fwd_id = i;
+ }
+ mutex_lock(&rcu_fwd_mutex);
+ rcu_fwds = rfp;
+ mutex_unlock(&rcu_fwd_mutex);
+ register_oom_notifier(&rcutorture_oom_nb);
+ for (i = 0; i < fwd_progress; i++) {
+ ret = torture_create_kthread(rcu_torture_fwd_prog, &rcu_fwds[i], fwd_prog_tasks[i]);
+ if (ret) {
+ fwd_progress = i;
+ return ret;
+ }
+ }
+ return 0;
+}
+
+static void rcu_torture_fwd_prog_cleanup(void)
+{
+ int i;
+ struct rcu_fwd *rfp;
+
+ if (!rcu_fwds || !fwd_prog_tasks)
+ return;
+ for (i = 0; i < fwd_progress; i++)
+ torture_stop_kthread(rcu_torture_fwd_prog, fwd_prog_tasks[i]);
+ unregister_oom_notifier(&rcutorture_oom_nb);
+ mutex_lock(&rcu_fwd_mutex);
+ rfp = rcu_fwds;
+ rcu_fwds = NULL;
+ mutex_unlock(&rcu_fwd_mutex);
+ kfree(rfp);
+ kfree(fwd_prog_tasks);
+ fwd_prog_tasks = NULL;
}
/* Callback function for RCU barrier testing. */
@@ -2044,11 +2966,19 @@ static void rcu_torture_barrier_cbf(struct rcu_head *rcu)
atomic_inc(&barrier_cbs_invoked);
}
+/* IPI handler to get callback posted on desired CPU, if online. */
+static void rcu_torture_barrier1cb(void *rcu_void)
+{
+ struct rcu_head *rhp = rcu_void;
+
+ cur_ops->call(rhp, rcu_torture_barrier_cbf);
+}
+
/* kthread function to register callbacks used to test RCU barriers. */
static int rcu_torture_barrier_cbs(void *arg)
{
long myid = (long)arg;
- bool lastphase = 0;
+ bool lastphase = false;
bool newphase;
struct rcu_head rcu;
@@ -2067,9 +2997,11 @@ static int rcu_torture_barrier_cbs(void *arg)
* The above smp_load_acquire() ensures barrier_phase load
* is ordered before the following ->call().
*/
- local_irq_disable(); /* Just to test no-irq call_rcu(). */
- cur_ops->call(&rcu, rcu_torture_barrier_cbf);
- local_irq_enable();
+ if (smp_call_function_single(myid, rcu_torture_barrier1cb,
+ &rcu, 1)) {
+ // IPI failed, so use direct call from current CPU.
+ cur_ops->call(&rcu, rcu_torture_barrier_cbf);
+ }
if (atomic_dec_and_test(&barrier_cbs_count))
wake_up(&barrier_wq);
} while (!torture_must_stop());
@@ -2105,7 +3037,21 @@ static int rcu_torture_barrier(void *arg)
pr_err("barrier_cbs_invoked = %d, n_barrier_cbs = %d\n",
atomic_read(&barrier_cbs_invoked),
n_barrier_cbs);
- WARN_ON_ONCE(1);
+ WARN_ON(1);
+ // Wait manually for the remaining callbacks
+ i = 0;
+ do {
+ if (WARN_ON(i++ > HZ))
+ i = INT_MIN;
+ schedule_timeout_interruptible(1);
+ cur_ops->cb_barrier();
+ } while (atomic_read(&barrier_cbs_invoked) !=
+ n_barrier_cbs &&
+ !torture_must_stop());
+ smp_mb(); // Can't trust ordering if broken.
+ if (!torture_must_stop())
+ pr_err("Recovered: barrier_cbs_invoked = %d\n",
+ atomic_read(&barrier_cbs_invoked));
} else {
n_barrier_successes++;
}
@@ -2178,13 +3124,15 @@ static bool rcu_torture_can_boost(void)
if (!(test_boost == 1 && cur_ops->can_boost) && test_boost != 2)
return false;
+ if (!cur_ops->start_gp_poll || !cur_ops->poll_gp_state)
+ return false;
prio = rcu_get_gp_kthreads_prio();
if (!prio)
return false;
if (prio < 2) {
- if (boost_warn_once == 1)
+ if (boost_warn_once == 1)
return false;
pr_alert("%s: WARN: RCU kthread priority too low to test boosting. Skipping RCU boost test. Try passing rcutree.kthread_prio > 1 on the kernel command line.\n", KBUILD_MODNAME);
@@ -2195,6 +3143,92 @@ static bool rcu_torture_can_boost(void)
return true;
}
+static bool read_exit_child_stop;
+static bool read_exit_child_stopped;
+static wait_queue_head_t read_exit_wq;
+
+// Child kthread which just does an rcutorture reader and exits.
+static int rcu_torture_read_exit_child(void *trsp_in)
+{
+ struct torture_random_state *trsp = trsp_in;
+
+ set_user_nice(current, MAX_NICE);
+ // Minimize time between reading and exiting.
+ while (!kthread_should_stop())
+ schedule_timeout_uninterruptible(1);
+ (void)rcu_torture_one_read(trsp, -1);
+ return 0;
+}
+
+// Parent kthread which creates and destroys read-exit child kthreads.
+static int rcu_torture_read_exit(void *unused)
+{
+ bool errexit = false;
+ int i;
+ struct task_struct *tsp;
+ DEFINE_TORTURE_RANDOM(trs);
+
+ // Allocate and initialize.
+ set_user_nice(current, MAX_NICE);
+ VERBOSE_TOROUT_STRING("rcu_torture_read_exit: Start of test");
+
+ // Each pass through this loop does one read-exit episode.
+ do {
+ VERBOSE_TOROUT_STRING("rcu_torture_read_exit: Start of episode");
+ for (i = 0; i < read_exit_burst; i++) {
+ if (READ_ONCE(read_exit_child_stop))
+ break;
+ stutter_wait("rcu_torture_read_exit");
+ // Spawn child.
+ tsp = kthread_run(rcu_torture_read_exit_child,
+ &trs, "%s", "rcu_torture_read_exit_child");
+ if (IS_ERR(tsp)) {
+ TOROUT_ERRSTRING("out of memory");
+ errexit = true;
+ break;
+ }
+ cond_resched();
+ kthread_stop(tsp);
+ n_read_exits++;
+ }
+ VERBOSE_TOROUT_STRING("rcu_torture_read_exit: End of episode");
+ rcu_barrier(); // Wait for task_struct free, avoid OOM.
+ i = 0;
+ for (; !errexit && !READ_ONCE(read_exit_child_stop) && i < read_exit_delay; i++)
+ schedule_timeout_uninterruptible(HZ);
+ } while (!errexit && !READ_ONCE(read_exit_child_stop));
+
+ // Clean up and exit.
+ smp_store_release(&read_exit_child_stopped, true); // After reaping.
+ smp_mb(); // Store before wakeup.
+ wake_up(&read_exit_wq);
+ while (!torture_must_stop())
+ schedule_timeout_uninterruptible(1);
+ torture_kthread_stopping("rcu_torture_read_exit");
+ return 0;
+}
+
+static int rcu_torture_read_exit_init(void)
+{
+ if (read_exit_burst <= 0)
+ return 0;
+ init_waitqueue_head(&read_exit_wq);
+ read_exit_child_stop = false;
+ read_exit_child_stopped = false;
+ return torture_create_kthread(rcu_torture_read_exit, NULL,
+ read_exit_task);
+}
+
+static void rcu_torture_read_exit_cleanup(void)
+{
+ if (!read_exit_task)
+ return;
+ WRITE_ONCE(read_exit_child_stop, true);
+ smp_mb(); // Above write before wait.
+ wait_event(read_exit_wq, smp_load_acquire(&read_exit_child_stopped));
+ torture_stop_kthread(rcutorture_read_exit, read_exit_task);
+}
+
static enum cpuhp_state rcutor_hp;
static void
@@ -2206,56 +3240,75 @@ rcu_torture_cleanup(void)
int i;
if (torture_cleanup_begin()) {
- if (cur_ops->cb_barrier != NULL)
+ if (cur_ops->cb_barrier != NULL) {
+ pr_info("%s: Invoking %pS().\n", __func__, cur_ops->cb_barrier);
cur_ops->cb_barrier();
+ }
+ rcu_gp_slow_unregister(NULL);
return;
}
if (!cur_ops) {
torture_cleanup_end();
+ rcu_gp_slow_unregister(NULL);
return;
}
- show_rcu_gp_kthreads();
+ if (cur_ops->gp_kthread_dbg)
+ cur_ops->gp_kthread_dbg();
+ rcu_torture_read_exit_cleanup();
rcu_torture_barrier_cleanup();
- torture_stop_kthread(rcu_torture_fwd_prog, fwd_prog_task);
+ rcu_torture_fwd_prog_cleanup();
torture_stop_kthread(rcu_torture_stall, stall_task);
torture_stop_kthread(rcu_torture_writer, writer_task);
+ if (nocb_tasks) {
+ for (i = 0; i < nrealnocbers; i++)
+ torture_stop_kthread(rcu_nocb_toggle, nocb_tasks[i]);
+ kfree(nocb_tasks);
+ nocb_tasks = NULL;
+ }
+
if (reader_tasks) {
for (i = 0; i < nrealreaders; i++)
torture_stop_kthread(rcu_torture_reader,
reader_tasks[i]);
kfree(reader_tasks);
+ reader_tasks = NULL;
}
- rcu_torture_current = NULL;
+ kfree(rcu_torture_reader_mbchk);
+ rcu_torture_reader_mbchk = NULL;
if (fakewriter_tasks) {
- for (i = 0; i < nfakewriters; i++) {
+ for (i = 0; i < nfakewriters; i++)
torture_stop_kthread(rcu_torture_fakewriter,
fakewriter_tasks[i]);
- }
kfree(fakewriter_tasks);
fakewriter_tasks = NULL;
}
rcutorture_get_gp_data(cur_ops->ttype, &flags, &gp_seq);
srcutorture_get_gp_data(cur_ops->ttype, srcu_ctlp, &flags, &gp_seq);
- pr_alert("%s: End-test grace-period state: g%lu f%#x\n",
- cur_ops->name, gp_seq, flags);
+ pr_alert("%s: End-test grace-period state: g%ld f%#x total-gps=%ld\n",
+ cur_ops->name, (long)gp_seq, flags,
+ rcutorture_seq_diff(gp_seq, start_gp_seq));
torture_stop_kthread(rcu_torture_stats, stats_task);
torture_stop_kthread(rcu_torture_fqs, fqs_task);
- if (rcu_torture_can_boost())
+ if (rcu_torture_can_boost() && rcutor_hp >= 0)
cpuhp_remove_state(rcutor_hp);
/*
* Wait for all RCU callbacks to fire, then do torture-type-specific
* cleanup operations.
*/
- if (cur_ops->cb_barrier != NULL)
+ if (cur_ops->cb_barrier != NULL) {
+ pr_info("%s: Invoking %pS().\n", __func__, cur_ops->cb_barrier);
cur_ops->cb_barrier();
+ }
if (cur_ops->cleanup != NULL)
cur_ops->cleanup();
+ rcu_torture_mem_dump_obj();
+
rcu_torture_stats_print(); /* -After- the stats thread is stopped! */
if (err_segs_recorded) {
@@ -2293,6 +3346,7 @@ rcu_torture_cleanup(void)
else
rcu_torture_print_module_parms(cur_ops, "End of test: SUCCESS");
torture_cleanup_end();
+ rcu_gp_slow_unregister(&rcu_fwd_cb_nodelay);
}
#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
@@ -2325,6 +3379,7 @@ static void rcu_test_debug_objects(void)
#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
struct rcu_head rh1;
struct rcu_head rh2;
+ struct rcu_head *rhp = kmalloc(sizeof(*rhp), GFP_KERNEL);
init_rcu_head_on_stack(&rh1);
init_rcu_head_on_stack(&rh2);
@@ -2337,6 +3392,10 @@ static void rcu_test_debug_objects(void)
local_irq_disable(); /* Make it harder to start a new grace period. */
call_rcu(&rh2, rcu_torture_leak_cb);
call_rcu(&rh2, rcu_torture_err_cb); /* Duplicate callback. */
+ if (rhp) {
+ call_rcu(rhp, rcu_torture_leak_cb);
+ call_rcu(rhp, rcu_torture_err_cb); /* Another duplicate callback. */
+ }
local_irq_enable();
rcu_read_unlock();
preempt_enable();
@@ -2346,6 +3405,7 @@ static void rcu_test_debug_objects(void)
pr_alert("%s: WARN: Duplicate call_rcu() test complete.\n", KBUILD_MODNAME);
destroy_rcu_head_on_stack(&rh1);
destroy_rcu_head_on_stack(&rh2);
+ kfree(rhp);
#else /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */
pr_alert("%s: !CONFIG_DEBUG_OBJECTS_RCU_HEAD, not testing duplicate call_rcu()\n", KBUILD_MODNAME);
#endif /* #else #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */
@@ -2365,9 +3425,12 @@ rcu_torture_init(void)
long i;
int cpu;
int firsterr = 0;
+ int flags = 0;
+ unsigned long gp_seq = 0;
static struct rcu_torture_ops *torture_ops[] = {
- &rcu_ops, &rcu_busted_ops, &srcu_ops, &srcud_ops,
- &busted_srcud_ops, &tasks_ops, &trivial_ops,
+ &rcu_ops, &rcu_busted_ops, &srcu_ops, &srcud_ops, &busted_srcud_ops,
+ TASKS_OPS TASKS_RUDE_OPS TASKS_TRACING_OPS
+ &trivial_ops,
};
if (!torture_init_begin(torture_type, verbose))
@@ -2386,7 +3449,6 @@ rcu_torture_init(void)
for (i = 0; i < ARRAY_SIZE(torture_ops); i++)
pr_cont(" %s", torture_ops[i]->name);
pr_cont("\n");
- WARN_ON(!IS_MODULE(CONFIG_RCU_TORTURE_TEST));
firsterr = -EINVAL;
cur_ops = NULL;
goto unwind;
@@ -2406,6 +3468,11 @@ rcu_torture_init(void)
nrealreaders = 1;
}
rcu_torture_print_module_parms(cur_ops, "Start of test");
+ rcutorture_get_gp_data(cur_ops->ttype, &flags, &gp_seq);
+ srcutorture_get_gp_data(cur_ops->ttype, srcu_ctlp, &flags, &gp_seq);
+ start_gp_seq = gp_seq;
+ pr_alert("%s: Start-test grace-period state: g%ld f%#x\n",
+ cur_ops->name, (long)gp_seq, flags);
/* Set up the freelist. */
@@ -2424,6 +3491,8 @@ rcu_torture_init(void)
atomic_set(&n_rcu_torture_alloc_fail, 0);
atomic_set(&n_rcu_torture_free, 0);
atomic_set(&n_rcu_torture_mberror, 0);
+ atomic_set(&n_rcu_torture_mbchk_fail, 0);
+ atomic_set(&n_rcu_torture_mbchk_tries, 0);
atomic_set(&n_rcu_torture_error, 0);
n_rcu_torture_barrier_error = 0;
n_rcu_torture_boost_ktrerror = 0;
@@ -2443,16 +3512,17 @@ rcu_torture_init(void)
/* Start up the kthreads. */
+ rcu_torture_write_types();
firsterr = torture_create_kthread(rcu_torture_writer, NULL,
writer_task);
- if (firsterr)
+ if (torture_init_error(firsterr))
goto unwind;
if (nfakewriters > 0) {
fakewriter_tasks = kcalloc(nfakewriters,
sizeof(fakewriter_tasks[0]),
GFP_KERNEL);
if (fakewriter_tasks == NULL) {
- VERBOSE_TOROUT_ERRSTRING("out of memory");
+ TOROUT_ERRSTRING("out of memory");
firsterr = -ENOMEM;
goto unwind;
}
@@ -2460,31 +3530,54 @@ rcu_torture_init(void)
for (i = 0; i < nfakewriters; i++) {
firsterr = torture_create_kthread(rcu_torture_fakewriter,
NULL, fakewriter_tasks[i]);
- if (firsterr)
+ if (torture_init_error(firsterr))
goto unwind;
}
reader_tasks = kcalloc(nrealreaders, sizeof(reader_tasks[0]),
GFP_KERNEL);
- if (reader_tasks == NULL) {
- VERBOSE_TOROUT_ERRSTRING("out of memory");
+ rcu_torture_reader_mbchk = kcalloc(nrealreaders, sizeof(*rcu_torture_reader_mbchk),
+ GFP_KERNEL);
+ if (!reader_tasks || !rcu_torture_reader_mbchk) {
+ TOROUT_ERRSTRING("out of memory");
firsterr = -ENOMEM;
goto unwind;
}
for (i = 0; i < nrealreaders; i++) {
+ rcu_torture_reader_mbchk[i].rtc_chkrdr = -1;
firsterr = torture_create_kthread(rcu_torture_reader, (void *)i,
reader_tasks[i]);
- if (firsterr)
+ if (torture_init_error(firsterr))
+ goto unwind;
+ }
+ nrealnocbers = nocbs_nthreads;
+ if (WARN_ON(nrealnocbers < 0))
+ nrealnocbers = 1;
+ if (WARN_ON(nocbs_toggle < 0))
+ nocbs_toggle = HZ;
+ if (nrealnocbers > 0) {
+ nocb_tasks = kcalloc(nrealnocbers, sizeof(nocb_tasks[0]), GFP_KERNEL);
+ if (nocb_tasks == NULL) {
+ TOROUT_ERRSTRING("out of memory");
+ firsterr = -ENOMEM;
+ goto unwind;
+ }
+ } else {
+ nocb_tasks = NULL;
+ }
+ for (i = 0; i < nrealnocbers; i++) {
+ firsterr = torture_create_kthread(rcu_nocb_toggle, NULL, nocb_tasks[i]);
+ if (torture_init_error(firsterr))
goto unwind;
}
if (stat_interval > 0) {
firsterr = torture_create_kthread(rcu_torture_stats, NULL,
stats_task);
- if (firsterr)
+ if (torture_init_error(firsterr))
goto unwind;
}
if (test_no_idle_hz && shuffle_interval > 0) {
firsterr = torture_shuffle_init(shuffle_interval * HZ);
- if (firsterr)
+ if (torture_init_error(firsterr))
goto unwind;
}
if (stutter < 0)
@@ -2494,7 +3587,7 @@ rcu_torture_init(void)
t = cur_ops->stall_dur ? cur_ops->stall_dur() : stutter * HZ;
firsterr = torture_stutter_init(stutter * HZ, t);
- if (firsterr)
+ if (torture_init_error(firsterr))
goto unwind;
}
if (fqs_duration < 0)
@@ -2503,7 +3596,7 @@ rcu_torture_init(void)
/* Create the fqs thread */
firsterr = torture_create_kthread(rcu_torture_fqs, NULL,
fqs_task);
- if (firsterr)
+ if (torture_init_error(firsterr))
goto unwind;
}
if (test_boost_interval < 1)
@@ -2517,35 +3610,43 @@ rcu_torture_init(void)
firsterr = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "RCU_TORTURE",
rcutorture_booster_init,
rcutorture_booster_cleanup);
- if (firsterr < 0)
- goto unwind;
rcutor_hp = firsterr;
+ if (torture_init_error(firsterr))
+ goto unwind;
}
shutdown_jiffies = jiffies + shutdown_secs * HZ;
firsterr = torture_shutdown_init(shutdown_secs, rcu_torture_cleanup);
- if (firsterr)
+ if (torture_init_error(firsterr))
goto unwind;
firsterr = torture_onoff_init(onoff_holdoff * HZ, onoff_interval,
rcutorture_sync);
- if (firsterr)
+ if (torture_init_error(firsterr))
goto unwind;
firsterr = rcu_torture_stall_init();
- if (firsterr)
+ if (torture_init_error(firsterr))
goto unwind;
firsterr = rcu_torture_fwd_prog_init();
- if (firsterr)
+ if (torture_init_error(firsterr))
goto unwind;
firsterr = rcu_torture_barrier_init();
- if (firsterr)
+ if (torture_init_error(firsterr))
+ goto unwind;
+ firsterr = rcu_torture_read_exit_init();
+ if (torture_init_error(firsterr))
goto unwind;
if (object_debug)
rcu_test_debug_objects();
torture_init_end();
+ rcu_gp_slow_register(&rcu_fwd_cb_nodelay);
return 0;
unwind:
torture_init_end();
rcu_torture_cleanup();
+ if (shutdown_secs) {
+ WARN_ON(!IS_MODULE(CONFIG_RCU_TORTURE_TEST));
+ kernel_power_off();
+ }
return firsterr;
}
diff --git a/kernel/rcu/refscale.c b/kernel/rcu/refscale.c
new file mode 100644
index 000000000000..435c884c02b5
--- /dev/null
+++ b/kernel/rcu/refscale.c
@@ -0,0 +1,898 @@
+// SPDX-License-Identifier: GPL-2.0+
+//
+// Scalability test comparing RCU vs other mechanisms
+// for acquiring references on objects.
+//
+// Copyright (C) Google, 2020.
+//
+// Author: Joel Fernandes <joel@joelfernandes.org>
+
+#define pr_fmt(fmt) fmt
+
+#include <linux/atomic.h>
+#include <linux/bitops.h>
+#include <linux/completion.h>
+#include <linux/cpu.h>
+#include <linux/delay.h>
+#include <linux/err.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/kthread.h>
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/notifier.h>
+#include <linux/percpu.h>
+#include <linux/rcupdate.h>
+#include <linux/rcupdate_trace.h>
+#include <linux/reboot.h>
+#include <linux/sched.h>
+#include <linux/spinlock.h>
+#include <linux/smp.h>
+#include <linux/stat.h>
+#include <linux/srcu.h>
+#include <linux/slab.h>
+#include <linux/torture.h>
+#include <linux/types.h>
+
+#include "rcu.h"
+
+#define SCALE_FLAG "-ref-scale: "
+
+#define SCALEOUT(s, x...) \
+ pr_alert("%s" SCALE_FLAG s, scale_type, ## x)
+
+#define VERBOSE_SCALEOUT(s, x...) \
+ do { \
+ if (verbose) \
+ pr_alert("%s" SCALE_FLAG s "\n", scale_type, ## x); \
+ } while (0)
+
+static atomic_t verbose_batch_ctr;
+
+#define VERBOSE_SCALEOUT_BATCH(s, x...) \
+do { \
+ if (verbose && \
+ (verbose_batched <= 0 || \
+ !(atomic_inc_return(&verbose_batch_ctr) % verbose_batched))) { \
+ schedule_timeout_uninterruptible(1); \
+ pr_alert("%s" SCALE_FLAG s "\n", scale_type, ## x); \
+ } \
+} while (0)
+
+#define SCALEOUT_ERRSTRING(s, x...) pr_alert("%s" SCALE_FLAG "!!! " s "\n", scale_type, ## x)
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Joel Fernandes (Google) <joel@joelfernandes.org>");
+
+static char *scale_type = "rcu";
+module_param(scale_type, charp, 0444);
+MODULE_PARM_DESC(scale_type, "Type of test (rcu, srcu, refcnt, rwsem, rwlock.");
+
+torture_param(int, verbose, 0, "Enable verbose debugging printk()s");
+torture_param(int, verbose_batched, 0, "Batch verbose debugging printk()s");
+
+// Wait until there are multiple CPUs before starting test.
+torture_param(int, holdoff, IS_BUILTIN(CONFIG_RCU_REF_SCALE_TEST) ? 10 : 0,
+ "Holdoff time before test start (s)");
+// Number of loops per experiment, all readers execute operations concurrently.
+torture_param(long, loops, 10000, "Number of loops per experiment.");
+// Number of readers, with -1 defaulting to about 75% of the CPUs.
+torture_param(int, nreaders, -1, "Number of readers, -1 for 75% of CPUs.");
+// Number of runs.
+torture_param(int, nruns, 30, "Number of experiments to run.");
+// Reader delay in nanoseconds, 0 for no delay.
+torture_param(int, readdelay, 0, "Read-side delay in nanoseconds.");
+
+#ifdef MODULE
+# define REFSCALE_SHUTDOWN 0
+#else
+# define REFSCALE_SHUTDOWN 1
+#endif
+
+torture_param(bool, shutdown, REFSCALE_SHUTDOWN,
+ "Shutdown at end of scalability tests.");
+
+struct reader_task {
+ struct task_struct *task;
+ int start_reader;
+ wait_queue_head_t wq;
+ u64 last_duration_ns;
+};
+
+static struct task_struct *shutdown_task;
+static wait_queue_head_t shutdown_wq;
+
+static struct task_struct *main_task;
+static wait_queue_head_t main_wq;
+static int shutdown_start;
+
+static struct reader_task *reader_tasks;
+
+// Number of readers that are part of the current experiment.
+static atomic_t nreaders_exp;
+
+// Use to wait for all threads to start.
+static atomic_t n_init;
+static atomic_t n_started;
+static atomic_t n_warmedup;
+static atomic_t n_cooleddown;
+
+// Track which experiment is currently running.
+static int exp_idx;
+
+// Operations vector for selecting different types of tests.
+struct ref_scale_ops {
+ void (*init)(void);
+ void (*cleanup)(void);
+ void (*readsection)(const int nloops);
+ void (*delaysection)(const int nloops, const int udl, const int ndl);
+ const char *name;
+};
+
+static struct ref_scale_ops *cur_ops;
+
+static void un_delay(const int udl, const int ndl)
+{
+ if (udl)
+ udelay(udl);
+ if (ndl)
+ ndelay(ndl);
+}
+
+static void ref_rcu_read_section(const int nloops)
+{
+ int i;
+
+ for (i = nloops; i >= 0; i--) {
+ rcu_read_lock();
+ rcu_read_unlock();
+ }
+}
+
+static void ref_rcu_delay_section(const int nloops, const int udl, const int ndl)
+{
+ int i;
+
+ for (i = nloops; i >= 0; i--) {
+ rcu_read_lock();
+ un_delay(udl, ndl);
+ rcu_read_unlock();
+ }
+}
+
+static void rcu_sync_scale_init(void)
+{
+}
+
+static struct ref_scale_ops rcu_ops = {
+ .init = rcu_sync_scale_init,
+ .readsection = ref_rcu_read_section,
+ .delaysection = ref_rcu_delay_section,
+ .name = "rcu"
+};
+
+// Definitions for SRCU ref scale testing.
+DEFINE_STATIC_SRCU(srcu_refctl_scale);
+static struct srcu_struct *srcu_ctlp = &srcu_refctl_scale;
+
+static void srcu_ref_scale_read_section(const int nloops)
+{
+ int i;
+ int idx;
+
+ for (i = nloops; i >= 0; i--) {
+ idx = srcu_read_lock(srcu_ctlp);
+ srcu_read_unlock(srcu_ctlp, idx);
+ }
+}
+
+static void srcu_ref_scale_delay_section(const int nloops, const int udl, const int ndl)
+{
+ int i;
+ int idx;
+
+ for (i = nloops; i >= 0; i--) {
+ idx = srcu_read_lock(srcu_ctlp);
+ un_delay(udl, ndl);
+ srcu_read_unlock(srcu_ctlp, idx);
+ }
+}
+
+static struct ref_scale_ops srcu_ops = {
+ .init = rcu_sync_scale_init,
+ .readsection = srcu_ref_scale_read_section,
+ .delaysection = srcu_ref_scale_delay_section,
+ .name = "srcu"
+};
+
+#ifdef CONFIG_TASKS_RCU
+
+// Definitions for RCU Tasks ref scale testing: Empty read markers.
+// These definitions also work for RCU Rude readers.
+static void rcu_tasks_ref_scale_read_section(const int nloops)
+{
+ int i;
+
+ for (i = nloops; i >= 0; i--)
+ continue;
+}
+
+static void rcu_tasks_ref_scale_delay_section(const int nloops, const int udl, const int ndl)
+{
+ int i;
+
+ for (i = nloops; i >= 0; i--)
+ un_delay(udl, ndl);
+}
+
+static struct ref_scale_ops rcu_tasks_ops = {
+ .init = rcu_sync_scale_init,
+ .readsection = rcu_tasks_ref_scale_read_section,
+ .delaysection = rcu_tasks_ref_scale_delay_section,
+ .name = "rcu-tasks"
+};
+
+#define RCU_TASKS_OPS &rcu_tasks_ops,
+
+#else // #ifdef CONFIG_TASKS_RCU
+
+#define RCU_TASKS_OPS
+
+#endif // #else // #ifdef CONFIG_TASKS_RCU
+
+#ifdef CONFIG_TASKS_TRACE_RCU
+
+// Definitions for RCU Tasks Trace ref scale testing.
+static void rcu_trace_ref_scale_read_section(const int nloops)
+{
+ int i;
+
+ for (i = nloops; i >= 0; i--) {
+ rcu_read_lock_trace();
+ rcu_read_unlock_trace();
+ }
+}
+
+static void rcu_trace_ref_scale_delay_section(const int nloops, const int udl, const int ndl)
+{
+ int i;
+
+ for (i = nloops; i >= 0; i--) {
+ rcu_read_lock_trace();
+ un_delay(udl, ndl);
+ rcu_read_unlock_trace();
+ }
+}
+
+static struct ref_scale_ops rcu_trace_ops = {
+ .init = rcu_sync_scale_init,
+ .readsection = rcu_trace_ref_scale_read_section,
+ .delaysection = rcu_trace_ref_scale_delay_section,
+ .name = "rcu-trace"
+};
+
+#define RCU_TRACE_OPS &rcu_trace_ops,
+
+#else // #ifdef CONFIG_TASKS_TRACE_RCU
+
+#define RCU_TRACE_OPS
+
+#endif // #else // #ifdef CONFIG_TASKS_TRACE_RCU
+
+// Definitions for reference count
+static atomic_t refcnt;
+
+static void ref_refcnt_section(const int nloops)
+{
+ int i;
+
+ for (i = nloops; i >= 0; i--) {
+ atomic_inc(&refcnt);
+ atomic_dec(&refcnt);
+ }
+}
+
+static void ref_refcnt_delay_section(const int nloops, const int udl, const int ndl)
+{
+ int i;
+
+ for (i = nloops; i >= 0; i--) {
+ atomic_inc(&refcnt);
+ un_delay(udl, ndl);
+ atomic_dec(&refcnt);
+ }
+}
+
+static struct ref_scale_ops refcnt_ops = {
+ .init = rcu_sync_scale_init,
+ .readsection = ref_refcnt_section,
+ .delaysection = ref_refcnt_delay_section,
+ .name = "refcnt"
+};
+
+// Definitions for rwlock
+static rwlock_t test_rwlock;
+
+static void ref_rwlock_init(void)
+{
+ rwlock_init(&test_rwlock);
+}
+
+static void ref_rwlock_section(const int nloops)
+{
+ int i;
+
+ for (i = nloops; i >= 0; i--) {
+ read_lock(&test_rwlock);
+ read_unlock(&test_rwlock);
+ }
+}
+
+static void ref_rwlock_delay_section(const int nloops, const int udl, const int ndl)
+{
+ int i;
+
+ for (i = nloops; i >= 0; i--) {
+ read_lock(&test_rwlock);
+ un_delay(udl, ndl);
+ read_unlock(&test_rwlock);
+ }
+}
+
+static struct ref_scale_ops rwlock_ops = {
+ .init = ref_rwlock_init,
+ .readsection = ref_rwlock_section,
+ .delaysection = ref_rwlock_delay_section,
+ .name = "rwlock"
+};
+
+// Definitions for rwsem
+static struct rw_semaphore test_rwsem;
+
+static void ref_rwsem_init(void)
+{
+ init_rwsem(&test_rwsem);
+}
+
+static void ref_rwsem_section(const int nloops)
+{
+ int i;
+
+ for (i = nloops; i >= 0; i--) {
+ down_read(&test_rwsem);
+ up_read(&test_rwsem);
+ }
+}
+
+static void ref_rwsem_delay_section(const int nloops, const int udl, const int ndl)
+{
+ int i;
+
+ for (i = nloops; i >= 0; i--) {
+ down_read(&test_rwsem);
+ un_delay(udl, ndl);
+ up_read(&test_rwsem);
+ }
+}
+
+static struct ref_scale_ops rwsem_ops = {
+ .init = ref_rwsem_init,
+ .readsection = ref_rwsem_section,
+ .delaysection = ref_rwsem_delay_section,
+ .name = "rwsem"
+};
+
+// Definitions for global spinlock
+static DEFINE_RAW_SPINLOCK(test_lock);
+
+static void ref_lock_section(const int nloops)
+{
+ int i;
+
+ preempt_disable();
+ for (i = nloops; i >= 0; i--) {
+ raw_spin_lock(&test_lock);
+ raw_spin_unlock(&test_lock);
+ }
+ preempt_enable();
+}
+
+static void ref_lock_delay_section(const int nloops, const int udl, const int ndl)
+{
+ int i;
+
+ preempt_disable();
+ for (i = nloops; i >= 0; i--) {
+ raw_spin_lock(&test_lock);
+ un_delay(udl, ndl);
+ raw_spin_unlock(&test_lock);
+ }
+ preempt_enable();
+}
+
+static struct ref_scale_ops lock_ops = {
+ .readsection = ref_lock_section,
+ .delaysection = ref_lock_delay_section,
+ .name = "lock"
+};
+
+// Definitions for global irq-save spinlock
+
+static void ref_lock_irq_section(const int nloops)
+{
+ unsigned long flags;
+ int i;
+
+ preempt_disable();
+ for (i = nloops; i >= 0; i--) {
+ raw_spin_lock_irqsave(&test_lock, flags);
+ raw_spin_unlock_irqrestore(&test_lock, flags);
+ }
+ preempt_enable();
+}
+
+static void ref_lock_irq_delay_section(const int nloops, const int udl, const int ndl)
+{
+ unsigned long flags;
+ int i;
+
+ preempt_disable();
+ for (i = nloops; i >= 0; i--) {
+ raw_spin_lock_irqsave(&test_lock, flags);
+ un_delay(udl, ndl);
+ raw_spin_unlock_irqrestore(&test_lock, flags);
+ }
+ preempt_enable();
+}
+
+static struct ref_scale_ops lock_irq_ops = {
+ .readsection = ref_lock_irq_section,
+ .delaysection = ref_lock_irq_delay_section,
+ .name = "lock-irq"
+};
+
+// Definitions acquire-release.
+static DEFINE_PER_CPU(unsigned long, test_acqrel);
+
+static void ref_acqrel_section(const int nloops)
+{
+ unsigned long x;
+ int i;
+
+ preempt_disable();
+ for (i = nloops; i >= 0; i--) {
+ x = smp_load_acquire(this_cpu_ptr(&test_acqrel));
+ smp_store_release(this_cpu_ptr(&test_acqrel), x + 1);
+ }
+ preempt_enable();
+}
+
+static void ref_acqrel_delay_section(const int nloops, const int udl, const int ndl)
+{
+ unsigned long x;
+ int i;
+
+ preempt_disable();
+ for (i = nloops; i >= 0; i--) {
+ x = smp_load_acquire(this_cpu_ptr(&test_acqrel));
+ un_delay(udl, ndl);
+ smp_store_release(this_cpu_ptr(&test_acqrel), x + 1);
+ }
+ preempt_enable();
+}
+
+static struct ref_scale_ops acqrel_ops = {
+ .readsection = ref_acqrel_section,
+ .delaysection = ref_acqrel_delay_section,
+ .name = "acqrel"
+};
+
+static volatile u64 stopopts;
+
+static void ref_clock_section(const int nloops)
+{
+ u64 x = 0;
+ int i;
+
+ preempt_disable();
+ for (i = nloops; i >= 0; i--)
+ x += ktime_get_real_fast_ns();
+ preempt_enable();
+ stopopts = x;
+}
+
+static void ref_clock_delay_section(const int nloops, const int udl, const int ndl)
+{
+ u64 x = 0;
+ int i;
+
+ preempt_disable();
+ for (i = nloops; i >= 0; i--) {
+ x += ktime_get_real_fast_ns();
+ un_delay(udl, ndl);
+ }
+ preempt_enable();
+ stopopts = x;
+}
+
+static struct ref_scale_ops clock_ops = {
+ .readsection = ref_clock_section,
+ .delaysection = ref_clock_delay_section,
+ .name = "clock"
+};
+
+static void rcu_scale_one_reader(void)
+{
+ if (readdelay <= 0)
+ cur_ops->readsection(loops);
+ else
+ cur_ops->delaysection(loops, readdelay / 1000, readdelay % 1000);
+}
+
+// Reader kthread. Repeatedly does empty RCU read-side
+// critical section, minimizing update-side interference.
+static int
+ref_scale_reader(void *arg)
+{
+ unsigned long flags;
+ long me = (long)arg;
+ struct reader_task *rt = &(reader_tasks[me]);
+ u64 start;
+ s64 duration;
+
+ VERBOSE_SCALEOUT_BATCH("ref_scale_reader %ld: task started", me);
+ WARN_ON_ONCE(set_cpus_allowed_ptr(current, cpumask_of(me % nr_cpu_ids)));
+ set_user_nice(current, MAX_NICE);
+ atomic_inc(&n_init);
+ if (holdoff)
+ schedule_timeout_interruptible(holdoff * HZ);
+repeat:
+ VERBOSE_SCALEOUT_BATCH("ref_scale_reader %ld: waiting to start next experiment on cpu %d", me, raw_smp_processor_id());
+
+ // Wait for signal that this reader can start.
+ wait_event(rt->wq, (atomic_read(&nreaders_exp) && smp_load_acquire(&rt->start_reader)) ||
+ torture_must_stop());
+
+ if (torture_must_stop())
+ goto end;
+
+ // Make sure that the CPU is affinitized appropriately during testing.
+ WARN_ON_ONCE(raw_smp_processor_id() != me);
+
+ WRITE_ONCE(rt->start_reader, 0);
+ if (!atomic_dec_return(&n_started))
+ while (atomic_read_acquire(&n_started))
+ cpu_relax();
+
+ VERBOSE_SCALEOUT_BATCH("ref_scale_reader %ld: experiment %d started", me, exp_idx);
+
+
+ // To reduce noise, do an initial cache-warming invocation, check
+ // in, and then keep warming until everyone has checked in.
+ rcu_scale_one_reader();
+ if (!atomic_dec_return(&n_warmedup))
+ while (atomic_read_acquire(&n_warmedup))
+ rcu_scale_one_reader();
+ // Also keep interrupts disabled. This also has the effect
+ // of preventing entries into slow path for rcu_read_unlock().
+ local_irq_save(flags);
+ start = ktime_get_mono_fast_ns();
+
+ rcu_scale_one_reader();
+
+ duration = ktime_get_mono_fast_ns() - start;
+ local_irq_restore(flags);
+
+ rt->last_duration_ns = WARN_ON_ONCE(duration < 0) ? 0 : duration;
+ // To reduce runtime-skew noise, do maintain-load invocations until
+ // everyone is done.
+ if (!atomic_dec_return(&n_cooleddown))
+ while (atomic_read_acquire(&n_cooleddown))
+ rcu_scale_one_reader();
+
+ if (atomic_dec_and_test(&nreaders_exp))
+ wake_up(&main_wq);
+
+ VERBOSE_SCALEOUT_BATCH("ref_scale_reader %ld: experiment %d ended, (readers remaining=%d)",
+ me, exp_idx, atomic_read(&nreaders_exp));
+
+ if (!torture_must_stop())
+ goto repeat;
+end:
+ torture_kthread_stopping("ref_scale_reader");
+ return 0;
+}
+
+static void reset_readers(void)
+{
+ int i;
+ struct reader_task *rt;
+
+ for (i = 0; i < nreaders; i++) {
+ rt = &(reader_tasks[i]);
+
+ rt->last_duration_ns = 0;
+ }
+}
+
+// Print the results of each reader and return the sum of all their durations.
+static u64 process_durations(int n)
+{
+ int i;
+ struct reader_task *rt;
+ char buf1[64];
+ char *buf;
+ u64 sum = 0;
+
+ buf = kmalloc(800 + 64, GFP_KERNEL);
+ if (!buf)
+ return 0;
+ buf[0] = 0;
+ sprintf(buf, "Experiment #%d (Format: <THREAD-NUM>:<Total loop time in ns>)",
+ exp_idx);
+
+ for (i = 0; i < n && !torture_must_stop(); i++) {
+ rt = &(reader_tasks[i]);
+ sprintf(buf1, "%d: %llu\t", i, rt->last_duration_ns);
+
+ if (i % 5 == 0)
+ strcat(buf, "\n");
+ if (strlen(buf) >= 800) {
+ pr_alert("%s", buf);
+ buf[0] = 0;
+ }
+ strcat(buf, buf1);
+
+ sum += rt->last_duration_ns;
+ }
+ pr_alert("%s\n", buf);
+
+ kfree(buf);
+ return sum;
+}
+
+// The main_func is the main orchestrator, it performs a bunch of
+// experiments. For every experiment, it orders all the readers
+// involved to start and waits for them to finish the experiment. It
+// then reads their timestamps and starts the next experiment. Each
+// experiment progresses from 1 concurrent reader to N of them at which
+// point all the timestamps are printed.
+static int main_func(void *arg)
+{
+ int exp, r;
+ char buf1[64];
+ char *buf;
+ u64 *result_avg;
+
+ set_cpus_allowed_ptr(current, cpumask_of(nreaders % nr_cpu_ids));
+ set_user_nice(current, MAX_NICE);
+
+ VERBOSE_SCALEOUT("main_func task started");
+ result_avg = kzalloc(nruns * sizeof(*result_avg), GFP_KERNEL);
+ buf = kzalloc(800 + 64, GFP_KERNEL);
+ if (!result_avg || !buf) {
+ SCALEOUT_ERRSTRING("out of memory");
+ goto oom_exit;
+ }
+ if (holdoff)
+ schedule_timeout_interruptible(holdoff * HZ);
+
+ // Wait for all threads to start.
+ atomic_inc(&n_init);
+ while (atomic_read(&n_init) < nreaders + 1)
+ schedule_timeout_uninterruptible(1);
+
+ // Start exp readers up per experiment
+ for (exp = 0; exp < nruns && !torture_must_stop(); exp++) {
+ if (torture_must_stop())
+ goto end;
+
+ reset_readers();
+ atomic_set(&nreaders_exp, nreaders);
+ atomic_set(&n_started, nreaders);
+ atomic_set(&n_warmedup, nreaders);
+ atomic_set(&n_cooleddown, nreaders);
+
+ exp_idx = exp;
+
+ for (r = 0; r < nreaders; r++) {
+ smp_store_release(&reader_tasks[r].start_reader, 1);
+ wake_up(&reader_tasks[r].wq);
+ }
+
+ VERBOSE_SCALEOUT("main_func: experiment started, waiting for %d readers",
+ nreaders);
+
+ wait_event(main_wq,
+ !atomic_read(&nreaders_exp) || torture_must_stop());
+
+ VERBOSE_SCALEOUT("main_func: experiment ended");
+
+ if (torture_must_stop())
+ goto end;
+
+ result_avg[exp] = div_u64(1000 * process_durations(nreaders), nreaders * loops);
+ }
+
+ // Print the average of all experiments
+ SCALEOUT("END OF TEST. Calculating average duration per loop (nanoseconds)...\n");
+
+ pr_alert("Runs\tTime(ns)\n");
+ for (exp = 0; exp < nruns; exp++) {
+ u64 avg;
+ u32 rem;
+
+ avg = div_u64_rem(result_avg[exp], 1000, &rem);
+ sprintf(buf1, "%d\t%llu.%03u\n", exp + 1, avg, rem);
+ strcat(buf, buf1);
+ if (strlen(buf) >= 800) {
+ pr_alert("%s", buf);
+ buf[0] = 0;
+ }
+ }
+
+ pr_alert("%s", buf);
+
+oom_exit:
+ // This will shutdown everything including us.
+ if (shutdown) {
+ shutdown_start = 1;
+ wake_up(&shutdown_wq);
+ }
+
+ // Wait for torture to stop us
+ while (!torture_must_stop())
+ schedule_timeout_uninterruptible(1);
+
+end:
+ torture_kthread_stopping("main_func");
+ kfree(result_avg);
+ kfree(buf);
+ return 0;
+}
+
+static void
+ref_scale_print_module_parms(struct ref_scale_ops *cur_ops, const char *tag)
+{
+ pr_alert("%s" SCALE_FLAG
+ "--- %s: verbose=%d shutdown=%d holdoff=%d loops=%ld nreaders=%d nruns=%d readdelay=%d\n", scale_type, tag,
+ verbose, shutdown, holdoff, loops, nreaders, nruns, readdelay);
+}
+
+static void
+ref_scale_cleanup(void)
+{
+ int i;
+
+ if (torture_cleanup_begin())
+ return;
+
+ if (!cur_ops) {
+ torture_cleanup_end();
+ return;
+ }
+
+ if (reader_tasks) {
+ for (i = 0; i < nreaders; i++)
+ torture_stop_kthread("ref_scale_reader",
+ reader_tasks[i].task);
+ }
+ kfree(reader_tasks);
+
+ torture_stop_kthread("main_task", main_task);
+ kfree(main_task);
+
+ // Do scale-type-specific cleanup operations.
+ if (cur_ops->cleanup != NULL)
+ cur_ops->cleanup();
+
+ torture_cleanup_end();
+}
+
+// Shutdown kthread. Just waits to be awakened, then shuts down system.
+static int
+ref_scale_shutdown(void *arg)
+{
+ wait_event(shutdown_wq, shutdown_start);
+
+ smp_mb(); // Wake before output.
+ ref_scale_cleanup();
+ kernel_power_off();
+
+ return -EINVAL;
+}
+
+static int __init
+ref_scale_init(void)
+{
+ long i;
+ int firsterr = 0;
+ static struct ref_scale_ops *scale_ops[] = {
+ &rcu_ops, &srcu_ops, RCU_TRACE_OPS RCU_TASKS_OPS &refcnt_ops, &rwlock_ops,
+ &rwsem_ops, &lock_ops, &lock_irq_ops, &acqrel_ops, &clock_ops,
+ };
+
+ if (!torture_init_begin(scale_type, verbose))
+ return -EBUSY;
+
+ for (i = 0; i < ARRAY_SIZE(scale_ops); i++) {
+ cur_ops = scale_ops[i];
+ if (strcmp(scale_type, cur_ops->name) == 0)
+ break;
+ }
+ if (i == ARRAY_SIZE(scale_ops)) {
+ pr_alert("rcu-scale: invalid scale type: \"%s\"\n", scale_type);
+ pr_alert("rcu-scale types:");
+ for (i = 0; i < ARRAY_SIZE(scale_ops); i++)
+ pr_cont(" %s", scale_ops[i]->name);
+ pr_cont("\n");
+ firsterr = -EINVAL;
+ cur_ops = NULL;
+ goto unwind;
+ }
+ if (cur_ops->init)
+ cur_ops->init();
+
+ ref_scale_print_module_parms(cur_ops, "Start of test");
+
+ // Shutdown task
+ if (shutdown) {
+ init_waitqueue_head(&shutdown_wq);
+ firsterr = torture_create_kthread(ref_scale_shutdown, NULL,
+ shutdown_task);
+ if (torture_init_error(firsterr))
+ goto unwind;
+ schedule_timeout_uninterruptible(1);
+ }
+
+ // Reader tasks (default to ~75% of online CPUs).
+ if (nreaders < 0)
+ nreaders = (num_online_cpus() >> 1) + (num_online_cpus() >> 2);
+ if (WARN_ONCE(loops <= 0, "%s: loops = %ld, adjusted to 1\n", __func__, loops))
+ loops = 1;
+ if (WARN_ONCE(nreaders <= 0, "%s: nreaders = %d, adjusted to 1\n", __func__, nreaders))
+ nreaders = 1;
+ if (WARN_ONCE(nruns <= 0, "%s: nruns = %d, adjusted to 1\n", __func__, nruns))
+ nruns = 1;
+ reader_tasks = kcalloc(nreaders, sizeof(reader_tasks[0]),
+ GFP_KERNEL);
+ if (!reader_tasks) {
+ SCALEOUT_ERRSTRING("out of memory");
+ firsterr = -ENOMEM;
+ goto unwind;
+ }
+
+ VERBOSE_SCALEOUT("Starting %d reader threads", nreaders);
+
+ for (i = 0; i < nreaders; i++) {
+ firsterr = torture_create_kthread(ref_scale_reader, (void *)i,
+ reader_tasks[i].task);
+ if (torture_init_error(firsterr))
+ goto unwind;
+
+ init_waitqueue_head(&(reader_tasks[i].wq));
+ }
+
+ // Main Task
+ init_waitqueue_head(&main_wq);
+ firsterr = torture_create_kthread(main_func, NULL, main_task);
+ if (torture_init_error(firsterr))
+ goto unwind;
+
+ torture_init_end();
+ return 0;
+
+unwind:
+ torture_init_end();
+ ref_scale_cleanup();
+ if (shutdown) {
+ WARN_ON(!IS_MODULE(CONFIG_RCU_REF_SCALE_TEST));
+ kernel_power_off();
+ }
+ return firsterr;
+}
+
+module_init(ref_scale_init);
+module_exit(ref_scale_cleanup);
diff --git a/kernel/rcu/srcutiny.c b/kernel/rcu/srcutiny.c
index 6208c1dae5c9..33adafdad261 100644
--- a/kernel/rcu/srcutiny.c
+++ b/kernel/rcu/srcutiny.c
@@ -34,6 +34,7 @@ static int init_srcu_struct_fields(struct srcu_struct *ssp)
ssp->srcu_gp_running = false;
ssp->srcu_gp_waiting = false;
ssp->srcu_idx = 0;
+ ssp->srcu_idx_max = 0;
INIT_WORK(&ssp->srcu_work, srcu_drive_gp);
INIT_LIST_HEAD(&ssp->srcu_work.entry);
return 0;
@@ -84,6 +85,8 @@ void cleanup_srcu_struct(struct srcu_struct *ssp)
WARN_ON(ssp->srcu_gp_waiting);
WARN_ON(ssp->srcu_cb_head);
WARN_ON(&ssp->srcu_cb_head != ssp->srcu_cb_tail);
+ WARN_ON(ssp->srcu_idx != ssp->srcu_idx_max);
+ WARN_ON(ssp->srcu_idx & 0x1);
}
EXPORT_SYMBOL_GPL(cleanup_srcu_struct);
@@ -93,10 +96,10 @@ EXPORT_SYMBOL_GPL(cleanup_srcu_struct);
*/
void __srcu_read_unlock(struct srcu_struct *ssp, int idx)
{
- int newval = ssp->srcu_lock_nesting[idx] - 1;
+ int newval = READ_ONCE(ssp->srcu_lock_nesting[idx]) - 1;
WRITE_ONCE(ssp->srcu_lock_nesting[idx], newval);
- if (!newval && READ_ONCE(ssp->srcu_gp_waiting))
+ if (!newval && READ_ONCE(ssp->srcu_gp_waiting) && in_task())
swake_up_one(&ssp->srcu_wq);
}
EXPORT_SYMBOL_GPL(__srcu_read_unlock);
@@ -114,7 +117,7 @@ void srcu_drive_gp(struct work_struct *wp)
struct srcu_struct *ssp;
ssp = container_of(wp, struct srcu_struct, srcu_work);
- if (ssp->srcu_gp_running || !READ_ONCE(ssp->srcu_cb_head))
+ if (ssp->srcu_gp_running || ULONG_CMP_GE(ssp->srcu_idx, READ_ONCE(ssp->srcu_idx_max)))
return; /* Already running or nothing to do. */
/* Remove recently arrived callbacks and wait for readers. */
@@ -124,11 +127,12 @@ void srcu_drive_gp(struct work_struct *wp)
ssp->srcu_cb_head = NULL;
ssp->srcu_cb_tail = &ssp->srcu_cb_head;
local_irq_enable();
- idx = ssp->srcu_idx;
- WRITE_ONCE(ssp->srcu_idx, !ssp->srcu_idx);
+ idx = (ssp->srcu_idx & 0x2) / 2;
+ WRITE_ONCE(ssp->srcu_idx, ssp->srcu_idx + 1);
WRITE_ONCE(ssp->srcu_gp_waiting, true); /* srcu_read_unlock() wakes! */
swait_event_exclusive(ssp->srcu_wq, !READ_ONCE(ssp->srcu_lock_nesting[idx]));
WRITE_ONCE(ssp->srcu_gp_waiting, false); /* srcu_read_unlock() cheap. */
+ WRITE_ONCE(ssp->srcu_idx, ssp->srcu_idx + 1);
/* Invoke the callbacks we removed above. */
while (lh) {
@@ -146,11 +150,27 @@ void srcu_drive_gp(struct work_struct *wp)
* straighten that out.
*/
WRITE_ONCE(ssp->srcu_gp_running, false);
- if (READ_ONCE(ssp->srcu_cb_head))
+ if (ULONG_CMP_LT(ssp->srcu_idx, READ_ONCE(ssp->srcu_idx_max)))
schedule_work(&ssp->srcu_work);
}
EXPORT_SYMBOL_GPL(srcu_drive_gp);
+static void srcu_gp_start_if_needed(struct srcu_struct *ssp)
+{
+ unsigned long cookie;
+
+ cookie = get_state_synchronize_srcu(ssp);
+ if (ULONG_CMP_GE(READ_ONCE(ssp->srcu_idx_max), cookie))
+ return;
+ WRITE_ONCE(ssp->srcu_idx_max, cookie);
+ if (!READ_ONCE(ssp->srcu_gp_running)) {
+ if (likely(srcu_init_done))
+ schedule_work(&ssp->srcu_work);
+ else if (list_empty(&ssp->srcu_work.entry))
+ list_add(&ssp->srcu_work.entry, &srcu_boot_list);
+ }
+}
+
/*
* Enqueue an SRCU callback on the specified srcu_struct structure,
* initiating grace-period processing if it is not already running.
@@ -166,12 +186,7 @@ void call_srcu(struct srcu_struct *ssp, struct rcu_head *rhp,
*ssp->srcu_cb_tail = rhp;
ssp->srcu_cb_tail = &rhp->next;
local_irq_restore(flags);
- if (!READ_ONCE(ssp->srcu_gp_running)) {
- if (likely(srcu_init_done))
- schedule_work(&ssp->srcu_work);
- else if (list_empty(&ssp->srcu_work.entry))
- list_add(&ssp->srcu_work.entry, &srcu_boot_list);
- }
+ srcu_gp_start_if_needed(ssp);
}
EXPORT_SYMBOL_GPL(call_srcu);
@@ -190,6 +205,48 @@ void synchronize_srcu(struct srcu_struct *ssp)
}
EXPORT_SYMBOL_GPL(synchronize_srcu);
+/*
+ * get_state_synchronize_srcu - Provide an end-of-grace-period cookie
+ */
+unsigned long get_state_synchronize_srcu(struct srcu_struct *ssp)
+{
+ unsigned long ret;
+
+ barrier();
+ ret = (READ_ONCE(ssp->srcu_idx) + 3) & ~0x1;
+ barrier();
+ return ret;
+}
+EXPORT_SYMBOL_GPL(get_state_synchronize_srcu);
+
+/*
+ * start_poll_synchronize_srcu - Provide cookie and start grace period
+ *
+ * The difference between this and get_state_synchronize_srcu() is that
+ * this function ensures that the poll_state_synchronize_srcu() will
+ * eventually return the value true.
+ */
+unsigned long start_poll_synchronize_srcu(struct srcu_struct *ssp)
+{
+ unsigned long ret = get_state_synchronize_srcu(ssp);
+
+ srcu_gp_start_if_needed(ssp);
+ return ret;
+}
+EXPORT_SYMBOL_GPL(start_poll_synchronize_srcu);
+
+/*
+ * poll_state_synchronize_srcu - Has cookie's grace period ended?
+ */
+bool poll_state_synchronize_srcu(struct srcu_struct *ssp, unsigned long cookie)
+{
+ unsigned long cur_s = READ_ONCE(ssp->srcu_idx);
+
+ barrier();
+ return ULONG_CMP_GE(cur_s, cookie) || ULONG_CMP_LT(cur_s, cookie - 3);
+}
+EXPORT_SYMBOL_GPL(poll_state_synchronize_srcu);
+
/* Lockdep diagnostics. */
void __init rcu_scheduler_starting(void)
{
diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
index 657e6a7d1c03..1c304fec89c0 100644
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -5,7 +5,7 @@
* Copyright (C) IBM Corporation, 2006
* Copyright (C) Fujitsu, 2012
*
- * Author: Paul McKenney <paulmck@linux.ibm.com>
+ * Authors: Paul McKenney <paulmck@linux.ibm.com>
* Lai Jiangshan <laijs@cn.fujitsu.com>
*
* For detailed explanation of Read-Copy Update mechanism see -
@@ -24,6 +24,7 @@
#include <linux/smp.h>
#include <linux/delay.h>
#include <linux/module.h>
+#include <linux/slab.h>
#include <linux/srcu.h>
#include "rcu.h"
@@ -38,6 +39,35 @@ module_param(exp_holdoff, ulong, 0444);
static ulong counter_wrap_check = (ULONG_MAX >> 2);
module_param(counter_wrap_check, ulong, 0444);
+/*
+ * Control conversion to SRCU_SIZE_BIG:
+ * 0: Don't convert at all.
+ * 1: Convert at init_srcu_struct() time.
+ * 2: Convert when rcutorture invokes srcu_torture_stats_print().
+ * 3: Decide at boot time based on system shape (default).
+ * 0x1x: Convert when excessive contention encountered.
+ */
+#define SRCU_SIZING_NONE 0
+#define SRCU_SIZING_INIT 1
+#define SRCU_SIZING_TORTURE 2
+#define SRCU_SIZING_AUTO 3
+#define SRCU_SIZING_CONTEND 0x10
+#define SRCU_SIZING_IS(x) ((convert_to_big & ~SRCU_SIZING_CONTEND) == x)
+#define SRCU_SIZING_IS_NONE() (SRCU_SIZING_IS(SRCU_SIZING_NONE))
+#define SRCU_SIZING_IS_INIT() (SRCU_SIZING_IS(SRCU_SIZING_INIT))
+#define SRCU_SIZING_IS_TORTURE() (SRCU_SIZING_IS(SRCU_SIZING_TORTURE))
+#define SRCU_SIZING_IS_CONTEND() (convert_to_big & SRCU_SIZING_CONTEND)
+static int convert_to_big = SRCU_SIZING_AUTO;
+module_param(convert_to_big, int, 0444);
+
+/* Number of CPUs to trigger init_srcu_struct()-time transition to big. */
+static int big_cpu_lim __read_mostly = 128;
+module_param(big_cpu_lim, int, 0444);
+
+/* Contention events per jiffy to initiate transition to big. */
+static int small_contention_lim __read_mostly = 100;
+module_param(small_contention_lim, int, 0444);
+
/* Early-boot callback-management, so early that no lock is required! */
static LIST_HEAD(srcu_boot_list);
static bool __read_mostly srcu_init_done;
@@ -48,39 +78,90 @@ static void process_srcu(struct work_struct *work);
static void srcu_delay_timer(struct timer_list *t);
/* Wrappers for lock acquisition and release, see raw_spin_lock_rcu_node(). */
-#define spin_lock_rcu_node(p) \
-do { \
- spin_lock(&ACCESS_PRIVATE(p, lock)); \
- smp_mb__after_unlock_lock(); \
+#define spin_lock_rcu_node(p) \
+do { \
+ spin_lock(&ACCESS_PRIVATE(p, lock)); \
+ smp_mb__after_unlock_lock(); \
} while (0)
#define spin_unlock_rcu_node(p) spin_unlock(&ACCESS_PRIVATE(p, lock))
-#define spin_lock_irq_rcu_node(p) \
-do { \
- spin_lock_irq(&ACCESS_PRIVATE(p, lock)); \
- smp_mb__after_unlock_lock(); \
+#define spin_lock_irq_rcu_node(p) \
+do { \
+ spin_lock_irq(&ACCESS_PRIVATE(p, lock)); \
+ smp_mb__after_unlock_lock(); \
} while (0)
-#define spin_unlock_irq_rcu_node(p) \
+#define spin_unlock_irq_rcu_node(p) \
spin_unlock_irq(&ACCESS_PRIVATE(p, lock))
-#define spin_lock_irqsave_rcu_node(p, flags) \
-do { \
- spin_lock_irqsave(&ACCESS_PRIVATE(p, lock), flags); \
- smp_mb__after_unlock_lock(); \
+#define spin_lock_irqsave_rcu_node(p, flags) \
+do { \
+ spin_lock_irqsave(&ACCESS_PRIVATE(p, lock), flags); \
+ smp_mb__after_unlock_lock(); \
} while (0)
-#define spin_unlock_irqrestore_rcu_node(p, flags) \
- spin_unlock_irqrestore(&ACCESS_PRIVATE(p, lock), flags) \
+#define spin_trylock_irqsave_rcu_node(p, flags) \
+({ \
+ bool ___locked = spin_trylock_irqsave(&ACCESS_PRIVATE(p, lock), flags); \
+ \
+ if (___locked) \
+ smp_mb__after_unlock_lock(); \
+ ___locked; \
+})
+
+#define spin_unlock_irqrestore_rcu_node(p, flags) \
+ spin_unlock_irqrestore(&ACCESS_PRIVATE(p, lock), flags) \
/*
- * Initialize SRCU combining tree. Note that statically allocated
+ * Initialize SRCU per-CPU data. Note that statically allocated
* srcu_struct structures might already have srcu_read_lock() and
* srcu_read_unlock() running against them. So if the is_static parameter
* is set, don't initialize ->srcu_lock_count[] and ->srcu_unlock_count[].
*/
-static void init_srcu_struct_nodes(struct srcu_struct *ssp, bool is_static)
+static void init_srcu_struct_data(struct srcu_struct *ssp)
+{
+ int cpu;
+ struct srcu_data *sdp;
+
+ /*
+ * Initialize the per-CPU srcu_data array, which feeds into the
+ * leaves of the srcu_node tree.
+ */
+ WARN_ON_ONCE(ARRAY_SIZE(sdp->srcu_lock_count) !=
+ ARRAY_SIZE(sdp->srcu_unlock_count));
+ for_each_possible_cpu(cpu) {
+ sdp = per_cpu_ptr(ssp->sda, cpu);
+ spin_lock_init(&ACCESS_PRIVATE(sdp, lock));
+ rcu_segcblist_init(&sdp->srcu_cblist);
+ sdp->srcu_cblist_invoking = false;
+ sdp->srcu_gp_seq_needed = ssp->srcu_gp_seq;
+ sdp->srcu_gp_seq_needed_exp = ssp->srcu_gp_seq;
+ sdp->mynode = NULL;
+ sdp->cpu = cpu;
+ INIT_WORK(&sdp->work, srcu_invoke_callbacks);
+ timer_setup(&sdp->delay_work, srcu_delay_timer, 0);
+ sdp->ssp = ssp;
+ }
+}
+
+/* Invalid seq state, used during snp node initialization */
+#define SRCU_SNP_INIT_SEQ 0x2
+
+/*
+ * Check whether sequence number corresponding to snp node,
+ * is invalid.
+ */
+static inline bool srcu_invl_snp_seq(unsigned long s)
+{
+ return rcu_seq_state(s) == SRCU_SNP_INIT_SEQ;
+}
+
+/*
+ * Allocated and initialize SRCU combining tree. Returns @true if
+ * allocation succeeded and @false otherwise.
+ */
+static bool init_srcu_struct_nodes(struct srcu_struct *ssp, gfp_t gfp_flags)
{
int cpu;
int i;
@@ -90,6 +171,12 @@ static void init_srcu_struct_nodes(struct srcu_struct *ssp, bool is_static)
struct srcu_node *snp;
struct srcu_node *snp_first;
+ /* Initialize geometry if it has not already been initialized. */
+ rcu_init_geometry();
+ ssp->node = kcalloc(rcu_num_nodes, sizeof(*ssp->node), gfp_flags);
+ if (!ssp->node)
+ return false;
+
/* Work out the overall tree geometry. */
ssp->level[0] = &ssp->node[0];
for (i = 1; i < rcu_num_lvls; i++)
@@ -102,10 +189,10 @@ static void init_srcu_struct_nodes(struct srcu_struct *ssp, bool is_static)
WARN_ON_ONCE(ARRAY_SIZE(snp->srcu_have_cbs) !=
ARRAY_SIZE(snp->srcu_data_have_cbs));
for (i = 0; i < ARRAY_SIZE(snp->srcu_have_cbs); i++) {
- snp->srcu_have_cbs[i] = 0;
+ snp->srcu_have_cbs[i] = SRCU_SNP_INIT_SEQ;
snp->srcu_data_have_cbs[i] = 0;
}
- snp->srcu_gp_seq_needed_exp = 0;
+ snp->srcu_gp_seq_needed_exp = SRCU_SNP_INIT_SEQ;
snp->grplo = -1;
snp->grphi = -1;
if (snp == &ssp->node[0]) {
@@ -126,47 +213,31 @@ static void init_srcu_struct_nodes(struct srcu_struct *ssp, bool is_static)
* Initialize the per-CPU srcu_data array, which feeds into the
* leaves of the srcu_node tree.
*/
- WARN_ON_ONCE(ARRAY_SIZE(sdp->srcu_lock_count) !=
- ARRAY_SIZE(sdp->srcu_unlock_count));
level = rcu_num_lvls - 1;
snp_first = ssp->level[level];
for_each_possible_cpu(cpu) {
sdp = per_cpu_ptr(ssp->sda, cpu);
- spin_lock_init(&ACCESS_PRIVATE(sdp, lock));
- rcu_segcblist_init(&sdp->srcu_cblist);
- sdp->srcu_cblist_invoking = false;
- sdp->srcu_gp_seq_needed = ssp->srcu_gp_seq;
- sdp->srcu_gp_seq_needed_exp = ssp->srcu_gp_seq;
sdp->mynode = &snp_first[cpu / levelspread[level]];
for (snp = sdp->mynode; snp != NULL; snp = snp->srcu_parent) {
if (snp->grplo < 0)
snp->grplo = cpu;
snp->grphi = cpu;
}
- sdp->cpu = cpu;
- INIT_WORK(&sdp->work, srcu_invoke_callbacks);
- timer_setup(&sdp->delay_work, srcu_delay_timer, 0);
- sdp->ssp = ssp;
sdp->grpmask = 1 << (cpu - sdp->mynode->grplo);
- if (is_static)
- continue;
-
- /* Dynamically allocated, better be no srcu_read_locks()! */
- for (i = 0; i < ARRAY_SIZE(sdp->srcu_lock_count); i++) {
- sdp->srcu_lock_count[i] = 0;
- sdp->srcu_unlock_count[i] = 0;
- }
}
+ smp_store_release(&ssp->srcu_size_state, SRCU_SIZE_WAIT_BARRIER);
+ return true;
}
/*
* Initialize non-compile-time initialized fields, including the
- * associated srcu_node and srcu_data structures. The is_static
- * parameter is passed through to init_srcu_struct_nodes(), and
- * also tells us that ->sda has already been wired up to srcu_data.
+ * associated srcu_node and srcu_data structures. The is_static parameter
+ * tells us that ->sda has already been wired up to srcu_data.
*/
static int init_srcu_struct_fields(struct srcu_struct *ssp, bool is_static)
{
+ ssp->srcu_size_state = SRCU_SIZE_SMALL;
+ ssp->node = NULL;
mutex_init(&ssp->srcu_cb_mutex);
mutex_init(&ssp->srcu_gp_mutex);
ssp->srcu_idx = 0;
@@ -175,13 +246,27 @@ static int init_srcu_struct_fields(struct srcu_struct *ssp, bool is_static)
mutex_init(&ssp->srcu_barrier_mutex);
atomic_set(&ssp->srcu_barrier_cpu_cnt, 0);
INIT_DELAYED_WORK(&ssp->work, process_srcu);
+ ssp->sda_is_static = is_static;
if (!is_static)
ssp->sda = alloc_percpu(struct srcu_data);
- init_srcu_struct_nodes(ssp, is_static);
+ if (!ssp->sda)
+ return -ENOMEM;
+ init_srcu_struct_data(ssp);
ssp->srcu_gp_seq_needed_exp = 0;
ssp->srcu_last_gp_end = ktime_get_mono_fast_ns();
+ if (READ_ONCE(ssp->srcu_size_state) == SRCU_SIZE_SMALL && SRCU_SIZING_IS_INIT()) {
+ if (!init_srcu_struct_nodes(ssp, GFP_ATOMIC)) {
+ if (!ssp->sda_is_static) {
+ free_percpu(ssp->sda);
+ ssp->sda = NULL;
+ return -ENOMEM;
+ }
+ } else {
+ WRITE_ONCE(ssp->srcu_size_state, SRCU_SIZE_BIG);
+ }
+ }
smp_store_release(&ssp->srcu_gp_seq_needed, 0); /* Init done. */
- return ssp->sda ? 0 : -ENOMEM;
+ return 0;
}
#ifdef CONFIG_DEBUG_LOCK_ALLOC
@@ -217,6 +302,86 @@ EXPORT_SYMBOL_GPL(init_srcu_struct);
#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
/*
+ * Initiate a transition to SRCU_SIZE_BIG with lock held.
+ */
+static void __srcu_transition_to_big(struct srcu_struct *ssp)
+{
+ lockdep_assert_held(&ACCESS_PRIVATE(ssp, lock));
+ smp_store_release(&ssp->srcu_size_state, SRCU_SIZE_ALLOC);
+}
+
+/*
+ * Initiate an idempotent transition to SRCU_SIZE_BIG.
+ */
+static void srcu_transition_to_big(struct srcu_struct *ssp)
+{
+ unsigned long flags;
+
+ /* Double-checked locking on ->srcu_size-state. */
+ if (smp_load_acquire(&ssp->srcu_size_state) != SRCU_SIZE_SMALL)
+ return;
+ spin_lock_irqsave_rcu_node(ssp, flags);
+ if (smp_load_acquire(&ssp->srcu_size_state) != SRCU_SIZE_SMALL) {
+ spin_unlock_irqrestore_rcu_node(ssp, flags);
+ return;
+ }
+ __srcu_transition_to_big(ssp);
+ spin_unlock_irqrestore_rcu_node(ssp, flags);
+}
+
+/*
+ * Check to see if the just-encountered contention event justifies
+ * a transition to SRCU_SIZE_BIG.
+ */
+static void spin_lock_irqsave_check_contention(struct srcu_struct *ssp)
+{
+ unsigned long j;
+
+ if (!SRCU_SIZING_IS_CONTEND() || ssp->srcu_size_state)
+ return;
+ j = jiffies;
+ if (ssp->srcu_size_jiffies != j) {
+ ssp->srcu_size_jiffies = j;
+ ssp->srcu_n_lock_retries = 0;
+ }
+ if (++ssp->srcu_n_lock_retries <= small_contention_lim)
+ return;
+ __srcu_transition_to_big(ssp);
+}
+
+/*
+ * Acquire the specified srcu_data structure's ->lock, but check for
+ * excessive contention, which results in initiation of a transition
+ * to SRCU_SIZE_BIG. But only if the srcutree.convert_to_big module
+ * parameter permits this.
+ */
+static void spin_lock_irqsave_sdp_contention(struct srcu_data *sdp, unsigned long *flags)
+{
+ struct srcu_struct *ssp = sdp->ssp;
+
+ if (spin_trylock_irqsave_rcu_node(sdp, *flags))
+ return;
+ spin_lock_irqsave_rcu_node(ssp, *flags);
+ spin_lock_irqsave_check_contention(ssp);
+ spin_unlock_irqrestore_rcu_node(ssp, *flags);
+ spin_lock_irqsave_rcu_node(sdp, *flags);
+}
+
+/*
+ * Acquire the specified srcu_struct structure's ->lock, but check for
+ * excessive contention, which results in initiation of a transition
+ * to SRCU_SIZE_BIG. But only if the srcutree.convert_to_big module
+ * parameter permits this.
+ */
+static void spin_lock_irqsave_ssp_contention(struct srcu_struct *ssp, unsigned long *flags)
+{
+ if (spin_trylock_irqsave_rcu_node(ssp, *flags))
+ return;
+ spin_lock_irqsave_rcu_node(ssp, *flags);
+ spin_lock_irqsave_check_contention(ssp);
+}
+
+/*
* First-use initialization of statically allocated srcu_struct
* structure. Wiring up the combining tree is more than can be
* done with compile-time initialization, so this check is added
@@ -346,7 +511,52 @@ static bool srcu_readers_active(struct srcu_struct *ssp)
return sum;
}
-#define SRCU_INTERVAL 1
+/*
+ * We use an adaptive strategy for synchronize_srcu() and especially for
+ * synchronize_srcu_expedited(). We spin for a fixed time period
+ * (defined below, boot time configurable) to allow SRCU readers to exit
+ * their read-side critical sections. If there are still some readers
+ * after one jiffy, we repeatedly block for one jiffy time periods.
+ * The blocking time is increased as the grace-period age increases,
+ * with max blocking time capped at 10 jiffies.
+ */
+#define SRCU_DEFAULT_RETRY_CHECK_DELAY 5
+
+static ulong srcu_retry_check_delay = SRCU_DEFAULT_RETRY_CHECK_DELAY;
+module_param(srcu_retry_check_delay, ulong, 0444);
+
+#define SRCU_INTERVAL 1 // Base delay if no expedited GPs pending.
+#define SRCU_MAX_INTERVAL 10 // Maximum incremental delay from slow readers.
+
+#define SRCU_DEFAULT_MAX_NODELAY_PHASE_LO 3UL // Lowmark on default per-GP-phase
+ // no-delay instances.
+#define SRCU_DEFAULT_MAX_NODELAY_PHASE_HI 1000UL // Highmark on default per-GP-phase
+ // no-delay instances.
+
+#define SRCU_UL_CLAMP_LO(val, low) ((val) > (low) ? (val) : (low))
+#define SRCU_UL_CLAMP_HI(val, high) ((val) < (high) ? (val) : (high))
+#define SRCU_UL_CLAMP(val, low, high) SRCU_UL_CLAMP_HI(SRCU_UL_CLAMP_LO((val), (low)), (high))
+// per-GP-phase no-delay instances adjusted to allow non-sleeping poll upto
+// one jiffies time duration. Mult by 2 is done to factor in the srcu_get_delay()
+// called from process_srcu().
+#define SRCU_DEFAULT_MAX_NODELAY_PHASE_ADJUSTED \
+ (2UL * USEC_PER_SEC / HZ / SRCU_DEFAULT_RETRY_CHECK_DELAY)
+
+// Maximum per-GP-phase consecutive no-delay instances.
+#define SRCU_DEFAULT_MAX_NODELAY_PHASE \
+ SRCU_UL_CLAMP(SRCU_DEFAULT_MAX_NODELAY_PHASE_ADJUSTED, \
+ SRCU_DEFAULT_MAX_NODELAY_PHASE_LO, \
+ SRCU_DEFAULT_MAX_NODELAY_PHASE_HI)
+
+static ulong srcu_max_nodelay_phase = SRCU_DEFAULT_MAX_NODELAY_PHASE;
+module_param(srcu_max_nodelay_phase, ulong, 0444);
+
+// Maximum consecutive no-delay instances.
+#define SRCU_DEFAULT_MAX_NODELAY (SRCU_DEFAULT_MAX_NODELAY_PHASE > 100 ? \
+ SRCU_DEFAULT_MAX_NODELAY_PHASE : 100)
+
+static ulong srcu_max_nodelay = SRCU_DEFAULT_MAX_NODELAY;
+module_param(srcu_max_nodelay, ulong, 0444);
/*
* Return grace-period delay, zero if there are expedited grace
@@ -354,10 +564,24 @@ static bool srcu_readers_active(struct srcu_struct *ssp)
*/
static unsigned long srcu_get_delay(struct srcu_struct *ssp)
{
- if (ULONG_CMP_LT(READ_ONCE(ssp->srcu_gp_seq),
- READ_ONCE(ssp->srcu_gp_seq_needed_exp)))
- return 0;
- return SRCU_INTERVAL;
+ unsigned long gpstart;
+ unsigned long j;
+ unsigned long jbase = SRCU_INTERVAL;
+
+ if (ULONG_CMP_LT(READ_ONCE(ssp->srcu_gp_seq), READ_ONCE(ssp->srcu_gp_seq_needed_exp)))
+ jbase = 0;
+ if (rcu_seq_state(READ_ONCE(ssp->srcu_gp_seq))) {
+ j = jiffies - 1;
+ gpstart = READ_ONCE(ssp->srcu_gp_start);
+ if (time_after(j, gpstart))
+ jbase += j - gpstart;
+ if (!jbase) {
+ WRITE_ONCE(ssp->srcu_n_exp_nodelay, READ_ONCE(ssp->srcu_n_exp_nodelay) + 1);
+ if (READ_ONCE(ssp->srcu_n_exp_nodelay) > srcu_max_nodelay_phase)
+ jbase = 1;
+ }
+ }
+ return jbase > SRCU_MAX_INTERVAL ? SRCU_MAX_INTERVAL : jbase;
}
/**
@@ -385,13 +609,20 @@ void cleanup_srcu_struct(struct srcu_struct *ssp)
return; /* Forgot srcu_barrier(), so just leak it! */
}
if (WARN_ON(rcu_seq_state(READ_ONCE(ssp->srcu_gp_seq)) != SRCU_STATE_IDLE) ||
+ WARN_ON(rcu_seq_current(&ssp->srcu_gp_seq) != ssp->srcu_gp_seq_needed) ||
WARN_ON(srcu_readers_active(ssp))) {
- pr_info("%s: Active srcu_struct %p state: %d\n",
- __func__, ssp, rcu_seq_state(READ_ONCE(ssp->srcu_gp_seq)));
+ pr_info("%s: Active srcu_struct %p read state: %d gp state: %lu/%lu\n",
+ __func__, ssp, rcu_seq_state(READ_ONCE(ssp->srcu_gp_seq)),
+ rcu_seq_current(&ssp->srcu_gp_seq), ssp->srcu_gp_seq_needed);
return; /* Caller forgot to stop doing call_srcu()? */
}
- free_percpu(ssp->sda);
- ssp->sda = NULL;
+ if (!ssp->sda_is_static) {
+ free_percpu(ssp->sda);
+ ssp->sda = NULL;
+ }
+ kfree(ssp->node);
+ ssp->node = NULL;
+ ssp->srcu_size_state = SRCU_SIZE_SMALL;
}
EXPORT_SYMBOL_GPL(cleanup_srcu_struct);
@@ -424,22 +655,17 @@ void __srcu_read_unlock(struct srcu_struct *ssp, int idx)
EXPORT_SYMBOL_GPL(__srcu_read_unlock);
/*
- * We use an adaptive strategy for synchronize_srcu() and especially for
- * synchronize_srcu_expedited(). We spin for a fixed time period
- * (defined below) to allow SRCU readers to exit their read-side critical
- * sections. If there are still some readers after a few microseconds,
- * we repeatedly block for 1-millisecond time periods.
- */
-#define SRCU_RETRY_CHECK_DELAY 5
-
-/*
* Start an SRCU grace period.
*/
static void srcu_gp_start(struct srcu_struct *ssp)
{
- struct srcu_data *sdp = this_cpu_ptr(ssp->sda);
+ struct srcu_data *sdp;
int state;
+ if (smp_load_acquire(&ssp->srcu_size_state) < SRCU_SIZE_WAIT_BARRIER)
+ sdp = per_cpu_ptr(ssp->sda, 0);
+ else
+ sdp = this_cpu_ptr(ssp->sda);
lockdep_assert_held(&ACCESS_PRIVATE(ssp, lock));
WARN_ON_ONCE(ULONG_CMP_GE(ssp->srcu_gp_seq, ssp->srcu_gp_seq_needed));
spin_lock_rcu_node(sdp); /* Interrupts already disabled. */
@@ -448,9 +674,11 @@ static void srcu_gp_start(struct srcu_struct *ssp)
(void)rcu_segcblist_accelerate(&sdp->srcu_cblist,
rcu_seq_snap(&ssp->srcu_gp_seq));
spin_unlock_rcu_node(sdp); /* Interrupts remain disabled. */
+ WRITE_ONCE(ssp->srcu_gp_start, jiffies);
+ WRITE_ONCE(ssp->srcu_n_exp_nodelay, 0);
smp_mb(); /* Order prior store to ->srcu_gp_seq_needed vs. GP start. */
rcu_seq_start(&ssp->srcu_gp_seq);
- state = rcu_seq_state(READ_ONCE(ssp->srcu_gp_seq));
+ state = rcu_seq_state(ssp->srcu_gp_seq);
WARN_ON_ONCE(state != SRCU_STATE_SCAN1);
}
@@ -511,7 +739,7 @@ static void srcu_schedule_cbs_snp(struct srcu_struct *ssp, struct srcu_node *snp
*/
static void srcu_gp_end(struct srcu_struct *ssp)
{
- unsigned long cbdelay;
+ unsigned long cbdelay = 1;
bool cbs;
bool last_lvl;
int cpu;
@@ -520,7 +748,9 @@ static void srcu_gp_end(struct srcu_struct *ssp)
int idx;
unsigned long mask;
struct srcu_data *sdp;
+ unsigned long sgsne;
struct srcu_node *snp;
+ int ss_state;
/* Prevent more than one additional grace period. */
mutex_lock(&ssp->srcu_cb_mutex);
@@ -529,49 +759,58 @@ static void srcu_gp_end(struct srcu_struct *ssp)
spin_lock_irq_rcu_node(ssp);
idx = rcu_seq_state(ssp->srcu_gp_seq);
WARN_ON_ONCE(idx != SRCU_STATE_SCAN2);
- cbdelay = srcu_get_delay(ssp);
+ if (ULONG_CMP_LT(READ_ONCE(ssp->srcu_gp_seq), READ_ONCE(ssp->srcu_gp_seq_needed_exp)))
+ cbdelay = 0;
+
WRITE_ONCE(ssp->srcu_last_gp_end, ktime_get_mono_fast_ns());
rcu_seq_end(&ssp->srcu_gp_seq);
gpseq = rcu_seq_current(&ssp->srcu_gp_seq);
if (ULONG_CMP_LT(ssp->srcu_gp_seq_needed_exp, gpseq))
- ssp->srcu_gp_seq_needed_exp = gpseq;
+ WRITE_ONCE(ssp->srcu_gp_seq_needed_exp, gpseq);
spin_unlock_irq_rcu_node(ssp);
mutex_unlock(&ssp->srcu_gp_mutex);
/* A new grace period can start at this point. But only one. */
/* Initiate callback invocation as needed. */
- idx = rcu_seq_ctr(gpseq) % ARRAY_SIZE(snp->srcu_have_cbs);
- srcu_for_each_node_breadth_first(ssp, snp) {
- spin_lock_irq_rcu_node(snp);
- cbs = false;
- last_lvl = snp >= ssp->level[rcu_num_lvls - 1];
- if (last_lvl)
- cbs = snp->srcu_have_cbs[idx] == gpseq;
- snp->srcu_have_cbs[idx] = gpseq;
- rcu_seq_set_state(&snp->srcu_have_cbs[idx], 1);
- if (ULONG_CMP_LT(snp->srcu_gp_seq_needed_exp, gpseq))
- snp->srcu_gp_seq_needed_exp = gpseq;
- mask = snp->srcu_data_have_cbs[idx];
- snp->srcu_data_have_cbs[idx] = 0;
- spin_unlock_irq_rcu_node(snp);
- if (cbs)
- srcu_schedule_cbs_snp(ssp, snp, mask, cbdelay);
-
- /* Occasionally prevent srcu_data counter wrap. */
- if (!(gpseq & counter_wrap_check) && last_lvl)
- for (cpu = snp->grplo; cpu <= snp->grphi; cpu++) {
- sdp = per_cpu_ptr(ssp->sda, cpu);
- spin_lock_irqsave_rcu_node(sdp, flags);
- if (ULONG_CMP_GE(gpseq,
- sdp->srcu_gp_seq_needed + 100))
- sdp->srcu_gp_seq_needed = gpseq;
- if (ULONG_CMP_GE(gpseq,
- sdp->srcu_gp_seq_needed_exp + 100))
- sdp->srcu_gp_seq_needed_exp = gpseq;
- spin_unlock_irqrestore_rcu_node(sdp, flags);
- }
+ ss_state = smp_load_acquire(&ssp->srcu_size_state);
+ if (ss_state < SRCU_SIZE_WAIT_BARRIER) {
+ srcu_schedule_cbs_sdp(per_cpu_ptr(ssp->sda, 0), cbdelay);
+ } else {
+ idx = rcu_seq_ctr(gpseq) % ARRAY_SIZE(snp->srcu_have_cbs);
+ srcu_for_each_node_breadth_first(ssp, snp) {
+ spin_lock_irq_rcu_node(snp);
+ cbs = false;
+ last_lvl = snp >= ssp->level[rcu_num_lvls - 1];
+ if (last_lvl)
+ cbs = ss_state < SRCU_SIZE_BIG || snp->srcu_have_cbs[idx] == gpseq;
+ snp->srcu_have_cbs[idx] = gpseq;
+ rcu_seq_set_state(&snp->srcu_have_cbs[idx], 1);
+ sgsne = snp->srcu_gp_seq_needed_exp;
+ if (srcu_invl_snp_seq(sgsne) || ULONG_CMP_LT(sgsne, gpseq))
+ WRITE_ONCE(snp->srcu_gp_seq_needed_exp, gpseq);
+ if (ss_state < SRCU_SIZE_BIG)
+ mask = ~0;
+ else
+ mask = snp->srcu_data_have_cbs[idx];
+ snp->srcu_data_have_cbs[idx] = 0;
+ spin_unlock_irq_rcu_node(snp);
+ if (cbs)
+ srcu_schedule_cbs_snp(ssp, snp, mask, cbdelay);
+ }
}
+ /* Occasionally prevent srcu_data counter wrap. */
+ if (!(gpseq & counter_wrap_check))
+ for_each_possible_cpu(cpu) {
+ sdp = per_cpu_ptr(ssp->sda, cpu);
+ spin_lock_irqsave_rcu_node(sdp, flags);
+ if (ULONG_CMP_GE(gpseq, sdp->srcu_gp_seq_needed + 100))
+ sdp->srcu_gp_seq_needed = gpseq;
+ if (ULONG_CMP_GE(gpseq, sdp->srcu_gp_seq_needed_exp + 100))
+ sdp->srcu_gp_seq_needed_exp = gpseq;
+ spin_unlock_irqrestore_rcu_node(sdp, flags);
+ }
+
/* Callback initiation done, allow grace periods after next. */
mutex_unlock(&ssp->srcu_cb_mutex);
@@ -586,6 +825,14 @@ static void srcu_gp_end(struct srcu_struct *ssp)
} else {
spin_unlock_irq_rcu_node(ssp);
}
+
+ /* Transition to big if needed. */
+ if (ss_state != SRCU_SIZE_SMALL && ss_state != SRCU_SIZE_BIG) {
+ if (ss_state == SRCU_SIZE_ALLOC)
+ init_srcu_struct_nodes(ssp, GFP_KERNEL);
+ else
+ smp_store_release(&ssp->srcu_size_state, ss_state + 1);
+ }
}
/*
@@ -599,22 +846,26 @@ static void srcu_funnel_exp_start(struct srcu_struct *ssp, struct srcu_node *snp
unsigned long s)
{
unsigned long flags;
+ unsigned long sgsne;
- for (; snp != NULL; snp = snp->srcu_parent) {
- if (rcu_seq_done(&ssp->srcu_gp_seq, s) ||
- ULONG_CMP_GE(READ_ONCE(snp->srcu_gp_seq_needed_exp), s))
- return;
- spin_lock_irqsave_rcu_node(snp, flags);
- if (ULONG_CMP_GE(snp->srcu_gp_seq_needed_exp, s)) {
+ if (snp)
+ for (; snp != NULL; snp = snp->srcu_parent) {
+ sgsne = READ_ONCE(snp->srcu_gp_seq_needed_exp);
+ if (rcu_seq_done(&ssp->srcu_gp_seq, s) ||
+ (!srcu_invl_snp_seq(sgsne) && ULONG_CMP_GE(sgsne, s)))
+ return;
+ spin_lock_irqsave_rcu_node(snp, flags);
+ sgsne = snp->srcu_gp_seq_needed_exp;
+ if (!srcu_invl_snp_seq(sgsne) && ULONG_CMP_GE(sgsne, s)) {
+ spin_unlock_irqrestore_rcu_node(snp, flags);
+ return;
+ }
+ WRITE_ONCE(snp->srcu_gp_seq_needed_exp, s);
spin_unlock_irqrestore_rcu_node(snp, flags);
- return;
}
- WRITE_ONCE(snp->srcu_gp_seq_needed_exp, s);
- spin_unlock_irqrestore_rcu_node(snp, flags);
- }
- spin_lock_irqsave_rcu_node(ssp, flags);
+ spin_lock_irqsave_ssp_contention(ssp, &flags);
if (ULONG_CMP_LT(ssp->srcu_gp_seq_needed_exp, s))
- ssp->srcu_gp_seq_needed_exp = s;
+ WRITE_ONCE(ssp->srcu_gp_seq_needed_exp, s);
spin_unlock_irqrestore_rcu_node(ssp, flags);
}
@@ -633,39 +884,47 @@ static void srcu_funnel_gp_start(struct srcu_struct *ssp, struct srcu_data *sdp,
{
unsigned long flags;
int idx = rcu_seq_ctr(s) % ARRAY_SIZE(sdp->mynode->srcu_have_cbs);
- struct srcu_node *snp = sdp->mynode;
+ unsigned long sgsne;
+ struct srcu_node *snp;
+ struct srcu_node *snp_leaf;
unsigned long snp_seq;
- /* Each pass through the loop does one level of the srcu_node tree. */
- for (; snp != NULL; snp = snp->srcu_parent) {
- if (rcu_seq_done(&ssp->srcu_gp_seq, s) && snp != sdp->mynode)
- return; /* GP already done and CBs recorded. */
- spin_lock_irqsave_rcu_node(snp, flags);
- if (ULONG_CMP_GE(snp->srcu_have_cbs[idx], s)) {
+ /* Ensure that snp node tree is fully initialized before traversing it */
+ if (smp_load_acquire(&ssp->srcu_size_state) < SRCU_SIZE_WAIT_BARRIER)
+ snp_leaf = NULL;
+ else
+ snp_leaf = sdp->mynode;
+
+ if (snp_leaf)
+ /* Each pass through the loop does one level of the srcu_node tree. */
+ for (snp = snp_leaf; snp != NULL; snp = snp->srcu_parent) {
+ if (rcu_seq_done(&ssp->srcu_gp_seq, s) && snp != snp_leaf)
+ return; /* GP already done and CBs recorded. */
+ spin_lock_irqsave_rcu_node(snp, flags);
snp_seq = snp->srcu_have_cbs[idx];
- if (snp == sdp->mynode && snp_seq == s)
- snp->srcu_data_have_cbs[idx] |= sdp->grpmask;
- spin_unlock_irqrestore_rcu_node(snp, flags);
- if (snp == sdp->mynode && snp_seq != s) {
- srcu_schedule_cbs_sdp(sdp, do_norm
- ? SRCU_INTERVAL
- : 0);
+ if (!srcu_invl_snp_seq(snp_seq) && ULONG_CMP_GE(snp_seq, s)) {
+ if (snp == snp_leaf && snp_seq == s)
+ snp->srcu_data_have_cbs[idx] |= sdp->grpmask;
+ spin_unlock_irqrestore_rcu_node(snp, flags);
+ if (snp == snp_leaf && snp_seq != s) {
+ srcu_schedule_cbs_sdp(sdp, do_norm ? SRCU_INTERVAL : 0);
+ return;
+ }
+ if (!do_norm)
+ srcu_funnel_exp_start(ssp, snp, s);
return;
}
- if (!do_norm)
- srcu_funnel_exp_start(ssp, snp, s);
- return;
+ snp->srcu_have_cbs[idx] = s;
+ if (snp == snp_leaf)
+ snp->srcu_data_have_cbs[idx] |= sdp->grpmask;
+ sgsne = snp->srcu_gp_seq_needed_exp;
+ if (!do_norm && (srcu_invl_snp_seq(sgsne) || ULONG_CMP_LT(sgsne, s)))
+ WRITE_ONCE(snp->srcu_gp_seq_needed_exp, s);
+ spin_unlock_irqrestore_rcu_node(snp, flags);
}
- snp->srcu_have_cbs[idx] = s;
- if (snp == sdp->mynode)
- snp->srcu_data_have_cbs[idx] |= sdp->grpmask;
- if (!do_norm && ULONG_CMP_LT(snp->srcu_gp_seq_needed_exp, s))
- snp->srcu_gp_seq_needed_exp = s;
- spin_unlock_irqrestore_rcu_node(snp, flags);
- }
/* Top of tree, must ensure the grace period will be started. */
- spin_lock_irqsave_rcu_node(ssp, flags);
+ spin_lock_irqsave_ssp_contention(ssp, &flags);
if (ULONG_CMP_LT(ssp->srcu_gp_seq_needed, s)) {
/*
* Record need for grace period s. Pair with load
@@ -674,16 +933,22 @@ static void srcu_funnel_gp_start(struct srcu_struct *ssp, struct srcu_data *sdp,
smp_store_release(&ssp->srcu_gp_seq_needed, s); /*^^^*/
}
if (!do_norm && ULONG_CMP_LT(ssp->srcu_gp_seq_needed_exp, s))
- ssp->srcu_gp_seq_needed_exp = s;
+ WRITE_ONCE(ssp->srcu_gp_seq_needed_exp, s);
/* If grace period not already done and none in progress, start it. */
if (!rcu_seq_done(&ssp->srcu_gp_seq, s) &&
rcu_seq_state(ssp->srcu_gp_seq) == SRCU_STATE_IDLE) {
WARN_ON_ONCE(ULONG_CMP_GE(ssp->srcu_gp_seq, ssp->srcu_gp_seq_needed));
srcu_gp_start(ssp);
+
+ // And how can that list_add() in the "else" clause
+ // possibly be safe for concurrent execution? Well,
+ // it isn't. And it does not have to be. After all, it
+ // can only be executed during early boot when there is only
+ // the one boot CPU running with interrupts still disabled.
if (likely(srcu_init_done))
queue_delayed_work(rcu_gp_wq, &ssp->work,
- srcu_get_delay(ssp));
+ !!srcu_get_delay(ssp));
else if (list_empty(&ssp->work.work.entry))
list_add(&ssp->work.work.entry, &srcu_boot_list);
}
@@ -697,12 +962,16 @@ static void srcu_funnel_gp_start(struct srcu_struct *ssp, struct srcu_data *sdp,
*/
static bool try_check_zero(struct srcu_struct *ssp, int idx, int trycount)
{
+ unsigned long curdelay;
+
+ curdelay = !srcu_get_delay(ssp);
+
for (;;) {
if (srcu_readers_active_idx_check(ssp, idx))
return true;
- if (--trycount + !srcu_get_delay(ssp) <= 0)
+ if ((--trycount + curdelay) <= 0)
return false;
- udelay(SRCU_RETRY_CHECK_DELAY);
+ udelay(srcu_retry_check_delay);
}
}
@@ -753,7 +1022,7 @@ static void srcu_flip(struct srcu_struct *ssp)
* it, if this function was preempted for enough time for the counters
* to wrap, it really doesn't matter whether or not we expedite the grace
* period. The extra overhead of a needlessly expedited grace period is
- * negligible when amoritized over that time period, and the extra latency
+ * negligible when amortized over that time period, and the extra latency
* of a needlessly non-expedited grace period is similarly negligible.
*/
static bool srcu_might_be_idle(struct srcu_struct *ssp)
@@ -764,19 +1033,20 @@ static bool srcu_might_be_idle(struct srcu_struct *ssp)
unsigned long t;
unsigned long tlast;
+ check_init_srcu_struct(ssp);
/* If the local srcu_data structure has callbacks, not idle. */
- local_irq_save(flags);
- sdp = this_cpu_ptr(ssp->sda);
+ sdp = raw_cpu_ptr(ssp->sda);
+ spin_lock_irqsave_rcu_node(sdp, flags);
if (rcu_segcblist_pend_cbs(&sdp->srcu_cblist)) {
- local_irq_restore(flags);
+ spin_unlock_irqrestore_rcu_node(sdp, flags);
return false; /* Callbacks already present, so not idle. */
}
- local_irq_restore(flags);
+ spin_unlock_irqrestore_rcu_node(sdp, flags);
/*
- * No local callbacks, so probabalistically probe global state.
+ * No local callbacks, so probabilistically probe global state.
* Exact information would require acquiring locks, which would
- * kill scalability, hence the probabalistic nature of the probe.
+ * kill scalability, hence the probabilistic nature of the probe.
*/
/* First, see if enough time has passed since the last GP. */
@@ -805,6 +1075,59 @@ static void srcu_leak_callback(struct rcu_head *rhp)
}
/*
+ * Start an SRCU grace period, and also queue the callback if non-NULL.
+ */
+static unsigned long srcu_gp_start_if_needed(struct srcu_struct *ssp,
+ struct rcu_head *rhp, bool do_norm)
+{
+ unsigned long flags;
+ int idx;
+ bool needexp = false;
+ bool needgp = false;
+ unsigned long s;
+ struct srcu_data *sdp;
+ struct srcu_node *sdp_mynode;
+ int ss_state;
+
+ check_init_srcu_struct(ssp);
+ idx = srcu_read_lock(ssp);
+ ss_state = smp_load_acquire(&ssp->srcu_size_state);
+ if (ss_state < SRCU_SIZE_WAIT_CALL)
+ sdp = per_cpu_ptr(ssp->sda, 0);
+ else
+ sdp = raw_cpu_ptr(ssp->sda);
+ spin_lock_irqsave_sdp_contention(sdp, &flags);
+ if (rhp)
+ rcu_segcblist_enqueue(&sdp->srcu_cblist, rhp);
+ rcu_segcblist_advance(&sdp->srcu_cblist,
+ rcu_seq_current(&ssp->srcu_gp_seq));
+ s = rcu_seq_snap(&ssp->srcu_gp_seq);
+ (void)rcu_segcblist_accelerate(&sdp->srcu_cblist, s);
+ if (ULONG_CMP_LT(sdp->srcu_gp_seq_needed, s)) {
+ sdp->srcu_gp_seq_needed = s;
+ needgp = true;
+ }
+ if (!do_norm && ULONG_CMP_LT(sdp->srcu_gp_seq_needed_exp, s)) {
+ sdp->srcu_gp_seq_needed_exp = s;
+ needexp = true;
+ }
+ spin_unlock_irqrestore_rcu_node(sdp, flags);
+
+ /* Ensure that snp node tree is fully initialized before traversing it */
+ if (ss_state < SRCU_SIZE_WAIT_BARRIER)
+ sdp_mynode = NULL;
+ else
+ sdp_mynode = sdp->mynode;
+
+ if (needgp)
+ srcu_funnel_gp_start(ssp, sdp, s, do_norm);
+ else if (needexp)
+ srcu_funnel_exp_start(ssp, sdp_mynode, s);
+ srcu_read_unlock(ssp, idx);
+ return s;
+}
+
+/*
* Enqueue an SRCU callback on the srcu_data structure associated with
* the current CPU and the specified srcu_struct structure, initiating
* grace-period processing if it is not already running.
@@ -835,14 +1158,6 @@ static void srcu_leak_callback(struct rcu_head *rhp)
static void __call_srcu(struct srcu_struct *ssp, struct rcu_head *rhp,
rcu_callback_t func, bool do_norm)
{
- unsigned long flags;
- int idx;
- bool needexp = false;
- bool needgp = false;
- unsigned long s;
- struct srcu_data *sdp;
-
- check_init_srcu_struct(ssp);
if (debug_rcu_head_queue(rhp)) {
/* Probable double call_srcu(), so leak the callback. */
WRITE_ONCE(rhp->func, srcu_leak_callback);
@@ -850,29 +1165,7 @@ static void __call_srcu(struct srcu_struct *ssp, struct rcu_head *rhp,
return;
}
rhp->func = func;
- idx = srcu_read_lock(ssp);
- local_irq_save(flags);
- sdp = this_cpu_ptr(ssp->sda);
- spin_lock_rcu_node(sdp);
- rcu_segcblist_enqueue(&sdp->srcu_cblist, rhp);
- rcu_segcblist_advance(&sdp->srcu_cblist,
- rcu_seq_current(&ssp->srcu_gp_seq));
- s = rcu_seq_snap(&ssp->srcu_gp_seq);
- (void)rcu_segcblist_accelerate(&sdp->srcu_cblist, s);
- if (ULONG_CMP_LT(sdp->srcu_gp_seq_needed, s)) {
- sdp->srcu_gp_seq_needed = s;
- needgp = true;
- }
- if (!do_norm && ULONG_CMP_LT(sdp->srcu_gp_seq_needed_exp, s)) {
- sdp->srcu_gp_seq_needed_exp = s;
- needexp = true;
- }
- spin_unlock_irqrestore_rcu_node(sdp, flags);
- if (needgp)
- srcu_funnel_gp_start(ssp, sdp, s, do_norm);
- else if (needexp)
- srcu_funnel_exp_start(ssp, sdp->mynode, s);
- srcu_read_unlock(ssp, idx);
+ (void)srcu_gp_start_if_needed(ssp, rhp, do_norm);
}
/**
@@ -906,7 +1199,7 @@ static void __synchronize_srcu(struct srcu_struct *ssp, bool do_norm)
{
struct rcu_synchronize rcu;
- RCU_LOCKDEP_WARN(lock_is_held(&ssp->dep_map) ||
+ RCU_LOCKDEP_WARN(lockdep_is_held(ssp) ||
lock_is_held(&rcu_bh_lock_map) ||
lock_is_held(&rcu_lock_map) ||
lock_is_held(&rcu_sched_lock_map),
@@ -987,6 +1280,9 @@ EXPORT_SYMBOL_GPL(synchronize_srcu_expedited);
* synchronize_srcu(), srcu_read_lock(), and srcu_read_unlock() are
* passed the same srcu_struct structure.
*
+ * Implementation of these memory-ordering guarantees is similar to
+ * that of synchronize_rcu().
+ *
* If SRCU is likely idle, expedite the first request. This semantic
* was provided by Classic SRCU, and is relied upon by its users, so TREE
* SRCU must also provide it. Note that detecting idleness is heuristic
@@ -1001,6 +1297,77 @@ void synchronize_srcu(struct srcu_struct *ssp)
}
EXPORT_SYMBOL_GPL(synchronize_srcu);
+/**
+ * get_state_synchronize_srcu - Provide an end-of-grace-period cookie
+ * @ssp: srcu_struct to provide cookie for.
+ *
+ * This function returns a cookie that can be passed to
+ * poll_state_synchronize_srcu(), which will return true if a full grace
+ * period has elapsed in the meantime. It is the caller's responsibility
+ * to make sure that grace period happens, for example, by invoking
+ * call_srcu() after return from get_state_synchronize_srcu().
+ */
+unsigned long get_state_synchronize_srcu(struct srcu_struct *ssp)
+{
+ // Any prior manipulation of SRCU-protected data must happen
+ // before the load from ->srcu_gp_seq.
+ smp_mb();
+ return rcu_seq_snap(&ssp->srcu_gp_seq);
+}
+EXPORT_SYMBOL_GPL(get_state_synchronize_srcu);
+
+/**
+ * start_poll_synchronize_srcu - Provide cookie and start grace period
+ * @ssp: srcu_struct to provide cookie for.
+ *
+ * This function returns a cookie that can be passed to
+ * poll_state_synchronize_srcu(), which will return true if a full grace
+ * period has elapsed in the meantime. Unlike get_state_synchronize_srcu(),
+ * this function also ensures that any needed SRCU grace period will be
+ * started. This convenience does come at a cost in terms of CPU overhead.
+ */
+unsigned long start_poll_synchronize_srcu(struct srcu_struct *ssp)
+{
+ return srcu_gp_start_if_needed(ssp, NULL, true);
+}
+EXPORT_SYMBOL_GPL(start_poll_synchronize_srcu);
+
+/**
+ * poll_state_synchronize_srcu - Has cookie's grace period ended?
+ * @ssp: srcu_struct to provide cookie for.
+ * @cookie: Return value from get_state_synchronize_srcu() or start_poll_synchronize_srcu().
+ *
+ * This function takes the cookie that was returned from either
+ * get_state_synchronize_srcu() or start_poll_synchronize_srcu(), and
+ * returns @true if an SRCU grace period elapsed since the time that the
+ * cookie was created.
+ *
+ * Because cookies are finite in size, wrapping/overflow is possible.
+ * This is more pronounced on 32-bit systems where cookies are 32 bits,
+ * where in theory wrapping could happen in about 14 hours assuming
+ * 25-microsecond expedited SRCU grace periods. However, a more likely
+ * overflow lower bound is on the order of 24 days in the case of
+ * one-millisecond SRCU grace periods. Of course, wrapping in a 64-bit
+ * system requires geologic timespans, as in more than seven million years
+ * even for expedited SRCU grace periods.
+ *
+ * Wrapping/overflow is much more of an issue for CONFIG_SMP=n systems
+ * that also have CONFIG_PREEMPTION=n, which selects Tiny SRCU. This uses
+ * a 16-bit cookie, which rcutorture routinely wraps in a matter of a
+ * few minutes. If this proves to be a problem, this counter will be
+ * expanded to the same size as for Tree SRCU.
+ */
+bool poll_state_synchronize_srcu(struct srcu_struct *ssp, unsigned long cookie)
+{
+ if (!rcu_seq_done(&ssp->srcu_gp_seq, cookie))
+ return false;
+ // Ensure that the end of the SRCU grace period happens before
+ // any subsequent code that the caller might execute.
+ smp_mb(); // ^^^
+ return true;
+}
+EXPORT_SYMBOL_GPL(poll_state_synchronize_srcu);
+
/*
* Callback function for srcu_barrier() use.
*/
@@ -1015,6 +1382,28 @@ static void srcu_barrier_cb(struct rcu_head *rhp)
complete(&ssp->srcu_barrier_completion);
}
+/*
+ * Enqueue an srcu_barrier() callback on the specified srcu_data
+ * structure's ->cblist. but only if that ->cblist already has at least one
+ * callback enqueued. Note that if a CPU already has callbacks enqueue,
+ * it must have already registered the need for a future grace period,
+ * so all we need do is enqueue a callback that will use the same grace
+ * period as the last callback already in the queue.
+ */
+static void srcu_barrier_one_cpu(struct srcu_struct *ssp, struct srcu_data *sdp)
+{
+ spin_lock_irq_rcu_node(sdp);
+ atomic_inc(&ssp->srcu_barrier_cpu_cnt);
+ sdp->srcu_barrier_head.func = srcu_barrier_cb;
+ debug_rcu_head_queue(&sdp->srcu_barrier_head);
+ if (!rcu_segcblist_entrain(&sdp->srcu_cblist,
+ &sdp->srcu_barrier_head)) {
+ debug_rcu_head_unqueue(&sdp->srcu_barrier_head);
+ atomic_dec(&ssp->srcu_barrier_cpu_cnt);
+ }
+ spin_unlock_irq_rcu_node(sdp);
+}
+
/**
* srcu_barrier - Wait until all in-flight call_srcu() callbacks complete.
* @ssp: srcu_struct on which to wait for in-flight callbacks.
@@ -1022,7 +1411,7 @@ static void srcu_barrier_cb(struct rcu_head *rhp)
void srcu_barrier(struct srcu_struct *ssp)
{
int cpu;
- struct srcu_data *sdp;
+ int idx;
unsigned long s = rcu_seq_snap(&ssp->srcu_barrier_seq);
check_init_srcu_struct(ssp);
@@ -1038,27 +1427,13 @@ void srcu_barrier(struct srcu_struct *ssp)
/* Initial count prevents reaching zero until all CBs are posted. */
atomic_set(&ssp->srcu_barrier_cpu_cnt, 1);
- /*
- * Each pass through this loop enqueues a callback, but only
- * on CPUs already having callbacks enqueued. Note that if
- * a CPU already has callbacks enqueue, it must have already
- * registered the need for a future grace period, so all we
- * need do is enqueue a callback that will use the same
- * grace period as the last callback already in the queue.
- */
- for_each_possible_cpu(cpu) {
- sdp = per_cpu_ptr(ssp->sda, cpu);
- spin_lock_irq_rcu_node(sdp);
- atomic_inc(&ssp->srcu_barrier_cpu_cnt);
- sdp->srcu_barrier_head.func = srcu_barrier_cb;
- debug_rcu_head_queue(&sdp->srcu_barrier_head);
- if (!rcu_segcblist_entrain(&sdp->srcu_cblist,
- &sdp->srcu_barrier_head)) {
- debug_rcu_head_unqueue(&sdp->srcu_barrier_head);
- atomic_dec(&ssp->srcu_barrier_cpu_cnt);
- }
- spin_unlock_irq_rcu_node(sdp);
- }
+ idx = srcu_read_lock(ssp);
+ if (smp_load_acquire(&ssp->srcu_size_state) < SRCU_SIZE_WAIT_BARRIER)
+ srcu_barrier_one_cpu(ssp, per_cpu_ptr(ssp->sda, 0));
+ else
+ for_each_possible_cpu(cpu)
+ srcu_barrier_one_cpu(ssp, per_cpu_ptr(ssp->sda, cpu));
+ srcu_read_unlock(ssp, idx);
/* Remove the initial count, at which point reaching zero can happen. */
if (atomic_dec_and_test(&ssp->srcu_barrier_cpu_cnt))
@@ -1079,7 +1454,7 @@ EXPORT_SYMBOL_GPL(srcu_barrier);
*/
unsigned long srcu_batches_completed(struct srcu_struct *ssp)
{
- return ssp->srcu_idx;
+ return READ_ONCE(ssp->srcu_idx);
}
EXPORT_SYMBOL_GPL(srcu_batches_completed);
@@ -1130,7 +1505,10 @@ static void srcu_advance_state(struct srcu_struct *ssp)
return; /* readers present, retry later. */
}
srcu_flip(ssp);
+ spin_lock_irq_rcu_node(ssp);
rcu_seq_set_state(&ssp->srcu_gp_seq, SRCU_STATE_SCAN2);
+ ssp->srcu_n_exp_nodelay = 0;
+ spin_unlock_irq_rcu_node(ssp);
}
if (rcu_seq_state(READ_ONCE(ssp->srcu_gp_seq)) == SRCU_STATE_SCAN2) {
@@ -1144,6 +1522,7 @@ static void srcu_advance_state(struct srcu_struct *ssp)
mutex_unlock(&ssp->srcu_gp_mutex);
return; /* readers present, retry later. */
}
+ ssp->srcu_n_exp_nodelay = 0;
srcu_gp_end(ssp); /* Releases ->srcu_gp_mutex. */
}
}
@@ -1156,6 +1535,7 @@ static void srcu_advance_state(struct srcu_struct *ssp)
*/
static void srcu_invoke_callbacks(struct work_struct *work)
{
+ long len;
bool more;
struct rcu_cblist ready_cbs;
struct rcu_head *rhp;
@@ -1178,6 +1558,7 @@ static void srcu_invoke_callbacks(struct work_struct *work)
/* We are on the job! Extract and invoke ready callbacks. */
sdp->srcu_cblist_invoking = true;
rcu_segcblist_extract_done_cbs(&sdp->srcu_cblist, &ready_cbs);
+ len = ready_cbs.len;
spin_unlock_irq_rcu_node(sdp);
rhp = rcu_cblist_dequeue(&ready_cbs);
for (; rhp != NULL; rhp = rcu_cblist_dequeue(&ready_cbs)) {
@@ -1186,13 +1567,14 @@ static void srcu_invoke_callbacks(struct work_struct *work)
rhp->func(rhp);
local_bh_enable();
}
+ WARN_ON_ONCE(ready_cbs.len);
/*
* Update counts, accelerate new callbacks, and if needed,
* schedule another round of callback invocation.
*/
spin_lock_irq_rcu_node(sdp);
- rcu_segcblist_insert_count(&sdp->srcu_cblist, &ready_cbs);
+ rcu_segcblist_add_len(&sdp->srcu_cblist, -len);
(void)rcu_segcblist_accelerate(&sdp->srcu_cblist,
rcu_seq_snap(&ssp->srcu_gp_seq));
sdp->srcu_cblist_invoking = false;
@@ -1231,12 +1613,28 @@ static void srcu_reschedule(struct srcu_struct *ssp, unsigned long delay)
*/
static void process_srcu(struct work_struct *work)
{
+ unsigned long curdelay;
+ unsigned long j;
struct srcu_struct *ssp;
ssp = container_of(work, struct srcu_struct, work.work);
srcu_advance_state(ssp);
- srcu_reschedule(ssp, srcu_get_delay(ssp));
+ curdelay = srcu_get_delay(ssp);
+ if (curdelay) {
+ WRITE_ONCE(ssp->reschedule_count, 0);
+ } else {
+ j = jiffies;
+ if (READ_ONCE(ssp->reschedule_jiffies) == j) {
+ WRITE_ONCE(ssp->reschedule_count, READ_ONCE(ssp->reschedule_count) + 1);
+ if (READ_ONCE(ssp->reschedule_count) > srcu_max_nodelay)
+ curdelay = 1;
+ } else {
+ WRITE_ONCE(ssp->reschedule_count, 1);
+ WRITE_ONCE(ssp->reschedule_jiffies, j);
+ }
+ }
+ srcu_reschedule(ssp, curdelay);
}
void srcutorture_get_gp_data(enum rcutorture_type test_type,
@@ -1250,43 +1648,69 @@ void srcutorture_get_gp_data(enum rcutorture_type test_type,
}
EXPORT_SYMBOL_GPL(srcutorture_get_gp_data);
+static const char * const srcu_size_state_name[] = {
+ "SRCU_SIZE_SMALL",
+ "SRCU_SIZE_ALLOC",
+ "SRCU_SIZE_WAIT_BARRIER",
+ "SRCU_SIZE_WAIT_CALL",
+ "SRCU_SIZE_WAIT_CBS1",
+ "SRCU_SIZE_WAIT_CBS2",
+ "SRCU_SIZE_WAIT_CBS3",
+ "SRCU_SIZE_WAIT_CBS4",
+ "SRCU_SIZE_BIG",
+ "SRCU_SIZE_???",
+};
+
void srcu_torture_stats_print(struct srcu_struct *ssp, char *tt, char *tf)
{
int cpu;
int idx;
unsigned long s0 = 0, s1 = 0;
+ int ss_state = READ_ONCE(ssp->srcu_size_state);
+ int ss_state_idx = ss_state;
idx = ssp->srcu_idx & 0x1;
- pr_alert("%s%s Tree SRCU g%ld per-CPU(idx=%d):",
- tt, tf, rcu_seq_current(&ssp->srcu_gp_seq), idx);
- for_each_possible_cpu(cpu) {
- unsigned long l0, l1;
- unsigned long u0, u1;
- long c0, c1;
- struct srcu_data *sdp;
-
- sdp = per_cpu_ptr(ssp->sda, cpu);
- u0 = sdp->srcu_unlock_count[!idx];
- u1 = sdp->srcu_unlock_count[idx];
-
- /*
- * Make sure that a lock is always counted if the corresponding
- * unlock is counted.
- */
- smp_rmb();
-
- l0 = sdp->srcu_lock_count[!idx];
- l1 = sdp->srcu_lock_count[idx];
-
- c0 = l0 - u0;
- c1 = l1 - u1;
- pr_cont(" %d(%ld,%ld %c)",
- cpu, c0, c1,
- "C."[rcu_segcblist_empty(&sdp->srcu_cblist)]);
- s0 += c0;
- s1 += c1;
+ if (ss_state < 0 || ss_state >= ARRAY_SIZE(srcu_size_state_name))
+ ss_state_idx = ARRAY_SIZE(srcu_size_state_name) - 1;
+ pr_alert("%s%s Tree SRCU g%ld state %d (%s)",
+ tt, tf, rcu_seq_current(&ssp->srcu_gp_seq), ss_state,
+ srcu_size_state_name[ss_state_idx]);
+ if (!ssp->sda) {
+ // Called after cleanup_srcu_struct(), perhaps.
+ pr_cont(" No per-CPU srcu_data structures (->sda == NULL).\n");
+ } else {
+ pr_cont(" per-CPU(idx=%d):", idx);
+ for_each_possible_cpu(cpu) {
+ unsigned long l0, l1;
+ unsigned long u0, u1;
+ long c0, c1;
+ struct srcu_data *sdp;
+
+ sdp = per_cpu_ptr(ssp->sda, cpu);
+ u0 = data_race(sdp->srcu_unlock_count[!idx]);
+ u1 = data_race(sdp->srcu_unlock_count[idx]);
+
+ /*
+ * Make sure that a lock is always counted if the corresponding
+ * unlock is counted.
+ */
+ smp_rmb();
+
+ l0 = data_race(sdp->srcu_lock_count[!idx]);
+ l1 = data_race(sdp->srcu_lock_count[idx]);
+
+ c0 = l0 - u0;
+ c1 = l1 - u1;
+ pr_cont(" %d(%ld,%ld %c)",
+ cpu, c0, c1,
+ "C."[rcu_segcblist_empty(&sdp->srcu_cblist)]);
+ s0 += c0;
+ s1 += c1;
+ }
+ pr_cont(" T(%ld,%ld)\n", s0, s1);
}
- pr_cont(" T(%ld,%ld)\n", s0, s1);
+ if (SRCU_SIZING_IS_TORTURE())
+ srcu_transition_to_big(ssp);
}
EXPORT_SYMBOL_GPL(srcu_torture_stats_print);
@@ -1295,6 +1719,11 @@ static int __init srcu_bootup_announce(void)
pr_info("Hierarchical SRCU implementation.\n");
if (exp_holdoff != DEFAULT_SRCU_EXP_HOLDOFF)
pr_info("\tNon-default auto-expedite holdoff of %lu ns.\n", exp_holdoff);
+ if (srcu_retry_check_delay != SRCU_DEFAULT_RETRY_CHECK_DELAY)
+ pr_info("\tNon-default retry check delay of %lu us.\n", srcu_retry_check_delay);
+ if (srcu_max_nodelay != SRCU_DEFAULT_MAX_NODELAY)
+ pr_info("\tNon-default max no-delay of %lu.\n", srcu_max_nodelay);
+ pr_info("\tMax phase no-delay instances is %lu.\n", srcu_max_nodelay_phase);
return 0;
}
early_initcall(srcu_bootup_announce);
@@ -1303,12 +1732,29 @@ void __init srcu_init(void)
{
struct srcu_struct *ssp;
+ /* Decide on srcu_struct-size strategy. */
+ if (SRCU_SIZING_IS(SRCU_SIZING_AUTO)) {
+ if (nr_cpu_ids >= big_cpu_lim) {
+ convert_to_big = SRCU_SIZING_INIT; // Don't bother waiting for contention.
+ pr_info("%s: Setting srcu_struct sizes to big.\n", __func__);
+ } else {
+ convert_to_big = SRCU_SIZING_NONE | SRCU_SIZING_CONTEND;
+ pr_info("%s: Setting srcu_struct sizes based on contention.\n", __func__);
+ }
+ }
+
+ /*
+ * Once that is set, call_srcu() can follow the normal path and
+ * queue delayed work. This must follow RCU workqueues creation
+ * and timers initialization.
+ */
srcu_init_done = true;
while (!list_empty(&srcu_boot_list)) {
ssp = list_first_entry(&srcu_boot_list, struct srcu_struct,
work.work.entry);
- check_init_srcu_struct(ssp);
list_del_init(&ssp->work.work.entry);
+ if (SRCU_SIZING_IS(SRCU_SIZING_INIT) && ssp->srcu_size_state == SRCU_SIZE_SMALL)
+ ssp->srcu_size_state = SRCU_SIZE_ALLOC;
queue_work(rcu_gp_wq, &ssp->work.work);
}
}
diff --git a/kernel/rcu/sync.c b/kernel/rcu/sync.c
index d4558ab7a07d..5cefc702158f 100644
--- a/kernel/rcu/sync.c
+++ b/kernel/rcu/sync.c
@@ -94,9 +94,9 @@ static void rcu_sync_func(struct rcu_head *rhp)
rcu_sync_call(rsp);
} else {
/*
- * We're at least a GP after the last rcu_sync_exit(); eveybody
+ * We're at least a GP after the last rcu_sync_exit(); everybody
* will now have observed the write side critical section.
- * Let 'em rip!.
+ * Let 'em rip!
*/
WRITE_ONCE(rsp->gp_state, GP_IDLE);
}
@@ -111,7 +111,7 @@ static void rcu_sync_func(struct rcu_head *rhp)
* a slowpath during the update. After this function returns, all
* subsequent calls to rcu_sync_is_idle() will return false, which
* tells readers to stay off their fastpaths. A later call to
- * rcu_sync_exit() re-enables reader slowpaths.
+ * rcu_sync_exit() re-enables reader fastpaths.
*
* When called in isolation, rcu_sync_enter() must wait for a grace
* period, however, closely spaced calls to rcu_sync_enter() can
diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
new file mode 100644
index 000000000000..f5bf6fb430da
--- /dev/null
+++ b/kernel/rcu/tasks.h
@@ -0,0 +1,1914 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Task-based RCU implementations.
+ *
+ * Copyright (C) 2020 Paul E. McKenney
+ */
+
+#ifdef CONFIG_TASKS_RCU_GENERIC
+#include "rcu_segcblist.h"
+
+////////////////////////////////////////////////////////////////////////
+//
+// Generic data structures.
+
+struct rcu_tasks;
+typedef void (*rcu_tasks_gp_func_t)(struct rcu_tasks *rtp);
+typedef void (*pregp_func_t)(struct list_head *hop);
+typedef void (*pertask_func_t)(struct task_struct *t, struct list_head *hop);
+typedef void (*postscan_func_t)(struct list_head *hop);
+typedef void (*holdouts_func_t)(struct list_head *hop, bool ndrpt, bool *frptp);
+typedef void (*postgp_func_t)(struct rcu_tasks *rtp);
+
+/**
+ * struct rcu_tasks_percpu - Per-CPU component of definition for a Tasks-RCU-like mechanism.
+ * @cblist: Callback list.
+ * @lock: Lock protecting per-CPU callback list.
+ * @rtp_jiffies: Jiffies counter value for statistics.
+ * @rtp_n_lock_retries: Rough lock-contention statistic.
+ * @rtp_work: Work queue for invoking callbacks.
+ * @rtp_irq_work: IRQ work queue for deferred wakeups.
+ * @barrier_q_head: RCU callback for barrier operation.
+ * @rtp_blkd_tasks: List of tasks blocked as readers.
+ * @cpu: CPU number corresponding to this entry.
+ * @rtpp: Pointer to the rcu_tasks structure.
+ */
+struct rcu_tasks_percpu {
+ struct rcu_segcblist cblist;
+ raw_spinlock_t __private lock;
+ unsigned long rtp_jiffies;
+ unsigned long rtp_n_lock_retries;
+ struct work_struct rtp_work;
+ struct irq_work rtp_irq_work;
+ struct rcu_head barrier_q_head;
+ struct list_head rtp_blkd_tasks;
+ int cpu;
+ struct rcu_tasks *rtpp;
+};
+
+/**
+ * struct rcu_tasks - Definition for a Tasks-RCU-like mechanism.
+ * @cbs_wait: RCU wait allowing a new callback to get kthread's attention.
+ * @cbs_gbl_lock: Lock protecting callback list.
+ * @tasks_gp_mutex: Mutex protecting grace period, needed during mid-boot dead zone.
+ * @kthread_ptr: This flavor's grace-period/callback-invocation kthread.
+ * @gp_func: This flavor's grace-period-wait function.
+ * @gp_state: Grace period's most recent state transition (debugging).
+ * @gp_sleep: Per-grace-period sleep to prevent CPU-bound looping.
+ * @init_fract: Initial backoff sleep interval.
+ * @gp_jiffies: Time of last @gp_state transition.
+ * @gp_start: Most recent grace-period start in jiffies.
+ * @tasks_gp_seq: Number of grace periods completed since boot.
+ * @n_ipis: Number of IPIs sent to encourage grace periods to end.
+ * @n_ipis_fails: Number of IPI-send failures.
+ * @pregp_func: This flavor's pre-grace-period function (optional).
+ * @pertask_func: This flavor's per-task scan function (optional).
+ * @postscan_func: This flavor's post-task scan function (optional).
+ * @holdouts_func: This flavor's holdout-list scan function (optional).
+ * @postgp_func: This flavor's post-grace-period function (optional).
+ * @call_func: This flavor's call_rcu()-equivalent function.
+ * @rtpcpu: This flavor's rcu_tasks_percpu structure.
+ * @percpu_enqueue_shift: Shift down CPU ID this much when enqueuing callbacks.
+ * @percpu_enqueue_lim: Number of per-CPU callback queues in use for enqueuing.
+ * @percpu_dequeue_lim: Number of per-CPU callback queues in use for dequeuing.
+ * @percpu_dequeue_gpseq: RCU grace-period number to propagate enqueue limit to dequeuers.
+ * @barrier_q_mutex: Serialize barrier operations.
+ * @barrier_q_count: Number of queues being waited on.
+ * @barrier_q_completion: Barrier wait/wakeup mechanism.
+ * @barrier_q_seq: Sequence number for barrier operations.
+ * @name: This flavor's textual name.
+ * @kname: This flavor's kthread name.
+ */
+struct rcu_tasks {
+ struct rcuwait cbs_wait;
+ raw_spinlock_t cbs_gbl_lock;
+ struct mutex tasks_gp_mutex;
+ int gp_state;
+ int gp_sleep;
+ int init_fract;
+ unsigned long gp_jiffies;
+ unsigned long gp_start;
+ unsigned long tasks_gp_seq;
+ unsigned long n_ipis;
+ unsigned long n_ipis_fails;
+ struct task_struct *kthread_ptr;
+ rcu_tasks_gp_func_t gp_func;
+ pregp_func_t pregp_func;
+ pertask_func_t pertask_func;
+ postscan_func_t postscan_func;
+ holdouts_func_t holdouts_func;
+ postgp_func_t postgp_func;
+ call_rcu_func_t call_func;
+ struct rcu_tasks_percpu __percpu *rtpcpu;
+ int percpu_enqueue_shift;
+ int percpu_enqueue_lim;
+ int percpu_dequeue_lim;
+ unsigned long percpu_dequeue_gpseq;
+ struct mutex barrier_q_mutex;
+ atomic_t barrier_q_count;
+ struct completion barrier_q_completion;
+ unsigned long barrier_q_seq;
+ char *name;
+ char *kname;
+};
+
+static void call_rcu_tasks_iw_wakeup(struct irq_work *iwp);
+
+#define DEFINE_RCU_TASKS(rt_name, gp, call, n) \
+static DEFINE_PER_CPU(struct rcu_tasks_percpu, rt_name ## __percpu) = { \
+ .lock = __RAW_SPIN_LOCK_UNLOCKED(rt_name ## __percpu.cbs_pcpu_lock), \
+ .rtp_irq_work = IRQ_WORK_INIT_HARD(call_rcu_tasks_iw_wakeup), \
+}; \
+static struct rcu_tasks rt_name = \
+{ \
+ .cbs_wait = __RCUWAIT_INITIALIZER(rt_name.wait), \
+ .cbs_gbl_lock = __RAW_SPIN_LOCK_UNLOCKED(rt_name.cbs_gbl_lock), \
+ .tasks_gp_mutex = __MUTEX_INITIALIZER(rt_name.tasks_gp_mutex), \
+ .gp_func = gp, \
+ .call_func = call, \
+ .rtpcpu = &rt_name ## __percpu, \
+ .name = n, \
+ .percpu_enqueue_shift = order_base_2(CONFIG_NR_CPUS), \
+ .percpu_enqueue_lim = 1, \
+ .percpu_dequeue_lim = 1, \
+ .barrier_q_mutex = __MUTEX_INITIALIZER(rt_name.barrier_q_mutex), \
+ .barrier_q_seq = (0UL - 50UL) << RCU_SEQ_CTR_SHIFT, \
+ .kname = #rt_name, \
+}
+
+/* Track exiting tasks in order to allow them to be waited for. */
+DEFINE_STATIC_SRCU(tasks_rcu_exit_srcu);
+
+/* Avoid IPIing CPUs early in the grace period. */
+#define RCU_TASK_IPI_DELAY (IS_ENABLED(CONFIG_TASKS_TRACE_RCU_READ_MB) ? HZ / 2 : 0)
+static int rcu_task_ipi_delay __read_mostly = RCU_TASK_IPI_DELAY;
+module_param(rcu_task_ipi_delay, int, 0644);
+
+/* Control stall timeouts. Disable with <= 0, otherwise jiffies till stall. */
+#define RCU_TASK_BOOT_STALL_TIMEOUT (HZ * 30)
+#define RCU_TASK_STALL_TIMEOUT (HZ * 60 * 10)
+static int rcu_task_stall_timeout __read_mostly = RCU_TASK_STALL_TIMEOUT;
+module_param(rcu_task_stall_timeout, int, 0644);
+#define RCU_TASK_STALL_INFO (HZ * 10)
+static int rcu_task_stall_info __read_mostly = RCU_TASK_STALL_INFO;
+module_param(rcu_task_stall_info, int, 0644);
+static int rcu_task_stall_info_mult __read_mostly = 3;
+module_param(rcu_task_stall_info_mult, int, 0444);
+
+static int rcu_task_enqueue_lim __read_mostly = -1;
+module_param(rcu_task_enqueue_lim, int, 0444);
+
+static bool rcu_task_cb_adjust;
+static int rcu_task_contend_lim __read_mostly = 100;
+module_param(rcu_task_contend_lim, int, 0444);
+static int rcu_task_collapse_lim __read_mostly = 10;
+module_param(rcu_task_collapse_lim, int, 0444);
+
+/* RCU tasks grace-period state for debugging. */
+#define RTGS_INIT 0
+#define RTGS_WAIT_WAIT_CBS 1
+#define RTGS_WAIT_GP 2
+#define RTGS_PRE_WAIT_GP 3
+#define RTGS_SCAN_TASKLIST 4
+#define RTGS_POST_SCAN_TASKLIST 5
+#define RTGS_WAIT_SCAN_HOLDOUTS 6
+#define RTGS_SCAN_HOLDOUTS 7
+#define RTGS_POST_GP 8
+#define RTGS_WAIT_READERS 9
+#define RTGS_INVOKE_CBS 10
+#define RTGS_WAIT_CBS 11
+#ifndef CONFIG_TINY_RCU
+static const char * const rcu_tasks_gp_state_names[] = {
+ "RTGS_INIT",
+ "RTGS_WAIT_WAIT_CBS",
+ "RTGS_WAIT_GP",
+ "RTGS_PRE_WAIT_GP",
+ "RTGS_SCAN_TASKLIST",
+ "RTGS_POST_SCAN_TASKLIST",
+ "RTGS_WAIT_SCAN_HOLDOUTS",
+ "RTGS_SCAN_HOLDOUTS",
+ "RTGS_POST_GP",
+ "RTGS_WAIT_READERS",
+ "RTGS_INVOKE_CBS",
+ "RTGS_WAIT_CBS",
+};
+#endif /* #ifndef CONFIG_TINY_RCU */
+
+////////////////////////////////////////////////////////////////////////
+//
+// Generic code.
+
+static void rcu_tasks_invoke_cbs_wq(struct work_struct *wp);
+
+/* Record grace-period phase and time. */
+static void set_tasks_gp_state(struct rcu_tasks *rtp, int newstate)
+{
+ rtp->gp_state = newstate;
+ rtp->gp_jiffies = jiffies;
+}
+
+#ifndef CONFIG_TINY_RCU
+/* Return state name. */
+static const char *tasks_gp_state_getname(struct rcu_tasks *rtp)
+{
+ int i = data_race(rtp->gp_state); // Let KCSAN detect update races
+ int j = READ_ONCE(i); // Prevent the compiler from reading twice
+
+ if (j >= ARRAY_SIZE(rcu_tasks_gp_state_names))
+ return "???";
+ return rcu_tasks_gp_state_names[j];
+}
+#endif /* #ifndef CONFIG_TINY_RCU */
+
+// Initialize per-CPU callback lists for the specified flavor of
+// Tasks RCU.
+static void cblist_init_generic(struct rcu_tasks *rtp)
+{
+ int cpu;
+ unsigned long flags;
+ int lim;
+ int shift;
+
+ raw_spin_lock_irqsave(&rtp->cbs_gbl_lock, flags);
+ if (rcu_task_enqueue_lim < 0) {
+ rcu_task_enqueue_lim = 1;
+ rcu_task_cb_adjust = true;
+ pr_info("%s: Setting adjustable number of callback queues.\n", __func__);
+ } else if (rcu_task_enqueue_lim == 0) {
+ rcu_task_enqueue_lim = 1;
+ }
+ lim = rcu_task_enqueue_lim;
+
+ if (lim > nr_cpu_ids)
+ lim = nr_cpu_ids;
+ shift = ilog2(nr_cpu_ids / lim);
+ if (((nr_cpu_ids - 1) >> shift) >= lim)
+ shift++;
+ WRITE_ONCE(rtp->percpu_enqueue_shift, shift);
+ WRITE_ONCE(rtp->percpu_dequeue_lim, lim);
+ smp_store_release(&rtp->percpu_enqueue_lim, lim);
+ for_each_possible_cpu(cpu) {
+ struct rcu_tasks_percpu *rtpcp = per_cpu_ptr(rtp->rtpcpu, cpu);
+
+ WARN_ON_ONCE(!rtpcp);
+ if (cpu)
+ raw_spin_lock_init(&ACCESS_PRIVATE(rtpcp, lock));
+ raw_spin_lock_rcu_node(rtpcp); // irqs already disabled.
+ if (rcu_segcblist_empty(&rtpcp->cblist))
+ rcu_segcblist_init(&rtpcp->cblist);
+ INIT_WORK(&rtpcp->rtp_work, rcu_tasks_invoke_cbs_wq);
+ rtpcp->cpu = cpu;
+ rtpcp->rtpp = rtp;
+ if (!rtpcp->rtp_blkd_tasks.next)
+ INIT_LIST_HEAD(&rtpcp->rtp_blkd_tasks);
+ raw_spin_unlock_rcu_node(rtpcp); // irqs remain disabled.
+ }
+ raw_spin_unlock_irqrestore(&rtp->cbs_gbl_lock, flags);
+ pr_info("%s: Setting shift to %d and lim to %d.\n", __func__, data_race(rtp->percpu_enqueue_shift), data_race(rtp->percpu_enqueue_lim));
+}
+
+// IRQ-work handler that does deferred wakeup for call_rcu_tasks_generic().
+static void call_rcu_tasks_iw_wakeup(struct irq_work *iwp)
+{
+ struct rcu_tasks *rtp;
+ struct rcu_tasks_percpu *rtpcp = container_of(iwp, struct rcu_tasks_percpu, rtp_irq_work);
+
+ rtp = rtpcp->rtpp;
+ rcuwait_wake_up(&rtp->cbs_wait);
+}
+
+// Enqueue a callback for the specified flavor of Tasks RCU.
+static void call_rcu_tasks_generic(struct rcu_head *rhp, rcu_callback_t func,
+ struct rcu_tasks *rtp)
+{
+ int chosen_cpu;
+ unsigned long flags;
+ int ideal_cpu;
+ unsigned long j;
+ bool needadjust = false;
+ bool needwake;
+ struct rcu_tasks_percpu *rtpcp;
+
+ rhp->next = NULL;
+ rhp->func = func;
+ local_irq_save(flags);
+ rcu_read_lock();
+ ideal_cpu = smp_processor_id() >> READ_ONCE(rtp->percpu_enqueue_shift);
+ chosen_cpu = cpumask_next(ideal_cpu - 1, cpu_possible_mask);
+ rtpcp = per_cpu_ptr(rtp->rtpcpu, chosen_cpu);
+ if (!raw_spin_trylock_rcu_node(rtpcp)) { // irqs already disabled.
+ raw_spin_lock_rcu_node(rtpcp); // irqs already disabled.
+ j = jiffies;
+ if (rtpcp->rtp_jiffies != j) {
+ rtpcp->rtp_jiffies = j;
+ rtpcp->rtp_n_lock_retries = 0;
+ }
+ if (rcu_task_cb_adjust && ++rtpcp->rtp_n_lock_retries > rcu_task_contend_lim &&
+ READ_ONCE(rtp->percpu_enqueue_lim) != nr_cpu_ids)
+ needadjust = true; // Defer adjustment to avoid deadlock.
+ }
+ if (!rcu_segcblist_is_enabled(&rtpcp->cblist)) {
+ raw_spin_unlock_rcu_node(rtpcp); // irqs remain disabled.
+ cblist_init_generic(rtp);
+ raw_spin_lock_rcu_node(rtpcp); // irqs already disabled.
+ }
+ needwake = rcu_segcblist_empty(&rtpcp->cblist);
+ rcu_segcblist_enqueue(&rtpcp->cblist, rhp);
+ raw_spin_unlock_irqrestore_rcu_node(rtpcp, flags);
+ if (unlikely(needadjust)) {
+ raw_spin_lock_irqsave(&rtp->cbs_gbl_lock, flags);
+ if (rtp->percpu_enqueue_lim != nr_cpu_ids) {
+ WRITE_ONCE(rtp->percpu_enqueue_shift, 0);
+ WRITE_ONCE(rtp->percpu_dequeue_lim, nr_cpu_ids);
+ smp_store_release(&rtp->percpu_enqueue_lim, nr_cpu_ids);
+ pr_info("Switching %s to per-CPU callback queuing.\n", rtp->name);
+ }
+ raw_spin_unlock_irqrestore(&rtp->cbs_gbl_lock, flags);
+ }
+ rcu_read_unlock();
+ /* We can't create the thread unless interrupts are enabled. */
+ if (needwake && READ_ONCE(rtp->kthread_ptr))
+ irq_work_queue(&rtpcp->rtp_irq_work);
+}
+
+// RCU callback function for rcu_barrier_tasks_generic().
+static void rcu_barrier_tasks_generic_cb(struct rcu_head *rhp)
+{
+ struct rcu_tasks *rtp;
+ struct rcu_tasks_percpu *rtpcp;
+
+ rtpcp = container_of(rhp, struct rcu_tasks_percpu, barrier_q_head);
+ rtp = rtpcp->rtpp;
+ if (atomic_dec_and_test(&rtp->barrier_q_count))
+ complete(&rtp->barrier_q_completion);
+}
+
+// Wait for all in-flight callbacks for the specified RCU Tasks flavor.
+// Operates in a manner similar to rcu_barrier().
+static void rcu_barrier_tasks_generic(struct rcu_tasks *rtp)
+{
+ int cpu;
+ unsigned long flags;
+ struct rcu_tasks_percpu *rtpcp;
+ unsigned long s = rcu_seq_snap(&rtp->barrier_q_seq);
+
+ mutex_lock(&rtp->barrier_q_mutex);
+ if (rcu_seq_done(&rtp->barrier_q_seq, s)) {
+ smp_mb();
+ mutex_unlock(&rtp->barrier_q_mutex);
+ return;
+ }
+ rcu_seq_start(&rtp->barrier_q_seq);
+ init_completion(&rtp->barrier_q_completion);
+ atomic_set(&rtp->barrier_q_count, 2);
+ for_each_possible_cpu(cpu) {
+ if (cpu >= smp_load_acquire(&rtp->percpu_dequeue_lim))
+ break;
+ rtpcp = per_cpu_ptr(rtp->rtpcpu, cpu);
+ rtpcp->barrier_q_head.func = rcu_barrier_tasks_generic_cb;
+ raw_spin_lock_irqsave_rcu_node(rtpcp, flags);
+ if (rcu_segcblist_entrain(&rtpcp->cblist, &rtpcp->barrier_q_head))
+ atomic_inc(&rtp->barrier_q_count);
+ raw_spin_unlock_irqrestore_rcu_node(rtpcp, flags);
+ }
+ if (atomic_sub_and_test(2, &rtp->barrier_q_count))
+ complete(&rtp->barrier_q_completion);
+ wait_for_completion(&rtp->barrier_q_completion);
+ rcu_seq_end(&rtp->barrier_q_seq);
+ mutex_unlock(&rtp->barrier_q_mutex);
+}
+
+// Advance callbacks and indicate whether either a grace period or
+// callback invocation is needed.
+static int rcu_tasks_need_gpcb(struct rcu_tasks *rtp)
+{
+ int cpu;
+ unsigned long flags;
+ long n;
+ long ncbs = 0;
+ long ncbsnz = 0;
+ int needgpcb = 0;
+
+ for (cpu = 0; cpu < smp_load_acquire(&rtp->percpu_dequeue_lim); cpu++) {
+ struct rcu_tasks_percpu *rtpcp = per_cpu_ptr(rtp->rtpcpu, cpu);
+
+ /* Advance and accelerate any new callbacks. */
+ if (!rcu_segcblist_n_cbs(&rtpcp->cblist))
+ continue;
+ raw_spin_lock_irqsave_rcu_node(rtpcp, flags);
+ // Should we shrink down to a single callback queue?
+ n = rcu_segcblist_n_cbs(&rtpcp->cblist);
+ if (n) {
+ ncbs += n;
+ if (cpu > 0)
+ ncbsnz += n;
+ }
+ rcu_segcblist_advance(&rtpcp->cblist, rcu_seq_current(&rtp->tasks_gp_seq));
+ (void)rcu_segcblist_accelerate(&rtpcp->cblist, rcu_seq_snap(&rtp->tasks_gp_seq));
+ if (rcu_segcblist_pend_cbs(&rtpcp->cblist))
+ needgpcb |= 0x3;
+ if (!rcu_segcblist_empty(&rtpcp->cblist))
+ needgpcb |= 0x1;
+ raw_spin_unlock_irqrestore_rcu_node(rtpcp, flags);
+ }
+
+ // Shrink down to a single callback queue if appropriate.
+ // This is done in two stages: (1) If there are no more than
+ // rcu_task_collapse_lim callbacks on CPU 0 and none on any other
+ // CPU, limit enqueueing to CPU 0. (2) After an RCU grace period,
+ // if there has not been an increase in callbacks, limit dequeuing
+ // to CPU 0. Note the matching RCU read-side critical section in
+ // call_rcu_tasks_generic().
+ if (rcu_task_cb_adjust && ncbs <= rcu_task_collapse_lim) {
+ raw_spin_lock_irqsave(&rtp->cbs_gbl_lock, flags);
+ if (rtp->percpu_enqueue_lim > 1) {
+ WRITE_ONCE(rtp->percpu_enqueue_shift, order_base_2(nr_cpu_ids));
+ smp_store_release(&rtp->percpu_enqueue_lim, 1);
+ rtp->percpu_dequeue_gpseq = get_state_synchronize_rcu();
+ pr_info("Starting switch %s to CPU-0 callback queuing.\n", rtp->name);
+ }
+ raw_spin_unlock_irqrestore(&rtp->cbs_gbl_lock, flags);
+ }
+ if (rcu_task_cb_adjust && !ncbsnz &&
+ poll_state_synchronize_rcu(rtp->percpu_dequeue_gpseq)) {
+ raw_spin_lock_irqsave(&rtp->cbs_gbl_lock, flags);
+ if (rtp->percpu_enqueue_lim < rtp->percpu_dequeue_lim) {
+ WRITE_ONCE(rtp->percpu_dequeue_lim, 1);
+ pr_info("Completing switch %s to CPU-0 callback queuing.\n", rtp->name);
+ }
+ for (cpu = rtp->percpu_dequeue_lim; cpu < nr_cpu_ids; cpu++) {
+ struct rcu_tasks_percpu *rtpcp = per_cpu_ptr(rtp->rtpcpu, cpu);
+
+ WARN_ON_ONCE(rcu_segcblist_n_cbs(&rtpcp->cblist));
+ }
+ raw_spin_unlock_irqrestore(&rtp->cbs_gbl_lock, flags);
+ }
+
+ return needgpcb;
+}
+
+// Advance callbacks and invoke any that are ready.
+static void rcu_tasks_invoke_cbs(struct rcu_tasks *rtp, struct rcu_tasks_percpu *rtpcp)
+{
+ int cpu;
+ int cpunext;
+ unsigned long flags;
+ int len;
+ struct rcu_head *rhp;
+ struct rcu_cblist rcl = RCU_CBLIST_INITIALIZER(rcl);
+ struct rcu_tasks_percpu *rtpcp_next;
+
+ cpu = rtpcp->cpu;
+ cpunext = cpu * 2 + 1;
+ if (cpunext < smp_load_acquire(&rtp->percpu_dequeue_lim)) {
+ rtpcp_next = per_cpu_ptr(rtp->rtpcpu, cpunext);
+ queue_work_on(cpunext, system_wq, &rtpcp_next->rtp_work);
+ cpunext++;
+ if (cpunext < smp_load_acquire(&rtp->percpu_dequeue_lim)) {
+ rtpcp_next = per_cpu_ptr(rtp->rtpcpu, cpunext);
+ queue_work_on(cpunext, system_wq, &rtpcp_next->rtp_work);
+ }
+ }
+
+ if (rcu_segcblist_empty(&rtpcp->cblist) || !cpu_possible(cpu))
+ return;
+ raw_spin_lock_irqsave_rcu_node(rtpcp, flags);
+ rcu_segcblist_advance(&rtpcp->cblist, rcu_seq_current(&rtp->tasks_gp_seq));
+ rcu_segcblist_extract_done_cbs(&rtpcp->cblist, &rcl);
+ raw_spin_unlock_irqrestore_rcu_node(rtpcp, flags);
+ len = rcl.len;
+ for (rhp = rcu_cblist_dequeue(&rcl); rhp; rhp = rcu_cblist_dequeue(&rcl)) {
+ local_bh_disable();
+ rhp->func(rhp);
+ local_bh_enable();
+ cond_resched();
+ }
+ raw_spin_lock_irqsave_rcu_node(rtpcp, flags);
+ rcu_segcblist_add_len(&rtpcp->cblist, -len);
+ (void)rcu_segcblist_accelerate(&rtpcp->cblist, rcu_seq_snap(&rtp->tasks_gp_seq));
+ raw_spin_unlock_irqrestore_rcu_node(rtpcp, flags);
+}
+
+// Workqueue flood to advance callbacks and invoke any that are ready.
+static void rcu_tasks_invoke_cbs_wq(struct work_struct *wp)
+{
+ struct rcu_tasks *rtp;
+ struct rcu_tasks_percpu *rtpcp = container_of(wp, struct rcu_tasks_percpu, rtp_work);
+
+ rtp = rtpcp->rtpp;
+ rcu_tasks_invoke_cbs(rtp, rtpcp);
+}
+
+// Wait for one grace period.
+static void rcu_tasks_one_gp(struct rcu_tasks *rtp, bool midboot)
+{
+ int needgpcb;
+
+ mutex_lock(&rtp->tasks_gp_mutex);
+
+ // If there were none, wait a bit and start over.
+ if (unlikely(midboot)) {
+ needgpcb = 0x2;
+ } else {
+ set_tasks_gp_state(rtp, RTGS_WAIT_CBS);
+ rcuwait_wait_event(&rtp->cbs_wait,
+ (needgpcb = rcu_tasks_need_gpcb(rtp)),
+ TASK_IDLE);
+ }
+
+ if (needgpcb & 0x2) {
+ // Wait for one grace period.
+ set_tasks_gp_state(rtp, RTGS_WAIT_GP);
+ rtp->gp_start = jiffies;
+ rcu_seq_start(&rtp->tasks_gp_seq);
+ rtp->gp_func(rtp);
+ rcu_seq_end(&rtp->tasks_gp_seq);
+ }
+
+ // Invoke callbacks.
+ set_tasks_gp_state(rtp, RTGS_INVOKE_CBS);
+ rcu_tasks_invoke_cbs(rtp, per_cpu_ptr(rtp->rtpcpu, 0));
+ mutex_unlock(&rtp->tasks_gp_mutex);
+}
+
+// RCU-tasks kthread that detects grace periods and invokes callbacks.
+static int __noreturn rcu_tasks_kthread(void *arg)
+{
+ struct rcu_tasks *rtp = arg;
+
+ /* Run on housekeeping CPUs by default. Sysadm can move if desired. */
+ housekeeping_affine(current, HK_TYPE_RCU);
+ WRITE_ONCE(rtp->kthread_ptr, current); // Let GPs start!
+
+ /*
+ * Each pass through the following loop makes one check for
+ * newly arrived callbacks, and, if there are some, waits for
+ * one RCU-tasks grace period and then invokes the callbacks.
+ * This loop is terminated by the system going down. ;-)
+ */
+ for (;;) {
+ // Wait for one grace period and invoke any callbacks
+ // that are ready.
+ rcu_tasks_one_gp(rtp, false);
+
+ // Paranoid sleep to keep this from entering a tight loop.
+ schedule_timeout_idle(rtp->gp_sleep);
+ }
+}
+
+// Wait for a grace period for the specified flavor of Tasks RCU.
+static void synchronize_rcu_tasks_generic(struct rcu_tasks *rtp)
+{
+ /* Complain if the scheduler has not started. */
+ WARN_ONCE(rcu_scheduler_active == RCU_SCHEDULER_INACTIVE,
+ "synchronize_rcu_tasks called too soon");
+
+ // If the grace-period kthread is running, use it.
+ if (READ_ONCE(rtp->kthread_ptr)) {
+ wait_rcu_gp(rtp->call_func);
+ return;
+ }
+ rcu_tasks_one_gp(rtp, true);
+}
+
+/* Spawn RCU-tasks grace-period kthread. */
+static void __init rcu_spawn_tasks_kthread_generic(struct rcu_tasks *rtp)
+{
+ struct task_struct *t;
+
+ t = kthread_run(rcu_tasks_kthread, rtp, "%s_kthread", rtp->kname);
+ if (WARN_ONCE(IS_ERR(t), "%s: Could not start %s grace-period kthread, OOM is now expected behavior\n", __func__, rtp->name))
+ return;
+ smp_mb(); /* Ensure others see full kthread. */
+}
+
+#ifndef CONFIG_TINY_RCU
+
+/*
+ * Print any non-default Tasks RCU settings.
+ */
+static void __init rcu_tasks_bootup_oddness(void)
+{
+#if defined(CONFIG_TASKS_RCU) || defined(CONFIG_TASKS_TRACE_RCU)
+ int rtsimc;
+
+ if (rcu_task_stall_timeout != RCU_TASK_STALL_TIMEOUT)
+ pr_info("\tTasks-RCU CPU stall warnings timeout set to %d (rcu_task_stall_timeout).\n", rcu_task_stall_timeout);
+ rtsimc = clamp(rcu_task_stall_info_mult, 1, 10);
+ if (rtsimc != rcu_task_stall_info_mult) {
+ pr_info("\tTasks-RCU CPU stall info multiplier clamped to %d (rcu_task_stall_info_mult).\n", rtsimc);
+ rcu_task_stall_info_mult = rtsimc;
+ }
+#endif /* #ifdef CONFIG_TASKS_RCU */
+#ifdef CONFIG_TASKS_RCU
+ pr_info("\tTrampoline variant of Tasks RCU enabled.\n");
+#endif /* #ifdef CONFIG_TASKS_RCU */
+#ifdef CONFIG_TASKS_RUDE_RCU
+ pr_info("\tRude variant of Tasks RCU enabled.\n");
+#endif /* #ifdef CONFIG_TASKS_RUDE_RCU */
+#ifdef CONFIG_TASKS_TRACE_RCU
+ pr_info("\tTracing variant of Tasks RCU enabled.\n");
+#endif /* #ifdef CONFIG_TASKS_TRACE_RCU */
+}
+
+#endif /* #ifndef CONFIG_TINY_RCU */
+
+#ifndef CONFIG_TINY_RCU
+/* Dump out rcutorture-relevant state common to all RCU-tasks flavors. */
+static void show_rcu_tasks_generic_gp_kthread(struct rcu_tasks *rtp, char *s)
+{
+ int cpu;
+ bool havecbs = false;
+
+ for_each_possible_cpu(cpu) {
+ struct rcu_tasks_percpu *rtpcp = per_cpu_ptr(rtp->rtpcpu, cpu);
+
+ if (!data_race(rcu_segcblist_empty(&rtpcp->cblist))) {
+ havecbs = true;
+ break;
+ }
+ }
+ pr_info("%s: %s(%d) since %lu g:%lu i:%lu/%lu %c%c %s\n",
+ rtp->kname,
+ tasks_gp_state_getname(rtp), data_race(rtp->gp_state),
+ jiffies - data_race(rtp->gp_jiffies),
+ data_race(rcu_seq_current(&rtp->tasks_gp_seq)),
+ data_race(rtp->n_ipis_fails), data_race(rtp->n_ipis),
+ ".k"[!!data_race(rtp->kthread_ptr)],
+ ".C"[havecbs],
+ s);
+}
+#endif // #ifndef CONFIG_TINY_RCU
+
+static void exit_tasks_rcu_finish_trace(struct task_struct *t);
+
+#if defined(CONFIG_TASKS_RCU) || defined(CONFIG_TASKS_TRACE_RCU)
+
+////////////////////////////////////////////////////////////////////////
+//
+// Shared code between task-list-scanning variants of Tasks RCU.
+
+/* Wait for one RCU-tasks grace period. */
+static void rcu_tasks_wait_gp(struct rcu_tasks *rtp)
+{
+ struct task_struct *g;
+ int fract;
+ LIST_HEAD(holdouts);
+ unsigned long j;
+ unsigned long lastinfo;
+ unsigned long lastreport;
+ bool reported = false;
+ int rtsi;
+ struct task_struct *t;
+
+ set_tasks_gp_state(rtp, RTGS_PRE_WAIT_GP);
+ rtp->pregp_func(&holdouts);
+
+ /*
+ * There were callbacks, so we need to wait for an RCU-tasks
+ * grace period. Start off by scanning the task list for tasks
+ * that are not already voluntarily blocked. Mark these tasks
+ * and make a list of them in holdouts.
+ */
+ set_tasks_gp_state(rtp, RTGS_SCAN_TASKLIST);
+ if (rtp->pertask_func) {
+ rcu_read_lock();
+ for_each_process_thread(g, t)
+ rtp->pertask_func(t, &holdouts);
+ rcu_read_unlock();
+ }
+
+ set_tasks_gp_state(rtp, RTGS_POST_SCAN_TASKLIST);
+ rtp->postscan_func(&holdouts);
+
+ /*
+ * Each pass through the following loop scans the list of holdout
+ * tasks, removing any that are no longer holdouts. When the list
+ * is empty, we are done.
+ */
+ lastreport = jiffies;
+ lastinfo = lastreport;
+ rtsi = READ_ONCE(rcu_task_stall_info);
+
+ // Start off with initial wait and slowly back off to 1 HZ wait.
+ fract = rtp->init_fract;
+
+ while (!list_empty(&holdouts)) {
+ ktime_t exp;
+ bool firstreport;
+ bool needreport;
+ int rtst;
+
+ // Slowly back off waiting for holdouts
+ set_tasks_gp_state(rtp, RTGS_WAIT_SCAN_HOLDOUTS);
+ if (!IS_ENABLED(CONFIG_PREEMPT_RT)) {
+ schedule_timeout_idle(fract);
+ } else {
+ exp = jiffies_to_nsecs(fract);
+ __set_current_state(TASK_IDLE);
+ schedule_hrtimeout_range(&exp, jiffies_to_nsecs(HZ / 2), HRTIMER_MODE_REL_HARD);
+ }
+
+ if (fract < HZ)
+ fract++;
+
+ rtst = READ_ONCE(rcu_task_stall_timeout);
+ needreport = rtst > 0 && time_after(jiffies, lastreport + rtst);
+ if (needreport) {
+ lastreport = jiffies;
+ reported = true;
+ }
+ firstreport = true;
+ WARN_ON(signal_pending(current));
+ set_tasks_gp_state(rtp, RTGS_SCAN_HOLDOUTS);
+ rtp->holdouts_func(&holdouts, needreport, &firstreport);
+
+ // Print pre-stall informational messages if needed.
+ j = jiffies;
+ if (rtsi > 0 && !reported && time_after(j, lastinfo + rtsi)) {
+ lastinfo = j;
+ rtsi = rtsi * rcu_task_stall_info_mult;
+ pr_info("%s: %s grace period %lu is %lu jiffies old.\n",
+ __func__, rtp->kname, rtp->tasks_gp_seq, j - rtp->gp_start);
+ }
+ }
+
+ set_tasks_gp_state(rtp, RTGS_POST_GP);
+ rtp->postgp_func(rtp);
+}
+
+#endif /* #if defined(CONFIG_TASKS_RCU) || defined(CONFIG_TASKS_TRACE_RCU) */
+
+#ifdef CONFIG_TASKS_RCU
+
+////////////////////////////////////////////////////////////////////////
+//
+// Simple variant of RCU whose quiescent states are voluntary context
+// switch, cond_resched_tasks_rcu_qs(), user-space execution, and idle.
+// As such, grace periods can take one good long time. There are no
+// read-side primitives similar to rcu_read_lock() and rcu_read_unlock()
+// because this implementation is intended to get the system into a safe
+// state for some of the manipulations involved in tracing and the like.
+// Finally, this implementation does not support high call_rcu_tasks()
+// rates from multiple CPUs. If this is required, per-CPU callback lists
+// will be needed.
+//
+// The implementation uses rcu_tasks_wait_gp(), which relies on function
+// pointers in the rcu_tasks structure. The rcu_spawn_tasks_kthread()
+// function sets these function pointers up so that rcu_tasks_wait_gp()
+// invokes these functions in this order:
+//
+// rcu_tasks_pregp_step():
+// Invokes synchronize_rcu() in order to wait for all in-flight
+// t->on_rq and t->nvcsw transitions to complete. This works because
+// all such transitions are carried out with interrupts disabled.
+// rcu_tasks_pertask(), invoked on every non-idle task:
+// For every runnable non-idle task other than the current one, use
+// get_task_struct() to pin down that task, snapshot that task's
+// number of voluntary context switches, and add that task to the
+// holdout list.
+// rcu_tasks_postscan():
+// Invoke synchronize_srcu() to ensure that all tasks that were
+// in the process of exiting (and which thus might not know to
+// synchronize with this RCU Tasks grace period) have completed
+// exiting.
+// check_all_holdout_tasks(), repeatedly until holdout list is empty:
+// Scans the holdout list, attempting to identify a quiescent state
+// for each task on the list. If there is a quiescent state, the
+// corresponding task is removed from the holdout list.
+// rcu_tasks_postgp():
+// Invokes synchronize_rcu() in order to ensure that all prior
+// t->on_rq and t->nvcsw transitions are seen by all CPUs and tasks
+// to have happened before the end of this RCU Tasks grace period.
+// Again, this works because all such transitions are carried out
+// with interrupts disabled.
+//
+// For each exiting task, the exit_tasks_rcu_start() and
+// exit_tasks_rcu_finish() functions begin and end, respectively, the SRCU
+// read-side critical sections waited for by rcu_tasks_postscan().
+//
+// Pre-grace-period update-side code is ordered before the grace
+// via the raw_spin_lock.*rcu_node(). Pre-grace-period read-side code
+// is ordered before the grace period via synchronize_rcu() call in
+// rcu_tasks_pregp_step() and by the scheduler's locks and interrupt
+// disabling.
+
+/* Pre-grace-period preparation. */
+static void rcu_tasks_pregp_step(struct list_head *hop)
+{
+ /*
+ * Wait for all pre-existing t->on_rq and t->nvcsw transitions
+ * to complete. Invoking synchronize_rcu() suffices because all
+ * these transitions occur with interrupts disabled. Without this
+ * synchronize_rcu(), a read-side critical section that started
+ * before the grace period might be incorrectly seen as having
+ * started after the grace period.
+ *
+ * This synchronize_rcu() also dispenses with the need for a
+ * memory barrier on the first store to t->rcu_tasks_holdout,
+ * as it forces the store to happen after the beginning of the
+ * grace period.
+ */
+ synchronize_rcu();
+}
+
+/* Per-task initial processing. */
+static void rcu_tasks_pertask(struct task_struct *t, struct list_head *hop)
+{
+ if (t != current && READ_ONCE(t->on_rq) && !is_idle_task(t)) {
+ get_task_struct(t);
+ t->rcu_tasks_nvcsw = READ_ONCE(t->nvcsw);
+ WRITE_ONCE(t->rcu_tasks_holdout, true);
+ list_add(&t->rcu_tasks_holdout_list, hop);
+ }
+}
+
+/* Processing between scanning taskslist and draining the holdout list. */
+static void rcu_tasks_postscan(struct list_head *hop)
+{
+ /*
+ * Wait for tasks that are in the process of exiting. This
+ * does only part of the job, ensuring that all tasks that were
+ * previously exiting reach the point where they have disabled
+ * preemption, allowing the later synchronize_rcu() to finish
+ * the job.
+ */
+ synchronize_srcu(&tasks_rcu_exit_srcu);
+}
+
+/* See if tasks are still holding out, complain if so. */
+static void check_holdout_task(struct task_struct *t,
+ bool needreport, bool *firstreport)
+{
+ int cpu;
+
+ if (!READ_ONCE(t->rcu_tasks_holdout) ||
+ t->rcu_tasks_nvcsw != READ_ONCE(t->nvcsw) ||
+ !READ_ONCE(t->on_rq) ||
+ (IS_ENABLED(CONFIG_NO_HZ_FULL) &&
+ !is_idle_task(t) && t->rcu_tasks_idle_cpu >= 0)) {
+ WRITE_ONCE(t->rcu_tasks_holdout, false);
+ list_del_init(&t->rcu_tasks_holdout_list);
+ put_task_struct(t);
+ return;
+ }
+ rcu_request_urgent_qs_task(t);
+ if (!needreport)
+ return;
+ if (*firstreport) {
+ pr_err("INFO: rcu_tasks detected stalls on tasks:\n");
+ *firstreport = false;
+ }
+ cpu = task_cpu(t);
+ pr_alert("%p: %c%c nvcsw: %lu/%lu holdout: %d idle_cpu: %d/%d\n",
+ t, ".I"[is_idle_task(t)],
+ "N."[cpu < 0 || !tick_nohz_full_cpu(cpu)],
+ t->rcu_tasks_nvcsw, t->nvcsw, t->rcu_tasks_holdout,
+ t->rcu_tasks_idle_cpu, cpu);
+ sched_show_task(t);
+}
+
+/* Scan the holdout lists for tasks no longer holding out. */
+static void check_all_holdout_tasks(struct list_head *hop,
+ bool needreport, bool *firstreport)
+{
+ struct task_struct *t, *t1;
+
+ list_for_each_entry_safe(t, t1, hop, rcu_tasks_holdout_list) {
+ check_holdout_task(t, needreport, firstreport);
+ cond_resched();
+ }
+}
+
+/* Finish off the Tasks-RCU grace period. */
+static void rcu_tasks_postgp(struct rcu_tasks *rtp)
+{
+ /*
+ * Because ->on_rq and ->nvcsw are not guaranteed to have a full
+ * memory barriers prior to them in the schedule() path, memory
+ * reordering on other CPUs could cause their RCU-tasks read-side
+ * critical sections to extend past the end of the grace period.
+ * However, because these ->nvcsw updates are carried out with
+ * interrupts disabled, we can use synchronize_rcu() to force the
+ * needed ordering on all such CPUs.
+ *
+ * This synchronize_rcu() also confines all ->rcu_tasks_holdout
+ * accesses to be within the grace period, avoiding the need for
+ * memory barriers for ->rcu_tasks_holdout accesses.
+ *
+ * In addition, this synchronize_rcu() waits for exiting tasks
+ * to complete their final preempt_disable() region of execution,
+ * cleaning up after the synchronize_srcu() above.
+ */
+ synchronize_rcu();
+}
+
+void call_rcu_tasks(struct rcu_head *rhp, rcu_callback_t func);
+DEFINE_RCU_TASKS(rcu_tasks, rcu_tasks_wait_gp, call_rcu_tasks, "RCU Tasks");
+
+/**
+ * call_rcu_tasks() - Queue an RCU for invocation task-based grace period
+ * @rhp: structure to be used for queueing the RCU updates.
+ * @func: actual callback function to be invoked after the grace period
+ *
+ * The callback function will be invoked some time after a full grace
+ * period elapses, in other words after all currently executing RCU
+ * read-side critical sections have completed. call_rcu_tasks() assumes
+ * that the read-side critical sections end at a voluntary context
+ * switch (not a preemption!), cond_resched_tasks_rcu_qs(), entry into idle,
+ * or transition to usermode execution. As such, there are no read-side
+ * primitives analogous to rcu_read_lock() and rcu_read_unlock() because
+ * this primitive is intended to determine that all tasks have passed
+ * through a safe state, not so much for data-structure synchronization.
+ *
+ * See the description of call_rcu() for more detailed information on
+ * memory ordering guarantees.
+ */
+void call_rcu_tasks(struct rcu_head *rhp, rcu_callback_t func)
+{
+ call_rcu_tasks_generic(rhp, func, &rcu_tasks);
+}
+EXPORT_SYMBOL_GPL(call_rcu_tasks);
+
+/**
+ * synchronize_rcu_tasks - wait until an rcu-tasks grace period has elapsed.
+ *
+ * Control will return to the caller some time after a full rcu-tasks
+ * grace period has elapsed, in other words after all currently
+ * executing rcu-tasks read-side critical sections have elapsed. These
+ * read-side critical sections are delimited by calls to schedule(),
+ * cond_resched_tasks_rcu_qs(), idle execution, userspace execution, calls
+ * to synchronize_rcu_tasks(), and (in theory, anyway) cond_resched().
+ *
+ * This is a very specialized primitive, intended only for a few uses in
+ * tracing and other situations requiring manipulation of function
+ * preambles and profiling hooks. The synchronize_rcu_tasks() function
+ * is not (yet) intended for heavy use from multiple CPUs.
+ *
+ * See the description of synchronize_rcu() for more detailed information
+ * on memory ordering guarantees.
+ */
+void synchronize_rcu_tasks(void)
+{
+ synchronize_rcu_tasks_generic(&rcu_tasks);
+}
+EXPORT_SYMBOL_GPL(synchronize_rcu_tasks);
+
+/**
+ * rcu_barrier_tasks - Wait for in-flight call_rcu_tasks() callbacks.
+ *
+ * Although the current implementation is guaranteed to wait, it is not
+ * obligated to, for example, if there are no pending callbacks.
+ */
+void rcu_barrier_tasks(void)
+{
+ rcu_barrier_tasks_generic(&rcu_tasks);
+}
+EXPORT_SYMBOL_GPL(rcu_barrier_tasks);
+
+static int __init rcu_spawn_tasks_kthread(void)
+{
+ cblist_init_generic(&rcu_tasks);
+ rcu_tasks.gp_sleep = HZ / 10;
+ rcu_tasks.init_fract = HZ / 10;
+ rcu_tasks.pregp_func = rcu_tasks_pregp_step;
+ rcu_tasks.pertask_func = rcu_tasks_pertask;
+ rcu_tasks.postscan_func = rcu_tasks_postscan;
+ rcu_tasks.holdouts_func = check_all_holdout_tasks;
+ rcu_tasks.postgp_func = rcu_tasks_postgp;
+ rcu_spawn_tasks_kthread_generic(&rcu_tasks);
+ return 0;
+}
+
+#if !defined(CONFIG_TINY_RCU)
+void show_rcu_tasks_classic_gp_kthread(void)
+{
+ show_rcu_tasks_generic_gp_kthread(&rcu_tasks, "");
+}
+EXPORT_SYMBOL_GPL(show_rcu_tasks_classic_gp_kthread);
+#endif // !defined(CONFIG_TINY_RCU)
+
+/* Do the srcu_read_lock() for the above synchronize_srcu(). */
+void exit_tasks_rcu_start(void) __acquires(&tasks_rcu_exit_srcu)
+{
+ preempt_disable();
+ current->rcu_tasks_idx = __srcu_read_lock(&tasks_rcu_exit_srcu);
+ preempt_enable();
+}
+
+/* Do the srcu_read_unlock() for the above synchronize_srcu(). */
+void exit_tasks_rcu_finish(void) __releases(&tasks_rcu_exit_srcu)
+{
+ struct task_struct *t = current;
+
+ preempt_disable();
+ __srcu_read_unlock(&tasks_rcu_exit_srcu, t->rcu_tasks_idx);
+ preempt_enable();
+ exit_tasks_rcu_finish_trace(t);
+}
+
+#else /* #ifdef CONFIG_TASKS_RCU */
+void exit_tasks_rcu_start(void) { }
+void exit_tasks_rcu_finish(void) { exit_tasks_rcu_finish_trace(current); }
+#endif /* #else #ifdef CONFIG_TASKS_RCU */
+
+#ifdef CONFIG_TASKS_RUDE_RCU
+
+////////////////////////////////////////////////////////////////////////
+//
+// "Rude" variant of Tasks RCU, inspired by Steve Rostedt's trick of
+// passing an empty function to schedule_on_each_cpu(). This approach
+// provides an asynchronous call_rcu_tasks_rude() API and batching of
+// concurrent calls to the synchronous synchronize_rcu_tasks_rude() API.
+// This invokes schedule_on_each_cpu() in order to send IPIs far and wide
+// and induces otherwise unnecessary context switches on all online CPUs,
+// whether idle or not.
+//
+// Callback handling is provided by the rcu_tasks_kthread() function.
+//
+// Ordering is provided by the scheduler's context-switch code.
+
+// Empty function to allow workqueues to force a context switch.
+static void rcu_tasks_be_rude(struct work_struct *work)
+{
+}
+
+// Wait for one rude RCU-tasks grace period.
+static void rcu_tasks_rude_wait_gp(struct rcu_tasks *rtp)
+{
+ if (num_online_cpus() <= 1)
+ return; // Fastpath for only one CPU.
+
+ rtp->n_ipis += cpumask_weight(cpu_online_mask);
+ schedule_on_each_cpu(rcu_tasks_be_rude);
+}
+
+void call_rcu_tasks_rude(struct rcu_head *rhp, rcu_callback_t func);
+DEFINE_RCU_TASKS(rcu_tasks_rude, rcu_tasks_rude_wait_gp, call_rcu_tasks_rude,
+ "RCU Tasks Rude");
+
+/**
+ * call_rcu_tasks_rude() - Queue a callback rude task-based grace period
+ * @rhp: structure to be used for queueing the RCU updates.
+ * @func: actual callback function to be invoked after the grace period
+ *
+ * The callback function will be invoked some time after a full grace
+ * period elapses, in other words after all currently executing RCU
+ * read-side critical sections have completed. call_rcu_tasks_rude()
+ * assumes that the read-side critical sections end at context switch,
+ * cond_resched_tasks_rcu_qs(), or transition to usermode execution (as
+ * usermode execution is schedulable). As such, there are no read-side
+ * primitives analogous to rcu_read_lock() and rcu_read_unlock() because
+ * this primitive is intended to determine that all tasks have passed
+ * through a safe state, not so much for data-structure synchronization.
+ *
+ * See the description of call_rcu() for more detailed information on
+ * memory ordering guarantees.
+ */
+void call_rcu_tasks_rude(struct rcu_head *rhp, rcu_callback_t func)
+{
+ call_rcu_tasks_generic(rhp, func, &rcu_tasks_rude);
+}
+EXPORT_SYMBOL_GPL(call_rcu_tasks_rude);
+
+/**
+ * synchronize_rcu_tasks_rude - wait for a rude rcu-tasks grace period
+ *
+ * Control will return to the caller some time after a rude rcu-tasks
+ * grace period has elapsed, in other words after all currently
+ * executing rcu-tasks read-side critical sections have elapsed. These
+ * read-side critical sections are delimited by calls to schedule(),
+ * cond_resched_tasks_rcu_qs(), userspace execution (which is a schedulable
+ * context), and (in theory, anyway) cond_resched().
+ *
+ * This is a very specialized primitive, intended only for a few uses in
+ * tracing and other situations requiring manipulation of function preambles
+ * and profiling hooks. The synchronize_rcu_tasks_rude() function is not
+ * (yet) intended for heavy use from multiple CPUs.
+ *
+ * See the description of synchronize_rcu() for more detailed information
+ * on memory ordering guarantees.
+ */
+void synchronize_rcu_tasks_rude(void)
+{
+ synchronize_rcu_tasks_generic(&rcu_tasks_rude);
+}
+EXPORT_SYMBOL_GPL(synchronize_rcu_tasks_rude);
+
+/**
+ * rcu_barrier_tasks_rude - Wait for in-flight call_rcu_tasks_rude() callbacks.
+ *
+ * Although the current implementation is guaranteed to wait, it is not
+ * obligated to, for example, if there are no pending callbacks.
+ */
+void rcu_barrier_tasks_rude(void)
+{
+ rcu_barrier_tasks_generic(&rcu_tasks_rude);
+}
+EXPORT_SYMBOL_GPL(rcu_barrier_tasks_rude);
+
+static int __init rcu_spawn_tasks_rude_kthread(void)
+{
+ cblist_init_generic(&rcu_tasks_rude);
+ rcu_tasks_rude.gp_sleep = HZ / 10;
+ rcu_spawn_tasks_kthread_generic(&rcu_tasks_rude);
+ return 0;
+}
+
+#if !defined(CONFIG_TINY_RCU)
+void show_rcu_tasks_rude_gp_kthread(void)
+{
+ show_rcu_tasks_generic_gp_kthread(&rcu_tasks_rude, "");
+}
+EXPORT_SYMBOL_GPL(show_rcu_tasks_rude_gp_kthread);
+#endif // !defined(CONFIG_TINY_RCU)
+#endif /* #ifdef CONFIG_TASKS_RUDE_RCU */
+
+////////////////////////////////////////////////////////////////////////
+//
+// Tracing variant of Tasks RCU. This variant is designed to be used
+// to protect tracing hooks, including those of BPF. This variant
+// therefore:
+//
+// 1. Has explicit read-side markers to allow finite grace periods
+// in the face of in-kernel loops for PREEMPT=n builds.
+//
+// 2. Protects code in the idle loop, exception entry/exit, and
+// CPU-hotplug code paths, similar to the capabilities of SRCU.
+//
+// 3. Avoids expensive read-side instructions, having overhead similar
+// to that of Preemptible RCU.
+//
+// There are of course downsides. For example, the grace-period code
+// can send IPIs to CPUs, even when those CPUs are in the idle loop or
+// in nohz_full userspace. If needed, these downsides can be at least
+// partially remedied.
+//
+// Perhaps most important, this variant of RCU does not affect the vanilla
+// flavors, rcu_preempt and rcu_sched. The fact that RCU Tasks Trace
+// readers can operate from idle, offline, and exception entry/exit in no
+// way allows rcu_preempt and rcu_sched readers to also do so.
+//
+// The implementation uses rcu_tasks_wait_gp(), which relies on function
+// pointers in the rcu_tasks structure. The rcu_spawn_tasks_trace_kthread()
+// function sets these function pointers up so that rcu_tasks_wait_gp()
+// invokes these functions in this order:
+//
+// rcu_tasks_trace_pregp_step():
+// Disables CPU hotplug, adds all currently executing tasks to the
+// holdout list, then checks the state of all tasks that blocked
+// or were preempted within their current RCU Tasks Trace read-side
+// critical section, adding them to the holdout list if appropriate.
+// Finally, this function re-enables CPU hotplug.
+// The ->pertask_func() pointer is NULL, so there is no per-task processing.
+// rcu_tasks_trace_postscan():
+// Invokes synchronize_rcu() to wait for late-stage exiting tasks
+// to finish exiting.
+// check_all_holdout_tasks_trace(), repeatedly until holdout list is empty:
+// Scans the holdout list, attempting to identify a quiescent state
+// for each task on the list. If there is a quiescent state, the
+// corresponding task is removed from the holdout list. Once this
+// list is empty, the grace period has completed.
+// rcu_tasks_trace_postgp():
+// Provides the needed full memory barrier and does debug checks.
+//
+// The exit_tasks_rcu_finish_trace() synchronizes with exiting tasks.
+//
+// Pre-grace-period update-side code is ordered before the grace period
+// via the ->cbs_lock and barriers in rcu_tasks_kthread(). Pre-grace-period
+// read-side code is ordered before the grace period by atomic operations
+// on .b.need_qs flag of each task involved in this process, or by scheduler
+// context-switch ordering (for locked-down non-running readers).
+
+// The lockdep state must be outside of #ifdef to be useful.
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+static struct lock_class_key rcu_lock_trace_key;
+struct lockdep_map rcu_trace_lock_map =
+ STATIC_LOCKDEP_MAP_INIT("rcu_read_lock_trace", &rcu_lock_trace_key);
+EXPORT_SYMBOL_GPL(rcu_trace_lock_map);
+#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
+
+#ifdef CONFIG_TASKS_TRACE_RCU
+
+// Record outstanding IPIs to each CPU. No point in sending two...
+static DEFINE_PER_CPU(bool, trc_ipi_to_cpu);
+
+// The number of detections of task quiescent state relying on
+// heavyweight readers executing explicit memory barriers.
+static unsigned long n_heavy_reader_attempts;
+static unsigned long n_heavy_reader_updates;
+static unsigned long n_heavy_reader_ofl_updates;
+static unsigned long n_trc_holdouts;
+
+void call_rcu_tasks_trace(struct rcu_head *rhp, rcu_callback_t func);
+DEFINE_RCU_TASKS(rcu_tasks_trace, rcu_tasks_wait_gp, call_rcu_tasks_trace,
+ "RCU Tasks Trace");
+
+/* Load from ->trc_reader_special.b.need_qs with proper ordering. */
+static u8 rcu_ld_need_qs(struct task_struct *t)
+{
+ smp_mb(); // Enforce full grace-period ordering.
+ return smp_load_acquire(&t->trc_reader_special.b.need_qs);
+}
+
+/* Store to ->trc_reader_special.b.need_qs with proper ordering. */
+static void rcu_st_need_qs(struct task_struct *t, u8 v)
+{
+ smp_store_release(&t->trc_reader_special.b.need_qs, v);
+ smp_mb(); // Enforce full grace-period ordering.
+}
+
+/*
+ * Do a cmpxchg() on ->trc_reader_special.b.need_qs, allowing for
+ * the four-byte operand-size restriction of some platforms.
+ * Returns the old value, which is often ignored.
+ */
+u8 rcu_trc_cmpxchg_need_qs(struct task_struct *t, u8 old, u8 new)
+{
+ union rcu_special ret;
+ union rcu_special trs_old = READ_ONCE(t->trc_reader_special);
+ union rcu_special trs_new = trs_old;
+
+ if (trs_old.b.need_qs != old)
+ return trs_old.b.need_qs;
+ trs_new.b.need_qs = new;
+ ret.s = cmpxchg(&t->trc_reader_special.s, trs_old.s, trs_new.s);
+ return ret.b.need_qs;
+}
+EXPORT_SYMBOL_GPL(rcu_trc_cmpxchg_need_qs);
+
+/*
+ * If we are the last reader, signal the grace-period kthread.
+ * Also remove from the per-CPU list of blocked tasks.
+ */
+void rcu_read_unlock_trace_special(struct task_struct *t)
+{
+ unsigned long flags;
+ struct rcu_tasks_percpu *rtpcp;
+ union rcu_special trs;
+
+ // Open-coded full-word version of rcu_ld_need_qs().
+ smp_mb(); // Enforce full grace-period ordering.
+ trs = smp_load_acquire(&t->trc_reader_special);
+
+ if (IS_ENABLED(CONFIG_TASKS_TRACE_RCU_READ_MB) && t->trc_reader_special.b.need_mb)
+ smp_mb(); // Pairs with update-side barriers.
+ // Update .need_qs before ->trc_reader_nesting for irq/NMI handlers.
+ if (trs.b.need_qs == (TRC_NEED_QS_CHECKED | TRC_NEED_QS)) {
+ u8 result = rcu_trc_cmpxchg_need_qs(t, TRC_NEED_QS_CHECKED | TRC_NEED_QS,
+ TRC_NEED_QS_CHECKED);
+
+ WARN_ONCE(result != trs.b.need_qs, "%s: result = %d", __func__, result);
+ }
+ if (trs.b.blocked) {
+ rtpcp = per_cpu_ptr(rcu_tasks_trace.rtpcpu, t->trc_blkd_cpu);
+ raw_spin_lock_irqsave_rcu_node(rtpcp, flags);
+ list_del_init(&t->trc_blkd_node);
+ WRITE_ONCE(t->trc_reader_special.b.blocked, false);
+ raw_spin_unlock_irqrestore_rcu_node(rtpcp, flags);
+ }
+ WRITE_ONCE(t->trc_reader_nesting, 0);
+}
+EXPORT_SYMBOL_GPL(rcu_read_unlock_trace_special);
+
+/* Add a newly blocked reader task to its CPU's list. */
+void rcu_tasks_trace_qs_blkd(struct task_struct *t)
+{
+ unsigned long flags;
+ struct rcu_tasks_percpu *rtpcp;
+
+ local_irq_save(flags);
+ rtpcp = this_cpu_ptr(rcu_tasks_trace.rtpcpu);
+ raw_spin_lock_rcu_node(rtpcp); // irqs already disabled
+ t->trc_blkd_cpu = smp_processor_id();
+ if (!rtpcp->rtp_blkd_tasks.next)
+ INIT_LIST_HEAD(&rtpcp->rtp_blkd_tasks);
+ list_add(&t->trc_blkd_node, &rtpcp->rtp_blkd_tasks);
+ WRITE_ONCE(t->trc_reader_special.b.blocked, true);
+ raw_spin_unlock_irqrestore_rcu_node(rtpcp, flags);
+}
+EXPORT_SYMBOL_GPL(rcu_tasks_trace_qs_blkd);
+
+/* Add a task to the holdout list, if it is not already on the list. */
+static void trc_add_holdout(struct task_struct *t, struct list_head *bhp)
+{
+ if (list_empty(&t->trc_holdout_list)) {
+ get_task_struct(t);
+ list_add(&t->trc_holdout_list, bhp);
+ n_trc_holdouts++;
+ }
+}
+
+/* Remove a task from the holdout list, if it is in fact present. */
+static void trc_del_holdout(struct task_struct *t)
+{
+ if (!list_empty(&t->trc_holdout_list)) {
+ list_del_init(&t->trc_holdout_list);
+ put_task_struct(t);
+ n_trc_holdouts--;
+ }
+}
+
+/* IPI handler to check task state. */
+static void trc_read_check_handler(void *t_in)
+{
+ int nesting;
+ struct task_struct *t = current;
+ struct task_struct *texp = t_in;
+
+ // If the task is no longer running on this CPU, leave.
+ if (unlikely(texp != t))
+ goto reset_ipi; // Already on holdout list, so will check later.
+
+ // If the task is not in a read-side critical section, and
+ // if this is the last reader, awaken the grace-period kthread.
+ nesting = READ_ONCE(t->trc_reader_nesting);
+ if (likely(!nesting)) {
+ rcu_trc_cmpxchg_need_qs(t, 0, TRC_NEED_QS_CHECKED);
+ goto reset_ipi;
+ }
+ // If we are racing with an rcu_read_unlock_trace(), try again later.
+ if (unlikely(nesting < 0))
+ goto reset_ipi;
+
+ // Get here if the task is in a read-side critical section.
+ // Set its state so that it will update state for the grace-period
+ // kthread upon exit from that critical section.
+ rcu_trc_cmpxchg_need_qs(t, 0, TRC_NEED_QS | TRC_NEED_QS_CHECKED);
+
+reset_ipi:
+ // Allow future IPIs to be sent on CPU and for task.
+ // Also order this IPI handler against any later manipulations of
+ // the intended task.
+ smp_store_release(per_cpu_ptr(&trc_ipi_to_cpu, smp_processor_id()), false); // ^^^
+ smp_store_release(&texp->trc_ipi_to_cpu, -1); // ^^^
+}
+
+/* Callback function for scheduler to check locked-down task. */
+static int trc_inspect_reader(struct task_struct *t, void *bhp_in)
+{
+ struct list_head *bhp = bhp_in;
+ int cpu = task_cpu(t);
+ int nesting;
+ bool ofl = cpu_is_offline(cpu);
+
+ if (task_curr(t) && !ofl) {
+ // If no chance of heavyweight readers, do it the hard way.
+ if (!IS_ENABLED(CONFIG_TASKS_TRACE_RCU_READ_MB))
+ return -EINVAL;
+
+ // If heavyweight readers are enabled on the remote task,
+ // we can inspect its state despite its currently running.
+ // However, we cannot safely change its state.
+ n_heavy_reader_attempts++;
+ // Check for "running" idle tasks on offline CPUs.
+ if (!rcu_dynticks_zero_in_eqs(cpu, &t->trc_reader_nesting))
+ return -EINVAL; // No quiescent state, do it the hard way.
+ n_heavy_reader_updates++;
+ nesting = 0;
+ } else {
+ // The task is not running, so C-language access is safe.
+ nesting = t->trc_reader_nesting;
+ WARN_ON_ONCE(ofl && task_curr(t) && !is_idle_task(t));
+ if (IS_ENABLED(CONFIG_TASKS_TRACE_RCU_READ_MB) && ofl)
+ n_heavy_reader_ofl_updates++;
+ }
+
+ // If not exiting a read-side critical section, mark as checked
+ // so that the grace-period kthread will remove it from the
+ // holdout list.
+ if (!nesting) {
+ rcu_trc_cmpxchg_need_qs(t, 0, TRC_NEED_QS_CHECKED);
+ return 0; // In QS, so done.
+ }
+ if (nesting < 0)
+ return -EINVAL; // Reader transitioning, try again later.
+
+ // The task is in a read-side critical section, so set up its
+ // state so that it will update state upon exit from that critical
+ // section.
+ if (!rcu_trc_cmpxchg_need_qs(t, 0, TRC_NEED_QS | TRC_NEED_QS_CHECKED))
+ trc_add_holdout(t, bhp);
+ return 0;
+}
+
+/* Attempt to extract the state for the specified task. */
+static void trc_wait_for_one_reader(struct task_struct *t,
+ struct list_head *bhp)
+{
+ int cpu;
+
+ // If a previous IPI is still in flight, let it complete.
+ if (smp_load_acquire(&t->trc_ipi_to_cpu) != -1) // Order IPI
+ return;
+
+ // The current task had better be in a quiescent state.
+ if (t == current) {
+ rcu_trc_cmpxchg_need_qs(t, 0, TRC_NEED_QS_CHECKED);
+ WARN_ON_ONCE(READ_ONCE(t->trc_reader_nesting));
+ return;
+ }
+
+ // Attempt to nail down the task for inspection.
+ get_task_struct(t);
+ if (!task_call_func(t, trc_inspect_reader, bhp)) {
+ put_task_struct(t);
+ return;
+ }
+ put_task_struct(t);
+
+ // If this task is not yet on the holdout list, then we are in
+ // an RCU read-side critical section. Otherwise, the invocation of
+ // trc_add_holdout() that added it to the list did the necessary
+ // get_task_struct(). Either way, the task cannot be freed out
+ // from under this code.
+
+ // If currently running, send an IPI, either way, add to list.
+ trc_add_holdout(t, bhp);
+ if (task_curr(t) &&
+ time_after(jiffies + 1, rcu_tasks_trace.gp_start + rcu_task_ipi_delay)) {
+ // The task is currently running, so try IPIing it.
+ cpu = task_cpu(t);
+
+ // If there is already an IPI outstanding, let it happen.
+ if (per_cpu(trc_ipi_to_cpu, cpu) || t->trc_ipi_to_cpu >= 0)
+ return;
+
+ per_cpu(trc_ipi_to_cpu, cpu) = true;
+ t->trc_ipi_to_cpu = cpu;
+ rcu_tasks_trace.n_ipis++;
+ if (smp_call_function_single(cpu, trc_read_check_handler, t, 0)) {
+ // Just in case there is some other reason for
+ // failure than the target CPU being offline.
+ WARN_ONCE(1, "%s(): smp_call_function_single() failed for CPU: %d\n",
+ __func__, cpu);
+ rcu_tasks_trace.n_ipis_fails++;
+ per_cpu(trc_ipi_to_cpu, cpu) = false;
+ t->trc_ipi_to_cpu = -1;
+ }
+ }
+}
+
+/*
+ * Initialize for first-round processing for the specified task.
+ * Return false if task is NULL or already taken care of, true otherwise.
+ */
+static bool rcu_tasks_trace_pertask_prep(struct task_struct *t, bool notself)
+{
+ // During early boot when there is only the one boot CPU, there
+ // is no idle task for the other CPUs. Also, the grace-period
+ // kthread is always in a quiescent state. In addition, just return
+ // if this task is already on the list.
+ if (unlikely(t == NULL) || (t == current && notself) || !list_empty(&t->trc_holdout_list))
+ return false;
+
+ rcu_st_need_qs(t, 0);
+ t->trc_ipi_to_cpu = -1;
+ return true;
+}
+
+/* Do first-round processing for the specified task. */
+static void rcu_tasks_trace_pertask(struct task_struct *t, struct list_head *hop)
+{
+ if (rcu_tasks_trace_pertask_prep(t, true))
+ trc_wait_for_one_reader(t, hop);
+}
+
+/* Initialize for a new RCU-tasks-trace grace period. */
+static void rcu_tasks_trace_pregp_step(struct list_head *hop)
+{
+ LIST_HEAD(blkd_tasks);
+ int cpu;
+ unsigned long flags;
+ struct rcu_tasks_percpu *rtpcp;
+ struct task_struct *t;
+
+ // There shouldn't be any old IPIs, but...
+ for_each_possible_cpu(cpu)
+ WARN_ON_ONCE(per_cpu(trc_ipi_to_cpu, cpu));
+
+ // Disable CPU hotplug across the CPU scan for the benefit of
+ // any IPIs that might be needed. This also waits for all readers
+ // in CPU-hotplug code paths.
+ cpus_read_lock();
+
+ // These rcu_tasks_trace_pertask_prep() calls are serialized to
+ // allow safe access to the hop list.
+ for_each_online_cpu(cpu) {
+ rcu_read_lock();
+ t = cpu_curr_snapshot(cpu);
+ if (rcu_tasks_trace_pertask_prep(t, true))
+ trc_add_holdout(t, hop);
+ rcu_read_unlock();
+ cond_resched_tasks_rcu_qs();
+ }
+
+ // Only after all running tasks have been accounted for is it
+ // safe to take care of the tasks that have blocked within their
+ // current RCU tasks trace read-side critical section.
+ for_each_possible_cpu(cpu) {
+ rtpcp = per_cpu_ptr(rcu_tasks_trace.rtpcpu, cpu);
+ raw_spin_lock_irqsave_rcu_node(rtpcp, flags);
+ list_splice_init(&rtpcp->rtp_blkd_tasks, &blkd_tasks);
+ while (!list_empty(&blkd_tasks)) {
+ rcu_read_lock();
+ t = list_first_entry(&blkd_tasks, struct task_struct, trc_blkd_node);
+ list_del_init(&t->trc_blkd_node);
+ list_add(&t->trc_blkd_node, &rtpcp->rtp_blkd_tasks);
+ raw_spin_unlock_irqrestore_rcu_node(rtpcp, flags);
+ rcu_tasks_trace_pertask(t, hop);
+ rcu_read_unlock();
+ raw_spin_lock_irqsave_rcu_node(rtpcp, flags);
+ }
+ raw_spin_unlock_irqrestore_rcu_node(rtpcp, flags);
+ cond_resched_tasks_rcu_qs();
+ }
+
+ // Re-enable CPU hotplug now that the holdout list is populated.
+ cpus_read_unlock();
+}
+
+/*
+ * Do intermediate processing between task and holdout scans.
+ */
+static void rcu_tasks_trace_postscan(struct list_head *hop)
+{
+ // Wait for late-stage exiting tasks to finish exiting.
+ // These might have passed the call to exit_tasks_rcu_finish().
+ synchronize_rcu();
+ // Any tasks that exit after this point will set
+ // TRC_NEED_QS_CHECKED in ->trc_reader_special.b.need_qs.
+}
+
+/* Communicate task state back to the RCU tasks trace stall warning request. */
+struct trc_stall_chk_rdr {
+ int nesting;
+ int ipi_to_cpu;
+ u8 needqs;
+};
+
+static int trc_check_slow_task(struct task_struct *t, void *arg)
+{
+ struct trc_stall_chk_rdr *trc_rdrp = arg;
+
+ if (task_curr(t) && cpu_online(task_cpu(t)))
+ return false; // It is running, so decline to inspect it.
+ trc_rdrp->nesting = READ_ONCE(t->trc_reader_nesting);
+ trc_rdrp->ipi_to_cpu = READ_ONCE(t->trc_ipi_to_cpu);
+ trc_rdrp->needqs = rcu_ld_need_qs(t);
+ return true;
+}
+
+/* Show the state of a task stalling the current RCU tasks trace GP. */
+static void show_stalled_task_trace(struct task_struct *t, bool *firstreport)
+{
+ int cpu;
+ struct trc_stall_chk_rdr trc_rdr;
+ bool is_idle_tsk = is_idle_task(t);
+
+ if (*firstreport) {
+ pr_err("INFO: rcu_tasks_trace detected stalls on tasks:\n");
+ *firstreport = false;
+ }
+ cpu = task_cpu(t);
+ if (!task_call_func(t, trc_check_slow_task, &trc_rdr))
+ pr_alert("P%d: %c%c\n",
+ t->pid,
+ ".I"[t->trc_ipi_to_cpu >= 0],
+ ".i"[is_idle_tsk]);
+ else
+ pr_alert("P%d: %c%c%c%c nesting: %d%c%c cpu: %d%s\n",
+ t->pid,
+ ".I"[trc_rdr.ipi_to_cpu >= 0],
+ ".i"[is_idle_tsk],
+ ".N"[cpu >= 0 && tick_nohz_full_cpu(cpu)],
+ ".B"[!!data_race(t->trc_reader_special.b.blocked)],
+ trc_rdr.nesting,
+ " !CN"[trc_rdr.needqs & 0x3],
+ " ?"[trc_rdr.needqs > 0x3],
+ cpu, cpu_online(cpu) ? "" : "(offline)");
+ sched_show_task(t);
+}
+
+/* List stalled IPIs for RCU tasks trace. */
+static void show_stalled_ipi_trace(void)
+{
+ int cpu;
+
+ for_each_possible_cpu(cpu)
+ if (per_cpu(trc_ipi_to_cpu, cpu))
+ pr_alert("\tIPI outstanding to CPU %d\n", cpu);
+}
+
+/* Do one scan of the holdout list. */
+static void check_all_holdout_tasks_trace(struct list_head *hop,
+ bool needreport, bool *firstreport)
+{
+ struct task_struct *g, *t;
+
+ // Disable CPU hotplug across the holdout list scan for IPIs.
+ cpus_read_lock();
+
+ list_for_each_entry_safe(t, g, hop, trc_holdout_list) {
+ // If safe and needed, try to check the current task.
+ if (READ_ONCE(t->trc_ipi_to_cpu) == -1 &&
+ !(rcu_ld_need_qs(t) & TRC_NEED_QS_CHECKED))
+ trc_wait_for_one_reader(t, hop);
+
+ // If check succeeded, remove this task from the list.
+ if (smp_load_acquire(&t->trc_ipi_to_cpu) == -1 &&
+ rcu_ld_need_qs(t) == TRC_NEED_QS_CHECKED)
+ trc_del_holdout(t);
+ else if (needreport)
+ show_stalled_task_trace(t, firstreport);
+ cond_resched_tasks_rcu_qs();
+ }
+
+ // Re-enable CPU hotplug now that the holdout list scan has completed.
+ cpus_read_unlock();
+
+ if (needreport) {
+ if (*firstreport)
+ pr_err("INFO: rcu_tasks_trace detected stalls? (Late IPI?)\n");
+ show_stalled_ipi_trace();
+ }
+}
+
+static void rcu_tasks_trace_empty_fn(void *unused)
+{
+}
+
+/* Wait for grace period to complete and provide ordering. */
+static void rcu_tasks_trace_postgp(struct rcu_tasks *rtp)
+{
+ int cpu;
+
+ // Wait for any lingering IPI handlers to complete. Note that
+ // if a CPU has gone offline or transitioned to userspace in the
+ // meantime, all IPI handlers should have been drained beforehand.
+ // Yes, this assumes that CPUs process IPIs in order. If that ever
+ // changes, there will need to be a recheck and/or timed wait.
+ for_each_online_cpu(cpu)
+ if (WARN_ON_ONCE(smp_load_acquire(per_cpu_ptr(&trc_ipi_to_cpu, cpu))))
+ smp_call_function_single(cpu, rcu_tasks_trace_empty_fn, NULL, 1);
+
+ smp_mb(); // Caller's code must be ordered after wakeup.
+ // Pairs with pretty much every ordering primitive.
+}
+
+/* Report any needed quiescent state for this exiting task. */
+static void exit_tasks_rcu_finish_trace(struct task_struct *t)
+{
+ union rcu_special trs = READ_ONCE(t->trc_reader_special);
+
+ rcu_trc_cmpxchg_need_qs(t, 0, TRC_NEED_QS_CHECKED);
+ WARN_ON_ONCE(READ_ONCE(t->trc_reader_nesting));
+ if (WARN_ON_ONCE(rcu_ld_need_qs(t) & TRC_NEED_QS || trs.b.blocked))
+ rcu_read_unlock_trace_special(t);
+ else
+ WRITE_ONCE(t->trc_reader_nesting, 0);
+}
+
+/**
+ * call_rcu_tasks_trace() - Queue a callback trace task-based grace period
+ * @rhp: structure to be used for queueing the RCU updates.
+ * @func: actual callback function to be invoked after the grace period
+ *
+ * The callback function will be invoked some time after a trace rcu-tasks
+ * grace period elapses, in other words after all currently executing
+ * trace rcu-tasks read-side critical sections have completed. These
+ * read-side critical sections are delimited by calls to rcu_read_lock_trace()
+ * and rcu_read_unlock_trace().
+ *
+ * See the description of call_rcu() for more detailed information on
+ * memory ordering guarantees.
+ */
+void call_rcu_tasks_trace(struct rcu_head *rhp, rcu_callback_t func)
+{
+ call_rcu_tasks_generic(rhp, func, &rcu_tasks_trace);
+}
+EXPORT_SYMBOL_GPL(call_rcu_tasks_trace);
+
+/**
+ * synchronize_rcu_tasks_trace - wait for a trace rcu-tasks grace period
+ *
+ * Control will return to the caller some time after a trace rcu-tasks
+ * grace period has elapsed, in other words after all currently executing
+ * trace rcu-tasks read-side critical sections have elapsed. These read-side
+ * critical sections are delimited by calls to rcu_read_lock_trace()
+ * and rcu_read_unlock_trace().
+ *
+ * This is a very specialized primitive, intended only for a few uses in
+ * tracing and other situations requiring manipulation of function preambles
+ * and profiling hooks. The synchronize_rcu_tasks_trace() function is not
+ * (yet) intended for heavy use from multiple CPUs.
+ *
+ * See the description of synchronize_rcu() for more detailed information
+ * on memory ordering guarantees.
+ */
+void synchronize_rcu_tasks_trace(void)
+{
+ RCU_LOCKDEP_WARN(lock_is_held(&rcu_trace_lock_map), "Illegal synchronize_rcu_tasks_trace() in RCU Tasks Trace read-side critical section");
+ synchronize_rcu_tasks_generic(&rcu_tasks_trace);
+}
+EXPORT_SYMBOL_GPL(synchronize_rcu_tasks_trace);
+
+/**
+ * rcu_barrier_tasks_trace - Wait for in-flight call_rcu_tasks_trace() callbacks.
+ *
+ * Although the current implementation is guaranteed to wait, it is not
+ * obligated to, for example, if there are no pending callbacks.
+ */
+void rcu_barrier_tasks_trace(void)
+{
+ rcu_barrier_tasks_generic(&rcu_tasks_trace);
+}
+EXPORT_SYMBOL_GPL(rcu_barrier_tasks_trace);
+
+static int __init rcu_spawn_tasks_trace_kthread(void)
+{
+ cblist_init_generic(&rcu_tasks_trace);
+ if (IS_ENABLED(CONFIG_TASKS_TRACE_RCU_READ_MB)) {
+ rcu_tasks_trace.gp_sleep = HZ / 10;
+ rcu_tasks_trace.init_fract = HZ / 10;
+ } else {
+ rcu_tasks_trace.gp_sleep = HZ / 200;
+ if (rcu_tasks_trace.gp_sleep <= 0)
+ rcu_tasks_trace.gp_sleep = 1;
+ rcu_tasks_trace.init_fract = HZ / 200;
+ if (rcu_tasks_trace.init_fract <= 0)
+ rcu_tasks_trace.init_fract = 1;
+ }
+ rcu_tasks_trace.pregp_func = rcu_tasks_trace_pregp_step;
+ rcu_tasks_trace.postscan_func = rcu_tasks_trace_postscan;
+ rcu_tasks_trace.holdouts_func = check_all_holdout_tasks_trace;
+ rcu_tasks_trace.postgp_func = rcu_tasks_trace_postgp;
+ rcu_spawn_tasks_kthread_generic(&rcu_tasks_trace);
+ return 0;
+}
+
+#if !defined(CONFIG_TINY_RCU)
+void show_rcu_tasks_trace_gp_kthread(void)
+{
+ char buf[64];
+
+ sprintf(buf, "N%lu h:%lu/%lu/%lu",
+ data_race(n_trc_holdouts),
+ data_race(n_heavy_reader_ofl_updates),
+ data_race(n_heavy_reader_updates),
+ data_race(n_heavy_reader_attempts));
+ show_rcu_tasks_generic_gp_kthread(&rcu_tasks_trace, buf);
+}
+EXPORT_SYMBOL_GPL(show_rcu_tasks_trace_gp_kthread);
+#endif // !defined(CONFIG_TINY_RCU)
+
+#else /* #ifdef CONFIG_TASKS_TRACE_RCU */
+static void exit_tasks_rcu_finish_trace(struct task_struct *t) { }
+#endif /* #else #ifdef CONFIG_TASKS_TRACE_RCU */
+
+#ifndef CONFIG_TINY_RCU
+void show_rcu_tasks_gp_kthreads(void)
+{
+ show_rcu_tasks_classic_gp_kthread();
+ show_rcu_tasks_rude_gp_kthread();
+ show_rcu_tasks_trace_gp_kthread();
+}
+#endif /* #ifndef CONFIG_TINY_RCU */
+
+#ifdef CONFIG_PROVE_RCU
+struct rcu_tasks_test_desc {
+ struct rcu_head rh;
+ const char *name;
+ bool notrun;
+ unsigned long runstart;
+};
+
+static struct rcu_tasks_test_desc tests[] = {
+ {
+ .name = "call_rcu_tasks()",
+ /* If not defined, the test is skipped. */
+ .notrun = IS_ENABLED(CONFIG_TASKS_RCU),
+ },
+ {
+ .name = "call_rcu_tasks_rude()",
+ /* If not defined, the test is skipped. */
+ .notrun = IS_ENABLED(CONFIG_TASKS_RUDE_RCU),
+ },
+ {
+ .name = "call_rcu_tasks_trace()",
+ /* If not defined, the test is skipped. */
+ .notrun = IS_ENABLED(CONFIG_TASKS_TRACE_RCU)
+ }
+};
+
+static void test_rcu_tasks_callback(struct rcu_head *rhp)
+{
+ struct rcu_tasks_test_desc *rttd =
+ container_of(rhp, struct rcu_tasks_test_desc, rh);
+
+ pr_info("Callback from %s invoked.\n", rttd->name);
+
+ rttd->notrun = false;
+}
+
+static void rcu_tasks_initiate_self_tests(void)
+{
+ unsigned long j = jiffies;
+
+ pr_info("Running RCU-tasks wait API self tests\n");
+#ifdef CONFIG_TASKS_RCU
+ tests[0].runstart = j;
+ synchronize_rcu_tasks();
+ call_rcu_tasks(&tests[0].rh, test_rcu_tasks_callback);
+#endif
+
+#ifdef CONFIG_TASKS_RUDE_RCU
+ tests[1].runstart = j;
+ synchronize_rcu_tasks_rude();
+ call_rcu_tasks_rude(&tests[1].rh, test_rcu_tasks_callback);
+#endif
+
+#ifdef CONFIG_TASKS_TRACE_RCU
+ tests[2].runstart = j;
+ synchronize_rcu_tasks_trace();
+ call_rcu_tasks_trace(&tests[2].rh, test_rcu_tasks_callback);
+#endif
+}
+
+/*
+ * Return: 0 - test passed
+ * 1 - test failed, but have not timed out yet
+ * -1 - test failed and timed out
+ */
+static int rcu_tasks_verify_self_tests(void)
+{
+ int ret = 0;
+ int i;
+ unsigned long bst = rcu_task_stall_timeout;
+
+ if (bst <= 0 || bst > RCU_TASK_BOOT_STALL_TIMEOUT)
+ bst = RCU_TASK_BOOT_STALL_TIMEOUT;
+ for (i = 0; i < ARRAY_SIZE(tests); i++) {
+ while (tests[i].notrun) { // still hanging.
+ if (time_after(jiffies, tests[i].runstart + bst)) {
+ pr_err("%s has failed boot-time tests.\n", tests[i].name);
+ ret = -1;
+ break;
+ }
+ ret = 1;
+ break;
+ }
+ }
+ WARN_ON(ret < 0);
+
+ return ret;
+}
+
+/*
+ * Repeat the rcu_tasks_verify_self_tests() call once every second until the
+ * test passes or has timed out.
+ */
+static struct delayed_work rcu_tasks_verify_work;
+static void rcu_tasks_verify_work_fn(struct work_struct *work __maybe_unused)
+{
+ int ret = rcu_tasks_verify_self_tests();
+
+ if (ret <= 0)
+ return;
+
+ /* Test fails but not timed out yet, reschedule another check */
+ schedule_delayed_work(&rcu_tasks_verify_work, HZ);
+}
+
+static int rcu_tasks_verify_schedule_work(void)
+{
+ INIT_DELAYED_WORK(&rcu_tasks_verify_work, rcu_tasks_verify_work_fn);
+ rcu_tasks_verify_work_fn(NULL);
+ return 0;
+}
+late_initcall(rcu_tasks_verify_schedule_work);
+#else /* #ifdef CONFIG_PROVE_RCU */
+static void rcu_tasks_initiate_self_tests(void) { }
+#endif /* #else #ifdef CONFIG_PROVE_RCU */
+
+void __init rcu_init_tasks_generic(void)
+{
+#ifdef CONFIG_TASKS_RCU
+ rcu_spawn_tasks_kthread();
+#endif
+
+#ifdef CONFIG_TASKS_RUDE_RCU
+ rcu_spawn_tasks_rude_kthread();
+#endif
+
+#ifdef CONFIG_TASKS_TRACE_RCU
+ rcu_spawn_tasks_trace_kthread();
+#endif
+
+ // Run the self-tests.
+ rcu_tasks_initiate_self_tests();
+}
+
+#else /* #ifdef CONFIG_TASKS_RCU_GENERIC */
+static inline void rcu_tasks_bootup_oddness(void) {}
+#endif /* #else #ifdef CONFIG_TASKS_RCU_GENERIC */
diff --git a/kernel/rcu/tiny.c b/kernel/rcu/tiny.c
index dd572ce7c747..a33a8d4942c3 100644
--- a/kernel/rcu/tiny.c
+++ b/kernel/rcu/tiny.c
@@ -23,6 +23,7 @@
#include <linux/cpu.h>
#include <linux/prefetch.h>
#include <linux/slab.h>
+#include <linux/mm.h>
#include "rcu.h"
@@ -31,12 +32,14 @@ struct rcu_ctrlblk {
struct rcu_head *rcucblist; /* List of pending callbacks (CBs). */
struct rcu_head **donetail; /* ->next pointer of last "done" CB. */
struct rcu_head **curtail; /* ->next pointer of last CB. */
+ unsigned long gp_seq; /* Grace-period counter. */
};
/* Definition for rcupdate control block. */
static struct rcu_ctrlblk rcu_ctrlblk = {
.donetail = &rcu_ctrlblk.rcucblist,
.curtail = &rcu_ctrlblk.rcucblist,
+ .gp_seq = 0 - 300UL,
};
void rcu_barrier(void)
@@ -55,6 +58,7 @@ void rcu_qs(void)
rcu_ctrlblk.donetail = rcu_ctrlblk.curtail;
raise_softirq_irqoff(RCU_SOFTIRQ);
}
+ WRITE_ONCE(rcu_ctrlblk.gp_seq, rcu_ctrlblk.gp_seq + 2);
local_irq_restore(flags);
}
@@ -84,9 +88,9 @@ static inline bool rcu_reclaim_tiny(struct rcu_head *head)
unsigned long offset = (unsigned long)head->func;
rcu_lock_acquire(&rcu_callback_map);
- if (__is_kfree_rcu_offset(offset)) {
- trace_rcu_invoke_kfree_callback("", head, offset);
- kfree((void *)head - offset);
+ if (__is_kvfree_rcu_offset(offset)) {
+ trace_rcu_invoke_kvfree_callback("", head, offset);
+ kvfree((void *)head - offset);
rcu_lock_release(&rcu_callback_map);
return true;
}
@@ -135,8 +139,10 @@ static __latent_entropy void rcu_process_callbacks(struct softirq_action *unused
/*
* Wait for a grace period to elapse. But it is illegal to invoke
* synchronize_rcu() from within an RCU read-side critical section.
- * Therefore, any legal call to synchronize_rcu() is a quiescent
- * state, and so on a UP system, synchronize_rcu() need do nothing.
+ * Therefore, any legal call to synchronize_rcu() is a quiescent state,
+ * and so on a UP system, synchronize_rcu() need do nothing, other than
+ * let the polled APIs know that another grace period elapsed.
+ *
* (But Lai Jiangshan points out the benefits of doing might_sleep()
* to reduce latency.)
*
@@ -148,9 +154,14 @@ void synchronize_rcu(void)
lock_is_held(&rcu_lock_map) ||
lock_is_held(&rcu_sched_lock_map),
"Illegal synchronize_rcu() in RCU read-side critical section");
+ WRITE_ONCE(rcu_ctrlblk.gp_seq, rcu_ctrlblk.gp_seq + 2);
}
EXPORT_SYMBOL_GPL(synchronize_rcu);
+static void tiny_rcu_leak_callback(struct rcu_head *rhp)
+{
+}
+
/*
* Post an RCU callback to be invoked after the end of an RCU grace
* period. But since we have but one CPU, that would be after any
@@ -158,9 +169,20 @@ EXPORT_SYMBOL_GPL(synchronize_rcu);
*/
void call_rcu(struct rcu_head *head, rcu_callback_t func)
{
+ static atomic_t doublefrees;
unsigned long flags;
- debug_rcu_head_queue(head);
+ if (debug_rcu_head_queue(head)) {
+ if (atomic_inc_return(&doublefrees) < 4) {
+ pr_err("%s(): Double-freed CB %p->%pS()!!! ", __func__, head, head->func);
+ mem_dump_obj(head);
+ }
+
+ if (!__is_kvfree_rcu_offset((unsigned long)head->func))
+ WRITE_ONCE(head->func, tiny_rcu_leak_callback);
+ return;
+ }
+
head->func = func;
head->next = NULL;
@@ -176,9 +198,69 @@ void call_rcu(struct rcu_head *head, rcu_callback_t func)
}
EXPORT_SYMBOL_GPL(call_rcu);
+/*
+ * Store a grace-period-counter "cookie". For more information,
+ * see the Tree RCU header comment.
+ */
+void get_completed_synchronize_rcu_full(struct rcu_gp_oldstate *rgosp)
+{
+ rgosp->rgos_norm = RCU_GET_STATE_COMPLETED;
+}
+EXPORT_SYMBOL_GPL(get_completed_synchronize_rcu_full);
+
+/*
+ * Return a grace-period-counter "cookie". For more information,
+ * see the Tree RCU header comment.
+ */
+unsigned long get_state_synchronize_rcu(void)
+{
+ return READ_ONCE(rcu_ctrlblk.gp_seq);
+}
+EXPORT_SYMBOL_GPL(get_state_synchronize_rcu);
+
+/*
+ * Return a grace-period-counter "cookie" and ensure that a future grace
+ * period completes. For more information, see the Tree RCU header comment.
+ */
+unsigned long start_poll_synchronize_rcu(void)
+{
+ unsigned long gp_seq = get_state_synchronize_rcu();
+
+ if (unlikely(is_idle_task(current))) {
+ /* force scheduling for rcu_qs() */
+ resched_cpu(0);
+ }
+ return gp_seq;
+}
+EXPORT_SYMBOL_GPL(start_poll_synchronize_rcu);
+
+/*
+ * Return true if the grace period corresponding to oldstate has completed
+ * and false otherwise. For more information, see the Tree RCU header
+ * comment.
+ */
+bool poll_state_synchronize_rcu(unsigned long oldstate)
+{
+ return oldstate == RCU_GET_STATE_COMPLETED || READ_ONCE(rcu_ctrlblk.gp_seq) != oldstate;
+}
+EXPORT_SYMBOL_GPL(poll_state_synchronize_rcu);
+
+#ifdef CONFIG_KASAN_GENERIC
+void kvfree_call_rcu(struct rcu_head *head, rcu_callback_t func)
+{
+ if (head) {
+ void *ptr = (void *) head - (unsigned long) func;
+
+ kasan_record_aux_stack_noalloc(ptr);
+ }
+
+ __kvfree_call_rcu(head, func);
+}
+EXPORT_SYMBOL_GPL(kvfree_call_rcu);
+#endif
+
void __init rcu_init(void)
{
open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
rcu_early_boot_tests();
- srcu_init();
}
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index d91c9156fab2..93416afebd59 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -1,12 +1,12 @@
// SPDX-License-Identifier: GPL-2.0+
/*
- * Read-Copy Update mechanism for mutual exclusion
+ * Read-Copy Update mechanism for mutual exclusion (tree-based version)
*
* Copyright IBM Corporation, 2008
*
* Authors: Dipankar Sarma <dipankar@in.ibm.com>
* Manfred Spraul <manfred@colorfullife.com>
- * Paul E. McKenney <paulmck@linux.ibm.com> Hierarchical version
+ * Paul E. McKenney <paulmck@linux.ibm.com>
*
* Based on the original work by Paul McKenney <paulmck@linux.ibm.com>
* and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen.
@@ -32,6 +32,8 @@
#include <linux/export.h>
#include <linux/completion.h>
#include <linux/moduleparam.h>
+#include <linux/panic.h>
+#include <linux/panic_notifier.h>
#include <linux/percpu.h>
#include <linux/notifier.h>
#include <linux/cpu.h>
@@ -57,6 +59,10 @@
#include <linux/slab.h>
#include <linux/sched/isolation.h>
#include <linux/sched/clock.h>
+#include <linux/vmalloc.h>
+#include <linux/mm.h>
+#include <linux/kasan.h>
+#include <linux/context_tracking.h>
#include "../time/tick-internal.h"
#include "tree.h"
@@ -69,39 +75,33 @@
/* Data structures. */
-/*
- * Steal a bit from the bottom of ->dynticks for idle entry/exit
- * control. Initially this is for TLB flushing.
- */
-#define RCU_DYNTICK_CTRL_MASK 0x1
-#define RCU_DYNTICK_CTRL_CTR (RCU_DYNTICK_CTRL_MASK + 1)
-#ifndef rcu_eqs_special_exit
-#define rcu_eqs_special_exit() do { } while (0)
-#endif
-
static DEFINE_PER_CPU_SHARED_ALIGNED(struct rcu_data, rcu_data) = {
- .dynticks_nesting = 1,
- .dynticks_nmi_nesting = DYNTICK_IRQ_NONIDLE,
- .dynticks = ATOMIC_INIT(RCU_DYNTICK_CTRL_CTR),
+ .gpwrap = true,
+#ifdef CONFIG_RCU_NOCB_CPU
+ .cblist.flags = SEGCBLIST_RCU_CORE,
+#endif
};
static struct rcu_state rcu_state = {
.level = { &rcu_state.node[0] },
.gp_state = RCU_GP_IDLE,
.gp_seq = (0UL - 300UL) << RCU_SEQ_CTR_SHIFT,
.barrier_mutex = __MUTEX_INITIALIZER(rcu_state.barrier_mutex),
+ .barrier_lock = __RAW_SPIN_LOCK_UNLOCKED(rcu_state.barrier_lock),
.name = RCU_NAME,
.abbr = RCU_ABBR,
.exp_mutex = __MUTEX_INITIALIZER(rcu_state.exp_mutex),
.exp_wake_mutex = __MUTEX_INITIALIZER(rcu_state.exp_wake_mutex),
- .ofl_lock = __RAW_SPIN_LOCK_UNLOCKED(rcu_state.ofl_lock),
+ .ofl_lock = __ARCH_SPIN_LOCK_UNLOCKED,
};
/* Dump rcu_node combining tree at boot to verify correct setup. */
static bool dump_tree;
module_param(dump_tree, bool, 0444);
/* By default, use RCU_SOFTIRQ instead of rcuc kthreads. */
-static bool use_softirq = 1;
+static bool use_softirq = !IS_ENABLED(CONFIG_PREEMPT_RT);
+#ifndef CONFIG_PREEMPT_RT
module_param(use_softirq, bool, 0444);
+#endif
/* Control rcu_node-tree auto-balancing at boot time. */
static bool rcu_fanout_exact;
module_param(rcu_fanout_exact, bool, 0444);
@@ -150,8 +150,14 @@ static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu)
static void invoke_rcu_core(void);
static void rcu_report_exp_rdp(struct rcu_data *rdp);
static void sync_sched_exp_online_cleanup(int cpu);
+static void check_cb_ovld_locked(struct rcu_data *rdp, struct rcu_node *rnp);
+static bool rcu_rdp_is_offloaded(struct rcu_data *rdp);
-/* rcuc/rcub kthread realtime priority */
+/*
+ * rcuc/rcub/rcuop kthread realtime priority. The "rcuop"
+ * real-time priority(enabling/disabling) is controlled by
+ * the extra CONFIG_RCU_NOCB_CPU_CB_BOOST configuration.
+ */
static int kthread_prio = IS_ENABLED(CONFIG_RCU_BOOST) ? 1 : 0;
module_param(kthread_prio, int, 0444);
@@ -164,6 +170,32 @@ module_param(gp_init_delay, int, 0444);
static int gp_cleanup_delay;
module_param(gp_cleanup_delay, int, 0444);
+// Add delay to rcu_read_unlock() for strict grace periods.
+static int rcu_unlock_delay;
+#ifdef CONFIG_RCU_STRICT_GRACE_PERIOD
+module_param(rcu_unlock_delay, int, 0444);
+#endif
+
+/*
+ * This rcu parameter is runtime-read-only. It reflects
+ * a minimum allowed number of objects which can be cached
+ * per-CPU. Object size is equal to one page. This value
+ * can be changed at boot time.
+ */
+static int rcu_min_cached_objs = 5;
+module_param(rcu_min_cached_objs, int, 0444);
+
+// A page shrinker can ask for pages to be freed to make them
+// available for other parts of the system. This usually happens
+// under low memory conditions, and in that case we should also
+// defer page-cache filling for a short time period.
+//
+// The default value is 5 seconds, which is long enough to reduce
+// interference with the shrinker while it asks other systems to
+// drain their caches.
+static int rcu_delay_page_cache_fill_msec = 5000;
+module_param(rcu_delay_page_cache_fill_msec, int, 0444);
+
/* Retrieve RCU kthreads priority for rcutorture */
int rcu_get_gp_kthreads_prio(void)
{
@@ -180,7 +212,7 @@ EXPORT_SYMBOL_GPL(rcu_get_gp_kthreads_prio);
* the need for long delays to increase some race probabilities with the
* need for fast grace periods to increase other race probabilities.
*/
-#define PER_RCU_NODE_PERIOD 3 /* Number of grace periods between delays. */
+#define PER_RCU_NODE_PERIOD 3 /* Number of grace periods between delays for debugging. */
/*
* Compute the mask of online CPUs for the specified rcu_node structure.
@@ -194,6 +226,16 @@ static unsigned long rcu_rnp_online_cpus(struct rcu_node *rnp)
}
/*
+ * Is the CPU corresponding to the specified rcu_data structure online
+ * from RCU's perspective? This perspective is given by that structure's
+ * ->qsmaskinitnext field rather than by the global cpu_online_mask.
+ */
+static bool rcu_rdp_cpu_online(struct rcu_data *rdp)
+{
+ return !!(rdp->grpmask & rcu_rnp_online_cpus(rdp->mynode));
+}
+
+/*
* Return true if an RCU grace period is in progress. The READ_ONCE()s
* permit this function to be invoked without holding the root rcu_node
* structure's ->lock, but of course results can be subject to change.
@@ -220,54 +262,7 @@ void rcu_softirq_qs(void)
{
rcu_qs();
rcu_preempt_deferred_qs(current);
-}
-
-/*
- * Record entry into an extended quiescent state. This is only to be
- * called when not already in an extended quiescent state.
- */
-static void rcu_dynticks_eqs_enter(void)
-{
- struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
- int seq;
-
- /*
- * CPUs seeing atomic_add_return() must see prior RCU read-side
- * critical sections, and we also must force ordering with the
- * next idle sojourn.
- */
- seq = atomic_add_return(RCU_DYNTICK_CTRL_CTR, &rdp->dynticks);
- /* Better be in an extended quiescent state! */
- WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) &&
- (seq & RCU_DYNTICK_CTRL_CTR));
- /* Better not have special action (TLB flush) pending! */
- WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) &&
- (seq & RCU_DYNTICK_CTRL_MASK));
-}
-
-/*
- * Record exit from an extended quiescent state. This is only to be
- * called from an extended quiescent state.
- */
-static void rcu_dynticks_eqs_exit(void)
-{
- struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
- int seq;
-
- /*
- * CPUs seeing atomic_add_return() must see prior idle sojourns,
- * and we also must force ordering with the next RCU read-side
- * critical section.
- */
- seq = atomic_add_return(RCU_DYNTICK_CTRL_CTR, &rdp->dynticks);
- WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) &&
- !(seq & RCU_DYNTICK_CTRL_CTR));
- if (seq & RCU_DYNTICK_CTRL_MASK) {
- atomic_andnot(RCU_DYNTICK_CTRL_MASK, &rdp->dynticks);
- smp_mb__after_atomic(); /* _exit after clearing mask. */
- /* Prefer duplicate flushes to losing a flush. */
- rcu_eqs_special_exit();
- }
+ rcu_tasks_qs(current, false);
}
/*
@@ -282,34 +277,19 @@ static void rcu_dynticks_eqs_exit(void)
*/
static void rcu_dynticks_eqs_online(void)
{
- struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
-
- if (atomic_read(&rdp->dynticks) & RCU_DYNTICK_CTRL_CTR)
+ if (ct_dynticks() & RCU_DYNTICKS_IDX)
return;
- atomic_add(RCU_DYNTICK_CTRL_CTR, &rdp->dynticks);
-}
-
-/*
- * Is the current CPU in an extended quiescent state?
- *
- * No ordering, as we are sampling CPU-local information.
- */
-static bool rcu_dynticks_curr_cpu_in_eqs(void)
-{
- struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
-
- return !(atomic_read(&rdp->dynticks) & RCU_DYNTICK_CTRL_CTR);
+ ct_state_inc(RCU_DYNTICKS_IDX);
}
/*
* Snapshot the ->dynticks counter with full ordering so as to allow
* stable comparison of this counter with past and future snapshots.
*/
-static int rcu_dynticks_snap(struct rcu_data *rdp)
+static int rcu_dynticks_snap(int cpu)
{
- int snap = atomic_add_return(0, &rdp->dynticks);
-
- return snap & ~RCU_DYNTICK_CTRL_MASK;
+ smp_mb(); // Fundamental RCU ordering guarantee.
+ return ct_dynticks_cpu_acquire(cpu);
}
/*
@@ -318,7 +298,13 @@ static int rcu_dynticks_snap(struct rcu_data *rdp)
*/
static bool rcu_dynticks_in_eqs(int snap)
{
- return !(snap & RCU_DYNTICK_CTRL_CTR);
+ return !(snap & RCU_DYNTICKS_IDX);
+}
+
+/* Return true if the specified CPU is currently idle from an RCU viewpoint. */
+bool rcu_is_idle_cpu(int cpu)
+{
+ return rcu_dynticks_in_eqs(rcu_dynticks_snap(cpu));
}
/*
@@ -328,29 +314,26 @@ static bool rcu_dynticks_in_eqs(int snap)
*/
static bool rcu_dynticks_in_eqs_since(struct rcu_data *rdp, int snap)
{
- return snap != rcu_dynticks_snap(rdp);
+ return snap != rcu_dynticks_snap(rdp->cpu);
}
/*
- * Set the special (bottom) bit of the specified CPU so that it
- * will take special action (such as flushing its TLB) on the
- * next exit from an extended quiescent state. Returns true if
- * the bit was successfully set, or false if the CPU was not in
- * an extended quiescent state.
+ * Return true if the referenced integer is zero while the specified
+ * CPU remains within a single extended quiescent state.
*/
-bool rcu_eqs_special_set(int cpu)
+bool rcu_dynticks_zero_in_eqs(int cpu, int *vp)
{
- int old;
- int new;
- struct rcu_data *rdp = &per_cpu(rcu_data, cpu);
+ int snap;
- do {
- old = atomic_read(&rdp->dynticks);
- if (old & RCU_DYNTICK_CTRL_CTR)
- return false;
- new = old | RCU_DYNTICK_CTRL_MASK;
- } while (atomic_cmpxchg(&rdp->dynticks, old, new) != old);
- return true;
+ // If not quiescent, force back to earlier extended quiescent state.
+ snap = ct_dynticks_cpu(cpu) & ~RCU_DYNTICKS_IDX;
+ smp_rmb(); // Order ->dynticks and *vp reads.
+ if (READ_ONCE(*vp))
+ return false; // Non-zero, so report failure;
+ smp_rmb(); // Order *vp read and ->dynticks re-read.
+
+ // If still in the same extended quiescent state, we are good!
+ return snap == ct_dynticks_cpu(cpu);
}
/*
@@ -364,58 +347,76 @@ bool rcu_eqs_special_set(int cpu)
*
* The caller must have disabled interrupts and must not be idle.
*/
-void rcu_momentary_dyntick_idle(void)
+notrace void rcu_momentary_dyntick_idle(void)
{
- int special;
+ int seq;
raw_cpu_write(rcu_data.rcu_need_heavy_qs, false);
- special = atomic_add_return(2 * RCU_DYNTICK_CTRL_CTR,
- &this_cpu_ptr(&rcu_data)->dynticks);
+ seq = ct_state_inc(2 * RCU_DYNTICKS_IDX);
/* It is illegal to call this from idle state. */
- WARN_ON_ONCE(!(special & RCU_DYNTICK_CTRL_CTR));
+ WARN_ON_ONCE(!(seq & RCU_DYNTICKS_IDX));
rcu_preempt_deferred_qs(current);
}
EXPORT_SYMBOL_GPL(rcu_momentary_dyntick_idle);
/**
- * rcu_is_cpu_rrupt_from_idle - see if interrupted from idle
+ * rcu_is_cpu_rrupt_from_idle - see if 'interrupted' from idle
*
* If the current CPU is idle and running at a first-level (not nested)
- * interrupt from idle, return true. The caller must have at least
- * disabled preemption.
+ * interrupt, or directly, from idle, return true.
+ *
+ * The caller must have at least disabled IRQs.
*/
static int rcu_is_cpu_rrupt_from_idle(void)
{
- /* Called only from within the scheduling-clock interrupt */
- lockdep_assert_in_irq();
+ long nesting;
+
+ /*
+ * Usually called from the tick; but also used from smp_function_call()
+ * for expedited grace periods. This latter can result in running from
+ * the idle task, instead of an actual IPI.
+ */
+ lockdep_assert_irqs_disabled();
/* Check for counter underflows */
- RCU_LOCKDEP_WARN(__this_cpu_read(rcu_data.dynticks_nesting) < 0,
+ RCU_LOCKDEP_WARN(ct_dynticks_nesting() < 0,
"RCU dynticks_nesting counter underflow!");
- RCU_LOCKDEP_WARN(__this_cpu_read(rcu_data.dynticks_nmi_nesting) <= 0,
+ RCU_LOCKDEP_WARN(ct_dynticks_nmi_nesting() <= 0,
"RCU dynticks_nmi_nesting counter underflow/zero!");
/* Are we at first interrupt nesting level? */
- if (__this_cpu_read(rcu_data.dynticks_nmi_nesting) != 1)
+ nesting = ct_dynticks_nmi_nesting();
+ if (nesting > 1)
return false;
+ /*
+ * If we're not in an interrupt, we must be in the idle task!
+ */
+ WARN_ON_ONCE(!nesting && !is_idle_task(current));
+
/* Does CPU appear to be idle from an RCU standpoint? */
- return __this_cpu_read(rcu_data.dynticks_nesting) == 0;
+ return ct_dynticks_nesting() == 0;
}
-#define DEFAULT_RCU_BLIMIT 10 /* Maximum callbacks per rcu_do_batch ... */
-#define DEFAULT_MAX_RCU_BLIMIT 10000 /* ... even during callback flood. */
+#define DEFAULT_RCU_BLIMIT (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD) ? 1000 : 10)
+ // Maximum callbacks per rcu_do_batch ...
+#define DEFAULT_MAX_RCU_BLIMIT 10000 // ... even during callback flood.
static long blimit = DEFAULT_RCU_BLIMIT;
-#define DEFAULT_RCU_QHIMARK 10000 /* If this many pending, ignore blimit. */
+#define DEFAULT_RCU_QHIMARK 10000 // If this many pending, ignore blimit.
static long qhimark = DEFAULT_RCU_QHIMARK;
-#define DEFAULT_RCU_QLOMARK 100 /* Once only this many pending, use blimit. */
+#define DEFAULT_RCU_QLOMARK 100 // Once only this many pending, use blimit.
static long qlowmark = DEFAULT_RCU_QLOMARK;
+#define DEFAULT_RCU_QOVLD_MULT 2
+#define DEFAULT_RCU_QOVLD (DEFAULT_RCU_QOVLD_MULT * DEFAULT_RCU_QHIMARK)
+static long qovld = DEFAULT_RCU_QOVLD; // If this many pending, hammer QS.
+static long qovld_calc = -1; // No pre-initialization lock acquisitions!
module_param(blimit, long, 0444);
module_param(qhimark, long, 0444);
module_param(qlowmark, long, 0444);
+module_param(qovld, long, 0444);
-static ulong jiffies_till_first_fqs = ULONG_MAX;
+static ulong jiffies_till_first_fqs = IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD) ? 0 : ULONG_MAX;
static ulong jiffies_till_next_fqs = ULONG_MAX;
static bool rcu_kick_kthreads;
static int rcu_divisor = 7;
@@ -482,12 +483,12 @@ static int param_set_next_fqs_jiffies(const char *val, const struct kernel_param
return ret;
}
-static struct kernel_param_ops first_fqs_jiffies_ops = {
+static const struct kernel_param_ops first_fqs_jiffies_ops = {
.set = param_set_first_fqs_jiffies,
.get = param_get_ulong,
};
-static struct kernel_param_ops next_fqs_jiffies_ops = {
+static const struct kernel_param_ops next_fqs_jiffies_ops = {
.set = param_set_next_fqs_jiffies,
.get = param_get_ulong,
};
@@ -545,346 +546,142 @@ void rcutorture_get_gp_data(enum rcutorture_type test_type, int *flags,
}
EXPORT_SYMBOL_GPL(rcutorture_get_gp_data);
+#if defined(CONFIG_NO_HZ_FULL) && (!defined(CONFIG_GENERIC_ENTRY) || !defined(CONFIG_KVM_XFER_TO_GUEST_WORK))
/*
- * Enter an RCU extended quiescent state, which can be either the
- * idle loop or adaptive-tickless usermode execution.
- *
- * We crowbar the ->dynticks_nmi_nesting field to zero to allow for
- * the possibility of usermode upcalls having messed up our count
- * of interrupt nesting level during the prior busy period.
+ * An empty function that will trigger a reschedule on
+ * IRQ tail once IRQs get re-enabled on userspace/guest resume.
*/
-static void rcu_eqs_enter(bool user)
+static void late_wakeup_func(struct irq_work *work)
{
- struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
-
- WARN_ON_ONCE(rdp->dynticks_nmi_nesting != DYNTICK_IRQ_NONIDLE);
- WRITE_ONCE(rdp->dynticks_nmi_nesting, 0);
- WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) &&
- rdp->dynticks_nesting == 0);
- if (rdp->dynticks_nesting != 1) {
- rdp->dynticks_nesting--;
- return;
- }
-
- lockdep_assert_irqs_disabled();
- trace_rcu_dyntick(TPS("Start"), rdp->dynticks_nesting, 0, atomic_read(&rdp->dynticks));
- WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !user && !is_idle_task(current));
- rdp = this_cpu_ptr(&rcu_data);
- do_nocb_deferred_wakeup(rdp);
- rcu_prepare_for_idle();
- rcu_preempt_deferred_qs(current);
- WRITE_ONCE(rdp->dynticks_nesting, 0); /* Avoid irq-access tearing. */
- rcu_dynticks_eqs_enter();
- rcu_dynticks_task_enter();
}
-/**
- * rcu_idle_enter - inform RCU that current CPU is entering idle
- *
- * Enter idle mode, in other words, -leave- the mode in which RCU
- * read-side critical sections can occur. (Though RCU read-side
- * critical sections can occur in irq handlers in idle, a possibility
- * handled by irq_enter() and irq_exit().)
- *
- * If you add or remove a call to rcu_idle_enter(), be sure to test with
- * CONFIG_RCU_EQS_DEBUG=y.
- */
-void rcu_idle_enter(void)
-{
- lockdep_assert_irqs_disabled();
- rcu_eqs_enter(false);
-}
-
-#ifdef CONFIG_NO_HZ_FULL
-/**
- * rcu_user_enter - inform RCU that we are resuming userspace.
- *
- * Enter RCU idle mode right before resuming userspace. No use of RCU
- * is permitted between this call and rcu_user_exit(). This way the
- * CPU doesn't need to maintain the tick for RCU maintenance purposes
- * when the CPU runs in userspace.
- *
- * If you add or remove a call to rcu_user_enter(), be sure to test with
- * CONFIG_RCU_EQS_DEBUG=y.
- */
-void rcu_user_enter(void)
-{
- lockdep_assert_irqs_disabled();
- rcu_eqs_enter(true);
-}
-#endif /* CONFIG_NO_HZ_FULL */
+static DEFINE_PER_CPU(struct irq_work, late_wakeup_work) =
+ IRQ_WORK_INIT(late_wakeup_func);
/*
- * If we are returning from the outermost NMI handler that interrupted an
- * RCU-idle period, update rdp->dynticks and rdp->dynticks_nmi_nesting
- * to let the RCU grace-period handling know that the CPU is back to
- * being RCU-idle.
+ * If either:
+ *
+ * 1) the task is about to enter in guest mode and $ARCH doesn't support KVM generic work
+ * 2) the task is about to enter in user mode and $ARCH doesn't support generic entry.
*
- * If you add or remove a call to rcu_nmi_exit_common(), be sure to test
- * with CONFIG_RCU_EQS_DEBUG=y.
+ * In these cases the late RCU wake ups aren't supported in the resched loops and our
+ * last resort is to fire a local irq_work that will trigger a reschedule once IRQs
+ * get re-enabled again.
*/
-static __always_inline void rcu_nmi_exit_common(bool irq)
+noinstr void rcu_irq_work_resched(void)
{
struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
- /*
- * Check for ->dynticks_nmi_nesting underflow and bad ->dynticks.
- * (We are exiting an NMI handler, so RCU better be paying attention
- * to us!)
- */
- WARN_ON_ONCE(rdp->dynticks_nmi_nesting <= 0);
- WARN_ON_ONCE(rcu_dynticks_curr_cpu_in_eqs());
-
- /*
- * If the nesting level is not 1, the CPU wasn't RCU-idle, so
- * leave it in non-RCU-idle state.
- */
- if (rdp->dynticks_nmi_nesting != 1) {
- trace_rcu_dyntick(TPS("--="), rdp->dynticks_nmi_nesting, rdp->dynticks_nmi_nesting - 2,
- atomic_read(&rdp->dynticks));
- WRITE_ONCE(rdp->dynticks_nmi_nesting, /* No store tearing. */
- rdp->dynticks_nmi_nesting - 2);
+ if (IS_ENABLED(CONFIG_GENERIC_ENTRY) && !(current->flags & PF_VCPU))
return;
- }
-
- /* This NMI interrupted an RCU-idle CPU, restore RCU-idleness. */
- trace_rcu_dyntick(TPS("Startirq"), rdp->dynticks_nmi_nesting, 0, atomic_read(&rdp->dynticks));
- WRITE_ONCE(rdp->dynticks_nmi_nesting, 0); /* Avoid store tearing. */
-
- if (irq)
- rcu_prepare_for_idle();
-
- rcu_dynticks_eqs_enter();
-
- if (irq)
- rcu_dynticks_task_enter();
-}
-
-/**
- * rcu_nmi_exit - inform RCU of exit from NMI context
- *
- * If you add or remove a call to rcu_nmi_exit(), be sure to test
- * with CONFIG_RCU_EQS_DEBUG=y.
- */
-void rcu_nmi_exit(void)
-{
- rcu_nmi_exit_common(false);
-}
-/**
- * rcu_irq_exit - inform RCU that current CPU is exiting irq towards idle
- *
- * Exit from an interrupt handler, which might possibly result in entering
- * idle mode, in other words, leaving the mode in which read-side critical
- * sections can occur. The caller must have disabled interrupts.
- *
- * This code assumes that the idle loop never does anything that might
- * result in unbalanced calls to irq_enter() and irq_exit(). If your
- * architecture's idle loop violates this assumption, RCU will give you what
- * you deserve, good and hard. But very infrequently and irreproducibly.
- *
- * Use things like work queues to work around this limitation.
- *
- * You have been warned.
- *
- * If you add or remove a call to rcu_irq_exit(), be sure to test with
- * CONFIG_RCU_EQS_DEBUG=y.
- */
-void rcu_irq_exit(void)
-{
- lockdep_assert_irqs_disabled();
- rcu_nmi_exit_common(true);
-}
-
-/*
- * Wrapper for rcu_irq_exit() where interrupts are enabled.
- *
- * If you add or remove a call to rcu_irq_exit_irqson(), be sure to test
- * with CONFIG_RCU_EQS_DEBUG=y.
- */
-void rcu_irq_exit_irqson(void)
-{
- unsigned long flags;
-
- local_irq_save(flags);
- rcu_irq_exit();
- local_irq_restore(flags);
-}
-
-/*
- * Exit an RCU extended quiescent state, which can be either the
- * idle loop or adaptive-tickless usermode execution.
- *
- * We crowbar the ->dynticks_nmi_nesting field to DYNTICK_IRQ_NONIDLE to
- * allow for the possibility of usermode upcalls messing up our count of
- * interrupt nesting level during the busy period that is just now starting.
- */
-static void rcu_eqs_exit(bool user)
-{
- struct rcu_data *rdp;
- long oldval;
-
- lockdep_assert_irqs_disabled();
- rdp = this_cpu_ptr(&rcu_data);
- oldval = rdp->dynticks_nesting;
- WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && oldval < 0);
- if (oldval) {
- rdp->dynticks_nesting++;
+ if (IS_ENABLED(CONFIG_KVM_XFER_TO_GUEST_WORK) && (current->flags & PF_VCPU))
return;
+
+ instrumentation_begin();
+ if (do_nocb_deferred_wakeup(rdp) && need_resched()) {
+ irq_work_queue(this_cpu_ptr(&late_wakeup_work));
}
- rcu_dynticks_task_exit();
- rcu_dynticks_eqs_exit();
- rcu_cleanup_after_idle();
- trace_rcu_dyntick(TPS("End"), rdp->dynticks_nesting, 1, atomic_read(&rdp->dynticks));
- WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !user && !is_idle_task(current));
- WRITE_ONCE(rdp->dynticks_nesting, 1);
- WARN_ON_ONCE(rdp->dynticks_nmi_nesting);
- WRITE_ONCE(rdp->dynticks_nmi_nesting, DYNTICK_IRQ_NONIDLE);
+ instrumentation_end();
}
+#endif /* #if defined(CONFIG_NO_HZ_FULL) && (!defined(CONFIG_GENERIC_ENTRY) || !defined(CONFIG_KVM_XFER_TO_GUEST_WORK)) */
+#ifdef CONFIG_PROVE_RCU
/**
- * rcu_idle_exit - inform RCU that current CPU is leaving idle
- *
- * Exit idle mode, in other words, -enter- the mode in which RCU
- * read-side critical sections can occur.
- *
- * If you add or remove a call to rcu_idle_exit(), be sure to test with
- * CONFIG_RCU_EQS_DEBUG=y.
+ * rcu_irq_exit_check_preempt - Validate that scheduling is possible
*/
-void rcu_idle_exit(void)
+void rcu_irq_exit_check_preempt(void)
{
- unsigned long flags;
+ lockdep_assert_irqs_disabled();
- local_irq_save(flags);
- rcu_eqs_exit(false);
- local_irq_restore(flags);
+ RCU_LOCKDEP_WARN(ct_dynticks_nesting() <= 0,
+ "RCU dynticks_nesting counter underflow/zero!");
+ RCU_LOCKDEP_WARN(ct_dynticks_nmi_nesting() !=
+ DYNTICK_IRQ_NONIDLE,
+ "Bad RCU dynticks_nmi_nesting counter\n");
+ RCU_LOCKDEP_WARN(rcu_dynticks_curr_cpu_in_eqs(),
+ "RCU in extended quiescent state!");
}
+#endif /* #ifdef CONFIG_PROVE_RCU */
#ifdef CONFIG_NO_HZ_FULL
/**
- * rcu_user_exit - inform RCU that we are exiting userspace.
+ * __rcu_irq_enter_check_tick - Enable scheduler tick on CPU if RCU needs it.
*
- * Exit RCU idle mode while entering the kernel because it can
- * run a RCU read side critical section anytime.
+ * The scheduler tick is not normally enabled when CPUs enter the kernel
+ * from nohz_full userspace execution. After all, nohz_full userspace
+ * execution is an RCU quiescent state and the time executing in the kernel
+ * is quite short. Except of course when it isn't. And it is not hard to
+ * cause a large system to spend tens of seconds or even minutes looping
+ * in the kernel, which can cause a number of problems, include RCU CPU
+ * stall warnings.
*
- * If you add or remove a call to rcu_user_exit(), be sure to test with
- * CONFIG_RCU_EQS_DEBUG=y.
- */
-void rcu_user_exit(void)
-{
- rcu_eqs_exit(1);
-}
-#endif /* CONFIG_NO_HZ_FULL */
-
-/**
- * rcu_nmi_enter_common - inform RCU of entry to NMI context
- * @irq: Is this call from rcu_irq_enter?
- *
- * If the CPU was idle from RCU's viewpoint, update rdp->dynticks and
- * rdp->dynticks_nmi_nesting to let the RCU grace-period handling know
- * that the CPU is active. This implementation permits nested NMIs, as
- * long as the nesting level does not overflow an int. (You will probably
- * run out of stack space first.)
+ * Therefore, if a nohz_full CPU fails to report a quiescent state
+ * in a timely manner, the RCU grace-period kthread sets that CPU's
+ * ->rcu_urgent_qs flag with the expectation that the next interrupt or
+ * exception will invoke this function, which will turn on the scheduler
+ * tick, which will enable RCU to detect that CPU's quiescent states,
+ * for example, due to cond_resched() calls in CONFIG_PREEMPT=n kernels.
+ * The tick will be disabled once a quiescent state is reported for
+ * this CPU.
*
- * If you add or remove a call to rcu_nmi_enter_common(), be sure to test
- * with CONFIG_RCU_EQS_DEBUG=y.
+ * Of course, in carefully tuned systems, there might never be an
+ * interrupt or exception. In that case, the RCU grace-period kthread
+ * will eventually cause one to happen. However, in less carefully
+ * controlled environments, this function allows RCU to get what it
+ * needs without creating otherwise useless interruptions.
*/
-static __always_inline void rcu_nmi_enter_common(bool irq)
+void __rcu_irq_enter_check_tick(void)
{
- long incby = 2;
struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
- /* Complain about underflow. */
- WARN_ON_ONCE(rdp->dynticks_nmi_nesting < 0);
-
- /*
- * If idle from RCU viewpoint, atomically increment ->dynticks
- * to mark non-idle and increment ->dynticks_nmi_nesting by one.
- * Otherwise, increment ->dynticks_nmi_nesting by two. This means
- * if ->dynticks_nmi_nesting is equal to one, we are guaranteed
- * to be in the outermost NMI handler that interrupted an RCU-idle
- * period (observation due to Andy Lutomirski).
- */
- if (rcu_dynticks_curr_cpu_in_eqs()) {
-
- if (irq)
- rcu_dynticks_task_exit();
-
- rcu_dynticks_eqs_exit();
+ // If we're here from NMI there's nothing to do.
+ if (in_nmi())
+ return;
- if (irq)
- rcu_cleanup_after_idle();
+ RCU_LOCKDEP_WARN(rcu_dynticks_curr_cpu_in_eqs(),
+ "Illegal rcu_irq_enter_check_tick() from extended quiescent state");
- incby = 1;
- } else if (tick_nohz_full_cpu(rdp->cpu) &&
- rdp->dynticks_nmi_nesting == DYNTICK_IRQ_NONIDLE &&
- READ_ONCE(rdp->rcu_urgent_qs) && !rdp->rcu_forced_tick) {
- raw_spin_lock_rcu_node(rdp->mynode);
- // Recheck under lock.
- if (rdp->rcu_urgent_qs && !rdp->rcu_forced_tick) {
- rdp->rcu_forced_tick = true;
- tick_dep_set_cpu(rdp->cpu, TICK_DEP_BIT_RCU);
- }
- raw_spin_unlock_rcu_node(rdp->mynode);
+ if (!tick_nohz_full_cpu(rdp->cpu) ||
+ !READ_ONCE(rdp->rcu_urgent_qs) ||
+ READ_ONCE(rdp->rcu_forced_tick)) {
+ // RCU doesn't need nohz_full help from this CPU, or it is
+ // already getting that help.
+ return;
}
- trace_rcu_dyntick(incby == 1 ? TPS("Endirq") : TPS("++="),
- rdp->dynticks_nmi_nesting,
- rdp->dynticks_nmi_nesting + incby, atomic_read(&rdp->dynticks));
- WRITE_ONCE(rdp->dynticks_nmi_nesting, /* Prevent store tearing. */
- rdp->dynticks_nmi_nesting + incby);
- barrier();
-}
-
-/**
- * rcu_nmi_enter - inform RCU of entry to NMI context
- */
-void rcu_nmi_enter(void)
-{
- rcu_nmi_enter_common(false);
-}
-NOKPROBE_SYMBOL(rcu_nmi_enter);
-/**
- * rcu_irq_enter - inform RCU that current CPU is entering irq away from idle
- *
- * Enter an interrupt handler, which might possibly result in exiting
- * idle mode, in other words, entering the mode in which read-side critical
- * sections can occur. The caller must have disabled interrupts.
- *
- * Note that the Linux kernel is fully capable of entering an interrupt
- * handler that it never exits, for example when doing upcalls to user mode!
- * This code assumes that the idle loop never does upcalls to user mode.
- * If your architecture's idle loop does do upcalls to user mode (or does
- * anything else that results in unbalanced calls to the irq_enter() and
- * irq_exit() functions), RCU will give you what you deserve, good and hard.
- * But very infrequently and irreproducibly.
- *
- * Use things like work queues to work around this limitation.
- *
- * You have been warned.
- *
- * If you add or remove a call to rcu_irq_enter(), be sure to test with
- * CONFIG_RCU_EQS_DEBUG=y.
- */
-void rcu_irq_enter(void)
-{
- lockdep_assert_irqs_disabled();
- rcu_nmi_enter_common(true);
+ // We get here only when not in an extended quiescent state and
+ // from interrupts (as opposed to NMIs). Therefore, (1) RCU is
+ // already watching and (2) The fact that we are in an interrupt
+ // handler and that the rcu_node lock is an irq-disabled lock
+ // prevents self-deadlock. So we can safely recheck under the lock.
+ // Note that the nohz_full state currently cannot change.
+ raw_spin_lock_rcu_node(rdp->mynode);
+ if (rdp->rcu_urgent_qs && !rdp->rcu_forced_tick) {
+ // A nohz_full CPU is in the kernel and RCU needs a
+ // quiescent state. Turn on the tick!
+ WRITE_ONCE(rdp->rcu_forced_tick, true);
+ tick_dep_set_cpu(rdp->cpu, TICK_DEP_BIT_RCU);
+ }
+ raw_spin_unlock_rcu_node(rdp->mynode);
}
+#endif /* CONFIG_NO_HZ_FULL */
/*
- * Wrapper for rcu_irq_enter() where interrupts are enabled.
+ * Check to see if any future non-offloaded RCU-related work will need
+ * to be done by the current CPU, even if none need be done immediately,
+ * returning 1 if so. This function is part of the RCU implementation;
+ * it is -not- an exported member of the RCU API. This is used by
+ * the idle-entry code to figure out whether it is safe to disable the
+ * scheduler-clock interrupt.
*
- * If you add or remove a call to rcu_irq_enter_irqson(), be sure to test
- * with CONFIG_RCU_EQS_DEBUG=y.
+ * Just check whether or not this CPU has non-offloaded RCU callbacks
+ * queued.
*/
-void rcu_irq_enter_irqson(void)
+int rcu_needs_cpu(void)
{
- unsigned long flags;
-
- local_irq_save(flags);
- rcu_irq_enter();
- local_irq_restore(flags);
+ return !rcu_segcblist_empty(&this_cpu_ptr(&rcu_data)->cblist) &&
+ !rcu_rdp_is_offloaded(this_cpu_ptr(&rcu_data));
}
/*
@@ -899,7 +696,7 @@ static void rcu_disable_urgency_upon_qs(struct rcu_data *rdp)
WRITE_ONCE(rdp->rcu_need_heavy_qs, false);
if (tick_nohz_full_cpu(rdp->cpu) && rdp->rcu_forced_tick) {
tick_dep_clear_cpu(rdp->cpu, TICK_DEP_BIT_RCU);
- rdp->rcu_forced_tick = false;
+ WRITE_ONCE(rdp->rcu_forced_tick, false);
}
}
@@ -910,8 +707,11 @@ static void rcu_disable_urgency_upon_qs(struct rcu_data *rdp)
* CPU can safely enter RCU read-side critical sections. In other words,
* if the current CPU is not in its idle loop or is in an interrupt or
* NMI handler, return true.
+ *
+ * Make notrace because it can be called by the internal functions of
+ * ftrace, and making this notrace removes unnecessary recursion calls.
*/
-bool notrace rcu_is_watching(void)
+notrace bool rcu_is_watching(void)
{
bool ret;
@@ -958,17 +758,22 @@ void rcu_request_urgent_qs_task(struct task_struct *t)
bool rcu_lockdep_current_cpu_online(void)
{
struct rcu_data *rdp;
- struct rcu_node *rnp;
bool ret = false;
if (in_nmi() || !rcu_scheduler_fully_active)
return true;
- preempt_disable();
+ preempt_disable_notrace();
rdp = this_cpu_ptr(&rcu_data);
- rnp = rdp->mynode;
- if (rdp->grpmask & rcu_rnp_online_cpus(rnp))
+ /*
+ * Strictly, we care here about the case where the current CPU is
+ * in rcu_cpu_starting() and thus has an excuse for rdp->grpmask
+ * not being up to date. So arch_spin_is_locked() might have a
+ * false positive if it's held by some *other* CPU, but that's
+ * OK because that just means a false *negative* on the warning.
+ */
+ if (rcu_rdp_cpu_online(rdp) || arch_spin_is_locked(&rcu_state.ofl_lock))
ret = true;
- preempt_enable();
+ preempt_enable_notrace();
return ret;
}
EXPORT_SYMBOL_GPL(rcu_lockdep_current_cpu_online);
@@ -976,7 +781,7 @@ EXPORT_SYMBOL_GPL(rcu_lockdep_current_cpu_online);
#endif /* #if defined(CONFIG_PROVE_RCU) && defined(CONFIG_HOTPLUG_CPU) */
/*
- * We are reporting a quiescent state on behalf of some other CPU, so
+ * When trying to report a quiescent state on behalf of some other CPU,
* it is our responsibility to check for and handle potential overflow
* of the rcu_node ->gp_seq counter with respect to the rcu_data counters.
* After all, the CPU might be in deep idle state, and thus executing no
@@ -999,7 +804,7 @@ static void rcu_gpnum_ovf(struct rcu_node *rnp, struct rcu_data *rdp)
*/
static int dyntick_save_progress_counter(struct rcu_data *rdp)
{
- rdp->dynticks_snap = rcu_dynticks_snap(rdp);
+ rdp->dynticks_snap = rcu_dynticks_snap(rdp->cpu);
if (rcu_dynticks_in_eqs(rdp->dynticks_snap)) {
trace_rcu_fqs(rcu_state.name, rdp->gp_seq, rdp->cpu, TPS("dti"));
rcu_gpnum_ovf(rdp->mynode, rdp);
@@ -1017,8 +822,6 @@ static int dyntick_save_progress_counter(struct rcu_data *rdp)
static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
{
unsigned long jtsq;
- bool *rnhqp;
- bool *ruqp;
struct rcu_node *rnp = rdp->mynode;
/*
@@ -1035,22 +838,35 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
return 1;
}
- /* If waiting too long on an offline CPU, complain. */
- if (!(rdp->grpmask & rcu_rnp_online_cpus(rnp)) &&
- time_after(jiffies, rcu_state.gp_start + HZ)) {
- bool onl;
+ /*
+ * Complain if a CPU that is considered to be offline from RCU's
+ * perspective has not yet reported a quiescent state. After all,
+ * the offline CPU should have reported a quiescent state during
+ * the CPU-offline process, or, failing that, by rcu_gp_init()
+ * if it ran concurrently with either the CPU going offline or the
+ * last task on a leaf rcu_node structure exiting its RCU read-side
+ * critical section while all CPUs corresponding to that structure
+ * are offline. This added warning detects bugs in any of these
+ * code paths.
+ *
+ * The rcu_node structure's ->lock is held here, which excludes
+ * the relevant portions the CPU-hotplug code, the grace-period
+ * initialization code, and the rcu_read_unlock() code paths.
+ *
+ * For more detail, please refer to the "Hotplug CPU" section
+ * of RCU's Requirements documentation.
+ */
+ if (WARN_ON_ONCE(!rcu_rdp_cpu_online(rdp))) {
struct rcu_node *rnp1;
- WARN_ON(1); /* Offline CPUs are supposed to report QS! */
pr_info("%s: grp: %d-%d level: %d ->gp_seq %ld ->completedqs %ld\n",
__func__, rnp->grplo, rnp->grphi, rnp->level,
(long)rnp->gp_seq, (long)rnp->completedqs);
for (rnp1 = rnp; rnp1; rnp1 = rnp1->parent)
pr_info("%s: %d:%d ->qsmask %#lx ->qsmaskinit %#lx ->qsmaskinitnext %#lx ->rcu_gp_init_mask %#lx\n",
__func__, rnp1->grplo, rnp1->grphi, rnp1->qsmask, rnp1->qsmaskinit, rnp1->qsmaskinitnext, rnp1->rcu_gp_init_mask);
- onl = !!(rdp->grpmask & rcu_rnp_online_cpus(rnp));
pr_info("%s %d: %c online: %ld(%d) offline: %ld(%d)\n",
- __func__, rdp->cpu, ".o"[onl],
+ __func__, rdp->cpu, ".o"[rcu_rdp_cpu_online(rdp)],
(long)rdp->rcu_onl_gp_seq, rdp->rcu_onl_gp_flags,
(long)rdp->rcu_ofl_gp_seq, rdp->rcu_ofl_gp_flags);
return 1; /* Break things loose after complaining. */
@@ -1068,16 +884,15 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
* is set way high.
*/
jtsq = READ_ONCE(jiffies_to_sched_qs);
- ruqp = per_cpu_ptr(&rcu_data.rcu_urgent_qs, rdp->cpu);
- rnhqp = &per_cpu(rcu_data.rcu_need_heavy_qs, rdp->cpu);
- if (!READ_ONCE(*rnhqp) &&
+ if (!READ_ONCE(rdp->rcu_need_heavy_qs) &&
(time_after(jiffies, rcu_state.gp_start + jtsq * 2) ||
- time_after(jiffies, rcu_state.jiffies_resched))) {
- WRITE_ONCE(*rnhqp, true);
+ time_after(jiffies, rcu_state.jiffies_resched) ||
+ rcu_state.cbovld)) {
+ WRITE_ONCE(rdp->rcu_need_heavy_qs, true);
/* Store rcu_need_heavy_qs before rcu_urgent_qs. */
- smp_store_release(ruqp, true);
+ smp_store_release(&rdp->rcu_urgent_qs, true);
} else if (time_after(jiffies, rcu_state.gp_start + jtsq)) {
- WRITE_ONCE(*ruqp, true);
+ WRITE_ONCE(rdp->rcu_urgent_qs, true);
}
/*
@@ -1089,9 +904,9 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
* So hit them over the head with the resched_cpu() hammer!
*/
if (tick_nohz_full_cpu(rdp->cpu) &&
- time_after(jiffies,
- READ_ONCE(rdp->last_fqs_resched) + jtsq * 3)) {
- WRITE_ONCE(*ruqp, true);
+ (time_after(jiffies, READ_ONCE(rdp->last_fqs_resched) + jtsq * 3) ||
+ rcu_state.cbovld)) {
+ WRITE_ONCE(rdp->rcu_urgent_qs, true);
resched_cpu(rdp->cpu);
WRITE_ONCE(rdp->last_fqs_resched, jiffies);
}
@@ -1112,7 +927,6 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
if (IS_ENABLED(CONFIG_IRQ_WORK) &&
!rdp->rcu_iw_pending && rdp->rcu_iw_gp_seq != rnp->gp_seq &&
(rnp->ffmask & rdp->grpmask)) {
- init_irq_work(&rdp->rcu_iw, rcu_iw_handler);
rdp->rcu_iw_pending = true;
rdp->rcu_iw_gp_seq = rnp->gp_seq;
irq_work_queue_on(&rdp->rcu_iw, rdp->cpu);
@@ -1126,8 +940,9 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
static void trace_rcu_this_gp(struct rcu_node *rnp, struct rcu_data *rdp,
unsigned long gp_seq_req, const char *s)
{
- trace_rcu_future_grace_period(rcu_state.name, rnp->gp_seq, gp_seq_req,
- rnp->level, rnp->grplo, rnp->grphi, s);
+ trace_rcu_future_grace_period(rcu_state.name, READ_ONCE(rnp->gp_seq),
+ gp_seq_req, rnp->level,
+ rnp->grplo, rnp->grphi, s);
}
/*
@@ -1174,7 +989,7 @@ static bool rcu_start_this_gp(struct rcu_node *rnp_start, struct rcu_data *rdp,
TPS("Prestarted"));
goto unlock_out;
}
- rnp->gp_seq_needed = gp_seq_req;
+ WRITE_ONCE(rnp->gp_seq_needed, gp_seq_req);
if (rcu_seq_state(rcu_seq_current(&rnp->gp_seq))) {
/*
* We just marked the leaf or internal node, and a
@@ -1199,18 +1014,18 @@ static bool rcu_start_this_gp(struct rcu_node *rnp_start, struct rcu_data *rdp,
}
trace_rcu_this_gp(rnp, rdp, gp_seq_req, TPS("Startedroot"));
WRITE_ONCE(rcu_state.gp_flags, rcu_state.gp_flags | RCU_GP_FLAG_INIT);
- rcu_state.gp_req_activity = jiffies;
- if (!rcu_state.gp_kthread) {
+ WRITE_ONCE(rcu_state.gp_req_activity, jiffies);
+ if (!READ_ONCE(rcu_state.gp_kthread)) {
trace_rcu_this_gp(rnp, rdp, gp_seq_req, TPS("NoGPkthread"));
goto unlock_out;
}
- trace_rcu_grace_period(rcu_state.name, READ_ONCE(rcu_state.gp_seq), TPS("newreq"));
+ trace_rcu_grace_period(rcu_state.name, data_race(rcu_state.gp_seq), TPS("newreq"));
ret = true; /* Caller must wake GP kthread. */
unlock_out:
/* Push furthest requested GP to leaf node and rcu_data structure. */
if (ULONG_CMP_LT(gp_seq_req, rnp->gp_seq_needed)) {
- rnp_start->gp_seq_needed = rnp->gp_seq_needed;
- rdp->gp_seq_needed = rnp->gp_seq_needed;
+ WRITE_ONCE(rnp_start->gp_seq_needed, rnp->gp_seq_needed);
+ WRITE_ONCE(rdp->gp_seq_needed, rnp->gp_seq_needed);
}
if (rnp != rnp_start)
raw_spin_unlock_rcu_node(rnp);
@@ -1235,12 +1050,13 @@ static bool rcu_future_gp_cleanup(struct rcu_node *rnp)
}
/*
- * Awaken the grace-period kthread. Don't do a self-awaken (unless in
- * an interrupt or softirq handler), and don't bother awakening when there
- * is nothing for the grace-period kthread to do (as in several CPUs raced
- * to awaken, and we lost), and finally don't try to awaken a kthread that
- * has not yet been created. If all those checks are passed, track some
- * debug information and awaken.
+ * Awaken the grace-period kthread. Don't do a self-awaken (unless in an
+ * interrupt or softirq handler, in which case we just might immediately
+ * sleep upon return, resulting in a grace-period hang), and don't bother
+ * awakening when there is nothing for the grace-period kthread to do
+ * (as in several CPUs raced to awaken, we lost), and finally don't try
+ * to awaken a kthread that has not yet been created. If all those checks
+ * are passed, track some debug information and awaken.
*
* So why do the self-wakeup when in an interrupt or softirq handler
* in the grace-period kthread's context? Because the kthread might have
@@ -1250,10 +1066,10 @@ static bool rcu_future_gp_cleanup(struct rcu_node *rnp)
*/
static void rcu_gp_kthread_wake(void)
{
- if ((current == rcu_state.gp_kthread &&
- !in_irq() && !in_serving_softirq()) ||
- !READ_ONCE(rcu_state.gp_flags) ||
- !rcu_state.gp_kthread)
+ struct task_struct *t = READ_ONCE(rcu_state.gp_kthread);
+
+ if ((current == t && !in_hardirq() && !in_serving_softirq()) ||
+ !READ_ONCE(rcu_state.gp_flags) || !t)
return;
WRITE_ONCE(rcu_state.gp_wake_time, jiffies);
WRITE_ONCE(rcu_state.gp_wake_seq, READ_ONCE(rcu_state.gp_seq));
@@ -1284,6 +1100,8 @@ static bool rcu_accelerate_cbs(struct rcu_node *rnp, struct rcu_data *rdp)
if (!rcu_segcblist_pend_cbs(&rdp->cblist))
return false;
+ trace_rcu_segcb_stats(&rdp->cblist, TPS("SegCbPreAcc"));
+
/*
* Callbacks are often registered with incomplete grace-period
* information. Something about the fact that getting exact
@@ -1300,9 +1118,12 @@ static bool rcu_accelerate_cbs(struct rcu_node *rnp, struct rcu_data *rdp)
/* Trace depending on how much we were able to accelerate. */
if (rcu_segcblist_restempty(&rdp->cblist, RCU_WAIT_TAIL))
- trace_rcu_grace_period(rcu_state.name, rdp->gp_seq, TPS("AccWaitCB"));
+ trace_rcu_grace_period(rcu_state.name, gp_seq_req, TPS("AccWaitCB"));
else
- trace_rcu_grace_period(rcu_state.name, rdp->gp_seq, TPS("AccReadyCB"));
+ trace_rcu_grace_period(rcu_state.name, gp_seq_req, TPS("AccReadyCB"));
+
+ trace_rcu_segcb_stats(&rdp->cblist, TPS("SegCbPostAcc"));
+
return ret;
}
@@ -1321,7 +1142,7 @@ static void rcu_accelerate_cbs_unlocked(struct rcu_node *rnp,
rcu_lockdep_assert_cblist_protected(rdp);
c = rcu_seq_snap(&rcu_state.gp_seq);
- if (!rdp->gpwrap && ULONG_CMP_GE(rdp->gp_seq_needed, c)) {
+ if (!READ_ONCE(rdp->gpwrap) && ULONG_CMP_GE(rdp->gp_seq_needed, c)) {
/* Old request still live, so mark recent callbacks. */
(void)rcu_segcblist_accelerate(&rdp->cblist, c);
return;
@@ -1370,14 +1191,28 @@ static void __maybe_unused rcu_advance_cbs_nowake(struct rcu_node *rnp,
struct rcu_data *rdp)
{
rcu_lockdep_assert_cblist_protected(rdp);
- if (!rcu_seq_state(rcu_seq_current(&rnp->gp_seq)) ||
- !raw_spin_trylock_rcu_node(rnp))
+ if (!rcu_seq_state(rcu_seq_current(&rnp->gp_seq)) || !raw_spin_trylock_rcu_node(rnp))
return;
- WARN_ON_ONCE(rcu_advance_cbs(rnp, rdp));
+ // The grace period cannot end while we hold the rcu_node lock.
+ if (rcu_seq_state(rcu_seq_current(&rnp->gp_seq)))
+ WARN_ON_ONCE(rcu_advance_cbs(rnp, rdp));
raw_spin_unlock_rcu_node(rnp);
}
/*
+ * In CONFIG_RCU_STRICT_GRACE_PERIOD=y kernels, attempt to generate a
+ * quiescent state. This is intended to be invoked when the CPU notices
+ * a new grace period.
+ */
+static void rcu_strict_gp_check_qs(void)
+{
+ if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD)) {
+ rcu_read_lock();
+ rcu_read_unlock();
+ }
+}
+
+/*
* Update CPU-local rcu_data state to record the beginnings and ends of
* grace periods. The caller must hold the ->lock of the leaf rcu_node
* structure corresponding to the current CPU, and must have irqs disabled.
@@ -1386,9 +1221,8 @@ static void __maybe_unused rcu_advance_cbs_nowake(struct rcu_node *rnp,
static bool __note_gp_changes(struct rcu_node *rnp, struct rcu_data *rdp)
{
bool ret = false;
- bool need_gp;
- const bool offloaded = IS_ENABLED(CONFIG_RCU_NOCB_CPU) &&
- rcu_segcblist_is_offloaded(&rdp->cblist);
+ bool need_qs;
+ const bool offloaded = rcu_rdp_is_offloaded(rdp);
raw_lockdep_assert_held_rcu_node(rnp);
@@ -1400,10 +1234,13 @@ static bool __note_gp_changes(struct rcu_node *rnp, struct rcu_data *rdp)
unlikely(READ_ONCE(rdp->gpwrap))) {
if (!offloaded)
ret = rcu_advance_cbs(rnp, rdp); /* Advance CBs. */
+ rdp->core_needs_qs = false;
trace_rcu_grace_period(rcu_state.name, rdp->gp_seq, TPS("cpuend"));
} else {
if (!offloaded)
ret = rcu_accelerate_cbs(rnp, rdp); /* Recent CBs. */
+ if (rdp->core_needs_qs)
+ rdp->core_needs_qs = !!(rnp->qsmask & rdp->grpmask);
}
/* Now handle the beginnings of any new-to-this-CPU grace periods. */
@@ -1415,14 +1252,16 @@ static bool __note_gp_changes(struct rcu_node *rnp, struct rcu_data *rdp)
* go looking for one.
*/
trace_rcu_grace_period(rcu_state.name, rnp->gp_seq, TPS("cpustart"));
- need_gp = !!(rnp->qsmask & rdp->grpmask);
- rdp->cpu_no_qs.b.norm = need_gp;
- rdp->core_needs_qs = need_gp;
+ need_qs = !!(rnp->qsmask & rdp->grpmask);
+ rdp->cpu_no_qs.b.norm = need_qs;
+ rdp->core_needs_qs = need_qs;
zero_cpu_stall_ticks(rdp);
}
rdp->gp_seq = rnp->gp_seq; /* Remember new grace-period state. */
if (ULONG_CMP_LT(rdp->gp_seq_needed, rnp->gp_seq_needed) || rdp->gpwrap)
- rdp->gp_seq_needed = rnp->gp_seq_needed;
+ WRITE_ONCE(rdp->gp_seq_needed, rnp->gp_seq_needed);
+ if (IS_ENABLED(CONFIG_PROVE_RCU) && READ_ONCE(rdp->gpwrap))
+ WRITE_ONCE(rdp->last_sched_clock, jiffies);
WRITE_ONCE(rdp->gpwrap, false);
rcu_gpnum_ovf(rnp, rdp);
return ret;
@@ -1444,22 +1283,158 @@ static void note_gp_changes(struct rcu_data *rdp)
}
needwake = __note_gp_changes(rnp, rdp);
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
+ rcu_strict_gp_check_qs();
if (needwake)
rcu_gp_kthread_wake();
}
+static atomic_t *rcu_gp_slow_suppress;
+
+/* Register a counter to suppress debugging grace-period delays. */
+void rcu_gp_slow_register(atomic_t *rgssp)
+{
+ WARN_ON_ONCE(rcu_gp_slow_suppress);
+
+ WRITE_ONCE(rcu_gp_slow_suppress, rgssp);
+}
+EXPORT_SYMBOL_GPL(rcu_gp_slow_register);
+
+/* Unregister a counter, with NULL for not caring which. */
+void rcu_gp_slow_unregister(atomic_t *rgssp)
+{
+ WARN_ON_ONCE(rgssp && rgssp != rcu_gp_slow_suppress);
+
+ WRITE_ONCE(rcu_gp_slow_suppress, NULL);
+}
+EXPORT_SYMBOL_GPL(rcu_gp_slow_unregister);
+
+static bool rcu_gp_slow_is_suppressed(void)
+{
+ atomic_t *rgssp = READ_ONCE(rcu_gp_slow_suppress);
+
+ return rgssp && atomic_read(rgssp);
+}
+
static void rcu_gp_slow(int delay)
{
- if (delay > 0 &&
- !(rcu_seq_ctr(rcu_state.gp_seq) %
- (rcu_num_nodes * PER_RCU_NODE_PERIOD * delay)))
- schedule_timeout_uninterruptible(delay);
+ if (!rcu_gp_slow_is_suppressed() && delay > 0 &&
+ !(rcu_seq_ctr(rcu_state.gp_seq) % (rcu_num_nodes * PER_RCU_NODE_PERIOD * delay)))
+ schedule_timeout_idle(delay);
+}
+
+static unsigned long sleep_duration;
+
+/* Allow rcutorture to stall the grace-period kthread. */
+void rcu_gp_set_torture_wait(int duration)
+{
+ if (IS_ENABLED(CONFIG_RCU_TORTURE_TEST) && duration > 0)
+ WRITE_ONCE(sleep_duration, duration);
+}
+EXPORT_SYMBOL_GPL(rcu_gp_set_torture_wait);
+
+/* Actually implement the aforementioned wait. */
+static void rcu_gp_torture_wait(void)
+{
+ unsigned long duration;
+
+ if (!IS_ENABLED(CONFIG_RCU_TORTURE_TEST))
+ return;
+ duration = xchg(&sleep_duration, 0UL);
+ if (duration > 0) {
+ pr_alert("%s: Waiting %lu jiffies\n", __func__, duration);
+ schedule_timeout_idle(duration);
+ pr_alert("%s: Wait complete\n", __func__);
+ }
+}
+
+/*
+ * Handler for on_each_cpu() to invoke the target CPU's RCU core
+ * processing.
+ */
+static void rcu_strict_gp_boundary(void *unused)
+{
+ invoke_rcu_core();
+}
+
+// Has rcu_init() been invoked? This is used (for example) to determine
+// whether spinlocks may be acquired safely.
+static bool rcu_init_invoked(void)
+{
+ return !!rcu_state.n_online_cpus;
+}
+
+// Make the polled API aware of the beginning of a grace period.
+static void rcu_poll_gp_seq_start(unsigned long *snap)
+{
+ struct rcu_node *rnp = rcu_get_root();
+
+ if (rcu_init_invoked())
+ raw_lockdep_assert_held_rcu_node(rnp);
+
+ // If RCU was idle, note beginning of GP.
+ if (!rcu_seq_state(rcu_state.gp_seq_polled))
+ rcu_seq_start(&rcu_state.gp_seq_polled);
+
+ // Either way, record current state.
+ *snap = rcu_state.gp_seq_polled;
+}
+
+// Make the polled API aware of the end of a grace period.
+static void rcu_poll_gp_seq_end(unsigned long *snap)
+{
+ struct rcu_node *rnp = rcu_get_root();
+
+ if (rcu_init_invoked())
+ raw_lockdep_assert_held_rcu_node(rnp);
+
+ // If the previously noted GP is still in effect, record the
+ // end of that GP. Either way, zero counter to avoid counter-wrap
+ // problems.
+ if (*snap && *snap == rcu_state.gp_seq_polled) {
+ rcu_seq_end(&rcu_state.gp_seq_polled);
+ rcu_state.gp_seq_polled_snap = 0;
+ rcu_state.gp_seq_polled_exp_snap = 0;
+ } else {
+ *snap = 0;
+ }
+}
+
+// Make the polled API aware of the beginning of a grace period, but
+// where caller does not hold the root rcu_node structure's lock.
+static void rcu_poll_gp_seq_start_unlocked(unsigned long *snap)
+{
+ unsigned long flags;
+ struct rcu_node *rnp = rcu_get_root();
+
+ if (rcu_init_invoked()) {
+ lockdep_assert_irqs_enabled();
+ raw_spin_lock_irqsave_rcu_node(rnp, flags);
+ }
+ rcu_poll_gp_seq_start(snap);
+ if (rcu_init_invoked())
+ raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
+}
+
+// Make the polled API aware of the end of a grace period, but where
+// caller does not hold the root rcu_node structure's lock.
+static void rcu_poll_gp_seq_end_unlocked(unsigned long *snap)
+{
+ unsigned long flags;
+ struct rcu_node *rnp = rcu_get_root();
+
+ if (rcu_init_invoked()) {
+ lockdep_assert_irqs_enabled();
+ raw_spin_lock_irqsave_rcu_node(rnp, flags);
+ }
+ rcu_poll_gp_seq_end(snap);
+ if (rcu_init_invoked())
+ raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
}
/*
* Initialize a new grace period. Return false if no grace period required.
*/
-static bool rcu_gp_init(void)
+static noinline_for_stack bool rcu_gp_init(void)
{
unsigned long flags;
unsigned long oldmask;
@@ -1489,24 +1464,32 @@ static bool rcu_gp_init(void)
record_gp_stall_check_time();
/* Record GP times before starting GP, hence rcu_seq_start(). */
rcu_seq_start(&rcu_state.gp_seq);
+ ASSERT_EXCLUSIVE_WRITER(rcu_state.gp_seq);
trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq, TPS("start"));
+ rcu_poll_gp_seq_start(&rcu_state.gp_seq_polled_snap);
raw_spin_unlock_irq_rcu_node(rnp);
/*
- * Apply per-leaf buffered online and offline operations to the
- * rcu_node tree. Note that this new grace period need not wait
- * for subsequent online CPUs, and that quiescent-state forcing
- * will handle subsequent offline CPUs.
+ * Apply per-leaf buffered online and offline operations to
+ * the rcu_node tree. Note that this new grace period need not
+ * wait for subsequent online CPUs, and that RCU hooks in the CPU
+ * offlining path, when combined with checks in this function,
+ * will handle CPUs that are currently going offline or that will
+ * go offline later. Please also refer to "Hotplug CPU" section
+ * of RCU's Requirements documentation.
*/
- rcu_state.gp_state = RCU_GP_ONOFF;
+ WRITE_ONCE(rcu_state.gp_state, RCU_GP_ONOFF);
+ /* Exclude CPU hotplug operations. */
rcu_for_each_leaf_node(rnp) {
- raw_spin_lock(&rcu_state.ofl_lock);
- raw_spin_lock_irq_rcu_node(rnp);
+ local_irq_save(flags);
+ arch_spin_lock(&rcu_state.ofl_lock);
+ raw_spin_lock_rcu_node(rnp);
if (rnp->qsmaskinit == rnp->qsmaskinitnext &&
!rnp->wait_blkd_tasks) {
/* Nothing to do on this leaf rcu_node structure. */
- raw_spin_unlock_irq_rcu_node(rnp);
- raw_spin_unlock(&rcu_state.ofl_lock);
+ raw_spin_unlock_rcu_node(rnp);
+ arch_spin_unlock(&rcu_state.ofl_lock);
+ local_irq_restore(flags);
continue;
}
@@ -1541,8 +1524,9 @@ static bool rcu_gp_init(void)
rcu_cleanup_dead_rnp(rnp);
}
- raw_spin_unlock_irq_rcu_node(rnp);
- raw_spin_unlock(&rcu_state.ofl_lock);
+ raw_spin_unlock_rcu_node(rnp);
+ arch_spin_unlock(&rcu_state.ofl_lock);
+ local_irq_restore(flags);
}
rcu_gp_slow(gp_preinit_delay); /* Races with CPU hotplug. */
@@ -1558,7 +1542,7 @@ static bool rcu_gp_init(void)
* The grace period cannot complete until the initialization
* process finishes, because this kthread handles both.
*/
- rcu_state.gp_state = RCU_GP_INIT;
+ WRITE_ONCE(rcu_state.gp_state, RCU_GP_INIT);
rcu_for_each_node_breadth_first(rnp) {
rcu_gp_slow(gp_init_delay);
raw_spin_lock_irqsave_rcu_node(rnp, flags);
@@ -1583,6 +1567,10 @@ static bool rcu_gp_init(void)
WRITE_ONCE(rcu_state.gp_activity, jiffies);
}
+ // If strict, make all CPUs aware of new grace period.
+ if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD))
+ on_each_cpu(rcu_strict_gp_boundary, NULL, 0);
+
return true;
}
@@ -1594,12 +1582,16 @@ static bool rcu_gp_fqs_check_wake(int *gfp)
{
struct rcu_node *rnp = rcu_get_root();
- /* Someone like call_rcu() requested a force-quiescent-state scan. */
+ // If under overload conditions, force an immediate FQS scan.
+ if (*gfp & RCU_GP_FLAG_OVLD)
+ return true;
+
+ // Someone like call_rcu() requested a force-quiescent-state scan.
*gfp = READ_ONCE(rcu_state.gp_flags);
if (*gfp & RCU_GP_FLAG_FQS)
return true;
- /* The current grace period has completed. */
+ // The current grace period has completed.
if (!READ_ONCE(rnp->qsmask) && !rcu_preempt_blocked_readers_cgp(rnp))
return true;
@@ -1614,7 +1606,7 @@ static void rcu_gp_fqs(bool first_time)
struct rcu_node *rnp = rcu_get_root();
WRITE_ONCE(rcu_state.gp_activity, jiffies);
- rcu_state.n_force_qs++;
+ WRITE_ONCE(rcu_state.n_force_qs, rcu_state.n_force_qs + 1);
if (first_time) {
/* Collect dyntick-idle snapshots. */
force_qs_rnp(dyntick_save_progress_counter);
@@ -1634,45 +1626,66 @@ static void rcu_gp_fqs(bool first_time)
/*
* Loop doing repeated quiescent-state forcing until the grace period ends.
*/
-static void rcu_gp_fqs_loop(void)
+static noinline_for_stack void rcu_gp_fqs_loop(void)
{
- bool first_gp_fqs;
- int gf;
+ bool first_gp_fqs = true;
+ int gf = 0;
unsigned long j;
int ret;
struct rcu_node *rnp = rcu_get_root();
- first_gp_fqs = true;
j = READ_ONCE(jiffies_till_first_fqs);
+ if (rcu_state.cbovld)
+ gf = RCU_GP_FLAG_OVLD;
ret = 0;
for (;;) {
- if (!ret) {
- rcu_state.jiffies_force_qs = jiffies + j;
+ if (rcu_state.cbovld) {
+ j = (j + 2) / 3;
+ if (j <= 0)
+ j = 1;
+ }
+ if (!ret || time_before(jiffies + j, rcu_state.jiffies_force_qs)) {
+ WRITE_ONCE(rcu_state.jiffies_force_qs, jiffies + j);
+ /*
+ * jiffies_force_qs before RCU_GP_WAIT_FQS state
+ * update; required for stall checks.
+ */
+ smp_wmb();
WRITE_ONCE(rcu_state.jiffies_kick_kthreads,
jiffies + (j ? 3 * j : 2));
}
- trace_rcu_grace_period(rcu_state.name,
- READ_ONCE(rcu_state.gp_seq),
+ trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq,
TPS("fqswait"));
- rcu_state.gp_state = RCU_GP_WAIT_FQS;
- ret = swait_event_idle_timeout_exclusive(
- rcu_state.gp_wq, rcu_gp_fqs_check_wake(&gf), j);
- rcu_state.gp_state = RCU_GP_DOING_FQS;
+ WRITE_ONCE(rcu_state.gp_state, RCU_GP_WAIT_FQS);
+ (void)swait_event_idle_timeout_exclusive(rcu_state.gp_wq,
+ rcu_gp_fqs_check_wake(&gf), j);
+ rcu_gp_torture_wait();
+ WRITE_ONCE(rcu_state.gp_state, RCU_GP_DOING_FQS);
/* Locking provides needed memory barriers. */
- /* If grace period done, leave loop. */
+ /*
+ * Exit the loop if the root rcu_node structure indicates that the grace period
+ * has ended, leave the loop. The rcu_preempt_blocked_readers_cgp(rnp) check
+ * is required only for single-node rcu_node trees because readers blocking
+ * the current grace period are queued only on leaf rcu_node structures.
+ * For multi-node trees, checking the root node's ->qsmask suffices, because a
+ * given root node's ->qsmask bit is cleared only when all CPUs and tasks from
+ * the corresponding leaf nodes have passed through their quiescent state.
+ */
if (!READ_ONCE(rnp->qsmask) &&
!rcu_preempt_blocked_readers_cgp(rnp))
break;
/* If time for quiescent-state forcing, do it. */
- if (ULONG_CMP_GE(jiffies, rcu_state.jiffies_force_qs) ||
- (gf & RCU_GP_FLAG_FQS)) {
- trace_rcu_grace_period(rcu_state.name,
- READ_ONCE(rcu_state.gp_seq),
+ if (!time_after(rcu_state.jiffies_force_qs, jiffies) ||
+ (gf & (RCU_GP_FLAG_FQS | RCU_GP_FLAG_OVLD))) {
+ trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq,
TPS("fqsstart"));
rcu_gp_fqs(first_gp_fqs);
- first_gp_fqs = false;
- trace_rcu_grace_period(rcu_state.name,
- READ_ONCE(rcu_state.gp_seq),
+ gf = 0;
+ if (first_gp_fqs) {
+ first_gp_fqs = false;
+ gf = rcu_state.cbovld ? RCU_GP_FLAG_OVLD : 0;
+ }
+ trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq,
TPS("fqsend"));
cond_resched_tasks_rcu_qs();
WRITE_ONCE(rcu_state.gp_activity, jiffies);
@@ -1683,8 +1696,7 @@ static void rcu_gp_fqs_loop(void)
cond_resched_tasks_rcu_qs();
WRITE_ONCE(rcu_state.gp_activity, jiffies);
WARN_ON(signal_pending(current));
- trace_rcu_grace_period(rcu_state.name,
- READ_ONCE(rcu_state.gp_seq),
+ trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq,
TPS("fqswaitsig"));
ret = 1; /* Keep old FQS timing. */
j = jiffies;
@@ -1692,6 +1704,7 @@ static void rcu_gp_fqs_loop(void)
j = 1;
else
j = rcu_state.jiffies_force_qs - j;
+ gf = 0;
}
}
}
@@ -1699,10 +1712,11 @@ static void rcu_gp_fqs_loop(void)
/*
* Clean up after the old grace period.
*/
-static void rcu_gp_cleanup(void)
+static noinline void rcu_gp_cleanup(void)
{
- unsigned long gp_duration;
+ int cpu;
bool needgp = false;
+ unsigned long gp_duration;
unsigned long new_gp_seq;
bool offloaded;
struct rcu_data *rdp;
@@ -1724,6 +1738,7 @@ static void rcu_gp_cleanup(void)
* safe for us to drop the lock in order to mark the grace
* period as completed in all of the rcu_node structures.
*/
+ rcu_poll_gp_seq_end(&rcu_state.gp_seq_polled_snap);
raw_spin_unlock_irq_rcu_node(rnp);
/*
@@ -1743,11 +1758,19 @@ static void rcu_gp_cleanup(void)
dump_blkd_tasks(rnp, 10);
WARN_ON_ONCE(rnp->qsmask);
WRITE_ONCE(rnp->gp_seq, new_gp_seq);
+ if (!rnp->parent)
+ smp_mb(); // Order against failing poll_state_synchronize_rcu_full().
rdp = this_cpu_ptr(&rcu_data);
if (rnp == rdp->mynode)
needgp = __note_gp_changes(rnp, rdp) || needgp;
/* smp_mb() provided by prior unlock-lock pair. */
needgp = rcu_future_gp_cleanup(rnp) || needgp;
+ // Reset overload indication for CPUs no longer overloaded
+ if (rcu_is_leaf_node(rnp))
+ for_each_leaf_node_cpu_mask(rnp, cpu, rnp->cbovldmask) {
+ rdp = per_cpu_ptr(&rcu_data, cpu);
+ check_cb_ovld_locked(rdp, rnp);
+ }
sq = rcu_nocb_gp_get(rnp);
raw_spin_unlock_irq_rcu_node(rnp);
rcu_nocb_gp_cleanup(sq);
@@ -1761,7 +1784,8 @@ static void rcu_gp_cleanup(void)
/* Declare grace period done, trace first to use old GP number. */
trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq, TPS("end"));
rcu_seq_end(&rcu_state.gp_seq);
- rcu_state.gp_state = RCU_GP_IDLE;
+ ASSERT_EXCLUSIVE_WRITER(rcu_state.gp_seq);
+ WRITE_ONCE(rcu_state.gp_state, RCU_GP_IDLE);
/* Check for GP requests since above loop. */
rdp = this_cpu_ptr(&rcu_data);
if (!needgp && ULONG_CMP_LT(rnp->gp_seq, rnp->gp_seq_needed)) {
@@ -1770,19 +1794,37 @@ static void rcu_gp_cleanup(void)
needgp = true;
}
/* Advance CBs to reduce false positives below. */
- offloaded = IS_ENABLED(CONFIG_RCU_NOCB_CPU) &&
- rcu_segcblist_is_offloaded(&rdp->cblist);
+ offloaded = rcu_rdp_is_offloaded(rdp);
if ((offloaded || !rcu_accelerate_cbs(rnp, rdp)) && needgp) {
+
+ // We get here if a grace period was needed (“needgp”)
+ // and the above call to rcu_accelerate_cbs() did not set
+ // the RCU_GP_FLAG_INIT bit in ->gp_state (which records
+ // the need for another grace period).  The purpose
+ // of the “offloaded” check is to avoid invoking
+ // rcu_accelerate_cbs() on an offloaded CPU because we do not
+ // hold the ->nocb_lock needed to safely access an offloaded
+ // ->cblist.  We do not want to acquire that lock because
+ // it can be heavily contended during callback floods.
+
WRITE_ONCE(rcu_state.gp_flags, RCU_GP_FLAG_INIT);
- rcu_state.gp_req_activity = jiffies;
- trace_rcu_grace_period(rcu_state.name,
- READ_ONCE(rcu_state.gp_seq),
- TPS("newreq"));
+ WRITE_ONCE(rcu_state.gp_req_activity, jiffies);
+ trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq, TPS("newreq"));
} else {
- WRITE_ONCE(rcu_state.gp_flags,
- rcu_state.gp_flags & RCU_GP_FLAG_INIT);
+
+ // We get here either if there is no need for an
+ // additional grace period or if rcu_accelerate_cbs() has
+ // already set the RCU_GP_FLAG_INIT bit in ->gp_flags. 
+ // So all we need to do is to clear all of the other
+ // ->gp_flags bits.
+
+ WRITE_ONCE(rcu_state.gp_flags, rcu_state.gp_flags & RCU_GP_FLAG_INIT);
}
raw_spin_unlock_irq_rcu_node(rnp);
+
+ // If strict, make all CPUs aware of the end of the old grace period.
+ if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD))
+ on_each_cpu(rcu_strict_gp_boundary, NULL, 0);
}
/*
@@ -1795,22 +1837,21 @@ static int __noreturn rcu_gp_kthread(void *unused)
/* Handle grace-period start. */
for (;;) {
- trace_rcu_grace_period(rcu_state.name,
- READ_ONCE(rcu_state.gp_seq),
+ trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq,
TPS("reqwait"));
- rcu_state.gp_state = RCU_GP_WAIT_GPS;
+ WRITE_ONCE(rcu_state.gp_state, RCU_GP_WAIT_GPS);
swait_event_idle_exclusive(rcu_state.gp_wq,
READ_ONCE(rcu_state.gp_flags) &
RCU_GP_FLAG_INIT);
- rcu_state.gp_state = RCU_GP_DONE_GPS;
+ rcu_gp_torture_wait();
+ WRITE_ONCE(rcu_state.gp_state, RCU_GP_DONE_GPS);
/* Locking provides needed memory barrier. */
if (rcu_gp_init())
break;
cond_resched_tasks_rcu_qs();
WRITE_ONCE(rcu_state.gp_activity, jiffies);
WARN_ON(signal_pending(current));
- trace_rcu_grace_period(rcu_state.name,
- READ_ONCE(rcu_state.gp_seq),
+ trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq,
TPS("reqwaitsig"));
}
@@ -1818,9 +1859,9 @@ static int __noreturn rcu_gp_kthread(void *unused)
rcu_gp_fqs_loop();
/* Handle grace-period end. */
- rcu_state.gp_state = RCU_GP_CLEANUP;
+ WRITE_ONCE(rcu_state.gp_state, RCU_GP_CLEANUP);
rcu_gp_cleanup();
- rcu_state.gp_state = RCU_GP_CLEANED;
+ WRITE_ONCE(rcu_state.gp_state, RCU_GP_CLEANED);
}
}
@@ -1881,7 +1922,7 @@ static void rcu_report_qs_rnp(unsigned long mask, struct rcu_node *rnp,
WARN_ON_ONCE(oldmask); /* Any child must be all zeroed! */
WARN_ON_ONCE(!rcu_is_leaf_node(rnp) &&
rcu_preempt_blocked_readers_cgp(rnp));
- rnp->qsmask &= ~mask;
+ WRITE_ONCE(rnp->qsmask, rnp->qsmask & ~mask);
trace_rcu_quiescent_state_report(rcu_state.name, rnp->gp_seq,
mask, rnp->qsmask, rnp->level,
rnp->grplo, rnp->grphi,
@@ -1904,7 +1945,7 @@ static void rcu_report_qs_rnp(unsigned long mask, struct rcu_node *rnp,
rnp_c = rnp;
rnp = rnp->parent;
raw_spin_lock_irqsave_rcu_node(rnp, flags);
- oldmask = rnp_c->qsmask;
+ oldmask = READ_ONCE(rnp_c->qsmask);
}
/*
@@ -1962,15 +2003,15 @@ rcu_report_unblock_qs_rnp(struct rcu_node *rnp, unsigned long flags)
* structure. This must be called from the specified CPU.
*/
static void
-rcu_report_qs_rdp(int cpu, struct rcu_data *rdp)
+rcu_report_qs_rdp(struct rcu_data *rdp)
{
unsigned long flags;
unsigned long mask;
bool needwake = false;
- const bool offloaded = IS_ENABLED(CONFIG_RCU_NOCB_CPU) &&
- rcu_segcblist_is_offloaded(&rdp->cblist);
+ bool needacc = false;
struct rcu_node *rnp;
+ WARN_ON_ONCE(rdp->cpu != smp_processor_id());
rnp = rdp->mynode;
raw_spin_lock_irqsave_rcu_node(rnp, flags);
if (rdp->cpu_no_qs.b.norm || rdp->gp_seq != rnp->gp_seq ||
@@ -1987,21 +2028,37 @@ rcu_report_qs_rdp(int cpu, struct rcu_data *rdp)
return;
}
mask = rdp->grpmask;
+ rdp->core_needs_qs = false;
if ((rnp->qsmask & mask) == 0) {
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
} else {
/*
* This GP can't end until cpu checks in, so all of our
* callbacks can be processed during the next GP.
+ *
+ * NOCB kthreads have their own way to deal with that...
*/
- if (!offloaded)
+ if (!rcu_rdp_is_offloaded(rdp)) {
needwake = rcu_accelerate_cbs(rnp, rdp);
+ } else if (!rcu_segcblist_completely_offloaded(&rdp->cblist)) {
+ /*
+ * ...but NOCB kthreads may miss or delay callbacks acceleration
+ * if in the middle of a (de-)offloading process.
+ */
+ needacc = true;
+ }
rcu_disable_urgency_upon_qs(rdp);
rcu_report_qs_rnp(mask, rnp, rnp->gp_seq, flags);
/* ^^^ Released rnp->lock */
if (needwake)
rcu_gp_kthread_wake();
+
+ if (needacc) {
+ rcu_nocb_lock_irqsave(rdp, flags);
+ rcu_accelerate_cbs_unlocked(rnp, rdp);
+ rcu_nocb_unlock_irqrestore(rdp, flags);
+ }
}
}
@@ -2035,7 +2092,7 @@ rcu_check_quiescent_state(struct rcu_data *rdp)
* Tell RCU we are done (but rcu_report_qs_rdp() will be the
* judge of that).
*/
- rcu_report_qs_rdp(rdp->cpu, rdp);
+ rcu_report_qs_rdp(rdp);
}
/*
@@ -2045,15 +2102,15 @@ rcu_check_quiescent_state(struct rcu_data *rdp)
int rcutree_dying_cpu(unsigned int cpu)
{
bool blkd;
- struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
+ struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
struct rcu_node *rnp = rdp->mynode;
if (!IS_ENABLED(CONFIG_HOTPLUG_CPU))
return 0;
blkd = !!(rnp->qsmask & rdp->grpmask);
- trace_rcu_grace_period(rcu_state.name, rnp->gp_seq,
- blkd ? TPS("cpuofl") : TPS("cpuofl-bgp"));
+ trace_rcu_grace_period(rcu_state.name, READ_ONCE(rnp->gp_seq),
+ blkd ? TPS("cpuofl-bgp") : TPS("cpuofl"));
return 0;
}
@@ -2116,11 +2173,9 @@ int rcutree_dead_cpu(unsigned int cpu)
if (!IS_ENABLED(CONFIG_HOTPLUG_CPU))
return 0;
+ WRITE_ONCE(rcu_state.n_online_cpus, rcu_state.n_online_cpus - 1);
/* Adjust any no-longer-needed kthreads. */
rcu_boost_kthread_setaffinity(rnp, -1);
- /* Do any needed no-CB deferred wakeups from this CPU. */
- do_nocb_deferred_wakeup(per_cpu_ptr(&rcu_data, cpu));
-
// Stop-machine done, so allow nohz_full to disable tick.
tick_dep_clear(TICK_DEP_BIT_RCU);
return 0;
@@ -2128,16 +2183,16 @@ int rcutree_dead_cpu(unsigned int cpu)
/*
* Invoke any RCU callbacks that have made it to the end of their grace
- * period. Thottle as specified by rdp->blimit.
+ * period. Throttle as specified by rdp->blimit.
*/
static void rcu_do_batch(struct rcu_data *rdp)
{
+ int div;
+ bool __maybe_unused empty;
unsigned long flags;
- const bool offloaded = IS_ENABLED(CONFIG_RCU_NOCB_CPU) &&
- rcu_segcblist_is_offloaded(&rdp->cblist);
struct rcu_head *rhp;
struct rcu_cblist rcl = RCU_CBLIST_INITIALIZER(rcl);
- long bl, count;
+ long bl, count = 0;
long pending, tlimit = 0;
/* If no callbacks are ready, just return. */
@@ -2147,35 +2202,44 @@ static void rcu_do_batch(struct rcu_data *rdp)
trace_rcu_batch_end(rcu_state.name, 0,
!rcu_segcblist_empty(&rdp->cblist),
need_resched(), is_idle_task(current),
- rcu_is_callbacks_kthread());
+ rcu_is_callbacks_kthread(rdp));
return;
}
/*
- * Extract the list of ready callbacks, disabling to prevent
+ * Extract the list of ready callbacks, disabling IRQs to prevent
* races with call_rcu() from interrupt handlers. Leave the
* callback counts, as rcu_barrier() needs to be conservative.
*/
- local_irq_save(flags);
- rcu_nocb_lock(rdp);
+ rcu_nocb_lock_irqsave(rdp, flags);
WARN_ON_ONCE(cpu_is_offline(smp_processor_id()));
pending = rcu_segcblist_n_cbs(&rdp->cblist);
- bl = max(rdp->blimit, pending >> rcu_divisor);
- if (unlikely(bl > 100))
- tlimit = local_clock() + rcu_resched_ns;
+ div = READ_ONCE(rcu_divisor);
+ div = div < 0 ? 7 : div > sizeof(long) * 8 - 2 ? sizeof(long) * 8 - 2 : div;
+ bl = max(rdp->blimit, pending >> div);
+ if (in_serving_softirq() && unlikely(bl > 100)) {
+ long rrn = READ_ONCE(rcu_resched_ns);
+
+ rrn = rrn < NSEC_PER_MSEC ? NSEC_PER_MSEC : rrn > NSEC_PER_SEC ? NSEC_PER_SEC : rrn;
+ tlimit = local_clock() + rrn;
+ }
trace_rcu_batch_start(rcu_state.name,
rcu_segcblist_n_cbs(&rdp->cblist), bl);
rcu_segcblist_extract_done_cbs(&rdp->cblist, &rcl);
- if (offloaded)
+ if (rcu_rdp_is_offloaded(rdp))
rdp->qlen_last_fqs_check = rcu_segcblist_n_cbs(&rdp->cblist);
+
+ trace_rcu_segcb_stats(&rdp->cblist, TPS("SegCbDequeued"));
rcu_nocb_unlock_irqrestore(rdp, flags);
/* Invoke callbacks. */
tick_dep_set_task(current, TICK_DEP_BIT_RCU);
rhp = rcu_cblist_dequeue(&rcl);
+
for (; rhp; rhp = rcu_cblist_dequeue(&rcl)) {
rcu_callback_t f;
+ count++;
debug_rcu_head_unqueue(rhp);
rcu_lock_acquire(&rcu_callback_map);
@@ -2189,21 +2253,22 @@ static void rcu_do_batch(struct rcu_data *rdp)
/*
* Stop only if limit reached and CPU has something to do.
- * Note: The rcl structure counts down from zero.
*/
- if (-rcl.len >= bl && !offloaded &&
- (need_resched() ||
- (!is_idle_task(current) && !rcu_is_callbacks_kthread())))
- break;
- if (unlikely(tlimit)) {
- /* only call local_clock() every 32 callbacks */
- if (likely((-rcl.len & 31) || local_clock() < tlimit))
- continue;
- /* Exceeded the time limit, so leave. */
- break;
- }
- if (offloaded) {
- WARN_ON_ONCE(in_serving_softirq());
+ if (in_serving_softirq()) {
+ if (count >= bl && (need_resched() || !is_idle_task(current)))
+ break;
+ /*
+ * Make sure we don't spend too much time here and deprive other
+ * softirq vectors of CPU cycles.
+ */
+ if (unlikely(tlimit)) {
+ /* only call local_clock() every 32 callbacks */
+ if (likely((count & 31) || local_clock() < tlimit))
+ continue;
+ /* Exceeded the time limit, so leave. */
+ break;
+ }
+ } else {
local_bh_enable();
lockdep_assert_irqs_enabled();
cond_resched_tasks_rcu_qs();
@@ -2212,16 +2277,14 @@ static void rcu_do_batch(struct rcu_data *rdp)
}
}
- local_irq_save(flags);
- rcu_nocb_lock(rdp);
- count = -rcl.len;
+ rcu_nocb_lock_irqsave(rdp, flags);
+ rdp->n_cbs_invoked += count;
trace_rcu_batch_end(rcu_state.name, count, !!rcl.head, need_resched(),
- is_idle_task(current), rcu_is_callbacks_kthread());
+ is_idle_task(current), rcu_is_callbacks_kthread(rdp));
/* Update counts and requeue any remaining callbacks. */
rcu_segcblist_insert_done_cbs(&rdp->cblist, &rcl);
- smp_mb(); /* List handling before counting for rcu_barrier(). */
- rcu_segcblist_insert_count(&rdp->cblist, &rcl);
+ rcu_segcblist_add_len(&rdp->cblist, -count);
/* Reinstate batch limit if we have worked down the excess. */
count = rcu_segcblist_n_cbs(&rdp->cblist);
@@ -2231,7 +2294,7 @@ static void rcu_do_batch(struct rcu_data *rdp)
/* Reset ->qlen_last_fqs_check trigger if enough CBs have drained. */
if (count == 0 && rdp->qlen_last_fqs_check != 0) {
rdp->qlen_last_fqs_check = 0;
- rdp->n_force_qs_snap = rcu_state.n_force_qs;
+ rdp->n_force_qs_snap = READ_ONCE(rcu_state.n_force_qs);
} else if (count < rdp->qlen_last_fqs_check - qhimark)
rdp->qlen_last_fqs_check = count;
@@ -2239,15 +2302,15 @@ static void rcu_do_batch(struct rcu_data *rdp)
* The following usually indicates a double call_rcu(). To track
* this down, try building with CONFIG_DEBUG_OBJECTS_RCU_HEAD=y.
*/
- WARN_ON_ONCE(count == 0 && !rcu_segcblist_empty(&rdp->cblist));
+ empty = rcu_segcblist_empty(&rdp->cblist);
+ WARN_ON_ONCE(count == 0 && !empty);
WARN_ON_ONCE(!IS_ENABLED(CONFIG_RCU_NOCB_CPU) &&
- count != 0 && rcu_segcblist_empty(&rdp->cblist));
+ count != 0 && empty);
+ WARN_ON_ONCE(count == 0 && rcu_segcblist_n_segment_cbs(&rdp->cblist) != 0);
+ WARN_ON_ONCE(!empty && rcu_segcblist_n_segment_cbs(&rdp->cblist) == 0);
rcu_nocb_unlock_irqrestore(rdp, flags);
- /* Re-invoke RCU core processing if there are callbacks remaining. */
- if (!offloaded && rcu_segcblist_ready_cbs(&rdp->cblist))
- invoke_rcu_core();
tick_dep_clear_task(current, TICK_DEP_BIT_RCU);
}
@@ -2257,11 +2320,19 @@ static void rcu_do_batch(struct rcu_data *rdp)
* state, for example, user mode or idle loop. It also schedules RCU
* core processing. If the current grace period has gone on too long,
* it will ask the scheduler to manufacture a context switch for the sole
- * purpose of providing a providing the needed quiescent state.
+ * purpose of providing the needed quiescent state.
*/
void rcu_sched_clock_irq(int user)
{
+ unsigned long j;
+
+ if (IS_ENABLED(CONFIG_PROVE_RCU)) {
+ j = jiffies;
+ WARN_ON_ONCE(time_before(j, __this_cpu_read(rcu_data.last_sched_clock)));
+ __this_cpu_write(rcu_data.last_sched_clock, j);
+ }
trace_rcu_utilization(TPS("Start scheduler-tick"));
+ lockdep_assert_irqs_disabled();
raw_cpu_inc(rcu_data.ticks_this_gp);
/* The load-acquire pairs with the store-release setting to true. */
if (smp_load_acquire(this_cpu_ptr(&rcu_data.rcu_urgent_qs))) {
@@ -2275,6 +2346,9 @@ void rcu_sched_clock_irq(int user)
rcu_flavor_sched_clock_irq(user);
if (rcu_pending(user))
invoke_rcu_core();
+ if (user || rcu_is_cpu_rrupt_from_idle())
+ rcu_note_voluntary_context_switch(current);
+ lockdep_assert_irqs_disabled();
trace_rcu_utilization(TPS("End scheduler-tick"));
}
@@ -2294,13 +2368,15 @@ static void force_qs_rnp(int (*f)(struct rcu_data *rdp))
struct rcu_data *rdp;
struct rcu_node *rnp;
+ rcu_state.cbovld = rcu_state.cbovldnext;
+ rcu_state.cbovldnext = false;
rcu_for_each_leaf_node(rnp) {
cond_resched_tasks_rcu_qs();
mask = 0;
raw_spin_lock_irqsave_rcu_node(rnp, flags);
+ rcu_state.cbovldnext |= !!rnp->cbovldmask;
if (rnp->qsmask == 0) {
- if (!IS_ENABLED(CONFIG_PREEMPT_RCU) ||
- rcu_preempt_blocked_readers_cgp(rnp)) {
+ if (rcu_preempt_blocked_readers_cgp(rnp)) {
/*
* No point in scanning bits because they
* are all zero. But we might need to
@@ -2368,14 +2444,38 @@ void rcu_force_quiescent_state(void)
}
EXPORT_SYMBOL_GPL(rcu_force_quiescent_state);
+// Workqueue handler for an RCU reader for kernels enforcing struct RCU
+// grace periods.
+static void strict_work_handler(struct work_struct *work)
+{
+ rcu_read_lock();
+ rcu_read_unlock();
+}
+
/* Perform RCU core processing work for the current CPU. */
static __latent_entropy void rcu_core(void)
{
unsigned long flags;
struct rcu_data *rdp = raw_cpu_ptr(&rcu_data);
struct rcu_node *rnp = rdp->mynode;
- const bool offloaded = IS_ENABLED(CONFIG_RCU_NOCB_CPU) &&
- rcu_segcblist_is_offloaded(&rdp->cblist);
+ /*
+ * On RT rcu_core() can be preempted when IRQs aren't disabled.
+ * Therefore this function can race with concurrent NOCB (de-)offloading
+ * on this CPU and the below condition must be considered volatile.
+ * However if we race with:
+ *
+ * _ Offloading: In the worst case we accelerate or process callbacks
+ * concurrently with NOCB kthreads. We are guaranteed to
+ * call rcu_nocb_lock() if that happens.
+ *
+ * _ Deoffloading: In the worst case we miss callbacks acceleration or
+ * processing. This is fine because the early stage
+ * of deoffloading invokes rcu_core() after setting
+ * SEGCBLIST_RCU_CORE. So we guarantee that we'll process
+ * what could have been dismissed without the need to wait
+ * for the next rcu_pending() check in the next jiffy.
+ */
+ const bool do_batch = !rcu_segcblist_completely_offloaded(&rdp->cblist);
if (cpu_is_offline(smp_processor_id()))
return;
@@ -2383,7 +2483,7 @@ static __latent_entropy void rcu_core(void)
WARN_ON_ONCE(!rdp->beenonline);
/* Report any deferred quiescent states if preemption enabled. */
- if (!(preempt_count() & PREEMPT_MASK)) {
+ if (IS_ENABLED(CONFIG_PREEMPT_COUNT) && (!(preempt_count() & PREEMPT_MASK))) {
rcu_preempt_deferred_qs(current);
} else if (rcu_preempt_need_deferred_qs(current)) {
set_tsk_need_resched(current);
@@ -2395,23 +2495,31 @@ static __latent_entropy void rcu_core(void)
/* No grace period and unregistered callbacks? */
if (!rcu_gp_in_progress() &&
- rcu_segcblist_is_enabled(&rdp->cblist) && !offloaded) {
- local_irq_save(flags);
+ rcu_segcblist_is_enabled(&rdp->cblist) && do_batch) {
+ rcu_nocb_lock_irqsave(rdp, flags);
if (!rcu_segcblist_restempty(&rdp->cblist, RCU_NEXT_READY_TAIL))
rcu_accelerate_cbs_unlocked(rnp, rdp);
- local_irq_restore(flags);
+ rcu_nocb_unlock_irqrestore(rdp, flags);
}
rcu_check_gp_start_stall(rnp, rdp, rcu_jiffies_till_stall_check());
/* If there are callbacks ready, invoke them. */
- if (!offloaded && rcu_segcblist_ready_cbs(&rdp->cblist) &&
- likely(READ_ONCE(rcu_scheduler_fully_active)))
+ if (do_batch && rcu_segcblist_ready_cbs(&rdp->cblist) &&
+ likely(READ_ONCE(rcu_scheduler_fully_active))) {
rcu_do_batch(rdp);
+ /* Re-invoke RCU core processing if there are callbacks remaining. */
+ if (rcu_segcblist_ready_cbs(&rdp->cblist))
+ invoke_rcu_core();
+ }
/* Do any needed deferred wakeups of rcuo kthreads. */
do_nocb_deferred_wakeup(rdp);
trace_rcu_utilization(TPS("End RCU core"));
+
+ // If strict GPs, schedule an RCU reader in a clean environment.
+ if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD))
+ queue_work_on(rdp->cpu, rcu_gp_wq, &rdp->strict_work);
}
static void rcu_core_si(struct softirq_action *h)
@@ -2474,10 +2582,12 @@ static void rcu_cpu_kthread(unsigned int cpu)
{
unsigned int *statusp = this_cpu_ptr(&rcu_data.rcu_cpu_kthread_status);
char work, *workp = this_cpu_ptr(&rcu_data.rcu_cpu_has_work);
+ unsigned long *j = this_cpu_ptr(&rcu_data.rcuc_activity);
int spincnt;
trace_rcu_utilization(TPS("Start CPU kthread@rcu_run"));
for (spincnt = 0; spincnt < 10; spincnt++) {
+ WRITE_ONCE(*j, jiffies);
local_bh_disable();
*statusp = RCU_KTHREAD_RUNNING;
local_irq_disable();
@@ -2495,9 +2605,10 @@ static void rcu_cpu_kthread(unsigned int cpu)
}
*statusp = RCU_KTHREAD_YIELDING;
trace_rcu_utilization(TPS("Start CPU kthread@rcu_yield"));
- schedule_timeout_interruptible(2);
+ schedule_timeout_idle(2);
trace_rcu_utilization(TPS("End CPU kthread@rcu_yield"));
*statusp = RCU_KTHREAD_WAITING;
+ WRITE_ONCE(*j, jiffies);
}
static struct smp_hotplug_thread rcu_cpu_thread_spec = {
@@ -2518,13 +2629,12 @@ static int __init rcu_spawn_core_kthreads(void)
for_each_possible_cpu(cpu)
per_cpu(rcu_data.rcu_cpu_has_work, cpu) = 0;
- if (!IS_ENABLED(CONFIG_RCU_BOOST) && use_softirq)
+ if (use_softirq)
return 0;
WARN_ONCE(smpboot_register_percpu_thread(&rcu_cpu_thread_spec),
"%s: Could not start rcuc kthread, OOM is now expected behavior\n", __func__);
return 0;
}
-early_initcall(rcu_spawn_core_kthreads);
/*
* Handle any core-RCU processing required by a call_rcu() invocation.
@@ -2562,10 +2672,10 @@ static void __call_rcu_core(struct rcu_data *rdp, struct rcu_head *head,
} else {
/* Give the grace period a kick. */
rdp->blimit = DEFAULT_MAX_RCU_BLIMIT;
- if (rcu_state.n_force_qs == rdp->n_force_qs_snap &&
+ if (READ_ONCE(rcu_state.n_force_qs) == rdp->n_force_qs_snap &&
rcu_segcblist_first_pend_cb(&rdp->cblist) != head)
rcu_force_quiescent_state();
- rdp->n_force_qs_snap = rcu_state.n_force_qs;
+ rdp->n_force_qs_snap = READ_ONCE(rcu_state.n_force_qs);
rdp->qlen_last_fqs_check = rcu_segcblist_n_cbs(&rdp->cblist);
}
}
@@ -2579,14 +2689,90 @@ static void rcu_leak_callback(struct rcu_head *rhp)
}
/*
- * Helper function for call_rcu() and friends. The cpu argument will
- * normally be -1, indicating "currently running CPU". It may specify
- * a CPU only if that CPU is a no-CBs CPU. Currently, only rcu_barrier()
- * is expected to specify a CPU.
+ * Check and if necessary update the leaf rcu_node structure's
+ * ->cbovldmask bit corresponding to the current CPU based on that CPU's
+ * number of queued RCU callbacks. The caller must hold the leaf rcu_node
+ * structure's ->lock.
*/
-static void
-__call_rcu(struct rcu_head *head, rcu_callback_t func)
+static void check_cb_ovld_locked(struct rcu_data *rdp, struct rcu_node *rnp)
{
+ raw_lockdep_assert_held_rcu_node(rnp);
+ if (qovld_calc <= 0)
+ return; // Early boot and wildcard value set.
+ if (rcu_segcblist_n_cbs(&rdp->cblist) >= qovld_calc)
+ WRITE_ONCE(rnp->cbovldmask, rnp->cbovldmask | rdp->grpmask);
+ else
+ WRITE_ONCE(rnp->cbovldmask, rnp->cbovldmask & ~rdp->grpmask);
+}
+
+/*
+ * Check and if necessary update the leaf rcu_node structure's
+ * ->cbovldmask bit corresponding to the current CPU based on that CPU's
+ * number of queued RCU callbacks. No locks need be held, but the
+ * caller must have disabled interrupts.
+ *
+ * Note that this function ignores the possibility that there are a lot
+ * of callbacks all of which have already seen the end of their respective
+ * grace periods. This omission is due to the need for no-CBs CPUs to
+ * be holding ->nocb_lock to do this check, which is too heavy for a
+ * common-case operation.
+ */
+static void check_cb_ovld(struct rcu_data *rdp)
+{
+ struct rcu_node *const rnp = rdp->mynode;
+
+ if (qovld_calc <= 0 ||
+ ((rcu_segcblist_n_cbs(&rdp->cblist) >= qovld_calc) ==
+ !!(READ_ONCE(rnp->cbovldmask) & rdp->grpmask)))
+ return; // Early boot wildcard value or already set correctly.
+ raw_spin_lock_rcu_node(rnp);
+ check_cb_ovld_locked(rdp, rnp);
+ raw_spin_unlock_rcu_node(rnp);
+}
+
+/**
+ * call_rcu() - Queue an RCU callback for invocation after a grace period.
+ * @head: structure to be used for queueing the RCU updates.
+ * @func: actual callback function to be invoked after the grace period
+ *
+ * The callback function will be invoked some time after a full grace
+ * period elapses, in other words after all pre-existing RCU read-side
+ * critical sections have completed. However, the callback function
+ * might well execute concurrently with RCU read-side critical sections
+ * that started after call_rcu() was invoked.
+ *
+ * RCU read-side critical sections are delimited by rcu_read_lock()
+ * and rcu_read_unlock(), and may be nested. In addition, but only in
+ * v5.0 and later, regions of code across which interrupts, preemption,
+ * or softirqs have been disabled also serve as RCU read-side critical
+ * sections. This includes hardware interrupt handlers, softirq handlers,
+ * and NMI handlers.
+ *
+ * Note that all CPUs must agree that the grace period extended beyond
+ * all pre-existing RCU read-side critical section. On systems with more
+ * than one CPU, this means that when "func()" is invoked, each CPU is
+ * guaranteed to have executed a full memory barrier since the end of its
+ * last RCU read-side critical section whose beginning preceded the call
+ * to call_rcu(). It also means that each CPU executing an RCU read-side
+ * critical section that continues beyond the start of "func()" must have
+ * executed a memory barrier after the call_rcu() but before the beginning
+ * of that RCU read-side critical section. Note that these guarantees
+ * include CPUs that are offline, idle, or executing in user mode, as
+ * well as CPUs that are executing in the kernel.
+ *
+ * Furthermore, if CPU A invoked call_rcu() and CPU B invoked the
+ * resulting RCU callback function "func()", then both CPU A and CPU B are
+ * guaranteed to execute a full memory barrier during the time interval
+ * between the call to call_rcu() and the invocation of "func()" -- even
+ * if CPU A and CPU B are the same CPU (but again only if the system has
+ * more than one CPU).
+ *
+ * Implementation of these memory-ordering guarantees is described here:
+ * Documentation/RCU/Design/Memory-Ordering/Tree-RCU-Memory-Ordering.rst.
+ */
+void call_rcu(struct rcu_head *head, rcu_callback_t func)
+{
+ static atomic_t doublefrees;
unsigned long flags;
struct rcu_data *rdp;
bool was_alldone;
@@ -2598,15 +2784,18 @@ __call_rcu(struct rcu_head *head, rcu_callback_t func)
/*
* Probable double call_rcu(), so leak the callback.
* Use rcu:rcu_callback trace event to find the previous
- * time callback was passed to __call_rcu().
+ * time callback was passed to call_rcu().
*/
- WARN_ONCE(1, "__call_rcu(): Double-freed CB %p->%pS()!!!\n",
- head, head->func);
+ if (atomic_inc_return(&doublefrees) < 4) {
+ pr_err("%s(): Double-freed CB %p->%pS()!!! ", __func__, head, head->func);
+ mem_dump_obj(head);
+ }
WRITE_ONCE(head->func, rcu_leak_callback);
return;
}
head->func = func;
head->next = NULL;
+ kasan_record_aux_stack_noalloc(head);
local_irq_save(flags);
rdp = this_cpu_ptr(&rcu_data);
@@ -2621,95 +2810,91 @@ __call_rcu(struct rcu_head *head, rcu_callback_t func)
rcu_segcblist_init(&rdp->cblist);
}
+ check_cb_ovld(rdp);
if (rcu_nocb_try_bypass(rdp, head, &was_alldone, flags))
return; // Enqueued onto ->nocb_bypass, so just leave.
- /* If we get here, rcu_nocb_try_bypass() acquired ->nocb_lock. */
+ // If no-CBs CPU gets here, rcu_nocb_try_bypass() acquired ->nocb_lock.
rcu_segcblist_enqueue(&rdp->cblist, head);
- if (__is_kfree_rcu_offset((unsigned long)func))
- trace_rcu_kfree_callback(rcu_state.name, head,
+ if (__is_kvfree_rcu_offset((unsigned long)func))
+ trace_rcu_kvfree_callback(rcu_state.name, head,
(unsigned long)func,
rcu_segcblist_n_cbs(&rdp->cblist));
else
trace_rcu_callback(rcu_state.name, head,
rcu_segcblist_n_cbs(&rdp->cblist));
+ trace_rcu_segcb_stats(&rdp->cblist, TPS("SegCBQueued"));
+
/* Go handle any RCU core processing required. */
- if (IS_ENABLED(CONFIG_RCU_NOCB_CPU) &&
- unlikely(rcu_segcblist_is_offloaded(&rdp->cblist))) {
+ if (unlikely(rcu_rdp_is_offloaded(rdp))) {
__call_rcu_nocb_wake(rdp, was_alldone, flags); /* unlocks */
} else {
__call_rcu_core(rdp, head, flags);
local_irq_restore(flags);
}
}
-
-/**
- * call_rcu() - Queue an RCU callback for invocation after a grace period.
- * @head: structure to be used for queueing the RCU updates.
- * @func: actual callback function to be invoked after the grace period
- *
- * The callback function will be invoked some time after a full grace
- * period elapses, in other words after all pre-existing RCU read-side
- * critical sections have completed. However, the callback function
- * might well execute concurrently with RCU read-side critical sections
- * that started after call_rcu() was invoked. RCU read-side critical
- * sections are delimited by rcu_read_lock() and rcu_read_unlock(), and
- * may be nested. In addition, regions of code across which interrupts,
- * preemption, or softirqs have been disabled also serve as RCU read-side
- * critical sections. This includes hardware interrupt handlers, softirq
- * handlers, and NMI handlers.
- *
- * Note that all CPUs must agree that the grace period extended beyond
- * all pre-existing RCU read-side critical section. On systems with more
- * than one CPU, this means that when "func()" is invoked, each CPU is
- * guaranteed to have executed a full memory barrier since the end of its
- * last RCU read-side critical section whose beginning preceded the call
- * to call_rcu(). It also means that each CPU executing an RCU read-side
- * critical section that continues beyond the start of "func()" must have
- * executed a memory barrier after the call_rcu() but before the beginning
- * of that RCU read-side critical section. Note that these guarantees
- * include CPUs that are offline, idle, or executing in user mode, as
- * well as CPUs that are executing in the kernel.
- *
- * Furthermore, if CPU A invoked call_rcu() and CPU B invoked the
- * resulting RCU callback function "func()", then both CPU A and CPU B are
- * guaranteed to execute a full memory barrier during the time interval
- * between the call to call_rcu() and the invocation of "func()" -- even
- * if CPU A and CPU B are the same CPU (but again only if the system has
- * more than one CPU).
- */
-void call_rcu(struct rcu_head *head, rcu_callback_t func)
-{
- __call_rcu(head, func);
-}
EXPORT_SYMBOL_GPL(call_rcu);
/* Maximum number of jiffies to wait before draining a batch. */
-#define KFREE_DRAIN_JIFFIES (HZ / 50)
+#define KFREE_DRAIN_JIFFIES (5 * HZ)
#define KFREE_N_BATCHES 2
+#define FREE_N_CHANNELS 2
+
+/**
+ * struct kvfree_rcu_bulk_data - single block to store kvfree_rcu() pointers
+ * @nr_records: Number of active pointers in the array
+ * @next: Next bulk object in the block chain
+ * @records: Array of the kvfree_rcu() pointers
+ */
+struct kvfree_rcu_bulk_data {
+ unsigned long nr_records;
+ struct kvfree_rcu_bulk_data *next;
+ void *records[];
+};
+
+/*
+ * This macro defines how many entries the "records" array
+ * will contain. It is based on the fact that the size of
+ * kvfree_rcu_bulk_data structure becomes exactly one page.
+ */
+#define KVFREE_BULK_MAX_ENTR \
+ ((PAGE_SIZE - sizeof(struct kvfree_rcu_bulk_data)) / sizeof(void *))
/**
* struct kfree_rcu_cpu_work - single batch of kfree_rcu() requests
* @rcu_work: Let queue_rcu_work() invoke workqueue handler after grace period
* @head_free: List of kfree_rcu() objects waiting for a grace period
+ * @bkvhead_free: Bulk-List of kvfree_rcu() objects waiting for a grace period
* @krcp: Pointer to @kfree_rcu_cpu structure
*/
struct kfree_rcu_cpu_work {
struct rcu_work rcu_work;
struct rcu_head *head_free;
+ struct kvfree_rcu_bulk_data *bkvhead_free[FREE_N_CHANNELS];
struct kfree_rcu_cpu *krcp;
};
/**
* struct kfree_rcu_cpu - batch up kfree_rcu() requests for RCU grace period
* @head: List of kfree_rcu() objects not yet waiting for a grace period
+ * @bkvhead: Bulk-List of kvfree_rcu() objects not yet waiting for a grace period
* @krw_arr: Array of batches of kfree_rcu() objects waiting for a grace period
* @lock: Synchronize access to this structure
* @monitor_work: Promote @head to @head_free after KFREE_DRAIN_JIFFIES
- * @monitor_todo: Tracks whether a @monitor_work delayed work is pending
- * @initialized: The @lock and @rcu_work fields have been initialized
+ * @initialized: The @rcu_work fields have been initialized
+ * @count: Number of objects for which GP not started
+ * @bkvcache:
+ * A simple cache list that contains objects for reuse purpose.
+ * In order to save some per-cpu space the list is singular.
+ * Even though it is lockless an access has to be protected by the
+ * per-cpu lock.
+ * @page_cache_work: A work to refill the cache when it is empty
+ * @backoff_page_cache_fill: Delay cache refills
+ * @work_in_progress: Indicates that page_cache_work is running
+ * @hrtimer: A hrtimer for scheduling a page_cache_work
+ * @nr_bkv_objs: number of allocated objects at @bkvcache.
*
* This is a per-CPU structure. The reason that it is not included in
* the rcu_data structure is to permit this code to be extracted from
@@ -2718,210 +2903,559 @@ struct kfree_rcu_cpu_work {
*/
struct kfree_rcu_cpu {
struct rcu_head *head;
+ struct kvfree_rcu_bulk_data *bkvhead[FREE_N_CHANNELS];
struct kfree_rcu_cpu_work krw_arr[KFREE_N_BATCHES];
- spinlock_t lock;
+ raw_spinlock_t lock;
struct delayed_work monitor_work;
- bool monitor_todo;
bool initialized;
+ int count;
+
+ struct delayed_work page_cache_work;
+ atomic_t backoff_page_cache_fill;
+ atomic_t work_in_progress;
+ struct hrtimer hrtimer;
+
+ struct llist_head bkvcache;
+ int nr_bkv_objs;
};
-static DEFINE_PER_CPU(struct kfree_rcu_cpu, krc);
+static DEFINE_PER_CPU(struct kfree_rcu_cpu, krc) = {
+ .lock = __RAW_SPIN_LOCK_UNLOCKED(krc.lock),
+};
+
+static __always_inline void
+debug_rcu_bhead_unqueue(struct kvfree_rcu_bulk_data *bhead)
+{
+#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
+ int i;
+
+ for (i = 0; i < bhead->nr_records; i++)
+ debug_rcu_head_unqueue((struct rcu_head *)(bhead->records[i]));
+#endif
+}
+
+static inline struct kfree_rcu_cpu *
+krc_this_cpu_lock(unsigned long *flags)
+{
+ struct kfree_rcu_cpu *krcp;
+
+ local_irq_save(*flags); // For safely calling this_cpu_ptr().
+ krcp = this_cpu_ptr(&krc);
+ raw_spin_lock(&krcp->lock);
+
+ return krcp;
+}
+
+static inline void
+krc_this_cpu_unlock(struct kfree_rcu_cpu *krcp, unsigned long flags)
+{
+ raw_spin_unlock_irqrestore(&krcp->lock, flags);
+}
+
+static inline struct kvfree_rcu_bulk_data *
+get_cached_bnode(struct kfree_rcu_cpu *krcp)
+{
+ if (!krcp->nr_bkv_objs)
+ return NULL;
+
+ WRITE_ONCE(krcp->nr_bkv_objs, krcp->nr_bkv_objs - 1);
+ return (struct kvfree_rcu_bulk_data *)
+ llist_del_first(&krcp->bkvcache);
+}
+
+static inline bool
+put_cached_bnode(struct kfree_rcu_cpu *krcp,
+ struct kvfree_rcu_bulk_data *bnode)
+{
+ // Check the limit.
+ if (krcp->nr_bkv_objs >= rcu_min_cached_objs)
+ return false;
+
+ llist_add((struct llist_node *) bnode, &krcp->bkvcache);
+ WRITE_ONCE(krcp->nr_bkv_objs, krcp->nr_bkv_objs + 1);
+ return true;
+}
+
+static int
+drain_page_cache(struct kfree_rcu_cpu *krcp)
+{
+ unsigned long flags;
+ struct llist_node *page_list, *pos, *n;
+ int freed = 0;
+
+ raw_spin_lock_irqsave(&krcp->lock, flags);
+ page_list = llist_del_all(&krcp->bkvcache);
+ WRITE_ONCE(krcp->nr_bkv_objs, 0);
+ raw_spin_unlock_irqrestore(&krcp->lock, flags);
+
+ llist_for_each_safe(pos, n, page_list) {
+ free_page((unsigned long)pos);
+ freed++;
+ }
+
+ return freed;
+}
/*
* This function is invoked in workqueue context after a grace period.
- * It frees all the objects queued on ->head_free.
+ * It frees all the objects queued on ->bkvhead_free or ->head_free.
*/
static void kfree_rcu_work(struct work_struct *work)
{
unsigned long flags;
+ struct kvfree_rcu_bulk_data *bkvhead[FREE_N_CHANNELS], *bnext;
struct rcu_head *head, *next;
struct kfree_rcu_cpu *krcp;
struct kfree_rcu_cpu_work *krwp;
+ int i, j;
krwp = container_of(to_rcu_work(work),
struct kfree_rcu_cpu_work, rcu_work);
krcp = krwp->krcp;
- spin_lock_irqsave(&krcp->lock, flags);
+
+ raw_spin_lock_irqsave(&krcp->lock, flags);
+ // Channels 1 and 2.
+ for (i = 0; i < FREE_N_CHANNELS; i++) {
+ bkvhead[i] = krwp->bkvhead_free[i];
+ krwp->bkvhead_free[i] = NULL;
+ }
+
+ // Channel 3.
head = krwp->head_free;
krwp->head_free = NULL;
- spin_unlock_irqrestore(&krcp->lock, flags);
+ raw_spin_unlock_irqrestore(&krcp->lock, flags);
+
+ // Handle the first two channels.
+ for (i = 0; i < FREE_N_CHANNELS; i++) {
+ for (; bkvhead[i]; bkvhead[i] = bnext) {
+ bnext = bkvhead[i]->next;
+ debug_rcu_bhead_unqueue(bkvhead[i]);
+
+ rcu_lock_acquire(&rcu_callback_map);
+ if (i == 0) { // kmalloc() / kfree().
+ trace_rcu_invoke_kfree_bulk_callback(
+ rcu_state.name, bkvhead[i]->nr_records,
+ bkvhead[i]->records);
+
+ kfree_bulk(bkvhead[i]->nr_records,
+ bkvhead[i]->records);
+ } else { // vmalloc() / vfree().
+ for (j = 0; j < bkvhead[i]->nr_records; j++) {
+ trace_rcu_invoke_kvfree_callback(
+ rcu_state.name,
+ bkvhead[i]->records[j], 0);
+
+ vfree(bkvhead[i]->records[j]);
+ }
+ }
+ rcu_lock_release(&rcu_callback_map);
+
+ raw_spin_lock_irqsave(&krcp->lock, flags);
+ if (put_cached_bnode(krcp, bkvhead[i]))
+ bkvhead[i] = NULL;
+ raw_spin_unlock_irqrestore(&krcp->lock, flags);
+
+ if (bkvhead[i])
+ free_page((unsigned long) bkvhead[i]);
+
+ cond_resched_tasks_rcu_qs();
+ }
+ }
- // List "head" is now private, so traverse locklessly.
+ /*
+ * This is used when the "bulk" path can not be used for the
+ * double-argument of kvfree_rcu(). This happens when the
+ * page-cache is empty, which means that objects are instead
+ * queued on a linked list through their rcu_head structures.
+ * This list is named "Channel 3".
+ */
for (; head; head = next) {
unsigned long offset = (unsigned long)head->func;
+ void *ptr = (void *)head - offset;
next = head->next;
- // Potentially optimize with kfree_bulk in future.
- debug_rcu_head_unqueue(head);
+ debug_rcu_head_unqueue((struct rcu_head *)ptr);
rcu_lock_acquire(&rcu_callback_map);
- trace_rcu_invoke_kfree_callback(rcu_state.name, head, offset);
+ trace_rcu_invoke_kvfree_callback(rcu_state.name, head, offset);
- if (!WARN_ON_ONCE(!__is_kfree_rcu_offset(offset))) {
- /* Could be optimized with kfree_bulk() in future. */
- kfree((void *)head - offset);
- }
+ if (!WARN_ON_ONCE(!__is_kvfree_rcu_offset(offset)))
+ kvfree(ptr);
rcu_lock_release(&rcu_callback_map);
cond_resched_tasks_rcu_qs();
}
}
-/*
- * Schedule the kfree batch RCU work to run in workqueue context after a GP.
- *
- * This function is invoked by kfree_rcu_monitor() when the KFREE_DRAIN_JIFFIES
- * timeout has been reached.
- */
-static inline bool queue_kfree_rcu_work(struct kfree_rcu_cpu *krcp)
+static bool
+need_offload_krc(struct kfree_rcu_cpu *krcp)
{
int i;
- struct kfree_rcu_cpu_work *krwp = NULL;
- lockdep_assert_held(&krcp->lock);
- for (i = 0; i < KFREE_N_BATCHES; i++)
- if (!krcp->krw_arr[i].head_free) {
- krwp = &(krcp->krw_arr[i]);
- break;
- }
+ for (i = 0; i < FREE_N_CHANNELS; i++)
+ if (krcp->bkvhead[i])
+ return true;
- // If a previous RCU batch is in progress, we cannot immediately
- // queue another one, so return false to tell caller to retry.
- if (!krwp)
- return false;
-
- krwp->head_free = krcp->head;
- krcp->head = NULL;
- INIT_RCU_WORK(&krwp->rcu_work, kfree_rcu_work);
- queue_rcu_work(system_wq, &krwp->rcu_work);
- return true;
+ return !!krcp->head;
}
-static inline void kfree_rcu_drain_unlock(struct kfree_rcu_cpu *krcp,
- unsigned long flags)
+static void
+schedule_delayed_monitor_work(struct kfree_rcu_cpu *krcp)
{
- // Attempt to start a new batch.
- krcp->monitor_todo = false;
- if (queue_kfree_rcu_work(krcp)) {
- // Success! Our job is done here.
- spin_unlock_irqrestore(&krcp->lock, flags);
+ long delay, delay_left;
+
+ delay = READ_ONCE(krcp->count) >= KVFREE_BULK_MAX_ENTR ? 1:KFREE_DRAIN_JIFFIES;
+ if (delayed_work_pending(&krcp->monitor_work)) {
+ delay_left = krcp->monitor_work.timer.expires - jiffies;
+ if (delay < delay_left)
+ mod_delayed_work(system_wq, &krcp->monitor_work, delay);
return;
}
-
- // Previous RCU batch still in progress, try again later.
- krcp->monitor_todo = true;
- schedule_delayed_work(&krcp->monitor_work, KFREE_DRAIN_JIFFIES);
- spin_unlock_irqrestore(&krcp->lock, flags);
+ queue_delayed_work(system_wq, &krcp->monitor_work, delay);
}
/*
* This function is invoked after the KFREE_DRAIN_JIFFIES timeout.
- * It invokes kfree_rcu_drain_unlock() to attempt to start another batch.
*/
static void kfree_rcu_monitor(struct work_struct *work)
{
+ struct kfree_rcu_cpu *krcp = container_of(work,
+ struct kfree_rcu_cpu, monitor_work.work);
unsigned long flags;
- struct kfree_rcu_cpu *krcp = container_of(work, struct kfree_rcu_cpu,
- monitor_work.work);
+ int i, j;
- spin_lock_irqsave(&krcp->lock, flags);
- if (krcp->monitor_todo)
- kfree_rcu_drain_unlock(krcp, flags);
- else
- spin_unlock_irqrestore(&krcp->lock, flags);
+ raw_spin_lock_irqsave(&krcp->lock, flags);
+
+ // Attempt to start a new batch.
+ for (i = 0; i < KFREE_N_BATCHES; i++) {
+ struct kfree_rcu_cpu_work *krwp = &(krcp->krw_arr[i]);
+
+ // Try to detach bkvhead or head and attach it over any
+ // available corresponding free channel. It can be that
+ // a previous RCU batch is in progress, it means that
+ // immediately to queue another one is not possible so
+ // in that case the monitor work is rearmed.
+ if ((krcp->bkvhead[0] && !krwp->bkvhead_free[0]) ||
+ (krcp->bkvhead[1] && !krwp->bkvhead_free[1]) ||
+ (krcp->head && !krwp->head_free)) {
+ // Channel 1 corresponds to the SLAB-pointer bulk path.
+ // Channel 2 corresponds to vmalloc-pointer bulk path.
+ for (j = 0; j < FREE_N_CHANNELS; j++) {
+ if (!krwp->bkvhead_free[j]) {
+ krwp->bkvhead_free[j] = krcp->bkvhead[j];
+ krcp->bkvhead[j] = NULL;
+ }
+ }
+
+ // Channel 3 corresponds to both SLAB and vmalloc
+ // objects queued on the linked list.
+ if (!krwp->head_free) {
+ krwp->head_free = krcp->head;
+ krcp->head = NULL;
+ }
+
+ WRITE_ONCE(krcp->count, 0);
+
+ // One work is per one batch, so there are three
+ // "free channels", the batch can handle. It can
+ // be that the work is in the pending state when
+ // channels have been detached following by each
+ // other.
+ queue_rcu_work(system_wq, &krwp->rcu_work);
+ }
+ }
+
+ // If there is nothing to detach, it means that our job is
+ // successfully done here. In case of having at least one
+ // of the channels that is still busy we should rearm the
+ // work to repeat an attempt. Because previous batches are
+ // still in progress.
+ if (need_offload_krc(krcp))
+ schedule_delayed_monitor_work(krcp);
+
+ raw_spin_unlock_irqrestore(&krcp->lock, flags);
+}
+
+static enum hrtimer_restart
+schedule_page_work_fn(struct hrtimer *t)
+{
+ struct kfree_rcu_cpu *krcp =
+ container_of(t, struct kfree_rcu_cpu, hrtimer);
+
+ queue_delayed_work(system_highpri_wq, &krcp->page_cache_work, 0);
+ return HRTIMER_NORESTART;
+}
+
+static void fill_page_cache_func(struct work_struct *work)
+{
+ struct kvfree_rcu_bulk_data *bnode;
+ struct kfree_rcu_cpu *krcp =
+ container_of(work, struct kfree_rcu_cpu,
+ page_cache_work.work);
+ unsigned long flags;
+ int nr_pages;
+ bool pushed;
+ int i;
+
+ nr_pages = atomic_read(&krcp->backoff_page_cache_fill) ?
+ 1 : rcu_min_cached_objs;
+
+ for (i = 0; i < nr_pages; i++) {
+ bnode = (struct kvfree_rcu_bulk_data *)
+ __get_free_page(GFP_KERNEL | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
+
+ if (!bnode)
+ break;
+
+ raw_spin_lock_irqsave(&krcp->lock, flags);
+ pushed = put_cached_bnode(krcp, bnode);
+ raw_spin_unlock_irqrestore(&krcp->lock, flags);
+
+ if (!pushed) {
+ free_page((unsigned long) bnode);
+ break;
+ }
+ }
+
+ atomic_set(&krcp->work_in_progress, 0);
+ atomic_set(&krcp->backoff_page_cache_fill, 0);
+}
+
+static void
+run_page_cache_worker(struct kfree_rcu_cpu *krcp)
+{
+ if (rcu_scheduler_active == RCU_SCHEDULER_RUNNING &&
+ !atomic_xchg(&krcp->work_in_progress, 1)) {
+ if (atomic_read(&krcp->backoff_page_cache_fill)) {
+ queue_delayed_work(system_wq,
+ &krcp->page_cache_work,
+ msecs_to_jiffies(rcu_delay_page_cache_fill_msec));
+ } else {
+ hrtimer_init(&krcp->hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
+ krcp->hrtimer.function = schedule_page_work_fn;
+ hrtimer_start(&krcp->hrtimer, 0, HRTIMER_MODE_REL);
+ }
+ }
+}
+
+// Record ptr in a page managed by krcp, with the pre-krc_this_cpu_lock()
+// state specified by flags. If can_alloc is true, the caller must
+// be schedulable and not be holding any locks or mutexes that might be
+// acquired by the memory allocator or anything that it might invoke.
+// Returns true if ptr was successfully recorded, else the caller must
+// use a fallback.
+static inline bool
+add_ptr_to_bulk_krc_lock(struct kfree_rcu_cpu **krcp,
+ unsigned long *flags, void *ptr, bool can_alloc)
+{
+ struct kvfree_rcu_bulk_data *bnode;
+ int idx;
+
+ *krcp = krc_this_cpu_lock(flags);
+ if (unlikely(!(*krcp)->initialized))
+ return false;
+
+ idx = !!is_vmalloc_addr(ptr);
+
+ /* Check if a new block is required. */
+ if (!(*krcp)->bkvhead[idx] ||
+ (*krcp)->bkvhead[idx]->nr_records == KVFREE_BULK_MAX_ENTR) {
+ bnode = get_cached_bnode(*krcp);
+ if (!bnode && can_alloc) {
+ krc_this_cpu_unlock(*krcp, *flags);
+
+ // __GFP_NORETRY - allows a light-weight direct reclaim
+ // what is OK from minimizing of fallback hitting point of
+ // view. Apart of that it forbids any OOM invoking what is
+ // also beneficial since we are about to release memory soon.
+ //
+ // __GFP_NOMEMALLOC - prevents from consuming of all the
+ // memory reserves. Please note we have a fallback path.
+ //
+ // __GFP_NOWARN - it is supposed that an allocation can
+ // be failed under low memory or high memory pressure
+ // scenarios.
+ bnode = (struct kvfree_rcu_bulk_data *)
+ __get_free_page(GFP_KERNEL | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
+ *krcp = krc_this_cpu_lock(flags);
+ }
+
+ if (!bnode)
+ return false;
+
+ /* Initialize the new block. */
+ bnode->nr_records = 0;
+ bnode->next = (*krcp)->bkvhead[idx];
+
+ /* Attach it to the head. */
+ (*krcp)->bkvhead[idx] = bnode;
+ }
+
+ /* Finally insert. */
+ (*krcp)->bkvhead[idx]->records
+ [(*krcp)->bkvhead[idx]->nr_records++] = ptr;
+
+ return true;
}
/*
- * Queue a request for lazy invocation of kfree() after a grace period.
+ * Queue a request for lazy invocation of the appropriate free routine
+ * after a grace period. Please note that three paths are maintained,
+ * two for the common case using arrays of pointers and a third one that
+ * is used only when the main paths cannot be used, for example, due to
+ * memory pressure.
*
- * Each kfree_call_rcu() request is added to a batch. The batch will be drained
- * every KFREE_DRAIN_JIFFIES number of jiffies. All the objects in the batch
- * will be kfree'd in workqueue context. This allows us to:
- *
- * 1. Batch requests together to reduce the number of grace periods during
- * heavy kfree_rcu() load.
- *
- * 2. It makes it possible to use kfree_bulk() on a large number of
- * kfree_rcu() requests thus reducing cache misses and the per-object
- * overhead of kfree().
+ * Each kvfree_call_rcu() request is added to a batch. The batch will be drained
+ * every KFREE_DRAIN_JIFFIES number of jiffies. All the objects in the batch will
+ * be free'd in workqueue context. This allows us to: batch requests together to
+ * reduce the number of grace periods during heavy kfree_rcu()/kvfree_rcu() load.
*/
-void kfree_call_rcu(struct rcu_head *head, rcu_callback_t func)
+void kvfree_call_rcu(struct rcu_head *head, rcu_callback_t func)
{
unsigned long flags;
struct kfree_rcu_cpu *krcp;
+ bool success;
+ void *ptr;
- local_irq_save(flags); // For safely calling this_cpu_ptr().
- krcp = this_cpu_ptr(&krc);
- if (krcp->initialized)
- spin_lock(&krcp->lock);
+ if (head) {
+ ptr = (void *) head - (unsigned long) func;
+ } else {
+ /*
+ * Please note there is a limitation for the head-less
+ * variant, that is why there is a clear rule for such
+ * objects: it can be used from might_sleep() context
+ * only. For other places please embed an rcu_head to
+ * your data.
+ */
+ might_sleep();
+ ptr = (unsigned long *) func;
+ }
// Queue the object but don't yet schedule the batch.
- if (debug_rcu_head_queue(head)) {
+ if (debug_rcu_head_queue(ptr)) {
// Probable double kfree_rcu(), just leak.
WARN_ONCE(1, "%s(): Double-freed call. rcu_head %p\n",
__func__, head);
- goto unlock_return;
+
+ // Mark as success and leave.
+ return;
}
- head->func = func;
- head->next = krcp->head;
- krcp->head = head;
- // Set timer to drain after KFREE_DRAIN_JIFFIES.
- if (rcu_scheduler_active == RCU_SCHEDULER_RUNNING &&
- !krcp->monitor_todo) {
- krcp->monitor_todo = true;
- schedule_delayed_work(&krcp->monitor_work, KFREE_DRAIN_JIFFIES);
+ kasan_record_aux_stack_noalloc(ptr);
+ success = add_ptr_to_bulk_krc_lock(&krcp, &flags, ptr, !head);
+ if (!success) {
+ run_page_cache_worker(krcp);
+
+ if (head == NULL)
+ // Inline if kvfree_rcu(one_arg) call.
+ goto unlock_return;
+
+ head->func = func;
+ head->next = krcp->head;
+ krcp->head = head;
+ success = true;
}
+ WRITE_ONCE(krcp->count, krcp->count + 1);
+
+ // Set timer to drain after KFREE_DRAIN_JIFFIES.
+ if (rcu_scheduler_active == RCU_SCHEDULER_RUNNING)
+ schedule_delayed_monitor_work(krcp);
+
unlock_return:
- if (krcp->initialized)
- spin_unlock(&krcp->lock);
- local_irq_restore(flags);
+ krc_this_cpu_unlock(krcp, flags);
+
+ /*
+ * Inline kvfree() after synchronize_rcu(). We can do
+ * it from might_sleep() context only, so the current
+ * CPU can pass the QS state.
+ */
+ if (!success) {
+ debug_rcu_head_unqueue((struct rcu_head *) ptr);
+ synchronize_rcu();
+ kvfree(ptr);
+ }
+}
+EXPORT_SYMBOL_GPL(kvfree_call_rcu);
+
+static unsigned long
+kfree_rcu_shrink_count(struct shrinker *shrink, struct shrink_control *sc)
+{
+ int cpu;
+ unsigned long count = 0;
+
+ /* Snapshot count of all CPUs */
+ for_each_possible_cpu(cpu) {
+ struct kfree_rcu_cpu *krcp = per_cpu_ptr(&krc, cpu);
+
+ count += READ_ONCE(krcp->count);
+ count += READ_ONCE(krcp->nr_bkv_objs);
+ atomic_set(&krcp->backoff_page_cache_fill, 1);
+ }
+
+ return count == 0 ? SHRINK_EMPTY : count;
+}
+
+static unsigned long
+kfree_rcu_shrink_scan(struct shrinker *shrink, struct shrink_control *sc)
+{
+ int cpu, freed = 0;
+
+ for_each_possible_cpu(cpu) {
+ int count;
+ struct kfree_rcu_cpu *krcp = per_cpu_ptr(&krc, cpu);
+
+ count = krcp->count;
+ count += drain_page_cache(krcp);
+ kfree_rcu_monitor(&krcp->monitor_work.work);
+
+ sc->nr_to_scan -= count;
+ freed += count;
+
+ if (sc->nr_to_scan <= 0)
+ break;
+ }
+
+ return freed == 0 ? SHRINK_STOP : freed;
}
-EXPORT_SYMBOL_GPL(kfree_call_rcu);
+
+static struct shrinker kfree_rcu_shrinker = {
+ .count_objects = kfree_rcu_shrink_count,
+ .scan_objects = kfree_rcu_shrink_scan,
+ .batch = 0,
+ .seeks = DEFAULT_SEEKS,
+};
void __init kfree_rcu_scheduler_running(void)
{
int cpu;
unsigned long flags;
- for_each_online_cpu(cpu) {
+ for_each_possible_cpu(cpu) {
struct kfree_rcu_cpu *krcp = per_cpu_ptr(&krc, cpu);
- spin_lock_irqsave(&krcp->lock, flags);
- if (!krcp->head || krcp->monitor_todo) {
- spin_unlock_irqrestore(&krcp->lock, flags);
- continue;
- }
- krcp->monitor_todo = true;
- schedule_delayed_work_on(cpu, &krcp->monitor_work,
- KFREE_DRAIN_JIFFIES);
- spin_unlock_irqrestore(&krcp->lock, flags);
+ raw_spin_lock_irqsave(&krcp->lock, flags);
+ if (need_offload_krc(krcp))
+ schedule_delayed_monitor_work(krcp);
+ raw_spin_unlock_irqrestore(&krcp->lock, flags);
}
}
/*
* During early boot, any blocking grace-period wait automatically
- * implies a grace period. Later on, this is never the case for PREEMPTION.
+ * implies a grace period.
*
- * Howevr, because a context switch is a grace period for !PREEMPTION, any
- * blocking grace-period wait automatically implies a grace period if
- * there is only one CPU online at any point time during execution of
- * either synchronize_rcu() or synchronize_rcu_expedited(). It is OK to
- * occasionally incorrectly indicate that there are multiple CPUs online
- * when there was in fact only one the whole time, as this just adds some
- * overhead: RCU still operates correctly.
+ * Later on, this could in theory be the case for kernels built with
+ * CONFIG_SMP=y && CONFIG_PREEMPTION=y running on a single CPU, but this
+ * is not a common case. Furthermore, this optimization would cause
+ * the rcu_gp_oldstate structure to expand by 50%, so this potential
+ * grace-period optimization is ignored once the scheduler is running.
*/
static int rcu_blocking_is_gp(void)
{
- int ret;
-
- if (IS_ENABLED(CONFIG_PREEMPTION))
- return rcu_scheduler_active == RCU_SCHEDULER_INACTIVE;
+ if (rcu_scheduler_active != RCU_SCHEDULER_INACTIVE)
+ return false;
might_sleep(); /* Check for RCU read-side critical section. */
- preempt_disable();
- ret = num_online_cpus() <= 1;
- preempt_enable();
- return ret;
+ return true;
}
/**
@@ -2932,10 +3466,12 @@ static int rcu_blocking_is_gp(void)
* read-side critical sections have completed. Note, however, that
* upon return from synchronize_rcu(), the caller might well be executing
* concurrently with new RCU read-side critical sections that began while
- * synchronize_rcu() was waiting. RCU read-side critical sections are
- * delimited by rcu_read_lock() and rcu_read_unlock(), and may be nested.
- * In addition, regions of code across which interrupts, preemption, or
- * softirqs have been disabled also serve as RCU read-side critical
+ * synchronize_rcu() was waiting.
+ *
+ * RCU read-side critical sections are delimited by rcu_read_lock()
+ * and rcu_read_unlock(), and may be nested. In addition, but only in
+ * v5.0 and later, regions of code across which interrupts, preemption,
+ * or softirqs have been disabled also serve as RCU read-side critical
* sections. This includes hardware interrupt handlers, softirq handlers,
* and NMI handlers.
*
@@ -2956,28 +3492,70 @@ static int rcu_blocking_is_gp(void)
* to have executed a full memory barrier during the execution of
* synchronize_rcu() -- even if CPU A and CPU B are the same CPU (but
* again only if the system has more than one CPU).
+ *
+ * Implementation of these memory-ordering guarantees is described here:
+ * Documentation/RCU/Design/Memory-Ordering/Tree-RCU-Memory-Ordering.rst.
*/
void synchronize_rcu(void)
{
+ unsigned long flags;
+ struct rcu_node *rnp;
+
RCU_LOCKDEP_WARN(lock_is_held(&rcu_bh_lock_map) ||
lock_is_held(&rcu_lock_map) ||
lock_is_held(&rcu_sched_lock_map),
"Illegal synchronize_rcu() in RCU read-side critical section");
- if (rcu_blocking_is_gp())
+ if (!rcu_blocking_is_gp()) {
+ if (rcu_gp_is_expedited())
+ synchronize_rcu_expedited();
+ else
+ wait_rcu_gp(call_rcu);
return;
- if (rcu_gp_is_expedited())
- synchronize_rcu_expedited();
- else
- wait_rcu_gp(call_rcu);
+ }
+
+ // Context allows vacuous grace periods.
+ // Note well that this code runs with !PREEMPT && !SMP.
+ // In addition, all code that advances grace periods runs at
+ // process level. Therefore, this normal GP overlaps with other
+ // normal GPs only by being fully nested within them, which allows
+ // reuse of ->gp_seq_polled_snap.
+ rcu_poll_gp_seq_start_unlocked(&rcu_state.gp_seq_polled_snap);
+ rcu_poll_gp_seq_end_unlocked(&rcu_state.gp_seq_polled_snap);
+
+ // Update the normal grace-period counters to record
+ // this grace period, but only those used by the boot CPU.
+ // The rcu_scheduler_starting() will take care of the rest of
+ // these counters.
+ local_irq_save(flags);
+ WARN_ON_ONCE(num_online_cpus() > 1);
+ rcu_state.gp_seq += (1 << RCU_SEQ_CTR_SHIFT);
+ for (rnp = this_cpu_ptr(&rcu_data)->mynode; rnp; rnp = rnp->parent)
+ rnp->gp_seq_needed = rnp->gp_seq = rcu_state.gp_seq;
+ local_irq_restore(flags);
}
EXPORT_SYMBOL_GPL(synchronize_rcu);
/**
+ * get_completed_synchronize_rcu_full - Return a full pre-completed polled state cookie
+ * @rgosp: Place to put state cookie
+ *
+ * Stores into @rgosp a value that will always be treated by functions
+ * like poll_state_synchronize_rcu_full() as a cookie whose grace period
+ * has already completed.
+ */
+void get_completed_synchronize_rcu_full(struct rcu_gp_oldstate *rgosp)
+{
+ rgosp->rgos_norm = RCU_GET_STATE_COMPLETED;
+ rgosp->rgos_exp = RCU_GET_STATE_COMPLETED;
+}
+EXPORT_SYMBOL_GPL(get_completed_synchronize_rcu_full);
+
+/**
* get_state_synchronize_rcu - Snapshot current RCU state
*
* Returns a cookie that is used by a later call to cond_synchronize_rcu()
- * to determine whether or not a full grace period has elapsed in the
- * meantime.
+ * or poll_state_synchronize_rcu() to determine whether or not a full
+ * grace period has elapsed in the meantime.
*/
unsigned long get_state_synchronize_rcu(void)
{
@@ -2986,33 +3564,248 @@ unsigned long get_state_synchronize_rcu(void)
* before the load from ->gp_seq.
*/
smp_mb(); /* ^^^ */
- return rcu_seq_snap(&rcu_state.gp_seq);
+ return rcu_seq_snap(&rcu_state.gp_seq_polled);
}
EXPORT_SYMBOL_GPL(get_state_synchronize_rcu);
/**
- * cond_synchronize_rcu - Conditionally wait for an RCU grace period
+ * get_state_synchronize_rcu_full - Snapshot RCU state, both normal and expedited
+ * @rgosp: location to place combined normal/expedited grace-period state
*
- * @oldstate: return value from earlier call to get_state_synchronize_rcu()
+ * Places the normal and expedited grace-period states in @rgosp. This
+ * state value can be passed to a later call to cond_synchronize_rcu_full()
+ * or poll_state_synchronize_rcu_full() to determine whether or not a
+ * grace period (whether normal or expedited) has elapsed in the meantime.
+ * The rcu_gp_oldstate structure takes up twice the memory of an unsigned
+ * long, but is guaranteed to see all grace periods. In contrast, the
+ * combined state occupies less memory, but can sometimes fail to take
+ * grace periods into account.
+ *
+ * This does not guarantee that the needed grace period will actually
+ * start.
+ */
+void get_state_synchronize_rcu_full(struct rcu_gp_oldstate *rgosp)
+{
+ struct rcu_node *rnp = rcu_get_root();
+
+ /*
+ * Any prior manipulation of RCU-protected data must happen
+ * before the loads from ->gp_seq and ->expedited_sequence.
+ */
+ smp_mb(); /* ^^^ */
+ rgosp->rgos_norm = rcu_seq_snap(&rnp->gp_seq);
+ rgosp->rgos_exp = rcu_seq_snap(&rcu_state.expedited_sequence);
+}
+EXPORT_SYMBOL_GPL(get_state_synchronize_rcu_full);
+
+/*
+ * Helper function for start_poll_synchronize_rcu() and
+ * start_poll_synchronize_rcu_full().
+ */
+static void start_poll_synchronize_rcu_common(void)
+{
+ unsigned long flags;
+ bool needwake;
+ struct rcu_data *rdp;
+ struct rcu_node *rnp;
+
+ lockdep_assert_irqs_enabled();
+ local_irq_save(flags);
+ rdp = this_cpu_ptr(&rcu_data);
+ rnp = rdp->mynode;
+ raw_spin_lock_rcu_node(rnp); // irqs already disabled.
+ // Note it is possible for a grace period to have elapsed between
+ // the above call to get_state_synchronize_rcu() and the below call
+ // to rcu_seq_snap. This is OK, the worst that happens is that we
+ // get a grace period that no one needed. These accesses are ordered
+ // by smp_mb(), and we are accessing them in the opposite order
+ // from which they are updated at grace-period start, as required.
+ needwake = rcu_start_this_gp(rnp, rdp, rcu_seq_snap(&rcu_state.gp_seq));
+ raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
+ if (needwake)
+ rcu_gp_kthread_wake();
+}
+
+/**
+ * start_poll_synchronize_rcu - Snapshot and start RCU grace period
+ *
+ * Returns a cookie that is used by a later call to cond_synchronize_rcu()
+ * or poll_state_synchronize_rcu() to determine whether or not a full
+ * grace period has elapsed in the meantime. If the needed grace period
+ * is not already slated to start, notifies RCU core of the need for that
+ * grace period.
+ *
+ * Interrupts must be enabled for the case where it is necessary to awaken
+ * the grace-period kthread.
+ */
+unsigned long start_poll_synchronize_rcu(void)
+{
+ unsigned long gp_seq = get_state_synchronize_rcu();
+
+ start_poll_synchronize_rcu_common();
+ return gp_seq;
+}
+EXPORT_SYMBOL_GPL(start_poll_synchronize_rcu);
+
+/**
+ * start_poll_synchronize_rcu_full - Take a full snapshot and start RCU grace period
+ * @rgosp: value from get_state_synchronize_rcu_full() or start_poll_synchronize_rcu_full()
+ *
+ * Places the normal and expedited grace-period states in *@rgos. This
+ * state value can be passed to a later call to cond_synchronize_rcu_full()
+ * or poll_state_synchronize_rcu_full() to determine whether or not a
+ * grace period (whether normal or expedited) has elapsed in the meantime.
+ * If the needed grace period is not already slated to start, notifies
+ * RCU core of the need for that grace period.
+ *
+ * Interrupts must be enabled for the case where it is necessary to awaken
+ * the grace-period kthread.
+ */
+void start_poll_synchronize_rcu_full(struct rcu_gp_oldstate *rgosp)
+{
+ get_state_synchronize_rcu_full(rgosp);
+
+ start_poll_synchronize_rcu_common();
+}
+EXPORT_SYMBOL_GPL(start_poll_synchronize_rcu_full);
+
+/**
+ * poll_state_synchronize_rcu - Has the specified RCU grace period completed?
+ * @oldstate: value from get_state_synchronize_rcu() or start_poll_synchronize_rcu()
+ *
+ * If a full RCU grace period has elapsed since the earlier call from
+ * which @oldstate was obtained, return @true, otherwise return @false.
+ * If @false is returned, it is the caller's responsibility to invoke this
+ * function later on until it does return @true. Alternatively, the caller
+ * can explicitly wait for a grace period, for example, by passing @oldstate
+ * to cond_synchronize_rcu() or by directly invoking synchronize_rcu().
+ *
+ * Yes, this function does not take counter wrap into account.
+ * But counter wrap is harmless. If the counter wraps, we have waited for
+ * more than a billion grace periods (and way more on a 64-bit system!).
+ * Those needing to keep old state values for very long time periods
+ * (many hours even on 32-bit systems) should check them occasionally and
+ * either refresh them or set a flag indicating that the grace period has
+ * completed. Alternatively, they can use get_completed_synchronize_rcu()
+ * to get a guaranteed-completed grace-period state.
+ *
+ * This function provides the same memory-ordering guarantees that
+ * would be provided by a synchronize_rcu() that was invoked at the call
+ * to the function that provided @oldstate, and that returned at the end
+ * of this function.
+ */
+bool poll_state_synchronize_rcu(unsigned long oldstate)
+{
+ if (oldstate == RCU_GET_STATE_COMPLETED ||
+ rcu_seq_done_exact(&rcu_state.gp_seq_polled, oldstate)) {
+ smp_mb(); /* Ensure GP ends before subsequent accesses. */
+ return true;
+ }
+ return false;
+}
+EXPORT_SYMBOL_GPL(poll_state_synchronize_rcu);
+
+/**
+ * poll_state_synchronize_rcu_full - Has the specified RCU grace period completed?
+ * @rgosp: value from get_state_synchronize_rcu_full() or start_poll_synchronize_rcu_full()
+ *
+ * If a full RCU grace period has elapsed since the earlier call from
+ * which *rgosp was obtained, return @true, otherwise return @false.
+ * If @false is returned, it is the caller's responsibility to invoke this
+ * function later on until it does return @true. Alternatively, the caller
+ * can explicitly wait for a grace period, for example, by passing @rgosp
+ * to cond_synchronize_rcu() or by directly invoking synchronize_rcu().
+ *
+ * Yes, this function does not take counter wrap into account.
+ * But counter wrap is harmless. If the counter wraps, we have waited
+ * for more than a billion grace periods (and way more on a 64-bit
+ * system!). Those needing to keep rcu_gp_oldstate values for very
+ * long time periods (many hours even on 32-bit systems) should check
+ * them occasionally and either refresh them or set a flag indicating
+ * that the grace period has completed. Alternatively, they can use
+ * get_completed_synchronize_rcu_full() to get a guaranteed-completed
+ * grace-period state.
+ *
+ * This function provides the same memory-ordering guarantees that would
+ * be provided by a synchronize_rcu() that was invoked at the call to
+ * the function that provided @rgosp, and that returned at the end of this
+ * function. And this guarantee requires that the root rcu_node structure's
+ * ->gp_seq field be checked instead of that of the rcu_state structure.
+ * The problem is that the just-ending grace-period's callbacks can be
+ * invoked between the time that the root rcu_node structure's ->gp_seq
+ * field is updated and the time that the rcu_state structure's ->gp_seq
+ * field is updated. Therefore, if a single synchronize_rcu() is to
+ * cause a subsequent poll_state_synchronize_rcu_full() to return @true,
+ * then the root rcu_node structure is the one that needs to be polled.
+ */
+bool poll_state_synchronize_rcu_full(struct rcu_gp_oldstate *rgosp)
+{
+ struct rcu_node *rnp = rcu_get_root();
+
+ smp_mb(); // Order against root rcu_node structure grace-period cleanup.
+ if (rgosp->rgos_norm == RCU_GET_STATE_COMPLETED ||
+ rcu_seq_done_exact(&rnp->gp_seq, rgosp->rgos_norm) ||
+ rgosp->rgos_exp == RCU_GET_STATE_COMPLETED ||
+ rcu_seq_done_exact(&rcu_state.expedited_sequence, rgosp->rgos_exp)) {
+ smp_mb(); /* Ensure GP ends before subsequent accesses. */
+ return true;
+ }
+ return false;
+}
+EXPORT_SYMBOL_GPL(poll_state_synchronize_rcu_full);
+
+/**
+ * cond_synchronize_rcu - Conditionally wait for an RCU grace period
+ * @oldstate: value from get_state_synchronize_rcu(), start_poll_synchronize_rcu(), or start_poll_synchronize_rcu_expedited()
*
* If a full RCU grace period has elapsed since the earlier call to
- * get_state_synchronize_rcu(), just return. Otherwise, invoke
- * synchronize_rcu() to wait for a full grace period.
+ * get_state_synchronize_rcu() or start_poll_synchronize_rcu(), just return.
+ * Otherwise, invoke synchronize_rcu() to wait for a full grace period.
*
- * Yes, this function does not take counter wrap into account. But
- * counter wrap is harmless. If the counter wraps, we have waited for
+ * Yes, this function does not take counter wrap into account.
+ * But counter wrap is harmless. If the counter wraps, we have waited for
* more than 2 billion grace periods (and way more on a 64-bit system!),
- * so waiting for one additional grace period should be just fine.
+ * so waiting for a couple of additional grace periods should be just fine.
+ *
+ * This function provides the same memory-ordering guarantees that
+ * would be provided by a synchronize_rcu() that was invoked at the call
+ * to the function that provided @oldstate and that returned at the end
+ * of this function.
*/
void cond_synchronize_rcu(unsigned long oldstate)
{
- if (!rcu_seq_done(&rcu_state.gp_seq, oldstate))
+ if (!poll_state_synchronize_rcu(oldstate))
synchronize_rcu();
- else
- smp_mb(); /* Ensure GP ends before subsequent accesses. */
}
EXPORT_SYMBOL_GPL(cond_synchronize_rcu);
+/**
+ * cond_synchronize_rcu_full - Conditionally wait for an RCU grace period
+ * @rgosp: value from get_state_synchronize_rcu_full(), start_poll_synchronize_rcu_full(), or start_poll_synchronize_rcu_expedited_full()
+ *
+ * If a full RCU grace period has elapsed since the call to
+ * get_state_synchronize_rcu_full(), start_poll_synchronize_rcu_full(),
+ * or start_poll_synchronize_rcu_expedited_full() from which @rgosp was
+ * obtained, just return. Otherwise, invoke synchronize_rcu() to wait
+ * for a full grace period.
+ *
+ * Yes, this function does not take counter wrap into account.
+ * But counter wrap is harmless. If the counter wraps, we have waited for
+ * more than 2 billion grace periods (and way more on a 64-bit system!),
+ * so waiting for a couple of additional grace periods should be just fine.
+ *
+ * This function provides the same memory-ordering guarantees that
+ * would be provided by a synchronize_rcu() that was invoked at the call
+ * to the function that provided @rgosp and that returned at the end of
+ * this function.
+ */
+void cond_synchronize_rcu_full(struct rcu_gp_oldstate *rgosp)
+{
+ if (!poll_state_synchronize_rcu_full(rgosp))
+ synchronize_rcu();
+}
+EXPORT_SYMBOL_GPL(cond_synchronize_rcu_full);
+
/*
* Check to see if there is any immediate RCU-related work to be done by
* the current CPU, returning 1 if so and zero otherwise. The checks are
@@ -3026,11 +3819,13 @@ static int rcu_pending(int user)
struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
struct rcu_node *rnp = rdp->mynode;
+ lockdep_assert_irqs_disabled();
+
/* Check for CPU stalls, if enabled. */
check_cpu_stall(rdp);
/* Does this CPU need a deferred NOCB wakeup? */
- if (rcu_nocb_need_deferred_wakeup(rdp))
+ if (rcu_nocb_need_deferred_wakeup(rdp, RCU_NOCB_WAKE))
return 1;
/* Is this a nohz_full CPU in userspace or idle? (Ignore RCU if so.) */
@@ -3043,13 +3838,13 @@ static int rcu_pending(int user)
return 1;
/* Does this CPU have callbacks ready to invoke? */
- if (rcu_segcblist_ready_cbs(&rdp->cblist))
+ if (!rcu_rdp_is_offloaded(rdp) &&
+ rcu_segcblist_ready_cbs(&rdp->cblist))
return 1;
/* Has RCU gone idle with this CPU needing another grace period? */
if (!gp_in_progress && rcu_segcblist_is_enabled(&rdp->cblist) &&
- (!IS_ENABLED(CONFIG_RCU_NOCB_CPU) ||
- !rcu_segcblist_is_offloaded(&rdp->cblist)) &&
+ !rcu_rdp_is_offloaded(rdp) &&
!rcu_segcblist_restempty(&rdp->cblist, RCU_NEXT_READY_TAIL))
return 1;
@@ -3075,25 +3870,36 @@ static void rcu_barrier_trace(const char *s, int cpu, unsigned long done)
/*
* RCU callback function for rcu_barrier(). If we are last, wake
* up the task executing rcu_barrier().
+ *
+ * Note that the value of rcu_state.barrier_sequence must be captured
+ * before the atomic_dec_and_test(). Otherwise, if this CPU is not last,
+ * other CPUs might count the value down to zero before this CPU gets
+ * around to invoking rcu_barrier_trace(), which might result in bogus
+ * data from the next instance of rcu_barrier().
*/
static void rcu_barrier_callback(struct rcu_head *rhp)
{
+ unsigned long __maybe_unused s = rcu_state.barrier_sequence;
+
if (atomic_dec_and_test(&rcu_state.barrier_cpu_count)) {
- rcu_barrier_trace(TPS("LastCB"), -1,
- rcu_state.barrier_sequence);
+ rcu_barrier_trace(TPS("LastCB"), -1, s);
complete(&rcu_state.barrier_completion);
} else {
- rcu_barrier_trace(TPS("CB"), -1, rcu_state.barrier_sequence);
+ rcu_barrier_trace(TPS("CB"), -1, s);
}
}
/*
- * Called with preemption disabled, and from cross-cpu IRQ context.
+ * If needed, entrain an rcu_barrier() callback on rdp->cblist.
*/
-static void rcu_barrier_func(void *unused)
+static void rcu_barrier_entrain(struct rcu_data *rdp)
{
- struct rcu_data *rdp = raw_cpu_ptr(&rcu_data);
+ unsigned long gseq = READ_ONCE(rcu_state.barrier_sequence);
+ unsigned long lseq = READ_ONCE(rdp->barrier_seq_snap);
+ lockdep_assert_held(&rcu_state.barrier_lock);
+ if (rcu_seq_state(lseq) || !rcu_seq_state(gseq) || rcu_seq_ctr(lseq) != rcu_seq_ctr(gseq))
+ return;
rcu_barrier_trace(TPS("IRQ"), -1, rcu_state.barrier_sequence);
rdp->barrier_head.func = rcu_barrier_callback;
debug_rcu_head_queue(&rdp->barrier_head);
@@ -3103,10 +3909,26 @@ static void rcu_barrier_func(void *unused)
atomic_inc(&rcu_state.barrier_cpu_count);
} else {
debug_rcu_head_unqueue(&rdp->barrier_head);
- rcu_barrier_trace(TPS("IRQNQ"), -1,
- rcu_state.barrier_sequence);
+ rcu_barrier_trace(TPS("IRQNQ"), -1, rcu_state.barrier_sequence);
}
rcu_nocb_unlock(rdp);
+ smp_store_release(&rdp->barrier_seq_snap, gseq);
+}
+
+/*
+ * Called with preemption disabled, and from cross-cpu IRQ context.
+ */
+static void rcu_barrier_handler(void *cpu_in)
+{
+ uintptr_t cpu = (uintptr_t)cpu_in;
+ struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
+
+ lockdep_assert_irqs_disabled();
+ WARN_ON_ONCE(cpu != rdp->cpu);
+ WARN_ON_ONCE(cpu != smp_processor_id());
+ raw_spin_lock(&rcu_state.barrier_lock);
+ rcu_barrier_entrain(rdp);
+ raw_spin_unlock(&rcu_state.barrier_lock);
}
/**
@@ -3119,7 +3941,9 @@ static void rcu_barrier_func(void *unused)
*/
void rcu_barrier(void)
{
- int cpu;
+ uintptr_t cpu;
+ unsigned long flags;
+ unsigned long gseq;
struct rcu_data *rdp;
unsigned long s = rcu_seq_snap(&rcu_state.barrier_sequence);
@@ -3130,26 +3954,28 @@ void rcu_barrier(void)
/* Did someone else do our work for us? */
if (rcu_seq_done(&rcu_state.barrier_sequence, s)) {
- rcu_barrier_trace(TPS("EarlyExit"), -1,
- rcu_state.barrier_sequence);
+ rcu_barrier_trace(TPS("EarlyExit"), -1, rcu_state.barrier_sequence);
smp_mb(); /* caller's subsequent code after above check. */
mutex_unlock(&rcu_state.barrier_mutex);
return;
}
/* Mark the start of the barrier operation. */
+ raw_spin_lock_irqsave(&rcu_state.barrier_lock, flags);
rcu_seq_start(&rcu_state.barrier_sequence);
+ gseq = rcu_state.barrier_sequence;
rcu_barrier_trace(TPS("Inc1"), -1, rcu_state.barrier_sequence);
/*
- * Initialize the count to one rather than to zero in order to
- * avoid a too-soon return to zero in case of a short grace period
- * (or preemption of this task). Exclude CPU-hotplug operations
- * to ensure that no offline CPU has callbacks queued.
+ * Initialize the count to two rather than to zero in order
+ * to avoid a too-soon return to zero in case of an immediate
+ * invocation of the just-enqueued callback (or preemption of
+ * this task). Exclude CPU-hotplug operations to ensure that no
+ * offline non-offloaded CPU has callbacks queued.
*/
init_completion(&rcu_state.barrier_completion);
- atomic_set(&rcu_state.barrier_cpu_count, 1);
- get_online_cpus();
+ atomic_set(&rcu_state.barrier_cpu_count, 2);
+ raw_spin_unlock_irqrestore(&rcu_state.barrier_lock, flags);
/*
* Force each CPU with callbacks to register a new callback.
@@ -3158,25 +3984,37 @@ void rcu_barrier(void)
*/
for_each_possible_cpu(cpu) {
rdp = per_cpu_ptr(&rcu_data, cpu);
- if (!cpu_online(cpu) &&
- !rcu_segcblist_is_offloaded(&rdp->cblist))
+retry:
+ if (smp_load_acquire(&rdp->barrier_seq_snap) == gseq)
continue;
- if (rcu_segcblist_n_cbs(&rdp->cblist)) {
- rcu_barrier_trace(TPS("OnlineQ"), cpu,
- rcu_state.barrier_sequence);
- smp_call_function_single(cpu, rcu_barrier_func, NULL, 1);
- } else {
- rcu_barrier_trace(TPS("OnlineNQ"), cpu,
- rcu_state.barrier_sequence);
+ raw_spin_lock_irqsave(&rcu_state.barrier_lock, flags);
+ if (!rcu_segcblist_n_cbs(&rdp->cblist)) {
+ WRITE_ONCE(rdp->barrier_seq_snap, gseq);
+ raw_spin_unlock_irqrestore(&rcu_state.barrier_lock, flags);
+ rcu_barrier_trace(TPS("NQ"), cpu, rcu_state.barrier_sequence);
+ continue;
+ }
+ if (!rcu_rdp_cpu_online(rdp)) {
+ rcu_barrier_entrain(rdp);
+ WARN_ON_ONCE(READ_ONCE(rdp->barrier_seq_snap) != gseq);
+ raw_spin_unlock_irqrestore(&rcu_state.barrier_lock, flags);
+ rcu_barrier_trace(TPS("OfflineNoCBQ"), cpu, rcu_state.barrier_sequence);
+ continue;
+ }
+ raw_spin_unlock_irqrestore(&rcu_state.barrier_lock, flags);
+ if (smp_call_function_single(cpu, rcu_barrier_handler, (void *)cpu, 1)) {
+ schedule_timeout_uninterruptible(1);
+ goto retry;
}
+ WARN_ON_ONCE(READ_ONCE(rdp->barrier_seq_snap) != gseq);
+ rcu_barrier_trace(TPS("OnlineQ"), cpu, rcu_state.barrier_sequence);
}
- put_online_cpus();
/*
* Now that we have an rcu_barrier_callback() callback on each
* CPU, and thus each counted, remove the initial count.
*/
- if (atomic_dec_and_test(&rcu_state.barrier_cpu_count))
+ if (atomic_sub_and_test(2, &rcu_state.barrier_cpu_count))
complete(&rcu_state.barrier_completion);
/* Wait for all rcu_barrier_callback() callbacks to be invoked. */
@@ -3185,6 +4023,12 @@ void rcu_barrier(void)
/* Mark the end of the barrier operation. */
rcu_barrier_trace(TPS("Inc2"), -1, rcu_state.barrier_sequence);
rcu_seq_end(&rcu_state.barrier_sequence);
+ gseq = rcu_state.barrier_sequence;
+ for_each_possible_cpu(cpu) {
+ rdp = per_cpu_ptr(&rcu_data, cpu);
+
+ WRITE_ONCE(rdp->barrier_seq_snap, gseq);
+ }
/* Other rcu_barrier() invocations can now safely proceed. */
mutex_unlock(&rcu_state.barrier_mutex);
@@ -3194,7 +4038,7 @@ EXPORT_SYMBOL_GPL(rcu_barrier);
/*
* Propagate ->qsinitmask bits up the rcu_node tree to account for the
* first CPU in a given leaf rcu_node structure coming online. The caller
- * must hold the corresponding leaf rcu_node ->lock with interrrupts
+ * must hold the corresponding leaf rcu_node ->lock with interrupts
* disabled.
*/
static void rcu_init_new_rnp(struct rcu_node *rnp_leaf)
@@ -3225,16 +4069,20 @@ static void rcu_init_new_rnp(struct rcu_node *rnp_leaf)
static void __init
rcu_boot_init_percpu_data(int cpu)
{
+ struct context_tracking *ct = this_cpu_ptr(&context_tracking);
struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
/* Set up local state, ensuring consistent view of global state. */
rdp->grpmask = leaf_node_cpu_bit(rdp->mynode, cpu);
- WARN_ON_ONCE(rdp->dynticks_nesting != 1);
- WARN_ON_ONCE(rcu_dynticks_in_eqs(rcu_dynticks_snap(rdp)));
+ INIT_WORK(&rdp->strict_work, strict_work_handler);
+ WARN_ON_ONCE(ct->dynticks_nesting != 1);
+ WARN_ON_ONCE(rcu_dynticks_in_eqs(rcu_dynticks_snap(cpu)));
+ rdp->barrier_seq_snap = rcu_state.barrier_sequence;
rdp->rcu_ofl_gp_seq = rcu_state.gp_seq;
rdp->rcu_ofl_gp_flags = RCU_GP_CLEANED;
rdp->rcu_onl_gp_seq = rcu_state.gp_seq;
rdp->rcu_onl_gp_flags = RCU_GP_CLEANED;
+ rdp->last_sched_clock = jiffies;
rdp->cpu = cpu;
rcu_boot_init_nocb_percpu_data(rdp);
}
@@ -3252,22 +4100,26 @@ rcu_boot_init_percpu_data(int cpu)
int rcutree_prepare_cpu(unsigned int cpu)
{
unsigned long flags;
+ struct context_tracking *ct = per_cpu_ptr(&context_tracking, cpu);
struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
struct rcu_node *rnp = rcu_get_root();
/* Set up local state, ensuring consistent view of global state. */
raw_spin_lock_irqsave_rcu_node(rnp, flags);
rdp->qlen_last_fqs_check = 0;
- rdp->n_force_qs_snap = rcu_state.n_force_qs;
+ rdp->n_force_qs_snap = READ_ONCE(rcu_state.n_force_qs);
rdp->blimit = blimit;
- if (rcu_segcblist_empty(&rdp->cblist) && /* No early-boot CBs? */
- !rcu_segcblist_is_offloaded(&rdp->cblist))
- rcu_segcblist_init(&rdp->cblist); /* Re-enable callbacks. */
- rdp->dynticks_nesting = 1; /* CPU not up, no tearing. */
- rcu_dynticks_eqs_online();
+ ct->dynticks_nesting = 1; /* CPU not up, no tearing. */
raw_spin_unlock_rcu_node(rnp); /* irqs remain disabled. */
/*
+ * Only non-NOCB CPUs that didn't have early-boot callbacks need to be
+ * (re-)initialized.
+ */
+ if (!rcu_segcblist_is_enabled(&rdp->cblist))
+ rcu_segcblist_init(&rdp->cblist); /* Re-enable callbacks. */
+
+ /*
* Add CPU to leaf rcu_node pending-online bitmask. Any needed
* propagation up the rcu_node tree will happen at the beginning
* of the next grace period.
@@ -3275,16 +4127,18 @@ int rcutree_prepare_cpu(unsigned int cpu)
rnp = rdp->mynode;
raw_spin_lock_rcu_node(rnp); /* irqs already disabled. */
rdp->beenonline = true; /* We have now been online. */
- rdp->gp_seq = rnp->gp_seq;
- rdp->gp_seq_needed = rnp->gp_seq;
+ rdp->gp_seq = READ_ONCE(rnp->gp_seq);
+ rdp->gp_seq_needed = rdp->gp_seq;
rdp->cpu_no_qs.b.norm = true;
rdp->core_needs_qs = false;
rdp->rcu_iw_pending = false;
- rdp->rcu_iw_gp_seq = rnp->gp_seq - 1;
+ rdp->rcu_iw = IRQ_WORK_INIT_HARD(rcu_iw_handler);
+ rdp->rcu_iw_gp_seq = rdp->gp_seq - 1;
trace_rcu_grace_period(rcu_state.name, rdp->gp_seq, TPS("cpuonl"));
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
- rcu_prepare_kthreads(cpu);
+ rcu_spawn_one_boost_kthread(rnp);
rcu_spawn_cpu_nocb_kthread(cpu);
+ WRITE_ONCE(rcu_state.n_online_cpus, rcu_state.n_online_cpus + 1);
return 0;
}
@@ -3347,8 +4201,6 @@ int rcutree_offline_cpu(unsigned int cpu)
return 0;
}
-static DEFINE_PER_CPU(int, rcu_cpu_started);
-
/*
* Mark the specified CPU as being online so that subsequent grace periods
* (both expedited and normal) will wait on it. Note that this means that
@@ -3364,41 +4216,50 @@ void rcu_cpu_starting(unsigned int cpu)
{
unsigned long flags;
unsigned long mask;
- int nbits;
- unsigned long oldmask;
struct rcu_data *rdp;
struct rcu_node *rnp;
+ bool newcpu;
- if (per_cpu(rcu_cpu_started, cpu))
+ rdp = per_cpu_ptr(&rcu_data, cpu);
+ if (rdp->cpu_started)
return;
+ rdp->cpu_started = true;
- per_cpu(rcu_cpu_started, cpu) = 1;
-
- rdp = per_cpu_ptr(&rcu_data, cpu);
rnp = rdp->mynode;
mask = rdp->grpmask;
- raw_spin_lock_irqsave_rcu_node(rnp, flags);
- rnp->qsmaskinitnext |= mask;
- oldmask = rnp->expmaskinitnext;
+ local_irq_save(flags);
+ arch_spin_lock(&rcu_state.ofl_lock);
+ rcu_dynticks_eqs_online();
+ raw_spin_lock(&rcu_state.barrier_lock);
+ raw_spin_lock_rcu_node(rnp);
+ WRITE_ONCE(rnp->qsmaskinitnext, rnp->qsmaskinitnext | mask);
+ raw_spin_unlock(&rcu_state.barrier_lock);
+ newcpu = !(rnp->expmaskinitnext & mask);
rnp->expmaskinitnext |= mask;
- oldmask ^= rnp->expmaskinitnext;
- nbits = bitmap_weight(&oldmask, BITS_PER_LONG);
/* Allow lockless access for expedited grace periods. */
- smp_store_release(&rcu_state.ncpus, rcu_state.ncpus + nbits); /* ^^^ */
+ smp_store_release(&rcu_state.ncpus, rcu_state.ncpus + newcpu); /* ^^^ */
+ ASSERT_EXCLUSIVE_WRITER(rcu_state.ncpus);
rcu_gpnum_ovf(rnp, rdp); /* Offline-induced counter wrap? */
rdp->rcu_onl_gp_seq = READ_ONCE(rcu_state.gp_seq);
rdp->rcu_onl_gp_flags = READ_ONCE(rcu_state.gp_flags);
- if (rnp->qsmask & mask) { /* RCU waiting on incoming CPU? */
+
+ /* An incoming CPU should never be blocking a grace period. */
+ if (WARN_ON_ONCE(rnp->qsmask & mask)) { /* RCU waiting on incoming CPU? */
+ /* rcu_report_qs_rnp() *really* wants some flags to restore */
+ unsigned long flags2;
+
+ local_irq_save(flags2);
rcu_disable_urgency_upon_qs(rdp);
/* Report QS -after- changing ->qsmaskinitnext! */
- rcu_report_qs_rnp(mask, rnp, rnp->gp_seq, flags);
+ rcu_report_qs_rnp(mask, rnp, rnp->gp_seq, flags2);
} else {
- raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
+ raw_spin_unlock_rcu_node(rnp);
}
+ arch_spin_unlock(&rcu_state.ofl_lock);
+ local_irq_restore(flags);
smp_mb(); /* Ensure RCU read-side usage follows above initialization. */
}
-#ifdef CONFIG_HOTPLUG_CPU
/*
* The outgoing function has no further need of RCU, so remove it from
* the rcu_node tree's ->qsmaskinitnext bit masks.
@@ -3409,35 +4270,40 @@ void rcu_cpu_starting(unsigned int cpu)
*/
void rcu_report_dead(unsigned int cpu)
{
- unsigned long flags;
+ unsigned long flags, seq_flags;
unsigned long mask;
struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
struct rcu_node *rnp = rdp->mynode; /* Outgoing CPU's rdp & rnp. */
+ // Do any dangling deferred wakeups.
+ do_nocb_deferred_wakeup(rdp);
+
/* QS for any half-done expedited grace period. */
- preempt_disable();
- rcu_report_exp_rdp(this_cpu_ptr(&rcu_data));
- preempt_enable();
+ rcu_report_exp_rdp(rdp);
rcu_preempt_deferred_qs(current);
/* Remove outgoing CPU from mask in the leaf rcu_node structure. */
mask = rdp->grpmask;
- raw_spin_lock(&rcu_state.ofl_lock);
+ local_irq_save(seq_flags);
+ arch_spin_lock(&rcu_state.ofl_lock);
raw_spin_lock_irqsave_rcu_node(rnp, flags); /* Enforce GP memory-order guarantee. */
rdp->rcu_ofl_gp_seq = READ_ONCE(rcu_state.gp_seq);
rdp->rcu_ofl_gp_flags = READ_ONCE(rcu_state.gp_flags);
if (rnp->qsmask & mask) { /* RCU waiting on outgoing CPU? */
/* Report quiescent state -before- changing ->qsmaskinitnext! */
+ rcu_disable_urgency_upon_qs(rdp);
rcu_report_qs_rnp(mask, rnp, rnp->gp_seq, flags);
raw_spin_lock_irqsave_rcu_node(rnp, flags);
}
- rnp->qsmaskinitnext &= ~mask;
+ WRITE_ONCE(rnp->qsmaskinitnext, rnp->qsmaskinitnext & ~mask);
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
- raw_spin_unlock(&rcu_state.ofl_lock);
+ arch_spin_unlock(&rcu_state.ofl_lock);
+ local_irq_restore(seq_flags);
- per_cpu(rcu_cpu_started, cpu) = 0;
+ rdp->cpu_started = false;
}
+#ifdef CONFIG_HOTPLUG_CPU
/*
* The outgoing CPU has just passed through the dying-idle state, and we
* are being invoked from the CPU that was IPIed to continue the offline
@@ -3451,11 +4317,13 @@ void rcutree_migrate_callbacks(int cpu)
struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
bool needwake;
- if (rcu_segcblist_is_offloaded(&rdp->cblist) ||
+ if (rcu_rdp_is_offloaded(rdp) ||
rcu_segcblist_empty(&rdp->cblist))
return; /* No callbacks to migrate. */
- local_irq_save(flags);
+ raw_spin_lock_irqsave(&rcu_state.barrier_lock, flags);
+ WARN_ON_ONCE(rcu_rdp_cpu_online(rdp));
+ rcu_barrier_entrain(rdp);
my_rdp = this_cpu_ptr(&rcu_data);
my_rnp = my_rdp->mynode;
rcu_nocb_lock(my_rdp); /* irqs already disabled. */
@@ -3465,11 +4333,12 @@ void rcutree_migrate_callbacks(int cpu)
needwake = rcu_advance_cbs(my_rnp, rdp) ||
rcu_advance_cbs(my_rnp, my_rdp);
rcu_segcblist_merge(&my_rdp->cblist, &rdp->cblist);
+ raw_spin_unlock(&rcu_state.barrier_lock); /* irqs remain disabled. */
needwake = needwake || rcu_advance_cbs(my_rnp, my_rdp);
rcu_segcblist_disable(&rdp->cblist);
- WARN_ON_ONCE(rcu_segcblist_empty(&my_rdp->cblist) !=
- !rcu_segcblist_n_cbs(&my_rdp->cblist));
- if (rcu_segcblist_is_offloaded(&my_rdp->cblist)) {
+ WARN_ON_ONCE(rcu_segcblist_empty(&my_rdp->cblist) != !rcu_segcblist_n_cbs(&my_rdp->cblist));
+ check_cb_ovld_locked(my_rdp, my_rnp);
+ if (rcu_rdp_is_offloaded(my_rdp)) {
raw_spin_unlock_rcu_node(my_rnp); /* irqs remain disabled. */
__call_rcu_nocb_wake(my_rdp, true, flags);
} else {
@@ -3509,31 +4378,61 @@ static int rcu_pm_notify(struct notifier_block *self,
return NOTIFY_OK;
}
+#ifdef CONFIG_RCU_EXP_KTHREAD
+struct kthread_worker *rcu_exp_gp_kworker;
+struct kthread_worker *rcu_exp_par_gp_kworker;
+
+static void __init rcu_start_exp_gp_kworkers(void)
+{
+ const char *par_gp_kworker_name = "rcu_exp_par_gp_kthread_worker";
+ const char *gp_kworker_name = "rcu_exp_gp_kthread_worker";
+ struct sched_param param = { .sched_priority = kthread_prio };
+
+ rcu_exp_gp_kworker = kthread_create_worker(0, gp_kworker_name);
+ if (IS_ERR_OR_NULL(rcu_exp_gp_kworker)) {
+ pr_err("Failed to create %s!\n", gp_kworker_name);
+ return;
+ }
+
+ rcu_exp_par_gp_kworker = kthread_create_worker(0, par_gp_kworker_name);
+ if (IS_ERR_OR_NULL(rcu_exp_par_gp_kworker)) {
+ pr_err("Failed to create %s!\n", par_gp_kworker_name);
+ kthread_destroy_worker(rcu_exp_gp_kworker);
+ return;
+ }
+
+ sched_setscheduler_nocheck(rcu_exp_gp_kworker->task, SCHED_FIFO, &param);
+ sched_setscheduler_nocheck(rcu_exp_par_gp_kworker->task, SCHED_FIFO,
+ &param);
+}
+
+static inline void rcu_alloc_par_gp_wq(void)
+{
+}
+#else /* !CONFIG_RCU_EXP_KTHREAD */
+struct workqueue_struct *rcu_par_gp_wq;
+
+static void __init rcu_start_exp_gp_kworkers(void)
+{
+}
+
+static inline void rcu_alloc_par_gp_wq(void)
+{
+ rcu_par_gp_wq = alloc_workqueue("rcu_par_gp", WQ_MEM_RECLAIM, 0);
+ WARN_ON(!rcu_par_gp_wq);
+}
+#endif /* CONFIG_RCU_EXP_KTHREAD */
+
/*
* Spawn the kthreads that handle RCU's grace periods.
*/
static int __init rcu_spawn_gp_kthread(void)
{
unsigned long flags;
- int kthread_prio_in = kthread_prio;
struct rcu_node *rnp;
struct sched_param sp;
struct task_struct *t;
-
- /* Force priority into range. */
- if (IS_ENABLED(CONFIG_RCU_BOOST) && kthread_prio < 2
- && IS_BUILTIN(CONFIG_RCU_TORTURE_TEST))
- kthread_prio = 2;
- else if (IS_ENABLED(CONFIG_RCU_BOOST) && kthread_prio < 1)
- kthread_prio = 1;
- else if (kthread_prio < 0)
- kthread_prio = 0;
- else if (kthread_prio > 99)
- kthread_prio = 99;
-
- if (kthread_prio != kthread_prio_in)
- pr_alert("rcu_spawn_gp_kthread(): Limited prio to %d from %d\n",
- kthread_prio, kthread_prio_in);
+ struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
rcu_scheduler_fully_active = 1;
t = kthread_create(rcu_gp_kthread, NULL, "%s", rcu_state.name);
@@ -3545,11 +4444,23 @@ static int __init rcu_spawn_gp_kthread(void)
}
rnp = rcu_get_root();
raw_spin_lock_irqsave_rcu_node(rnp, flags);
- rcu_state.gp_kthread = t;
+ WRITE_ONCE(rcu_state.gp_activity, jiffies);
+ WRITE_ONCE(rcu_state.gp_req_activity, jiffies);
+ // Reset .gp_activity and .gp_req_activity before setting .gp_kthread.
+ smp_store_release(&rcu_state.gp_kthread, t); /* ^^^ */
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
wake_up_process(t);
- rcu_spawn_nocb_kthreads();
- rcu_spawn_boost_kthreads();
+ /* This is a pre-SMP initcall, we expect a single CPU */
+ WARN_ON(num_online_cpus() > 1);
+ /*
+ * Those kthreads couldn't be created on rcu_init() -> rcutree_prepare_cpu()
+ * due to rcu_scheduler_fully_active.
+ */
+ rcu_spawn_cpu_nocb_kthread(smp_processor_id());
+ rcu_spawn_one_boost_kthread(rdp->mynode);
+ rcu_spawn_core_kthreads();
+ /* Create kthread worker for expedited GPs */
+ rcu_start_exp_gp_kworkers();
return 0;
}
early_initcall(rcu_spawn_gp_kthread);
@@ -3566,9 +4477,20 @@ early_initcall(rcu_spawn_gp_kthread);
*/
void rcu_scheduler_starting(void)
{
+ unsigned long flags;
+ struct rcu_node *rnp;
+
WARN_ON(num_online_cpus() != 1);
WARN_ON(nr_context_switches() > 0);
rcu_test_sync_prims();
+
+ // Fix up the ->gp_seq counters.
+ local_irq_save(flags);
+ rcu_for_each_node_breadth_first(rnp)
+ rnp->gp_seq_needed = rnp->gp_seq = rcu_state.gp_seq;
+ local_irq_restore(flags);
+
+ // Switch out of early boot mode.
rcu_scheduler_active = RCU_SCHEDULER_INIT;
rcu_test_sync_prims();
}
@@ -3641,6 +4563,10 @@ static void __init rcu_init_one(void)
init_waitqueue_head(&rnp->exp_wq[2]);
init_waitqueue_head(&rnp->exp_wq[3]);
spin_lock_init(&rnp->exp_lock);
+ mutex_init(&rnp->boost_kthread_mutex);
+ raw_spin_lock_init(&rnp->exp_poll_lock);
+ rnp->exp_seq_poll_rq = RCU_GET_STATE_COMPLETED;
+ INIT_WORK(&rnp->exp_poll_wq, sync_rcu_do_polled_gp);
}
}
@@ -3656,15 +4582,51 @@ static void __init rcu_init_one(void)
}
/*
+ * Force priority from the kernel command-line into range.
+ */
+static void __init sanitize_kthread_prio(void)
+{
+ int kthread_prio_in = kthread_prio;
+
+ if (IS_ENABLED(CONFIG_RCU_BOOST) && kthread_prio < 2
+ && IS_BUILTIN(CONFIG_RCU_TORTURE_TEST))
+ kthread_prio = 2;
+ else if (IS_ENABLED(CONFIG_RCU_BOOST) && kthread_prio < 1)
+ kthread_prio = 1;
+ else if (kthread_prio < 0)
+ kthread_prio = 0;
+ else if (kthread_prio > 99)
+ kthread_prio = 99;
+
+ if (kthread_prio != kthread_prio_in)
+ pr_alert("%s: Limited prio to %d from %d\n",
+ __func__, kthread_prio, kthread_prio_in);
+}
+
+/*
* Compute the rcu_node tree geometry from kernel parameters. This cannot
* replace the definitions in tree.h because those are needed to size
* the ->node array in the rcu_state structure.
*/
-static void __init rcu_init_geometry(void)
+void rcu_init_geometry(void)
{
ulong d;
int i;
+ static unsigned long old_nr_cpu_ids;
int rcu_capacity[RCU_NUM_LVLS];
+ static bool initialized;
+
+ if (initialized) {
+ /*
+ * Warn if setup_nr_cpu_ids() had not yet been invoked,
+ * unless nr_cpus_ids == NR_CPUS, in which case who cares?
+ */
+ WARN_ON_ONCE(old_nr_cpu_ids != nr_cpu_ids);
+ return;
+ }
+
+ old_nr_cpu_ids = nr_cpu_ids;
+ initialized = true;
/*
* Initialize any unspecified boot parameters.
@@ -3758,32 +4720,49 @@ static void __init rcu_dump_rcu_node_tree(void)
}
struct workqueue_struct *rcu_gp_wq;
-struct workqueue_struct *rcu_par_gp_wq;
static void __init kfree_rcu_batch_init(void)
{
int cpu;
int i;
+ /* Clamp it to [0:100] seconds interval. */
+ if (rcu_delay_page_cache_fill_msec < 0 ||
+ rcu_delay_page_cache_fill_msec > 100 * MSEC_PER_SEC) {
+
+ rcu_delay_page_cache_fill_msec =
+ clamp(rcu_delay_page_cache_fill_msec, 0,
+ (int) (100 * MSEC_PER_SEC));
+
+ pr_info("Adjusting rcutree.rcu_delay_page_cache_fill_msec to %d ms.\n",
+ rcu_delay_page_cache_fill_msec);
+ }
+
for_each_possible_cpu(cpu) {
struct kfree_rcu_cpu *krcp = per_cpu_ptr(&krc, cpu);
- spin_lock_init(&krcp->lock);
- for (i = 0; i < KFREE_N_BATCHES; i++)
+ for (i = 0; i < KFREE_N_BATCHES; i++) {
+ INIT_RCU_WORK(&krcp->krw_arr[i].rcu_work, kfree_rcu_work);
krcp->krw_arr[i].krcp = krcp;
+ }
+
INIT_DELAYED_WORK(&krcp->monitor_work, kfree_rcu_monitor);
+ INIT_DELAYED_WORK(&krcp->page_cache_work, fill_page_cache_func);
krcp->initialized = true;
}
+ if (register_shrinker(&kfree_rcu_shrinker, "rcu-kfree"))
+ pr_err("Failed to register kfree_rcu() shrinker!\n");
}
void __init rcu_init(void)
{
- int cpu;
+ int cpu = smp_processor_id();
rcu_early_boot_tests();
kfree_rcu_batch_init();
rcu_bootup_announce();
+ sanitize_kthread_prio();
rcu_init_geometry();
rcu_init_one();
if (dump_tree)
@@ -3797,20 +4776,29 @@ void __init rcu_init(void)
* or the scheduler are operational.
*/
pm_notifier(rcu_pm_notify, 0);
- for_each_online_cpu(cpu) {
- rcutree_prepare_cpu(cpu);
- rcu_cpu_starting(cpu);
- rcutree_online_cpu(cpu);
- }
+ WARN_ON(num_online_cpus() > 1); // Only one CPU this early in boot.
+ rcutree_prepare_cpu(cpu);
+ rcu_cpu_starting(cpu);
+ rcutree_online_cpu(cpu);
- /* Create workqueue for expedited GPs and for Tree SRCU. */
+ /* Create workqueue for Tree SRCU and for expedited GPs. */
rcu_gp_wq = alloc_workqueue("rcu_gp", WQ_MEM_RECLAIM, 0);
WARN_ON(!rcu_gp_wq);
- rcu_par_gp_wq = alloc_workqueue("rcu_par_gp", WQ_MEM_RECLAIM, 0);
- WARN_ON(!rcu_par_gp_wq);
- srcu_init();
+ rcu_alloc_par_gp_wq();
+
+ /* Fill in default value for rcutree.qovld boot parameter. */
+ /* -After- the rcu_node ->lock fields are initialized! */
+ if (qovld < 0)
+ qovld_calc = DEFAULT_RCU_QOVLD_MULT * qhimark;
+ else
+ qovld_calc = qovld;
+
+ // Kick-start any polled grace periods that started early.
+ if (!(per_cpu_ptr(&rcu_data, cpu)->mynode->exp_seq_poll_rq & 0x1))
+ (void)start_poll_synchronize_rcu_expedited();
}
#include "tree_stall.h"
#include "tree_exp.h"
+#include "tree_nocb.h"
#include "tree_plugin.h"
diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
index 0c87e4c161c2..d4a97e40ea9c 100644
--- a/kernel/rcu/tree.h
+++ b/kernel/rcu/tree.h
@@ -10,6 +10,7 @@
*/
#include <linux/cache.h>
+#include <linux/kthread.h>
#include <linux/spinlock.h>
#include <linux/rtmutex.h>
#include <linux/threads.h>
@@ -23,7 +24,11 @@
/* Communicate arguments to a workqueue handler. */
struct rcu_exp_work {
unsigned long rew_s;
+#ifdef CONFIG_RCU_EXP_KTHREAD
+ struct kthread_work rew_work;
+#else
struct work_struct rew_work;
+#endif /* CONFIG_RCU_EXP_KTHREAD */
};
/* RCU's kthread states for tracing. */
@@ -41,7 +46,7 @@ struct rcu_node {
raw_spinlock_t __private lock; /* Root rcu_node's lock protects */
/* some rcu_state fields as well as */
/* following. */
- unsigned long gp_seq; /* Track rsp->rcu_gp_seq. */
+ unsigned long gp_seq; /* Track rsp->gp_seq. */
unsigned long gp_seq_needed; /* Track furthest future GP request. */
unsigned long completedqs; /* All QSes done for this node. */
unsigned long qsmask; /* CPUs or groups that need to switch in */
@@ -56,7 +61,6 @@ struct rcu_node {
/* Initialized from ->qsmaskinitnext at the */
/* beginning of each grace period. */
unsigned long qsmaskinitnext;
- /* Online CPUs for next grace period. */
unsigned long expmask; /* CPUs or groups that need to check in */
/* to allow the current expedited GP */
/* to complete. */
@@ -68,12 +72,14 @@ struct rcu_node {
/* Online CPUs for next expedited GP. */
/* Any CPU that has ever been online will */
/* have its bit set. */
+ unsigned long cbovldmask;
+ /* CPUs experiencing callback overload. */
unsigned long ffmask; /* Fully functional CPUs. */
unsigned long grpmask; /* Mask to apply to parent qsmask. */
/* Only one bit will be set in this mask. */
- int grplo; /* lowest-numbered CPU or group here. */
- int grphi; /* highest-numbered CPU or group here. */
- u8 grpnum; /* CPU/group number for next level up. */
+ int grplo; /* lowest-numbered CPU here. */
+ int grphi; /* highest-numbered CPU here. */
+ u8 grpnum; /* group number for next level up. */
u8 level; /* root is at level 0. */
bool wait_blkd_tasks;/* Necessary to wait for blocked tasks to */
/* exit RCU read-side critical sections */
@@ -107,11 +113,15 @@ struct rcu_node {
/* side effect, not as a lock. */
unsigned long boost_time;
/* When to start boosting (jiffies). */
+ struct mutex boost_kthread_mutex;
+ /* Exclusion for thread spawning and affinity */
+ /* manipulation. */
struct task_struct *boost_kthread_task;
/* kthread that takes care of priority */
/* boosting for this rcu_node structure. */
unsigned int boost_kthread_status;
/* State of boost_kthread_task for tracing. */
+ unsigned long n_boosts; /* Number of boosts for this rcu_node structure. */
#ifdef CONFIG_RCU_NOCB_CPU
struct swait_queue_head nocb_gp_wq[2];
/* Place for rcu_nocb_kthread() to wait GP. */
@@ -123,6 +133,10 @@ struct rcu_node {
wait_queue_head_t exp_wq[4];
struct rcu_exp_work rew;
bool exp_need_flush; /* Need to flush workitem? */
+ raw_spinlock_t exp_poll_lock;
+ /* Lock and data for polled expedited grace periods. */
+ unsigned long exp_seq_poll_rq;
+ struct work_struct exp_poll_wq;
} ____cacheline_internodealigned_in_smp;
/*
@@ -147,13 +161,13 @@ union rcu_noqs {
/* Per-CPU data for read-copy update. */
struct rcu_data {
/* 1) quiescent-state and grace-period handling : */
- unsigned long gp_seq; /* Track rsp->rcu_gp_seq counter. */
+ unsigned long gp_seq; /* Track rsp->gp_seq counter. */
unsigned long gp_seq_needed; /* Track furthest future GP request. */
union rcu_noqs cpu_no_qs; /* No QSes yet for this CPU. */
- bool core_needs_qs; /* Core waits for quiesc state. */
+ bool core_needs_qs; /* Core waits for quiescent state. */
bool beenonline; /* CPU online at least once. */
bool gpwrap; /* Possible ->gp_seq wrap. */
- bool exp_deferred_qs; /* This CPU awaiting a deferred QS? */
+ bool cpu_started; /* RCU watching this onlining CPU. */
struct rcu_node *mynode; /* This CPU's leaf of hierarchy */
unsigned long grpmask; /* Mask to apply to leaf qsmask. */
unsigned long ticks_this_gp; /* The number of scheduling-clock */
@@ -162,6 +176,7 @@ struct rcu_data {
/* period it is aware of. */
struct irq_work defer_qs_iw; /* Obtain later scheduler attention. */
bool defer_qs_iw_pending; /* Scheduler attention pending? */
+ struct work_struct strict_work; /* Schedule readers for strict GPs. */
/* 2) batch handling */
struct rcu_segcblist cblist; /* Segmented callback list, with */
@@ -169,38 +184,35 @@ struct rcu_data {
/* different grace periods. */
long qlen_last_fqs_check;
/* qlen at last check for QS forcing */
+ unsigned long n_cbs_invoked; /* # callbacks invoked since boot. */
unsigned long n_force_qs_snap;
/* did other CPU force QS recently? */
long blimit; /* Upper limit on a processed batch */
/* 3) dynticks interface. */
int dynticks_snap; /* Per-GP tracking for dynticks. */
- long dynticks_nesting; /* Track process nesting level. */
- long dynticks_nmi_nesting; /* Track irq/NMI nesting level. */
- atomic_t dynticks; /* Even value for idle, else odd. */
bool rcu_need_heavy_qs; /* GP old, so heavy quiescent state! */
bool rcu_urgent_qs; /* GP old need light quiescent state. */
bool rcu_forced_tick; /* Forced tick to provide QS. */
bool rcu_forced_tick_exp; /* ... provide QS to expedited GP. */
-#ifdef CONFIG_RCU_FAST_NO_HZ
- unsigned long last_accelerate; /* Last jiffy CBs were accelerated. */
- unsigned long last_advance_all; /* Last jiffy CBs were all advanced. */
- int tick_nohz_enabled_snap; /* Previously seen value from sysfs. */
-#endif /* #ifdef CONFIG_RCU_FAST_NO_HZ */
/* 4) rcu_barrier(), OOM callbacks, and expediting. */
+ unsigned long barrier_seq_snap; /* Snap of rcu_state.barrier_sequence. */
struct rcu_head barrier_head;
int exp_dynticks_snap; /* Double-check need for IPI. */
/* 5) Callback offloading. */
#ifdef CONFIG_RCU_NOCB_CPU
struct swait_queue_head nocb_cb_wq; /* For nocb kthreads to sleep on. */
+ struct swait_queue_head nocb_state_wq; /* For offloading state changes */
struct task_struct *nocb_gp_kthread;
raw_spinlock_t nocb_lock; /* Guard following pair of fields. */
atomic_t nocb_lock_contended; /* Contention experienced. */
int nocb_defer_wakeup; /* Defer wakeup of nocb_kthread. */
struct timer_list nocb_timer; /* Enforce finite deferral. */
unsigned long nocb_gp_adv_time; /* Last call_rcu() CB adv (jiffies). */
+ struct mutex nocb_gp_kthread_mutex; /* Exclusion for nocb gp kthread */
+ /* spawning */
/* The following fields are used by call_rcu, hence own cacheline. */
raw_spinlock_t nocb_bypass_lock ____cacheline_internodealigned_in_smp;
@@ -211,7 +223,6 @@ struct rcu_data {
/* The following fields are used by GP kthread, hence own cacheline. */
raw_spinlock_t nocb_gp_lock ____cacheline_internodealigned_in_smp;
- struct timer_list nocb_bypass_timer; /* Force nocb_bypass flush. */
u8 nocb_gp_sleep; /* Is the nocb GP thread asleep? */
u8 nocb_gp_bypass; /* Found a bypass on last scan? */
u8 nocb_gp_gp; /* GP to wait for on last scan? */
@@ -220,8 +231,12 @@ struct rcu_data {
struct swait_queue_head nocb_gp_wq; /* For nocb kthreads to sleep on. */
bool nocb_cb_sleep; /* Is the nocb CB thread asleep? */
struct task_struct *nocb_cb_kthread;
- struct rcu_data *nocb_next_cb_rdp;
- /* Next rcu_data in wakeup chain. */
+ struct list_head nocb_head_rdp; /*
+ * Head of rcu_data list in wakeup chain,
+ * if rdp_gp.
+ */
+ struct list_head nocb_entry_rdp; /* rcu_data node in wakeup chain. */
+ struct rcu_data *nocb_toggling_rdp; /* rdp queued for (de-)offloading */
/* The following fields are used by CB kthread, hence new cacheline. */
struct rcu_data *nocb_gp_rdp ____cacheline_internodealigned_in_smp;
@@ -233,6 +248,7 @@ struct rcu_data {
/* rcuc per-CPU kthread or NULL. */
unsigned int rcu_cpu_kthread_status;
char rcu_cpu_has_work;
+ unsigned long rcuc_activity;
/* 7) Diagnostic data, including RCU CPU stall warnings. */
unsigned int softirq_snap; /* Snapshot of softirq activity. */
@@ -245,14 +261,16 @@ struct rcu_data {
unsigned long rcu_onl_gp_seq; /* ->gp_seq at last online. */
short rcu_onl_gp_flags; /* ->gp_flags at last online. */
unsigned long last_fqs_resched; /* Time of last rcu_resched(). */
+ unsigned long last_sched_clock; /* Jiffies of last rcu_sched_clock_irq(). */
int cpu;
};
/* Values for nocb_defer_wakeup field in struct rcu_data. */
#define RCU_NOCB_WAKE_NOT 0
-#define RCU_NOCB_WAKE 1
-#define RCU_NOCB_WAKE_FORCE 2
+#define RCU_NOCB_WAKE_BYPASS 1
+#define RCU_NOCB_WAKE 2
+#define RCU_NOCB_WAKE_FORCE 3
#define RCU_JIFFIES_TILL_FORCE_QS (1 + (HZ > 250) + (HZ > 500))
/* For jiffies_till_first_fqs and */
@@ -293,18 +311,23 @@ struct rcu_state {
/* Hierarchy levels (+1 to */
/* shut bogus gcc warning) */
int ncpus; /* # CPUs seen so far. */
+ int n_online_cpus; /* # CPUs online for RCU. */
/* The following fields are guarded by the root rcu_node's lock. */
- u8 boost ____cacheline_internodealigned_in_smp;
- /* Subject to priority boost. */
- unsigned long gp_seq; /* Grace-period sequence #. */
+ unsigned long gp_seq ____cacheline_internodealigned_in_smp;
+ /* Grace-period sequence #. */
+ unsigned long gp_max; /* Maximum GP duration in */
+ /* jiffies. */
struct task_struct *gp_kthread; /* Task for grace periods. */
struct swait_queue_head gp_wq; /* Where GP task waits. */
short gp_flags; /* Commands for GP task. */
short gp_state; /* GP kthread sleep state. */
unsigned long gp_wake_time; /* Last GP kthread wake. */
unsigned long gp_wake_seq; /* ->gp_seq at ^^^. */
+ unsigned long gp_seq_polled; /* GP seq for polled API. */
+ unsigned long gp_seq_polled_snap; /* ->gp_seq_polled at normal GP start. */
+ unsigned long gp_seq_polled_exp_snap; /* ->gp_seq_polled at expedited GP start. */
/* End of fields guarded by root rcu_node's lock. */
@@ -315,12 +338,16 @@ struct rcu_state {
/* rcu_barrier(). */
/* End of fields guarded by barrier_mutex. */
+ raw_spinlock_t barrier_lock; /* Protects ->barrier_seq_snap. */
+
struct mutex exp_mutex; /* Serialize expedited GP. */
struct mutex exp_wake_mutex; /* Serialize wakeup. */
unsigned long expedited_sequence; /* Take a ticket. */
atomic_t expedited_need_qs; /* # CPUs left to check in. */
struct swait_queue_head expedited_wq; /* Wait for check-ins. */
int ncpus_snap; /* # CPUs seen last time. */
+ u8 cbovld; /* Callback overload now? */
+ u8 cbovldnext; /* ^ ^ next time? */
unsigned long jiffies_force_qs; /* Time at which to invoke */
/* force_quiescent_state(). */
@@ -342,19 +369,19 @@ struct rcu_state {
/* a reluctant CPU. */
unsigned long n_force_qs_gpstart; /* Snapshot of n_force_qs at */
/* GP start. */
- unsigned long gp_max; /* Maximum GP duration in */
- /* jiffies. */
const char *name; /* Name of structure. */
char abbr; /* Abbreviated name. */
- raw_spinlock_t ofl_lock ____cacheline_internodealigned_in_smp;
+ arch_spinlock_t ofl_lock ____cacheline_internodealigned_in_smp;
/* Synchronize offline with */
/* GP pre-initialization. */
+ int nocb_is_setup; /* nocb is setup from boot */
};
/* Values for rcu_state structure's gp_flags field. */
#define RCU_GP_FLAG_INIT 0x1 /* Need grace-period initialization. */
#define RCU_GP_FLAG_FQS 0x2 /* Need grace-period quiescent-state forcing. */
+#define RCU_GP_FLAG_OVLD 0x4 /* Experiencing callback overload. */
/* Values for rcu_state structure's gp_state field. */
#define RCU_GP_IDLE 0 /* Initial state and no GP in progress. */
@@ -403,15 +430,11 @@ static void rcu_flavor_sched_clock_irq(int user);
static void dump_blkd_tasks(struct rcu_node *rnp, int ncheck);
static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags);
static void rcu_preempt_boost_start_gp(struct rcu_node *rnp);
-static bool rcu_is_callbacks_kthread(void);
+static bool rcu_is_callbacks_kthread(struct rcu_data *rdp);
static void rcu_cpu_kthread_setup(unsigned int cpu);
-static void __init rcu_spawn_boost_kthreads(void);
-static void rcu_prepare_kthreads(int cpu);
-static void rcu_cleanup_after_idle(void);
-static void rcu_prepare_for_idle(void);
+static void rcu_spawn_one_boost_kthread(struct rcu_node *rnp);
static bool rcu_preempt_has_tasks(struct rcu_node *rnp);
static bool rcu_preempt_need_deferred_qs(struct task_struct *t);
-static void rcu_preempt_deferred_qs(struct task_struct *t);
static void zero_cpu_stall_ticks(struct rcu_data *rdp);
static struct swait_queue_head *rcu_nocb_gp_get(struct rcu_node *rnp);
static void rcu_nocb_gp_cleanup(struct swait_queue_head *sq);
@@ -422,11 +445,10 @@ static bool rcu_nocb_try_bypass(struct rcu_data *rdp, struct rcu_head *rhp,
bool *was_alldone, unsigned long flags);
static void __call_rcu_nocb_wake(struct rcu_data *rdp, bool was_empty,
unsigned long flags);
-static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp);
-static void do_nocb_deferred_wakeup(struct rcu_data *rdp);
+static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp, int level);
+static bool do_nocb_deferred_wakeup(struct rcu_data *rdp);
static void rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp);
static void rcu_spawn_cpu_nocb_kthread(int cpu);
-static void __init rcu_spawn_nocb_kthreads(void);
static void show_rcu_nocb_state(struct rcu_data *rdp);
static void rcu_nocb_lock(struct rcu_data *rdp);
static void rcu_nocb_unlock(struct rcu_data *rdp);
@@ -435,12 +457,16 @@ static void rcu_nocb_unlock_irqrestore(struct rcu_data *rdp,
static void rcu_lockdep_assert_cblist_protected(struct rcu_data *rdp);
#ifdef CONFIG_RCU_NOCB_CPU
static void __init rcu_organize_nocb_kthreads(void);
-#define rcu_nocb_lock_irqsave(rdp, flags) \
-do { \
- if (!rcu_segcblist_is_offloaded(&(rdp)->cblist)) \
- local_irq_save(flags); \
- else \
- raw_spin_lock_irqsave(&(rdp)->nocb_lock, (flags)); \
+
+/*
+ * Disable IRQs before checking offloaded state so that local
+ * locking is safe against concurrent de-offloading.
+ */
+#define rcu_nocb_lock_irqsave(rdp, flags) \
+do { \
+ local_irq_save(flags); \
+ if (rcu_segcblist_is_offloaded(&(rdp)->cblist)) \
+ raw_spin_lock(&(rdp)->nocb_lock); \
} while (0)
#else /* #ifdef CONFIG_RCU_NOCB_CPU */
#define rcu_nocb_lock_irqsave(rdp, flags) local_irq_save(flags)
@@ -448,8 +474,6 @@ do { \
static void rcu_bind_gp_kthread(void);
static bool rcu_nohz_full_cpu(void);
-static void rcu_dynticks_task_enter(void);
-static void rcu_dynticks_task_exit(void);
/* Forward declarations for tree_stall.h */
static void record_gp_stall_check_time(void);
@@ -457,3 +481,6 @@ static void rcu_iw_handler(struct irq_work *iwp);
static void check_cpu_stall(struct rcu_data *rdp);
static void rcu_check_gp_start_stall(struct rcu_node *rnp, struct rcu_data *rdp,
const unsigned long gpssdelay);
+
+/* Forward declarations for tree_exp.h. */
+static void sync_rcu_do_polled_gp(struct work_struct *wp);
diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h
index dcbd75791f39..18e9b4cd78ef 100644
--- a/kernel/rcu/tree_exp.h
+++ b/kernel/rcu/tree_exp.h
@@ -18,6 +18,7 @@ static int rcu_print_task_exp_stall(struct rcu_node *rnp);
static void rcu_exp_gp_seq_start(void)
{
rcu_seq_start(&rcu_state.expedited_sequence);
+ rcu_poll_gp_seq_start_unlocked(&rcu_state.gp_seq_polled_exp_snap);
}
/*
@@ -34,6 +35,7 @@ static __maybe_unused unsigned long rcu_exp_gp_seq_endval(void)
*/
static void rcu_exp_gp_seq_end(void)
{
+ rcu_poll_gp_seq_end_unlocked(&rcu_state.gp_seq_polled_exp_snap);
rcu_seq_end(&rcu_state.expedited_sequence);
smp_mb(); /* Ensure that consecutive grace periods serialize. */
}
@@ -150,7 +152,7 @@ static void __maybe_unused sync_exp_reset_tree(void)
static bool sync_rcu_exp_done(struct rcu_node *rnp)
{
raw_lockdep_assert_held_rcu_node(rnp);
- return rnp->exp_tasks == NULL &&
+ return READ_ONCE(rnp->exp_tasks) == NULL &&
READ_ONCE(rnp->expmask) == 0;
}
@@ -255,7 +257,7 @@ static void rcu_report_exp_cpu_mult(struct rcu_node *rnp,
*/
static void rcu_report_exp_rdp(struct rcu_data *rdp)
{
- WRITE_ONCE(rdp->exp_deferred_qs, false);
+ WRITE_ONCE(rdp->cpu_no_qs.b.exp, false);
rcu_report_exp_cpu_mult(rdp->mynode, rdp->grpmask, true);
}
@@ -314,7 +316,7 @@ static bool exp_funnel_lock(unsigned long s)
sync_exp_work_done(s));
return true;
}
- rnp->exp_seq_rq = s; /* Followers can wait on us. */
+ WRITE_ONCE(rnp->exp_seq_rq, s); /* Followers can wait on us. */
spin_unlock(&rnp->exp_lock);
trace_rcu_exp_funnel_lock(rcu_state.name, rnp->level,
rnp->grplo, rnp->grphi, TPS("nxtlvl"));
@@ -334,15 +336,13 @@ fastpath:
* Select the CPUs within the specified rcu_node that the upcoming
* expedited grace period needs to wait for.
*/
-static void sync_rcu_exp_select_node_cpus(struct work_struct *wp)
+static void __sync_rcu_exp_select_node_cpus(struct rcu_exp_work *rewp)
{
int cpu;
unsigned long flags;
unsigned long mask_ofl_test;
unsigned long mask_ofl_ipi;
int ret;
- struct rcu_exp_work *rewp =
- container_of(wp, struct rcu_exp_work, rew_work);
struct rcu_node *rnp = container_of(rewp, struct rcu_node, rew);
raw_spin_lock_irqsave_rcu_node(rnp, flags);
@@ -358,7 +358,7 @@ static void sync_rcu_exp_select_node_cpus(struct work_struct *wp)
!(rnp->qsmaskinitnext & mask)) {
mask_ofl_test |= mask;
} else {
- snap = rcu_dynticks_snap(rdp);
+ snap = rcu_dynticks_snap(cpu);
if (rcu_dynticks_in_eqs(snap))
mask_ofl_test |= mask;
else
@@ -373,7 +373,7 @@ static void sync_rcu_exp_select_node_cpus(struct work_struct *wp)
* until such time as the ->expmask bits are cleared.
*/
if (rcu_preempt_has_tasks(rnp))
- rnp->exp_tasks = rnp->blkd_tasks.next;
+ WRITE_ONCE(rnp->exp_tasks, rnp->blkd_tasks.next);
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
/* IPI the remaining CPUs for expedited quiescent state. */
@@ -387,6 +387,7 @@ retry_ipi:
continue;
}
if (get_cpu() == cpu) {
+ mask_ofl_test |= mask;
put_cpu();
continue;
}
@@ -403,7 +404,7 @@ retry_ipi:
/* Online, so delay for a bit and try again. */
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
trace_rcu_exp_grace_period(rcu_state.name, rcu_exp_gp_seq_endval(), TPS("selectofl"));
- schedule_timeout_uninterruptible(1);
+ schedule_timeout_idle(1);
goto retry_ipi;
}
/* CPU really is offline, so we must report its QS. */
@@ -416,13 +417,119 @@ retry_ipi:
rcu_report_exp_cpu_mult(rnp, mask_ofl_test, false);
}
+static void rcu_exp_sel_wait_wake(unsigned long s);
+
+#ifdef CONFIG_RCU_EXP_KTHREAD
+static void sync_rcu_exp_select_node_cpus(struct kthread_work *wp)
+{
+ struct rcu_exp_work *rewp =
+ container_of(wp, struct rcu_exp_work, rew_work);
+
+ __sync_rcu_exp_select_node_cpus(rewp);
+}
+
+static inline bool rcu_gp_par_worker_started(void)
+{
+ return !!READ_ONCE(rcu_exp_par_gp_kworker);
+}
+
+static inline void sync_rcu_exp_select_cpus_queue_work(struct rcu_node *rnp)
+{
+ kthread_init_work(&rnp->rew.rew_work, sync_rcu_exp_select_node_cpus);
+ /*
+ * Use rcu_exp_par_gp_kworker, because flushing a work item from
+ * another work item on the same kthread worker can result in
+ * deadlock.
+ */
+ kthread_queue_work(rcu_exp_par_gp_kworker, &rnp->rew.rew_work);
+}
+
+static inline void sync_rcu_exp_select_cpus_flush_work(struct rcu_node *rnp)
+{
+ kthread_flush_work(&rnp->rew.rew_work);
+}
+
+/*
+ * Work-queue handler to drive an expedited grace period forward.
+ */
+static void wait_rcu_exp_gp(struct kthread_work *wp)
+{
+ struct rcu_exp_work *rewp;
+
+ rewp = container_of(wp, struct rcu_exp_work, rew_work);
+ rcu_exp_sel_wait_wake(rewp->rew_s);
+}
+
+static inline void synchronize_rcu_expedited_queue_work(struct rcu_exp_work *rew)
+{
+ kthread_init_work(&rew->rew_work, wait_rcu_exp_gp);
+ kthread_queue_work(rcu_exp_gp_kworker, &rew->rew_work);
+}
+
+static inline void synchronize_rcu_expedited_destroy_work(struct rcu_exp_work *rew)
+{
+}
+#else /* !CONFIG_RCU_EXP_KTHREAD */
+static void sync_rcu_exp_select_node_cpus(struct work_struct *wp)
+{
+ struct rcu_exp_work *rewp =
+ container_of(wp, struct rcu_exp_work, rew_work);
+
+ __sync_rcu_exp_select_node_cpus(rewp);
+}
+
+static inline bool rcu_gp_par_worker_started(void)
+{
+ return !!READ_ONCE(rcu_par_gp_wq);
+}
+
+static inline void sync_rcu_exp_select_cpus_queue_work(struct rcu_node *rnp)
+{
+ int cpu = find_next_bit(&rnp->ffmask, BITS_PER_LONG, -1);
+
+ INIT_WORK(&rnp->rew.rew_work, sync_rcu_exp_select_node_cpus);
+ /* If all offline, queue the work on an unbound CPU. */
+ if (unlikely(cpu > rnp->grphi - rnp->grplo))
+ cpu = WORK_CPU_UNBOUND;
+ else
+ cpu += rnp->grplo;
+ queue_work_on(cpu, rcu_par_gp_wq, &rnp->rew.rew_work);
+}
+
+static inline void sync_rcu_exp_select_cpus_flush_work(struct rcu_node *rnp)
+{
+ flush_work(&rnp->rew.rew_work);
+}
+
+/*
+ * Work-queue handler to drive an expedited grace period forward.
+ */
+static void wait_rcu_exp_gp(struct work_struct *wp)
+{
+ struct rcu_exp_work *rewp;
+
+ rewp = container_of(wp, struct rcu_exp_work, rew_work);
+ rcu_exp_sel_wait_wake(rewp->rew_s);
+}
+
+static inline void synchronize_rcu_expedited_queue_work(struct rcu_exp_work *rew)
+{
+ INIT_WORK_ONSTACK(&rew->rew_work, wait_rcu_exp_gp);
+ queue_work(rcu_gp_wq, &rew->rew_work);
+}
+
+static inline void synchronize_rcu_expedited_destroy_work(struct rcu_exp_work *rew)
+{
+ destroy_work_on_stack(&rew->rew_work);
+}
+#endif /* CONFIG_RCU_EXP_KTHREAD */
+
/*
* Select the nodes that the upcoming expedited grace period needs
* to wait for.
*/
static void sync_rcu_exp_select_cpus(void)
{
- int cpu;
struct rcu_node *rnp;
trace_rcu_exp_grace_period(rcu_state.name, rcu_exp_gp_seq_endval(), TPS("reset"));
@@ -434,28 +541,21 @@ static void sync_rcu_exp_select_cpus(void)
rnp->exp_need_flush = false;
if (!READ_ONCE(rnp->expmask))
continue; /* Avoid early boot non-existent wq. */
- if (!READ_ONCE(rcu_par_gp_wq) ||
+ if (!rcu_gp_par_worker_started() ||
rcu_scheduler_active != RCU_SCHEDULER_RUNNING ||
rcu_is_last_leaf_node(rnp)) {
- /* No workqueues yet or last leaf, do direct call. */
+ /* No worker started yet or last leaf, do direct call. */
sync_rcu_exp_select_node_cpus(&rnp->rew.rew_work);
continue;
}
- INIT_WORK(&rnp->rew.rew_work, sync_rcu_exp_select_node_cpus);
- cpu = find_next_bit(&rnp->ffmask, BITS_PER_LONG, -1);
- /* If all offline, queue the work on an unbound CPU. */
- if (unlikely(cpu > rnp->grphi - rnp->grplo))
- cpu = WORK_CPU_UNBOUND;
- else
- cpu += rnp->grplo;
- queue_work_on(cpu, rcu_par_gp_wq, &rnp->rew.rew_work);
+ sync_rcu_exp_select_cpus_queue_work(rnp);
rnp->exp_need_flush = true;
}
- /* Wait for workqueue jobs (if any) to complete. */
+ /* Wait for jobs (if any) to complete. */
rcu_for_each_leaf_node(rnp)
if (rnp->exp_need_flush)
- flush_work(&rnp->rew.rew_work);
+ sync_rcu_exp_select_cpus_flush_work(rnp);
}
/*
@@ -485,6 +585,7 @@ static bool synchronize_rcu_expedited_wait_once(long tlimit)
static void synchronize_rcu_expedited_wait(void)
{
int cpu;
+ unsigned long j;
unsigned long jiffies_stall;
unsigned long jiffies_start;
unsigned long mask;
@@ -494,28 +595,35 @@ static void synchronize_rcu_expedited_wait(void)
struct rcu_node *rnp_root = rcu_get_root();
trace_rcu_exp_grace_period(rcu_state.name, rcu_exp_gp_seq_endval(), TPS("startwait"));
- jiffies_stall = rcu_jiffies_till_stall_check();
+ jiffies_stall = rcu_exp_jiffies_till_stall_check();
jiffies_start = jiffies;
- if (IS_ENABLED(CONFIG_NO_HZ_FULL)) {
+ if (tick_nohz_full_enabled() && rcu_inkernel_boot_has_ended()) {
if (synchronize_rcu_expedited_wait_once(1))
return;
rcu_for_each_leaf_node(rnp) {
- for_each_leaf_node_cpu_mask(rnp, cpu, rnp->expmask) {
+ mask = READ_ONCE(rnp->expmask);
+ for_each_leaf_node_cpu_mask(rnp, cpu, mask) {
rdp = per_cpu_ptr(&rcu_data, cpu);
if (rdp->rcu_forced_tick_exp)
continue;
rdp->rcu_forced_tick_exp = true;
- tick_dep_set_cpu(cpu, TICK_DEP_BIT_RCU_EXP);
+ preempt_disable();
+ if (cpu_online(cpu))
+ tick_dep_set_cpu(cpu, TICK_DEP_BIT_RCU_EXP);
+ preempt_enable();
}
}
+ j = READ_ONCE(jiffies_till_first_fqs);
+ if (synchronize_rcu_expedited_wait_once(j + HZ))
+ return;
}
for (;;) {
if (synchronize_rcu_expedited_wait_once(jiffies_stall))
return;
- if (rcu_cpu_stall_suppress)
+ if (rcu_stall_is_suppressed())
continue;
- panic_on_rcu_stall();
+ trace_rcu_stall_warning(rcu_state.name, TPS("ExpeditedStall"));
pr_err("INFO: %s detected expedited stalls on CPUs/tasks: {",
rcu_state.name);
ndetected = 0;
@@ -529,18 +637,19 @@ static void synchronize_rcu_expedited_wait(void)
continue;
ndetected++;
rdp = per_cpu_ptr(&rcu_data, cpu);
- pr_cont(" %d-%c%c%c", cpu,
+ pr_cont(" %d-%c%c%c%c", cpu,
"O."[!!cpu_online(cpu)],
"o."[!!(rdp->grpmask & rnp->expmaskinit)],
- "N."[!!(rdp->grpmask & rnp->expmaskinitnext)]);
+ "N."[!!(rdp->grpmask & rnp->expmaskinitnext)],
+ "D."[!!(rdp->cpu_no_qs.b.exp)]);
}
}
pr_cont(" } %lu jiffies s: %lu root: %#lx/%c\n",
jiffies - jiffies_start, rcu_state.expedited_sequence,
- READ_ONCE(rnp_root->expmask),
- ".T"[!!rnp_root->exp_tasks]);
+ data_race(rnp_root->expmask),
+ ".T"[!!data_race(rnp_root->exp_tasks)]);
if (ndetected) {
- pr_err("blocking rcu_node structures:");
+ pr_err("blocking rcu_node structures (internal RCU debug):");
rcu_for_each_node_breadth_first(rnp) {
if (rnp == rnp_root)
continue; /* printed unconditionally */
@@ -548,8 +657,8 @@ static void synchronize_rcu_expedited_wait(void)
continue;
pr_cont(" l=%u:%d-%d:%#lx/%c",
rnp->level, rnp->grplo, rnp->grphi,
- READ_ONCE(rnp->expmask),
- ".T"[!!rnp->exp_tasks]);
+ data_race(rnp->expmask),
+ ".T"[!!data_race(rnp->exp_tasks)]);
}
pr_cont("\n");
}
@@ -561,7 +670,8 @@ static void synchronize_rcu_expedited_wait(void)
dump_cpu_task(cpu);
}
}
- jiffies_stall = 3 * rcu_jiffies_till_stall_check() + 3;
+ jiffies_stall = 3 * rcu_exp_jiffies_till_stall_check() + 3;
+ panic_on_rcu_stall();
}
}
@@ -589,7 +699,7 @@ static void rcu_exp_wait_wake(unsigned long s)
spin_lock(&rnp->exp_lock);
/* Recheck, avoid hang in case someone just arrived. */
if (ULONG_CMP_LT(rnp->exp_seq_rq, s))
- rnp->exp_seq_rq = s;
+ WRITE_ONCE(rnp->exp_seq_rq, s);
spin_unlock(&rnp->exp_lock);
}
smp_mb(); /* All above changes before wakeup. */
@@ -612,17 +722,6 @@ static void rcu_exp_sel_wait_wake(unsigned long s)
rcu_exp_wait_wake(s);
}
-/*
- * Work-queue handler to drive an expedited grace period forward.
- */
-static void wait_rcu_exp_gp(struct work_struct *wp)
-{
- struct rcu_exp_work *rewp;
-
- rewp = container_of(wp, struct rcu_exp_work, rew_work);
- rcu_exp_sel_wait_wake(rewp->rew_s);
-}
-
#ifdef CONFIG_PREEMPT_RCU
/*
@@ -634,6 +733,7 @@ static void wait_rcu_exp_gp(struct work_struct *wp)
*/
static void rcu_exp_handler(void *unused)
{
+ int depth = rcu_preempt_depth();
unsigned long flags;
struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
struct rcu_node *rnp = rdp->mynode;
@@ -644,12 +744,12 @@ static void rcu_exp_handler(void *unused)
* critical section. If also enabled or idle, immediately
* report the quiescent state, otherwise defer.
*/
- if (!rcu_preempt_depth()) {
+ if (!depth) {
if (!(preempt_count() & (PREEMPT_MASK | SOFTIRQ_MASK)) ||
- rcu_dynticks_curr_cpu_in_eqs()) {
+ rcu_is_cpu_rrupt_from_idle()) {
rcu_report_exp_rdp(rdp);
} else {
- rdp->exp_deferred_qs = true;
+ WRITE_ONCE(rdp->cpu_no_qs.b.exp, true);
set_tsk_need_resched(t);
set_preempt_need_resched();
}
@@ -668,40 +768,18 @@ static void rcu_exp_handler(void *unused)
* can have caused this quiescent state to already have been
* reported, so we really do need to check ->expmask.
*/
- if (rcu_preempt_depth() > 0) {
+ if (depth > 0) {
raw_spin_lock_irqsave_rcu_node(rnp, flags);
if (rnp->expmask & rdp->grpmask) {
- rdp->exp_deferred_qs = true;
+ WRITE_ONCE(rdp->cpu_no_qs.b.exp, true);
t->rcu_read_unlock_special.b.exp_hint = true;
}
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
return;
}
- /*
- * The final and least likely case is where the interrupted
- * code was just about to or just finished exiting the RCU-preempt
- * read-side critical section, and no, we can't tell which.
- * So either way, set ->deferred_qs to flag later code that
- * a quiescent state is required.
- *
- * If the CPU is fully enabled (or if some buggy RCU-preempt
- * read-side critical section is being used from idle), just
- * invoke rcu_preempt_deferred_qs() to immediately report the
- * quiescent state. We cannot use rcu_read_unlock_special()
- * because we are in an interrupt handler, which will cause that
- * function to take an early exit without doing anything.
- *
- * Otherwise, force a context switch after the CPU enables everything.
- */
- rdp->exp_deferred_qs = true;
- if (!(preempt_count() & (PREEMPT_MASK | SOFTIRQ_MASK)) ||
- WARN_ON_ONCE(rcu_dynticks_curr_cpu_in_eqs())) {
- rcu_preempt_deferred_qs(t);
- } else {
- set_tsk_need_resched(t);
- set_preempt_need_resched();
- }
+ // Finally, negative nesting depth should not happen.
+ WARN_ON_ONCE(1);
}
/* PREEMPTION=y, so no PREEMPTION=n expedited grace period to clean up after. */
@@ -716,17 +794,20 @@ static void sync_sched_exp_online_cleanup(int cpu)
*/
static int rcu_print_task_exp_stall(struct rcu_node *rnp)
{
- struct task_struct *t;
+ unsigned long flags;
int ndetected = 0;
+ struct task_struct *t;
- if (!rnp->exp_tasks)
+ if (!READ_ONCE(rnp->exp_tasks))
return 0;
+ raw_spin_lock_irqsave_rcu_node(rnp, flags);
t = list_entry(rnp->exp_tasks->prev,
struct task_struct, rcu_node_entry);
list_for_each_entry_continue(t, &rnp->blkd_tasks, rcu_node_entry) {
pr_cont(" P%d", t->pid);
ndetected++;
}
+ raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
return ndetected;
}
@@ -745,15 +826,15 @@ static void rcu_exp_need_qs(void)
/* Invoked on each online non-idle CPU for expedited quiescent state. */
static void rcu_exp_handler(void *unused)
{
- struct rcu_data *rdp;
- struct rcu_node *rnp;
+ struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
+ struct rcu_node *rnp = rdp->mynode;
+ bool preempt_bh_enabled = !(preempt_count() & (PREEMPT_MASK | SOFTIRQ_MASK));
- rdp = this_cpu_ptr(&rcu_data);
- rnp = rdp->mynode;
if (!(READ_ONCE(rnp->expmask) & rdp->grpmask) ||
__this_cpu_read(rcu_data.cpu_no_qs.b.exp))
return;
- if (rcu_is_cpu_rrupt_from_idle()) {
+ if (rcu_is_cpu_rrupt_from_idle() ||
+ (IS_ENABLED(CONFIG_PREEMPT_COUNT) && preempt_bh_enabled)) {
rcu_report_exp_rdp(this_cpu_ptr(&rcu_data));
return;
}
@@ -774,7 +855,7 @@ static void sync_sched_exp_online_cleanup(int cpu)
my_cpu = get_cpu();
/* Quiescent state either not needed or already requested, leave. */
if (!(READ_ONCE(rnp->expmask) & rdp->grpmask) ||
- __this_cpu_read(rcu_data.cpu_no_qs.b.exp)) {
+ READ_ONCE(rdp->cpu_no_qs.b.exp)) {
put_cpu();
return;
}
@@ -827,6 +908,7 @@ static int rcu_print_task_exp_stall(struct rcu_node *rnp)
void synchronize_rcu_expedited(void)
{
bool boottime = (rcu_scheduler_active == RCU_SCHEDULER_INIT);
+ unsigned long flags;
struct rcu_exp_work rew;
struct rcu_node *rnp;
unsigned long s;
@@ -837,8 +919,21 @@ void synchronize_rcu_expedited(void)
"Illegal synchronize_rcu_expedited() in RCU read-side critical section");
/* Is the state is such that the call is a grace period? */
- if (rcu_blocking_is_gp())
- return;
+ if (rcu_blocking_is_gp()) {
+ // Note well that this code runs with !PREEMPT && !SMP.
+ // In addition, all code that advances grace periods runs
+ // at process level. Therefore, this expedited GP overlaps
+ // with other expedited GPs only by being fully nested within
+ // them, which allows reuse of ->gp_seq_polled_exp_snap.
+ rcu_poll_gp_seq_start_unlocked(&rcu_state.gp_seq_polled_exp_snap);
+ rcu_poll_gp_seq_end_unlocked(&rcu_state.gp_seq_polled_exp_snap);
+
+ local_irq_save(flags);
+ WARN_ON_ONCE(num_online_cpus() > 1);
+ rcu_state.expedited_sequence += (1 << RCU_SEQ_CTR_SHIFT);
+ local_irq_restore(flags);
+ return; // Context allows vacuous grace periods.
+ }
/* If expedited grace periods are prohibited, fall back to normal. */
if (rcu_gp_is_normal()) {
@@ -858,20 +953,154 @@ void synchronize_rcu_expedited(void)
} else {
/* Marshall arguments & schedule the expedited grace period. */
rew.rew_s = s;
- INIT_WORK_ONSTACK(&rew.rew_work, wait_rcu_exp_gp);
- queue_work(rcu_gp_wq, &rew.rew_work);
+ synchronize_rcu_expedited_queue_work(&rew);
}
/* Wait for expedited grace period to complete. */
rnp = rcu_get_root();
wait_event(rnp->exp_wq[rcu_seq_ctr(s) & 0x3],
sync_exp_work_done(s));
- smp_mb(); /* Workqueue actions happen before return. */
+ smp_mb(); /* Work actions happen before return. */
/* Let the next expedited grace period start. */
mutex_unlock(&rcu_state.exp_mutex);
if (likely(!boottime))
- destroy_work_on_stack(&rew.rew_work);
+ synchronize_rcu_expedited_destroy_work(&rew);
}
EXPORT_SYMBOL_GPL(synchronize_rcu_expedited);
+
+/*
+ * Ensure that start_poll_synchronize_rcu_expedited() has the expedited
+ * RCU grace periods that it needs.
+ */
+static void sync_rcu_do_polled_gp(struct work_struct *wp)
+{
+ unsigned long flags;
+ int i = 0;
+ struct rcu_node *rnp = container_of(wp, struct rcu_node, exp_poll_wq);
+ unsigned long s;
+
+ raw_spin_lock_irqsave(&rnp->exp_poll_lock, flags);
+ s = rnp->exp_seq_poll_rq;
+ rnp->exp_seq_poll_rq = RCU_GET_STATE_COMPLETED;
+ raw_spin_unlock_irqrestore(&rnp->exp_poll_lock, flags);
+ if (s == RCU_GET_STATE_COMPLETED)
+ return;
+ while (!poll_state_synchronize_rcu(s)) {
+ synchronize_rcu_expedited();
+ if (i == 10 || i == 20)
+ pr_info("%s: i = %d s = %lx gp_seq_polled = %lx\n", __func__, i, s, READ_ONCE(rcu_state.gp_seq_polled));
+ i++;
+ }
+ raw_spin_lock_irqsave(&rnp->exp_poll_lock, flags);
+ s = rnp->exp_seq_poll_rq;
+ if (poll_state_synchronize_rcu(s))
+ rnp->exp_seq_poll_rq = RCU_GET_STATE_COMPLETED;
+ raw_spin_unlock_irqrestore(&rnp->exp_poll_lock, flags);
+}
+
+/**
+ * start_poll_synchronize_rcu_expedited - Snapshot current RCU state and start expedited grace period
+ *
+ * Returns a cookie to pass to a call to cond_synchronize_rcu(),
+ * cond_synchronize_rcu_expedited(), or poll_state_synchronize_rcu(),
+ * allowing them to determine whether or not any sort of grace period has
+ * elapsed in the meantime. If the needed expedited grace period is not
+ * already slated to start, initiates that grace period.
+ */
+unsigned long start_poll_synchronize_rcu_expedited(void)
+{
+ unsigned long flags;
+ struct rcu_data *rdp;
+ struct rcu_node *rnp;
+ unsigned long s;
+
+ s = get_state_synchronize_rcu();
+ rdp = per_cpu_ptr(&rcu_data, raw_smp_processor_id());
+ rnp = rdp->mynode;
+ if (rcu_init_invoked())
+ raw_spin_lock_irqsave(&rnp->exp_poll_lock, flags);
+ if (!poll_state_synchronize_rcu(s)) {
+ rnp->exp_seq_poll_rq = s;
+ if (rcu_init_invoked())
+ queue_work(rcu_gp_wq, &rnp->exp_poll_wq);
+ }
+ if (rcu_init_invoked())
+ raw_spin_unlock_irqrestore(&rnp->exp_poll_lock, flags);
+
+ return s;
+}
+EXPORT_SYMBOL_GPL(start_poll_synchronize_rcu_expedited);
+
+/**
+ * start_poll_synchronize_rcu_expedited_full - Take a full snapshot and start expedited grace period
+ * @rgosp: Place to put snapshot of grace-period state
+ *
+ * Places the normal and expedited grace-period states in rgosp. This
+ * state value can be passed to a later call to cond_synchronize_rcu_full()
+ * or poll_state_synchronize_rcu_full() to determine whether or not a
+ * grace period (whether normal or expedited) has elapsed in the meantime.
+ * If the needed expedited grace period is not already slated to start,
+ * initiates that grace period.
+ */
+void start_poll_synchronize_rcu_expedited_full(struct rcu_gp_oldstate *rgosp)
+{
+ get_state_synchronize_rcu_full(rgosp);
+ (void)start_poll_synchronize_rcu_expedited();
+}
+EXPORT_SYMBOL_GPL(start_poll_synchronize_rcu_expedited_full);
+
+/**
+ * cond_synchronize_rcu_expedited - Conditionally wait for an expedited RCU grace period
+ *
+ * @oldstate: value from get_state_synchronize_rcu(), start_poll_synchronize_rcu(), or start_poll_synchronize_rcu_expedited()
+ *
+ * If any type of full RCU grace period has elapsed since the earlier
+ * call to get_state_synchronize_rcu(), start_poll_synchronize_rcu(),
+ * or start_poll_synchronize_rcu_expedited(), just return. Otherwise,
+ * invoke synchronize_rcu_expedited() to wait for a full grace period.
+ *
+ * Yes, this function does not take counter wrap into account.
+ * But counter wrap is harmless. If the counter wraps, we have waited for
+ * more than 2 billion grace periods (and way more on a 64-bit system!),
+ * so waiting for a couple of additional grace periods should be just fine.
+ *
+ * This function provides the same memory-ordering guarantees that
+ * would be provided by a synchronize_rcu() that was invoked at the call
+ * to the function that provided @oldstate and that returned at the end
+ * of this function.
+ */
+void cond_synchronize_rcu_expedited(unsigned long oldstate)
+{
+ if (!poll_state_synchronize_rcu(oldstate))
+ synchronize_rcu_expedited();
+}
+EXPORT_SYMBOL_GPL(cond_synchronize_rcu_expedited);
+
+/**
+ * cond_synchronize_rcu_expedited_full - Conditionally wait for an expedited RCU grace period
+ * @rgosp: value from get_state_synchronize_rcu_full(), start_poll_synchronize_rcu_full(), or start_poll_synchronize_rcu_expedited_full()
+ *
+ * If a full RCU grace period has elapsed since the call to
+ * get_state_synchronize_rcu_full(), start_poll_synchronize_rcu_full(),
+ * or start_poll_synchronize_rcu_expedited_full() from which @rgosp was
+ * obtained, just return. Otherwise, invoke synchronize_rcu_expedited()
+ * to wait for a full grace period.
+ *
+ * Yes, this function does not take counter wrap into account.
+ * But counter wrap is harmless. If the counter wraps, we have waited for
+ * more than 2 billion grace periods (and way more on a 64-bit system!),
+ * so waiting for a couple of additional grace periods should be just fine.
+ *
+ * This function provides the same memory-ordering guarantees that
+ * would be provided by a synchronize_rcu() that was invoked at the call
+ * to the function that provided @rgosp and that returned at the end of
+ * this function.
+ */
+void cond_synchronize_rcu_expedited_full(struct rcu_gp_oldstate *rgosp)
+{
+ if (!poll_state_synchronize_rcu_full(rgosp))
+ synchronize_rcu_expedited();
+}
+EXPORT_SYMBOL_GPL(cond_synchronize_rcu_expedited_full);
diff --git a/kernel/rcu/tree_nocb.h b/kernel/rcu/tree_nocb.h
new file mode 100644
index 000000000000..0a5f0ef41484
--- /dev/null
+++ b/kernel/rcu/tree_nocb.h
@@ -0,0 +1,1607 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Read-Copy Update mechanism for mutual exclusion (tree-based version)
+ * Internal non-public definitions that provide either classic
+ * or preemptible semantics.
+ *
+ * Copyright Red Hat, 2009
+ * Copyright IBM Corporation, 2009
+ * Copyright SUSE, 2021
+ *
+ * Author: Ingo Molnar <mingo@elte.hu>
+ * Paul E. McKenney <paulmck@linux.ibm.com>
+ * Frederic Weisbecker <frederic@kernel.org>
+ */
+
+#ifdef CONFIG_RCU_NOCB_CPU
+static cpumask_var_t rcu_nocb_mask; /* CPUs to have callbacks offloaded. */
+static bool __read_mostly rcu_nocb_poll; /* Offload kthread are to poll. */
+static inline int rcu_lockdep_is_held_nocb(struct rcu_data *rdp)
+{
+ return lockdep_is_held(&rdp->nocb_lock);
+}
+
+static inline bool rcu_current_is_nocb_kthread(struct rcu_data *rdp)
+{
+ /* Race on early boot between thread creation and assignment */
+ if (!rdp->nocb_cb_kthread || !rdp->nocb_gp_kthread)
+ return true;
+
+ if (current == rdp->nocb_cb_kthread || current == rdp->nocb_gp_kthread)
+ if (in_task())
+ return true;
+ return false;
+}
+
+/*
+ * Offload callback processing from the boot-time-specified set of CPUs
+ * specified by rcu_nocb_mask. For the CPUs in the set, there are kthreads
+ * created that pull the callbacks from the corresponding CPU, wait for
+ * a grace period to elapse, and invoke the callbacks. These kthreads
+ * are organized into GP kthreads, which manage incoming callbacks, wait for
+ * grace periods, and awaken CB kthreads, and the CB kthreads, which only
+ * invoke callbacks. Each GP kthread invokes its own CBs. The no-CBs CPUs
+ * do a wake_up() on their GP kthread when they insert a callback into any
+ * empty list, unless the rcu_nocb_poll boot parameter has been specified,
+ * in which case each kthread actively polls its CPU. (Which isn't so great
+ * for energy efficiency, but which does reduce RCU's overhead on that CPU.)
+ *
+ * This is intended to be used in conjunction with Frederic Weisbecker's
+ * adaptive-idle work, which would seriously reduce OS jitter on CPUs
+ * running CPU-bound user-mode computations.
+ *
+ * Offloading of callbacks can also be used as an energy-efficiency
+ * measure because CPUs with no RCU callbacks queued are more aggressive
+ * about entering dyntick-idle mode.
+ */
+
+
+/*
+ * Parse the boot-time rcu_nocb_mask CPU list from the kernel parameters.
+ * If the list is invalid, a warning is emitted and all CPUs are offloaded.
+ */
+static int __init rcu_nocb_setup(char *str)
+{
+ alloc_bootmem_cpumask_var(&rcu_nocb_mask);
+ if (*str == '=') {
+ if (cpulist_parse(++str, rcu_nocb_mask)) {
+ pr_warn("rcu_nocbs= bad CPU range, all CPUs set\n");
+ cpumask_setall(rcu_nocb_mask);
+ }
+ }
+ rcu_state.nocb_is_setup = true;
+ return 1;
+}
+__setup("rcu_nocbs", rcu_nocb_setup);
+
+static int __init parse_rcu_nocb_poll(char *arg)
+{
+ rcu_nocb_poll = true;
+ return 0;
+}
+early_param("rcu_nocb_poll", parse_rcu_nocb_poll);
+
+/*
+ * Don't bother bypassing ->cblist if the call_rcu() rate is low.
+ * After all, the main point of bypassing is to avoid lock contention
+ * on ->nocb_lock, which only can happen at high call_rcu() rates.
+ */
+static int nocb_nobypass_lim_per_jiffy = 16 * 1000 / HZ;
+module_param(nocb_nobypass_lim_per_jiffy, int, 0);
+
+/*
+ * Acquire the specified rcu_data structure's ->nocb_bypass_lock. If the
+ * lock isn't immediately available, increment ->nocb_lock_contended to
+ * flag the contention.
+ */
+static void rcu_nocb_bypass_lock(struct rcu_data *rdp)
+ __acquires(&rdp->nocb_bypass_lock)
+{
+ lockdep_assert_irqs_disabled();
+ if (raw_spin_trylock(&rdp->nocb_bypass_lock))
+ return;
+ atomic_inc(&rdp->nocb_lock_contended);
+ WARN_ON_ONCE(smp_processor_id() != rdp->cpu);
+ smp_mb__after_atomic(); /* atomic_inc() before lock. */
+ raw_spin_lock(&rdp->nocb_bypass_lock);
+ smp_mb__before_atomic(); /* atomic_dec() after lock. */
+ atomic_dec(&rdp->nocb_lock_contended);
+}
+
+/*
+ * Spinwait until the specified rcu_data structure's ->nocb_lock is
+ * not contended. Please note that this is extremely special-purpose,
+ * relying on the fact that at most two kthreads and one CPU contend for
+ * this lock, and also that the two kthreads are guaranteed to have frequent
+ * grace-period-duration time intervals between successive acquisitions
+ * of the lock. This allows us to use an extremely simple throttling
+ * mechanism, and further to apply it only to the CPU doing floods of
+ * call_rcu() invocations. Don't try this at home!
+ */
+static void rcu_nocb_wait_contended(struct rcu_data *rdp)
+{
+ WARN_ON_ONCE(smp_processor_id() != rdp->cpu);
+ while (WARN_ON_ONCE(atomic_read(&rdp->nocb_lock_contended)))
+ cpu_relax();
+}
+
+/*
+ * Conditionally acquire the specified rcu_data structure's
+ * ->nocb_bypass_lock.
+ */
+static bool rcu_nocb_bypass_trylock(struct rcu_data *rdp)
+{
+ lockdep_assert_irqs_disabled();
+ return raw_spin_trylock(&rdp->nocb_bypass_lock);
+}
+
+/*
+ * Release the specified rcu_data structure's ->nocb_bypass_lock.
+ */
+static void rcu_nocb_bypass_unlock(struct rcu_data *rdp)
+ __releases(&rdp->nocb_bypass_lock)
+{
+ lockdep_assert_irqs_disabled();
+ raw_spin_unlock(&rdp->nocb_bypass_lock);
+}
+
+/*
+ * Acquire the specified rcu_data structure's ->nocb_lock, but only
+ * if it corresponds to a no-CBs CPU.
+ */
+static void rcu_nocb_lock(struct rcu_data *rdp)
+{
+ lockdep_assert_irqs_disabled();
+ if (!rcu_rdp_is_offloaded(rdp))
+ return;
+ raw_spin_lock(&rdp->nocb_lock);
+}
+
+/*
+ * Release the specified rcu_data structure's ->nocb_lock, but only
+ * if it corresponds to a no-CBs CPU.
+ */
+static void rcu_nocb_unlock(struct rcu_data *rdp)
+{
+ if (rcu_rdp_is_offloaded(rdp)) {
+ lockdep_assert_irqs_disabled();
+ raw_spin_unlock(&rdp->nocb_lock);
+ }
+}
+
+/*
+ * Release the specified rcu_data structure's ->nocb_lock and restore
+ * interrupts, but only if it corresponds to a no-CBs CPU.
+ */
+static void rcu_nocb_unlock_irqrestore(struct rcu_data *rdp,
+ unsigned long flags)
+{
+ if (rcu_rdp_is_offloaded(rdp)) {
+ lockdep_assert_irqs_disabled();
+ raw_spin_unlock_irqrestore(&rdp->nocb_lock, flags);
+ } else {
+ local_irq_restore(flags);
+ }
+}
+
+/* Lockdep check that ->cblist may be safely accessed. */
+static void rcu_lockdep_assert_cblist_protected(struct rcu_data *rdp)
+{
+ lockdep_assert_irqs_disabled();
+ if (rcu_rdp_is_offloaded(rdp))
+ lockdep_assert_held(&rdp->nocb_lock);
+}
+
+/*
+ * Wake up any no-CBs CPUs' kthreads that were waiting on the just-ended
+ * grace period.
+ */
+static void rcu_nocb_gp_cleanup(struct swait_queue_head *sq)
+{
+ swake_up_all(sq);
+}
+
+static struct swait_queue_head *rcu_nocb_gp_get(struct rcu_node *rnp)
+{
+ return &rnp->nocb_gp_wq[rcu_seq_ctr(rnp->gp_seq) & 0x1];
+}
+
+static void rcu_init_one_nocb(struct rcu_node *rnp)
+{
+ init_swait_queue_head(&rnp->nocb_gp_wq[0]);
+ init_swait_queue_head(&rnp->nocb_gp_wq[1]);
+}
+
+static bool __wake_nocb_gp(struct rcu_data *rdp_gp,
+ struct rcu_data *rdp,
+ bool force, unsigned long flags)
+ __releases(rdp_gp->nocb_gp_lock)
+{
+ bool needwake = false;
+
+ if (!READ_ONCE(rdp_gp->nocb_gp_kthread)) {
+ raw_spin_unlock_irqrestore(&rdp_gp->nocb_gp_lock, flags);
+ trace_rcu_nocb_wake(rcu_state.name, rdp->cpu,
+ TPS("AlreadyAwake"));
+ return false;
+ }
+
+ if (rdp_gp->nocb_defer_wakeup > RCU_NOCB_WAKE_NOT) {
+ WRITE_ONCE(rdp_gp->nocb_defer_wakeup, RCU_NOCB_WAKE_NOT);
+ del_timer(&rdp_gp->nocb_timer);
+ }
+
+ if (force || READ_ONCE(rdp_gp->nocb_gp_sleep)) {
+ WRITE_ONCE(rdp_gp->nocb_gp_sleep, false);
+ needwake = true;
+ }
+ raw_spin_unlock_irqrestore(&rdp_gp->nocb_gp_lock, flags);
+ if (needwake) {
+ trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("DoWake"));
+ wake_up_process(rdp_gp->nocb_gp_kthread);
+ }
+
+ return needwake;
+}
+
+/*
+ * Kick the GP kthread for this NOCB group.
+ */
+static bool wake_nocb_gp(struct rcu_data *rdp, bool force)
+{
+ unsigned long flags;
+ struct rcu_data *rdp_gp = rdp->nocb_gp_rdp;
+
+ raw_spin_lock_irqsave(&rdp_gp->nocb_gp_lock, flags);
+ return __wake_nocb_gp(rdp_gp, rdp, force, flags);
+}
+
+/*
+ * Arrange to wake the GP kthread for this NOCB group at some future
+ * time when it is safe to do so.
+ */
+static void wake_nocb_gp_defer(struct rcu_data *rdp, int waketype,
+ const char *reason)
+{
+ unsigned long flags;
+ struct rcu_data *rdp_gp = rdp->nocb_gp_rdp;
+
+ raw_spin_lock_irqsave(&rdp_gp->nocb_gp_lock, flags);
+
+ /*
+ * Bypass wakeup overrides previous deferments. In case
+ * of callback storm, no need to wake up too early.
+ */
+ if (waketype == RCU_NOCB_WAKE_BYPASS) {
+ mod_timer(&rdp_gp->nocb_timer, jiffies + 2);
+ WRITE_ONCE(rdp_gp->nocb_defer_wakeup, waketype);
+ } else {
+ if (rdp_gp->nocb_defer_wakeup < RCU_NOCB_WAKE)
+ mod_timer(&rdp_gp->nocb_timer, jiffies + 1);
+ if (rdp_gp->nocb_defer_wakeup < waketype)
+ WRITE_ONCE(rdp_gp->nocb_defer_wakeup, waketype);
+ }
+
+ raw_spin_unlock_irqrestore(&rdp_gp->nocb_gp_lock, flags);
+
+ trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, reason);
+}
+
+/*
+ * Flush the ->nocb_bypass queue into ->cblist, enqueuing rhp if non-NULL.
+ * However, if there is a callback to be enqueued and if ->nocb_bypass
+ * proves to be initially empty, just return false because the no-CB GP
+ * kthread may need to be awakened in this case.
+ *
+ * Note that this function always returns true if rhp is NULL.
+ */
+static bool rcu_nocb_do_flush_bypass(struct rcu_data *rdp, struct rcu_head *rhp,
+ unsigned long j)
+{
+ struct rcu_cblist rcl;
+
+ WARN_ON_ONCE(!rcu_rdp_is_offloaded(rdp));
+ rcu_lockdep_assert_cblist_protected(rdp);
+ lockdep_assert_held(&rdp->nocb_bypass_lock);
+ if (rhp && !rcu_cblist_n_cbs(&rdp->nocb_bypass)) {
+ raw_spin_unlock(&rdp->nocb_bypass_lock);
+ return false;
+ }
+ /* Note: ->cblist.len already accounts for ->nocb_bypass contents. */
+ if (rhp)
+ rcu_segcblist_inc_len(&rdp->cblist); /* Must precede enqueue. */
+ rcu_cblist_flush_enqueue(&rcl, &rdp->nocb_bypass, rhp);
+ rcu_segcblist_insert_pend_cbs(&rdp->cblist, &rcl);
+ WRITE_ONCE(rdp->nocb_bypass_first, j);
+ rcu_nocb_bypass_unlock(rdp);
+ return true;
+}
+
+/*
+ * Flush the ->nocb_bypass queue into ->cblist, enqueuing rhp if non-NULL.
+ * However, if there is a callback to be enqueued and if ->nocb_bypass
+ * proves to be initially empty, just return false because the no-CB GP
+ * kthread may need to be awakened in this case.
+ *
+ * Note that this function always returns true if rhp is NULL.
+ */
+static bool rcu_nocb_flush_bypass(struct rcu_data *rdp, struct rcu_head *rhp,
+ unsigned long j)
+{
+ if (!rcu_rdp_is_offloaded(rdp))
+ return true;
+ rcu_lockdep_assert_cblist_protected(rdp);
+ rcu_nocb_bypass_lock(rdp);
+ return rcu_nocb_do_flush_bypass(rdp, rhp, j);
+}
+
+/*
+ * If the ->nocb_bypass_lock is immediately available, flush the
+ * ->nocb_bypass queue into ->cblist.
+ */
+static void rcu_nocb_try_flush_bypass(struct rcu_data *rdp, unsigned long j)
+{
+ rcu_lockdep_assert_cblist_protected(rdp);
+ if (!rcu_rdp_is_offloaded(rdp) ||
+ !rcu_nocb_bypass_trylock(rdp))
+ return;
+ WARN_ON_ONCE(!rcu_nocb_do_flush_bypass(rdp, NULL, j));
+}
+
+/*
+ * See whether it is appropriate to use the ->nocb_bypass list in order
+ * to control contention on ->nocb_lock. A limited number of direct
+ * enqueues are permitted into ->cblist per jiffy. If ->nocb_bypass
+ * is non-empty, further callbacks must be placed into ->nocb_bypass,
+ * otherwise rcu_barrier() breaks. Use rcu_nocb_flush_bypass() to switch
+ * back to direct use of ->cblist. However, ->nocb_bypass should not be
+ * used if ->cblist is empty, because otherwise callbacks can be stranded
+ * on ->nocb_bypass because we cannot count on the current CPU ever again
+ * invoking call_rcu(). The general rule is that if ->nocb_bypass is
+ * non-empty, the corresponding no-CBs grace-period kthread must not be
+ * in an indefinite sleep state.
+ *
+ * Finally, it is not permitted to use the bypass during early boot,
+ * as doing so would confuse the auto-initialization code. Besides
+ * which, there is no point in worrying about lock contention while
+ * there is only one CPU in operation.
+ */
+static bool rcu_nocb_try_bypass(struct rcu_data *rdp, struct rcu_head *rhp,
+ bool *was_alldone, unsigned long flags)
+{
+ unsigned long c;
+ unsigned long cur_gp_seq;
+ unsigned long j = jiffies;
+ long ncbs = rcu_cblist_n_cbs(&rdp->nocb_bypass);
+
+ lockdep_assert_irqs_disabled();
+
+ // Pure softirq/rcuc based processing: no bypassing, no
+ // locking.
+ if (!rcu_rdp_is_offloaded(rdp)) {
+ *was_alldone = !rcu_segcblist_pend_cbs(&rdp->cblist);
+ return false;
+ }
+
+ // In the process of (de-)offloading: no bypassing, but
+ // locking.
+ if (!rcu_segcblist_completely_offloaded(&rdp->cblist)) {
+ rcu_nocb_lock(rdp);
+ *was_alldone = !rcu_segcblist_pend_cbs(&rdp->cblist);
+ return false; /* Not offloaded, no bypassing. */
+ }
+
+ // Don't use ->nocb_bypass during early boot.
+ if (rcu_scheduler_active != RCU_SCHEDULER_RUNNING) {
+ rcu_nocb_lock(rdp);
+ WARN_ON_ONCE(rcu_cblist_n_cbs(&rdp->nocb_bypass));
+ *was_alldone = !rcu_segcblist_pend_cbs(&rdp->cblist);
+ return false;
+ }
+
+ // If we have advanced to a new jiffy, reset counts to allow
+ // moving back from ->nocb_bypass to ->cblist.
+ if (j == rdp->nocb_nobypass_last) {
+ c = rdp->nocb_nobypass_count + 1;
+ } else {
+ WRITE_ONCE(rdp->nocb_nobypass_last, j);
+ c = rdp->nocb_nobypass_count - nocb_nobypass_lim_per_jiffy;
+ if (ULONG_CMP_LT(rdp->nocb_nobypass_count,
+ nocb_nobypass_lim_per_jiffy))
+ c = 0;
+ else if (c > nocb_nobypass_lim_per_jiffy)
+ c = nocb_nobypass_lim_per_jiffy;
+ }
+ WRITE_ONCE(rdp->nocb_nobypass_count, c);
+
+ // If there hasn't yet been all that many ->cblist enqueues
+ // this jiffy, tell the caller to enqueue onto ->cblist. But flush
+ // ->nocb_bypass first.
+ if (rdp->nocb_nobypass_count < nocb_nobypass_lim_per_jiffy) {
+ rcu_nocb_lock(rdp);
+ *was_alldone = !rcu_segcblist_pend_cbs(&rdp->cblist);
+ if (*was_alldone)
+ trace_rcu_nocb_wake(rcu_state.name, rdp->cpu,
+ TPS("FirstQ"));
+ WARN_ON_ONCE(!rcu_nocb_flush_bypass(rdp, NULL, j));
+ WARN_ON_ONCE(rcu_cblist_n_cbs(&rdp->nocb_bypass));
+ return false; // Caller must enqueue the callback.
+ }
+
+ // If ->nocb_bypass has been used too long or is too full,
+ // flush ->nocb_bypass to ->cblist.
+ if ((ncbs && j != READ_ONCE(rdp->nocb_bypass_first)) ||
+ ncbs >= qhimark) {
+ rcu_nocb_lock(rdp);
+ if (!rcu_nocb_flush_bypass(rdp, rhp, j)) {
+ *was_alldone = !rcu_segcblist_pend_cbs(&rdp->cblist);
+ if (*was_alldone)
+ trace_rcu_nocb_wake(rcu_state.name, rdp->cpu,
+ TPS("FirstQ"));
+ WARN_ON_ONCE(rcu_cblist_n_cbs(&rdp->nocb_bypass));
+ return false; // Caller must enqueue the callback.
+ }
+ if (j != rdp->nocb_gp_adv_time &&
+ rcu_segcblist_nextgp(&rdp->cblist, &cur_gp_seq) &&
+ rcu_seq_done(&rdp->mynode->gp_seq, cur_gp_seq)) {
+ rcu_advance_cbs_nowake(rdp->mynode, rdp);
+ rdp->nocb_gp_adv_time = j;
+ }
+ rcu_nocb_unlock_irqrestore(rdp, flags);
+ return true; // Callback already enqueued.
+ }
+
+ // We need to use the bypass.
+ rcu_nocb_wait_contended(rdp);
+ rcu_nocb_bypass_lock(rdp);
+ ncbs = rcu_cblist_n_cbs(&rdp->nocb_bypass);
+ rcu_segcblist_inc_len(&rdp->cblist); /* Must precede enqueue. */
+ rcu_cblist_enqueue(&rdp->nocb_bypass, rhp);
+ if (!ncbs) {
+ WRITE_ONCE(rdp->nocb_bypass_first, j);
+ trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("FirstBQ"));
+ }
+ rcu_nocb_bypass_unlock(rdp);
+ smp_mb(); /* Order enqueue before wake. */
+ if (ncbs) {
+ local_irq_restore(flags);
+ } else {
+ // No-CBs GP kthread might be indefinitely asleep, if so, wake.
+ rcu_nocb_lock(rdp); // Rare during call_rcu() flood.
+ if (!rcu_segcblist_pend_cbs(&rdp->cblist)) {
+ trace_rcu_nocb_wake(rcu_state.name, rdp->cpu,
+ TPS("FirstBQwake"));
+ __call_rcu_nocb_wake(rdp, true, flags);
+ } else {
+ trace_rcu_nocb_wake(rcu_state.name, rdp->cpu,
+ TPS("FirstBQnoWake"));
+ rcu_nocb_unlock_irqrestore(rdp, flags);
+ }
+ }
+ return true; // Callback already enqueued.
+}
+
+/*
+ * Awaken the no-CBs grace-period kthread if needed, either due to it
+ * legitimately being asleep or due to overload conditions.
+ *
+ * If warranted, also wake up the kthread servicing this CPUs queues.
+ */
+static void __call_rcu_nocb_wake(struct rcu_data *rdp, bool was_alldone,
+ unsigned long flags)
+ __releases(rdp->nocb_lock)
+{
+ unsigned long cur_gp_seq;
+ unsigned long j;
+ long len;
+ struct task_struct *t;
+
+ // If we are being polled or there is no kthread, just leave.
+ t = READ_ONCE(rdp->nocb_gp_kthread);
+ if (rcu_nocb_poll || !t) {
+ rcu_nocb_unlock_irqrestore(rdp, flags);
+ trace_rcu_nocb_wake(rcu_state.name, rdp->cpu,
+ TPS("WakeNotPoll"));
+ return;
+ }
+ // Need to actually to a wakeup.
+ len = rcu_segcblist_n_cbs(&rdp->cblist);
+ if (was_alldone) {
+ rdp->qlen_last_fqs_check = len;
+ if (!irqs_disabled_flags(flags)) {
+ /* ... if queue was empty ... */
+ rcu_nocb_unlock_irqrestore(rdp, flags);
+ wake_nocb_gp(rdp, false);
+ trace_rcu_nocb_wake(rcu_state.name, rdp->cpu,
+ TPS("WakeEmpty"));
+ } else {
+ rcu_nocb_unlock_irqrestore(rdp, flags);
+ wake_nocb_gp_defer(rdp, RCU_NOCB_WAKE,
+ TPS("WakeEmptyIsDeferred"));
+ }
+ } else if (len > rdp->qlen_last_fqs_check + qhimark) {
+ /* ... or if many callbacks queued. */
+ rdp->qlen_last_fqs_check = len;
+ j = jiffies;
+ if (j != rdp->nocb_gp_adv_time &&
+ rcu_segcblist_nextgp(&rdp->cblist, &cur_gp_seq) &&
+ rcu_seq_done(&rdp->mynode->gp_seq, cur_gp_seq)) {
+ rcu_advance_cbs_nowake(rdp->mynode, rdp);
+ rdp->nocb_gp_adv_time = j;
+ }
+ smp_mb(); /* Enqueue before timer_pending(). */
+ if ((rdp->nocb_cb_sleep ||
+ !rcu_segcblist_ready_cbs(&rdp->cblist)) &&
+ !timer_pending(&rdp->nocb_timer)) {
+ rcu_nocb_unlock_irqrestore(rdp, flags);
+ wake_nocb_gp_defer(rdp, RCU_NOCB_WAKE_FORCE,
+ TPS("WakeOvfIsDeferred"));
+ } else {
+ rcu_nocb_unlock_irqrestore(rdp, flags);
+ trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("WakeNot"));
+ }
+ } else {
+ rcu_nocb_unlock_irqrestore(rdp, flags);
+ trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("WakeNot"));
+ }
+}
+
+static int nocb_gp_toggle_rdp(struct rcu_data *rdp,
+ bool *wake_state)
+{
+ struct rcu_segcblist *cblist = &rdp->cblist;
+ unsigned long flags;
+ int ret;
+
+ rcu_nocb_lock_irqsave(rdp, flags);
+ if (rcu_segcblist_test_flags(cblist, SEGCBLIST_OFFLOADED) &&
+ !rcu_segcblist_test_flags(cblist, SEGCBLIST_KTHREAD_GP)) {
+ /*
+ * Offloading. Set our flag and notify the offload worker.
+ * We will handle this rdp until it ever gets de-offloaded.
+ */
+ rcu_segcblist_set_flags(cblist, SEGCBLIST_KTHREAD_GP);
+ if (rcu_segcblist_test_flags(cblist, SEGCBLIST_KTHREAD_CB))
+ *wake_state = true;
+ ret = 1;
+ } else if (!rcu_segcblist_test_flags(cblist, SEGCBLIST_OFFLOADED) &&
+ rcu_segcblist_test_flags(cblist, SEGCBLIST_KTHREAD_GP)) {
+ /*
+ * De-offloading. Clear our flag and notify the de-offload worker.
+ * We will ignore this rdp until it ever gets re-offloaded.
+ */
+ rcu_segcblist_clear_flags(cblist, SEGCBLIST_KTHREAD_GP);
+ if (!rcu_segcblist_test_flags(cblist, SEGCBLIST_KTHREAD_CB))
+ *wake_state = true;
+ ret = 0;
+ } else {
+ WARN_ON_ONCE(1);
+ ret = -1;
+ }
+
+ rcu_nocb_unlock_irqrestore(rdp, flags);
+
+ return ret;
+}
+
+static void nocb_gp_sleep(struct rcu_data *my_rdp, int cpu)
+{
+ trace_rcu_nocb_wake(rcu_state.name, cpu, TPS("Sleep"));
+ swait_event_interruptible_exclusive(my_rdp->nocb_gp_wq,
+ !READ_ONCE(my_rdp->nocb_gp_sleep));
+ trace_rcu_nocb_wake(rcu_state.name, cpu, TPS("EndSleep"));
+}
+
+/*
+ * No-CBs GP kthreads come here to wait for additional callbacks to show up
+ * or for grace periods to end.
+ */
+static void nocb_gp_wait(struct rcu_data *my_rdp)
+{
+ bool bypass = false;
+ long bypass_ncbs;
+ int __maybe_unused cpu = my_rdp->cpu;
+ unsigned long cur_gp_seq;
+ unsigned long flags;
+ bool gotcbs = false;
+ unsigned long j = jiffies;
+ bool needwait_gp = false; // This prevents actual uninitialized use.
+ bool needwake;
+ bool needwake_gp;
+ struct rcu_data *rdp, *rdp_toggling = NULL;
+ struct rcu_node *rnp;
+ unsigned long wait_gp_seq = 0; // Suppress "use uninitialized" warning.
+ bool wasempty = false;
+
+ /*
+ * Each pass through the following loop checks for CBs and for the
+ * nearest grace period (if any) to wait for next. The CB kthreads
+ * and the global grace-period kthread are awakened if needed.
+ */
+ WARN_ON_ONCE(my_rdp->nocb_gp_rdp != my_rdp);
+ /*
+ * An rcu_data structure is removed from the list after its
+ * CPU is de-offloaded and added to the list before that CPU is
+ * (re-)offloaded. If the following loop happens to be referencing
+ * that rcu_data structure during the time that the corresponding
+ * CPU is de-offloaded and then immediately re-offloaded, this
+ * loop's rdp pointer will be carried to the end of the list by
+ * the resulting pair of list operations. This can cause the loop
+ * to skip over some of the rcu_data structures that were supposed
+ * to have been scanned. Fortunately a new iteration through the
+ * entire loop is forced after a given CPU's rcu_data structure
+ * is added to the list, so the skipped-over rcu_data structures
+ * won't be ignored for long.
+ */
+ list_for_each_entry(rdp, &my_rdp->nocb_head_rdp, nocb_entry_rdp) {
+ trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("Check"));
+ rcu_nocb_lock_irqsave(rdp, flags);
+ lockdep_assert_held(&rdp->nocb_lock);
+ bypass_ncbs = rcu_cblist_n_cbs(&rdp->nocb_bypass);
+ if (bypass_ncbs &&
+ (time_after(j, READ_ONCE(rdp->nocb_bypass_first) + 1) ||
+ bypass_ncbs > 2 * qhimark)) {
+ // Bypass full or old, so flush it.
+ (void)rcu_nocb_try_flush_bypass(rdp, j);
+ bypass_ncbs = rcu_cblist_n_cbs(&rdp->nocb_bypass);
+ } else if (!bypass_ncbs && rcu_segcblist_empty(&rdp->cblist)) {
+ rcu_nocb_unlock_irqrestore(rdp, flags);
+ continue; /* No callbacks here, try next. */
+ }
+ if (bypass_ncbs) {
+ trace_rcu_nocb_wake(rcu_state.name, rdp->cpu,
+ TPS("Bypass"));
+ bypass = true;
+ }
+ rnp = rdp->mynode;
+
+ // Advance callbacks if helpful and low contention.
+ needwake_gp = false;
+ if (!rcu_segcblist_restempty(&rdp->cblist,
+ RCU_NEXT_READY_TAIL) ||
+ (rcu_segcblist_nextgp(&rdp->cblist, &cur_gp_seq) &&
+ rcu_seq_done(&rnp->gp_seq, cur_gp_seq))) {
+ raw_spin_lock_rcu_node(rnp); /* irqs disabled. */
+ needwake_gp = rcu_advance_cbs(rnp, rdp);
+ wasempty = rcu_segcblist_restempty(&rdp->cblist,
+ RCU_NEXT_READY_TAIL);
+ raw_spin_unlock_rcu_node(rnp); /* irqs disabled. */
+ }
+ // Need to wait on some grace period?
+ WARN_ON_ONCE(wasempty &&
+ !rcu_segcblist_restempty(&rdp->cblist,
+ RCU_NEXT_READY_TAIL));
+ if (rcu_segcblist_nextgp(&rdp->cblist, &cur_gp_seq)) {
+ if (!needwait_gp ||
+ ULONG_CMP_LT(cur_gp_seq, wait_gp_seq))
+ wait_gp_seq = cur_gp_seq;
+ needwait_gp = true;
+ trace_rcu_nocb_wake(rcu_state.name, rdp->cpu,
+ TPS("NeedWaitGP"));
+ }
+ if (rcu_segcblist_ready_cbs(&rdp->cblist)) {
+ needwake = rdp->nocb_cb_sleep;
+ WRITE_ONCE(rdp->nocb_cb_sleep, false);
+ smp_mb(); /* CB invocation -after- GP end. */
+ } else {
+ needwake = false;
+ }
+ rcu_nocb_unlock_irqrestore(rdp, flags);
+ if (needwake) {
+ swake_up_one(&rdp->nocb_cb_wq);
+ gotcbs = true;
+ }
+ if (needwake_gp)
+ rcu_gp_kthread_wake();
+ }
+
+ my_rdp->nocb_gp_bypass = bypass;
+ my_rdp->nocb_gp_gp = needwait_gp;
+ my_rdp->nocb_gp_seq = needwait_gp ? wait_gp_seq : 0;
+
+ if (bypass && !rcu_nocb_poll) {
+ // At least one child with non-empty ->nocb_bypass, so set
+ // timer in order to avoid stranding its callbacks.
+ wake_nocb_gp_defer(my_rdp, RCU_NOCB_WAKE_BYPASS,
+ TPS("WakeBypassIsDeferred"));
+ }
+ if (rcu_nocb_poll) {
+ /* Polling, so trace if first poll in the series. */
+ if (gotcbs)
+ trace_rcu_nocb_wake(rcu_state.name, cpu, TPS("Poll"));
+ if (list_empty(&my_rdp->nocb_head_rdp)) {
+ raw_spin_lock_irqsave(&my_rdp->nocb_gp_lock, flags);
+ if (!my_rdp->nocb_toggling_rdp)
+ WRITE_ONCE(my_rdp->nocb_gp_sleep, true);
+ raw_spin_unlock_irqrestore(&my_rdp->nocb_gp_lock, flags);
+ /* Wait for any offloading rdp */
+ nocb_gp_sleep(my_rdp, cpu);
+ } else {
+ schedule_timeout_idle(1);
+ }
+ } else if (!needwait_gp) {
+ /* Wait for callbacks to appear. */
+ nocb_gp_sleep(my_rdp, cpu);
+ } else {
+ rnp = my_rdp->mynode;
+ trace_rcu_this_gp(rnp, my_rdp, wait_gp_seq, TPS("StartWait"));
+ swait_event_interruptible_exclusive(
+ rnp->nocb_gp_wq[rcu_seq_ctr(wait_gp_seq) & 0x1],
+ rcu_seq_done(&rnp->gp_seq, wait_gp_seq) ||
+ !READ_ONCE(my_rdp->nocb_gp_sleep));
+ trace_rcu_this_gp(rnp, my_rdp, wait_gp_seq, TPS("EndWait"));
+ }
+
+ if (!rcu_nocb_poll) {
+ raw_spin_lock_irqsave(&my_rdp->nocb_gp_lock, flags);
+ // (De-)queue an rdp to/from the group if its nocb state is changing
+ rdp_toggling = my_rdp->nocb_toggling_rdp;
+ if (rdp_toggling)
+ my_rdp->nocb_toggling_rdp = NULL;
+
+ if (my_rdp->nocb_defer_wakeup > RCU_NOCB_WAKE_NOT) {
+ WRITE_ONCE(my_rdp->nocb_defer_wakeup, RCU_NOCB_WAKE_NOT);
+ del_timer(&my_rdp->nocb_timer);
+ }
+ WRITE_ONCE(my_rdp->nocb_gp_sleep, true);
+ raw_spin_unlock_irqrestore(&my_rdp->nocb_gp_lock, flags);
+ } else {
+ rdp_toggling = READ_ONCE(my_rdp->nocb_toggling_rdp);
+ if (rdp_toggling) {
+ /*
+ * Paranoid locking to make sure nocb_toggling_rdp is well
+ * reset *before* we (re)set SEGCBLIST_KTHREAD_GP or we could
+ * race with another round of nocb toggling for this rdp.
+ * Nocb locking should prevent from that already but we stick
+ * to paranoia, especially in rare path.
+ */
+ raw_spin_lock_irqsave(&my_rdp->nocb_gp_lock, flags);
+ my_rdp->nocb_toggling_rdp = NULL;
+ raw_spin_unlock_irqrestore(&my_rdp->nocb_gp_lock, flags);
+ }
+ }
+
+ if (rdp_toggling) {
+ bool wake_state = false;
+ int ret;
+
+ ret = nocb_gp_toggle_rdp(rdp_toggling, &wake_state);
+ if (ret == 1)
+ list_add_tail(&rdp_toggling->nocb_entry_rdp, &my_rdp->nocb_head_rdp);
+ else if (ret == 0)
+ list_del(&rdp_toggling->nocb_entry_rdp);
+ if (wake_state)
+ swake_up_one(&rdp_toggling->nocb_state_wq);
+ }
+
+ my_rdp->nocb_gp_seq = -1;
+ WARN_ON(signal_pending(current));
+}
+
+/*
+ * No-CBs grace-period-wait kthread. There is one of these per group
+ * of CPUs, but only once at least one CPU in that group has come online
+ * at least once since boot. This kthread checks for newly posted
+ * callbacks from any of the CPUs it is responsible for, waits for a
+ * grace period, then awakens all of the rcu_nocb_cb_kthread() instances
+ * that then have callback-invocation work to do.
+ */
+static int rcu_nocb_gp_kthread(void *arg)
+{
+ struct rcu_data *rdp = arg;
+
+ for (;;) {
+ WRITE_ONCE(rdp->nocb_gp_loops, rdp->nocb_gp_loops + 1);
+ nocb_gp_wait(rdp);
+ cond_resched_tasks_rcu_qs();
+ }
+ return 0;
+}
+
+static inline bool nocb_cb_can_run(struct rcu_data *rdp)
+{
+ u8 flags = SEGCBLIST_OFFLOADED | SEGCBLIST_KTHREAD_CB;
+
+ return rcu_segcblist_test_flags(&rdp->cblist, flags);
+}
+
+static inline bool nocb_cb_wait_cond(struct rcu_data *rdp)
+{
+ return nocb_cb_can_run(rdp) && !READ_ONCE(rdp->nocb_cb_sleep);
+}
+
+/*
+ * Invoke any ready callbacks from the corresponding no-CBs CPU,
+ * then, if there are no more, wait for more to appear.
+ */
+static void nocb_cb_wait(struct rcu_data *rdp)
+{
+ struct rcu_segcblist *cblist = &rdp->cblist;
+ unsigned long cur_gp_seq;
+ unsigned long flags;
+ bool needwake_state = false;
+ bool needwake_gp = false;
+ bool can_sleep = true;
+ struct rcu_node *rnp = rdp->mynode;
+
+ do {
+ swait_event_interruptible_exclusive(rdp->nocb_cb_wq,
+ nocb_cb_wait_cond(rdp));
+
+ // VVV Ensure CB invocation follows _sleep test.
+ if (smp_load_acquire(&rdp->nocb_cb_sleep)) { // ^^^
+ WARN_ON(signal_pending(current));
+ trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("WokeEmpty"));
+ }
+ } while (!nocb_cb_can_run(rdp));
+
+
+ local_irq_save(flags);
+ rcu_momentary_dyntick_idle();
+ local_irq_restore(flags);
+ /*
+ * Disable BH to provide the expected environment. Also, when
+ * transitioning to/from NOCB mode, a self-requeuing callback might
+ * be invoked from softirq. A short grace period could cause both
+ * instances of this callback would execute concurrently.
+ */
+ local_bh_disable();
+ rcu_do_batch(rdp);
+ local_bh_enable();
+ lockdep_assert_irqs_enabled();
+ rcu_nocb_lock_irqsave(rdp, flags);
+ if (rcu_segcblist_nextgp(cblist, &cur_gp_seq) &&
+ rcu_seq_done(&rnp->gp_seq, cur_gp_seq) &&
+ raw_spin_trylock_rcu_node(rnp)) { /* irqs already disabled. */
+ needwake_gp = rcu_advance_cbs(rdp->mynode, rdp);
+ raw_spin_unlock_rcu_node(rnp); /* irqs remain disabled. */
+ }
+
+ if (rcu_segcblist_test_flags(cblist, SEGCBLIST_OFFLOADED)) {
+ if (!rcu_segcblist_test_flags(cblist, SEGCBLIST_KTHREAD_CB)) {
+ rcu_segcblist_set_flags(cblist, SEGCBLIST_KTHREAD_CB);
+ if (rcu_segcblist_test_flags(cblist, SEGCBLIST_KTHREAD_GP))
+ needwake_state = true;
+ }
+ if (rcu_segcblist_ready_cbs(cblist))
+ can_sleep = false;
+ } else {
+ /*
+ * De-offloading. Clear our flag and notify the de-offload worker.
+ * We won't touch the callbacks and keep sleeping until we ever
+ * get re-offloaded.
+ */
+ WARN_ON_ONCE(!rcu_segcblist_test_flags(cblist, SEGCBLIST_KTHREAD_CB));
+ rcu_segcblist_clear_flags(cblist, SEGCBLIST_KTHREAD_CB);
+ if (!rcu_segcblist_test_flags(cblist, SEGCBLIST_KTHREAD_GP))
+ needwake_state = true;
+ }
+
+ WRITE_ONCE(rdp->nocb_cb_sleep, can_sleep);
+
+ if (rdp->nocb_cb_sleep)
+ trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("CBSleep"));
+
+ rcu_nocb_unlock_irqrestore(rdp, flags);
+ if (needwake_gp)
+ rcu_gp_kthread_wake();
+
+ if (needwake_state)
+ swake_up_one(&rdp->nocb_state_wq);
+}
+
+/*
+ * Per-rcu_data kthread, but only for no-CBs CPUs. Repeatedly invoke
+ * nocb_cb_wait() to do the dirty work.
+ */
+static int rcu_nocb_cb_kthread(void *arg)
+{
+ struct rcu_data *rdp = arg;
+
+ // Each pass through this loop does one callback batch, and,
+ // if there are no more ready callbacks, waits for them.
+ for (;;) {
+ nocb_cb_wait(rdp);
+ cond_resched_tasks_rcu_qs();
+ }
+ return 0;
+}
+
+/* Is a deferred wakeup of rcu_nocb_kthread() required? */
+static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp, int level)
+{
+ return READ_ONCE(rdp->nocb_defer_wakeup) >= level;
+}
+
+/* Do a deferred wakeup of rcu_nocb_kthread(). */
+static bool do_nocb_deferred_wakeup_common(struct rcu_data *rdp_gp,
+ struct rcu_data *rdp, int level,
+ unsigned long flags)
+ __releases(rdp_gp->nocb_gp_lock)
+{
+ int ndw;
+ int ret;
+
+ if (!rcu_nocb_need_deferred_wakeup(rdp_gp, level)) {
+ raw_spin_unlock_irqrestore(&rdp_gp->nocb_gp_lock, flags);
+ return false;
+ }
+
+ ndw = rdp_gp->nocb_defer_wakeup;
+ ret = __wake_nocb_gp(rdp_gp, rdp, ndw == RCU_NOCB_WAKE_FORCE, flags);
+ trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("DeferredWake"));
+
+ return ret;
+}
+
+/* Do a deferred wakeup of rcu_nocb_kthread() from a timer handler. */
+static void do_nocb_deferred_wakeup_timer(struct timer_list *t)
+{
+ unsigned long flags;
+ struct rcu_data *rdp = from_timer(rdp, t, nocb_timer);
+
+ WARN_ON_ONCE(rdp->nocb_gp_rdp != rdp);
+ trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("Timer"));
+
+ raw_spin_lock_irqsave(&rdp->nocb_gp_lock, flags);
+ smp_mb__after_spinlock(); /* Timer expire before wakeup. */
+ do_nocb_deferred_wakeup_common(rdp, rdp, RCU_NOCB_WAKE_BYPASS, flags);
+}
+
+/*
+ * Do a deferred wakeup of rcu_nocb_kthread() from fastpath.
+ * This means we do an inexact common-case check. Note that if
+ * we miss, ->nocb_timer will eventually clean things up.
+ */
+static bool do_nocb_deferred_wakeup(struct rcu_data *rdp)
+{
+ unsigned long flags;
+ struct rcu_data *rdp_gp = rdp->nocb_gp_rdp;
+
+ if (!rdp_gp || !rcu_nocb_need_deferred_wakeup(rdp_gp, RCU_NOCB_WAKE))
+ return false;
+
+ raw_spin_lock_irqsave(&rdp_gp->nocb_gp_lock, flags);
+ return do_nocb_deferred_wakeup_common(rdp_gp, rdp, RCU_NOCB_WAKE, flags);
+}
+
+void rcu_nocb_flush_deferred_wakeup(void)
+{
+ do_nocb_deferred_wakeup(this_cpu_ptr(&rcu_data));
+}
+EXPORT_SYMBOL_GPL(rcu_nocb_flush_deferred_wakeup);
+
+static int rdp_offload_toggle(struct rcu_data *rdp,
+ bool offload, unsigned long flags)
+ __releases(rdp->nocb_lock)
+{
+ struct rcu_segcblist *cblist = &rdp->cblist;
+ struct rcu_data *rdp_gp = rdp->nocb_gp_rdp;
+ bool wake_gp = false;
+
+ rcu_segcblist_offload(cblist, offload);
+
+ if (rdp->nocb_cb_sleep)
+ rdp->nocb_cb_sleep = false;
+ rcu_nocb_unlock_irqrestore(rdp, flags);
+
+ /*
+ * Ignore former value of nocb_cb_sleep and force wake up as it could
+ * have been spuriously set to false already.
+ */
+ swake_up_one(&rdp->nocb_cb_wq);
+
+ raw_spin_lock_irqsave(&rdp_gp->nocb_gp_lock, flags);
+ // Queue this rdp for add/del to/from the list to iterate on rcuog
+ WRITE_ONCE(rdp_gp->nocb_toggling_rdp, rdp);
+ if (rdp_gp->nocb_gp_sleep) {
+ rdp_gp->nocb_gp_sleep = false;
+ wake_gp = true;
+ }
+ raw_spin_unlock_irqrestore(&rdp_gp->nocb_gp_lock, flags);
+
+ return wake_gp;
+}
+
+static long rcu_nocb_rdp_deoffload(void *arg)
+{
+ struct rcu_data *rdp = arg;
+ struct rcu_segcblist *cblist = &rdp->cblist;
+ unsigned long flags;
+ int wake_gp;
+ struct rcu_data *rdp_gp = rdp->nocb_gp_rdp;
+
+ /*
+ * rcu_nocb_rdp_deoffload() may be called directly if
+ * rcuog/o[p] spawn failed, because at this time the rdp->cpu
+ * is not online yet.
+ */
+ WARN_ON_ONCE((rdp->cpu != raw_smp_processor_id()) && cpu_online(rdp->cpu));
+
+ pr_info("De-offloading %d\n", rdp->cpu);
+
+ rcu_nocb_lock_irqsave(rdp, flags);
+ /*
+ * Flush once and for all now. This suffices because we are
+ * running on the target CPU holding ->nocb_lock (thus having
+ * interrupts disabled), and because rdp_offload_toggle()
+ * invokes rcu_segcblist_offload(), which clears SEGCBLIST_OFFLOADED.
+ * Thus future calls to rcu_segcblist_completely_offloaded() will
+ * return false, which means that future calls to rcu_nocb_try_bypass()
+ * will refuse to put anything into the bypass.
+ */
+ WARN_ON_ONCE(!rcu_nocb_flush_bypass(rdp, NULL, jiffies));
+ /*
+ * Start with invoking rcu_core() early. This way if the current thread
+ * happens to preempt an ongoing call to rcu_core() in the middle,
+ * leaving some work dismissed because rcu_core() still thinks the rdp is
+ * completely offloaded, we are guaranteed a nearby future instance of
+ * rcu_core() to catch up.
+ */
+ rcu_segcblist_set_flags(cblist, SEGCBLIST_RCU_CORE);
+ invoke_rcu_core();
+ wake_gp = rdp_offload_toggle(rdp, false, flags);
+
+ mutex_lock(&rdp_gp->nocb_gp_kthread_mutex);
+ if (rdp_gp->nocb_gp_kthread) {
+ if (wake_gp)
+ wake_up_process(rdp_gp->nocb_gp_kthread);
+
+ /*
+ * If rcuo[p] kthread spawn failed, directly remove SEGCBLIST_KTHREAD_CB.
+ * Just wait SEGCBLIST_KTHREAD_GP to be cleared by rcuog.
+ */
+ if (!rdp->nocb_cb_kthread) {
+ rcu_nocb_lock_irqsave(rdp, flags);
+ rcu_segcblist_clear_flags(&rdp->cblist, SEGCBLIST_KTHREAD_CB);
+ rcu_nocb_unlock_irqrestore(rdp, flags);
+ }
+
+ swait_event_exclusive(rdp->nocb_state_wq,
+ !rcu_segcblist_test_flags(cblist,
+ SEGCBLIST_KTHREAD_CB | SEGCBLIST_KTHREAD_GP));
+ } else {
+ /*
+ * No kthread to clear the flags for us or remove the rdp from the nocb list
+ * to iterate. Do it here instead. Locking doesn't look stricly necessary
+ * but we stick to paranoia in this rare path.
+ */
+ rcu_nocb_lock_irqsave(rdp, flags);
+ rcu_segcblist_clear_flags(&rdp->cblist,
+ SEGCBLIST_KTHREAD_CB | SEGCBLIST_KTHREAD_GP);
+ rcu_nocb_unlock_irqrestore(rdp, flags);
+
+ list_del(&rdp->nocb_entry_rdp);
+ }
+ mutex_unlock(&rdp_gp->nocb_gp_kthread_mutex);
+
+ /*
+ * Lock one last time to acquire latest callback updates from kthreads
+ * so we can later handle callbacks locally without locking.
+ */
+ rcu_nocb_lock_irqsave(rdp, flags);
+ /*
+ * Theoretically we could clear SEGCBLIST_LOCKING after the nocb
+ * lock is released but how about being paranoid for once?
+ */
+ rcu_segcblist_clear_flags(cblist, SEGCBLIST_LOCKING);
+ /*
+ * Without SEGCBLIST_LOCKING, we can't use
+ * rcu_nocb_unlock_irqrestore() anymore.
+ */
+ raw_spin_unlock_irqrestore(&rdp->nocb_lock, flags);
+
+ /* Sanity check */
+ WARN_ON_ONCE(rcu_cblist_n_cbs(&rdp->nocb_bypass));
+
+
+ return 0;
+}
+
+int rcu_nocb_cpu_deoffload(int cpu)
+{
+ struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
+ int ret = 0;
+
+ cpus_read_lock();
+ mutex_lock(&rcu_state.barrier_mutex);
+ if (rcu_rdp_is_offloaded(rdp)) {
+ if (cpu_online(cpu)) {
+ ret = work_on_cpu(cpu, rcu_nocb_rdp_deoffload, rdp);
+ if (!ret)
+ cpumask_clear_cpu(cpu, rcu_nocb_mask);
+ } else {
+ pr_info("NOCB: Cannot CB-deoffload offline CPU %d\n", rdp->cpu);
+ ret = -EINVAL;
+ }
+ }
+ mutex_unlock(&rcu_state.barrier_mutex);
+ cpus_read_unlock();
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(rcu_nocb_cpu_deoffload);
+
+static long rcu_nocb_rdp_offload(void *arg)
+{
+ struct rcu_data *rdp = arg;
+ struct rcu_segcblist *cblist = &rdp->cblist;
+ unsigned long flags;
+ int wake_gp;
+ struct rcu_data *rdp_gp = rdp->nocb_gp_rdp;
+
+ WARN_ON_ONCE(rdp->cpu != raw_smp_processor_id());
+ /*
+ * For now we only support re-offload, ie: the rdp must have been
+ * offloaded on boot first.
+ */
+ if (!rdp->nocb_gp_rdp)
+ return -EINVAL;
+
+ if (WARN_ON_ONCE(!rdp_gp->nocb_gp_kthread))
+ return -EINVAL;
+
+ pr_info("Offloading %d\n", rdp->cpu);
+
+ /*
+ * Can't use rcu_nocb_lock_irqsave() before SEGCBLIST_LOCKING
+ * is set.
+ */
+ raw_spin_lock_irqsave(&rdp->nocb_lock, flags);
+
+ /*
+ * We didn't take the nocb lock while working on the
+ * rdp->cblist with SEGCBLIST_LOCKING cleared (pure softirq/rcuc mode).
+ * Every modifications that have been done previously on
+ * rdp->cblist must be visible remotely by the nocb kthreads
+ * upon wake up after reading the cblist flags.
+ *
+ * The layout against nocb_lock enforces that ordering:
+ *
+ * __rcu_nocb_rdp_offload() nocb_cb_wait()/nocb_gp_wait()
+ * ------------------------- ----------------------------
+ * WRITE callbacks rcu_nocb_lock()
+ * rcu_nocb_lock() READ flags
+ * WRITE flags READ callbacks
+ * rcu_nocb_unlock() rcu_nocb_unlock()
+ */
+ wake_gp = rdp_offload_toggle(rdp, true, flags);
+ if (wake_gp)
+ wake_up_process(rdp_gp->nocb_gp_kthread);
+ swait_event_exclusive(rdp->nocb_state_wq,
+ rcu_segcblist_test_flags(cblist, SEGCBLIST_KTHREAD_CB) &&
+ rcu_segcblist_test_flags(cblist, SEGCBLIST_KTHREAD_GP));
+
+ /*
+ * All kthreads are ready to work, we can finally relieve rcu_core() and
+ * enable nocb bypass.
+ */
+ rcu_nocb_lock_irqsave(rdp, flags);
+ rcu_segcblist_clear_flags(cblist, SEGCBLIST_RCU_CORE);
+ rcu_nocb_unlock_irqrestore(rdp, flags);
+
+ return 0;
+}
+
+int rcu_nocb_cpu_offload(int cpu)
+{
+ struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
+ int ret = 0;
+
+ cpus_read_lock();
+ mutex_lock(&rcu_state.barrier_mutex);
+ if (!rcu_rdp_is_offloaded(rdp)) {
+ if (cpu_online(cpu)) {
+ ret = work_on_cpu(cpu, rcu_nocb_rdp_offload, rdp);
+ if (!ret)
+ cpumask_set_cpu(cpu, rcu_nocb_mask);
+ } else {
+ pr_info("NOCB: Cannot CB-offload offline CPU %d\n", rdp->cpu);
+ ret = -EINVAL;
+ }
+ }
+ mutex_unlock(&rcu_state.barrier_mutex);
+ cpus_read_unlock();
+
+ return ret;
+}
+EXPORT_SYMBOL_GPL(rcu_nocb_cpu_offload);
+
+void __init rcu_init_nohz(void)
+{
+ int cpu;
+ bool need_rcu_nocb_mask = false;
+ bool offload_all = false;
+ struct rcu_data *rdp;
+
+#if defined(CONFIG_RCU_NOCB_CPU_DEFAULT_ALL)
+ if (!rcu_state.nocb_is_setup) {
+ need_rcu_nocb_mask = true;
+ offload_all = true;
+ }
+#endif /* #if defined(CONFIG_RCU_NOCB_CPU_DEFAULT_ALL) */
+
+#if defined(CONFIG_NO_HZ_FULL)
+ if (tick_nohz_full_running && !cpumask_empty(tick_nohz_full_mask)) {
+ need_rcu_nocb_mask = true;
+ offload_all = false; /* NO_HZ_FULL has its own mask. */
+ }
+#endif /* #if defined(CONFIG_NO_HZ_FULL) */
+
+ if (need_rcu_nocb_mask) {
+ if (!cpumask_available(rcu_nocb_mask)) {
+ if (!zalloc_cpumask_var(&rcu_nocb_mask, GFP_KERNEL)) {
+ pr_info("rcu_nocb_mask allocation failed, callback offloading disabled.\n");
+ return;
+ }
+ }
+ rcu_state.nocb_is_setup = true;
+ }
+
+ if (!rcu_state.nocb_is_setup)
+ return;
+
+#if defined(CONFIG_NO_HZ_FULL)
+ if (tick_nohz_full_running)
+ cpumask_or(rcu_nocb_mask, rcu_nocb_mask, tick_nohz_full_mask);
+#endif /* #if defined(CONFIG_NO_HZ_FULL) */
+
+ if (offload_all)
+ cpumask_setall(rcu_nocb_mask);
+
+ if (!cpumask_subset(rcu_nocb_mask, cpu_possible_mask)) {
+ pr_info("\tNote: kernel parameter 'rcu_nocbs=', 'nohz_full', or 'isolcpus=' contains nonexistent CPUs.\n");
+ cpumask_and(rcu_nocb_mask, cpu_possible_mask,
+ rcu_nocb_mask);
+ }
+ if (cpumask_empty(rcu_nocb_mask))
+ pr_info("\tOffload RCU callbacks from CPUs: (none).\n");
+ else
+ pr_info("\tOffload RCU callbacks from CPUs: %*pbl.\n",
+ cpumask_pr_args(rcu_nocb_mask));
+ if (rcu_nocb_poll)
+ pr_info("\tPoll for callbacks from no-CBs CPUs.\n");
+
+ for_each_cpu(cpu, rcu_nocb_mask) {
+ rdp = per_cpu_ptr(&rcu_data, cpu);
+ if (rcu_segcblist_empty(&rdp->cblist))
+ rcu_segcblist_init(&rdp->cblist);
+ rcu_segcblist_offload(&rdp->cblist, true);
+ rcu_segcblist_set_flags(&rdp->cblist, SEGCBLIST_KTHREAD_CB | SEGCBLIST_KTHREAD_GP);
+ rcu_segcblist_clear_flags(&rdp->cblist, SEGCBLIST_RCU_CORE);
+ }
+ rcu_organize_nocb_kthreads();
+}
+
+/* Initialize per-rcu_data variables for no-CBs CPUs. */
+static void __init rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp)
+{
+ init_swait_queue_head(&rdp->nocb_cb_wq);
+ init_swait_queue_head(&rdp->nocb_gp_wq);
+ init_swait_queue_head(&rdp->nocb_state_wq);
+ raw_spin_lock_init(&rdp->nocb_lock);
+ raw_spin_lock_init(&rdp->nocb_bypass_lock);
+ raw_spin_lock_init(&rdp->nocb_gp_lock);
+ timer_setup(&rdp->nocb_timer, do_nocb_deferred_wakeup_timer, 0);
+ rcu_cblist_init(&rdp->nocb_bypass);
+ mutex_init(&rdp->nocb_gp_kthread_mutex);
+}
+
+/*
+ * If the specified CPU is a no-CBs CPU that does not already have its
+ * rcuo CB kthread, spawn it. Additionally, if the rcuo GP kthread
+ * for this CPU's group has not yet been created, spawn it as well.
+ */
+static void rcu_spawn_cpu_nocb_kthread(int cpu)
+{
+ struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
+ struct rcu_data *rdp_gp;
+ struct task_struct *t;
+ struct sched_param sp;
+
+ if (!rcu_scheduler_fully_active || !rcu_state.nocb_is_setup)
+ return;
+
+ /* If there already is an rcuo kthread, then nothing to do. */
+ if (rdp->nocb_cb_kthread)
+ return;
+
+ /* If we didn't spawn the GP kthread first, reorganize! */
+ sp.sched_priority = kthread_prio;
+ rdp_gp = rdp->nocb_gp_rdp;
+ mutex_lock(&rdp_gp->nocb_gp_kthread_mutex);
+ if (!rdp_gp->nocb_gp_kthread) {
+ t = kthread_run(rcu_nocb_gp_kthread, rdp_gp,
+ "rcuog/%d", rdp_gp->cpu);
+ if (WARN_ONCE(IS_ERR(t), "%s: Could not start rcuo GP kthread, OOM is now expected behavior\n", __func__)) {
+ mutex_unlock(&rdp_gp->nocb_gp_kthread_mutex);
+ goto end;
+ }
+ WRITE_ONCE(rdp_gp->nocb_gp_kthread, t);
+ if (kthread_prio)
+ sched_setscheduler_nocheck(t, SCHED_FIFO, &sp);
+ }
+ mutex_unlock(&rdp_gp->nocb_gp_kthread_mutex);
+
+ /* Spawn the kthread for this CPU. */
+ t = kthread_run(rcu_nocb_cb_kthread, rdp,
+ "rcuo%c/%d", rcu_state.abbr, cpu);
+ if (WARN_ONCE(IS_ERR(t), "%s: Could not start rcuo CB kthread, OOM is now expected behavior\n", __func__))
+ goto end;
+
+ if (IS_ENABLED(CONFIG_RCU_NOCB_CPU_CB_BOOST) && kthread_prio)
+ sched_setscheduler_nocheck(t, SCHED_FIFO, &sp);
+
+ WRITE_ONCE(rdp->nocb_cb_kthread, t);
+ WRITE_ONCE(rdp->nocb_gp_kthread, rdp_gp->nocb_gp_kthread);
+ return;
+end:
+ mutex_lock(&rcu_state.barrier_mutex);
+ if (rcu_rdp_is_offloaded(rdp)) {
+ rcu_nocb_rdp_deoffload(rdp);
+ cpumask_clear_cpu(cpu, rcu_nocb_mask);
+ }
+ mutex_unlock(&rcu_state.barrier_mutex);
+}
+
+/* How many CB CPU IDs per GP kthread? Default of -1 for sqrt(nr_cpu_ids). */
+static int rcu_nocb_gp_stride = -1;
+module_param(rcu_nocb_gp_stride, int, 0444);
+
+/*
+ * Initialize GP-CB relationships for all no-CBs CPU.
+ */
+static void __init rcu_organize_nocb_kthreads(void)
+{
+ int cpu;
+ bool firsttime = true;
+ bool gotnocbs = false;
+ bool gotnocbscbs = true;
+ int ls = rcu_nocb_gp_stride;
+ int nl = 0; /* Next GP kthread. */
+ struct rcu_data *rdp;
+ struct rcu_data *rdp_gp = NULL; /* Suppress misguided gcc warn. */
+
+ if (!cpumask_available(rcu_nocb_mask))
+ return;
+ if (ls == -1) {
+ ls = nr_cpu_ids / int_sqrt(nr_cpu_ids);
+ rcu_nocb_gp_stride = ls;
+ }
+
+ /*
+ * Each pass through this loop sets up one rcu_data structure.
+ * Should the corresponding CPU come online in the future, then
+ * we will spawn the needed set of rcu_nocb_kthread() kthreads.
+ */
+ for_each_possible_cpu(cpu) {
+ rdp = per_cpu_ptr(&rcu_data, cpu);
+ if (rdp->cpu >= nl) {
+ /* New GP kthread, set up for CBs & next GP. */
+ gotnocbs = true;
+ nl = DIV_ROUND_UP(rdp->cpu + 1, ls) * ls;
+ rdp_gp = rdp;
+ INIT_LIST_HEAD(&rdp->nocb_head_rdp);
+ if (dump_tree) {
+ if (!firsttime)
+ pr_cont("%s\n", gotnocbscbs
+ ? "" : " (self only)");
+ gotnocbscbs = false;
+ firsttime = false;
+ pr_alert("%s: No-CB GP kthread CPU %d:",
+ __func__, cpu);
+ }
+ } else {
+ /* Another CB kthread, link to previous GP kthread. */
+ gotnocbscbs = true;
+ if (dump_tree)
+ pr_cont(" %d", cpu);
+ }
+ rdp->nocb_gp_rdp = rdp_gp;
+ if (cpumask_test_cpu(cpu, rcu_nocb_mask))
+ list_add_tail(&rdp->nocb_entry_rdp, &rdp_gp->nocb_head_rdp);
+ }
+ if (gotnocbs && dump_tree)
+ pr_cont("%s\n", gotnocbscbs ? "" : " (self only)");
+}
+
+/*
+ * Bind the current task to the offloaded CPUs. If there are no offloaded
+ * CPUs, leave the task unbound. Splat if the bind attempt fails.
+ */
+void rcu_bind_current_to_nocb(void)
+{
+ if (cpumask_available(rcu_nocb_mask) && !cpumask_empty(rcu_nocb_mask))
+ WARN_ON(sched_setaffinity(current->pid, rcu_nocb_mask));
+}
+EXPORT_SYMBOL_GPL(rcu_bind_current_to_nocb);
+
+// The ->on_cpu field is available only in CONFIG_SMP=y, so...
+#ifdef CONFIG_SMP
+static char *show_rcu_should_be_on_cpu(struct task_struct *tsp)
+{
+ return tsp && task_is_running(tsp) && !tsp->on_cpu ? "!" : "";
+}
+#else // #ifdef CONFIG_SMP
+static char *show_rcu_should_be_on_cpu(struct task_struct *tsp)
+{
+ return "";
+}
+#endif // #else #ifdef CONFIG_SMP
+
+/*
+ * Dump out nocb grace-period kthread state for the specified rcu_data
+ * structure.
+ */
+static void show_rcu_nocb_gp_state(struct rcu_data *rdp)
+{
+ struct rcu_node *rnp = rdp->mynode;
+
+ pr_info("nocb GP %d %c%c%c%c%c %c[%c%c] %c%c:%ld rnp %d:%d %lu %c CPU %d%s\n",
+ rdp->cpu,
+ "kK"[!!rdp->nocb_gp_kthread],
+ "lL"[raw_spin_is_locked(&rdp->nocb_gp_lock)],
+ "dD"[!!rdp->nocb_defer_wakeup],
+ "tT"[timer_pending(&rdp->nocb_timer)],
+ "sS"[!!rdp->nocb_gp_sleep],
+ ".W"[swait_active(&rdp->nocb_gp_wq)],
+ ".W"[swait_active(&rnp->nocb_gp_wq[0])],
+ ".W"[swait_active(&rnp->nocb_gp_wq[1])],
+ ".B"[!!rdp->nocb_gp_bypass],
+ ".G"[!!rdp->nocb_gp_gp],
+ (long)rdp->nocb_gp_seq,
+ rnp->grplo, rnp->grphi, READ_ONCE(rdp->nocb_gp_loops),
+ rdp->nocb_gp_kthread ? task_state_to_char(rdp->nocb_gp_kthread) : '.',
+ rdp->nocb_gp_kthread ? (int)task_cpu(rdp->nocb_gp_kthread) : -1,
+ show_rcu_should_be_on_cpu(rdp->nocb_gp_kthread));
+}
+
+/* Dump out nocb kthread state for the specified rcu_data structure. */
+static void show_rcu_nocb_state(struct rcu_data *rdp)
+{
+ char bufw[20];
+ char bufr[20];
+ struct rcu_data *nocb_next_rdp;
+ struct rcu_segcblist *rsclp = &rdp->cblist;
+ bool waslocked;
+ bool wassleep;
+
+ if (rdp->nocb_gp_rdp == rdp)
+ show_rcu_nocb_gp_state(rdp);
+
+ nocb_next_rdp = list_next_or_null_rcu(&rdp->nocb_gp_rdp->nocb_head_rdp,
+ &rdp->nocb_entry_rdp,
+ typeof(*rdp),
+ nocb_entry_rdp);
+
+ sprintf(bufw, "%ld", rsclp->gp_seq[RCU_WAIT_TAIL]);
+ sprintf(bufr, "%ld", rsclp->gp_seq[RCU_NEXT_READY_TAIL]);
+ pr_info(" CB %d^%d->%d %c%c%c%c%c%c F%ld L%ld C%d %c%c%s%c%s%c%c q%ld %c CPU %d%s\n",
+ rdp->cpu, rdp->nocb_gp_rdp->cpu,
+ nocb_next_rdp ? nocb_next_rdp->cpu : -1,
+ "kK"[!!rdp->nocb_cb_kthread],
+ "bB"[raw_spin_is_locked(&rdp->nocb_bypass_lock)],
+ "cC"[!!atomic_read(&rdp->nocb_lock_contended)],
+ "lL"[raw_spin_is_locked(&rdp->nocb_lock)],
+ "sS"[!!rdp->nocb_cb_sleep],
+ ".W"[swait_active(&rdp->nocb_cb_wq)],
+ jiffies - rdp->nocb_bypass_first,
+ jiffies - rdp->nocb_nobypass_last,
+ rdp->nocb_nobypass_count,
+ ".D"[rcu_segcblist_ready_cbs(rsclp)],
+ ".W"[!rcu_segcblist_segempty(rsclp, RCU_WAIT_TAIL)],
+ rcu_segcblist_segempty(rsclp, RCU_WAIT_TAIL) ? "" : bufw,
+ ".R"[!rcu_segcblist_segempty(rsclp, RCU_NEXT_READY_TAIL)],
+ rcu_segcblist_segempty(rsclp, RCU_NEXT_READY_TAIL) ? "" : bufr,
+ ".N"[!rcu_segcblist_segempty(rsclp, RCU_NEXT_TAIL)],
+ ".B"[!!rcu_cblist_n_cbs(&rdp->nocb_bypass)],
+ rcu_segcblist_n_cbs(&rdp->cblist),
+ rdp->nocb_cb_kthread ? task_state_to_char(rdp->nocb_cb_kthread) : '.',
+ rdp->nocb_cb_kthread ? (int)task_cpu(rdp->nocb_cb_kthread) : -1,
+ show_rcu_should_be_on_cpu(rdp->nocb_cb_kthread));
+
+ /* It is OK for GP kthreads to have GP state. */
+ if (rdp->nocb_gp_rdp == rdp)
+ return;
+
+ waslocked = raw_spin_is_locked(&rdp->nocb_gp_lock);
+ wassleep = swait_active(&rdp->nocb_gp_wq);
+ if (!rdp->nocb_gp_sleep && !waslocked && !wassleep)
+ return; /* Nothing untoward. */
+
+ pr_info(" nocb GP activity on CB-only CPU!!! %c%c%c %c\n",
+ "lL"[waslocked],
+ "dD"[!!rdp->nocb_defer_wakeup],
+ "sS"[!!rdp->nocb_gp_sleep],
+ ".W"[wassleep]);
+}
+
+#else /* #ifdef CONFIG_RCU_NOCB_CPU */
+
+static inline int rcu_lockdep_is_held_nocb(struct rcu_data *rdp)
+{
+ return 0;
+}
+
+static inline bool rcu_current_is_nocb_kthread(struct rcu_data *rdp)
+{
+ return false;
+}
+
+/* No ->nocb_lock to acquire. */
+static void rcu_nocb_lock(struct rcu_data *rdp)
+{
+}
+
+/* No ->nocb_lock to release. */
+static void rcu_nocb_unlock(struct rcu_data *rdp)
+{
+}
+
+/* No ->nocb_lock to release. */
+static void rcu_nocb_unlock_irqrestore(struct rcu_data *rdp,
+ unsigned long flags)
+{
+ local_irq_restore(flags);
+}
+
+/* Lockdep check that ->cblist may be safely accessed. */
+static void rcu_lockdep_assert_cblist_protected(struct rcu_data *rdp)
+{
+ lockdep_assert_irqs_disabled();
+}
+
+static void rcu_nocb_gp_cleanup(struct swait_queue_head *sq)
+{
+}
+
+static struct swait_queue_head *rcu_nocb_gp_get(struct rcu_node *rnp)
+{
+ return NULL;
+}
+
+static void rcu_init_one_nocb(struct rcu_node *rnp)
+{
+}
+
+static bool rcu_nocb_flush_bypass(struct rcu_data *rdp, struct rcu_head *rhp,
+ unsigned long j)
+{
+ return true;
+}
+
+static bool rcu_nocb_try_bypass(struct rcu_data *rdp, struct rcu_head *rhp,
+ bool *was_alldone, unsigned long flags)
+{
+ return false;
+}
+
+static void __call_rcu_nocb_wake(struct rcu_data *rdp, bool was_empty,
+ unsigned long flags)
+{
+ WARN_ON_ONCE(1); /* Should be dead code! */
+}
+
+static void __init rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp)
+{
+}
+
+static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp, int level)
+{
+ return false;
+}
+
+static bool do_nocb_deferred_wakeup(struct rcu_data *rdp)
+{
+ return false;
+}
+
+static void rcu_spawn_cpu_nocb_kthread(int cpu)
+{
+}
+
+static void show_rcu_nocb_state(struct rcu_data *rdp)
+{
+}
+
+#endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index c6ea81cd4189..e3142ee35fc6 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -13,10 +13,29 @@
#include "../locking/rtmutex_common.h"
-#ifdef CONFIG_RCU_NOCB_CPU
-static cpumask_var_t rcu_nocb_mask; /* CPUs to have callbacks offloaded. */
-static bool __read_mostly rcu_nocb_poll; /* Offload kthread are to poll. */
-#endif /* #ifdef CONFIG_RCU_NOCB_CPU */
+static bool rcu_rdp_is_offloaded(struct rcu_data *rdp)
+{
+ /*
+ * In order to read the offloaded state of an rdp in a safe
+ * and stable way and prevent from its value to be changed
+ * under us, we must either hold the barrier mutex, the cpu
+ * hotplug lock (read or write) or the nocb lock. Local
+ * non-preemptible reads are also safe. NOCB kthreads and
+ * timers have their own means of synchronization against the
+ * offloaded state updaters.
+ */
+ RCU_LOCKDEP_WARN(
+ !(lockdep_is_held(&rcu_state.barrier_mutex) ||
+ (IS_ENABLED(CONFIG_HOTPLUG_CPU) && lockdep_is_cpus_held()) ||
+ rcu_lockdep_is_held_nocb(rdp) ||
+ (rdp == this_cpu_ptr(&rcu_data) &&
+ !(IS_ENABLED(CONFIG_PREEMPT_COUNT) && preemptible())) ||
+ rcu_current_is_nocb_kthread(rdp)),
+ "Unsafe read of RCU_NOCB offloaded state"
+ );
+
+ return rcu_segcblist_is_offloaded(&rdp->cblist);
+}
/*
* Check the RCU kernel configuration parameters and print informative
@@ -32,10 +51,10 @@ static void __init rcu_bootup_announce_oddness(void)
RCU_FANOUT);
if (rcu_fanout_exact)
pr_info("\tHierarchical RCU autobalancing is disabled.\n");
- if (IS_ENABLED(CONFIG_RCU_FAST_NO_HZ))
- pr_info("\tRCU dyntick-idle grace-period acceleration is enabled.\n");
if (IS_ENABLED(CONFIG_PROVE_RCU))
pr_info("\tRCU lockdep checking is enabled.\n");
+ if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD))
+ pr_info("\tRCU strict (and thus non-scalable) grace periods are enabled.\n");
if (RCU_NUM_LVLS >= 4)
pr_info("\tFour(or more)-level hierarchy is enabled.\n");
if (RCU_FANOUT_LEAF != 16)
@@ -56,6 +75,8 @@ static void __init rcu_bootup_announce_oddness(void)
pr_info("\tBoot-time adjustment of callback high-water mark to %ld.\n", qhimark);
if (qlowmark != DEFAULT_RCU_QLOMARK)
pr_info("\tBoot-time adjustment of callback low-water mark to %ld.\n", qlowmark);
+ if (qovld != DEFAULT_RCU_QOVLD)
+ pr_info("\tBoot-time adjustment of callback overload level to %ld.\n", qovld);
if (jiffies_till_first_fqs != ULONG_MAX)
pr_info("\tBoot-time adjustment of first FQS scan delay to %ld jiffies.\n", jiffies_till_first_fqs);
if (jiffies_till_next_fqs != ULONG_MAX)
@@ -65,13 +86,13 @@ static void __init rcu_bootup_announce_oddness(void)
if (rcu_kick_kthreads)
pr_info("\tKick kthreads if too-long grace period.\n");
if (IS_ENABLED(CONFIG_DEBUG_OBJECTS_RCU_HEAD))
- pr_info("\tRCU callback double-/use-after-free debug enabled.\n");
+ pr_info("\tRCU callback double-/use-after-free debug is enabled.\n");
if (gp_preinit_delay)
pr_info("\tRCU debug GP pre-init slowdown %d jiffies.\n", gp_preinit_delay);
if (gp_init_delay)
pr_info("\tRCU debug GP init slowdown %d jiffies.\n", gp_init_delay);
if (gp_cleanup_delay)
- pr_info("\tRCU debug GP init slowdown %d jiffies.\n", gp_cleanup_delay);
+ pr_info("\tRCU debug GP cleanup slowdown %d jiffies.\n", gp_cleanup_delay);
if (!use_softirq)
pr_info("\tRCU_SOFTIRQ processing moved to rcuc kthreads.\n");
if (IS_ENABLED(CONFIG_RCU_EQS_DEBUG))
@@ -224,7 +245,7 @@ static void rcu_preempt_ctxt_queue(struct rcu_node *rnp, struct rcu_data *rdp)
WARN_ON_ONCE(rnp->completedqs == rnp->gp_seq);
}
if (!rnp->exp_tasks && (blkd_state & RCU_EXP_BLKD))
- rnp->exp_tasks = &t->rcu_node_entry;
+ WRITE_ONCE(rnp->exp_tasks, &t->rcu_node_entry);
WARN_ON_ONCE(!(blkd_state & RCU_GP_BLKD) !=
!(rnp->qsmask & rdp->grpmask));
WARN_ON_ONCE(!(blkd_state & RCU_EXP_BLKD) !=
@@ -237,10 +258,10 @@ static void rcu_preempt_ctxt_queue(struct rcu_node *rnp, struct rcu_data *rdp)
* no need to check for a subsequent expedited GP. (Though we are
* still in a quiescent state in any case.)
*/
- if (blkd_state & RCU_EXP_BLKD && rdp->exp_deferred_qs)
+ if (blkd_state & RCU_EXP_BLKD && rdp->cpu_no_qs.b.exp)
rcu_report_exp_rdp(rdp);
else
- WARN_ON_ONCE(rdp->exp_deferred_qs);
+ WARN_ON_ONCE(rdp->cpu_no_qs.b.exp);
}
/*
@@ -254,12 +275,16 @@ static void rcu_preempt_ctxt_queue(struct rcu_node *rnp, struct rcu_data *rdp)
* current task, there might be any number of other tasks blocked while
* in an RCU read-side critical section.
*
+ * Unlike non-preemptible-RCU, quiescent state reports for expedited
+ * grace periods are handled separately via deferred quiescent states
+ * and context switch events.
+ *
* Callers to this function must disable preemption.
*/
static void rcu_qs(void)
{
RCU_LOCKDEP_WARN(preemptible(), "rcu_qs() invoked with preemption enabled!!!\n");
- if (__this_cpu_read(rcu_data.cpu_no_qs.s)) {
+ if (__this_cpu_read(rcu_data.cpu_no_qs.b.norm)) {
trace_rcu_grace_period(TPS("rcu_preempt"),
__this_cpu_read(rcu_data.gp_seq),
TPS("cpuqs"));
@@ -290,7 +315,7 @@ void rcu_note_context_switch(bool preempt)
trace_rcu_utilization(TPS("Start context switch"));
lockdep_assert_irqs_disabled();
- WARN_ON_ONCE(!preempt && rcu_preempt_depth() > 0);
+ WARN_ONCE(!preempt && rcu_preempt_depth() > 0, "Voluntary context switch within RCU read-side critical section!");
if (rcu_preempt_depth() > 0 &&
!t->rcu_read_unlock_special.b.blocked) {
@@ -305,7 +330,7 @@ void rcu_note_context_switch(bool preempt)
* then queue the task as required based on the states
* of any ongoing and expedited grace periods.
*/
- WARN_ON_ONCE((rdp->grpmask & rcu_rnp_online_cpus(rnp)) == 0);
+ WARN_ON_ONCE(!rcu_rdp_cpu_online(rdp));
WARN_ON_ONCE(!list_empty(&t->rcu_node_entry));
trace_rcu_preempt_task(rcu_state.name,
t->pid,
@@ -327,8 +352,9 @@ void rcu_note_context_switch(bool preempt)
* means that we continue to block the current grace period.
*/
rcu_qs();
- if (rdp->exp_deferred_qs)
+ if (rdp->cpu_no_qs.b.exp)
rcu_report_exp_rdp(rdp);
+ rcu_tasks_qs(current, preempt);
trace_rcu_utilization(TPS("End context switch"));
}
EXPORT_SYMBOL_GPL(rcu_note_context_switch);
@@ -343,24 +369,25 @@ static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp)
return READ_ONCE(rnp->gp_tasks) != NULL;
}
-/* Bias and limit values for ->rcu_read_lock_nesting. */
-#define RCU_NEST_BIAS INT_MAX
-#define RCU_NEST_NMAX (-INT_MAX / 2)
+/* limit value for ->rcu_read_lock_nesting. */
#define RCU_NEST_PMAX (INT_MAX / 2)
static void rcu_preempt_read_enter(void)
{
- current->rcu_read_lock_nesting++;
+ WRITE_ONCE(current->rcu_read_lock_nesting, READ_ONCE(current->rcu_read_lock_nesting) + 1);
}
-static void rcu_preempt_read_exit(void)
+static int rcu_preempt_read_exit(void)
{
- current->rcu_read_lock_nesting--;
+ int ret = READ_ONCE(current->rcu_read_lock_nesting) - 1;
+
+ WRITE_ONCE(current->rcu_read_lock_nesting, ret);
+ return ret;
}
static void rcu_preempt_depth_set(int val)
{
- current->rcu_read_lock_nesting = val;
+ WRITE_ONCE(current->rcu_read_lock_nesting, val);
}
/*
@@ -373,6 +400,8 @@ void __rcu_read_lock(void)
rcu_preempt_read_enter();
if (IS_ENABLED(CONFIG_PROVE_LOCKING))
WARN_ON_ONCE(rcu_preempt_depth() > RCU_NEST_PMAX);
+ if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD) && rcu_state.gp_kthread)
+ WRITE_ONCE(current->rcu_read_unlock_special.b.need_qs, true);
barrier(); /* critical section after entry code. */
}
EXPORT_SYMBOL_GPL(__rcu_read_lock);
@@ -388,21 +417,16 @@ void __rcu_read_unlock(void)
{
struct task_struct *t = current;
- if (rcu_preempt_depth() != 1) {
- rcu_preempt_read_exit();
- } else {
- barrier(); /* critical section before exit code. */
- rcu_preempt_depth_set(-RCU_NEST_BIAS);
- barrier(); /* assign before ->rcu_read_unlock_special load */
+ barrier(); // critical section before exit code.
+ if (rcu_preempt_read_exit() == 0) {
+ barrier(); // critical-section exit before .s check.
if (unlikely(READ_ONCE(t->rcu_read_unlock_special.s)))
rcu_read_unlock_special(t);
- barrier(); /* ->rcu_read_unlock_special load before assign */
- rcu_preempt_depth_set(0);
}
if (IS_ENABLED(CONFIG_PROVE_LOCKING)) {
int rrln = rcu_preempt_depth();
- WARN_ON_ONCE(rrln < 0 && rrln > RCU_NEST_NMAX);
+ WARN_ON_ONCE(rrln < 0 || rrln > RCU_NEST_PMAX);
}
}
EXPORT_SYMBOL_GPL(__rcu_read_unlock);
@@ -436,7 +460,7 @@ static bool rcu_preempt_has_tasks(struct rcu_node *rnp)
* be quite short, for example, in the case of the call from
* rcu_read_unlock_special().
*/
-static void
+static notrace void
rcu_preempt_deferred_qs_irqrestore(struct task_struct *t, unsigned long flags)
{
bool empty_exp;
@@ -455,13 +479,20 @@ rcu_preempt_deferred_qs_irqrestore(struct task_struct *t, unsigned long flags)
*/
special = t->rcu_read_unlock_special;
rdp = this_cpu_ptr(&rcu_data);
- if (!special.s && !rdp->exp_deferred_qs) {
+ if (!special.s && !rdp->cpu_no_qs.b.exp) {
local_irq_restore(flags);
return;
}
t->rcu_read_unlock_special.s = 0;
- if (special.b.need_qs)
- rcu_qs();
+ if (special.b.need_qs) {
+ if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD)) {
+ rdp->cpu_no_qs.b.norm = false;
+ rcu_report_qs_rdp(rdp);
+ udelay(rcu_unlock_delay);
+ } else {
+ rcu_qs();
+ }
+ }
/*
* Respond to a request by an expedited grace period for a
@@ -469,7 +500,7 @@ rcu_preempt_deferred_qs_irqrestore(struct task_struct *t, unsigned long flags)
* tasks are handled when removing the task from the
* blocked-tasks list below.
*/
- if (rdp->exp_deferred_qs)
+ if (rdp->cpu_no_qs.b.exp)
rcu_report_exp_rdp(rdp);
/* Clean up if blocked during RCU read-side critical section. */
@@ -498,12 +529,12 @@ rcu_preempt_deferred_qs_irqrestore(struct task_struct *t, unsigned long flags)
if (&t->rcu_node_entry == rnp->gp_tasks)
WRITE_ONCE(rnp->gp_tasks, np);
if (&t->rcu_node_entry == rnp->exp_tasks)
- rnp->exp_tasks = np;
+ WRITE_ONCE(rnp->exp_tasks, np);
if (IS_ENABLED(CONFIG_RCU_BOOST)) {
/* Snapshot ->boost_mtx ownership w/rnp->lock held. */
- drop_boost_mutex = rt_mutex_owner(&rnp->boost_mtx) == t;
+ drop_boost_mutex = rt_mutex_owner(&rnp->boost_mtx.rtmutex) == t;
if (&t->rcu_node_entry == rnp->boost_tasks)
- rnp->boost_tasks = np;
+ WRITE_ONCE(rnp->boost_tasks, np);
}
/*
@@ -526,16 +557,16 @@ rcu_preempt_deferred_qs_irqrestore(struct task_struct *t, unsigned long flags)
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
}
- /* Unboost if we were boosted. */
- if (IS_ENABLED(CONFIG_RCU_BOOST) && drop_boost_mutex)
- rt_mutex_futex_unlock(&rnp->boost_mtx);
-
/*
* If this was the last task on the expedited lists,
* then we need to report up the rcu_node hierarchy.
*/
if (!empty_exp && empty_exp_now)
rcu_report_exp_rnp(rnp, true);
+
+ /* Unboost if we were boosted. */
+ if (IS_ENABLED(CONFIG_RCU_BOOST) && drop_boost_mutex)
+ rt_mutex_futex_unlock(&rnp->boost_mtx.rtmutex);
} else {
local_irq_restore(flags);
}
@@ -550,11 +581,11 @@ rcu_preempt_deferred_qs_irqrestore(struct task_struct *t, unsigned long flags)
* is disabled. This function cannot be expected to understand these
* nuances, so the caller must handle them.
*/
-static bool rcu_preempt_need_deferred_qs(struct task_struct *t)
+static notrace bool rcu_preempt_need_deferred_qs(struct task_struct *t)
{
- return (__this_cpu_read(rcu_data.exp_deferred_qs) ||
+ return (__this_cpu_read(rcu_data.cpu_no_qs.b.exp) ||
READ_ONCE(t->rcu_read_unlock_special.s)) &&
- rcu_preempt_depth() <= 0;
+ rcu_preempt_depth() == 0;
}
/*
@@ -564,19 +595,14 @@ static bool rcu_preempt_need_deferred_qs(struct task_struct *t)
* evaluate safety in terms of interrupt, softirq, and preemption
* disabling.
*/
-static void rcu_preempt_deferred_qs(struct task_struct *t)
+notrace void rcu_preempt_deferred_qs(struct task_struct *t)
{
unsigned long flags;
- bool couldrecurse = rcu_preempt_depth() >= 0;
if (!rcu_preempt_need_deferred_qs(t))
return;
- if (couldrecurse)
- rcu_preempt_depth_set(rcu_preempt_depth() - RCU_NEST_BIAS);
local_irq_save(flags);
rcu_preempt_deferred_qs_irqrestore(t, flags);
- if (couldrecurse)
- rcu_preempt_depth_set(rcu_preempt_depth() + RCU_NEST_BIAS);
}
/*
@@ -598,9 +624,9 @@ static void rcu_preempt_deferred_qs_handler(struct irq_work *iwp)
static void rcu_read_unlock_special(struct task_struct *t)
{
unsigned long flags;
+ bool irqs_were_disabled;
bool preempt_bh_were_disabled =
!!(preempt_count() & (PREEMPT_MASK | SOFTIRQ_MASK));
- bool irqs_were_disabled;
/* NMI handlers cannot block and cannot safely manipulate state. */
if (in_nmi())
@@ -609,36 +635,44 @@ static void rcu_read_unlock_special(struct task_struct *t)
local_irq_save(flags);
irqs_were_disabled = irqs_disabled_flags(flags);
if (preempt_bh_were_disabled || irqs_were_disabled) {
- bool exp;
+ bool expboost; // Expedited GP in flight or possible boosting.
struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
struct rcu_node *rnp = rdp->mynode;
- exp = (t->rcu_blocked_node && t->rcu_blocked_node->exp_tasks) ||
- (rdp->grpmask & READ_ONCE(rnp->expmask)) ||
- tick_nohz_full_cpu(rdp->cpu);
+ expboost = (t->rcu_blocked_node && READ_ONCE(t->rcu_blocked_node->exp_tasks)) ||
+ (rdp->grpmask & READ_ONCE(rnp->expmask)) ||
+ (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD) &&
+ ((rdp->grpmask & READ_ONCE(rnp->qsmask)) || t->rcu_blocked_node)) ||
+ (IS_ENABLED(CONFIG_RCU_BOOST) && irqs_were_disabled &&
+ t->rcu_blocked_node);
// Need to defer quiescent state until everything is enabled.
- if (irqs_were_disabled && use_softirq &&
- (in_interrupt() ||
- (exp && !t->rcu_read_unlock_special.b.deferred_qs))) {
- // Using softirq, safe to awaken, and we get
- // no help from enabling irqs, unlike bh/preempt.
+ if (use_softirq && (in_hardirq() || (expboost && !irqs_were_disabled))) {
+ // Using softirq, safe to awaken, and either the
+ // wakeup is free or there is either an expedited
+ // GP in flight or a potential need to deboost.
raise_softirq_irqoff(RCU_SOFTIRQ);
} else {
// Enabling BH or preempt does reschedule, so...
- // Also if no expediting or NO_HZ_FULL, slow is OK.
+ // Also if no expediting and no possible deboosting,
+ // slow is OK. Plus nohz_full CPUs eventually get
+ // tick enabled.
set_tsk_need_resched(current);
set_preempt_need_resched();
if (IS_ENABLED(CONFIG_IRQ_WORK) && irqs_were_disabled &&
- !rdp->defer_qs_iw_pending && exp) {
+ expboost && !rdp->defer_qs_iw_pending && cpu_online(rdp->cpu)) {
// Get scheduler to re-evaluate and call hooks.
// If !IRQ_WORK, FQS scan will eventually IPI.
- init_irq_work(&rdp->defer_qs_iw,
- rcu_preempt_deferred_qs_handler);
+ if (IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD) &&
+ IS_ENABLED(CONFIG_PREEMPT_RT))
+ rdp->defer_qs_iw = IRQ_WORK_INIT_HARD(
+ rcu_preempt_deferred_qs_handler);
+ else
+ init_irq_work(&rdp->defer_qs_iw,
+ rcu_preempt_deferred_qs_handler);
rdp->defer_qs_iw_pending = true;
irq_work_queue_on(&rdp->defer_qs_iw, rdp->cpu);
}
}
- t->rcu_read_unlock_special.b.deferred_qs = true;
local_irq_restore(flags);
return;
}
@@ -684,9 +718,7 @@ static void rcu_flavor_sched_clock_irq(int user)
{
struct task_struct *t = current;
- if (user || rcu_is_cpu_rrupt_from_idle()) {
- rcu_note_voluntary_context_switch(current);
- }
+ lockdep_assert_irqs_disabled();
if (rcu_preempt_depth() > 0 ||
(preempt_count() & (PREEMPT_MASK | SOFTIRQ_MASK))) {
/* No QS, force context switch if deferred. */
@@ -697,7 +729,7 @@ static void rcu_flavor_sched_clock_irq(int user)
} else if (rcu_preempt_need_deferred_qs(t)) {
rcu_preempt_deferred_qs(t); /* Report deferred QS. */
return;
- } else if (!rcu_preempt_depth()) {
+ } else if (!WARN_ON_ONCE(rcu_preempt_depth())) {
rcu_qs(); /* Report immediate QS. */
return;
}
@@ -746,20 +778,19 @@ dump_blkd_tasks(struct rcu_node *rnp, int ncheck)
int cpu;
int i;
struct list_head *lhp;
- bool onl;
struct rcu_data *rdp;
struct rcu_node *rnp1;
raw_lockdep_assert_held_rcu_node(rnp);
pr_info("%s: grp: %d-%d level: %d ->gp_seq %ld ->completedqs %ld\n",
__func__, rnp->grplo, rnp->grphi, rnp->level,
- (long)rnp->gp_seq, (long)rnp->completedqs);
+ (long)READ_ONCE(rnp->gp_seq), (long)rnp->completedqs);
for (rnp1 = rnp; rnp1; rnp1 = rnp1->parent)
pr_info("%s: %d:%d ->qsmask %#lx ->qsmaskinit %#lx ->qsmaskinitnext %#lx\n",
__func__, rnp1->grplo, rnp1->grphi, rnp1->qsmask, rnp1->qsmaskinit, rnp1->qsmaskinitnext);
pr_info("%s: ->gp_tasks %p ->boost_tasks %p ->exp_tasks %p\n",
- __func__, READ_ONCE(rnp->gp_tasks), rnp->boost_tasks,
- rnp->exp_tasks);
+ __func__, READ_ONCE(rnp->gp_tasks), data_race(rnp->boost_tasks),
+ READ_ONCE(rnp->exp_tasks));
pr_info("%s: ->blkd_tasks", __func__);
i = 0;
list_for_each(lhp, &rnp->blkd_tasks) {
@@ -770,9 +801,8 @@ dump_blkd_tasks(struct rcu_node *rnp, int ncheck)
pr_cont("\n");
for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++) {
rdp = per_cpu_ptr(&rcu_data, cpu);
- onl = !!(rdp->grpmask & rcu_rnp_online_cpus(rnp));
pr_info("\t%d: %c online: %ld(%d) offline: %ld(%d)\n",
- cpu, ".o"[onl],
+ cpu, ".o"[rcu_rdp_cpu_online(rdp)],
(long)rdp->rcu_onl_gp_seq, rdp->rcu_onl_gp_flags,
(long)rdp->rcu_ofl_gp_seq, rdp->rcu_ofl_gp_flags);
}
@@ -781,6 +811,24 @@ dump_blkd_tasks(struct rcu_node *rnp, int ncheck)
#else /* #ifdef CONFIG_PREEMPT_RCU */
/*
+ * If strict grace periods are enabled, and if the calling
+ * __rcu_read_unlock() marks the beginning of a quiescent state, immediately
+ * report that quiescent state and, if requested, spin for a bit.
+ */
+void rcu_read_unlock_strict(void)
+{
+ struct rcu_data *rdp;
+
+ if (irqs_disabled() || preempt_count() || !rcu_state.gp_kthread)
+ return;
+ rdp = this_cpu_ptr(&rcu_data);
+ rdp->cpu_no_qs.b.norm = false;
+ rcu_report_qs_rdp(rdp);
+ udelay(rcu_unlock_delay);
+}
+EXPORT_SYMBOL_GPL(rcu_read_unlock_strict);
+
+/*
* Tell them what RCU they are running.
*/
static void __init rcu_bootup_announce(void)
@@ -803,10 +851,8 @@ static void rcu_qs(void)
trace_rcu_grace_period(TPS("rcu_sched"),
__this_cpu_read(rcu_data.gp_seq), TPS("cpuqs"));
__this_cpu_write(rcu_data.cpu_no_qs.b.norm, false);
- if (!__this_cpu_read(rcu_data.cpu_no_qs.b.exp))
- return;
- __this_cpu_write(rcu_data.cpu_no_qs.b.exp, false);
- rcu_report_exp_rdp(this_cpu_ptr(&rcu_data));
+ if (__this_cpu_read(rcu_data.cpu_no_qs.b.exp))
+ rcu_report_exp_rdp(this_cpu_ptr(&rcu_data));
}
/*
@@ -822,7 +868,7 @@ void rcu_all_qs(void)
if (!raw_cpu_read(rcu_data.rcu_urgent_qs))
return;
- preempt_disable();
+ preempt_disable(); // For CONFIG_PREEMPT_COUNT=y kernels
/* Load rcu_urgent_qs before other flags. */
if (!smp_load_acquire(this_cpu_ptr(&rcu_data.rcu_urgent_qs))) {
preempt_enable();
@@ -852,9 +898,8 @@ void rcu_note_context_switch(bool preempt)
this_cpu_write(rcu_data.rcu_urgent_qs, false);
if (unlikely(raw_cpu_read(rcu_data.rcu_need_heavy_qs)))
rcu_momentary_dyntick_idle();
- if (!preempt)
- rcu_tasks_qs(current);
out:
+ rcu_tasks_qs(current, preempt);
trace_rcu_utilization(TPS("End context switch"));
}
EXPORT_SYMBOL_GPL(rcu_note_context_switch);
@@ -880,11 +925,25 @@ static bool rcu_preempt_has_tasks(struct rcu_node *rnp)
* Because there is no preemptible RCU, there can be no deferred quiescent
* states.
*/
-static bool rcu_preempt_need_deferred_qs(struct task_struct *t)
+static notrace bool rcu_preempt_need_deferred_qs(struct task_struct *t)
{
return false;
}
-static void rcu_preempt_deferred_qs(struct task_struct *t) { }
+
+// Except that we do need to respond to a request by an expedited
+// grace period for a quiescent state from this CPU. Note that in
+// non-preemptible kernels, there can be no context switches within RCU
+// read-side critical sections, which in turn means that the leaf rcu_node
+// structure's blocked-tasks list is always empty. is therefore no need to
+// actually check it. Instead, a quiescent state from this CPU suffices,
+// and this function is only called from such a quiescent state.
+notrace void rcu_preempt_deferred_qs(struct task_struct *t)
+{
+ struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
+
+ if (rdp->cpu_no_qs.b.exp)
+ rcu_report_exp_rdp(rdp);
+}
/*
* Because there is no preemptible RCU, there can be no readers blocked,
@@ -915,7 +974,6 @@ static void rcu_flavor_sched_clock_irq(int user)
* neither access nor modify, at least not while the
* corresponding CPU is online.
*/
-
rcu_qs();
}
}
@@ -944,12 +1002,34 @@ dump_blkd_tasks(struct rcu_node *rnp, int ncheck)
*/
static void rcu_cpu_kthread_setup(unsigned int cpu)
{
+ struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
#ifdef CONFIG_RCU_BOOST
struct sched_param sp;
sp.sched_priority = kthread_prio;
sched_setscheduler_nocheck(current, SCHED_FIFO, &sp);
#endif /* #ifdef CONFIG_RCU_BOOST */
+
+ WRITE_ONCE(rdp->rcuc_activity, jiffies);
+}
+
+static bool rcu_is_callbacks_nocb_kthread(struct rcu_data *rdp)
+{
+#ifdef CONFIG_RCU_NOCB_CPU
+ return rdp->nocb_cb_kthread == current;
+#else
+ return false;
+#endif
+}
+
+/*
+ * Is the current CPU running the RCU-callbacks kthread?
+ * Caller must have preemption disabled.
+ */
+static bool rcu_is_callbacks_kthread(struct rcu_data *rdp)
+{
+ return rdp->rcu_cpu_kthread_task == current ||
+ rcu_is_callbacks_nocb_kthread(rdp);
}
#ifdef CONFIG_RCU_BOOST
@@ -1011,11 +1091,12 @@ static int rcu_boost(struct rcu_node *rnp)
* section.
*/
t = container_of(tb, struct task_struct, rcu_node_entry);
- rt_mutex_init_proxy_locked(&rnp->boost_mtx, t);
+ rt_mutex_init_proxy_locked(&rnp->boost_mtx.rtmutex, t);
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
/* Lock only for side effect: boosts task t's priority. */
rt_mutex_lock(&rnp->boost_mtx);
rt_mutex_unlock(&rnp->boost_mtx); /* Then keep lockdep happy. */
+ rnp->n_boosts++;
return READ_ONCE(rnp->exp_tasks) != NULL ||
READ_ONCE(rnp->boost_tasks) != NULL;
@@ -1032,20 +1113,21 @@ static int rcu_boost_kthread(void *arg)
trace_rcu_utilization(TPS("Start boost kthread@init"));
for (;;) {
- rnp->boost_kthread_status = RCU_KTHREAD_WAITING;
+ WRITE_ONCE(rnp->boost_kthread_status, RCU_KTHREAD_WAITING);
trace_rcu_utilization(TPS("End boost kthread@rcu_wait"));
- rcu_wait(rnp->boost_tasks || rnp->exp_tasks);
+ rcu_wait(READ_ONCE(rnp->boost_tasks) ||
+ READ_ONCE(rnp->exp_tasks));
trace_rcu_utilization(TPS("Start boost kthread@rcu_wait"));
- rnp->boost_kthread_status = RCU_KTHREAD_RUNNING;
+ WRITE_ONCE(rnp->boost_kthread_status, RCU_KTHREAD_RUNNING);
more2boost = rcu_boost(rnp);
if (more2boost)
spincnt++;
else
spincnt = 0;
if (spincnt > 10) {
- rnp->boost_kthread_status = RCU_KTHREAD_YIELDING;
+ WRITE_ONCE(rnp->boost_kthread_status, RCU_KTHREAD_YIELDING);
trace_rcu_utilization(TPS("End boost kthread@rcu_yield"));
- schedule_timeout_interruptible(2);
+ schedule_timeout_idle(2);
trace_rcu_utilization(TPS("Start boost kthread@rcu_yield"));
spincnt = 0;
}
@@ -1069,7 +1151,8 @@ static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags)
__releases(rnp->lock)
{
raw_lockdep_assert_held_rcu_node(rnp);
- if (!rcu_preempt_blocked_readers_cgp(rnp) && rnp->exp_tasks == NULL) {
+ if (!rnp->boost_kthread_task ||
+ (!rcu_preempt_blocked_readers_cgp(rnp) && !rnp->exp_tasks)) {
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
return;
}
@@ -1077,26 +1160,18 @@ static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags)
(rnp->gp_tasks != NULL &&
rnp->boost_tasks == NULL &&
rnp->qsmask == 0 &&
- ULONG_CMP_GE(jiffies, rnp->boost_time))) {
+ (!time_after(rnp->boost_time, jiffies) || rcu_state.cbovld ||
+ IS_ENABLED(CONFIG_RCU_STRICT_GRACE_PERIOD)))) {
if (rnp->exp_tasks == NULL)
- rnp->boost_tasks = rnp->gp_tasks;
+ WRITE_ONCE(rnp->boost_tasks, rnp->gp_tasks);
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
rcu_wake_cond(rnp->boost_kthread_task,
- rnp->boost_kthread_status);
+ READ_ONCE(rnp->boost_kthread_status));
} else {
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
}
}
-/*
- * Is the current CPU running the RCU-callbacks kthread?
- * Caller must have preemption disabled.
- */
-static bool rcu_is_callbacks_kthread(void)
-{
- return __this_cpu_read(rcu_data.rcu_cpu_kthread_task) == current;
-}
-
#define RCU_BOOST_DELAY_JIFFIES DIV_ROUND_UP(CONFIG_RCU_BOOST_DELAY * HZ, 1000)
/*
@@ -1110,30 +1185,22 @@ static void rcu_preempt_boost_start_gp(struct rcu_node *rnp)
/*
* Create an RCU-boost kthread for the specified node if one does not
* already exist. We only create this kthread for preemptible RCU.
- * Returns zero if all is well, a negated errno otherwise.
*/
static void rcu_spawn_one_boost_kthread(struct rcu_node *rnp)
{
- int rnp_index = rnp - rcu_get_root();
unsigned long flags;
+ int rnp_index = rnp - rcu_get_root();
struct sched_param sp;
struct task_struct *t;
- if (!IS_ENABLED(CONFIG_PREEMPT_RCU))
- return;
-
- if (!rcu_scheduler_fully_active || rcu_rnp_online_cpus(rnp) == 0)
- return;
-
- rcu_state.boost = 1;
-
- if (rnp->boost_kthread_task != NULL)
- return;
+ mutex_lock(&rnp->boost_kthread_mutex);
+ if (rnp->boost_kthread_task || !rcu_scheduler_fully_active)
+ goto out;
t = kthread_create(rcu_boost_kthread, (void *)rnp,
"rcub/%d", rnp_index);
if (WARN_ON_ONCE(IS_ERR(t)))
- return;
+ goto out;
raw_spin_lock_irqsave_rcu_node(rnp, flags);
rnp->boost_kthread_task = t;
@@ -1141,6 +1208,9 @@ static void rcu_spawn_one_boost_kthread(struct rcu_node *rnp)
sp.sched_priority = kthread_prio;
sched_setscheduler_nocheck(t, SCHED_FIFO, &sp);
wake_up_process(t); /* get to TASK_INTERRUPTIBLE quickly. */
+
+ out:
+ mutex_unlock(&rnp->boost_kthread_mutex);
}
/*
@@ -1163,37 +1233,22 @@ static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu)
return;
if (!zalloc_cpumask_var(&cm, GFP_KERNEL))
return;
+ mutex_lock(&rnp->boost_kthread_mutex);
for_each_leaf_node_possible_cpu(rnp, cpu)
if ((mask & leaf_node_cpu_bit(rnp, cpu)) &&
cpu != outgoingcpu)
cpumask_set_cpu(cpu, cm);
- if (cpumask_weight(cm) == 0)
- cpumask_setall(cm);
+ cpumask_and(cm, cm, housekeeping_cpumask(HK_TYPE_RCU));
+ if (cpumask_empty(cm)) {
+ cpumask_copy(cm, housekeeping_cpumask(HK_TYPE_RCU));
+ if (outgoingcpu >= 0)
+ cpumask_clear_cpu(outgoingcpu, cm);
+ }
set_cpus_allowed_ptr(t, cm);
+ mutex_unlock(&rnp->boost_kthread_mutex);
free_cpumask_var(cm);
}
-/*
- * Spawn boost kthreads -- called as soon as the scheduler is running.
- */
-static void __init rcu_spawn_boost_kthreads(void)
-{
- struct rcu_node *rnp;
-
- rcu_for_each_leaf_node(rnp)
- rcu_spawn_one_boost_kthread(rnp);
-}
-
-static void rcu_prepare_kthreads(int cpu)
-{
- struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
- struct rcu_node *rnp = rdp->mynode;
-
- /* Fire up the incoming CPU's kthread and leaf rcu_node kthread. */
- if (rcu_scheduler_fully_active)
- rcu_spawn_one_boost_kthread(rnp);
-}
-
#else /* #ifdef CONFIG_RCU_BOOST */
static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags)
@@ -1202,1319 +1257,20 @@ static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags)
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
}
-static bool rcu_is_callbacks_kthread(void)
-{
- return false;
-}
-
static void rcu_preempt_boost_start_gp(struct rcu_node *rnp)
{
}
-static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu)
-{
-}
-
-static void __init rcu_spawn_boost_kthreads(void)
+static void rcu_spawn_one_boost_kthread(struct rcu_node *rnp)
{
}
-static void rcu_prepare_kthreads(int cpu)
+static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu)
{
}
#endif /* #else #ifdef CONFIG_RCU_BOOST */
-#if !defined(CONFIG_RCU_FAST_NO_HZ)
-
-/*
- * Check to see if any future non-offloaded RCU-related work will need
- * to be done by the current CPU, even if none need be done immediately,
- * returning 1 if so. This function is part of the RCU implementation;
- * it is -not- an exported member of the RCU API.
- *
- * Because we not have RCU_FAST_NO_HZ, just check whether or not this
- * CPU has RCU callbacks queued.
- */
-int rcu_needs_cpu(u64 basemono, u64 *nextevt)
-{
- *nextevt = KTIME_MAX;
- return !rcu_segcblist_empty(&this_cpu_ptr(&rcu_data)->cblist) &&
- !rcu_segcblist_is_offloaded(&this_cpu_ptr(&rcu_data)->cblist);
-}
-
-/*
- * Because we do not have RCU_FAST_NO_HZ, don't bother cleaning up
- * after it.
- */
-static void rcu_cleanup_after_idle(void)
-{
-}
-
-/*
- * Do the idle-entry grace-period work, which, because CONFIG_RCU_FAST_NO_HZ=n,
- * is nothing.
- */
-static void rcu_prepare_for_idle(void)
-{
-}
-
-#else /* #if !defined(CONFIG_RCU_FAST_NO_HZ) */
-
-/*
- * This code is invoked when a CPU goes idle, at which point we want
- * to have the CPU do everything required for RCU so that it can enter
- * the energy-efficient dyntick-idle mode.
- *
- * The following preprocessor symbol controls this:
- *
- * RCU_IDLE_GP_DELAY gives the number of jiffies that a CPU is permitted
- * to sleep in dyntick-idle mode with RCU callbacks pending. This
- * is sized to be roughly one RCU grace period. Those energy-efficiency
- * benchmarkers who might otherwise be tempted to set this to a large
- * number, be warned: Setting RCU_IDLE_GP_DELAY too high can hang your
- * system. And if you are -that- concerned about energy efficiency,
- * just power the system down and be done with it!
- *
- * The value below works well in practice. If future workloads require
- * adjustment, they can be converted into kernel config parameters, though
- * making the state machine smarter might be a better option.
- */
-#define RCU_IDLE_GP_DELAY 4 /* Roughly one grace period. */
-
-static int rcu_idle_gp_delay = RCU_IDLE_GP_DELAY;
-module_param(rcu_idle_gp_delay, int, 0644);
-
-/*
- * Try to advance callbacks on the current CPU, but only if it has been
- * awhile since the last time we did so. Afterwards, if there are any
- * callbacks ready for immediate invocation, return true.
- */
-static bool __maybe_unused rcu_try_advance_all_cbs(void)
-{
- bool cbs_ready = false;
- struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
- struct rcu_node *rnp;
-
- /* Exit early if we advanced recently. */
- if (jiffies == rdp->last_advance_all)
- return false;
- rdp->last_advance_all = jiffies;
-
- rnp = rdp->mynode;
-
- /*
- * Don't bother checking unless a grace period has
- * completed since we last checked and there are
- * callbacks not yet ready to invoke.
- */
- if ((rcu_seq_completed_gp(rdp->gp_seq,
- rcu_seq_current(&rnp->gp_seq)) ||
- unlikely(READ_ONCE(rdp->gpwrap))) &&
- rcu_segcblist_pend_cbs(&rdp->cblist))
- note_gp_changes(rdp);
-
- if (rcu_segcblist_ready_cbs(&rdp->cblist))
- cbs_ready = true;
- return cbs_ready;
-}
-
-/*
- * Allow the CPU to enter dyntick-idle mode unless it has callbacks ready
- * to invoke. If the CPU has callbacks, try to advance them. Tell the
- * caller about what to set the timeout.
- *
- * The caller must have disabled interrupts.
- */
-int rcu_needs_cpu(u64 basemono, u64 *nextevt)
-{
- struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
- unsigned long dj;
-
- lockdep_assert_irqs_disabled();
-
- /* If no non-offloaded callbacks, RCU doesn't need the CPU. */
- if (rcu_segcblist_empty(&rdp->cblist) ||
- rcu_segcblist_is_offloaded(&this_cpu_ptr(&rcu_data)->cblist)) {
- *nextevt = KTIME_MAX;
- return 0;
- }
-
- /* Attempt to advance callbacks. */
- if (rcu_try_advance_all_cbs()) {
- /* Some ready to invoke, so initiate later invocation. */
- invoke_rcu_core();
- return 1;
- }
- rdp->last_accelerate = jiffies;
-
- /* Request timer and round. */
- dj = round_up(rcu_idle_gp_delay + jiffies, rcu_idle_gp_delay) - jiffies;
-
- *nextevt = basemono + dj * TICK_NSEC;
- return 0;
-}
-
-/*
- * Prepare a CPU for idle from an RCU perspective. The first major task is to
- * sense whether nohz mode has been enabled or disabled via sysfs. The second
- * major task is to accelerate (that is, assign grace-period numbers to) any
- * recently arrived callbacks.
- *
- * The caller must have disabled interrupts.
- */
-static void rcu_prepare_for_idle(void)
-{
- bool needwake;
- struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
- struct rcu_node *rnp;
- int tne;
-
- lockdep_assert_irqs_disabled();
- if (rcu_segcblist_is_offloaded(&rdp->cblist))
- return;
-
- /* Handle nohz enablement switches conservatively. */
- tne = READ_ONCE(tick_nohz_active);
- if (tne != rdp->tick_nohz_enabled_snap) {
- if (!rcu_segcblist_empty(&rdp->cblist))
- invoke_rcu_core(); /* force nohz to see update. */
- rdp->tick_nohz_enabled_snap = tne;
- return;
- }
- if (!tne)
- return;
-
- /*
- * If we have not yet accelerated this jiffy, accelerate all
- * callbacks on this CPU.
- */
- if (rdp->last_accelerate == jiffies)
- return;
- rdp->last_accelerate = jiffies;
- if (rcu_segcblist_pend_cbs(&rdp->cblist)) {
- rnp = rdp->mynode;
- raw_spin_lock_rcu_node(rnp); /* irqs already disabled. */
- needwake = rcu_accelerate_cbs(rnp, rdp);
- raw_spin_unlock_rcu_node(rnp); /* irqs remain disabled. */
- if (needwake)
- rcu_gp_kthread_wake();
- }
-}
-
-/*
- * Clean up for exit from idle. Attempt to advance callbacks based on
- * any grace periods that elapsed while the CPU was idle, and if any
- * callbacks are now ready to invoke, initiate invocation.
- */
-static void rcu_cleanup_after_idle(void)
-{
- struct rcu_data *rdp = this_cpu_ptr(&rcu_data);
-
- lockdep_assert_irqs_disabled();
- if (rcu_segcblist_is_offloaded(&rdp->cblist))
- return;
- if (rcu_try_advance_all_cbs())
- invoke_rcu_core();
-}
-
-#endif /* #else #if !defined(CONFIG_RCU_FAST_NO_HZ) */
-
-#ifdef CONFIG_RCU_NOCB_CPU
-
-/*
- * Offload callback processing from the boot-time-specified set of CPUs
- * specified by rcu_nocb_mask. For the CPUs in the set, there are kthreads
- * created that pull the callbacks from the corresponding CPU, wait for
- * a grace period to elapse, and invoke the callbacks. These kthreads
- * are organized into GP kthreads, which manage incoming callbacks, wait for
- * grace periods, and awaken CB kthreads, and the CB kthreads, which only
- * invoke callbacks. Each GP kthread invokes its own CBs. The no-CBs CPUs
- * do a wake_up() on their GP kthread when they insert a callback into any
- * empty list, unless the rcu_nocb_poll boot parameter has been specified,
- * in which case each kthread actively polls its CPU. (Which isn't so great
- * for energy efficiency, but which does reduce RCU's overhead on that CPU.)
- *
- * This is intended to be used in conjunction with Frederic Weisbecker's
- * adaptive-idle work, which would seriously reduce OS jitter on CPUs
- * running CPU-bound user-mode computations.
- *
- * Offloading of callbacks can also be used as an energy-efficiency
- * measure because CPUs with no RCU callbacks queued are more aggressive
- * about entering dyntick-idle mode.
- */
-
-
-/*
- * Parse the boot-time rcu_nocb_mask CPU list from the kernel parameters.
- * The string after the "rcu_nocbs=" is either "all" for all CPUs, or a
- * comma-separated list of CPUs and/or CPU ranges. If an invalid list is
- * given, a warning is emitted and all CPUs are offloaded.
- */
-static int __init rcu_nocb_setup(char *str)
-{
- alloc_bootmem_cpumask_var(&rcu_nocb_mask);
- if (!strcasecmp(str, "all"))
- cpumask_setall(rcu_nocb_mask);
- else
- if (cpulist_parse(str, rcu_nocb_mask)) {
- pr_warn("rcu_nocbs= bad CPU range, all CPUs set\n");
- cpumask_setall(rcu_nocb_mask);
- }
- return 1;
-}
-__setup("rcu_nocbs=", rcu_nocb_setup);
-
-static int __init parse_rcu_nocb_poll(char *arg)
-{
- rcu_nocb_poll = true;
- return 0;
-}
-early_param("rcu_nocb_poll", parse_rcu_nocb_poll);
-
-/*
- * Don't bother bypassing ->cblist if the call_rcu() rate is low.
- * After all, the main point of bypassing is to avoid lock contention
- * on ->nocb_lock, which only can happen at high call_rcu() rates.
- */
-int nocb_nobypass_lim_per_jiffy = 16 * 1000 / HZ;
-module_param(nocb_nobypass_lim_per_jiffy, int, 0);
-
-/*
- * Acquire the specified rcu_data structure's ->nocb_bypass_lock. If the
- * lock isn't immediately available, increment ->nocb_lock_contended to
- * flag the contention.
- */
-static void rcu_nocb_bypass_lock(struct rcu_data *rdp)
-{
- lockdep_assert_irqs_disabled();
- if (raw_spin_trylock(&rdp->nocb_bypass_lock))
- return;
- atomic_inc(&rdp->nocb_lock_contended);
- WARN_ON_ONCE(smp_processor_id() != rdp->cpu);
- smp_mb__after_atomic(); /* atomic_inc() before lock. */
- raw_spin_lock(&rdp->nocb_bypass_lock);
- smp_mb__before_atomic(); /* atomic_dec() after lock. */
- atomic_dec(&rdp->nocb_lock_contended);
-}
-
-/*
- * Spinwait until the specified rcu_data structure's ->nocb_lock is
- * not contended. Please note that this is extremely special-purpose,
- * relying on the fact that at most two kthreads and one CPU contend for
- * this lock, and also that the two kthreads are guaranteed to have frequent
- * grace-period-duration time intervals between successive acquisitions
- * of the lock. This allows us to use an extremely simple throttling
- * mechanism, and further to apply it only to the CPU doing floods of
- * call_rcu() invocations. Don't try this at home!
- */
-static void rcu_nocb_wait_contended(struct rcu_data *rdp)
-{
- WARN_ON_ONCE(smp_processor_id() != rdp->cpu);
- while (WARN_ON_ONCE(atomic_read(&rdp->nocb_lock_contended)))
- cpu_relax();
-}
-
-/*
- * Conditionally acquire the specified rcu_data structure's
- * ->nocb_bypass_lock.
- */
-static bool rcu_nocb_bypass_trylock(struct rcu_data *rdp)
-{
- lockdep_assert_irqs_disabled();
- return raw_spin_trylock(&rdp->nocb_bypass_lock);
-}
-
-/*
- * Release the specified rcu_data structure's ->nocb_bypass_lock.
- */
-static void rcu_nocb_bypass_unlock(struct rcu_data *rdp)
-{
- lockdep_assert_irqs_disabled();
- raw_spin_unlock(&rdp->nocb_bypass_lock);
-}
-
-/*
- * Acquire the specified rcu_data structure's ->nocb_lock, but only
- * if it corresponds to a no-CBs CPU.
- */
-static void rcu_nocb_lock(struct rcu_data *rdp)
-{
- lockdep_assert_irqs_disabled();
- if (!rcu_segcblist_is_offloaded(&rdp->cblist))
- return;
- raw_spin_lock(&rdp->nocb_lock);
-}
-
-/*
- * Release the specified rcu_data structure's ->nocb_lock, but only
- * if it corresponds to a no-CBs CPU.
- */
-static void rcu_nocb_unlock(struct rcu_data *rdp)
-{
- if (rcu_segcblist_is_offloaded(&rdp->cblist)) {
- lockdep_assert_irqs_disabled();
- raw_spin_unlock(&rdp->nocb_lock);
- }
-}
-
-/*
- * Release the specified rcu_data structure's ->nocb_lock and restore
- * interrupts, but only if it corresponds to a no-CBs CPU.
- */
-static void rcu_nocb_unlock_irqrestore(struct rcu_data *rdp,
- unsigned long flags)
-{
- if (rcu_segcblist_is_offloaded(&rdp->cblist)) {
- lockdep_assert_irqs_disabled();
- raw_spin_unlock_irqrestore(&rdp->nocb_lock, flags);
- } else {
- local_irq_restore(flags);
- }
-}
-
-/* Lockdep check that ->cblist may be safely accessed. */
-static void rcu_lockdep_assert_cblist_protected(struct rcu_data *rdp)
-{
- lockdep_assert_irqs_disabled();
- if (rcu_segcblist_is_offloaded(&rdp->cblist) &&
- cpu_online(rdp->cpu))
- lockdep_assert_held(&rdp->nocb_lock);
-}
-
-/*
- * Wake up any no-CBs CPUs' kthreads that were waiting on the just-ended
- * grace period.
- */
-static void rcu_nocb_gp_cleanup(struct swait_queue_head *sq)
-{
- swake_up_all(sq);
-}
-
-static struct swait_queue_head *rcu_nocb_gp_get(struct rcu_node *rnp)
-{
- return &rnp->nocb_gp_wq[rcu_seq_ctr(rnp->gp_seq) & 0x1];
-}
-
-static void rcu_init_one_nocb(struct rcu_node *rnp)
-{
- init_swait_queue_head(&rnp->nocb_gp_wq[0]);
- init_swait_queue_head(&rnp->nocb_gp_wq[1]);
-}
-
-/* Is the specified CPU a no-CBs CPU? */
-bool rcu_is_nocb_cpu(int cpu)
-{
- if (cpumask_available(rcu_nocb_mask))
- return cpumask_test_cpu(cpu, rcu_nocb_mask);
- return false;
-}
-
-/*
- * Kick the GP kthread for this NOCB group. Caller holds ->nocb_lock
- * and this function releases it.
- */
-static void wake_nocb_gp(struct rcu_data *rdp, bool force,
- unsigned long flags)
- __releases(rdp->nocb_lock)
-{
- bool needwake = false;
- struct rcu_data *rdp_gp = rdp->nocb_gp_rdp;
-
- lockdep_assert_held(&rdp->nocb_lock);
- if (!READ_ONCE(rdp_gp->nocb_gp_kthread)) {
- trace_rcu_nocb_wake(rcu_state.name, rdp->cpu,
- TPS("AlreadyAwake"));
- rcu_nocb_unlock_irqrestore(rdp, flags);
- return;
- }
- del_timer(&rdp->nocb_timer);
- rcu_nocb_unlock_irqrestore(rdp, flags);
- raw_spin_lock_irqsave(&rdp_gp->nocb_gp_lock, flags);
- if (force || READ_ONCE(rdp_gp->nocb_gp_sleep)) {
- WRITE_ONCE(rdp_gp->nocb_gp_sleep, false);
- needwake = true;
- trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("DoWake"));
- }
- raw_spin_unlock_irqrestore(&rdp_gp->nocb_gp_lock, flags);
- if (needwake)
- wake_up_process(rdp_gp->nocb_gp_kthread);
-}
-
-/*
- * Arrange to wake the GP kthread for this NOCB group at some future
- * time when it is safe to do so.
- */
-static void wake_nocb_gp_defer(struct rcu_data *rdp, int waketype,
- const char *reason)
-{
- if (rdp->nocb_defer_wakeup == RCU_NOCB_WAKE_NOT)
- mod_timer(&rdp->nocb_timer, jiffies + 1);
- if (rdp->nocb_defer_wakeup < waketype)
- WRITE_ONCE(rdp->nocb_defer_wakeup, waketype);
- trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, reason);
-}
-
-/*
- * Flush the ->nocb_bypass queue into ->cblist, enqueuing rhp if non-NULL.
- * However, if there is a callback to be enqueued and if ->nocb_bypass
- * proves to be initially empty, just return false because the no-CB GP
- * kthread may need to be awakened in this case.
- *
- * Note that this function always returns true if rhp is NULL.
- */
-static bool rcu_nocb_do_flush_bypass(struct rcu_data *rdp, struct rcu_head *rhp,
- unsigned long j)
-{
- struct rcu_cblist rcl;
-
- WARN_ON_ONCE(!rcu_segcblist_is_offloaded(&rdp->cblist));
- rcu_lockdep_assert_cblist_protected(rdp);
- lockdep_assert_held(&rdp->nocb_bypass_lock);
- if (rhp && !rcu_cblist_n_cbs(&rdp->nocb_bypass)) {
- raw_spin_unlock(&rdp->nocb_bypass_lock);
- return false;
- }
- /* Note: ->cblist.len already accounts for ->nocb_bypass contents. */
- if (rhp)
- rcu_segcblist_inc_len(&rdp->cblist); /* Must precede enqueue. */
- rcu_cblist_flush_enqueue(&rcl, &rdp->nocb_bypass, rhp);
- rcu_segcblist_insert_pend_cbs(&rdp->cblist, &rcl);
- WRITE_ONCE(rdp->nocb_bypass_first, j);
- rcu_nocb_bypass_unlock(rdp);
- return true;
-}
-
-/*
- * Flush the ->nocb_bypass queue into ->cblist, enqueuing rhp if non-NULL.
- * However, if there is a callback to be enqueued and if ->nocb_bypass
- * proves to be initially empty, just return false because the no-CB GP
- * kthread may need to be awakened in this case.
- *
- * Note that this function always returns true if rhp is NULL.
- */
-static bool rcu_nocb_flush_bypass(struct rcu_data *rdp, struct rcu_head *rhp,
- unsigned long j)
-{
- if (!rcu_segcblist_is_offloaded(&rdp->cblist))
- return true;
- rcu_lockdep_assert_cblist_protected(rdp);
- rcu_nocb_bypass_lock(rdp);
- return rcu_nocb_do_flush_bypass(rdp, rhp, j);
-}
-
-/*
- * If the ->nocb_bypass_lock is immediately available, flush the
- * ->nocb_bypass queue into ->cblist.
- */
-static void rcu_nocb_try_flush_bypass(struct rcu_data *rdp, unsigned long j)
-{
- rcu_lockdep_assert_cblist_protected(rdp);
- if (!rcu_segcblist_is_offloaded(&rdp->cblist) ||
- !rcu_nocb_bypass_trylock(rdp))
- return;
- WARN_ON_ONCE(!rcu_nocb_do_flush_bypass(rdp, NULL, j));
-}
-
-/*
- * See whether it is appropriate to use the ->nocb_bypass list in order
- * to control contention on ->nocb_lock. A limited number of direct
- * enqueues are permitted into ->cblist per jiffy. If ->nocb_bypass
- * is non-empty, further callbacks must be placed into ->nocb_bypass,
- * otherwise rcu_barrier() breaks. Use rcu_nocb_flush_bypass() to switch
- * back to direct use of ->cblist. However, ->nocb_bypass should not be
- * used if ->cblist is empty, because otherwise callbacks can be stranded
- * on ->nocb_bypass because we cannot count on the current CPU ever again
- * invoking call_rcu(). The general rule is that if ->nocb_bypass is
- * non-empty, the corresponding no-CBs grace-period kthread must not be
- * in an indefinite sleep state.
- *
- * Finally, it is not permitted to use the bypass during early boot,
- * as doing so would confuse the auto-initialization code. Besides
- * which, there is no point in worrying about lock contention while
- * there is only one CPU in operation.
- */
-static bool rcu_nocb_try_bypass(struct rcu_data *rdp, struct rcu_head *rhp,
- bool *was_alldone, unsigned long flags)
-{
- unsigned long c;
- unsigned long cur_gp_seq;
- unsigned long j = jiffies;
- long ncbs = rcu_cblist_n_cbs(&rdp->nocb_bypass);
-
- if (!rcu_segcblist_is_offloaded(&rdp->cblist)) {
- *was_alldone = !rcu_segcblist_pend_cbs(&rdp->cblist);
- return false; /* Not offloaded, no bypassing. */
- }
- lockdep_assert_irqs_disabled();
-
- // Don't use ->nocb_bypass during early boot.
- if (rcu_scheduler_active != RCU_SCHEDULER_RUNNING) {
- rcu_nocb_lock(rdp);
- WARN_ON_ONCE(rcu_cblist_n_cbs(&rdp->nocb_bypass));
- *was_alldone = !rcu_segcblist_pend_cbs(&rdp->cblist);
- return false;
- }
-
- // If we have advanced to a new jiffy, reset counts to allow
- // moving back from ->nocb_bypass to ->cblist.
- if (j == rdp->nocb_nobypass_last) {
- c = rdp->nocb_nobypass_count + 1;
- } else {
- WRITE_ONCE(rdp->nocb_nobypass_last, j);
- c = rdp->nocb_nobypass_count - nocb_nobypass_lim_per_jiffy;
- if (ULONG_CMP_LT(rdp->nocb_nobypass_count,
- nocb_nobypass_lim_per_jiffy))
- c = 0;
- else if (c > nocb_nobypass_lim_per_jiffy)
- c = nocb_nobypass_lim_per_jiffy;
- }
- WRITE_ONCE(rdp->nocb_nobypass_count, c);
-
- // If there hasn't yet been all that many ->cblist enqueues
- // this jiffy, tell the caller to enqueue onto ->cblist. But flush
- // ->nocb_bypass first.
- if (rdp->nocb_nobypass_count < nocb_nobypass_lim_per_jiffy) {
- rcu_nocb_lock(rdp);
- *was_alldone = !rcu_segcblist_pend_cbs(&rdp->cblist);
- if (*was_alldone)
- trace_rcu_nocb_wake(rcu_state.name, rdp->cpu,
- TPS("FirstQ"));
- WARN_ON_ONCE(!rcu_nocb_flush_bypass(rdp, NULL, j));
- WARN_ON_ONCE(rcu_cblist_n_cbs(&rdp->nocb_bypass));
- return false; // Caller must enqueue the callback.
- }
-
- // If ->nocb_bypass has been used too long or is too full,
- // flush ->nocb_bypass to ->cblist.
- if ((ncbs && j != READ_ONCE(rdp->nocb_bypass_first)) ||
- ncbs >= qhimark) {
- rcu_nocb_lock(rdp);
- if (!rcu_nocb_flush_bypass(rdp, rhp, j)) {
- *was_alldone = !rcu_segcblist_pend_cbs(&rdp->cblist);
- if (*was_alldone)
- trace_rcu_nocb_wake(rcu_state.name, rdp->cpu,
- TPS("FirstQ"));
- WARN_ON_ONCE(rcu_cblist_n_cbs(&rdp->nocb_bypass));
- return false; // Caller must enqueue the callback.
- }
- if (j != rdp->nocb_gp_adv_time &&
- rcu_segcblist_nextgp(&rdp->cblist, &cur_gp_seq) &&
- rcu_seq_done(&rdp->mynode->gp_seq, cur_gp_seq)) {
- rcu_advance_cbs_nowake(rdp->mynode, rdp);
- rdp->nocb_gp_adv_time = j;
- }
- rcu_nocb_unlock_irqrestore(rdp, flags);
- return true; // Callback already enqueued.
- }
-
- // We need to use the bypass.
- rcu_nocb_wait_contended(rdp);
- rcu_nocb_bypass_lock(rdp);
- ncbs = rcu_cblist_n_cbs(&rdp->nocb_bypass);
- rcu_segcblist_inc_len(&rdp->cblist); /* Must precede enqueue. */
- rcu_cblist_enqueue(&rdp->nocb_bypass, rhp);
- if (!ncbs) {
- WRITE_ONCE(rdp->nocb_bypass_first, j);
- trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("FirstBQ"));
- }
- rcu_nocb_bypass_unlock(rdp);
- smp_mb(); /* Order enqueue before wake. */
- if (ncbs) {
- local_irq_restore(flags);
- } else {
- // No-CBs GP kthread might be indefinitely asleep, if so, wake.
- rcu_nocb_lock(rdp); // Rare during call_rcu() flood.
- if (!rcu_segcblist_pend_cbs(&rdp->cblist)) {
- trace_rcu_nocb_wake(rcu_state.name, rdp->cpu,
- TPS("FirstBQwake"));
- __call_rcu_nocb_wake(rdp, true, flags);
- } else {
- trace_rcu_nocb_wake(rcu_state.name, rdp->cpu,
- TPS("FirstBQnoWake"));
- rcu_nocb_unlock_irqrestore(rdp, flags);
- }
- }
- return true; // Callback already enqueued.
-}
-
-/*
- * Awaken the no-CBs grace-period kthead if needed, either due to it
- * legitimately being asleep or due to overload conditions.
- *
- * If warranted, also wake up the kthread servicing this CPUs queues.
- */
-static void __call_rcu_nocb_wake(struct rcu_data *rdp, bool was_alldone,
- unsigned long flags)
- __releases(rdp->nocb_lock)
-{
- unsigned long cur_gp_seq;
- unsigned long j;
- long len;
- struct task_struct *t;
-
- // If we are being polled or there is no kthread, just leave.
- t = READ_ONCE(rdp->nocb_gp_kthread);
- if (rcu_nocb_poll || !t) {
- trace_rcu_nocb_wake(rcu_state.name, rdp->cpu,
- TPS("WakeNotPoll"));
- rcu_nocb_unlock_irqrestore(rdp, flags);
- return;
- }
- // Need to actually to a wakeup.
- len = rcu_segcblist_n_cbs(&rdp->cblist);
- if (was_alldone) {
- rdp->qlen_last_fqs_check = len;
- if (!irqs_disabled_flags(flags)) {
- /* ... if queue was empty ... */
- wake_nocb_gp(rdp, false, flags);
- trace_rcu_nocb_wake(rcu_state.name, rdp->cpu,
- TPS("WakeEmpty"));
- } else {
- wake_nocb_gp_defer(rdp, RCU_NOCB_WAKE,
- TPS("WakeEmptyIsDeferred"));
- rcu_nocb_unlock_irqrestore(rdp, flags);
- }
- } else if (len > rdp->qlen_last_fqs_check + qhimark) {
- /* ... or if many callbacks queued. */
- rdp->qlen_last_fqs_check = len;
- j = jiffies;
- if (j != rdp->nocb_gp_adv_time &&
- rcu_segcblist_nextgp(&rdp->cblist, &cur_gp_seq) &&
- rcu_seq_done(&rdp->mynode->gp_seq, cur_gp_seq)) {
- rcu_advance_cbs_nowake(rdp->mynode, rdp);
- rdp->nocb_gp_adv_time = j;
- }
- smp_mb(); /* Enqueue before timer_pending(). */
- if ((rdp->nocb_cb_sleep ||
- !rcu_segcblist_ready_cbs(&rdp->cblist)) &&
- !timer_pending(&rdp->nocb_bypass_timer))
- wake_nocb_gp_defer(rdp, RCU_NOCB_WAKE_FORCE,
- TPS("WakeOvfIsDeferred"));
- rcu_nocb_unlock_irqrestore(rdp, flags);
- } else {
- trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("WakeNot"));
- rcu_nocb_unlock_irqrestore(rdp, flags);
- }
- return;
-}
-
-/* Wake up the no-CBs GP kthread to flush ->nocb_bypass. */
-static void do_nocb_bypass_wakeup_timer(struct timer_list *t)
-{
- unsigned long flags;
- struct rcu_data *rdp = from_timer(rdp, t, nocb_bypass_timer);
-
- trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("Timer"));
- rcu_nocb_lock_irqsave(rdp, flags);
- smp_mb__after_spinlock(); /* Timer expire before wakeup. */
- __call_rcu_nocb_wake(rdp, true, flags);
-}
-
-/*
- * No-CBs GP kthreads come here to wait for additional callbacks to show up
- * or for grace periods to end.
- */
-static void nocb_gp_wait(struct rcu_data *my_rdp)
-{
- bool bypass = false;
- long bypass_ncbs;
- int __maybe_unused cpu = my_rdp->cpu;
- unsigned long cur_gp_seq;
- unsigned long flags;
- bool gotcbs = false;
- unsigned long j = jiffies;
- bool needwait_gp = false; // This prevents actual uninitialized use.
- bool needwake;
- bool needwake_gp;
- struct rcu_data *rdp;
- struct rcu_node *rnp;
- unsigned long wait_gp_seq = 0; // Suppress "use uninitialized" warning.
-
- /*
- * Each pass through the following loop checks for CBs and for the
- * nearest grace period (if any) to wait for next. The CB kthreads
- * and the global grace-period kthread are awakened if needed.
- */
- for (rdp = my_rdp; rdp; rdp = rdp->nocb_next_cb_rdp) {
- trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("Check"));
- rcu_nocb_lock_irqsave(rdp, flags);
- bypass_ncbs = rcu_cblist_n_cbs(&rdp->nocb_bypass);
- if (bypass_ncbs &&
- (time_after(j, READ_ONCE(rdp->nocb_bypass_first) + 1) ||
- bypass_ncbs > 2 * qhimark)) {
- // Bypass full or old, so flush it.
- (void)rcu_nocb_try_flush_bypass(rdp, j);
- bypass_ncbs = rcu_cblist_n_cbs(&rdp->nocb_bypass);
- } else if (!bypass_ncbs && rcu_segcblist_empty(&rdp->cblist)) {
- rcu_nocb_unlock_irqrestore(rdp, flags);
- continue; /* No callbacks here, try next. */
- }
- if (bypass_ncbs) {
- trace_rcu_nocb_wake(rcu_state.name, rdp->cpu,
- TPS("Bypass"));
- bypass = true;
- }
- rnp = rdp->mynode;
- if (bypass) { // Avoid race with first bypass CB.
- WRITE_ONCE(my_rdp->nocb_defer_wakeup,
- RCU_NOCB_WAKE_NOT);
- del_timer(&my_rdp->nocb_timer);
- }
- // Advance callbacks if helpful and low contention.
- needwake_gp = false;
- if (!rcu_segcblist_restempty(&rdp->cblist,
- RCU_NEXT_READY_TAIL) ||
- (rcu_segcblist_nextgp(&rdp->cblist, &cur_gp_seq) &&
- rcu_seq_done(&rnp->gp_seq, cur_gp_seq))) {
- raw_spin_lock_rcu_node(rnp); /* irqs disabled. */
- needwake_gp = rcu_advance_cbs(rnp, rdp);
- raw_spin_unlock_rcu_node(rnp); /* irqs disabled. */
- }
- // Need to wait on some grace period?
- WARN_ON_ONCE(!rcu_segcblist_restempty(&rdp->cblist,
- RCU_NEXT_READY_TAIL));
- if (rcu_segcblist_nextgp(&rdp->cblist, &cur_gp_seq)) {
- if (!needwait_gp ||
- ULONG_CMP_LT(cur_gp_seq, wait_gp_seq))
- wait_gp_seq = cur_gp_seq;
- needwait_gp = true;
- trace_rcu_nocb_wake(rcu_state.name, rdp->cpu,
- TPS("NeedWaitGP"));
- }
- if (rcu_segcblist_ready_cbs(&rdp->cblist)) {
- needwake = rdp->nocb_cb_sleep;
- WRITE_ONCE(rdp->nocb_cb_sleep, false);
- smp_mb(); /* CB invocation -after- GP end. */
- } else {
- needwake = false;
- }
- rcu_nocb_unlock_irqrestore(rdp, flags);
- if (needwake) {
- swake_up_one(&rdp->nocb_cb_wq);
- gotcbs = true;
- }
- if (needwake_gp)
- rcu_gp_kthread_wake();
- }
-
- my_rdp->nocb_gp_bypass = bypass;
- my_rdp->nocb_gp_gp = needwait_gp;
- my_rdp->nocb_gp_seq = needwait_gp ? wait_gp_seq : 0;
- if (bypass && !rcu_nocb_poll) {
- // At least one child with non-empty ->nocb_bypass, so set
- // timer in order to avoid stranding its callbacks.
- raw_spin_lock_irqsave(&my_rdp->nocb_gp_lock, flags);
- mod_timer(&my_rdp->nocb_bypass_timer, j + 2);
- raw_spin_unlock_irqrestore(&my_rdp->nocb_gp_lock, flags);
- }
- if (rcu_nocb_poll) {
- /* Polling, so trace if first poll in the series. */
- if (gotcbs)
- trace_rcu_nocb_wake(rcu_state.name, cpu, TPS("Poll"));
- schedule_timeout_interruptible(1);
- } else if (!needwait_gp) {
- /* Wait for callbacks to appear. */
- trace_rcu_nocb_wake(rcu_state.name, cpu, TPS("Sleep"));
- swait_event_interruptible_exclusive(my_rdp->nocb_gp_wq,
- !READ_ONCE(my_rdp->nocb_gp_sleep));
- trace_rcu_nocb_wake(rcu_state.name, cpu, TPS("EndSleep"));
- } else {
- rnp = my_rdp->mynode;
- trace_rcu_this_gp(rnp, my_rdp, wait_gp_seq, TPS("StartWait"));
- swait_event_interruptible_exclusive(
- rnp->nocb_gp_wq[rcu_seq_ctr(wait_gp_seq) & 0x1],
- rcu_seq_done(&rnp->gp_seq, wait_gp_seq) ||
- !READ_ONCE(my_rdp->nocb_gp_sleep));
- trace_rcu_this_gp(rnp, my_rdp, wait_gp_seq, TPS("EndWait"));
- }
- if (!rcu_nocb_poll) {
- raw_spin_lock_irqsave(&my_rdp->nocb_gp_lock, flags);
- if (bypass)
- del_timer(&my_rdp->nocb_bypass_timer);
- WRITE_ONCE(my_rdp->nocb_gp_sleep, true);
- raw_spin_unlock_irqrestore(&my_rdp->nocb_gp_lock, flags);
- }
- my_rdp->nocb_gp_seq = -1;
- WARN_ON(signal_pending(current));
-}
-
-/*
- * No-CBs grace-period-wait kthread. There is one of these per group
- * of CPUs, but only once at least one CPU in that group has come online
- * at least once since boot. This kthread checks for newly posted
- * callbacks from any of the CPUs it is responsible for, waits for a
- * grace period, then awakens all of the rcu_nocb_cb_kthread() instances
- * that then have callback-invocation work to do.
- */
-static int rcu_nocb_gp_kthread(void *arg)
-{
- struct rcu_data *rdp = arg;
-
- for (;;) {
- WRITE_ONCE(rdp->nocb_gp_loops, rdp->nocb_gp_loops + 1);
- nocb_gp_wait(rdp);
- cond_resched_tasks_rcu_qs();
- }
- return 0;
-}
-
-/*
- * Invoke any ready callbacks from the corresponding no-CBs CPU,
- * then, if there are no more, wait for more to appear.
- */
-static void nocb_cb_wait(struct rcu_data *rdp)
-{
- unsigned long cur_gp_seq;
- unsigned long flags;
- bool needwake_gp = false;
- struct rcu_node *rnp = rdp->mynode;
-
- local_irq_save(flags);
- rcu_momentary_dyntick_idle();
- local_irq_restore(flags);
- local_bh_disable();
- rcu_do_batch(rdp);
- local_bh_enable();
- lockdep_assert_irqs_enabled();
- rcu_nocb_lock_irqsave(rdp, flags);
- if (rcu_segcblist_nextgp(&rdp->cblist, &cur_gp_seq) &&
- rcu_seq_done(&rnp->gp_seq, cur_gp_seq) &&
- raw_spin_trylock_rcu_node(rnp)) { /* irqs already disabled. */
- needwake_gp = rcu_advance_cbs(rdp->mynode, rdp);
- raw_spin_unlock_rcu_node(rnp); /* irqs remain disabled. */
- }
- if (rcu_segcblist_ready_cbs(&rdp->cblist)) {
- rcu_nocb_unlock_irqrestore(rdp, flags);
- if (needwake_gp)
- rcu_gp_kthread_wake();
- return;
- }
-
- trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("CBSleep"));
- WRITE_ONCE(rdp->nocb_cb_sleep, true);
- rcu_nocb_unlock_irqrestore(rdp, flags);
- if (needwake_gp)
- rcu_gp_kthread_wake();
- swait_event_interruptible_exclusive(rdp->nocb_cb_wq,
- !READ_ONCE(rdp->nocb_cb_sleep));
- if (!smp_load_acquire(&rdp->nocb_cb_sleep)) { /* VVV */
- /* ^^^ Ensure CB invocation follows _sleep test. */
- return;
- }
- WARN_ON(signal_pending(current));
- trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("WokeEmpty"));
-}
-
-/*
- * Per-rcu_data kthread, but only for no-CBs CPUs. Repeatedly invoke
- * nocb_cb_wait() to do the dirty work.
- */
-static int rcu_nocb_cb_kthread(void *arg)
-{
- struct rcu_data *rdp = arg;
-
- // Each pass through this loop does one callback batch, and,
- // if there are no more ready callbacks, waits for them.
- for (;;) {
- nocb_cb_wait(rdp);
- cond_resched_tasks_rcu_qs();
- }
- return 0;
-}
-
-/* Is a deferred wakeup of rcu_nocb_kthread() required? */
-static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp)
-{
- return READ_ONCE(rdp->nocb_defer_wakeup);
-}
-
-/* Do a deferred wakeup of rcu_nocb_kthread(). */
-static void do_nocb_deferred_wakeup_common(struct rcu_data *rdp)
-{
- unsigned long flags;
- int ndw;
-
- rcu_nocb_lock_irqsave(rdp, flags);
- if (!rcu_nocb_need_deferred_wakeup(rdp)) {
- rcu_nocb_unlock_irqrestore(rdp, flags);
- return;
- }
- ndw = READ_ONCE(rdp->nocb_defer_wakeup);
- WRITE_ONCE(rdp->nocb_defer_wakeup, RCU_NOCB_WAKE_NOT);
- wake_nocb_gp(rdp, ndw == RCU_NOCB_WAKE_FORCE, flags);
- trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("DeferredWake"));
-}
-
-/* Do a deferred wakeup of rcu_nocb_kthread() from a timer handler. */
-static void do_nocb_deferred_wakeup_timer(struct timer_list *t)
-{
- struct rcu_data *rdp = from_timer(rdp, t, nocb_timer);
-
- do_nocb_deferred_wakeup_common(rdp);
-}
-
-/*
- * Do a deferred wakeup of rcu_nocb_kthread() from fastpath.
- * This means we do an inexact common-case check. Note that if
- * we miss, ->nocb_timer will eventually clean things up.
- */
-static void do_nocb_deferred_wakeup(struct rcu_data *rdp)
-{
- if (rcu_nocb_need_deferred_wakeup(rdp))
- do_nocb_deferred_wakeup_common(rdp);
-}
-
-void __init rcu_init_nohz(void)
-{
- int cpu;
- bool need_rcu_nocb_mask = false;
- struct rcu_data *rdp;
-
-#if defined(CONFIG_NO_HZ_FULL)
- if (tick_nohz_full_running && cpumask_weight(tick_nohz_full_mask))
- need_rcu_nocb_mask = true;
-#endif /* #if defined(CONFIG_NO_HZ_FULL) */
-
- if (!cpumask_available(rcu_nocb_mask) && need_rcu_nocb_mask) {
- if (!zalloc_cpumask_var(&rcu_nocb_mask, GFP_KERNEL)) {
- pr_info("rcu_nocb_mask allocation failed, callback offloading disabled.\n");
- return;
- }
- }
- if (!cpumask_available(rcu_nocb_mask))
- return;
-
-#if defined(CONFIG_NO_HZ_FULL)
- if (tick_nohz_full_running)
- cpumask_or(rcu_nocb_mask, rcu_nocb_mask, tick_nohz_full_mask);
-#endif /* #if defined(CONFIG_NO_HZ_FULL) */
-
- if (!cpumask_subset(rcu_nocb_mask, cpu_possible_mask)) {
- pr_info("\tNote: kernel parameter 'rcu_nocbs=', 'nohz_full', or 'isolcpus=' contains nonexistent CPUs.\n");
- cpumask_and(rcu_nocb_mask, cpu_possible_mask,
- rcu_nocb_mask);
- }
- if (cpumask_empty(rcu_nocb_mask))
- pr_info("\tOffload RCU callbacks from CPUs: (none).\n");
- else
- pr_info("\tOffload RCU callbacks from CPUs: %*pbl.\n",
- cpumask_pr_args(rcu_nocb_mask));
- if (rcu_nocb_poll)
- pr_info("\tPoll for callbacks from no-CBs CPUs.\n");
-
- for_each_cpu(cpu, rcu_nocb_mask) {
- rdp = per_cpu_ptr(&rcu_data, cpu);
- if (rcu_segcblist_empty(&rdp->cblist))
- rcu_segcblist_init(&rdp->cblist);
- rcu_segcblist_offload(&rdp->cblist);
- }
- rcu_organize_nocb_kthreads();
-}
-
-/* Initialize per-rcu_data variables for no-CBs CPUs. */
-static void __init rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp)
-{
- init_swait_queue_head(&rdp->nocb_cb_wq);
- init_swait_queue_head(&rdp->nocb_gp_wq);
- raw_spin_lock_init(&rdp->nocb_lock);
- raw_spin_lock_init(&rdp->nocb_bypass_lock);
- raw_spin_lock_init(&rdp->nocb_gp_lock);
- timer_setup(&rdp->nocb_timer, do_nocb_deferred_wakeup_timer, 0);
- timer_setup(&rdp->nocb_bypass_timer, do_nocb_bypass_wakeup_timer, 0);
- rcu_cblist_init(&rdp->nocb_bypass);
-}
-
-/*
- * If the specified CPU is a no-CBs CPU that does not already have its
- * rcuo CB kthread, spawn it. Additionally, if the rcuo GP kthread
- * for this CPU's group has not yet been created, spawn it as well.
- */
-static void rcu_spawn_one_nocb_kthread(int cpu)
-{
- struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
- struct rcu_data *rdp_gp;
- struct task_struct *t;
-
- /*
- * If this isn't a no-CBs CPU or if it already has an rcuo kthread,
- * then nothing to do.
- */
- if (!rcu_is_nocb_cpu(cpu) || rdp->nocb_cb_kthread)
- return;
-
- /* If we didn't spawn the GP kthread first, reorganize! */
- rdp_gp = rdp->nocb_gp_rdp;
- if (!rdp_gp->nocb_gp_kthread) {
- t = kthread_run(rcu_nocb_gp_kthread, rdp_gp,
- "rcuog/%d", rdp_gp->cpu);
- if (WARN_ONCE(IS_ERR(t), "%s: Could not start rcuo GP kthread, OOM is now expected behavior\n", __func__))
- return;
- WRITE_ONCE(rdp_gp->nocb_gp_kthread, t);
- }
-
- /* Spawn the kthread for this CPU. */
- t = kthread_run(rcu_nocb_cb_kthread, rdp,
- "rcuo%c/%d", rcu_state.abbr, cpu);
- if (WARN_ONCE(IS_ERR(t), "%s: Could not start rcuo CB kthread, OOM is now expected behavior\n", __func__))
- return;
- WRITE_ONCE(rdp->nocb_cb_kthread, t);
- WRITE_ONCE(rdp->nocb_gp_kthread, rdp_gp->nocb_gp_kthread);
-}
-
-/*
- * If the specified CPU is a no-CBs CPU that does not already have its
- * rcuo kthread, spawn it.
- */
-static void rcu_spawn_cpu_nocb_kthread(int cpu)
-{
- if (rcu_scheduler_fully_active)
- rcu_spawn_one_nocb_kthread(cpu);
-}
-
-/*
- * Once the scheduler is running, spawn rcuo kthreads for all online
- * no-CBs CPUs. This assumes that the early_initcall()s happen before
- * non-boot CPUs come online -- if this changes, we will need to add
- * some mutual exclusion.
- */
-static void __init rcu_spawn_nocb_kthreads(void)
-{
- int cpu;
-
- for_each_online_cpu(cpu)
- rcu_spawn_cpu_nocb_kthread(cpu);
-}
-
-/* How many CB CPU IDs per GP kthread? Default of -1 for sqrt(nr_cpu_ids). */
-static int rcu_nocb_gp_stride = -1;
-module_param(rcu_nocb_gp_stride, int, 0444);
-
-/*
- * Initialize GP-CB relationships for all no-CBs CPU.
- */
-static void __init rcu_organize_nocb_kthreads(void)
-{
- int cpu;
- bool firsttime = true;
- bool gotnocbs = false;
- bool gotnocbscbs = true;
- int ls = rcu_nocb_gp_stride;
- int nl = 0; /* Next GP kthread. */
- struct rcu_data *rdp;
- struct rcu_data *rdp_gp = NULL; /* Suppress misguided gcc warn. */
- struct rcu_data *rdp_prev = NULL;
-
- if (!cpumask_available(rcu_nocb_mask))
- return;
- if (ls == -1) {
- ls = nr_cpu_ids / int_sqrt(nr_cpu_ids);
- rcu_nocb_gp_stride = ls;
- }
-
- /*
- * Each pass through this loop sets up one rcu_data structure.
- * Should the corresponding CPU come online in the future, then
- * we will spawn the needed set of rcu_nocb_kthread() kthreads.
- */
- for_each_cpu(cpu, rcu_nocb_mask) {
- rdp = per_cpu_ptr(&rcu_data, cpu);
- if (rdp->cpu >= nl) {
- /* New GP kthread, set up for CBs & next GP. */
- gotnocbs = true;
- nl = DIV_ROUND_UP(rdp->cpu + 1, ls) * ls;
- rdp->nocb_gp_rdp = rdp;
- rdp_gp = rdp;
- if (dump_tree) {
- if (!firsttime)
- pr_cont("%s\n", gotnocbscbs
- ? "" : " (self only)");
- gotnocbscbs = false;
- firsttime = false;
- pr_alert("%s: No-CB GP kthread CPU %d:",
- __func__, cpu);
- }
- } else {
- /* Another CB kthread, link to previous GP kthread. */
- gotnocbscbs = true;
- rdp->nocb_gp_rdp = rdp_gp;
- rdp_prev->nocb_next_cb_rdp = rdp;
- if (dump_tree)
- pr_cont(" %d", cpu);
- }
- rdp_prev = rdp;
- }
- if (gotnocbs && dump_tree)
- pr_cont("%s\n", gotnocbscbs ? "" : " (self only)");
-}
-
-/*
- * Bind the current task to the offloaded CPUs. If there are no offloaded
- * CPUs, leave the task unbound. Splat if the bind attempt fails.
- */
-void rcu_bind_current_to_nocb(void)
-{
- if (cpumask_available(rcu_nocb_mask) && cpumask_weight(rcu_nocb_mask))
- WARN_ON(sched_setaffinity(current->pid, rcu_nocb_mask));
-}
-EXPORT_SYMBOL_GPL(rcu_bind_current_to_nocb);
-
-/*
- * Dump out nocb grace-period kthread state for the specified rcu_data
- * structure.
- */
-static void show_rcu_nocb_gp_state(struct rcu_data *rdp)
-{
- struct rcu_node *rnp = rdp->mynode;
-
- pr_info("nocb GP %d %c%c%c%c%c%c %c[%c%c] %c%c:%ld rnp %d:%d %lu\n",
- rdp->cpu,
- "kK"[!!rdp->nocb_gp_kthread],
- "lL"[raw_spin_is_locked(&rdp->nocb_gp_lock)],
- "dD"[!!rdp->nocb_defer_wakeup],
- "tT"[timer_pending(&rdp->nocb_timer)],
- "bB"[timer_pending(&rdp->nocb_bypass_timer)],
- "sS"[!!rdp->nocb_gp_sleep],
- ".W"[swait_active(&rdp->nocb_gp_wq)],
- ".W"[swait_active(&rnp->nocb_gp_wq[0])],
- ".W"[swait_active(&rnp->nocb_gp_wq[1])],
- ".B"[!!rdp->nocb_gp_bypass],
- ".G"[!!rdp->nocb_gp_gp],
- (long)rdp->nocb_gp_seq,
- rnp->grplo, rnp->grphi, READ_ONCE(rdp->nocb_gp_loops));
-}
-
-/* Dump out nocb kthread state for the specified rcu_data structure. */
-static void show_rcu_nocb_state(struct rcu_data *rdp)
-{
- struct rcu_segcblist *rsclp = &rdp->cblist;
- bool waslocked;
- bool wastimer;
- bool wassleep;
-
- if (rdp->nocb_gp_rdp == rdp)
- show_rcu_nocb_gp_state(rdp);
-
- pr_info(" CB %d->%d %c%c%c%c%c%c F%ld L%ld C%d %c%c%c%c%c q%ld\n",
- rdp->cpu, rdp->nocb_gp_rdp->cpu,
- "kK"[!!rdp->nocb_cb_kthread],
- "bB"[raw_spin_is_locked(&rdp->nocb_bypass_lock)],
- "cC"[!!atomic_read(&rdp->nocb_lock_contended)],
- "lL"[raw_spin_is_locked(&rdp->nocb_lock)],
- "sS"[!!rdp->nocb_cb_sleep],
- ".W"[swait_active(&rdp->nocb_cb_wq)],
- jiffies - rdp->nocb_bypass_first,
- jiffies - rdp->nocb_nobypass_last,
- rdp->nocb_nobypass_count,
- ".D"[rcu_segcblist_ready_cbs(rsclp)],
- ".W"[!rcu_segcblist_restempty(rsclp, RCU_DONE_TAIL)],
- ".R"[!rcu_segcblist_restempty(rsclp, RCU_WAIT_TAIL)],
- ".N"[!rcu_segcblist_restempty(rsclp, RCU_NEXT_READY_TAIL)],
- ".B"[!!rcu_cblist_n_cbs(&rdp->nocb_bypass)],
- rcu_segcblist_n_cbs(&rdp->cblist));
-
- /* It is OK for GP kthreads to have GP state. */
- if (rdp->nocb_gp_rdp == rdp)
- return;
-
- waslocked = raw_spin_is_locked(&rdp->nocb_gp_lock);
- wastimer = timer_pending(&rdp->nocb_timer);
- wassleep = swait_active(&rdp->nocb_gp_wq);
- if (!rdp->nocb_defer_wakeup && !rdp->nocb_gp_sleep &&
- !waslocked && !wastimer && !wassleep)
- return; /* Nothing untowards. */
-
- pr_info(" !!! %c%c%c%c %c\n",
- "lL"[waslocked],
- "dD"[!!rdp->nocb_defer_wakeup],
- "tT"[wastimer],
- "sS"[!!rdp->nocb_gp_sleep],
- ".W"[wassleep]);
-}
-
-#else /* #ifdef CONFIG_RCU_NOCB_CPU */
-
-/* No ->nocb_lock to acquire. */
-static void rcu_nocb_lock(struct rcu_data *rdp)
-{
-}
-
-/* No ->nocb_lock to release. */
-static void rcu_nocb_unlock(struct rcu_data *rdp)
-{
-}
-
-/* No ->nocb_lock to release. */
-static void rcu_nocb_unlock_irqrestore(struct rcu_data *rdp,
- unsigned long flags)
-{
- local_irq_restore(flags);
-}
-
-/* Lockdep check that ->cblist may be safely accessed. */
-static void rcu_lockdep_assert_cblist_protected(struct rcu_data *rdp)
-{
- lockdep_assert_irqs_disabled();
-}
-
-static void rcu_nocb_gp_cleanup(struct swait_queue_head *sq)
-{
-}
-
-static struct swait_queue_head *rcu_nocb_gp_get(struct rcu_node *rnp)
-{
- return NULL;
-}
-
-static void rcu_init_one_nocb(struct rcu_node *rnp)
-{
-}
-
-static bool rcu_nocb_flush_bypass(struct rcu_data *rdp, struct rcu_head *rhp,
- unsigned long j)
-{
- return true;
-}
-
-static bool rcu_nocb_try_bypass(struct rcu_data *rdp, struct rcu_head *rhp,
- bool *was_alldone, unsigned long flags)
-{
- return false;
-}
-
-static void __call_rcu_nocb_wake(struct rcu_data *rdp, bool was_empty,
- unsigned long flags)
-{
- WARN_ON_ONCE(1); /* Should be dead code! */
-}
-
-static void __init rcu_boot_init_nocb_percpu_data(struct rcu_data *rdp)
-{
-}
-
-static int rcu_nocb_need_deferred_wakeup(struct rcu_data *rdp)
-{
- return false;
-}
-
-static void do_nocb_deferred_wakeup(struct rcu_data *rdp)
-{
-}
-
-static void rcu_spawn_cpu_nocb_kthread(int cpu)
-{
-}
-
-static void __init rcu_spawn_nocb_kthreads(void)
-{
-}
-
-static void show_rcu_nocb_state(struct rcu_data *rdp)
-{
-}
-
-#endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */
-
/*
* Is this CPU a NO_HZ_FULL CPU that should ignore RCU so that the
* grace-period kthread will do force_quiescent_state() processing?
@@ -2522,14 +1278,14 @@ static void show_rcu_nocb_state(struct rcu_data *rdp)
* CPU unless the grace period has extended for too long.
*
* This code relies on the fact that all NO_HZ_FULL CPUs are also
- * CONFIG_RCU_NOCB_CPU CPUs.
+ * RCU_NOCB_CPU CPUs.
*/
static bool rcu_nohz_full_cpu(void)
{
#ifdef CONFIG_NO_HZ_FULL
if (tick_nohz_full_cpu(smp_processor_id()) &&
(!rcu_gp_in_progress() ||
- ULONG_CMP_LT(jiffies, READ_ONCE(rcu_state.gp_start) + HZ)))
+ time_before(jiffies, READ_ONCE(rcu_state.gp_start) + HZ)))
return true;
#endif /* #ifdef CONFIG_NO_HZ_FULL */
return false;
@@ -2542,21 +1298,5 @@ static void rcu_bind_gp_kthread(void)
{
if (!tick_nohz_full_enabled())
return;
- housekeeping_affine(current, HK_FLAG_RCU);
-}
-
-/* Record the current task on dyntick-idle entry. */
-static void rcu_dynticks_task_enter(void)
-{
-#if defined(CONFIG_TASKS_RCU) && defined(CONFIG_NO_HZ_FULL)
- WRITE_ONCE(current->rcu_tasks_idle_cpu, smp_processor_id());
-#endif /* #if defined(CONFIG_TASKS_RCU) && defined(CONFIG_NO_HZ_FULL) */
-}
-
-/* Record no current task on dyntick-idle exit. */
-static void rcu_dynticks_task_exit(void)
-{
-#if defined(CONFIG_TASKS_RCU) && defined(CONFIG_NO_HZ_FULL)
- WRITE_ONCE(current->rcu_tasks_idle_cpu, -1);
-#endif /* #if defined(CONFIG_TASKS_RCU) && defined(CONFIG_NO_HZ_FULL) */
+ housekeeping_affine(current, HK_TYPE_RCU);
}
diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h
index 55f9b84790d3..5653560573e2 100644
--- a/kernel/rcu/tree_stall.h
+++ b/kernel/rcu/tree_stall.h
@@ -7,19 +7,52 @@
* Author: Paul E. McKenney <paulmck@linux.ibm.com>
*/
+#include <linux/kvm_para.h>
+
//////////////////////////////////////////////////////////////////////////////
//
// Controlling CPU stall warnings, including delay calculation.
/* panic() on RCU Stall sysctl. */
int sysctl_panic_on_rcu_stall __read_mostly;
+int sysctl_max_rcu_stall_to_panic __read_mostly;
#ifdef CONFIG_PROVE_RCU
-#define RCU_STALL_DELAY_DELTA (5 * HZ)
+#define RCU_STALL_DELAY_DELTA (5 * HZ)
#else
-#define RCU_STALL_DELAY_DELTA 0
+#define RCU_STALL_DELAY_DELTA 0
+#endif
+#define RCU_STALL_MIGHT_DIV 8
+#define RCU_STALL_MIGHT_MIN (2 * HZ)
+
+int rcu_exp_jiffies_till_stall_check(void)
+{
+ int cpu_stall_timeout = READ_ONCE(rcu_exp_cpu_stall_timeout);
+ int exp_stall_delay_delta = 0;
+ int till_stall_check;
+
+ // Zero says to use rcu_cpu_stall_timeout, but in milliseconds.
+ if (!cpu_stall_timeout)
+ cpu_stall_timeout = jiffies_to_msecs(rcu_jiffies_till_stall_check());
+
+ // Limit check must be consistent with the Kconfig limits for
+ // CONFIG_RCU_EXP_CPU_STALL_TIMEOUT, so check the allowed range.
+ // The minimum clamped value is "2UL", because at least one full
+ // tick has to be guaranteed.
+ till_stall_check = clamp(msecs_to_jiffies(cpu_stall_timeout), 2UL, 21UL * HZ);
+
+ if (cpu_stall_timeout && jiffies_to_msecs(till_stall_check) != cpu_stall_timeout)
+ WRITE_ONCE(rcu_exp_cpu_stall_timeout, jiffies_to_msecs(till_stall_check));
+
+#ifdef CONFIG_PROVE_RCU
+ /* Add extra ~25% out of till_stall_check. */
+ exp_stall_delay_delta = ((till_stall_check * 25) / 100) + 1;
#endif
+ return till_stall_check + exp_stall_delay_delta;
+}
+EXPORT_SYMBOL_GPL(rcu_exp_jiffies_till_stall_check);
+
/* Limit-check stall timeouts specified at boottime and runtime. */
int rcu_jiffies_till_stall_check(void)
{
@@ -40,6 +73,36 @@ int rcu_jiffies_till_stall_check(void)
}
EXPORT_SYMBOL_GPL(rcu_jiffies_till_stall_check);
+/**
+ * rcu_gp_might_be_stalled - Is it likely that the grace period is stalled?
+ *
+ * Returns @true if the current grace period is sufficiently old that
+ * it is reasonable to assume that it might be stalled. This can be
+ * useful when deciding whether to allocate memory to enable RCU-mediated
+ * freeing on the one hand or just invoking synchronize_rcu() on the other.
+ * The latter is preferable when the grace period is stalled.
+ *
+ * Note that sampling of the .gp_start and .gp_seq fields must be done
+ * carefully to avoid false positives at the beginnings and ends of
+ * grace periods.
+ */
+bool rcu_gp_might_be_stalled(void)
+{
+ unsigned long d = rcu_jiffies_till_stall_check() / RCU_STALL_MIGHT_DIV;
+ unsigned long j = jiffies;
+
+ if (d < RCU_STALL_MIGHT_MIN)
+ d = RCU_STALL_MIGHT_MIN;
+ smp_mb(); // jiffies before .gp_seq to avoid false positives.
+ if (!rcu_gp_in_progress())
+ return false;
+ // Long delays at this point avoids false positive, but a delay
+ // of ULONG_MAX/4 jiffies voids your no-false-positive warranty.
+ smp_mb(); // .gp_seq before second .gp_start
+ // And ditto here.
+ return !time_before(j, READ_ONCE(rcu_state.gp_start) + d);
+}
+
/* Don't do RCU CPU stall warnings during long sysrq printouts. */
void rcu_sysrq_start(void)
{
@@ -74,22 +137,24 @@ early_initcall(check_cpu_stall_init);
/* If so specified via sysctl, panic, yielding cleaner stall-warning output. */
static void panic_on_rcu_stall(void)
{
+ static int cpu_stall;
+
+ if (++cpu_stall < sysctl_max_rcu_stall_to_panic)
+ return;
+
if (sysctl_panic_on_rcu_stall)
panic("RCU Stall\n");
}
/**
- * rcu_cpu_stall_reset - prevent further stall warnings in current grace period
- *
- * Set the stall-warning timeout way off into the future, thus preventing
- * any RCU CPU stall-warning messages from appearing in the current set of
- * RCU grace periods.
+ * rcu_cpu_stall_reset - restart stall-warning timeout for current grace period
*
* The caller must disable hard irqs.
*/
void rcu_cpu_stall_reset(void)
{
- WRITE_ONCE(rcu_state.jiffies_stall, jiffies + ULONG_MAX / 2);
+ WRITE_ONCE(rcu_state.jiffies_stall,
+ jiffies + rcu_jiffies_till_stall_check());
}
//////////////////////////////////////////////////////////////////////////////
@@ -102,10 +167,10 @@ static void record_gp_stall_check_time(void)
unsigned long j = jiffies;
unsigned long j1;
- rcu_state.gp_start = j;
+ WRITE_ONCE(rcu_state.gp_start, j);
j1 = rcu_jiffies_till_stall_check();
- /* Record ->gp_start before ->jiffies_stall. */
- smp_store_release(&rcu_state.jiffies_stall, j + j1); /* ^^^ */
+ smp_mb(); // ->gp_start before ->jiffies_stall and caller's ->gp_seq.
+ WRITE_ONCE(rcu_state.jiffies_stall, j + j1);
rcu_state.jiffies_resched = j + j1 / 2;
rcu_state.n_force_qs_gpstart = READ_ONCE(rcu_state.n_force_qs);
}
@@ -126,7 +191,7 @@ static void rcu_stall_kick_kthreads(void)
{
unsigned long j;
- if (!rcu_kick_kthreads)
+ if (!READ_ONCE(rcu_kick_kthreads))
return;
j = READ_ONCE(rcu_state.jiffies_kick_kthreads);
if (time_after(jiffies, j) && rcu_state.gp_kthread &&
@@ -192,23 +257,71 @@ static void rcu_print_detail_task_stall_rnp(struct rcu_node *rnp)
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
}
+// Communicate task state back to the RCU CPU stall warning request.
+struct rcu_stall_chk_rdr {
+ int nesting;
+ union rcu_special rs;
+ bool on_blkd_list;
+};
+
+/*
+ * Report out the state of a not-running task that is stalling the
+ * current RCU grace period.
+ */
+static int check_slow_task(struct task_struct *t, void *arg)
+{
+ struct rcu_stall_chk_rdr *rscrp = arg;
+
+ if (task_curr(t))
+ return -EBUSY; // It is running, so decline to inspect it.
+ rscrp->nesting = t->rcu_read_lock_nesting;
+ rscrp->rs = t->rcu_read_unlock_special;
+ rscrp->on_blkd_list = !list_empty(&t->rcu_node_entry);
+ return 0;
+}
+
/*
* Scan the current list of tasks blocked within RCU read-side critical
- * sections, printing out the tid of each.
+ * sections, printing out the tid of each of the first few of them.
*/
-static int rcu_print_task_stall(struct rcu_node *rnp)
+static int rcu_print_task_stall(struct rcu_node *rnp, unsigned long flags)
+ __releases(rnp->lock)
{
- struct task_struct *t;
+ int i = 0;
int ndetected = 0;
+ struct rcu_stall_chk_rdr rscr;
+ struct task_struct *t;
+ struct task_struct *ts[8];
- if (!rcu_preempt_blocked_readers_cgp(rnp))
+ lockdep_assert_irqs_disabled();
+ if (!rcu_preempt_blocked_readers_cgp(rnp)) {
+ raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
return 0;
+ }
pr_err("\tTasks blocked on level-%d rcu_node (CPUs %d-%d):",
rnp->level, rnp->grplo, rnp->grphi);
t = list_entry(rnp->gp_tasks->prev,
struct task_struct, rcu_node_entry);
list_for_each_entry_continue(t, &rnp->blkd_tasks, rcu_node_entry) {
- pr_cont(" P%d", t->pid);
+ get_task_struct(t);
+ ts[i++] = t;
+ if (i >= ARRAY_SIZE(ts))
+ break;
+ }
+ raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
+ while (i) {
+ t = ts[--i];
+ if (task_call_func(t, check_slow_task, &rscr))
+ pr_cont(" P%d", t->pid);
+ else
+ pr_cont(" P%d/%d:%c%c%c%c",
+ t->pid, rscr.nesting,
+ ".b"[rscr.rs.b.blocked],
+ ".q"[rscr.rs.b.need_qs],
+ ".e"[rscr.rs.b.exp_hint],
+ ".l"[rscr.on_blkd_list]);
+ lockdep_assert_irqs_disabled();
+ put_task_struct(t);
ndetected++;
}
pr_cont("\n");
@@ -229,8 +342,10 @@ static void rcu_print_detail_task_stall_rnp(struct rcu_node *rnp)
* Because preemptible RCU does not exist, we never have to check for
* tasks blocked within RCU read-side critical sections.
*/
-static int rcu_print_task_stall(struct rcu_node *rnp)
+static int rcu_print_task_stall(struct rcu_node *rnp, unsigned long flags)
+ __releases(rnp->lock)
{
+ raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
return 0;
}
#endif /* #else #ifdef CONFIG_PREEMPT_RCU */
@@ -250,33 +365,16 @@ static void rcu_dump_cpu_stacks(void)
rcu_for_each_leaf_node(rnp) {
raw_spin_lock_irqsave_rcu_node(rnp, flags);
for_each_leaf_node_possible_cpu(rnp, cpu)
- if (rnp->qsmask & leaf_node_cpu_bit(rnp, cpu))
- if (!trigger_single_cpu_backtrace(cpu))
+ if (rnp->qsmask & leaf_node_cpu_bit(rnp, cpu)) {
+ if (cpu_is_offline(cpu))
+ pr_err("Offline CPU %d blocking current GP.\n", cpu);
+ else
dump_cpu_task(cpu);
+ }
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
}
}
-#ifdef CONFIG_RCU_FAST_NO_HZ
-
-static void print_cpu_stall_fast_no_hz(char *cp, int cpu)
-{
- struct rcu_data *rdp = &per_cpu(rcu_data, cpu);
-
- sprintf(cp, "last_accelerate: %04lx/%04lx dyntick_enabled: %d",
- rdp->last_accelerate & 0xffff, jiffies & 0xffff,
- !!rdp->tick_nohz_enabled_snap);
-}
-
-#else /* #ifdef CONFIG_RCU_FAST_NO_HZ */
-
-static void print_cpu_stall_fast_no_hz(char *cp, int cpu)
-{
- *cp = '\0';
-}
-
-#endif /* #else #ifdef CONFIG_RCU_FAST_NO_HZ */
-
static const char * const gp_state_names[] = {
[RCU_GP_IDLE] = "RCU_GP_IDLE",
[RCU_GP_WAIT_GPS] = "RCU_GP_WAIT_GPS",
@@ -299,6 +397,37 @@ static const char *gp_state_getname(short gs)
return gp_state_names[gs];
}
+/* Is the RCU grace-period kthread being starved of CPU time? */
+static bool rcu_is_gp_kthread_starving(unsigned long *jp)
+{
+ unsigned long j = jiffies - READ_ONCE(rcu_state.gp_activity);
+
+ if (jp)
+ *jp = j;
+ return j > 2 * HZ;
+}
+
+static bool rcu_is_rcuc_kthread_starving(struct rcu_data *rdp, unsigned long *jp)
+{
+ int cpu;
+ struct task_struct *rcuc;
+ unsigned long j;
+
+ rcuc = rdp->rcu_cpu_kthread_task;
+ if (!rcuc)
+ return false;
+
+ cpu = task_cpu(rcuc);
+ if (cpu_is_offline(cpu) || idle_cpu(cpu))
+ return false;
+
+ j = jiffies - READ_ONCE(rdp->rcuc_activity);
+
+ if (jp)
+ *jp = j;
+ return j > 2 * HZ;
+}
+
/*
* Print out diagnostic information for the specified stalled CPU.
*
@@ -308,15 +437,18 @@ static const char *gp_state_getname(short gs)
* of RCU grace periods that this CPU is ignorant of, for example, "1"
* if the CPU was aware of the previous grace period.
*
- * Also print out idle and (if CONFIG_RCU_FAST_NO_HZ) idle-entry info.
+ * Also print out idle info.
*/
static void print_cpu_stall_info(int cpu)
{
unsigned long delta;
- char fast_no_hz[72];
+ bool falsepositive;
struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
char *ticks_title;
unsigned long ticks_value;
+ bool rcuc_starved;
+ unsigned long j;
+ char buf[32];
/*
* We could be printing a lot while holding a spinlock. Avoid
@@ -331,9 +463,13 @@ static void print_cpu_stall_info(int cpu)
ticks_title = "ticks this GP";
ticks_value = rdp->ticks_this_gp;
}
- print_cpu_stall_fast_no_hz(fast_no_hz, cpu);
delta = rcu_seq_ctr(rdp->mynode->gp_seq - rdp->rcu_iw_gp_seq);
- pr_err("\t%d-%c%c%c%c: (%lu %s) idle=%03x/%ld/%#lx softirq=%u/%u fqs=%ld %s\n",
+ falsepositive = rcu_is_gp_kthread_starving(NULL) &&
+ rcu_dynticks_in_eqs(rcu_dynticks_snap(cpu));
+ rcuc_starved = rcu_is_rcuc_kthread_starving(rdp, &j);
+ if (rcuc_starved)
+ sprintf(buf, " rcuc=%ld jiffies(starved)", j);
+ pr_err("\t%d-%c%c%c%c: (%lu %s) idle=%04x/%ld/%#lx softirq=%u/%u fqs=%ld%s%s\n",
cpu,
"O."[!!cpu_online(cpu)],
"o."[!!(rdp->grpmask & rdp->mynode->qsmaskinit)],
@@ -342,36 +478,78 @@ static void print_cpu_stall_info(int cpu)
rdp->rcu_iw_pending ? (int)min(delta, 9UL) + '0' :
"!."[!delta],
ticks_value, ticks_title,
- rcu_dynticks_snap(rdp) & 0xfff,
- rdp->dynticks_nesting, rdp->dynticks_nmi_nesting,
+ rcu_dynticks_snap(cpu) & 0xffff,
+ ct_dynticks_nesting_cpu(cpu), ct_dynticks_nmi_nesting_cpu(cpu),
rdp->softirq_snap, kstat_softirqs_cpu(RCU_SOFTIRQ, cpu),
- READ_ONCE(rcu_state.n_force_qs) - rcu_state.n_force_qs_gpstart,
- fast_no_hz);
+ data_race(rcu_state.n_force_qs) - rcu_state.n_force_qs_gpstart,
+ rcuc_starved ? buf : "",
+ falsepositive ? " (false positive?)" : "");
}
/* Complain about starvation of grace-period kthread. */
static void rcu_check_gp_kthread_starvation(void)
{
+ int cpu;
struct task_struct *gpk = rcu_state.gp_kthread;
unsigned long j;
- j = jiffies - READ_ONCE(rcu_state.gp_activity);
- if (j > 2 * HZ) {
- pr_err("%s kthread starved for %ld jiffies! g%ld f%#x %s(%d) ->state=%#lx ->cpu=%d\n",
+ if (rcu_is_gp_kthread_starving(&j)) {
+ cpu = gpk ? task_cpu(gpk) : -1;
+ pr_err("%s kthread starved for %ld jiffies! g%ld f%#x %s(%d) ->state=%#x ->cpu=%d\n",
rcu_state.name, j,
(long)rcu_seq_current(&rcu_state.gp_seq),
- READ_ONCE(rcu_state.gp_flags),
- gp_state_getname(rcu_state.gp_state), rcu_state.gp_state,
- gpk ? gpk->state : ~0, gpk ? task_cpu(gpk) : -1);
+ data_race(READ_ONCE(rcu_state.gp_flags)),
+ gp_state_getname(rcu_state.gp_state),
+ data_race(READ_ONCE(rcu_state.gp_state)),
+ gpk ? data_race(READ_ONCE(gpk->__state)) : ~0, cpu);
if (gpk) {
+ pr_err("\tUnless %s kthread gets sufficient CPU time, OOM is now expected behavior.\n", rcu_state.name);
pr_err("RCU grace-period kthread stack dump:\n");
sched_show_task(gpk);
+ if (cpu >= 0) {
+ if (cpu_is_offline(cpu)) {
+ pr_err("RCU GP kthread last ran on offline CPU %d.\n", cpu);
+ } else {
+ pr_err("Stack dump where RCU GP kthread last ran:\n");
+ dump_cpu_task(cpu);
+ }
+ }
wake_up_process(gpk);
}
}
}
-static void print_other_cpu_stall(unsigned long gp_seq)
+/* Complain about missing wakeups from expired fqs wait timer */
+static void rcu_check_gp_kthread_expired_fqs_timer(void)
+{
+ struct task_struct *gpk = rcu_state.gp_kthread;
+ short gp_state;
+ unsigned long jiffies_fqs;
+ int cpu;
+
+ /*
+ * Order reads of .gp_state and .jiffies_force_qs.
+ * Matching smp_wmb() is present in rcu_gp_fqs_loop().
+ */
+ gp_state = smp_load_acquire(&rcu_state.gp_state);
+ jiffies_fqs = READ_ONCE(rcu_state.jiffies_force_qs);
+
+ if (gp_state == RCU_GP_WAIT_FQS &&
+ time_after(jiffies, jiffies_fqs + RCU_STALL_MIGHT_MIN) &&
+ gpk && !READ_ONCE(gpk->on_rq)) {
+ cpu = task_cpu(gpk);
+ pr_err("%s kthread timer wakeup didn't happen for %ld jiffies! g%ld f%#x %s(%d) ->state=%#x\n",
+ rcu_state.name, (jiffies - jiffies_fqs),
+ (long)rcu_seq_current(&rcu_state.gp_seq),
+ data_race(rcu_state.gp_flags),
+ gp_state_getname(RCU_GP_WAIT_FQS), RCU_GP_WAIT_FQS,
+ data_race(READ_ONCE(gpk->__state)));
+ pr_err("\tPossible timer handling issue on cpu=%d timer-softirq=%u\n",
+ cpu, kstat_softirqs_cpu(TIMER_SOFTIRQ, cpu));
+ }
+}
+
+static void print_other_cpu_stall(unsigned long gp_seq, unsigned long gps)
{
int cpu;
unsigned long flags;
@@ -381,20 +559,22 @@ static void print_other_cpu_stall(unsigned long gp_seq)
struct rcu_node *rnp;
long totqlen = 0;
+ lockdep_assert_irqs_disabled();
+
/* Kick and suppress, if so configured. */
rcu_stall_kick_kthreads();
- if (rcu_cpu_stall_suppress)
+ if (rcu_stall_is_suppressed())
return;
/*
* OK, time to rat on our buddy...
- * See Documentation/RCU/stallwarn.txt for info on how to debug
+ * See Documentation/RCU/stallwarn.rst for info on how to debug
* RCU CPU stall warnings.
*/
+ trace_rcu_stall_warning(rcu_state.name, TPS("StallDetected"));
pr_err("INFO: %s detected stalls on CPUs/tasks:\n", rcu_state.name);
rcu_for_each_leaf_node(rnp) {
raw_spin_lock_irqsave_rcu_node(rnp, flags);
- ndetected += rcu_print_task_stall(rnp);
if (rnp->qsmask != 0) {
for_each_leaf_node_possible_cpu(rnp, cpu)
if (rnp->qsmask & leaf_node_cpu_bit(rnp, cpu)) {
@@ -402,14 +582,15 @@ static void print_other_cpu_stall(unsigned long gp_seq)
ndetected++;
}
}
- raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
+ ndetected += rcu_print_task_stall(rnp, flags); // Releases rnp->lock.
+ lockdep_assert_irqs_disabled();
}
for_each_possible_cpu(cpu)
totqlen += rcu_get_n_cbs_cpu(cpu);
- pr_cont("\t(detected by %d, t=%ld jiffies, g=%ld, q=%lu)\n",
- smp_processor_id(), (long)(jiffies - rcu_state.gp_start),
- (long)rcu_seq_current(&rcu_state.gp_seq), totqlen);
+ pr_cont("\t(detected by %d, t=%ld jiffies, g=%ld, q=%lu ncpus=%d)\n",
+ smp_processor_id(), (long)(jiffies - gps),
+ (long)rcu_seq_current(&rcu_state.gp_seq), totqlen, rcu_state.n_online_cpus);
if (ndetected) {
rcu_dump_cpu_stacks();
@@ -421,13 +602,11 @@ static void print_other_cpu_stall(unsigned long gp_seq)
pr_err("INFO: Stall ended before state dump start\n");
} else {
j = jiffies;
- gpa = READ_ONCE(rcu_state.gp_activity);
+ gpa = data_race(READ_ONCE(rcu_state.gp_activity));
pr_err("All QSes seen, last %s kthread activity %ld (%ld-%ld), jiffies_till_next_fqs=%ld, root ->qsmask %#lx\n",
rcu_state.name, j - gpa, j, gpa,
- READ_ONCE(jiffies_till_next_fqs),
- rcu_get_root()->qsmask);
- /* In this case, the current CPU might be at fault. */
- sched_show_task(current);
+ data_race(READ_ONCE(jiffies_till_next_fqs)),
+ data_race(READ_ONCE(rcu_get_root()->qsmask)));
}
}
/* Rewrite if needed in case of slow consoles. */
@@ -435,6 +614,7 @@ static void print_other_cpu_stall(unsigned long gp_seq)
WRITE_ONCE(rcu_state.jiffies_stall,
jiffies + 3 * rcu_jiffies_till_stall_check() + 3);
+ rcu_check_gp_kthread_expired_fqs_timer();
rcu_check_gp_kthread_starvation();
panic_on_rcu_stall();
@@ -442,7 +622,7 @@ static void print_other_cpu_stall(unsigned long gp_seq)
rcu_force_quiescent_state(); /* Kick them all. */
}
-static void print_cpu_stall(void)
+static void print_cpu_stall(unsigned long gps)
{
int cpu;
unsigned long flags;
@@ -450,26 +630,30 @@ static void print_cpu_stall(void)
struct rcu_node *rnp = rcu_get_root();
long totqlen = 0;
+ lockdep_assert_irqs_disabled();
+
/* Kick and suppress, if so configured. */
rcu_stall_kick_kthreads();
- if (rcu_cpu_stall_suppress)
+ if (rcu_stall_is_suppressed())
return;
/*
* OK, time to rat on ourselves...
- * See Documentation/RCU/stallwarn.txt for info on how to debug
+ * See Documentation/RCU/stallwarn.rst for info on how to debug
* RCU CPU stall warnings.
*/
+ trace_rcu_stall_warning(rcu_state.name, TPS("SelfDetected"));
pr_err("INFO: %s self-detected stall on CPU\n", rcu_state.name);
raw_spin_lock_irqsave_rcu_node(rdp->mynode, flags);
print_cpu_stall_info(smp_processor_id());
raw_spin_unlock_irqrestore_rcu_node(rdp->mynode, flags);
for_each_possible_cpu(cpu)
totqlen += rcu_get_n_cbs_cpu(cpu);
- pr_cont("\t(t=%lu jiffies g=%ld q=%lu)\n",
- jiffies - rcu_state.gp_start,
- (long)rcu_seq_current(&rcu_state.gp_seq), totqlen);
+ pr_cont("\t(t=%lu jiffies g=%ld q=%lu ncpus=%d)\n",
+ jiffies - gps,
+ (long)rcu_seq_current(&rcu_state.gp_seq), totqlen, rcu_state.n_online_cpus);
+ rcu_check_gp_kthread_expired_fqs_timer();
rcu_check_gp_kthread_starvation();
rcu_dump_cpu_stacks();
@@ -496,6 +680,7 @@ static void print_cpu_stall(void)
static void check_cpu_stall(struct rcu_data *rdp)
{
+ bool didstall = false;
unsigned long gs1;
unsigned long gs2;
unsigned long gps;
@@ -504,7 +689,8 @@ static void check_cpu_stall(struct rcu_data *rdp)
unsigned long js;
struct rcu_node *rnp;
- if ((rcu_cpu_stall_suppress && !rcu_kick_kthreads) ||
+ lockdep_assert_irqs_disabled();
+ if ((rcu_stall_is_suppressed() && !READ_ONCE(rcu_kick_kthreads)) ||
!rcu_gp_in_progress())
return;
rcu_stall_kick_kthreads();
@@ -540,24 +726,46 @@ static void check_cpu_stall(struct rcu_data *rdp)
ULONG_CMP_GE(gps, js))
return; /* No stall or GP completed since entering function. */
rnp = rdp->mynode;
- jn = jiffies + 3 * rcu_jiffies_till_stall_check() + 3;
+ jn = jiffies + ULONG_MAX / 2;
if (rcu_gp_in_progress() &&
(READ_ONCE(rnp->qsmask) & rdp->grpmask) &&
cmpxchg(&rcu_state.jiffies_stall, js, jn) == js) {
+ /*
+ * If a virtual machine is stopped by the host it can look to
+ * the watchdog like an RCU stall. Check to see if the host
+ * stopped the vm.
+ */
+ if (kvm_check_and_clear_guest_paused())
+ return;
+
/* We haven't checked in, so go dump stack. */
- print_cpu_stall();
- if (rcu_cpu_stall_ftrace_dump)
+ print_cpu_stall(gps);
+ if (READ_ONCE(rcu_cpu_stall_ftrace_dump))
rcu_ftrace_dump(DUMP_ALL);
+ didstall = true;
} else if (rcu_gp_in_progress() &&
ULONG_CMP_GE(j, js + RCU_STALL_RAT_DELAY) &&
cmpxchg(&rcu_state.jiffies_stall, js, jn) == js) {
+ /*
+ * If a virtual machine is stopped by the host it can look to
+ * the watchdog like an RCU stall. Check to see if the host
+ * stopped the vm.
+ */
+ if (kvm_check_and_clear_guest_paused())
+ return;
+
/* They had a few time units to dump stack, so complain. */
- print_other_cpu_stall(gs2);
- if (rcu_cpu_stall_ftrace_dump)
+ print_other_cpu_stall(gs2, gps);
+ if (READ_ONCE(rcu_cpu_stall_ftrace_dump))
rcu_ftrace_dump(DUMP_ALL);
+ didstall = true;
+ }
+ if (didstall && READ_ONCE(rcu_state.jiffies_stall) == jn) {
+ jn = jiffies + 3 * rcu_jiffies_till_stall_check() + 3;
+ WRITE_ONCE(rcu_state.jiffies_stall, jn);
}
}
@@ -567,54 +775,127 @@ static void check_cpu_stall(struct rcu_data *rdp)
/*
+ * Check to see if a failure to end RCU priority inversion was due to
+ * a CPU not passing through a quiescent state. When this happens, there
+ * is nothing that RCU priority boosting can do to help, so we shouldn't
+ * count this as an RCU priority boosting failure. A return of true says
+ * RCU priority boosting is to blame, and false says otherwise. If false
+ * is returned, the first of the CPUs to blame is stored through cpup.
+ * If there was no CPU blocking the current grace period, but also nothing
+ * in need of being boosted, *cpup is set to -1. This can happen in case
+ * of vCPU preemption while the last CPU is reporting its quiscent state,
+ * for example.
+ *
+ * If cpup is NULL, then a lockless quick check is carried out, suitable
+ * for high-rate usage. On the other hand, if cpup is non-NULL, each
+ * rcu_node structure's ->lock is acquired, ruling out high-rate usage.
+ */
+bool rcu_check_boost_fail(unsigned long gp_state, int *cpup)
+{
+ bool atb = false;
+ int cpu;
+ unsigned long flags;
+ struct rcu_node *rnp;
+
+ rcu_for_each_leaf_node(rnp) {
+ if (!cpup) {
+ if (data_race(READ_ONCE(rnp->qsmask))) {
+ return false;
+ } else {
+ if (READ_ONCE(rnp->gp_tasks))
+ atb = true;
+ continue;
+ }
+ }
+ *cpup = -1;
+ raw_spin_lock_irqsave_rcu_node(rnp, flags);
+ if (rnp->gp_tasks)
+ atb = true;
+ if (!rnp->qsmask) {
+ // No CPUs without quiescent states for this rnp.
+ raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
+ continue;
+ }
+ // Find the first holdout CPU.
+ for_each_leaf_node_possible_cpu(rnp, cpu) {
+ if (rnp->qsmask & (1UL << (cpu - rnp->grplo))) {
+ raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
+ *cpup = cpu;
+ return false;
+ }
+ }
+ raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
+ }
+ // Can't blame CPUs, so must blame RCU priority boosting.
+ return atb;
+}
+EXPORT_SYMBOL_GPL(rcu_check_boost_fail);
+
+/*
* Show the state of the grace-period kthreads.
*/
void show_rcu_gp_kthreads(void)
{
+ unsigned long cbs = 0;
int cpu;
unsigned long j;
unsigned long ja;
unsigned long jr;
+ unsigned long js;
unsigned long jw;
struct rcu_data *rdp;
struct rcu_node *rnp;
+ struct task_struct *t = READ_ONCE(rcu_state.gp_kthread);
j = jiffies;
- ja = j - READ_ONCE(rcu_state.gp_activity);
- jr = j - READ_ONCE(rcu_state.gp_req_activity);
- jw = j - READ_ONCE(rcu_state.gp_wake_time);
- pr_info("%s: wait state: %s(%d) ->state: %#lx delta ->gp_activity %lu ->gp_req_activity %lu ->gp_wake_time %lu ->gp_wake_seq %ld ->gp_seq %ld ->gp_seq_needed %ld ->gp_flags %#x\n",
+ ja = j - data_race(READ_ONCE(rcu_state.gp_activity));
+ jr = j - data_race(READ_ONCE(rcu_state.gp_req_activity));
+ js = j - data_race(READ_ONCE(rcu_state.gp_start));
+ jw = j - data_race(READ_ONCE(rcu_state.gp_wake_time));
+ pr_info("%s: wait state: %s(%d) ->state: %#x ->rt_priority %u delta ->gp_start %lu ->gp_activity %lu ->gp_req_activity %lu ->gp_wake_time %lu ->gp_wake_seq %ld ->gp_seq %ld ->gp_seq_needed %ld ->gp_max %lu ->gp_flags %#x\n",
rcu_state.name, gp_state_getname(rcu_state.gp_state),
- rcu_state.gp_state,
- rcu_state.gp_kthread ? rcu_state.gp_kthread->state : 0x1ffffL,
- ja, jr, jw, (long)READ_ONCE(rcu_state.gp_wake_seq),
- (long)READ_ONCE(rcu_state.gp_seq),
- (long)READ_ONCE(rcu_get_root()->gp_seq_needed),
- READ_ONCE(rcu_state.gp_flags));
+ data_race(READ_ONCE(rcu_state.gp_state)),
+ t ? data_race(READ_ONCE(t->__state)) : 0x1ffff, t ? t->rt_priority : 0xffU,
+ js, ja, jr, jw, (long)data_race(READ_ONCE(rcu_state.gp_wake_seq)),
+ (long)data_race(READ_ONCE(rcu_state.gp_seq)),
+ (long)data_race(READ_ONCE(rcu_get_root()->gp_seq_needed)),
+ data_race(READ_ONCE(rcu_state.gp_max)),
+ data_race(READ_ONCE(rcu_state.gp_flags)));
rcu_for_each_node_breadth_first(rnp) {
- if (ULONG_CMP_GE(rcu_state.gp_seq, rnp->gp_seq_needed))
+ if (ULONG_CMP_GE(READ_ONCE(rcu_state.gp_seq), READ_ONCE(rnp->gp_seq_needed)) &&
+ !data_race(READ_ONCE(rnp->qsmask)) && !data_race(READ_ONCE(rnp->boost_tasks)) &&
+ !data_race(READ_ONCE(rnp->exp_tasks)) && !data_race(READ_ONCE(rnp->gp_tasks)))
continue;
- pr_info("\trcu_node %d:%d ->gp_seq %ld ->gp_seq_needed %ld\n",
- rnp->grplo, rnp->grphi, (long)rnp->gp_seq,
- (long)rnp->gp_seq_needed);
+ pr_info("\trcu_node %d:%d ->gp_seq %ld ->gp_seq_needed %ld ->qsmask %#lx %c%c%c%c ->n_boosts %ld\n",
+ rnp->grplo, rnp->grphi,
+ (long)data_race(READ_ONCE(rnp->gp_seq)),
+ (long)data_race(READ_ONCE(rnp->gp_seq_needed)),
+ data_race(READ_ONCE(rnp->qsmask)),
+ ".b"[!!data_race(READ_ONCE(rnp->boost_kthread_task))],
+ ".B"[!!data_race(READ_ONCE(rnp->boost_tasks))],
+ ".E"[!!data_race(READ_ONCE(rnp->exp_tasks))],
+ ".G"[!!data_race(READ_ONCE(rnp->gp_tasks))],
+ data_race(READ_ONCE(rnp->n_boosts)));
if (!rcu_is_leaf_node(rnp))
continue;
for_each_leaf_node_possible_cpu(rnp, cpu) {
rdp = per_cpu_ptr(&rcu_data, cpu);
- if (rdp->gpwrap ||
- ULONG_CMP_GE(rcu_state.gp_seq,
- rdp->gp_seq_needed))
+ if (READ_ONCE(rdp->gpwrap) ||
+ ULONG_CMP_GE(READ_ONCE(rcu_state.gp_seq),
+ READ_ONCE(rdp->gp_seq_needed)))
continue;
pr_info("\tcpu %d ->gp_seq_needed %ld\n",
- cpu, (long)rdp->gp_seq_needed);
+ cpu, (long)data_race(READ_ONCE(rdp->gp_seq_needed)));
}
}
for_each_possible_cpu(cpu) {
rdp = per_cpu_ptr(&rcu_data, cpu);
+ cbs += data_race(READ_ONCE(rdp->n_cbs_invoked));
if (rcu_segcblist_is_offloaded(&rdp->cblist))
show_rcu_nocb_state(rdp);
}
- /* sched_show_task(rcu_state.gp_kthread); */
+ pr_info("RCU callbacks invoked since boot: %lu\n", cbs);
+ show_rcu_tasks_gp_kthreads();
}
EXPORT_SYMBOL_GPL(show_rcu_gp_kthreads);
@@ -631,7 +912,9 @@ static void rcu_check_gp_start_stall(struct rcu_node *rnp, struct rcu_data *rdp,
static atomic_t warned = ATOMIC_INIT(0);
if (!IS_ENABLED(CONFIG_PROVE_RCU) || rcu_gp_in_progress() ||
- ULONG_CMP_GE(rnp_root->gp_seq, rnp_root->gp_seq_needed))
+ ULONG_CMP_GE(READ_ONCE(rnp_root->gp_seq),
+ READ_ONCE(rnp_root->gp_seq_needed)) ||
+ !smp_load_acquire(&rcu_state.gp_kthread)) // Get stable kthread.
return;
j = jiffies; /* Expensive access, and in common case don't get here. */
if (time_before(j, READ_ONCE(rcu_state.gp_req_activity) + gpssdelay) ||
@@ -642,7 +925,8 @@ static void rcu_check_gp_start_stall(struct rcu_node *rnp, struct rcu_data *rdp,
raw_spin_lock_irqsave_rcu_node(rnp, flags);
j = jiffies;
if (rcu_gp_in_progress() ||
- ULONG_CMP_GE(rnp_root->gp_seq, rnp_root->gp_seq_needed) ||
+ ULONG_CMP_GE(READ_ONCE(rnp_root->gp_seq),
+ READ_ONCE(rnp_root->gp_seq_needed)) ||
time_before(j, READ_ONCE(rcu_state.gp_req_activity) + gpssdelay) ||
time_before(j, READ_ONCE(rcu_state.gp_activity) + gpssdelay) ||
atomic_read(&warned)) {
@@ -655,9 +939,10 @@ static void rcu_check_gp_start_stall(struct rcu_node *rnp, struct rcu_data *rdp,
raw_spin_lock_rcu_node(rnp_root); /* irqs already disabled. */
j = jiffies;
if (rcu_gp_in_progress() ||
- ULONG_CMP_GE(rnp_root->gp_seq, rnp_root->gp_seq_needed) ||
- time_before(j, rcu_state.gp_req_activity + gpssdelay) ||
- time_before(j, rcu_state.gp_activity + gpssdelay) ||
+ ULONG_CMP_GE(READ_ONCE(rnp_root->gp_seq),
+ READ_ONCE(rnp_root->gp_seq_needed)) ||
+ time_before(j, READ_ONCE(rcu_state.gp_req_activity) + gpssdelay) ||
+ time_before(j, READ_ONCE(rcu_state.gp_activity) + gpssdelay) ||
atomic_xchg(&warned, 1)) {
if (rnp_root != rnp)
/* irqs remain disabled. */
@@ -687,11 +972,11 @@ void rcu_fwd_progress_check(unsigned long j)
if (rcu_gp_in_progress()) {
pr_info("%s: GP age %lu jiffies\n",
- __func__, jiffies - rcu_state.gp_start);
+ __func__, jiffies - data_race(READ_ONCE(rcu_state.gp_start)));
show_rcu_gp_kthreads();
} else {
pr_info("%s: Last GP end %lu jiffies ago\n",
- __func__, jiffies - rcu_state.gp_end);
+ __func__, jiffies - data_race(READ_ONCE(rcu_state.gp_end)));
preempt_disable();
rdp = this_cpu_ptr(&rcu_data);
rcu_check_gp_start_stall(rdp->mynode, rdp, j);
@@ -724,7 +1009,7 @@ static void sysrq_show_rcu(int key)
show_rcu_gp_kthreads();
}
-static struct sysrq_key_op sysrq_rcudump_op = {
+static const struct sysrq_key_op sysrq_rcudump_op = {
.handler = sysrq_show_rcu,
.help_msg = "show-rcu(y)",
.action_msg = "Show RCU tree",
diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c
index 6c4b862f57d6..738842c4886b 100644
--- a/kernel/rcu/update.c
+++ b/kernel/rcu/update.c
@@ -41,6 +41,8 @@
#include <linux/sched/isolation.h>
#include <linux/kprobes.h>
#include <linux/slab.h>
+#include <linux/irq_work.h>
+#include <linux/rcupdate_trace.h>
#define CREATE_TRACE_POINTS
@@ -52,10 +54,12 @@
#define MODULE_PARAM_PREFIX "rcupdate."
#ifndef CONFIG_TINY_RCU
-module_param(rcu_expedited, int, 0);
-module_param(rcu_normal, int, 0);
-static int rcu_normal_after_boot;
-module_param(rcu_normal_after_boot, int, 0);
+module_param(rcu_expedited, int, 0444);
+module_param(rcu_normal, int, 0444);
+static int rcu_normal_after_boot = IS_ENABLED(CONFIG_PREEMPT_RT);
+#if !defined(CONFIG_PREEMPT_RT) || defined(CONFIG_NO_HZ_FULL)
+module_param(rcu_normal_after_boot, int, 0444);
+#endif
#endif /* #ifndef CONFIG_TINY_RCU */
#ifdef CONFIG_DEBUG_LOCK_ALLOC
@@ -63,12 +67,12 @@ module_param(rcu_normal_after_boot, int, 0);
* rcu_read_lock_held_common() - might we be in RCU-sched read-side critical section?
* @ret: Best guess answer if lockdep cannot be relied on
*
- * Returns true if lockdep must be ignored, in which case *ret contains
+ * Returns true if lockdep must be ignored, in which case ``*ret`` contains
* the best guess described below. Otherwise returns false, in which
- * case *ret tells the caller nothing and the caller should instead
+ * case ``*ret`` tells the caller nothing and the caller should instead
* consult lockdep.
*
- * If CONFIG_DEBUG_LOCK_ALLOC is selected, set *ret to nonzero iff in an
+ * If CONFIG_DEBUG_LOCK_ALLOC is selected, set ``*ret`` to nonzero iff in an
* RCU-sched read-side critical section. In absence of
* CONFIG_DEBUG_LOCK_ALLOC, this assumes we are in an RCU-sched read-side
* critical section unless it can prove otherwise. Note that disabling
@@ -81,8 +85,8 @@ module_param(rcu_normal_after_boot, int, 0);
* and while lockdep is disabled.
*
* Note that if the CPU is in the idle loop from an RCU point of view (ie:
- * that we are in the section between rcu_idle_enter() and rcu_idle_exit())
- * then rcu_read_lock_held() sets *ret to false even if the CPU did an
+ * that we are in the section between ct_idle_enter() and ct_idle_exit())
+ * then rcu_read_lock_held() sets ``*ret`` to false even if the CPU did an
* rcu_read_lock(). The reason for this is that RCU ignores CPUs that are
* in such a section, considering these as in extended quiescent state,
* so such a CPU is effectively never in an RCU read-side critical section
@@ -98,15 +102,15 @@ module_param(rcu_normal_after_boot, int, 0);
static bool rcu_read_lock_held_common(bool *ret)
{
if (!debug_lockdep_rcu_enabled()) {
- *ret = 1;
+ *ret = true;
return true;
}
if (!rcu_is_watching()) {
- *ret = 0;
+ *ret = false;
return true;
}
if (!rcu_lockdep_current_cpu_online()) {
- *ret = 0;
+ *ret = false;
return true;
}
return false;
@@ -183,6 +187,8 @@ void rcu_unexpedite_gp(void)
}
EXPORT_SYMBOL_GPL(rcu_unexpedite_gp);
+static bool rcu_boot_ended __read_mostly;
+
/*
* Inform RCU of the end of the in-kernel boot sequence.
*/
@@ -191,8 +197,18 @@ void rcu_end_inkernel_boot(void)
rcu_unexpedite_gp();
if (rcu_normal_after_boot)
WRITE_ONCE(rcu_normal, 1);
+ rcu_boot_ended = true;
}
+/*
+ * Let rcutorture know when it is OK to turn it up to eleven.
+ */
+bool rcu_inkernel_boot_has_ended(void)
+{
+ return rcu_boot_ended;
+}
+EXPORT_SYMBOL_GPL(rcu_inkernel_boot_has_ended);
+
#endif /* #ifndef CONFIG_TINY_RCU */
/*
@@ -227,32 +243,44 @@ core_initcall(rcu_set_runtime_mode);
#ifdef CONFIG_DEBUG_LOCK_ALLOC
static struct lock_class_key rcu_lock_key;
-struct lockdep_map rcu_lock_map =
- STATIC_LOCKDEP_MAP_INIT("rcu_read_lock", &rcu_lock_key);
+struct lockdep_map rcu_lock_map = {
+ .name = "rcu_read_lock",
+ .key = &rcu_lock_key,
+ .wait_type_outer = LD_WAIT_FREE,
+ .wait_type_inner = LD_WAIT_CONFIG, /* PREEMPT_RT implies PREEMPT_RCU */
+};
EXPORT_SYMBOL_GPL(rcu_lock_map);
static struct lock_class_key rcu_bh_lock_key;
-struct lockdep_map rcu_bh_lock_map =
- STATIC_LOCKDEP_MAP_INIT("rcu_read_lock_bh", &rcu_bh_lock_key);
+struct lockdep_map rcu_bh_lock_map = {
+ .name = "rcu_read_lock_bh",
+ .key = &rcu_bh_lock_key,
+ .wait_type_outer = LD_WAIT_FREE,
+ .wait_type_inner = LD_WAIT_CONFIG, /* PREEMPT_RT makes BH preemptible. */
+};
EXPORT_SYMBOL_GPL(rcu_bh_lock_map);
static struct lock_class_key rcu_sched_lock_key;
-struct lockdep_map rcu_sched_lock_map =
- STATIC_LOCKDEP_MAP_INIT("rcu_read_lock_sched", &rcu_sched_lock_key);
+struct lockdep_map rcu_sched_lock_map = {
+ .name = "rcu_read_lock_sched",
+ .key = &rcu_sched_lock_key,
+ .wait_type_outer = LD_WAIT_FREE,
+ .wait_type_inner = LD_WAIT_SPIN,
+};
EXPORT_SYMBOL_GPL(rcu_sched_lock_map);
+// Tell lockdep when RCU callbacks are being invoked.
static struct lock_class_key rcu_callback_key;
struct lockdep_map rcu_callback_map =
STATIC_LOCKDEP_MAP_INIT("rcu_callback", &rcu_callback_key);
EXPORT_SYMBOL_GPL(rcu_callback_map);
-int notrace debug_lockdep_rcu_enabled(void)
+noinstr int notrace debug_lockdep_rcu_enabled(void)
{
- return rcu_scheduler_active != RCU_SCHEDULER_INACTIVE && debug_locks &&
+ return rcu_scheduler_active != RCU_SCHEDULER_INACTIVE && READ_ONCE(debug_locks) &&
current->lockdep_recursion == 0;
}
EXPORT_SYMBOL_GPL(debug_lockdep_rcu_enabled);
-NOKPROBE_SYMBOL(debug_lockdep_rcu_enabled);
/**
* rcu_read_lock_held() - might we be in RCU read-side critical section?
@@ -353,13 +381,14 @@ void __wait_rcu_gp(bool checktiny, int n, call_rcu_func_t *crcu_array,
might_sleep();
continue;
}
- init_rcu_head_on_stack(&rs_array[i].head);
- init_completion(&rs_array[i].completion);
for (j = 0; j < i; j++)
if (crcu_array[j] == crcu_array[i])
break;
- if (j == i)
+ if (j == i) {
+ init_rcu_head_on_stack(&rs_array[i].head);
+ init_completion(&rs_array[i].completion);
(crcu_array[i])(&rs_array[i].head, wakeme_after_rcu);
+ }
}
/* Wait for all callbacks to be invoked. */
@@ -370,13 +399,21 @@ void __wait_rcu_gp(bool checktiny, int n, call_rcu_func_t *crcu_array,
for (j = 0; j < i; j++)
if (crcu_array[j] == crcu_array[i])
break;
- if (j == i)
+ if (j == i) {
wait_for_completion(&rs_array[i].completion);
- destroy_rcu_head_on_stack(&rs_array[i].head);
+ destroy_rcu_head_on_stack(&rs_array[i].head);
+ }
}
}
EXPORT_SYMBOL_GPL(__wait_rcu_gp);
+void finish_rcuwait(struct rcuwait *w)
+{
+ rcu_assign_pointer(w->task, NULL);
+ __set_current_state(TASK_RUNNING);
+}
+EXPORT_SYMBOL_GPL(finish_rcuwait);
+
#ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
void init_rcu_head(struct rcu_head *head)
{
@@ -428,7 +465,7 @@ void destroy_rcu_head_on_stack(struct rcu_head *head)
}
EXPORT_SYMBOL_GPL(destroy_rcu_head_on_stack);
-struct debug_obj_descr rcuhead_debug_descr = {
+const struct debug_obj_descr rcuhead_debug_descr = {
.name = "rcu_head",
.is_static_object = rcuhead_is_static_object,
};
@@ -464,376 +501,33 @@ EXPORT_SYMBOL_GPL(rcutorture_sched_setaffinity);
#ifdef CONFIG_RCU_STALL_COMMON
int rcu_cpu_stall_ftrace_dump __read_mostly;
module_param(rcu_cpu_stall_ftrace_dump, int, 0644);
-int rcu_cpu_stall_suppress __read_mostly; /* 1 = suppress stall warnings. */
+int rcu_cpu_stall_suppress __read_mostly; // !0 = suppress stall warnings.
EXPORT_SYMBOL_GPL(rcu_cpu_stall_suppress);
module_param(rcu_cpu_stall_suppress, int, 0644);
int rcu_cpu_stall_timeout __read_mostly = CONFIG_RCU_CPU_STALL_TIMEOUT;
module_param(rcu_cpu_stall_timeout, int, 0644);
+int rcu_exp_cpu_stall_timeout __read_mostly = CONFIG_RCU_EXP_CPU_STALL_TIMEOUT;
+module_param(rcu_exp_cpu_stall_timeout, int, 0644);
#endif /* #ifdef CONFIG_RCU_STALL_COMMON */
-#ifdef CONFIG_TASKS_RCU
-
-/*
- * Simple variant of RCU whose quiescent states are voluntary context
- * switch, cond_resched_rcu_qs(), user-space execution, and idle.
- * As such, grace periods can take one good long time. There are no
- * read-side primitives similar to rcu_read_lock() and rcu_read_unlock()
- * because this implementation is intended to get the system into a safe
- * state for some of the manipulations involved in tracing and the like.
- * Finally, this implementation does not support high call_rcu_tasks()
- * rates from multiple CPUs. If this is required, per-CPU callback lists
- * will be needed.
- */
-
-/* Global list of callbacks and associated lock. */
-static struct rcu_head *rcu_tasks_cbs_head;
-static struct rcu_head **rcu_tasks_cbs_tail = &rcu_tasks_cbs_head;
-static DECLARE_WAIT_QUEUE_HEAD(rcu_tasks_cbs_wq);
-static DEFINE_RAW_SPINLOCK(rcu_tasks_cbs_lock);
-
-/* Track exiting tasks in order to allow them to be waited for. */
-DEFINE_STATIC_SRCU(tasks_rcu_exit_srcu);
-
-/* Control stall timeouts. Disable with <= 0, otherwise jiffies till stall. */
-#define RCU_TASK_STALL_TIMEOUT (HZ * 60 * 10)
-static int rcu_task_stall_timeout __read_mostly = RCU_TASK_STALL_TIMEOUT;
-module_param(rcu_task_stall_timeout, int, 0644);
-
-static struct task_struct *rcu_tasks_kthread_ptr;
-
-/**
- * call_rcu_tasks() - Queue an RCU for invocation task-based grace period
- * @rhp: structure to be used for queueing the RCU updates.
- * @func: actual callback function to be invoked after the grace period
- *
- * The callback function will be invoked some time after a full grace
- * period elapses, in other words after all currently executing RCU
- * read-side critical sections have completed. call_rcu_tasks() assumes
- * that the read-side critical sections end at a voluntary context
- * switch (not a preemption!), cond_resched_rcu_qs(), entry into idle,
- * or transition to usermode execution. As such, there are no read-side
- * primitives analogous to rcu_read_lock() and rcu_read_unlock() because
- * this primitive is intended to determine that all tasks have passed
- * through a safe state, not so much for data-strcuture synchronization.
- *
- * See the description of call_rcu() for more detailed information on
- * memory ordering guarantees.
- */
-void call_rcu_tasks(struct rcu_head *rhp, rcu_callback_t func)
-{
- unsigned long flags;
- bool needwake;
-
- rhp->next = NULL;
- rhp->func = func;
- raw_spin_lock_irqsave(&rcu_tasks_cbs_lock, flags);
- needwake = !rcu_tasks_cbs_head;
- *rcu_tasks_cbs_tail = rhp;
- rcu_tasks_cbs_tail = &rhp->next;
- raw_spin_unlock_irqrestore(&rcu_tasks_cbs_lock, flags);
- /* We can't create the thread unless interrupts are enabled. */
- if (needwake && READ_ONCE(rcu_tasks_kthread_ptr))
- wake_up(&rcu_tasks_cbs_wq);
-}
-EXPORT_SYMBOL_GPL(call_rcu_tasks);
-
-/**
- * synchronize_rcu_tasks - wait until an rcu-tasks grace period has elapsed.
- *
- * Control will return to the caller some time after a full rcu-tasks
- * grace period has elapsed, in other words after all currently
- * executing rcu-tasks read-side critical sections have elapsed. These
- * read-side critical sections are delimited by calls to schedule(),
- * cond_resched_tasks_rcu_qs(), idle execution, userspace execution, calls
- * to synchronize_rcu_tasks(), and (in theory, anyway) cond_resched().
- *
- * This is a very specialized primitive, intended only for a few uses in
- * tracing and other situations requiring manipulation of function
- * preambles and profiling hooks. The synchronize_rcu_tasks() function
- * is not (yet) intended for heavy use from multiple CPUs.
- *
- * Note that this guarantee implies further memory-ordering guarantees.
- * On systems with more than one CPU, when synchronize_rcu_tasks() returns,
- * each CPU is guaranteed to have executed a full memory barrier since the
- * end of its last RCU-tasks read-side critical section whose beginning
- * preceded the call to synchronize_rcu_tasks(). In addition, each CPU
- * having an RCU-tasks read-side critical section that extends beyond
- * the return from synchronize_rcu_tasks() is guaranteed to have executed
- * a full memory barrier after the beginning of synchronize_rcu_tasks()
- * and before the beginning of that RCU-tasks read-side critical section.
- * Note that these guarantees include CPUs that are offline, idle, or
- * executing in user mode, as well as CPUs that are executing in the kernel.
- *
- * Furthermore, if CPU A invoked synchronize_rcu_tasks(), which returned
- * to its caller on CPU B, then both CPU A and CPU B are guaranteed
- * to have executed a full memory barrier during the execution of
- * synchronize_rcu_tasks() -- even if CPU A and CPU B are the same CPU
- * (but again only if the system has more than one CPU).
- */
-void synchronize_rcu_tasks(void)
-{
- /* Complain if the scheduler has not started. */
- RCU_LOCKDEP_WARN(rcu_scheduler_active == RCU_SCHEDULER_INACTIVE,
- "synchronize_rcu_tasks called too soon");
-
- /* Wait for the grace period. */
- wait_rcu_gp(call_rcu_tasks);
-}
-EXPORT_SYMBOL_GPL(synchronize_rcu_tasks);
+// Suppress boot-time RCU CPU stall warnings and rcutorture writer stall
+// warnings. Also used by rcutorture even if stall warnings are excluded.
+int rcu_cpu_stall_suppress_at_boot __read_mostly; // !0 = suppress boot stalls.
+EXPORT_SYMBOL_GPL(rcu_cpu_stall_suppress_at_boot);
+module_param(rcu_cpu_stall_suppress_at_boot, int, 0444);
/**
- * rcu_barrier_tasks - Wait for in-flight call_rcu_tasks() callbacks.
+ * get_completed_synchronize_rcu - Return a pre-completed polled state cookie
*
- * Although the current implementation is guaranteed to wait, it is not
- * obligated to, for example, if there are no pending callbacks.
- */
-void rcu_barrier_tasks(void)
-{
- /* There is only one callback queue, so this is easy. ;-) */
- synchronize_rcu_tasks();
-}
-EXPORT_SYMBOL_GPL(rcu_barrier_tasks);
-
-/* See if tasks are still holding out, complain if so. */
-static void check_holdout_task(struct task_struct *t,
- bool needreport, bool *firstreport)
-{
- int cpu;
-
- if (!READ_ONCE(t->rcu_tasks_holdout) ||
- t->rcu_tasks_nvcsw != READ_ONCE(t->nvcsw) ||
- !READ_ONCE(t->on_rq) ||
- (IS_ENABLED(CONFIG_NO_HZ_FULL) &&
- !is_idle_task(t) && t->rcu_tasks_idle_cpu >= 0)) {
- WRITE_ONCE(t->rcu_tasks_holdout, false);
- list_del_init(&t->rcu_tasks_holdout_list);
- put_task_struct(t);
- return;
- }
- rcu_request_urgent_qs_task(t);
- if (!needreport)
- return;
- if (*firstreport) {
- pr_err("INFO: rcu_tasks detected stalls on tasks:\n");
- *firstreport = false;
- }
- cpu = task_cpu(t);
- pr_alert("%p: %c%c nvcsw: %lu/%lu holdout: %d idle_cpu: %d/%d\n",
- t, ".I"[is_idle_task(t)],
- "N."[cpu < 0 || !tick_nohz_full_cpu(cpu)],
- t->rcu_tasks_nvcsw, t->nvcsw, t->rcu_tasks_holdout,
- t->rcu_tasks_idle_cpu, cpu);
- sched_show_task(t);
-}
-
-/* RCU-tasks kthread that detects grace periods and invokes callbacks. */
-static int __noreturn rcu_tasks_kthread(void *arg)
-{
- unsigned long flags;
- struct task_struct *g, *t;
- unsigned long lastreport;
- struct rcu_head *list;
- struct rcu_head *next;
- LIST_HEAD(rcu_tasks_holdouts);
- int fract;
-
- /* Run on housekeeping CPUs by default. Sysadm can move if desired. */
- housekeeping_affine(current, HK_FLAG_RCU);
-
- /*
- * Each pass through the following loop makes one check for
- * newly arrived callbacks, and, if there are some, waits for
- * one RCU-tasks grace period and then invokes the callbacks.
- * This loop is terminated by the system going down. ;-)
- */
- for (;;) {
-
- /* Pick up any new callbacks. */
- raw_spin_lock_irqsave(&rcu_tasks_cbs_lock, flags);
- list = rcu_tasks_cbs_head;
- rcu_tasks_cbs_head = NULL;
- rcu_tasks_cbs_tail = &rcu_tasks_cbs_head;
- raw_spin_unlock_irqrestore(&rcu_tasks_cbs_lock, flags);
-
- /* If there were none, wait a bit and start over. */
- if (!list) {
- wait_event_interruptible(rcu_tasks_cbs_wq,
- rcu_tasks_cbs_head);
- if (!rcu_tasks_cbs_head) {
- WARN_ON(signal_pending(current));
- schedule_timeout_interruptible(HZ/10);
- }
- continue;
- }
-
- /*
- * Wait for all pre-existing t->on_rq and t->nvcsw
- * transitions to complete. Invoking synchronize_rcu()
- * suffices because all these transitions occur with
- * interrupts disabled. Without this synchronize_rcu(),
- * a read-side critical section that started before the
- * grace period might be incorrectly seen as having started
- * after the grace period.
- *
- * This synchronize_rcu() also dispenses with the
- * need for a memory barrier on the first store to
- * ->rcu_tasks_holdout, as it forces the store to happen
- * after the beginning of the grace period.
- */
- synchronize_rcu();
-
- /*
- * There were callbacks, so we need to wait for an
- * RCU-tasks grace period. Start off by scanning
- * the task list for tasks that are not already
- * voluntarily blocked. Mark these tasks and make
- * a list of them in rcu_tasks_holdouts.
- */
- rcu_read_lock();
- for_each_process_thread(g, t) {
- if (t != current && READ_ONCE(t->on_rq) &&
- !is_idle_task(t)) {
- get_task_struct(t);
- t->rcu_tasks_nvcsw = READ_ONCE(t->nvcsw);
- WRITE_ONCE(t->rcu_tasks_holdout, true);
- list_add(&t->rcu_tasks_holdout_list,
- &rcu_tasks_holdouts);
- }
- }
- rcu_read_unlock();
-
- /*
- * Wait for tasks that are in the process of exiting.
- * This does only part of the job, ensuring that all
- * tasks that were previously exiting reach the point
- * where they have disabled preemption, allowing the
- * later synchronize_rcu() to finish the job.
- */
- synchronize_srcu(&tasks_rcu_exit_srcu);
-
- /*
- * Each pass through the following loop scans the list
- * of holdout tasks, removing any that are no longer
- * holdouts. When the list is empty, we are done.
- */
- lastreport = jiffies;
-
- /* Start off with HZ/10 wait and slowly back off to 1 HZ wait*/
- fract = 10;
-
- for (;;) {
- bool firstreport;
- bool needreport;
- int rtst;
- struct task_struct *t1;
-
- if (list_empty(&rcu_tasks_holdouts))
- break;
-
- /* Slowly back off waiting for holdouts */
- schedule_timeout_interruptible(HZ/fract);
-
- if (fract > 1)
- fract--;
-
- rtst = READ_ONCE(rcu_task_stall_timeout);
- needreport = rtst > 0 &&
- time_after(jiffies, lastreport + rtst);
- if (needreport)
- lastreport = jiffies;
- firstreport = true;
- WARN_ON(signal_pending(current));
- list_for_each_entry_safe(t, t1, &rcu_tasks_holdouts,
- rcu_tasks_holdout_list) {
- check_holdout_task(t, needreport, &firstreport);
- cond_resched();
- }
- }
-
- /*
- * Because ->on_rq and ->nvcsw are not guaranteed
- * to have a full memory barriers prior to them in the
- * schedule() path, memory reordering on other CPUs could
- * cause their RCU-tasks read-side critical sections to
- * extend past the end of the grace period. However,
- * because these ->nvcsw updates are carried out with
- * interrupts disabled, we can use synchronize_rcu()
- * to force the needed ordering on all such CPUs.
- *
- * This synchronize_rcu() also confines all
- * ->rcu_tasks_holdout accesses to be within the grace
- * period, avoiding the need for memory barriers for
- * ->rcu_tasks_holdout accesses.
- *
- * In addition, this synchronize_rcu() waits for exiting
- * tasks to complete their final preempt_disable() region
- * of execution, cleaning up after the synchronize_srcu()
- * above.
- */
- synchronize_rcu();
-
- /* Invoke the callbacks. */
- while (list) {
- next = list->next;
- local_bh_disable();
- list->func(list);
- local_bh_enable();
- list = next;
- cond_resched();
- }
- /* Paranoid sleep to keep this from entering a tight loop */
- schedule_timeout_uninterruptible(HZ/10);
- }
-}
-
-/* Spawn rcu_tasks_kthread() at core_initcall() time. */
-static int __init rcu_spawn_tasks_kthread(void)
-{
- struct task_struct *t;
-
- t = kthread_run(rcu_tasks_kthread, NULL, "rcu_tasks_kthread");
- if (WARN_ONCE(IS_ERR(t), "%s: Could not start Tasks-RCU grace-period kthread, OOM is now expected behavior\n", __func__))
- return 0;
- smp_mb(); /* Ensure others see full kthread. */
- WRITE_ONCE(rcu_tasks_kthread_ptr, t);
- return 0;
-}
-core_initcall(rcu_spawn_tasks_kthread);
-
-/* Do the srcu_read_lock() for the above synchronize_srcu(). */
-void exit_tasks_rcu_start(void)
-{
- preempt_disable();
- current->rcu_tasks_idx = __srcu_read_lock(&tasks_rcu_exit_srcu);
- preempt_enable();
-}
-
-/* Do the srcu_read_unlock() for the above synchronize_srcu(). */
-void exit_tasks_rcu_finish(void)
-{
- preempt_disable();
- __srcu_read_unlock(&tasks_rcu_exit_srcu, current->rcu_tasks_idx);
- preempt_enable();
-}
-
-#endif /* #ifdef CONFIG_TASKS_RCU */
-
-#ifndef CONFIG_TINY_RCU
-
-/*
- * Print any non-default Tasks RCU settings.
+ * Returns a value that will always be treated by functions like
+ * poll_state_synchronize_rcu() as a cookie whose grace period has already
+ * completed.
*/
-static void __init rcu_tasks_bootup_oddness(void)
+unsigned long get_completed_synchronize_rcu(void)
{
-#ifdef CONFIG_TASKS_RCU
- if (rcu_task_stall_timeout != RCU_TASK_STALL_TIMEOUT)
- pr_info("\tTasks-RCU CPU stall warnings timeout set to %d (rcu_task_stall_timeout).\n", rcu_task_stall_timeout);
- else
- pr_info("\tTasks RCU enabled.\n");
-#endif /* #ifdef CONFIG_TASKS_RCU */
+ return RCU_GET_STATE_COMPLETED;
}
-
-#endif /* #ifndef CONFIG_TINY_RCU */
+EXPORT_SYMBOL_GPL(get_completed_synchronize_rcu);
#ifdef CONFIG_PROVE_RCU
@@ -852,6 +546,7 @@ static void test_callback(struct rcu_head *r)
}
DEFINE_STATIC_SRCU(early_srcu);
+static unsigned long early_srcu_cookie;
struct early_boot_kfree_rcu {
struct rcu_head rh;
@@ -864,8 +559,10 @@ static void early_boot_test_call_rcu(void)
struct early_boot_kfree_rcu *rhp;
call_rcu(&head, test_callback);
- if (IS_ENABLED(CONFIG_SRCU))
+ if (IS_ENABLED(CONFIG_SRCU)) {
+ early_srcu_cookie = start_poll_synchronize_srcu(&early_srcu);
call_srcu(&early_srcu, &shead, test_callback);
+ }
rhp = kmalloc(sizeof(*rhp), GFP_KERNEL);
if (!WARN_ON_ONCE(!rhp))
kfree_rcu(rhp, rh);
@@ -891,6 +588,7 @@ static int rcu_verify_early_boot_tests(void)
if (IS_ENABLED(CONFIG_SRCU)) {
early_boot_test_counter++;
srcu_barrier(&early_srcu);
+ WARN_ON_ONCE(!poll_state_synchronize_srcu(&early_srcu, early_srcu_cookie));
}
}
if (rcu_self_test_counter != early_boot_test_counter) {
@@ -905,6 +603,8 @@ late_initcall(rcu_verify_early_boot_tests);
void rcu_early_boot_tests(void) {}
#endif /* CONFIG_PROVE_RCU */
+#include "tasks.h"
+
#ifndef CONFIG_TINY_RCU
/*
Copyright © 1996 – 2023 Jason A. Donenfeld. All Rights Reverse Engineered.