diff options
Diffstat (limited to 'kernel/rcu')
| -rw-r--r-- | kernel/rcu/Kconfig | 242 | ||||
| -rw-r--r-- | kernel/rcu/Kconfig.debug | 82 | ||||
| -rw-r--r-- | kernel/rcu/Makefile | 2 | ||||
| -rw-r--r-- | kernel/rcu/rcu.h | 277 | ||||
| -rw-r--r-- | kernel/rcu/rcuperf.c | 129 | ||||
| -rw-r--r-- | kernel/rcu/rcutorture.c | 21 | ||||
| -rw-r--r-- | kernel/rcu/srcu.c | 661 | ||||
| -rw-r--r-- | kernel/rcu/srcutiny.c | 86 | ||||
| -rw-r--r-- | kernel/rcu/srcutree.c | 187 | ||||
| -rw-r--r-- | kernel/rcu/tiny.c | 54 | ||||
| -rw-r--r-- | kernel/rcu/tiny_plugin.h | 123 | ||||
| -rw-r--r-- | kernel/rcu/tree.c | 195 | ||||
| -rw-r--r-- | kernel/rcu/tree.h | 109 | ||||
| -rw-r--r-- | kernel/rcu/tree_exp.h | 2 | ||||
| -rw-r--r-- | kernel/rcu/tree_plugin.h | 573 | ||||
| -rw-r--r-- | kernel/rcu/tree_trace.c | 494 | ||||
| -rw-r--r-- | kernel/rcu/update.c | 77 |
17 files changed, 1161 insertions, 2153 deletions
diff --git a/kernel/rcu/Kconfig b/kernel/rcu/Kconfig new file mode 100644 index 000000000000..be90c945063f --- /dev/null +++ b/kernel/rcu/Kconfig @@ -0,0 +1,242 @@ +# +# RCU-related configuration options +# + +menu "RCU Subsystem" + +config TREE_RCU + bool + default y if !PREEMPT && SMP + help + This option selects the RCU implementation that is + designed for very large SMP system with hundreds or + thousands of CPUs. It also scales down nicely to + smaller systems. + +config PREEMPT_RCU + bool + default y if PREEMPT + help + This option selects the RCU implementation that is + designed for very large SMP systems with hundreds or + thousands of CPUs, but for which real-time response + is also required. It also scales down nicely to + smaller systems. + + Select this option if you are unsure. + +config TINY_RCU + bool + default y if !PREEMPT && !SMP + help + This option selects the RCU implementation that is + designed for UP systems from which real-time response + is not required. This option greatly reduces the + memory footprint of RCU. + +config RCU_EXPERT + bool "Make expert-level adjustments to RCU configuration" + default n + help + This option needs to be enabled if you wish to make + expert-level adjustments to RCU configuration. By default, + no such adjustments can be made, which has the often-beneficial + side-effect of preventing "make oldconfig" from asking you all + sorts of detailed questions about how you would like numerous + obscure RCU options to be set up. + + Say Y if you need to make expert-level adjustments to RCU. + + Say N if you are unsure. + +config SRCU + bool + help + This option selects the sleepable version of RCU. This version + permits arbitrary sleeping or blocking within RCU read-side critical + sections. + +config TINY_SRCU + bool + default y if SRCU && TINY_RCU + help + This option selects the single-CPU non-preemptible version of SRCU. + +config TREE_SRCU + bool + default y if SRCU && !TINY_RCU + help + This option selects the full-fledged version of SRCU. + +config TASKS_RCU + bool + default n + select SRCU + 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. + +config RCU_STALL_COMMON + def_bool ( TREE_RCU || PREEMPT_RCU ) + help + This option enables RCU CPU stall code that is common between + the TINY and TREE variants of RCU. The purpose is to allow + the tiny variants to disable RCU CPU stall warnings, while + making these warnings mandatory for the tree variants. + +config RCU_NEED_SEGCBLIST + def_bool ( TREE_RCU || PREEMPT_RCU || TREE_SRCU ) + +config CONTEXT_TRACKING + bool + +config CONTEXT_TRACKING_FORCE + bool "Force context tracking" + depends on CONTEXT_TRACKING + default y if !NO_HZ_FULL + help + The major pre-requirement for full dynticks to work is to + support the context tracking subsystem. But there are also + other dependencies to provide in order to make the full + dynticks working. + + This option stands for testing when an arch implements the + context tracking backend but doesn't yet fullfill all the + requirements to make the full dynticks feature working. + Without the full dynticks, there is no way to test the support + for context tracking and the subsystems that rely on it: RCU + userspace extended quiescent state and tickless cputime + accounting. This option copes with the absence of the full + dynticks subsystem by forcing the context tracking on all + CPUs in the system. + + Say Y only if you're working on the development of an + architecture backend for the context tracking. + + Say N otherwise, this option brings an overhead that you + don't want in production. + + +config RCU_FANOUT + int "Tree-based hierarchical RCU fanout value" + range 2 64 if 64BIT + range 2 32 if !64BIT + depends on (TREE_RCU || PREEMPT_RCU) && RCU_EXPERT + default 64 if 64BIT + default 32 if !64BIT + help + This option controls the fanout of hierarchical implementations + of RCU, allowing RCU to work efficiently on machines with + large numbers of CPUs. This value must be at least the fourth + root of NR_CPUS, which allows NR_CPUS to be insanely large. + The default value of RCU_FANOUT should be used for production + systems, but if you are stress-testing the RCU implementation + itself, small RCU_FANOUT values allow you to test large-system + code paths on small(er) systems. + + Select a specific number if testing RCU itself. + Take the default if unsure. + +config RCU_FANOUT_LEAF + int "Tree-based hierarchical RCU leaf-level fanout value" + range 2 64 if 64BIT + range 2 32 if !64BIT + depends on (TREE_RCU || PREEMPT_RCU) && RCU_EXPERT + default 16 + help + This option controls the leaf-level fanout of hierarchical + implementations of RCU, and allows trading off cache misses + against lock contention. Systems that synchronize their + scheduling-clock interrupts for energy-efficiency reasons will + want the default because the smaller leaf-level fanout keeps + lock contention levels acceptably low. Very large systems + (hundreds or thousands of CPUs) will instead want to set this + value to the maximum value possible in order to reduce the + number of cache misses incurred during RCU's grace-period + initialization. These systems tend to run CPU-bound, and thus + are not helped by synchronized interrupts, and thus tend to + skew them, which reduces lock contention enough that large + leaf-level fanouts work well. That said, setting leaf-level + fanout to a large number will likely cause problematic + lock contention on the leaf-level rcu_node structures unless + you boot with the skew_tick kernel parameter. + + Select a specific number if testing RCU itself. + + Select the maximum permissible value for large systems, but + please understand that you may also need to set the skew_tick + kernel boot parameter to avoid contention on the rcu_node + structure's locks. + + 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 + help + This option boosts the priority of preempted RCU readers that + block the current preemptible RCU grace period for too long. + This option also prevents heavy loads from blocking RCU + callback invocation for all flavors of RCU. + + Say Y here if you are working with real-time apps or heavy loads + Say N here if you are unsure. + +config RCU_BOOST_DELAY + int "Milliseconds to delay boosting after RCU grace-period start" + range 0 3000 + depends on RCU_BOOST + default 500 + help + This option specifies the time to wait after the beginning of + a given grace period before priority-boosting preempted RCU + readers blocking that grace period. Note that any RCU reader + blocking an expedited RCU grace period is boosted immediately. + + Accept the default if unsure. + +config RCU_NOCB_CPU + bool "Offload RCU callback processing from boot-selected CPUs" + depends on TREE_RCU || PREEMPT_RCU + depends on RCU_EXPERT || NO_HZ_FULL + default n + help + 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. + + 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 "x" is "b" for RCU-bh, "p" for RCU-preempt, and + "s" for RCU-sched. 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 N here if you are unsure. + +endmenu # "RCU Subsystem" diff --git a/kernel/rcu/Kconfig.debug b/kernel/rcu/Kconfig.debug new file mode 100644 index 000000000000..0ec7d1d33a14 --- /dev/null +++ b/kernel/rcu/Kconfig.debug @@ -0,0 +1,82 @@ +# +# RCU-related debugging configuration options +# + +menu "RCU Debugging" + +config PROVE_RCU + def_bool PROVE_LOCKING + +config TORTURE_TEST + tristate + default n + +config RCU_PERF_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 + tests on the RCU infrastructure. The kernel module may be built + after the fact on the running kernel to be tested, if desired. + + Say Y here if you want RCU performance tests to be built into + the kernel. + Say M if you want the RCU performance tests to build as a module. + Say N if you are unsure. + +config RCU_TORTURE_TEST + tristate "torture 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 torture tests + on the RCU infrastructure. The kernel module may be built + after the fact on the running kernel to be tested, if desired. + + Say Y here if you want RCU torture tests to be built into + the kernel. + Say M if you want the RCU torture tests to build as a module. + Say N if you are unsure. + +config RCU_CPU_STALL_TIMEOUT + int "RCU CPU stall timeout in seconds" + depends on RCU_STALL_COMMON + range 3 300 + default 21 + help + If a given RCU grace period extends more than the specified + number of seconds, a CPU stall warning is printed. If the + RCU grace period persists, additional CPU stall warnings are + printed at more widely spaced intervals. + +config RCU_TRACE + bool "Enable tracing for RCU" + depends on DEBUG_KERNEL + default y if TREE_RCU + select TRACE_CLOCK + help + This option enables additional tracepoints for ftrace-style + event tracing. + + Say Y here if you want to enable RCU tracing + Say N if you are unsure. + +config RCU_EQS_DEBUG + bool "Provide debugging asserts for adding NO_HZ support to an arch" + depends on DEBUG_KERNEL + help + This option provides consistency checks in RCU's handling of + NO_HZ. These checks have proven quite helpful in detecting + bugs in arch-specific NO_HZ code. + + Say N here if you need ultimate kernel/user switch latencies + Say Y if you are unsure + +endmenu # "RCU Debugging" diff --git a/kernel/rcu/Makefile b/kernel/rcu/Makefile index 23803c7d5180..13c0fc852767 100644 --- a/kernel/rcu/Makefile +++ b/kernel/rcu/Makefile @@ -3,13 +3,11 @@ KCOV_INSTRUMENT := n obj-y += update.o sync.o -obj-$(CONFIG_CLASSIC_SRCU) += srcu.o obj-$(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_TREE_RCU) += tree.o obj-$(CONFIG_PREEMPT_RCU) += tree.o -obj-$(CONFIG_TREE_RCU_TRACE) += tree_trace.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 73e16ec4054b..808b8c85f626 100644 --- a/kernel/rcu/rcu.h +++ b/kernel/rcu/rcu.h @@ -212,6 +212,18 @@ int rcu_jiffies_till_stall_check(void); */ #define TPS(x) tracepoint_string(x) +/* + * Dump the ftrace buffer, but only one time per callsite per boot. + */ +#define rcu_ftrace_dump(oops_dump_mode) \ +do { \ + static atomic_t ___rfd_beenhere = ATOMIC_INIT(0); \ + \ + if (!atomic_read(&___rfd_beenhere) && \ + !atomic_xchg(&___rfd_beenhere, 1)) \ + ftrace_dump(oops_dump_mode); \ +} while (0) + void rcu_early_boot_tests(void); void rcu_test_sync_prims(void); @@ -291,6 +303,271 @@ static inline void rcu_init_levelspread(int *levelspread, const int *levelcnt) cpu <= rnp->grphi; \ cpu = cpumask_next((cpu), cpu_possible_mask)) +/* + * Wrappers for the rcu_node::lock acquire and release. + * + * Because the rcu_nodes form a tree, the tree traversal locking will observe + * different lock values, this in turn means that an UNLOCK of one level + * followed by a LOCK of another level does not imply a full memory barrier; + * and most importantly transitivity is lost. + * + * In order to restore full ordering between tree levels, augment the regular + * lock acquire functions with smp_mb__after_unlock_lock(). + * + * As ->lock of struct rcu_node is a __private field, therefore one should use + * these wrappers rather than directly call raw_spin_{lock,unlock}* on ->lock. + */ +#define raw_spin_lock_rcu_node(p) \ +do { \ + raw_spin_lock(&ACCESS_PRIVATE(p, lock)); \ + smp_mb__after_unlock_lock(); \ +} while (0) + +#define raw_spin_unlock_rcu_node(p) raw_spin_unlock(&ACCESS_PRIVATE(p, lock)) + +#define raw_spin_lock_irq_rcu_node(p) \ +do { \ + raw_spin_lock_irq(&ACCESS_PRIVATE(p, lock)); \ + smp_mb__after_unlock_lock(); \ +} while (0) + +#define raw_spin_unlock_irq_rcu_node(p) \ + raw_spin_unlock_irq(&ACCESS_PRIVATE(p, lock)) + +#define raw_spin_lock_irqsave_rcu_node(p, flags) \ +do { \ + raw_spin_lock_irqsave(&ACCESS_PRIVATE(p, lock), flags); \ + smp_mb__after_unlock_lock(); \ +} while (0) + +#define raw_spin_unlock_irqrestore_rcu_node(p, flags) \ + raw_spin_unlock_irqrestore(&ACCESS_PRIVATE(p, lock), flags) \ + +#define raw_spin_trylock_rcu_node(p) \ +({ \ + bool ___locked = raw_spin_trylock(&ACCESS_PRIVATE(p, lock)); \ + \ + if (___locked) \ + smp_mb__after_unlock_lock(); \ + ___locked; \ +}) + #endif /* #if defined(SRCU) || !defined(TINY_RCU) */ +#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) /* Internal RCU use. */ +{ + return true; +} +static inline bool rcu_gp_is_expedited(void) /* Internal RCU use. */ +{ + return false; +} + +static inline void rcu_expedite_gp(void) +{ +} + +static inline void rcu_unexpedite_gp(void) +{ +} +#else /* #ifdef CONFIG_TINY_RCU */ +bool rcu_gp_is_normal(void); /* Internal RCU use. */ +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); +#endif /* #else #ifdef CONFIG_TINY_RCU */ + +#define RCU_SCHEDULER_INACTIVE 0 +#define RCU_SCHEDULER_INIT 1 +#define RCU_SCHEDULER_RUNNING 2 + +#ifdef CONFIG_TINY_RCU +static inline void rcu_request_urgent_qs_task(struct task_struct *t) { } +#else /* #ifdef CONFIG_TINY_RCU */ +void rcu_request_urgent_qs_task(struct task_struct *t); +#endif /* #else #ifdef CONFIG_TINY_RCU */ + +enum rcutorture_type { + RCU_FLAVOR, + RCU_BH_FLAVOR, + RCU_SCHED_FLAVOR, + RCU_TASKS_FLAVOR, + SRCU_FLAVOR, + INVALID_RCU_FLAVOR +}; + +#if defined(CONFIG_TREE_RCU) || defined(CONFIG_PREEMPT_RCU) +void rcutorture_get_gp_data(enum rcutorture_type test_type, int *flags, + unsigned long *gpnum, unsigned long *completed); +void rcutorture_record_test_transition(void); +void rcutorture_record_progress(unsigned long vernum); +void do_trace_rcu_torture_read(const char *rcutorturename, + struct rcu_head *rhp, + unsigned long secs, + unsigned long c_old, + unsigned long c); +#else +static inline void rcutorture_get_gp_data(enum rcutorture_type test_type, + int *flags, + unsigned long *gpnum, + unsigned long *completed) +{ + *flags = 0; + *gpnum = 0; + *completed = 0; +} +static inline void rcutorture_record_test_transition(void) +{ +} +static inline void rcutorture_record_progress(unsigned long vernum) +{ +} +#ifdef CONFIG_RCU_TRACE +void do_trace_rcu_torture_read(const char *rcutorturename, + struct rcu_head *rhp, + unsigned long secs, + unsigned long c_old, + unsigned long c); +#else +#define do_trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c) \ + do { } while (0) +#endif +#endif + +#ifdef CONFIG_TINY_SRCU + +static inline void srcutorture_get_gp_data(enum rcutorture_type test_type, + struct srcu_struct *sp, int *flags, + unsigned long *gpnum, + unsigned long *completed) +{ + if (test_type != SRCU_FLAVOR) + return; + *flags = 0; + *completed = sp->srcu_idx; + *gpnum = *completed; +} + +#elif defined(CONFIG_TREE_SRCU) + +void srcutorture_get_gp_data(enum rcutorture_type test_type, + struct srcu_struct *sp, int *flags, + unsigned long *gpnum, unsigned long *completed); + +#endif + +#ifdef CONFIG_TINY_RCU + +/* + * Return the number of grace periods started. + */ +static inline unsigned long rcu_batches_started(void) +{ + return 0; +} + +/* + * Return the number of bottom-half grace periods started. + */ +static inline unsigned long rcu_batches_started_bh(void) +{ + return 0; +} + +/* + * Return the number of sched grace periods started. + */ +static inline unsigned long rcu_batches_started_sched(void) +{ + return 0; +} + +/* + * Return the number of grace periods completed. + */ +static inline unsigned long rcu_batches_completed(void) +{ + return 0; +} + +/* + * Return the number of bottom-half grace periods completed. + */ +static inline unsigned long rcu_batches_completed_bh(void) +{ + return 0; +} + +/* + * Return the number of sched grace periods completed. + */ +static inline unsigned long rcu_batches_completed_sched(void) +{ + return 0; +} + +/* + * Return the number of expedited grace periods completed. + */ +static inline unsigned long rcu_exp_batches_completed(void) +{ + return 0; +} + +/* + * Return the number of expedited sched grace periods completed. + */ +static inline unsigned long rcu_exp_batches_completed_sched(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 void rcu_bh_force_quiescent_state(void) +{ +} + +static inline void rcu_sched_force_quiescent_state(void) +{ +} + +static inline void show_rcu_gp_kthreads(void) +{ +} + +#else /* #ifdef CONFIG_TINY_RCU */ +extern unsigned long rcutorture_testseq; +extern unsigned long rcutorture_vernum; +unsigned long rcu_batches_started(void); +unsigned long rcu_batches_started_bh(void); +unsigned long rcu_batches_started_sched(void); +unsigned long rcu_batches_completed(void); +unsigned long rcu_batches_completed_bh(void); +unsigned long rcu_batches_completed_sched(void); +unsigned long rcu_exp_batches_completed(void); +unsigned long rcu_exp_batches_completed_sched(void); +unsigned long srcu_batches_completed(struct srcu_struct *sp); +void show_rcu_gp_kthreads(void); +void rcu_force_quiescent_state(void); +void rcu_bh_force_quiescent_state(void); +void rcu_sched_force_quiescent_state(void); +#endif /* #else #ifdef CONFIG_TINY_RCU */ + +#ifdef CONFIG_RCU_NOCB_CPU +bool rcu_is_nocb_cpu(int cpu); +#else +static inline bool rcu_is_nocb_cpu(int cpu) { return false; } +#endif + #endif /* __LINUX_RCU_H */ diff --git a/kernel/rcu/rcuperf.c b/kernel/rcu/rcuperf.c index a4a86fb47e4a..3cc18110b612 100644 --- a/kernel/rcu/rcuperf.c +++ b/kernel/rcu/rcuperf.c @@ -48,6 +48,8 @@ #include <linux/torture.h> #include <linux/vmalloc.h> +#include "rcu.h" + MODULE_LICENSE("GPL"); MODULE_AUTHOR("Paul E. McKenney <paulmck@linux.vnet.ibm.com>"); @@ -59,12 +61,16 @@ MODULE_AUTHOR("Paul E. McKenney <paulmck@linux.vnet.ibm.com>"); #define VERBOSE_PERFOUT_ERRSTRING(s) \ do { if (verbose) pr_alert("%s" PERF_FLAG "!!! %s\n", perf_type, s); } while (0) +torture_param(bool, gp_async, false, "Use asynchronous GP wait primitives"); +torture_param(int, gp_async_max, 1000, "Max # outstanding waits per reader"); 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, nreaders, 0, "Number of RCU reader threads"); torture_param(int, nwriters, -1, "Number of RCU updater threads"); -torture_param(bool, shutdown, false, "Shutdown at end of performance tests."); +torture_param(bool, shutdown, !IS_ENABLED(MODULE), + "Shutdown at end of performance tests."); torture_param(bool, verbose, true, "Enable verbose debugging printk()s"); +torture_param(int, writer_holdoff, 0, "Holdoff (us) between GPs, zero to disable"); static char *perf_type = "rcu"; module_param(perf_type, charp, 0444); @@ -86,13 +92,16 @@ static u64 t_rcu_perf_writer_started; static u64 t_rcu_perf_writer_finished; static unsigned long b_rcu_perf_writer_started; static unsigned long b_rcu_perf_writer_finished; +static DEFINE_PER_CPU(atomic_t, n_async_inflight); static int rcu_perf_writer_state; #define RTWS_INIT 0 -#define RTWS_EXP_SYNC 1 -#define RTWS_SYNC 2 -#define RTWS_IDLE 2 -#define RTWS_STOPPING 3 +#define RTWS_ASYNC 1 +#define RTWS_BARRIER 2 +#define RTWS_EXP_SYNC 3 +#define RTWS_SYNC 4 +#define RTWS_IDLE 5 +#define RTWS_STOPPING 6 #define MAX_MEAS 10000 #define MIN_MEAS 100 @@ -114,6 +123,8 @@ struct rcu_perf_ops { unsigned long (*started)(void); unsigned long (*completed)(void); unsigned long (*exp_completed)(void); + void (*async)(struct rcu_head *head, rcu_callback_t func); + void (*gp_barrier)(void); void (*sync)(void); void (*exp_sync)(void); const char *name; @@ -153,6 +164,8 @@ static struct rcu_perf_ops rcu_ops = { .started = rcu_batches_started, .completed = rcu_batches_completed, .exp_completed = rcu_exp_batches_completed, + .async = call_rcu, + .gp_barrier = rcu_barrier, .sync = synchronize_rcu, .exp_sync = synchronize_rcu_expedited, .name = "rcu" @@ -181,6 +194,8 @@ static struct rcu_perf_ops rcu_bh_ops = { .started = rcu_batches_started_bh, .completed = rcu_batches_completed_bh, .exp_completed = rcu_exp_batches_completed_sched, + .async = call_rcu_bh, + .gp_barrier = rcu_barrier_bh, .sync = synchronize_rcu_bh, .exp_sync = synchronize_rcu_bh_expedited, .name = "rcu_bh" @@ -208,6 +223,16 @@ static unsigned long srcu_perf_completed(void) return srcu_batches_completed(srcu_ctlp); } +static void srcu_call_rcu(struct rcu_head *head, rcu_callback_t func) +{ + call_srcu(srcu_ctlp, head, func); +} + +static void srcu_rcu_barrier(void) +{ + srcu_barrier(srcu_ctlp); +} + static void srcu_perf_synchronize(void) { synchronize_srcu(srcu_ctlp); @@ -226,11 +251,42 @@ static struct rcu_perf_ops srcu_ops = { .started = NULL, .completed = srcu_perf_completed, .exp_completed = srcu_perf_completed, + .async = srcu_call_rcu, + .gp_barrier = srcu_rcu_barrier, .sync = srcu_perf_synchronize, .exp_sync = srcu_perf_synchronize_expedited, .name = "srcu" }; +static struct srcu_struct srcud; + +static void srcu_sync_perf_init(void) +{ + srcu_ctlp = &srcud; + init_srcu_struct(srcu_ctlp); +} + +static void srcu_sync_perf_cleanup(void) +{ + cleanup_srcu_struct(srcu_ctlp); +} + +static struct rcu_perf_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, + .started = NULL, + .completed = srcu_perf_completed, + .exp_completed = srcu_perf_completed, + .async = srcu_call_rcu, + .gp_barrier = srcu_rcu_barrier, + .sync = srcu_perf_synchronize, + .exp_sync = srcu_perf_synchronize_expedited, + .name = "srcud" +}; + /* * Definitions for sched perf testing. */ @@ -254,6 +310,8 @@ static struct rcu_perf_ops sched_ops = { .started = rcu_batches_started_sched, .completed = rcu_batches_completed_sched, .exp_completed = rcu_exp_batches_completed_sched, + .async = call_rcu_sched, + .gp_barrier = rcu_barrier_sched, .sync = synchronize_sched, .exp_sync = synchronize_sched_expedited, .name = "sched" @@ -281,6 +339,8 @@ static struct rcu_perf_ops tasks_ops = { .readunlock = tasks_perf_read_unlock, .started = rcu_no_completed, .completed = rcu_no_completed, + .async = call_rcu_tasks, + .gp_barrier = rcu_barrier_tasks, .sync = synchronize_rcu_tasks, .exp_sync = synchronize_rcu_tasks, .name = "tasks" @@ -344,6 +404,15 @@ rcu_perf_reader(void *arg) } /* + * Callback function for asynchronous grace periods from rcu_perf_writer(). + */ +static void rcu_perf_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. */ static int @@ -352,6 +421,7 @@ rcu_perf_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; @@ -380,9 +450,27 @@ rcu_perf_writer(void *arg) } do { + if (writer_holdoff) + udelay(writer_holdoff); wdp = &wdpp[i]; *wdp = ktime_get_mono_fast_ns(); - if (gp_exp) { + if (gp_async) { +retry: + if (!rhp) + rhp = kmalloc(sizeof(*rhp), GFP_KERNEL); + if (rhp && atomic_read(this_cpu_ptr(&n_async_inflight)) < gp_async_max) { + rcu_perf_writer_state = RTWS_ASYNC; + atomic_inc(this_cpu_ptr(&n_async_inflight)); + cur_ops->async(rhp, rcu_perf_async_cb); + rhp = NULL; + } else if (!kthread_should_stop()) { + rcu_perf_writer_state = RTWS_BARRIER; + cur_ops->gp_barrier(); + goto retry; + } else { + kfree(rhp); /* Because we are stopping. */ + } + } else if (gp_exp) { rcu_perf_writer_state = RTWS_EXP_SYNC; cur_ops->exp_sync(); } else { @@ -429,6 +517,10 @@ rcu_perf_writer(void *arg) i++; rcu_perf_wait_shutdown(); } while (!torture_must_stop()); + if (gp_async) { + rcu_perf_writer_state = RTWS_BARRIER; + cur_ops->gp_barrier(); + } rcu_perf_writer_state = RTWS_STOPPING; writer_n_durations[me] = i_max; torture_kthread_stopping("rcu_perf_writer"); @@ -452,6 +544,17 @@ rcu_perf_cleanup(void) u64 *wdp; u64 *wdpp; + /* + * Would like warning at start, but everything is expedited + * 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!"); + if (rcu_gp_is_normal() && gp_exp) + VERBOSE_PERFOUT_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!"); + if (torture_cleanup_begin()) return; @@ -554,7 +657,7 @@ rcu_perf_init(void) long i; int firsterr = 0; static struct rcu_perf_ops *perf_ops[] = { - &rcu_ops, &rcu_bh_ops, &srcu_ops, &sched_ops, + &rcu_ops, &rcu_bh_ops, &srcu_ops, &srcud_ops, &sched_ops, RCUPERF_TASKS_OPS }; @@ -624,16 +727,6 @@ rcu_perf_init(void) firsterr = -ENOMEM; goto unwind; } - if (rcu_gp_is_expedited() && !rcu_gp_is_normal() && !gp_exp) { - VERBOSE_PERFOUT_ERRSTRING("All grace periods expedited, no normal ones to measure!"); - firsterr = -EINVAL; - goto unwind; - } - if (rcu_gp_is_normal() && gp_exp) { - VERBOSE_PERFOUT_ERRSTRING("All grace periods normal, no expedited ones to measure!"); - firsterr = -EINVAL; - goto unwind; - } for (i = 0; i < nrealwriters; i++) { writer_durations[i] = kcalloc(MAX_MEAS, sizeof(*writer_durations[i]), diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c index ae6e574d4cf5..b8f7f8ce8575 100644 --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -52,6 +52,8 @@ #include <linux/torture.h> #include <linux/vmalloc.h> +#include "rcu.h" + MODULE_LICENSE("GPL"); MODULE_AUTHOR("Paul E. McKenney <paulmck@us.ibm.com> and Josh Triplett <josh@joshtriplett.org>"); @@ -562,31 +564,19 @@ static void srcu_torture_stats(void) int __maybe_unused cpu; int idx; -#if defined(CONFIG_TREE_SRCU) || defined(CONFIG_CLASSIC_SRCU) #ifdef CONFIG_TREE_SRCU idx = srcu_ctlp->srcu_idx & 0x1; -#else /* #ifdef CONFIG_TREE_SRCU */ - idx = srcu_ctlp->completed & 0x1; -#endif /* #else #ifdef CONFIG_TREE_SRCU */ pr_alert("%s%s Tree SRCU per-CPU(idx=%d):", torture_type, TORTURE_FLAG, idx); for_each_possible_cpu(cpu) { unsigned long l0, l1; unsigned long u0, u1; long c0, c1; -#ifdef CONFIG_TREE_SRCU struct srcu_data *counts; counts = per_cpu_ptr(srcu_ctlp->sda, cpu); u0 = counts->srcu_unlock_count[!idx]; u1 = counts->srcu_unlock_count[idx]; -#else /* #ifdef CONFIG_TREE_SRCU */ - struct srcu_array *counts; - - counts = per_cpu_ptr(srcu_ctlp->per_cpu_ref, cpu); - u0 = counts->unlock_count[!idx]; - u1 = counts->unlock_count[idx]; -#endif /* #else #ifdef CONFIG_TREE_SRCU */ /* * Make sure that a lock is always counted if the corresponding @@ -594,13 +584,8 @@ static void srcu_torture_stats(void) */ smp_rmb(); -#ifdef CONFIG_TREE_SRCU l0 = counts->srcu_lock_count[!idx]; l1 = counts->srcu_lock_count[idx]; -#else /* #ifdef CONFIG_TREE_SRCU */ - l0 = counts->lock_count[!idx]; - l1 = counts->lock_count[idx]; -#endif /* #else #ifdef CONFIG_TREE_SRCU */ c0 = l0 - u0; c1 = l1 - u1; @@ -609,7 +594,7 @@ static void srcu_torture_stats(void) pr_cont("\n"); #elif defined(CONFIG_TINY_SRCU) idx = READ_ONCE(srcu_ctlp->srcu_idx) & 0x1; - pr_alert("%s%s Tiny SRCU per-CPU(idx=%d): (%d,%d)\n", + pr_alert("%s%s Tiny SRCU per-CPU(idx=%d): (%hd,%hd)\n", torture_type, TORTURE_FLAG, idx, READ_ONCE(srcu_ctlp->srcu_lock_nesting[!idx]), READ_ONCE(srcu_ctlp->srcu_lock_nesting[idx])); diff --git a/kernel/rcu/srcu.c b/kernel/rcu/srcu.c deleted file mode 100644 index dea03614263f..000000000000 --- a/kernel/rcu/srcu.c +++ /dev/null @@ -1,661 +0,0 @@ -/* - * Sleepable Read-Copy Update mechanism for mutual exclusion. - * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License as published by - * the Free Software Foundation; either version 2 of the License, or - * (at your option) any later version. - * - * This program is distributed in the hope that it will be useful, - * but WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the - * GNU General Public License for more details. - * - * You should have received a copy of the GNU General Public License - * along with this program; if not, you can access it online at - * http://www.gnu.org/licenses/gpl-2.0.html. - * - * Copyright (C) IBM Corporation, 2006 - * Copyright (C) Fujitsu, 2012 - * - * Author: Paul McKenney <paulmck@us.ibm.com> - * Lai Jiangshan <laijs@cn.fujitsu.com> - * - * For detailed explanation of Read-Copy Update mechanism see - - * Documentation/RCU/ *.txt - * - */ - -#include <linux/export.h> -#include <linux/mutex.h> -#include <linux/percpu.h> -#include <linux/preempt.h> -#include <linux/rcupdate_wait.h> -#include <linux/sched.h> -#include <linux/smp.h> -#include <linux/delay.h> -#include <linux/srcu.h> - -#include "rcu.h" - -/* - * Initialize an rcu_batch structure to empty. - */ -static inline void rcu_batch_init(struct rcu_batch *b) -{ - b->head = NULL; - b->tail = &b->head; -} - -/* - * Enqueue a callback onto the tail of the specified rcu_batch structure. - */ -static inline void rcu_batch_queue(struct rcu_batch *b, struct rcu_head *head) -{ - *b->tail = head; - b->tail = &head->next; -} - -/* - * Is the specified rcu_batch structure empty? - */ -static inline bool rcu_batch_empty(struct rcu_batch *b) -{ - return b->tail == &b->head; -} - -/* - * Remove the callback at the head of the specified rcu_batch structure - * and return a pointer to it, or return NULL if the structure is empty. - */ -static inline struct rcu_head *rcu_batch_dequeue(struct rcu_batch *b) -{ - struct rcu_head *head; - - if (rcu_batch_empty(b)) - return NULL; - - head = b->head; - b->head = head->next; - if (b->tail == &head->next) - rcu_batch_init(b); - - return head; -} - -/* - * Move all callbacks from the rcu_batch structure specified by "from" to - * the structure specified by "to". - */ -static inline void rcu_batch_move(struct rcu_batch *to, struct rcu_batch *from) -{ - if (!rcu_batch_empty(from)) { - *to->tail = from->head; - to->tail = from->tail; - rcu_batch_init(from); - } -} - -static int init_srcu_struct_fields(struct srcu_struct *sp) -{ - sp->completed = 0; - spin_lock_init(&sp->queue_lock); - sp->running = false; - rcu_batch_init(&sp->batch_queue); - rcu_batch_init(&sp->batch_check0); - rcu_batch_init(&sp->batch_check1); - rcu_batch_init(&sp->batch_done); - INIT_DELAYED_WORK(&sp->work, process_srcu); - sp->per_cpu_ref = alloc_percpu(struct srcu_array); - return sp->per_cpu_ref ? 0 : -ENOMEM; -} - -#ifdef CONFIG_DEBUG_LOCK_ALLOC - -int __init_srcu_struct(struct srcu_struct *sp, const char *name, - struct lock_class_key *key) -{ - /* Don't re-initialize a lock while it is held. */ - debug_check_no_locks_freed((void *)sp, sizeof(*sp)); - lockdep_init_map(&sp->dep_map, name, key, 0); - return init_srcu_struct_fields(sp); -} -EXPORT_SYMBOL_GPL(__init_srcu_struct); - -#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ - -/** - * init_srcu_struct - initialize a sleep-RCU structure - * @sp: structure to initialize. - * - * Must invoke this on a given srcu_struct before passing that srcu_struct - * to any other function. Each srcu_struct represents a separate domain - * of SRCU protection. - */ -int init_srcu_struct(struct srcu_struct *sp) -{ - return init_srcu_struct_fields(sp); -} -EXPORT_SYMBOL_GPL(init_srcu_struct); - -#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ - -/* - * Returns approximate total of the readers' ->lock_count[] values for the - * rank of per-CPU counters specified by idx. - */ -static unsigned long srcu_readers_lock_idx(struct srcu_struct *sp, int idx) -{ - int cpu; - unsigned long sum = 0; - - for_each_possible_cpu(cpu) { - struct srcu_array *cpuc = per_cpu_ptr(sp->per_cpu_ref, cpu); - - sum += READ_ONCE(cpuc->lock_count[idx]); - } - return sum; -} - -/* - * Returns approximate total of the readers' ->unlock_count[] values for the - * rank of per-CPU counters specified by idx. - */ -static unsigned long srcu_readers_unlock_idx(struct srcu_struct *sp, int idx) -{ - int cpu; - unsigned long sum = 0; - - for_each_possible_cpu(cpu) { - struct srcu_array *cpuc = per_cpu_ptr(sp->per_cpu_ref, cpu); - - sum += READ_ONCE(cpuc->unlock_count[idx]); - } - return sum; -} - -/* - * Return true if the number of pre-existing readers is determined to - * be zero. - */ -static bool srcu_readers_active_idx_check(struct srcu_struct *sp, int idx) -{ - unsigned long unlocks; - - unlocks = srcu_readers_unlock_idx(sp, idx); - - /* - * Make sure that a lock is always counted if the corresponding unlock - * is counted. Needs to be a smp_mb() as the read side may contain a - * read from a variable that is written to before the synchronize_srcu() - * in the write side. In this case smp_mb()s A and B act like the store - * buffering pattern. - * - * This smp_mb() also pairs with smp_mb() C to prevent accesses after the - * synchronize_srcu() from being executed before the grace period ends. - */ - smp_mb(); /* A */ - - /* - * If the locks are the same as the unlocks, then there must have - * been no readers on this index at some time in between. This does not - * mean that there are no more readers, as one could have read the - * current index but not have incremented the lock counter yet. - * - * Possible bug: There is no guarantee that there haven't been ULONG_MAX - * increments of ->lock_count[] since the unlocks were counted, meaning - * that this could return true even if there are still active readers. - * Since there are no memory barriers around srcu_flip(), the CPU is not - * required to increment ->completed before running - * srcu_readers_unlock_idx(), which means that there could be an - * arbitrarily large number of critical sections that execute after - * srcu_readers_unlock_idx() but use the old value of ->completed. - */ - return srcu_readers_lock_idx(sp, idx) == unlocks; -} - -/** - * srcu_readers_active - returns true if there are readers. and false - * otherwise - * @sp: which srcu_struct to count active readers (holding srcu_read_lock). - * - * Note that this is not an atomic primitive, and can therefore suffer - * severe errors when invoked on an active srcu_struct. That said, it - * can be useful as an error check at cleanup time. - */ -static bool srcu_readers_active(struct srcu_struct *sp) -{ - int cpu; - unsigned long sum = 0; - - for_each_possible_cpu(cpu) { - struct srcu_array *cpuc = per_cpu_ptr(sp->per_cpu_ref, cpu); - - sum += READ_ONCE(cpuc->lock_count[0]); - sum += READ_ONCE(cpuc->lock_count[1]); - sum -= READ_ONCE(cpuc->unlock_count[0]); - sum -= READ_ONCE(cpuc->unlock_count[1]); - } - return sum; -} - -/** - * cleanup_srcu_struct - deconstruct a sleep-RCU structure - * @sp: structure to clean up. - * - * Must invoke this only after you are finished using a given srcu_struct - * that was initialized via init_srcu_struct(). This code does some - * probabalistic checking, spotting late uses of srcu_read_lock(), - * synchronize_srcu(), synchronize_srcu_expedited(), and call_srcu(). - * If any such late uses are detected, the per-CPU memory associated with - * the srcu_struct is simply leaked and WARN_ON() is invoked. If the - * caller frees the srcu_struct itself, a use-after-free crash will likely - * ensue, but at least there will be a warning printed. - */ -void cleanup_srcu_struct(struct srcu_struct *sp) -{ - if (WARN_ON(srcu_readers_active(sp))) - return; /* Leakage unless caller handles error. */ - free_percpu(sp->per_cpu_ref); - sp->per_cpu_ref = NULL; -} -EXPORT_SYMBOL_GPL(cleanup_srcu_struct); - -/* - * Counts the new reader in the appropriate per-CPU element of the - * srcu_struct. - * Returns an index that must be passed to the matching srcu_read_unlock(). - */ -int __srcu_read_lock(struct srcu_struct *sp) -{ - int idx; - - idx = READ_ONCE(sp->completed) & 0x1; - this_cpu_inc(sp->per_cpu_ref->lock_count[idx]); - smp_mb(); /* B */ /* Avoid leaking the critical section. */ - return idx; -} -EXPORT_SYMBOL_GPL(__srcu_read_lock); - -/* - * Removes the count for the old reader from the appropriate per-CPU - * element of the srcu_struct. Note that this may well be a different - * CPU than that which was incremented by the corresponding srcu_read_lock(). - */ -void __srcu_read_unlock(struct srcu_struct *sp, int idx) -{ - smp_mb(); /* C */ /* Avoid leaking the critical section. */ - this_cpu_inc(sp->per_cpu_ref->unlock_count[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 10 microseconds, - * we repeatedly block for 1-millisecond time periods. This approach - * has done well in testing, so there is no need for a config parameter. - */ -#define SRCU_RETRY_CHECK_DELAY 5 -#define SYNCHRONIZE_SRCU_TRYCOUNT 2 -#define SYNCHRONIZE_SRCU_EXP_TRYCOUNT 12 - -/* - * @@@ Wait until all pre-existing readers complete. Such readers - * will have used the index specified by "idx". - * the caller should ensures the ->completed is not changed while checking - * and idx = (->completed & 1) ^ 1 - */ -static bool try_check_zero(struct srcu_struct *sp, int idx, int trycount) -{ - for (;;) { - if (srcu_readers_active_idx_check(sp, idx)) - return true; - if (--trycount <= 0) - return false; - udelay(SRCU_RETRY_CHECK_DELAY); - } -} - -/* - * Increment the ->completed counter so that future SRCU readers will - * use the other rank of the ->(un)lock_count[] arrays. This allows - * us to wait for pre-existing readers in a starvation-free manner. - */ -static void srcu_flip(struct srcu_struct *sp) -{ - WRITE_ONCE(sp->completed, sp->completed + 1); - - /* - * Ensure that if the updater misses an __srcu_read_unlock() - * increment, that task's next __srcu_read_lock() will see the - * above counter update. Note that both this memory barrier - * and the one in srcu_readers_active_idx_check() provide the - * guarantee for __srcu_read_lock(). - */ - smp_mb(); /* D */ /* Pairs with C. */ -} - -/* - * Enqueue an SRCU callback on the specified srcu_struct structure, - * initiating grace-period processing if it is not already running. - * - * Note that all CPUs must agree that the grace period extended beyond - * all pre-existing SRCU 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 corresponding SRCU read-side critical section whose beginning - * preceded the call to call_rcu(). It also means that each CPU executing - * an SRCU 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 SRCU 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 SRCU 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()". - * This guarantee applies even if CPU A and CPU B are the same CPU (but - * again only if the system has more than one CPU). - * - * Of course, these guarantees apply only for invocations of call_srcu(), - * srcu_read_lock(), and srcu_read_unlock() that are all passed the same - * srcu_struct structure. - */ -void call_srcu(struct srcu_struct *sp, struct rcu_head *head, - rcu_callback_t func) -{ - unsigned long flags; - - head->next = NULL; - head->func = func; - spin_lock_irqsave(&sp->queue_lock, flags); - smp_mb__after_unlock_lock(); /* Caller's prior accesses before GP. */ - rcu_batch_queue(&sp->batch_queue, head); - if (!sp->running) { - sp->running = true; - queue_delayed_work(system_power_efficient_wq, &sp->work, 0); - } - spin_unlock_irqrestore(&sp->queue_lock, flags); -} -EXPORT_SYMBOL_GPL(call_srcu); - -static void srcu_advance_batches(struct srcu_struct *sp, int trycount); -static void srcu_reschedule(struct srcu_struct *sp); - -/* - * Helper function for synchronize_srcu() and synchronize_srcu_expedited(). - */ -static void __synchronize_srcu(struct srcu_struct *sp, int trycount) -{ - struct rcu_synchronize rcu; - struct rcu_head *head = &rcu.head; - bool done = false; - - RCU_LOCKDEP_WARN(lock_is_held(&sp->dep_map) || - lock_is_held(&rcu_bh_lock_map) || - lock_is_held(&rcu_lock_map) || - lock_is_held(&rcu_sched_lock_map), - "Illegal synchronize_srcu() in same-type SRCU (or in RCU) read-side critical section"); - - might_sleep(); - init_completion(&rcu.completion); - - head->next = NULL; - head->func = wakeme_after_rcu; - spin_lock_irq(&sp->queue_lock); - smp_mb__after_unlock_lock(); /* Caller's prior accesses before GP. */ - if (!sp->running) { - /* steal the processing owner */ - sp->running = true; - rcu_batch_queue(&sp->batch_check0, head); - spin_unlock_irq(&sp->queue_lock); - - srcu_advance_batches(sp, trycount); - if (!rcu_batch_empty(&sp->batch_done)) { - BUG_ON(sp->batch_done.head != head); - rcu_batch_dequeue(&sp->batch_done); - done = true; - } - /* give the processing owner to work_struct */ - srcu_reschedule(sp); - } else { - rcu_batch_queue(&sp->batch_queue, head); - spin_unlock_irq(&sp->queue_lock); - } - - if (!done) { - wait_for_completion(&rcu.completion); - smp_mb(); /* Caller's later accesses after GP. */ - } - -} - -/** - * synchronize_srcu - wait for prior SRCU read-side critical-section completion - * @sp: srcu_struct with which to synchronize. - * - * Wait for the count to drain to zero of both indexes. To avoid the - * possible starvation of synchronize_srcu(), it waits for the count of - * the index=((->completed & 1) ^ 1) to drain to zero at first, - * and then flip the completed and wait for the count of the other index. - * - * Can block; must be called from process context. - * - * Note that it is illegal to call synchronize_srcu() from the corresponding - * SRCU read-side critical section; doing so will result in deadlock. - * However, it is perfectly legal to call synchronize_srcu() on one - * srcu_struct from some other srcu_struct's read-side critical section, - * as long as the resulting graph of srcu_structs is acyclic. - * - * There are memory-ordering constraints implied by synchronize_srcu(). - * On systems with more than one CPU, when synchronize_srcu() returns, - * each CPU is guaranteed to have executed a full memory barrier since - * the end of its last corresponding SRCU-sched read-side critical section - * whose beginning preceded the call to synchronize_srcu(). In addition, - * each CPU having an SRCU read-side critical section that extends beyond - * the return from synchronize_srcu() is guaranteed to have executed a - * full memory barrier after the beginning of synchronize_srcu() and before - * the beginning of that SRCU 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_srcu(), 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_srcu(). This guarantee applies even if CPU A and CPU B - * are the same CPU, but again only if the system has more than one CPU. - * - * Of course, these memory-ordering guarantees apply only when - * synchronize_srcu(), srcu_read_lock(), and srcu_read_unlock() are - * passed the same srcu_struct structure. - */ -void synchronize_srcu(struct srcu_struct *sp) -{ - __synchronize_srcu(sp, (rcu_gp_is_expedited() && !rcu_gp_is_normal()) - ? SYNCHRONIZE_SRCU_EXP_TRYCOUNT - : SYNCHRONIZE_SRCU_TRYCOUNT); -} -EXPORT_SYMBOL_GPL(synchronize_srcu); - -/** - * synchronize_srcu_expedited - Brute-force SRCU grace period - * @sp: srcu_struct with which to synchronize. - * - * Wait for an SRCU grace period to elapse, but be more aggressive about - * spinning rather than blocking when waiting. - * - * Note that synchronize_srcu_expedited() has the same deadlock and - * memory-ordering properties as does synchronize_srcu(). - */ -void synchronize_srcu_expedited(struct srcu_struct *sp) -{ - __synchronize_srcu(sp, SYNCHRONIZE_SRCU_EXP_TRYCOUNT); -} -EXPORT_SYMBOL_GPL(synchronize_srcu_expedited); - -/** - * srcu_barrier - Wait until all in-flight call_srcu() callbacks complete. - * @sp: srcu_struct on which to wait for in-flight callbacks. - */ -void srcu_barrier(struct srcu_struct *sp) -{ - synchronize_srcu(sp); -} -EXPORT_SYMBOL_GPL(srcu_barrier); - -/** - * srcu_batches_completed - return batches completed. - * @sp: srcu_struct on which to report batch completion. - * - * Report the number of batches, correlated with, but not necessarily - * precisely the same as, the number of grace periods that have elapsed. - */ -unsigned long srcu_batches_completed(struct srcu_struct *sp) -{ - return sp->completed; -} -EXPORT_SYMBOL_GPL(srcu_batches_completed); - -#define SRCU_CALLBACK_BATCH 10 -#define SRCU_INTERVAL 1 - -/* - * Move any new SRCU callbacks to the first stage of the SRCU grace - * period pipeline. - */ -static void srcu_collect_new(struct srcu_struct *sp) -{ - if (!rcu_batch_empty(&sp->batch_queue)) { - spin_lock_irq(&sp->queue_lock); - rcu_batch_move(&sp->batch_check0, &sp->batch_queue); - spin_unlock_irq(&sp->queue_lock); - } -} - -/* - * Core SRCU state machine. Advance callbacks from ->batch_check0 to - * ->batch_check1 and then to ->batch_done as readers drain. - */ -static void srcu_advance_batches(struct srcu_struct *sp, int trycount) -{ - int idx = 1 ^ (sp->completed & 1); - - /* - * Because readers might be delayed for an extended period after - * fetching ->completed for their index, at any point in time there - * might well be readers using both idx=0 and idx=1. We therefore - * need to wait for readers to clear from both index values before - * invoking a callback. - */ - - if (rcu_batch_empty(&sp->batch_check0) && - rcu_batch_empty(&sp->batch_check1)) - return; /* no callbacks need to be advanced */ - - if (!try_check_zero(sp, idx, trycount)) - return; /* failed to advance, will try after SRCU_INTERVAL */ - - /* - * The callbacks in ->batch_check1 have already done with their - * first zero check and flip back when they were enqueued on - * ->batch_check0 in a previous invocation of srcu_advance_batches(). - * (Presumably try_check_zero() returned false during that - * invocation, leaving the callbacks stranded on ->batch_check1.) - * They are therefore ready to invoke, so move them to ->batch_done. - */ - rcu_batch_move(&sp->batch_done, &sp->batch_check1); - - if (rcu_batch_empty(&sp->batch_check0)) - return; /* no callbacks need to be advanced */ - srcu_flip(sp); - - /* - * The callbacks in ->batch_check0 just finished their - * first check zero and flip, so move them to ->batch_check1 - * for future checking on the other idx. - */ - rcu_batch_move(&sp->batch_check1, &sp->batch_check0); - - /* - * SRCU read-side critical sections are normally short, so check - * at least twice in quick succession after a flip. - */ - trycount = trycount < 2 ? 2 : trycount; - if (!try_check_zero(sp, idx^1, trycount)) - return; /* failed to advance, will try after SRCU_INTERVAL */ - - /* - * The callbacks in ->batch_check1 have now waited for all - * pre-existing readers using both idx values. They are therefore - * ready to invoke, so move them to ->batch_done. - */ - rcu_batch_move(&sp->batch_done, &sp->batch_check1); -} - -/* - * Invoke a limited number of SRCU callbacks that have passed through - * their grace period. If there are more to do, SRCU will reschedule - * the workqueue. Note that needed memory barriers have been executed - * in this task's context by srcu_readers_active_idx_check(). - */ -static void srcu_invoke_callbacks(struct srcu_struct *sp) -{ - int i; - struct rcu_head *head; - - for (i = 0; i < SRCU_CALLBACK_BATCH; i++) { - head = rcu_batch_dequeue(&sp->batch_done); - if (!head) - break; - local_bh_disable(); - head->func(head); - local_bh_enable(); - } -} - -/* - * Finished one round of SRCU grace period. Start another if there are - * more SRCU callbacks queued, otherwise put SRCU into not-running state. - */ -static void srcu_reschedule(struct srcu_struct *sp) -{ - bool pending = true; - - if (rcu_batch_empty(&sp->batch_done) && - rcu_batch_empty(&sp->batch_check1) && - rcu_batch_empty(&sp->batch_check0) && - rcu_batch_empty(&sp->batch_queue)) { - spin_lock_irq(&sp->queue_lock); - if (rcu_batch_empty(&sp->batch_done) && - rcu_batch_empty(&sp->batch_check1) && - rcu_batch_empty(&sp->batch_check0) && - rcu_batch_empty(&sp->batch_queue)) { - sp->running = false; - pending = false; - } - spin_unlock_irq(&sp->queue_lock); - } - - if (pending) - queue_delayed_work(system_power_efficient_wq, - &sp->work, SRCU_INTERVAL); -} - -/* - * This is the work-queue function that handles SRCU grace periods. - */ -void process_srcu(struct work_struct *work) -{ - struct srcu_struct *sp; - - sp = container_of(work, struct srcu_struct, work.work); - - srcu_collect_new(sp); - srcu_advance_batches(sp, 1); - srcu_invoke_callbacks(sp); - srcu_reschedule(sp); -} -EXPORT_SYMBOL_GPL(process_srcu); diff --git a/kernel/rcu/srcutiny.c b/kernel/rcu/srcutiny.c index 32798eb14853..1a1c1047d2ed 100644 --- a/kernel/rcu/srcutiny.c +++ b/kernel/rcu/srcutiny.c @@ -38,8 +38,8 @@ static int init_srcu_struct_fields(struct srcu_struct *sp) sp->srcu_lock_nesting[0] = 0; sp->srcu_lock_nesting[1] = 0; init_swait_queue_head(&sp->srcu_wq); - sp->srcu_gp_seq = 0; - rcu_segcblist_init(&sp->srcu_cblist); + sp->srcu_cb_head = NULL; + sp->srcu_cb_tail = &sp->srcu_cb_head; sp->srcu_gp_running = false; sp->srcu_gp_waiting = false; sp->srcu_idx = 0; @@ -88,30 +88,14 @@ void cleanup_srcu_struct(struct srcu_struct *sp) { WARN_ON(sp->srcu_lock_nesting[0] || sp->srcu_lock_nesting[1]); flush_work(&sp->srcu_work); - WARN_ON(rcu_seq_state(sp->srcu_gp_seq)); WARN_ON(sp->srcu_gp_running); WARN_ON(sp->srcu_gp_waiting); - WARN_ON(!rcu_segcblist_empty(&sp->srcu_cblist)); + WARN_ON(sp->srcu_cb_head); + WARN_ON(&sp->srcu_cb_head != sp->srcu_cb_tail); } EXPORT_SYMBOL_GPL(cleanup_srcu_struct); /* - * Counts the new reader in the appropriate per-CPU element of the - * srcu_struct. Can be invoked from irq/bh handlers, but the matching - * __srcu_read_unlock() must be in the same handler instance. Returns an - * index that must be passed to the matching srcu_read_unlock(). - */ -int __srcu_read_lock(struct srcu_struct *sp) -{ - int idx; - - idx = READ_ONCE(sp->srcu_idx); - WRITE_ONCE(sp->srcu_lock_nesting[idx], sp->srcu_lock_nesting[idx] + 1); - return idx; -} -EXPORT_SYMBOL_GPL(__srcu_read_lock); - -/* * Removes the count for the old reader from the appropriate element of * the srcu_struct. */ @@ -133,52 +117,44 @@ EXPORT_SYMBOL_GPL(__srcu_read_unlock); void srcu_drive_gp(struct work_struct *wp) { int idx; - struct rcu_cblist ready_cbs; - struct srcu_struct *sp; + struct rcu_head *lh; struct rcu_head *rhp; + struct srcu_struct *sp; sp = container_of(wp, struct srcu_struct, srcu_work); - if (sp->srcu_gp_running || rcu_segcblist_empty(&sp->srcu_cblist)) + if (sp->srcu_gp_running || !READ_ONCE(sp->srcu_cb_head)) return; /* Already running or nothing to do. */ - /* Tag recently arrived callbacks and wait for readers. */ + /* Remove recently arrived callbacks and wait for readers. */ WRITE_ONCE(sp->srcu_gp_running, true); - rcu_segcblist_accelerate(&sp->srcu_cblist, - rcu_seq_snap(&sp->srcu_gp_seq)); - rcu_seq_start(&sp->srcu_gp_seq); + local_irq_disable(); + lh = sp->srcu_cb_head; + sp->srcu_cb_head = NULL; + sp->srcu_cb_tail = &sp->srcu_cb_head; + local_irq_enable(); idx = sp->srcu_idx; WRITE_ONCE(sp->srcu_idx, !sp->srcu_idx); WRITE_ONCE(sp->srcu_gp_waiting, true); /* srcu_read_unlock() wakes! */ swait_event(sp->srcu_wq, !READ_ONCE(sp->srcu_lock_nesting[idx])); WRITE_ONCE(sp->srcu_gp_waiting, false); /* srcu_read_unlock() cheap. */ - rcu_seq_end(&sp->srcu_gp_seq); - - /* Update callback list based on GP, and invoke ready callbacks. */ - rcu_segcblist_advance(&sp->srcu_cblist, - rcu_seq_current(&sp->srcu_gp_seq)); - if (rcu_segcblist_ready_cbs(&sp->srcu_cblist)) { - rcu_cblist_init(&ready_cbs); - local_irq_disable(); - rcu_segcblist_extract_done_cbs(&sp->srcu_cblist, &ready_cbs); - local_irq_enable(); - rhp = rcu_cblist_dequeue(&ready_cbs); - for (; rhp != NULL; rhp = rcu_cblist_dequeue(&ready_cbs)) { - local_bh_disable(); - rhp->func(rhp); - local_bh_enable(); - } - local_irq_disable(); - rcu_segcblist_insert_count(&sp->srcu_cblist, &ready_cbs); - local_irq_enable(); + + /* Invoke the callbacks we removed above. */ + while (lh) { + rhp = lh; + lh = lh->next; + local_bh_disable(); + rhp->func(rhp); + local_bh_enable(); } - WRITE_ONCE(sp->srcu_gp_running, false); /* - * If more callbacks, reschedule ourselves. This can race with - * a call_srcu() at interrupt level, but the ->srcu_gp_running - * checks will straighten that out. + * Enable rescheduling, and if there are more callbacks, + * reschedule ourselves. This can race with a call_srcu() + * at interrupt level, but the ->srcu_gp_running checks will + * straighten that out. */ - if (!rcu_segcblist_empty(&sp->srcu_cblist)) + WRITE_ONCE(sp->srcu_gp_running, false); + if (READ_ONCE(sp->srcu_cb_head)) schedule_work(&sp->srcu_work); } EXPORT_SYMBOL_GPL(srcu_drive_gp); @@ -187,14 +163,16 @@ EXPORT_SYMBOL_GPL(srcu_drive_gp); * Enqueue an SRCU callback on the specified srcu_struct structure, * initiating grace-period processing if it is not already running. */ -void call_srcu(struct srcu_struct *sp, struct rcu_head *head, +void call_srcu(struct srcu_struct *sp, struct rcu_head *rhp, rcu_callback_t func) { unsigned long flags; - head->func = func; + rhp->func = func; + rhp->next = NULL; local_irq_save(flags); - rcu_segcblist_enqueue(&sp->srcu_cblist, head, false); + *sp->srcu_cb_tail = rhp; + sp->srcu_cb_tail = &rhp->next; local_irq_restore(flags); if (!READ_ONCE(sp->srcu_gp_running)) schedule_work(&sp->srcu_work); diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c index 157654fa436a..d0ca524bf042 100644 --- a/kernel/rcu/srcutree.c +++ b/kernel/rcu/srcutree.c @@ -40,9 +40,15 @@ #include "rcu.h" #include "rcu_segcblist.h" -ulong exp_holdoff = 25 * 1000; /* Holdoff (ns) for auto-expediting. */ +/* Holdoff in nanoseconds for auto-expediting. */ +#define DEFAULT_SRCU_EXP_HOLDOFF (25 * 1000) +static ulong exp_holdoff = DEFAULT_SRCU_EXP_HOLDOFF; module_param(exp_holdoff, ulong, 0444); +/* Overflow-check frequency. N bits roughly says every 2**N grace periods. */ +static ulong counter_wrap_check = (ULONG_MAX >> 2); +module_param(counter_wrap_check, ulong, 0444); + static void srcu_invoke_callbacks(struct work_struct *work); static void srcu_reschedule(struct srcu_struct *sp, unsigned long delay); @@ -70,7 +76,7 @@ static void init_srcu_struct_nodes(struct srcu_struct *sp, bool is_static) /* Each pass through this loop initializes one srcu_node structure. */ rcu_for_each_node_breadth_first(sp, snp) { - spin_lock_init(&snp->lock); + raw_spin_lock_init(&ACCESS_PRIVATE(snp, lock)); 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++) { @@ -104,7 +110,7 @@ static void init_srcu_struct_nodes(struct srcu_struct *sp, bool is_static) snp_first = sp->level[level]; for_each_possible_cpu(cpu) { sdp = per_cpu_ptr(sp->sda, cpu); - spin_lock_init(&sdp->lock); + raw_spin_lock_init(&ACCESS_PRIVATE(sdp, lock)); rcu_segcblist_init(&sdp->srcu_cblist); sdp->srcu_cblist_invoking = false; sdp->srcu_gp_seq_needed = sp->srcu_gp_seq; @@ -163,7 +169,7 @@ int __init_srcu_struct(struct srcu_struct *sp, const char *name, /* Don't re-initialize a lock while it is held. */ debug_check_no_locks_freed((void *)sp, sizeof(*sp)); lockdep_init_map(&sp->dep_map, name, key, 0); - spin_lock_init(&sp->gp_lock); + raw_spin_lock_init(&ACCESS_PRIVATE(sp, lock)); return init_srcu_struct_fields(sp, false); } EXPORT_SYMBOL_GPL(__init_srcu_struct); @@ -180,7 +186,7 @@ EXPORT_SYMBOL_GPL(__init_srcu_struct); */ int init_srcu_struct(struct srcu_struct *sp) { - spin_lock_init(&sp->gp_lock); + raw_spin_lock_init(&ACCESS_PRIVATE(sp, lock)); return init_srcu_struct_fields(sp, false); } EXPORT_SYMBOL_GPL(init_srcu_struct); @@ -191,7 +197,7 @@ EXPORT_SYMBOL_GPL(init_srcu_struct); * 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 - * to each update-side SRCU primitive. Use ->gp_lock, which -is- + * to each update-side SRCU primitive. Use sp->lock, which -is- * compile-time initialized, to resolve races involving multiple * CPUs trying to garner first-use privileges. */ @@ -203,13 +209,13 @@ static void check_init_srcu_struct(struct srcu_struct *sp) /* The smp_load_acquire() pairs with the smp_store_release(). */ if (!rcu_seq_state(smp_load_acquire(&sp->srcu_gp_seq_needed))) /*^^^*/ return; /* Already initialized. */ - spin_lock_irqsave(&sp->gp_lock, flags); + raw_spin_lock_irqsave_rcu_node(sp, flags); if (!rcu_seq_state(sp->srcu_gp_seq_needed)) { - spin_unlock_irqrestore(&sp->gp_lock, flags); + raw_spin_unlock_irqrestore_rcu_node(sp, flags); return; } init_srcu_struct_fields(sp, true); - spin_unlock_irqrestore(&sp->gp_lock, flags); + raw_spin_unlock_irqrestore_rcu_node(sp, flags); } /* @@ -275,15 +281,20 @@ static bool srcu_readers_active_idx_check(struct srcu_struct *sp, int idx) * not mean that there are no more readers, as one could have read * the current index but not have incremented the lock counter yet. * - * Possible bug: There is no guarantee that there haven't been - * ULONG_MAX increments of ->srcu_lock_count[] since the unlocks were - * counted, meaning that this could return true even if there are - * still active readers. Since there are no memory barriers around - * srcu_flip(), the CPU is not required to increment ->srcu_idx - * before running srcu_readers_unlock_idx(), which means that there - * could be an arbitrarily large number of critical sections that - * execute after srcu_readers_unlock_idx() but use the old value - * of ->srcu_idx. + * So suppose that the updater is preempted here for so long + * that more than ULONG_MAX non-nested readers come and go in + * the meantime. It turns out that this cannot result in overflow + * because if a reader modifies its unlock count after we read it + * above, then that reader's next load of ->srcu_idx is guaranteed + * to get the new value, which will cause it to operate on the + * other bank of counters, where it cannot contribute to the + * overflow of these counters. This means that there is a maximum + * of 2*NR_CPUS increments, which cannot overflow given current + * systems, especially not on 64-bit systems. + * + * OK, how about nesting? This does impose a limit on nesting + * of floor(ULONG_MAX/NR_CPUS/2), which should be sufficient, + * especially on 64-bit systems. */ return srcu_readers_lock_idx(sp, idx) == unlocks; } @@ -400,8 +411,7 @@ static void srcu_gp_start(struct srcu_struct *sp) struct srcu_data *sdp = this_cpu_ptr(sp->sda); int state; - RCU_LOCKDEP_WARN(!lockdep_is_held(&sp->gp_lock), - "Invoked srcu_gp_start() without ->gp_lock!"); + lockdep_assert_held(&sp->lock); WARN_ON_ONCE(ULONG_CMP_GE(sp->srcu_gp_seq, sp->srcu_gp_seq_needed)); rcu_segcblist_advance(&sdp->srcu_cblist, rcu_seq_current(&sp->srcu_gp_seq)); @@ -489,17 +499,20 @@ static void srcu_gp_end(struct srcu_struct *sp) { unsigned long cbdelay; bool cbs; + int cpu; + unsigned long flags; unsigned long gpseq; int idx; int idxnext; unsigned long mask; + struct srcu_data *sdp; struct srcu_node *snp; /* Prevent more than one additional grace period. */ mutex_lock(&sp->srcu_cb_mutex); /* End the current grace period. */ - spin_lock_irq(&sp->gp_lock); + raw_spin_lock_irq_rcu_node(sp); idx = rcu_seq_state(sp->srcu_gp_seq); WARN_ON_ONCE(idx != SRCU_STATE_SCAN2); cbdelay = srcu_get_delay(sp); @@ -508,7 +521,7 @@ static void srcu_gp_end(struct srcu_struct *sp) gpseq = rcu_seq_current(&sp->srcu_gp_seq); if (ULONG_CMP_LT(sp->srcu_gp_seq_needed_exp, gpseq)) sp->srcu_gp_seq_needed_exp = gpseq; - spin_unlock_irq(&sp->gp_lock); + raw_spin_unlock_irq_rcu_node(sp); mutex_unlock(&sp->srcu_gp_mutex); /* A new grace period can start at this point. But only one. */ @@ -516,7 +529,7 @@ static void srcu_gp_end(struct srcu_struct *sp) idx = rcu_seq_ctr(gpseq) % ARRAY_SIZE(snp->srcu_have_cbs); idxnext = (idx + 1) % ARRAY_SIZE(snp->srcu_have_cbs); rcu_for_each_node_breadth_first(sp, snp) { - spin_lock_irq(&snp->lock); + raw_spin_lock_irq_rcu_node(snp); cbs = false; if (snp >= sp->level[rcu_num_lvls - 1]) cbs = snp->srcu_have_cbs[idx] == gpseq; @@ -526,28 +539,37 @@ static void srcu_gp_end(struct srcu_struct *sp) snp->srcu_gp_seq_needed_exp = gpseq; mask = snp->srcu_data_have_cbs[idx]; snp->srcu_data_have_cbs[idx] = 0; - spin_unlock_irq(&snp->lock); - if (cbs) { - smp_mb(); /* GP end before CB invocation. */ + raw_spin_unlock_irq_rcu_node(snp); + if (cbs) srcu_schedule_cbs_snp(sp, snp, mask, cbdelay); - } + + /* Occasionally prevent srcu_data counter wrap. */ + if (!(gpseq & counter_wrap_check)) + for (cpu = snp->grplo; cpu <= snp->grphi; cpu++) { + sdp = per_cpu_ptr(sp->sda, cpu); + raw_spin_lock_irqsave_rcu_node(sdp, flags); + if (ULONG_CMP_GE(gpseq, + sdp->srcu_gp_seq_needed + 100)) + sdp->srcu_gp_seq_needed = gpseq; + raw_spin_unlock_irqrestore_rcu_node(sdp, flags); + } } /* Callback initiation done, allow grace periods after next. */ mutex_unlock(&sp->srcu_cb_mutex); /* Start a new grace period if needed. */ - spin_lock_irq(&sp->gp_lock); + raw_spin_lock_irq_rcu_node(sp); gpseq = rcu_seq_current(&sp->srcu_gp_seq); if (!rcu_seq_state(gpseq) && ULONG_CMP_LT(gpseq, sp->srcu_gp_seq_needed)) { srcu_gp_start(sp); - spin_unlock_irq(&sp->gp_lock); + raw_spin_unlock_irq_rcu_node(sp); /* Throttle expedited grace periods: Should be rare! */ srcu_reschedule(sp, rcu_seq_ctr(gpseq) & 0x3ff ? 0 : SRCU_INTERVAL); } else { - spin_unlock_irq(&sp->gp_lock); + raw_spin_unlock_irq_rcu_node(sp); } } @@ -567,18 +589,18 @@ static void srcu_funnel_exp_start(struct srcu_struct *sp, struct srcu_node *snp, if (rcu_seq_done(&sp->srcu_gp_seq, s) || ULONG_CMP_GE(READ_ONCE(snp->srcu_gp_seq_needed_exp), s)) return; - spin_lock_irqsave(&snp->lock, flags); + raw_spin_lock_irqsave_rcu_node(snp, flags); if (ULONG_CMP_GE(snp->srcu_gp_seq_needed_exp, s)) { - spin_unlock_irqrestore(&snp->lock, flags); + raw_spin_unlock_irqrestore_rcu_node(snp, flags); return; } WRITE_ONCE(snp->srcu_gp_seq_needed_exp, s); - spin_unlock_irqrestore(&snp->lock, flags); + raw_spin_unlock_irqrestore_rcu_node(snp, flags); } - spin_lock_irqsave(&sp->gp_lock, flags); + raw_spin_lock_irqsave_rcu_node(sp, flags); if (!ULONG_CMP_LT(sp->srcu_gp_seq_needed_exp, s)) sp->srcu_gp_seq_needed_exp = s; - spin_unlock_irqrestore(&sp->gp_lock, flags); + raw_spin_unlock_irqrestore_rcu_node(sp, flags); } /* @@ -600,14 +622,13 @@ static void srcu_funnel_gp_start(struct srcu_struct *sp, struct srcu_data *sdp, for (; snp != NULL; snp = snp->srcu_parent) { if (rcu_seq_done(&sp->srcu_gp_seq, s) && snp != sdp->mynode) return; /* GP already done and CBs recorded. */ - spin_lock_irqsave(&snp->lock, flags); + raw_spin_lock_irqsave_rcu_node(snp, flags); if (ULONG_CMP_GE(snp->srcu_have_cbs[idx], s)) { 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(&snp->lock, flags); + raw_spin_unlock_irqrestore_rcu_node(snp, flags); if (snp == sdp->mynode && snp_seq != s) { - smp_mb(); /* CBs after GP! */ srcu_schedule_cbs_sdp(sdp, do_norm ? SRCU_INTERVAL : 0); @@ -622,11 +643,11 @@ static void srcu_funnel_gp_start(struct srcu_struct *sp, struct srcu_data *sdp, 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(&snp->lock, flags); + raw_spin_unlock_irqrestore_rcu_node(snp, flags); } /* Top of tree, must ensure the grace period will be started. */ - spin_lock_irqsave(&sp->gp_lock, flags); + raw_spin_lock_irqsave_rcu_node(sp, flags); if (ULONG_CMP_LT(sp->srcu_gp_seq_needed, s)) { /* * Record need for grace period s. Pair with load @@ -645,7 +666,7 @@ static void srcu_funnel_gp_start(struct srcu_struct *sp, struct srcu_data *sdp, queue_delayed_work(system_power_efficient_wq, &sp->work, srcu_get_delay(sp)); } - spin_unlock_irqrestore(&sp->gp_lock, flags); + raw_spin_unlock_irqrestore_rcu_node(sp, flags); } /* @@ -671,6 +692,16 @@ static bool try_check_zero(struct srcu_struct *sp, int idx, int trycount) */ static void srcu_flip(struct srcu_struct *sp) { + /* + * Ensure that if this updater saw a given reader's increment + * from __srcu_read_lock(), that reader was using an old value + * of ->srcu_idx. Also ensure that if a given reader sees the + * new value of ->srcu_idx, this updater's earlier scans cannot + * have seen that reader's increments (which is OK, because this + * grace period need not wait on that reader). + */ + smp_mb(); /* E */ /* Pairs with B and C. */ + WRITE_ONCE(sp->srcu_idx, sp->srcu_idx + 1); /* @@ -745,6 +776,13 @@ static bool srcu_might_be_idle(struct srcu_struct *sp) } /* + * SRCU callback function to leak a callback. + */ +static void srcu_leak_callback(struct rcu_head *rhp) +{ +} + +/* * 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. @@ -782,10 +820,16 @@ void __call_srcu(struct srcu_struct *sp, struct rcu_head *rhp, struct srcu_data *sdp; check_init_srcu_struct(sp); + if (debug_rcu_head_queue(rhp)) { + /* Probable double call_srcu(), so leak the callback. */ + WRITE_ONCE(rhp->func, srcu_leak_callback); + WARN_ONCE(1, "call_srcu(): Leaked duplicate callback\n"); + return; + } rhp->func = func; local_irq_save(flags); sdp = this_cpu_ptr(sp->sda); - spin_lock(&sdp->lock); + raw_spin_lock_rcu_node(sdp); rcu_segcblist_enqueue(&sdp->srcu_cblist, rhp, false); rcu_segcblist_advance(&sdp->srcu_cblist, rcu_seq_current(&sp->srcu_gp_seq)); @@ -799,13 +843,30 @@ void __call_srcu(struct srcu_struct *sp, struct rcu_head *rhp, sdp->srcu_gp_seq_needed_exp = s; needexp = true; } - spin_unlock_irqrestore(&sdp->lock, flags); + raw_spin_unlock_irqrestore_rcu_node(sdp, flags); if (needgp) srcu_funnel_gp_start(sp, sdp, s, do_norm); else if (needexp) srcu_funnel_exp_start(sp, sdp->mynode, s); } +/** + * call_srcu() - Queue a callback for invocation after an SRCU grace period + * @sp: srcu_struct in queue the callback + * @head: structure to be used for queueing the SRCU callback. + * @func: function to be invoked after the SRCU grace period + * + * The callback function will be invoked some time after a full SRCU + * grace period elapses, in other words after all pre-existing SRCU + * read-side critical sections have completed. However, the callback + * function might well execute concurrently with other SRCU read-side + * critical sections that started after call_srcu() was invoked. SRCU + * read-side critical sections are delimited by srcu_read_lock() and + * srcu_read_unlock(), and may be nested. + * + * The callback will be invoked from process context, but must nevertheless + * be fast and must not block. + */ void call_srcu(struct srcu_struct *sp, struct rcu_head *rhp, rcu_callback_t func) { @@ -953,13 +1014,16 @@ void srcu_barrier(struct srcu_struct *sp) */ for_each_possible_cpu(cpu) { sdp = per_cpu_ptr(sp->sda, cpu); - spin_lock_irq(&sdp->lock); + raw_spin_lock_irq_rcu_node(sdp); atomic_inc(&sp->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, 0)) + &sdp->srcu_barrier_head, 0)) { + debug_rcu_head_unqueue(&sdp->srcu_barrier_head); atomic_dec(&sp->srcu_barrier_cpu_cnt); - spin_unlock_irq(&sdp->lock); + } + raw_spin_unlock_irq_rcu_node(sdp); } /* Remove the initial count, at which point reaching zero can happen. */ @@ -1008,17 +1072,17 @@ static void srcu_advance_state(struct srcu_struct *sp) */ idx = rcu_seq_state(smp_load_acquire(&sp->srcu_gp_seq)); /* ^^^ */ if (idx == SRCU_STATE_IDLE) { - spin_lock_irq(&sp->gp_lock); + raw_spin_lock_irq_rcu_node(sp); if (ULONG_CMP_GE(sp->srcu_gp_seq, sp->srcu_gp_seq_needed)) { WARN_ON_ONCE(rcu_seq_state(sp->srcu_gp_seq)); - spin_unlock_irq(&sp->gp_lock); + raw_spin_unlock_irq_rcu_node(sp); mutex_unlock(&sp->srcu_gp_mutex); return; } idx = rcu_seq_state(READ_ONCE(sp->srcu_gp_seq)); if (idx == SRCU_STATE_IDLE) srcu_gp_start(sp); - spin_unlock_irq(&sp->gp_lock); + raw_spin_unlock_irq_rcu_node(sp); if (idx != SRCU_STATE_IDLE) { mutex_unlock(&sp->srcu_gp_mutex); return; /* Someone else started the grace period. */ @@ -1067,22 +1131,22 @@ static void srcu_invoke_callbacks(struct work_struct *work) sdp = container_of(work, struct srcu_data, work.work); sp = sdp->sp; rcu_cblist_init(&ready_cbs); - spin_lock_irq(&sdp->lock); - smp_mb(); /* Old grace periods before callback invocation! */ + raw_spin_lock_irq_rcu_node(sdp); rcu_segcblist_advance(&sdp->srcu_cblist, rcu_seq_current(&sp->srcu_gp_seq)); if (sdp->srcu_cblist_invoking || !rcu_segcblist_ready_cbs(&sdp->srcu_cblist)) { - spin_unlock_irq(&sdp->lock); + raw_spin_unlock_irq_rcu_node(sdp); return; /* Someone else on the job or nothing to do. */ } /* 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); - spin_unlock_irq(&sdp->lock); + raw_spin_unlock_irq_rcu_node(sdp); rhp = rcu_cblist_dequeue(&ready_cbs); for (; rhp != NULL; rhp = rcu_cblist_dequeue(&ready_cbs)) { + debug_rcu_head_unqueue(rhp); local_bh_disable(); rhp->func(rhp); local_bh_enable(); @@ -1092,13 +1156,13 @@ static void srcu_invoke_callbacks(struct work_struct *work) * Update counts, accelerate new callbacks, and if needed, * schedule another round of callback invocation. */ - spin_lock_irq(&sdp->lock); + raw_spin_lock_irq_rcu_node(sdp); rcu_segcblist_insert_count(&sdp->srcu_cblist, &ready_cbs); (void)rcu_segcblist_accelerate(&sdp->srcu_cblist, rcu_seq_snap(&sp->srcu_gp_seq)); sdp->srcu_cblist_invoking = false; more = rcu_segcblist_ready_cbs(&sdp->srcu_cblist); - spin_unlock_irq(&sdp->lock); + raw_spin_unlock_irq_rcu_node(sdp); if (more) srcu_schedule_cbs_sdp(sdp, 0); } @@ -1111,7 +1175,7 @@ static void srcu_reschedule(struct srcu_struct *sp, unsigned long delay) { bool pushgp = true; - spin_lock_irq(&sp->gp_lock); + raw_spin_lock_irq_rcu_node(sp); if (ULONG_CMP_GE(sp->srcu_gp_seq, sp->srcu_gp_seq_needed)) { if (!WARN_ON_ONCE(rcu_seq_state(sp->srcu_gp_seq))) { /* All requests fulfilled, time to go idle. */ @@ -1121,7 +1185,7 @@ static void srcu_reschedule(struct srcu_struct *sp, unsigned long delay) /* Outstanding request and no GP. Start one. */ srcu_gp_start(sp); } - spin_unlock_irq(&sp->gp_lock); + raw_spin_unlock_irq_rcu_node(sp); if (pushgp) queue_delayed_work(system_power_efficient_wq, &sp->work, delay); @@ -1152,3 +1216,12 @@ void srcutorture_get_gp_data(enum rcutorture_type test_type, *gpnum = rcu_seq_ctr(sp->srcu_gp_seq_needed); } EXPORT_SYMBOL_GPL(srcutorture_get_gp_data); + +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); + return 0; +} +early_initcall(srcu_bootup_announce); diff --git a/kernel/rcu/tiny.c b/kernel/rcu/tiny.c index e5385731e391..f8488965250f 100644 --- a/kernel/rcu/tiny.c +++ b/kernel/rcu/tiny.c @@ -35,15 +35,26 @@ #include <linux/time.h> #include <linux/cpu.h> #include <linux/prefetch.h> -#include <linux/trace_events.h> #include "rcu.h" -/* Forward declarations for tiny_plugin.h. */ -struct rcu_ctrlblk; -static void __call_rcu(struct rcu_head *head, - rcu_callback_t func, - struct rcu_ctrlblk *rcp); +/* Global control variables for rcupdate callback mechanism. */ +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. */ +}; + +/* Definition for rcupdate control block. */ +static struct rcu_ctrlblk rcu_sched_ctrlblk = { + .donetail = &rcu_sched_ctrlblk.rcucblist, + .curtail = &rcu_sched_ctrlblk.rcucblist, +}; + +static struct rcu_ctrlblk rcu_bh_ctrlblk = { + .donetail = &rcu_bh_ctrlblk.rcucblist, + .curtail = &rcu_bh_ctrlblk.rcucblist, +}; #include "tiny_plugin.h" @@ -59,19 +70,6 @@ void rcu_barrier_sched(void) } EXPORT_SYMBOL(rcu_barrier_sched); -#if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_RCU_TRACE) - -/* - * Test whether RCU thinks that the current CPU is idle. - */ -bool notrace __rcu_is_watching(void) -{ - return true; -} -EXPORT_SYMBOL(__rcu_is_watching); - -#endif /* defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_RCU_TRACE) */ - /* * Helper function for rcu_sched_qs() and rcu_bh_qs(). * Also irqs are disabled to avoid confusion due to interrupt handlers @@ -79,7 +77,6 @@ EXPORT_SYMBOL(__rcu_is_watching); */ static int rcu_qsctr_help(struct rcu_ctrlblk *rcp) { - RCU_TRACE(reset_cpu_stall_ticks(rcp);) if (rcp->donetail != rcp->curtail) { rcp->donetail = rcp->curtail; return 1; @@ -125,7 +122,6 @@ void rcu_bh_qs(void) */ void rcu_check_callbacks(int user) { - RCU_TRACE(check_cpu_stalls();) if (user) rcu_sched_qs(); else if (!in_softirq()) @@ -140,10 +136,8 @@ void rcu_check_callbacks(int user) */ static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp) { - const char *rn = NULL; struct rcu_head *next, *list; unsigned long flags; - RCU_TRACE(int cb_count = 0;) /* Move the ready-to-invoke callbacks to a local list. */ local_irq_save(flags); @@ -152,7 +146,6 @@ static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp) local_irq_restore(flags); return; } - RCU_TRACE(trace_rcu_batch_start(rcp->name, 0, rcp->qlen, -1);) list = rcp->rcucblist; rcp->rcucblist = *rcp->donetail; *rcp->donetail = NULL; @@ -162,22 +155,15 @@ static void __rcu_process_callbacks(struct rcu_ctrlblk *rcp) local_irq_restore(flags); /* Invoke the callbacks on the local list. */ - RCU_TRACE(rn = rcp->name;) while (list) { next = list->next; prefetch(next); debug_rcu_head_unqueue(list); local_bh_disable(); - __rcu_reclaim(rn, list); + __rcu_reclaim("", list); local_bh_enable(); list = next; - RCU_TRACE(cb_count++;) } - RCU_TRACE(rcu_trace_sub_qlen(rcp, cb_count);) - RCU_TRACE(trace_rcu_batch_end(rcp->name, - cb_count, 0, need_resched(), - is_idle_task(current), - false)); } static __latent_entropy void rcu_process_callbacks(struct softirq_action *unused) @@ -221,7 +207,6 @@ static void __call_rcu(struct rcu_head *head, local_irq_save(flags); *rcp->curtail = head; rcp->curtail = &head->next; - RCU_TRACE(rcp->qlen++;) local_irq_restore(flags); if (unlikely(is_idle_task(current))) { @@ -254,8 +239,5 @@ EXPORT_SYMBOL_GPL(call_rcu_bh); void __init rcu_init(void) { open_softirq(RCU_SOFTIRQ, rcu_process_callbacks); - RCU_TRACE(reset_cpu_stall_ticks(&rcu_sched_ctrlblk);) - RCU_TRACE(reset_cpu_stall_ticks(&rcu_bh_ctrlblk);) - rcu_early_boot_tests(); } diff --git a/kernel/rcu/tiny_plugin.h b/kernel/rcu/tiny_plugin.h index 371034e77f87..f0a01b2a3062 100644 --- a/kernel/rcu/tiny_plugin.h +++ b/kernel/rcu/tiny_plugin.h @@ -22,36 +22,6 @@ * Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com> */ -#include <linux/kthread.h> -#include <linux/init.h> -#include <linux/debugfs.h> -#include <linux/seq_file.h> - -/* Global control variables for rcupdate callback mechanism. */ -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. */ - RCU_TRACE(long qlen); /* Number of pending CBs. */ - RCU_TRACE(unsigned long gp_start); /* Start time for stalls. */ - RCU_TRACE(unsigned long ticks_this_gp); /* Statistic for stalls. */ - RCU_TRACE(unsigned long jiffies_stall); /* Jiffies at next stall. */ - RCU_TRACE(const char *name); /* Name of RCU type. */ -}; - -/* Definition for rcupdate control block. */ -static struct rcu_ctrlblk rcu_sched_ctrlblk = { - .donetail = &rcu_sched_ctrlblk.rcucblist, - .curtail = &rcu_sched_ctrlblk.rcucblist, - RCU_TRACE(.name = "rcu_sched") -}; - -static struct rcu_ctrlblk rcu_bh_ctrlblk = { - .donetail = &rcu_bh_ctrlblk.rcucblist, - .curtail = &rcu_bh_ctrlblk.rcucblist, - RCU_TRACE(.name = "rcu_bh") -}; - #if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_SRCU) #include <linux/kernel_stat.h> @@ -75,96 +45,3 @@ void __init rcu_scheduler_starting(void) } #endif /* #if defined(CONFIG_DEBUG_LOCK_ALLOC) || defined(CONFIG_SRCU) */ - -#ifdef CONFIG_RCU_TRACE - -static void rcu_trace_sub_qlen(struct rcu_ctrlblk *rcp, int n) -{ - unsigned long flags; - - local_irq_save(flags); - rcp->qlen -= n; - local_irq_restore(flags); -} - -/* - * Dump statistics for TINY_RCU, such as they are. - */ -static int show_tiny_stats(struct seq_file *m, void *unused) -{ - seq_printf(m, "rcu_sched: qlen: %ld\n", rcu_sched_ctrlblk.qlen); - seq_printf(m, "rcu_bh: qlen: %ld\n", rcu_bh_ctrlblk.qlen); - return 0; -} - -static int show_tiny_stats_open(struct inode *inode, struct file *file) -{ - return single_open(file, show_tiny_stats, NULL); -} - -static const struct file_operations show_tiny_stats_fops = { - .owner = THIS_MODULE, - .open = show_tiny_stats_open, - .read = seq_read, - .llseek = seq_lseek, - .release = single_release, -}; - -static struct dentry *rcudir; - -static int __init rcutiny_trace_init(void) -{ - struct dentry *retval; - - rcudir = debugfs_create_dir("rcu", NULL); - if (!rcudir) - goto free_out; - retval = debugfs_create_file("rcudata", 0444, rcudir, - NULL, &show_tiny_stats_fops); - if (!retval) - goto free_out; - return 0; -free_out: - debugfs_remove_recursive(rcudir); - return 1; -} -device_initcall(rcutiny_trace_init); - -static void check_cpu_stall(struct rcu_ctrlblk *rcp) -{ - unsigned long j; - unsigned long js; - - if (rcu_cpu_stall_suppress) - return; - rcp->ticks_this_gp++; - j = jiffies; - js = READ_ONCE(rcp->jiffies_stall); - if (rcp->rcucblist && ULONG_CMP_GE(j, js)) { - pr_err("INFO: %s stall on CPU (%lu ticks this GP) idle=%llx (t=%lu jiffies q=%ld)\n", - rcp->name, rcp->ticks_this_gp, DYNTICK_TASK_EXIT_IDLE, - jiffies - rcp->gp_start, rcp->qlen); - dump_stack(); - WRITE_ONCE(rcp->jiffies_stall, - jiffies + 3 * rcu_jiffies_till_stall_check() + 3); - } else if (ULONG_CMP_GE(j, js)) { - WRITE_ONCE(rcp->jiffies_stall, - jiffies + rcu_jiffies_till_stall_check()); - } -} - -static void reset_cpu_stall_ticks(struct rcu_ctrlblk *rcp) -{ - rcp->ticks_this_gp = 0; - rcp->gp_start = jiffies; - WRITE_ONCE(rcp->jiffies_stall, - jiffies + rcu_jiffies_till_stall_check()); -} - -static void check_cpu_stalls(void) -{ - RCU_TRACE(check_cpu_stall(&rcu_bh_ctrlblk);) - RCU_TRACE(check_cpu_stall(&rcu_sched_ctrlblk);) -} - -#endif /* #ifdef CONFIG_RCU_TRACE */ diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index e354e475e645..51d4c3acf32d 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -168,35 +168,17 @@ static void rcu_report_exp_rdp(struct rcu_state *rsp, static void sync_sched_exp_online_cleanup(int cpu); /* rcuc/rcub kthread realtime priority */ -#ifdef CONFIG_RCU_KTHREAD_PRIO -static int kthread_prio = CONFIG_RCU_KTHREAD_PRIO; -#else /* #ifdef CONFIG_RCU_KTHREAD_PRIO */ static int kthread_prio = IS_ENABLED(CONFIG_RCU_BOOST) ? 1 : 0; -#endif /* #else #ifdef CONFIG_RCU_KTHREAD_PRIO */ module_param(kthread_prio, int, 0644); /* Delay in jiffies for grace-period initialization delays, debug only. */ -#ifdef CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT -static int gp_preinit_delay = CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT_DELAY; -module_param(gp_preinit_delay, int, 0644); -#else /* #ifdef CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT */ -static const int gp_preinit_delay; -#endif /* #else #ifdef CONFIG_RCU_TORTURE_TEST_SLOW_PREINIT */ - -#ifdef CONFIG_RCU_TORTURE_TEST_SLOW_INIT -static int gp_init_delay = CONFIG_RCU_TORTURE_TEST_SLOW_INIT_DELAY; -module_param(gp_init_delay, int, 0644); -#else /* #ifdef CONFIG_RCU_TORTURE_TEST_SLOW_INIT */ -static const int gp_init_delay; -#endif /* #else #ifdef CONFIG_RCU_TORTURE_TEST_SLOW_INIT */ - -#ifdef CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP -static int gp_cleanup_delay = CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP_DELAY; -module_param(gp_cleanup_delay, int, 0644); -#else /* #ifdef CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP */ -static const int gp_cleanup_delay; -#endif /* #else #ifdef CONFIG_RCU_TORTURE_TEST_SLOW_CLEANUP */ +static int gp_preinit_delay; +module_param(gp_preinit_delay, int, 0444); +static int gp_init_delay; +module_param(gp_init_delay, int, 0444); +static int gp_cleanup_delay; +module_param(gp_cleanup_delay, int, 0444); /* * Number of grace periods between delays, normalized by the duration of @@ -250,6 +232,7 @@ static int rcu_gp_in_progress(struct rcu_state *rsp) */ void rcu_sched_qs(void) { + RCU_LOCKDEP_WARN(preemptible(), "rcu_sched_qs() invoked with preemption enabled!!!"); if (!__this_cpu_read(rcu_sched_data.cpu_no_qs.s)) return; trace_rcu_grace_period(TPS("rcu_sched"), @@ -265,6 +248,7 @@ void rcu_sched_qs(void) void rcu_bh_qs(void) { + RCU_LOCKDEP_WARN(preemptible(), "rcu_bh_qs() invoked with preemption enabled!!!"); if (__this_cpu_read(rcu_bh_data.cpu_no_qs.s)) { trace_rcu_grace_period(TPS("rcu_bh"), __this_cpu_read(rcu_bh_data.gpnum), @@ -286,10 +270,6 @@ void rcu_bh_qs(void) static DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = { .dynticks_nesting = DYNTICK_TASK_EXIT_IDLE, .dynticks = ATOMIC_INIT(RCU_DYNTICK_CTRL_CTR), -#ifdef CONFIG_NO_HZ_FULL_SYSIDLE - .dynticks_idle_nesting = DYNTICK_TASK_NEST_VALUE, - .dynticks_idle = ATOMIC_INIT(1), -#endif /* #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */ }; /* @@ -478,7 +458,7 @@ void rcu_note_context_switch(bool preempt) barrier(); /* Avoid RCU read-side critical sections leaking down. */ trace_rcu_utilization(TPS("Start context switch")); rcu_sched_qs(); - rcu_preempt_note_context_switch(); + rcu_preempt_note_context_switch(preempt); /* Load rcu_urgent_qs before other flags. */ if (!smp_load_acquire(this_cpu_ptr(&rcu_dynticks.rcu_urgent_qs))) goto out; @@ -534,9 +514,12 @@ void rcu_all_qs(void) } EXPORT_SYMBOL_GPL(rcu_all_qs); -static long blimit = 10; /* Maximum callbacks per rcu_do_batch. */ -static long qhimark = 10000; /* If this many pending, ignore blimit. */ -static long qlowmark = 100; /* Once only this many pending, use blimit. */ +#define DEFAULT_RCU_BLIMIT 10 /* Maximum callbacks per rcu_do_batch. */ +static long blimit = DEFAULT_RCU_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. */ +static long qlowmark = DEFAULT_RCU_QLOMARK; module_param(blimit, long, 0444); module_param(qhimark, long, 0444); @@ -559,10 +542,7 @@ module_param(jiffies_till_sched_qs, ulong, 0644); static bool rcu_start_gp_advanced(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp); -static void force_qs_rnp(struct rcu_state *rsp, - int (*f)(struct rcu_data *rsp, bool *isidle, - unsigned long *maxj), - bool *isidle, unsigned long *maxj); +static void force_qs_rnp(struct rcu_state *rsp, int (*f)(struct rcu_data *rsp)); static void force_quiescent_state(struct rcu_state *rsp); static int rcu_pending(void); @@ -757,6 +737,7 @@ static int rcu_future_needs_gp(struct rcu_state *rsp) int idx = (READ_ONCE(rnp->completed) + 1) & 0x1; int *fp = &rnp->need_future_gp[idx]; + RCU_LOCKDEP_WARN(!irqs_disabled(), "rcu_future_needs_gp() invoked with irqs enabled!!!"); return READ_ONCE(*fp); } @@ -768,6 +749,7 @@ static int rcu_future_needs_gp(struct rcu_state *rsp) static bool cpu_needs_another_gp(struct rcu_state *rsp, struct rcu_data *rdp) { + RCU_LOCKDEP_WARN(!irqs_disabled(), "cpu_needs_another_gp() invoked with irqs enabled!!!"); if (rcu_gp_in_progress(rsp)) return false; /* No, a grace period is already in progress. */ if (rcu_future_needs_gp(rsp)) @@ -794,6 +776,7 @@ static void rcu_eqs_enter_common(bool user) struct rcu_data *rdp; struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks); + RCU_LOCKDEP_WARN(!irqs_disabled(), "rcu_eqs_enter_common() invoked with irqs enabled!!!"); trace_rcu_dyntick(TPS("Start"), rdtp->dynticks_nesting, 0); if (IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !user && !is_idle_task(current)) { @@ -864,7 +847,6 @@ void rcu_idle_enter(void) local_irq_save(flags); rcu_eqs_enter(false); - rcu_sysidle_enter(0); local_irq_restore(flags); } EXPORT_SYMBOL_GPL(rcu_idle_enter); @@ -914,7 +896,6 @@ void rcu_irq_exit(void) trace_rcu_dyntick(TPS("--="), rdtp->dynticks_nesting, rdtp->dynticks_nesting - 1); rdtp->dynticks_nesting--; } - rcu_sysidle_enter(1); } /* @@ -967,6 +948,7 @@ static void rcu_eqs_exit(bool user) struct rcu_dynticks *rdtp; long long oldval; + RCU_LOCKDEP_WARN(!irqs_disabled(), "rcu_eqs_exit() invoked with irqs enabled!!!"); rdtp = this_cpu_ptr(&rcu_dynticks); oldval = rdtp->dynticks_nesting; WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && oldval < 0); @@ -995,7 +977,6 @@ void rcu_idle_exit(void) local_irq_save(flags); rcu_eqs_exit(false); - rcu_sysidle_exit(0); local_irq_restore(flags); } EXPORT_SYMBOL_GPL(rcu_idle_exit); @@ -1047,7 +1028,6 @@ void rcu_irq_enter(void) trace_rcu_dyntick(TPS("++="), oldval, rdtp->dynticks_nesting); else rcu_eqs_exit_common(oldval, true); - rcu_sysidle_exit(1); } /* @@ -1130,22 +1110,11 @@ void rcu_nmi_exit(void) } /** - * __rcu_is_watching - are RCU read-side critical sections safe? - * - * Return true if RCU is watching the running CPU, which means that - * this CPU can safely enter RCU read-side critical sections. Unlike - * rcu_is_watching(), the caller of __rcu_is_watching() must have at - * least disabled preemption. - */ -bool notrace __rcu_is_watching(void) -{ - return !rcu_dynticks_curr_cpu_in_eqs(); -} - -/** * rcu_is_watching - see if RCU thinks that the current CPU is idle * - * If the current CPU is in its idle loop and is neither in an interrupt + * Return true if RCU is watching the running CPU, which means that this + * CPU can safely enter RCU read-side critical sections. In other words, + * if the current CPU is in its idle loop and is neither in an interrupt * or NMI handler, return true. */ bool notrace rcu_is_watching(void) @@ -1153,7 +1122,7 @@ bool notrace rcu_is_watching(void) bool ret; preempt_disable_notrace(); - ret = __rcu_is_watching(); + ret = !rcu_dynticks_curr_cpu_in_eqs(); preempt_enable_notrace(); return ret; } @@ -1237,11 +1206,9 @@ static int rcu_is_cpu_rrupt_from_idle(void) * credit them with an implicit quiescent state. Return 1 if this CPU * is in dynticks idle mode, which is an extended quiescent state. */ -static int dyntick_save_progress_counter(struct rcu_data *rdp, - bool *isidle, unsigned long *maxj) +static int dyntick_save_progress_counter(struct rcu_data *rdp) { rdp->dynticks_snap = rcu_dynticks_snap(rdp->dynticks); - rcu_sysidle_check_cpu(rdp, isidle, maxj); if (rcu_dynticks_in_eqs(rdp->dynticks_snap)) { trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, TPS("dti")); if (ULONG_CMP_LT(READ_ONCE(rdp->gpnum) + ULONG_MAX / 4, @@ -1258,8 +1225,7 @@ static int dyntick_save_progress_counter(struct rcu_data *rdp, * idle state since the last call to dyntick_save_progress_counter() * for this same CPU, or by virtue of having been offline. */ -static int rcu_implicit_dynticks_qs(struct rcu_data *rdp, - bool *isidle, unsigned long *maxj) +static int rcu_implicit_dynticks_qs(struct rcu_data *rdp) { unsigned long jtsq; bool *rnhqp; @@ -1674,6 +1640,8 @@ void rcu_cpu_stall_reset(void) static unsigned long rcu_cbs_completed(struct rcu_state *rsp, struct rcu_node *rnp) { + lockdep_assert_held(&rnp->lock); + /* * If RCU is idle, we just wait for the next grace period. * But we can only be sure that RCU is idle if we are looking @@ -1719,6 +1687,8 @@ rcu_start_future_gp(struct rcu_node *rnp, struct rcu_data *rdp, bool ret = false; struct rcu_node *rnp_root = rcu_get_root(rdp->rsp); + lockdep_assert_held(&rnp->lock); + /* * Pick up grace-period number for new callbacks. If this * grace period is already marked as needed, return to the caller. @@ -1845,6 +1815,8 @@ static bool rcu_accelerate_cbs(struct rcu_state *rsp, struct rcu_node *rnp, { bool ret = false; + lockdep_assert_held(&rnp->lock); + /* If no pending (not yet ready to invoke) callbacks, nothing to do. */ if (!rcu_segcblist_pend_cbs(&rdp->cblist)) return false; @@ -1883,6 +1855,8 @@ static bool rcu_accelerate_cbs(struct rcu_state *rsp, struct rcu_node *rnp, static bool rcu_advance_cbs(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp) { + lockdep_assert_held(&rnp->lock); + /* If no pending (not yet ready to invoke) callbacks, nothing to do. */ if (!rcu_segcblist_pend_cbs(&rdp->cblist)) return false; @@ -1909,6 +1883,8 @@ static bool __note_gp_changes(struct rcu_state *rsp, struct rcu_node *rnp, bool ret; bool need_gp; + lockdep_assert_held(&rnp->lock); + /* Handle the ends of any preceding grace periods first. */ if (rdp->completed == rnp->completed && !unlikely(READ_ONCE(rdp->gpwrap))) { @@ -2115,25 +2091,16 @@ static bool rcu_gp_fqs_check_wake(struct rcu_state *rsp, int *gfp) */ static void rcu_gp_fqs(struct rcu_state *rsp, bool first_time) { - bool isidle = false; - unsigned long maxj; struct rcu_node *rnp = rcu_get_root(rsp); WRITE_ONCE(rsp->gp_activity, jiffies); rsp->n_force_qs++; if (first_time) { /* Collect dyntick-idle snapshots. */ - if (is_sysidle_rcu_state(rsp)) { - isidle = true; - maxj = jiffies - ULONG_MAX / 4; - } - force_qs_rnp(rsp, dyntick_save_progress_counter, - &isidle, &maxj); - rcu_sysidle_report_gp(rsp, isidle, maxj); + force_qs_rnp(rsp, dyntick_save_progress_counter); } else { /* Handle dyntick-idle and offline CPUs. */ - isidle = true; - force_qs_rnp(rsp, rcu_implicit_dynticks_qs, &isidle, &maxj); + force_qs_rnp(rsp, rcu_implicit_dynticks_qs); } /* Clear flag to prevent immediate re-entry. */ if (READ_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) { @@ -2341,6 +2308,7 @@ static bool rcu_start_gp_advanced(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp) { + lockdep_assert_held(&rnp->lock); if (!rsp->gp_kthread || !cpu_needs_another_gp(rsp, rdp)) { /* * Either we have not yet spawned the grace-period @@ -2402,6 +2370,7 @@ static bool rcu_start_gp(struct rcu_state *rsp) static void rcu_report_qs_rsp(struct rcu_state *rsp, unsigned long flags) __releases(rcu_get_root(rsp)->lock) { + lockdep_assert_held(&rcu_get_root(rsp)->lock); WARN_ON_ONCE(!rcu_gp_in_progress(rsp)); WRITE_ONCE(rsp->gp_flags, READ_ONCE(rsp->gp_flags) | RCU_GP_FLAG_FQS); raw_spin_unlock_irqrestore_rcu_node(rcu_get_root(rsp), flags); @@ -2426,6 +2395,8 @@ rcu_report_qs_rnp(unsigned long mask, struct rcu_state *rsp, unsigned long oldmask = 0; struct rcu_node *rnp_c; + lockdep_assert_held(&rnp->lock); + /* Walk up the rcu_node hierarchy. */ for (;;) { if (!(rnp->qsmask & mask) || rnp->gpnum != gps) { @@ -2486,6 +2457,7 @@ static void rcu_report_unblock_qs_rnp(struct rcu_state *rsp, unsigned long mask; struct rcu_node *rnp_p; + lockdep_assert_held(&rnp->lock); if (rcu_state_p == &rcu_sched_state || rsp != rcu_state_p || rnp->qsmask != 0 || rcu_preempt_blocked_readers_cgp(rnp)) { raw_spin_unlock_irqrestore_rcu_node(rnp, flags); @@ -2599,6 +2571,8 @@ static void rcu_send_cbs_to_orphanage(int cpu, struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp) { + lockdep_assert_held(&rsp->orphan_lock); + /* No-CBs CPUs do not have orphanable callbacks. */ if (!IS_ENABLED(CONFIG_HOTPLUG_CPU) || rcu_is_nocb_cpu(rdp->cpu)) return; @@ -2639,6 +2613,8 @@ static void rcu_adopt_orphan_cbs(struct rcu_state *rsp, unsigned long flags) { struct rcu_data *rdp = raw_cpu_ptr(rsp->rda); + lockdep_assert_held(&rsp->orphan_lock); + /* No-CBs CPUs are handled specially. */ if (!IS_ENABLED(CONFIG_HOTPLUG_CPU) || rcu_nocb_adopt_orphan_cbs(rsp, rdp, flags)) @@ -2705,6 +2681,7 @@ static void rcu_cleanup_dead_rnp(struct rcu_node *rnp_leaf) long mask; struct rcu_node *rnp = rnp_leaf; + lockdep_assert_held(&rnp->lock); if (!IS_ENABLED(CONFIG_HOTPLUG_CPU) || rnp->qsmaskinit || rcu_preempt_has_tasks(rnp)) return; @@ -2895,10 +2872,7 @@ void rcu_check_callbacks(int user) * * The caller must have suppressed start of new grace periods. */ -static void force_qs_rnp(struct rcu_state *rsp, - int (*f)(struct rcu_data *rsp, bool *isidle, - unsigned long *maxj), - bool *isidle, unsigned long *maxj) +static void force_qs_rnp(struct rcu_state *rsp, int (*f)(struct rcu_data *rsp)) { int cpu; unsigned long flags; @@ -2937,7 +2911,7 @@ static void force_qs_rnp(struct rcu_state *rsp, for_each_leaf_node_possible_cpu(rnp, cpu) { unsigned long bit = leaf_node_cpu_bit(rnp, cpu); if ((rnp->qsmask & bit) != 0) { - if (f(per_cpu_ptr(rsp->rda, cpu), isidle, maxj)) + if (f(per_cpu_ptr(rsp->rda, cpu))) mask |= bit; } } @@ -3143,9 +3117,14 @@ __call_rcu(struct rcu_head *head, rcu_callback_t func, WARN_ON_ONCE((unsigned long)head & (sizeof(void *) - 1)); if (debug_rcu_head_queue(head)) { - /* Probable double call_rcu(), so leak the callback. */ + /* + * 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(). + */ + WARN_ONCE(1, "__call_rcu(): Double-freed CB %p->%pF()!!!\n", + head, head->func); WRITE_ONCE(head->func, rcu_leak_callback); - WARN_ONCE(1, "__call_rcu(): Leaked duplicate callback\n"); return; } head->func = func; @@ -3194,8 +3173,24 @@ __call_rcu(struct rcu_head *head, rcu_callback_t func, local_irq_restore(flags); } -/* - * Queue an RCU-sched callback for invocation after a grace period. +/** + * call_rcu_sched() - Queue an RCU for invocation after sched 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 currently executing RCU + * read-side critical sections have completed. call_rcu_sched() assumes + * that the read-side critical sections end on enabling of preemption + * or on voluntary preemption. + * RCU read-side critical sections are delimited by : + * - rcu_read_lock_sched() and rcu_read_unlock_sched(), OR + * - anything that disables preemption. + * + * These may be nested. + * + * See the description of call_rcu() for more detailed information on + * memory ordering guarantees. */ void call_rcu_sched(struct rcu_head *head, rcu_callback_t func) { @@ -3203,8 +3198,26 @@ void call_rcu_sched(struct rcu_head *head, rcu_callback_t func) } EXPORT_SYMBOL_GPL(call_rcu_sched); -/* - * Queue an RCU callback for invocation after a quicker grace period. +/** + * call_rcu_bh() - Queue an RCU for invocation after a quicker 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 currently executing RCU + * read-side critical sections have completed. call_rcu_bh() assumes + * that the read-side critical sections end on completion of a softirq + * handler. This means that read-side critical sections in process + * context must not be interrupted by softirqs. This interface is to be + * used when most of the read-side critical sections are in softirq context. + * RCU read-side critical sections are delimited by : + * - rcu_read_lock() and rcu_read_unlock(), if in interrupt context. + * OR + * - rcu_read_lock_bh() and rcu_read_unlock_bh(), if in process context. + * These may be nested. + * + * See the description of call_rcu() for more detailed information on + * memory ordering guarantees. */ void call_rcu_bh(struct rcu_head *head, rcu_callback_t func) { @@ -3280,12 +3293,6 @@ static inline int rcu_blocking_is_gp(void) * to have executed a full memory barrier during the execution of * synchronize_sched() -- even if CPU A and CPU B are the same CPU (but * again only if the system has more than one CPU). - * - * This primitive provides the guarantees made by the (now removed) - * synchronize_kernel() API. In contrast, synchronize_rcu() only - * guarantees that rcu_read_lock() sections will have completed. - * In "classic RCU", these two guarantees happen to be one and - * the same, but can differ in realtime RCU implementations. */ void synchronize_sched(void) { @@ -3578,8 +3585,14 @@ static void rcu_barrier_func(void *type) struct rcu_data *rdp = raw_cpu_ptr(rsp->rda); _rcu_barrier_trace(rsp, "IRQ", -1, rsp->barrier_sequence); - atomic_inc(&rsp->barrier_cpu_count); - rsp->call(&rdp->barrier_head, rcu_barrier_callback); + rdp->barrier_head.func = rcu_barrier_callback; + debug_rcu_head_queue(&rdp->barrier_head); + if (rcu_segcblist_entrain(&rdp->cblist, &rdp->barrier_head, 0)) { + atomic_inc(&rsp->barrier_cpu_count); + } else { + debug_rcu_head_unqueue(&rdp->barrier_head); + _rcu_barrier_trace(rsp, "IRQNQ", -1, rsp->barrier_sequence); + } } /* @@ -3698,6 +3711,7 @@ static void rcu_init_new_rnp(struct rcu_node *rnp_leaf) long mask; struct rcu_node *rnp = rnp_leaf; + lockdep_assert_held(&rnp->lock); for (;;) { mask = rnp->grpmask; rnp = rnp->parent; @@ -3753,7 +3767,6 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp) !init_nocb_callback_list(rdp)) rcu_segcblist_init(&rdp->cblist); /* Re-enable callbacks. */ rdp->dynticks->dynticks_nesting = DYNTICK_TASK_EXIT_IDLE; - rcu_sysidle_init_percpu_data(rdp->dynticks); rcu_dynticks_eqs_online(); raw_spin_unlock_rcu_node(rnp); /* irqs remain disabled. */ diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h index ba38262c3554..9af0f31d6847 100644 --- a/kernel/rcu/tree.h +++ b/kernel/rcu/tree.h @@ -45,14 +45,6 @@ struct rcu_dynticks { bool rcu_need_heavy_qs; /* GP old, need heavy quiescent state. */ unsigned long rcu_qs_ctr; /* Light universal quiescent state ctr. */ bool rcu_urgent_qs; /* GP old need light quiescent state. */ -#ifdef CONFIG_NO_HZ_FULL_SYSIDLE - long long dynticks_idle_nesting; - /* irq/process nesting level from idle. */ - atomic_t dynticks_idle; /* Even value for idle, else odd. */ - /* "Idle" excludes userspace execution. */ - unsigned long dynticks_idle_jiffies; - /* End of last non-NMI non-idle period. */ -#endif /* #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */ #ifdef CONFIG_RCU_FAST_NO_HZ bool all_lazy; /* Are all CPU's CBs lazy? */ unsigned long nonlazy_posted; @@ -160,19 +152,6 @@ struct rcu_node { /* Number of tasks boosted for expedited GP. */ unsigned long n_normal_boosts; /* Number of tasks boosted for normal GP. */ - unsigned long n_balk_blkd_tasks; - /* Refused to boost: no blocked tasks. */ - unsigned long n_balk_exp_gp_tasks; - /* Refused to boost: nothing blocking GP. */ - unsigned long n_balk_boost_tasks; - /* Refused to boost: already boosting. */ - unsigned long n_balk_notblocked; - /* Refused to boost: RCU RS CS still running. */ - unsigned long n_balk_notyet; - /* Refused to boost: not yet time. */ - unsigned long n_balk_nos; - /* Refused to boost: not sure why, though. */ - /* This can happen due to race conditions. */ #ifdef CONFIG_RCU_NOCB_CPU struct swait_queue_head nocb_gp_wq[2]; /* Place for rcu_nocb_kthread() to wait GP. */ @@ -312,9 +291,9 @@ struct rcu_data { }; /* Values for nocb_defer_wakeup field in struct rcu_data. */ -#define RCU_NOGP_WAKE_NOT 0 -#define RCU_NOGP_WAKE 1 -#define RCU_NOGP_WAKE_FORCE 2 +#define RCU_NOCB_WAKE_NOT 0 +#define RCU_NOCB_WAKE 1 +#define RCU_NOCB_WAKE_FORCE 2 #define RCU_JIFFIES_TILL_FORCE_QS (1 + (HZ > 250) + (HZ > 500)) /* For jiffies_till_first_fqs and */ @@ -477,7 +456,7 @@ DECLARE_PER_CPU(char, rcu_cpu_has_work); /* Forward declarations for rcutree_plugin.h */ static void rcu_bootup_announce(void); -static void rcu_preempt_note_context_switch(void); +static void rcu_preempt_note_context_switch(bool preempt); static int rcu_preempt_blocked_readers_cgp(struct rcu_node *rnp); #ifdef CONFIG_HOTPLUG_CPU static bool rcu_preempt_has_tasks(struct rcu_node *rnp); @@ -529,15 +508,7 @@ static void __init rcu_organize_nocb_kthreads(struct rcu_state *rsp); #endif /* #ifdef CONFIG_RCU_NOCB_CPU */ static void __maybe_unused rcu_kick_nohz_cpu(int cpu); static bool init_nocb_callback_list(struct rcu_data *rdp); -static void rcu_sysidle_enter(int irq); -static void rcu_sysidle_exit(int irq); -static void rcu_sysidle_check_cpu(struct rcu_data *rdp, bool *isidle, - unsigned long *maxj); -static bool is_sysidle_rcu_state(struct rcu_state *rsp); -static void rcu_sysidle_report_gp(struct rcu_state *rsp, int isidle, - unsigned long maxj); static void rcu_bind_gp_kthread(void); -static void rcu_sysidle_init_percpu_data(struct rcu_dynticks *rdtp); static bool rcu_nohz_full_cpu(struct rcu_state *rsp); static void rcu_dynticks_task_enter(void); static void rcu_dynticks_task_exit(void); @@ -551,75 +522,3 @@ void srcu_offline_cpu(unsigned int cpu) { } #endif /* #else #ifdef CONFIG_SRCU */ #endif /* #ifndef RCU_TREE_NONCORE */ - -#ifdef CONFIG_RCU_TRACE -/* Read out queue lengths for tracing. */ -static inline void rcu_nocb_q_lengths(struct rcu_data *rdp, long *ql, long *qll) -{ -#ifdef CONFIG_RCU_NOCB_CPU - *ql = atomic_long_read(&rdp->nocb_q_count); - *qll = atomic_long_read(&rdp->nocb_q_count_lazy); -#else /* #ifdef CONFIG_RCU_NOCB_CPU */ - *ql = 0; - *qll = 0; -#endif /* #else #ifdef CONFIG_RCU_NOCB_CPU */ -} -#endif /* #ifdef CONFIG_RCU_TRACE */ - -/* - * Wrappers for the rcu_node::lock acquire and release. - * - * Because the rcu_nodes form a tree, the tree traversal locking will observe - * different lock values, this in turn means that an UNLOCK of one level - * followed by a LOCK of another level does not imply a full memory barrier; - * and most importantly transitivity is lost. - * - * In order to restore full ordering between tree levels, augment the regular - * lock acquire functions with smp_mb__after_unlock_lock(). - * - * As ->lock of struct rcu_node is a __private field, therefore one should use - * these wrappers rather than directly call raw_spin_{lock,unlock}* on ->lock. - */ -static inline void raw_spin_lock_rcu_node(struct rcu_node *rnp) -{ - raw_spin_lock(&ACCESS_PRIVATE(rnp, lock)); - smp_mb__after_unlock_lock(); -} - -static inline void raw_spin_unlock_rcu_node(struct rcu_node *rnp) -{ - raw_spin_unlock(&ACCESS_PRIVATE(rnp, lock)); -} - -static inline void raw_spin_lock_irq_rcu_node(struct rcu_node *rnp) -{ - raw_spin_lock_irq(&ACCESS_PRIVATE(rnp, lock)); - smp_mb__after_unlock_lock(); -} - -static inline void raw_spin_unlock_irq_rcu_node(struct rcu_node *rnp) -{ - raw_spin_unlock_irq(&ACCESS_PRIVATE(rnp, lock)); -} - -#define raw_spin_lock_irqsave_rcu_node(rnp, flags) \ -do { \ - typecheck(unsigned long, flags); \ - raw_spin_lock_irqsave(&ACCESS_PRIVATE(rnp, lock), flags); \ - smp_mb__after_unlock_lock(); \ -} while (0) - -#define raw_spin_unlock_irqrestore_rcu_node(rnp, flags) \ -do { \ - typecheck(unsigned long, flags); \ - raw_spin_unlock_irqrestore(&ACCESS_PRIVATE(rnp, lock), flags); \ -} while (0) - -static inline bool raw_spin_trylock_rcu_node(struct rcu_node *rnp) -{ - bool locked = raw_spin_trylock(&ACCESS_PRIVATE(rnp, lock)); - - if (locked) - smp_mb__after_unlock_lock(); - return locked; -} diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h index e513b4ab1197..dd21ca47e4b4 100644 --- a/kernel/rcu/tree_exp.h +++ b/kernel/rcu/tree_exp.h @@ -147,7 +147,7 @@ static void __maybe_unused sync_exp_reset_tree(struct rcu_state *rsp) * * Caller must hold the rcu_state's exp_mutex. */ -static int sync_rcu_preempt_exp_done(struct rcu_node *rnp) +static bool sync_rcu_preempt_exp_done(struct rcu_node *rnp) { return rnp->exp_tasks == NULL && READ_ONCE(rnp->expmask) == 0; diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index c9a48657512a..908b309d60d7 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -70,7 +70,7 @@ static bool __read_mostly rcu_nocb_poll; /* Offload kthread are to poll. */ static void __init rcu_bootup_announce_oddness(void) { if (IS_ENABLED(CONFIG_RCU_TRACE)) - pr_info("\tRCU debugfs-based tracing is enabled.\n"); + pr_info("\tRCU event tracing is enabled.\n"); if ((IS_ENABLED(CONFIG_64BIT) && RCU_FANOUT != 64) || (!IS_ENABLED(CONFIG_64BIT) && RCU_FANOUT != 32)) pr_info("\tCONFIG_RCU_FANOUT set to non-default value of %d\n", @@ -90,8 +90,32 @@ static void __init rcu_bootup_announce_oddness(void) pr_info("\tBoot-time adjustment of leaf fanout to %d.\n", rcu_fanout_leaf); if (nr_cpu_ids != NR_CPUS) pr_info("\tRCU restricting CPUs from NR_CPUS=%d to nr_cpu_ids=%d.\n", NR_CPUS, nr_cpu_ids); - if (IS_ENABLED(CONFIG_RCU_BOOST)) - pr_info("\tRCU kthread priority: %d.\n", kthread_prio); +#ifdef CONFIG_RCU_BOOST + pr_info("\tRCU priority boosting: priority %d delay %d ms.\n", kthread_prio, CONFIG_RCU_BOOST_DELAY); +#endif + if (blimit != DEFAULT_RCU_BLIMIT) + pr_info("\tBoot-time adjustment of callback invocation limit to %ld.\n", blimit); + if (qhimark != DEFAULT_RCU_QHIMARK) + 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 (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) + pr_info("\tBoot-time adjustment of subsequent FQS scan delay to %ld jiffies.\n", jiffies_till_next_fqs); + 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"); + 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); + if (IS_ENABLED(CONFIG_RCU_EQS_DEBUG)) + pr_info("\tRCU debug extended QS entry/exit.\n"); + rcupdate_announce_bootup_oddness(); } #ifdef CONFIG_PREEMPT_RCU @@ -155,6 +179,8 @@ static void rcu_preempt_ctxt_queue(struct rcu_node *rnp, struct rcu_data *rdp) (rnp->expmask & rdp->grpmask ? RCU_EXP_BLKD : 0); struct task_struct *t = current; + lockdep_assert_held(&rnp->lock); + /* * Decide where to queue the newly blocked task. In theory, * this could be an if-statement. In practice, when I tried @@ -263,6 +289,7 @@ static void rcu_preempt_ctxt_queue(struct rcu_node *rnp, struct rcu_data *rdp) */ static void rcu_preempt_qs(void) { + RCU_LOCKDEP_WARN(preemptible(), "rcu_preempt_qs() invoked with preemption enabled!!!\n"); if (__this_cpu_read(rcu_data_p->cpu_no_qs.s)) { trace_rcu_grace_period(TPS("rcu_preempt"), __this_cpu_read(rcu_data_p->gpnum), @@ -286,12 +313,14 @@ static void rcu_preempt_qs(void) * * Caller must disable interrupts. */ -static void rcu_preempt_note_context_switch(void) +static void rcu_preempt_note_context_switch(bool preempt) { struct task_struct *t = current; struct rcu_data *rdp; struct rcu_node *rnp; + RCU_LOCKDEP_WARN(!irqs_disabled(), "rcu_preempt_note_context_switch() invoked with interrupts enabled!!!\n"); + WARN_ON_ONCE(!preempt && t->rcu_read_lock_nesting > 0); if (t->rcu_read_lock_nesting > 0 && !t->rcu_read_unlock_special.b.blocked) { @@ -607,6 +636,7 @@ static int rcu_print_task_exp_stall(struct rcu_node *rnp) */ static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp) { + RCU_LOCKDEP_WARN(preemptible(), "rcu_preempt_check_blocked_tasks() invoked with preemption enabled!!!\n"); WARN_ON_ONCE(rcu_preempt_blocked_readers_cgp(rnp)); if (rcu_preempt_has_tasks(rnp)) rnp->gp_tasks = rnp->blkd_tasks.next; @@ -643,8 +673,37 @@ static void rcu_preempt_do_callbacks(void) #endif /* #ifdef CONFIG_RCU_BOOST */ -/* - * Queue a preemptible-RCU callback for invocation after a grace period. +/** + * 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. + * + * 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) { @@ -663,8 +722,13 @@ EXPORT_SYMBOL_GPL(call_rcu); * synchronize_rcu() was waiting. RCU read-side critical sections are * delimited by rcu_read_lock() and rcu_read_unlock(), and may be nested. * - * See the description of synchronize_sched() for more detailed information - * on memory ordering guarantees. + * See the description of synchronize_sched() for more detailed + * information on memory-ordering guarantees. However, please note + * that -only- the memory-ordering guarantees apply. For example, + * synchronize_rcu() is -not- guaranteed to wait on things like code + * protected by preempt_disable(), instead, synchronize_rcu() is -only- + * guaranteed to wait on RCU read-side critical sections, that is, sections + * of code protected by rcu_read_lock(). */ void synchronize_rcu(void) { @@ -738,7 +802,7 @@ static void __init rcu_bootup_announce(void) * Because preemptible RCU does not exist, we never have to check for * CPUs being in quiescent states. */ -static void rcu_preempt_note_context_switch(void) +static void rcu_preempt_note_context_switch(bool preempt) { } @@ -835,33 +899,6 @@ void exit_rcu(void) #include "../locking/rtmutex_common.h" -#ifdef CONFIG_RCU_TRACE - -static void rcu_initiate_boost_trace(struct rcu_node *rnp) -{ - if (!rcu_preempt_has_tasks(rnp)) - rnp->n_balk_blkd_tasks++; - else if (rnp->exp_tasks == NULL && rnp->gp_tasks == NULL) - rnp->n_balk_exp_gp_tasks++; - else if (rnp->gp_tasks != NULL && rnp->boost_tasks != NULL) - rnp->n_balk_boost_tasks++; - else if (rnp->gp_tasks != NULL && rnp->qsmask != 0) - rnp->n_balk_notblocked++; - else if (rnp->gp_tasks != NULL && - ULONG_CMP_LT(jiffies, rnp->boost_time)) - rnp->n_balk_notyet++; - else - rnp->n_balk_nos++; -} - -#else /* #ifdef CONFIG_RCU_TRACE */ - -static void rcu_initiate_boost_trace(struct rcu_node *rnp) -{ -} - -#endif /* #else #ifdef CONFIG_RCU_TRACE */ - static void rcu_wake_cond(struct task_struct *t, int status) { /* @@ -992,8 +1029,8 @@ static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags) { struct task_struct *t; + lockdep_assert_held(&rnp->lock); if (!rcu_preempt_blocked_readers_cgp(rnp) && rnp->exp_tasks == NULL) { - rnp->n_balk_exp_gp_tasks++; raw_spin_unlock_irqrestore_rcu_node(rnp, flags); return; } @@ -1009,7 +1046,6 @@ static void rcu_initiate_boost(struct rcu_node *rnp, unsigned long flags) if (t) rcu_wake_cond(t, rnp->boost_kthread_status); } else { - rcu_initiate_boost_trace(rnp); raw_spin_unlock_irqrestore_rcu_node(rnp, flags); } } @@ -1260,8 +1296,7 @@ static void rcu_prepare_kthreads(int cpu) int rcu_needs_cpu(u64 basemono, u64 *nextevt) { *nextevt = KTIME_MAX; - return IS_ENABLED(CONFIG_RCU_NOCB_CPU_ALL) - ? 0 : rcu_cpu_has_callbacks(NULL); + return rcu_cpu_has_callbacks(NULL); } /* @@ -1372,10 +1407,7 @@ int rcu_needs_cpu(u64 basemono, u64 *nextevt) struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks); unsigned long dj; - if (IS_ENABLED(CONFIG_RCU_NOCB_CPU_ALL)) { - *nextevt = KTIME_MAX; - return 0; - } + RCU_LOCKDEP_WARN(!irqs_disabled(), "rcu_needs_cpu() invoked with irqs enabled!!!"); /* Snapshot to detect later posting of non-lazy callback. */ rdtp->nonlazy_posted_snap = rdtp->nonlazy_posted; @@ -1424,8 +1456,8 @@ static void rcu_prepare_for_idle(void) struct rcu_state *rsp; int tne; - if (IS_ENABLED(CONFIG_RCU_NOCB_CPU_ALL) || - rcu_is_nocb_cpu(smp_processor_id())) + RCU_LOCKDEP_WARN(!irqs_disabled(), "rcu_prepare_for_idle() invoked with irqs enabled!!!"); + if (rcu_is_nocb_cpu(smp_processor_id())) return; /* Handle nohz enablement switches conservatively. */ @@ -1479,8 +1511,8 @@ static void rcu_prepare_for_idle(void) */ static void rcu_cleanup_after_idle(void) { - if (IS_ENABLED(CONFIG_RCU_NOCB_CPU_ALL) || - rcu_is_nocb_cpu(smp_processor_id())) + RCU_LOCKDEP_WARN(!irqs_disabled(), "rcu_cleanup_after_idle() invoked with irqs enabled!!!"); + if (rcu_is_nocb_cpu(smp_processor_id())) return; if (rcu_try_advance_all_cbs()) invoke_rcu_core(); @@ -1747,7 +1779,6 @@ static void rcu_init_one_nocb(struct rcu_node *rnp) init_swait_queue_head(&rnp->nocb_gp_wq[1]); } -#ifndef CONFIG_RCU_NOCB_CPU_ALL /* Is the specified CPU a no-CBs CPU? */ bool rcu_is_nocb_cpu(int cpu) { @@ -1755,7 +1786,6 @@ bool rcu_is_nocb_cpu(int cpu) return cpumask_test_cpu(cpu, rcu_nocb_mask); return false; } -#endif /* #ifndef CONFIG_RCU_NOCB_CPU_ALL */ /* * Kick the leader kthread for this NOCB group. @@ -1769,6 +1799,7 @@ static void wake_nocb_leader(struct rcu_data *rdp, bool force) if (READ_ONCE(rdp_leader->nocb_leader_sleep) || force) { /* Prior smp_mb__after_atomic() orders against prior enqueue. */ WRITE_ONCE(rdp_leader->nocb_leader_sleep, false); + smp_mb(); /* ->nocb_leader_sleep before swake_up(). */ swake_up(&rdp_leader->nocb_wq); } } @@ -1860,7 +1891,7 @@ static void __call_rcu_nocb_enqueue(struct rcu_data *rdp, trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, TPS("WakeEmpty")); } else { - WRITE_ONCE(rdp->nocb_defer_wakeup, RCU_NOGP_WAKE); + WRITE_ONCE(rdp->nocb_defer_wakeup, RCU_NOCB_WAKE); /* Store ->nocb_defer_wakeup before ->rcu_urgent_qs. */ smp_store_release(this_cpu_ptr(&rcu_dynticks.rcu_urgent_qs), true); trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, @@ -1874,7 +1905,7 @@ static void __call_rcu_nocb_enqueue(struct rcu_data *rdp, trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, TPS("WakeOvf")); } else { - WRITE_ONCE(rdp->nocb_defer_wakeup, RCU_NOGP_WAKE_FORCE); + WRITE_ONCE(rdp->nocb_defer_wakeup, RCU_NOCB_WAKE_FORCE); /* Store ->nocb_defer_wakeup before ->rcu_urgent_qs. */ smp_store_release(this_cpu_ptr(&rcu_dynticks.rcu_urgent_qs), true); trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, @@ -2023,6 +2054,7 @@ wait_again: * nocb_gp_head, where they await a grace period. */ gotcbs = false; + smp_mb(); /* wakeup before ->nocb_head reads. */ for (rdp = my_rdp; rdp; rdp = rdp->nocb_next_follower) { rdp->nocb_gp_head = READ_ONCE(rdp->nocb_head); if (!rdp->nocb_gp_head) @@ -2201,8 +2233,8 @@ static void do_nocb_deferred_wakeup(struct rcu_data *rdp) if (!rcu_nocb_need_deferred_wakeup(rdp)) return; ndw = READ_ONCE(rdp->nocb_defer_wakeup); - WRITE_ONCE(rdp->nocb_defer_wakeup, RCU_NOGP_WAKE_NOT); - wake_nocb_leader(rdp, ndw == RCU_NOGP_WAKE_FORCE); + WRITE_ONCE(rdp->nocb_defer_wakeup, RCU_NOCB_WAKE_NOT); + wake_nocb_leader(rdp, ndw == RCU_NOCB_WAKE_FORCE); trace_rcu_nocb_wake(rdp->rsp->name, rdp->cpu, TPS("DeferredWake")); } @@ -2212,10 +2244,6 @@ void __init rcu_init_nohz(void) bool need_rcu_nocb_mask = true; struct rcu_state *rsp; -#ifdef CONFIG_RCU_NOCB_CPU_NONE - need_rcu_nocb_mask = false; -#endif /* #ifndef CONFIG_RCU_NOCB_CPU_NONE */ - #if defined(CONFIG_NO_HZ_FULL) if (tick_nohz_full_running && cpumask_weight(tick_nohz_full_mask)) need_rcu_nocb_mask = true; @@ -2231,14 +2259,6 @@ void __init rcu_init_nohz(void) if (!have_rcu_nocb_mask) return; -#ifdef CONFIG_RCU_NOCB_CPU_ZERO - pr_info("\tOffload RCU callbacks from CPU 0\n"); - cpumask_set_cpu(0, rcu_nocb_mask); -#endif /* #ifdef CONFIG_RCU_NOCB_CPU_ZERO */ -#ifdef CONFIG_RCU_NOCB_CPU_ALL - pr_info("\tOffload RCU callbacks from all CPUs\n"); - cpumask_copy(rcu_nocb_mask, cpu_possible_mask); -#endif /* #ifdef CONFIG_RCU_NOCB_CPU_ALL */ #if defined(CONFIG_NO_HZ_FULL) if (tick_nohz_full_running) cpumask_or(rcu_nocb_mask, rcu_nocb_mask, tick_nohz_full_mask); @@ -2491,421 +2511,6 @@ static void __maybe_unused rcu_kick_nohz_cpu(int cpu) #endif /* #ifdef CONFIG_NO_HZ_FULL */ } - -#ifdef CONFIG_NO_HZ_FULL_SYSIDLE - -static int full_sysidle_state; /* Current system-idle state. */ -#define RCU_SYSIDLE_NOT 0 /* Some CPU is not idle. */ -#define RCU_SYSIDLE_SHORT 1 /* All CPUs idle for brief period. */ -#define RCU_SYSIDLE_LONG 2 /* All CPUs idle for long enough. */ -#define RCU_SYSIDLE_FULL 3 /* All CPUs idle, ready for sysidle. */ -#define RCU_SYSIDLE_FULL_NOTED 4 /* Actually entered sysidle state. */ - -/* - * Invoked to note exit from irq or task transition to idle. Note that - * usermode execution does -not- count as idle here! After all, we want - * to detect full-system idle states, not RCU quiescent states and grace - * periods. The caller must have disabled interrupts. - */ -static void rcu_sysidle_enter(int irq) -{ - unsigned long j; - struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks); - - /* If there are no nohz_full= CPUs, no need to track this. */ - if (!tick_nohz_full_enabled()) - return; - - /* Adjust nesting, check for fully idle. */ - if (irq) { - rdtp->dynticks_idle_nesting--; - WARN_ON_ONCE(rdtp->dynticks_idle_nesting < 0); - if (rdtp->dynticks_idle_nesting != 0) - return; /* Still not fully idle. */ - } else { - if ((rdtp->dynticks_idle_nesting & DYNTICK_TASK_NEST_MASK) == - DYNTICK_TASK_NEST_VALUE) { - rdtp->dynticks_idle_nesting = 0; - } else { - rdtp->dynticks_idle_nesting -= DYNTICK_TASK_NEST_VALUE; - WARN_ON_ONCE(rdtp->dynticks_idle_nesting < 0); - return; /* Still not fully idle. */ - } - } - - /* Record start of fully idle period. */ - j = jiffies; - WRITE_ONCE(rdtp->dynticks_idle_jiffies, j); - smp_mb__before_atomic(); - atomic_inc(&rdtp->dynticks_idle); - smp_mb__after_atomic(); - WARN_ON_ONCE(atomic_read(&rdtp->dynticks_idle) & 0x1); -} - -/* - * Unconditionally force exit from full system-idle state. This is - * invoked when a normal CPU exits idle, but must be called separately - * for the timekeeping CPU (tick_do_timer_cpu). The reason for this - * is that the timekeeping CPU is permitted to take scheduling-clock - * interrupts while the system is in system-idle state, and of course - * rcu_sysidle_exit() has no way of distinguishing a scheduling-clock - * interrupt from any other type of interrupt. - */ -void rcu_sysidle_force_exit(void) -{ - int oldstate = READ_ONCE(full_sysidle_state); - int newoldstate; - - /* - * Each pass through the following loop attempts to exit full - * system-idle state. If contention proves to be a problem, - * a trylock-based contention tree could be used here. - */ - while (oldstate > RCU_SYSIDLE_SHORT) { - newoldstate = cmpxchg(&full_sysidle_state, - oldstate, RCU_SYSIDLE_NOT); - if (oldstate == newoldstate && - oldstate == RCU_SYSIDLE_FULL_NOTED) { - rcu_kick_nohz_cpu(tick_do_timer_cpu); - return; /* We cleared it, done! */ - } - oldstate = newoldstate; - } - smp_mb(); /* Order initial oldstate fetch vs. later non-idle work. */ -} - -/* - * Invoked to note entry to irq or task transition from idle. Note that - * usermode execution does -not- count as idle here! The caller must - * have disabled interrupts. - */ -static void rcu_sysidle_exit(int irq) -{ - struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks); - - /* If there are no nohz_full= CPUs, no need to track this. */ - if (!tick_nohz_full_enabled()) - return; - - /* Adjust nesting, check for already non-idle. */ - if (irq) { - rdtp->dynticks_idle_nesting++; - WARN_ON_ONCE(rdtp->dynticks_idle_nesting <= 0); - if (rdtp->dynticks_idle_nesting != 1) - return; /* Already non-idle. */ - } else { - /* - * Allow for irq misnesting. Yes, it really is possible - * to enter an irq handler then never leave it, and maybe - * also vice versa. Handle both possibilities. - */ - if (rdtp->dynticks_idle_nesting & DYNTICK_TASK_NEST_MASK) { - rdtp->dynticks_idle_nesting += DYNTICK_TASK_NEST_VALUE; - WARN_ON_ONCE(rdtp->dynticks_idle_nesting <= 0); - return; /* Already non-idle. */ - } else { - rdtp->dynticks_idle_nesting = DYNTICK_TASK_EXIT_IDLE; - } - } - - /* Record end of idle period. */ - smp_mb__before_atomic(); - atomic_inc(&rdtp->dynticks_idle); - smp_mb__after_atomic(); - WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks_idle) & 0x1)); - - /* - * If we are the timekeeping CPU, we are permitted to be non-idle - * during a system-idle state. This must be the case, because - * the timekeeping CPU has to take scheduling-clock interrupts - * during the time that the system is transitioning to full - * system-idle state. This means that the timekeeping CPU must - * invoke rcu_sysidle_force_exit() directly if it does anything - * more than take a scheduling-clock interrupt. - */ - if (smp_processor_id() == tick_do_timer_cpu) - return; - - /* Update system-idle state: We are clearly no longer fully idle! */ - rcu_sysidle_force_exit(); -} - -/* - * Check to see if the current CPU is idle. Note that usermode execution - * does not count as idle. The caller must have disabled interrupts, - * and must be running on tick_do_timer_cpu. - */ -static void rcu_sysidle_check_cpu(struct rcu_data *rdp, bool *isidle, - unsigned long *maxj) -{ - int cur; - unsigned long j; - struct rcu_dynticks *rdtp = rdp->dynticks; - - /* If there are no nohz_full= CPUs, don't check system-wide idleness. */ - if (!tick_nohz_full_enabled()) - return; - - /* - * If some other CPU has already reported non-idle, if this is - * not the flavor of RCU that tracks sysidle state, or if this - * is an offline or the timekeeping CPU, nothing to do. - */ - if (!*isidle || rdp->rsp != rcu_state_p || - cpu_is_offline(rdp->cpu) || rdp->cpu == tick_do_timer_cpu) - return; - /* Verify affinity of current kthread. */ - WARN_ON_ONCE(smp_processor_id() != tick_do_timer_cpu); - - /* Pick up current idle and NMI-nesting counter and check. */ - cur = atomic_read(&rdtp->dynticks_idle); - if (cur & 0x1) { - *isidle = false; /* We are not idle! */ - return; - } - smp_mb(); /* Read counters before timestamps. */ - - /* Pick up timestamps. */ - j = READ_ONCE(rdtp->dynticks_idle_jiffies); - /* If this CPU entered idle more recently, update maxj timestamp. */ - if (ULONG_CMP_LT(*maxj, j)) - *maxj = j; -} - -/* - * Is this the flavor of RCU that is handling full-system idle? - */ -static bool is_sysidle_rcu_state(struct rcu_state *rsp) -{ - return rsp == rcu_state_p; -} - -/* - * Return a delay in jiffies based on the number of CPUs, rcu_node - * leaf fanout, and jiffies tick rate. The idea is to allow larger - * systems more time to transition to full-idle state in order to - * avoid the cache thrashing that otherwise occur on the state variable. - * Really small systems (less than a couple of tens of CPUs) should - * instead use a single global atomically incremented counter, and later - * versions of this will automatically reconfigure themselves accordingly. - */ -static unsigned long rcu_sysidle_delay(void) -{ - if (nr_cpu_ids <= CONFIG_NO_HZ_FULL_SYSIDLE_SMALL) - return 0; - return DIV_ROUND_UP(nr_cpu_ids * HZ, rcu_fanout_leaf * 1000); -} - -/* - * Advance the full-system-idle state. This is invoked when all of - * the non-timekeeping CPUs are idle. - */ -static void rcu_sysidle(unsigned long j) -{ - /* Check the current state. */ - switch (READ_ONCE(full_sysidle_state)) { - case RCU_SYSIDLE_NOT: - - /* First time all are idle, so note a short idle period. */ - WRITE_ONCE(full_sysidle_state, RCU_SYSIDLE_SHORT); - break; - - case RCU_SYSIDLE_SHORT: - - /* - * Idle for a bit, time to advance to next state? - * cmpxchg failure means race with non-idle, let them win. - */ - if (ULONG_CMP_GE(jiffies, j + rcu_sysidle_delay())) - (void)cmpxchg(&full_sysidle_state, - RCU_SYSIDLE_SHORT, RCU_SYSIDLE_LONG); - break; - - case RCU_SYSIDLE_LONG: - - /* - * Do an additional check pass before advancing to full. - * cmpxchg failure means race with non-idle, let them win. - */ - if (ULONG_CMP_GE(jiffies, j + rcu_sysidle_delay())) - (void)cmpxchg(&full_sysidle_state, - RCU_SYSIDLE_LONG, RCU_SYSIDLE_FULL); - break; - - default: - break; - } -} - -/* - * Found a non-idle non-timekeeping CPU, so kick the system-idle state - * back to the beginning. - */ -static void rcu_sysidle_cancel(void) -{ - smp_mb(); - if (full_sysidle_state > RCU_SYSIDLE_SHORT) - WRITE_ONCE(full_sysidle_state, RCU_SYSIDLE_NOT); -} - -/* - * Update the sysidle state based on the results of a force-quiescent-state - * scan of the CPUs' dyntick-idle state. - */ -static void rcu_sysidle_report(struct rcu_state *rsp, int isidle, - unsigned long maxj, bool gpkt) -{ - if (rsp != rcu_state_p) - return; /* Wrong flavor, ignore. */ - if (gpkt && nr_cpu_ids <= CONFIG_NO_HZ_FULL_SYSIDLE_SMALL) - return; /* Running state machine from timekeeping CPU. */ - if (isidle) - rcu_sysidle(maxj); /* More idle! */ - else - rcu_sysidle_cancel(); /* Idle is over. */ -} - -/* - * Wrapper for rcu_sysidle_report() when called from the grace-period - * kthread's context. - */ -static void rcu_sysidle_report_gp(struct rcu_state *rsp, int isidle, - unsigned long maxj) -{ - /* If there are no nohz_full= CPUs, no need to track this. */ - if (!tick_nohz_full_enabled()) - return; - - rcu_sysidle_report(rsp, isidle, maxj, true); -} - -/* Callback and function for forcing an RCU grace period. */ -struct rcu_sysidle_head { - struct rcu_head rh; - int inuse; -}; - -static void rcu_sysidle_cb(struct rcu_head *rhp) -{ - struct rcu_sysidle_head *rshp; - - /* - * The following memory barrier is needed to replace the - * memory barriers that would normally be in the memory - * allocator. - */ - smp_mb(); /* grace period precedes setting inuse. */ - - rshp = container_of(rhp, struct rcu_sysidle_head, rh); - WRITE_ONCE(rshp->inuse, 0); -} - -/* - * Check to see if the system is fully idle, other than the timekeeping CPU. - * The caller must have disabled interrupts. This is not intended to be - * called unless tick_nohz_full_enabled(). - */ -bool rcu_sys_is_idle(void) -{ - static struct rcu_sysidle_head rsh; - int rss = READ_ONCE(full_sysidle_state); - - if (WARN_ON_ONCE(smp_processor_id() != tick_do_timer_cpu)) - return false; - - /* Handle small-system case by doing a full scan of CPUs. */ - if (nr_cpu_ids <= CONFIG_NO_HZ_FULL_SYSIDLE_SMALL) { - int oldrss = rss - 1; - - /* - * One pass to advance to each state up to _FULL. - * Give up if any pass fails to advance the state. - */ - while (rss < RCU_SYSIDLE_FULL && oldrss < rss) { - int cpu; - bool isidle = true; - unsigned long maxj = jiffies - ULONG_MAX / 4; - struct rcu_data *rdp; - - /* Scan all the CPUs looking for nonidle CPUs. */ - for_each_possible_cpu(cpu) { - rdp = per_cpu_ptr(rcu_state_p->rda, cpu); - rcu_sysidle_check_cpu(rdp, &isidle, &maxj); - if (!isidle) - break; - } - rcu_sysidle_report(rcu_state_p, isidle, maxj, false); - oldrss = rss; - rss = READ_ONCE(full_sysidle_state); - } - } - - /* If this is the first observation of an idle period, record it. */ - if (rss == RCU_SYSIDLE_FULL) { - rss = cmpxchg(&full_sysidle_state, - RCU_SYSIDLE_FULL, RCU_SYSIDLE_FULL_NOTED); - return rss == RCU_SYSIDLE_FULL; - } - - smp_mb(); /* ensure rss load happens before later caller actions. */ - - /* If already fully idle, tell the caller (in case of races). */ - if (rss == RCU_SYSIDLE_FULL_NOTED) - return true; - - /* - * If we aren't there yet, and a grace period is not in flight, - * initiate a grace period. Either way, tell the caller that - * we are not there yet. We use an xchg() rather than an assignment - * to make up for the memory barriers that would otherwise be - * provided by the memory allocator. - */ - if (nr_cpu_ids > CONFIG_NO_HZ_FULL_SYSIDLE_SMALL && - !rcu_gp_in_progress(rcu_state_p) && - !rsh.inuse && xchg(&rsh.inuse, 1) == 0) - call_rcu(&rsh.rh, rcu_sysidle_cb); - return false; -} - -/* - * Initialize dynticks sysidle state for CPUs coming online. - */ -static void rcu_sysidle_init_percpu_data(struct rcu_dynticks *rdtp) -{ - rdtp->dynticks_idle_nesting = DYNTICK_TASK_NEST_VALUE; -} - -#else /* #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */ - -static void rcu_sysidle_enter(int irq) -{ -} - -static void rcu_sysidle_exit(int irq) -{ -} - -static void rcu_sysidle_check_cpu(struct rcu_data *rdp, bool *isidle, - unsigned long *maxj) -{ -} - -static bool is_sysidle_rcu_state(struct rcu_state *rsp) -{ - return false; -} - -static void rcu_sysidle_report_gp(struct rcu_state *rsp, int isidle, - unsigned long maxj) -{ -} - -static void rcu_sysidle_init_percpu_data(struct rcu_dynticks *rdtp) -{ -} - -#endif /* #else #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */ - /* * Is this CPU a NO_HZ_FULL CPU that should ignore RCU so that the * grace-period kthread will do force_quiescent_state() processing? @@ -2936,13 +2541,7 @@ static void rcu_bind_gp_kthread(void) if (!tick_nohz_full_enabled()) return; -#ifdef CONFIG_NO_HZ_FULL_SYSIDLE - cpu = tick_do_timer_cpu; - if (cpu >= 0 && cpu < nr_cpu_ids) - set_cpus_allowed_ptr(current, cpumask_of(cpu)); -#else /* #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */ housekeeping_affine(current); -#endif /* #else #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */ } /* Record the current task on dyntick-idle entry. */ diff --git a/kernel/rcu/tree_trace.c b/kernel/rcu/tree_trace.c deleted file mode 100644 index 6cea17a1ea30..000000000000 --- a/kernel/rcu/tree_trace.c +++ /dev/null @@ -1,494 +0,0 @@ -/* - * Read-Copy Update tracing for hierarchical implementation. - * - * This program is free software; you can redistribute it and/or modify - * it under the terms of the GNU General Public License as published by - * the Free Software Foundation; either version 2 of the License, or - * (at your option) any later version. - * - * This program is distributed in the hope that it will be useful, - * but WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the - * GNU General Public License for more details. - * - * You should have received a copy of the GNU General Public License - * along with this program; if not, you can access it online at - * http://www.gnu.org/licenses/gpl-2.0.html. - * - * Copyright IBM Corporation, 2008 - * Author: Paul E. McKenney - * - * Papers: http://www.rdrop.com/users/paulmck/RCU - * - * For detailed explanation of Read-Copy Update mechanism see - - * Documentation/RCU - * - */ -#include <linux/types.h> -#include <linux/kernel.h> -#include <linux/init.h> -#include <linux/spinlock.h> -#include <linux/smp.h> -#include <linux/rcupdate.h> -#include <linux/interrupt.h> -#include <linux/sched.h> -#include <linux/atomic.h> -#include <linux/bitops.h> -#include <linux/completion.h> -#include <linux/percpu.h> -#include <linux/notifier.h> -#include <linux/cpu.h> -#include <linux/mutex.h> -#include <linux/debugfs.h> -#include <linux/seq_file.h> -#include <linux/prefetch.h> - -#define RCU_TREE_NONCORE -#include "tree.h" -#include "rcu.h" - -static int r_open(struct inode *inode, struct file *file, - const struct seq_operations *op) -{ - int ret = seq_open(file, op); - if (!ret) { - struct seq_file *m = (struct seq_file *)file->private_data; - m->private = inode->i_private; - } - return ret; -} - -static void *r_start(struct seq_file *m, loff_t *pos) -{ - struct rcu_state *rsp = (struct rcu_state *)m->private; - *pos = cpumask_next(*pos - 1, cpu_possible_mask); - if ((*pos) < nr_cpu_ids) - return per_cpu_ptr(rsp->rda, *pos); - return NULL; -} - -static void *r_next(struct seq_file *m, void *v, loff_t *pos) -{ - (*pos)++; - return r_start(m, pos); -} - -static void r_stop(struct seq_file *m, void *v) -{ -} - -static int show_rcubarrier(struct seq_file *m, void *v) -{ - struct rcu_state *rsp = (struct rcu_state *)m->private; - seq_printf(m, "bcc: %d bseq: %lu\n", - atomic_read(&rsp->barrier_cpu_count), - rsp->barrier_sequence); - return 0; -} - -static int rcubarrier_open(struct inode *inode, struct file *file) -{ - return single_open(file, show_rcubarrier, inode->i_private); -} - -static const struct file_operations rcubarrier_fops = { - .owner = THIS_MODULE, - .open = rcubarrier_open, - .read = seq_read, - .llseek = no_llseek, - .release = single_release, -}; - -#ifdef CONFIG_RCU_BOOST - -static char convert_kthread_status(unsigned int kthread_status) -{ - if (kthread_status > RCU_KTHREAD_MAX) - return '?'; - return "SRWOY"[kthread_status]; -} - -#endif /* #ifdef CONFIG_RCU_BOOST */ - -static void print_one_rcu_data(struct seq_file *m, struct rcu_data *rdp) -{ - long ql, qll; - - if (!rdp->beenonline) - return; - seq_printf(m, "%3d%cc=%ld g=%ld cnq=%d/%d:%d", - rdp->cpu, - cpu_is_offline(rdp->cpu) ? '!' : ' ', - ulong2long(rdp->completed), ulong2long(rdp->gpnum), - rdp->cpu_no_qs.b.norm, - rdp->rcu_qs_ctr_snap == per_cpu(rdp->dynticks->rcu_qs_ctr, rdp->cpu), - rdp->core_needs_qs); - seq_printf(m, " dt=%d/%llx/%d df=%lu", - rcu_dynticks_snap(rdp->dynticks), - rdp->dynticks->dynticks_nesting, - rdp->dynticks->dynticks_nmi_nesting, - rdp->dynticks_fqs); - seq_printf(m, " of=%lu", rdp->offline_fqs); - rcu_nocb_q_lengths(rdp, &ql, &qll); - qll += rcu_segcblist_n_lazy_cbs(&rdp->cblist); - ql += rcu_segcblist_n_cbs(&rdp->cblist); - seq_printf(m, " ql=%ld/%ld qs=%c%c%c%c", - qll, ql, - ".N"[!rcu_segcblist_segempty(&rdp->cblist, RCU_NEXT_TAIL)], - ".R"[!rcu_segcblist_segempty(&rdp->cblist, - RCU_NEXT_READY_TAIL)], - ".W"[!rcu_segcblist_segempty(&rdp->cblist, RCU_WAIT_TAIL)], - ".D"[!rcu_segcblist_segempty(&rdp->cblist, RCU_DONE_TAIL)]); -#ifdef CONFIG_RCU_BOOST - seq_printf(m, " kt=%d/%c ktl=%x", - per_cpu(rcu_cpu_has_work, rdp->cpu), - convert_kthread_status(per_cpu(rcu_cpu_kthread_status, - rdp->cpu)), - per_cpu(rcu_cpu_kthread_loops, rdp->cpu) & 0xffff); -#endif /* #ifdef CONFIG_RCU_BOOST */ - seq_printf(m, " b=%ld", rdp->blimit); - seq_printf(m, " ci=%lu nci=%lu co=%lu ca=%lu\n", - rdp->n_cbs_invoked, rdp->n_nocbs_invoked, - rdp->n_cbs_orphaned, rdp->n_cbs_adopted); -} - -static int show_rcudata(struct seq_file *m, void *v) -{ - print_one_rcu_data(m, (struct rcu_data *)v); - return 0; -} - -static const struct seq_operations rcudate_op = { - .start = r_start, - .next = r_next, - .stop = r_stop, - .show = show_rcudata, -}; - -static int rcudata_open(struct inode *inode, struct file *file) -{ - return r_open(inode, file, &rcudate_op); -} - -static const struct file_operations rcudata_fops = { - .owner = THIS_MODULE, - .open = rcudata_open, - .read = seq_read, - .llseek = no_llseek, - .release = seq_release, -}; - -static int show_rcuexp(struct seq_file *m, void *v) -{ - int cpu; - struct rcu_state *rsp = (struct rcu_state *)m->private; - struct rcu_data *rdp; - unsigned long s0 = 0, s1 = 0, s2 = 0, s3 = 0; - - for_each_possible_cpu(cpu) { - rdp = per_cpu_ptr(rsp->rda, cpu); - s0 += atomic_long_read(&rdp->exp_workdone0); - s1 += atomic_long_read(&rdp->exp_workdone1); - s2 += atomic_long_read(&rdp->exp_workdone2); - s3 += atomic_long_read(&rdp->exp_workdone3); - } - seq_printf(m, "s=%lu wd0=%lu wd1=%lu wd2=%lu wd3=%lu enq=%d sc=%lu\n", - rsp->expedited_sequence, s0, s1, s2, s3, - atomic_read(&rsp->expedited_need_qs), - rsp->expedited_sequence / 2); - return 0; -} - -static int rcuexp_open(struct inode *inode, struct file *file) -{ - return single_open(file, show_rcuexp, inode->i_private); -} - -static const struct file_operations rcuexp_fops = { - .owner = THIS_MODULE, - .open = rcuexp_open, - .read = seq_read, - .llseek = no_llseek, - .release = single_release, -}; - -#ifdef CONFIG_RCU_BOOST - -static void print_one_rcu_node_boost(struct seq_file *m, struct rcu_node *rnp) -{ - seq_printf(m, "%d:%d tasks=%c%c%c%c kt=%c ntb=%lu neb=%lu nnb=%lu ", - rnp->grplo, rnp->grphi, - "T."[list_empty(&rnp->blkd_tasks)], - "N."[!rnp->gp_tasks], - "E."[!rnp->exp_tasks], - "B."[!rnp->boost_tasks], - convert_kthread_status(rnp->boost_kthread_status), - rnp->n_tasks_boosted, rnp->n_exp_boosts, - rnp->n_normal_boosts); - seq_printf(m, "j=%04x bt=%04x\n", - (int)(jiffies & 0xffff), - (int)(rnp->boost_time & 0xffff)); - seq_printf(m, " balk: nt=%lu egt=%lu bt=%lu nb=%lu ny=%lu nos=%lu\n", - rnp->n_balk_blkd_tasks, - rnp->n_balk_exp_gp_tasks, - rnp->n_balk_boost_tasks, - rnp->n_balk_notblocked, - rnp->n_balk_notyet, - rnp->n_balk_nos); -} - -static int show_rcu_node_boost(struct seq_file *m, void *unused) -{ - struct rcu_node *rnp; - - rcu_for_each_leaf_node(&rcu_preempt_state, rnp) - print_one_rcu_node_boost(m, rnp); - return 0; -} - -static int rcu_node_boost_open(struct inode *inode, struct file *file) -{ - return single_open(file, show_rcu_node_boost, NULL); -} - -static const struct file_operations rcu_node_boost_fops = { - .owner = THIS_MODULE, - .open = rcu_node_boost_open, - .read = seq_read, - .llseek = no_llseek, - .release = single_release, -}; - -#endif /* #ifdef CONFIG_RCU_BOOST */ - -static void print_one_rcu_state(struct seq_file *m, struct rcu_state *rsp) -{ - unsigned long gpnum; - int level = 0; - struct rcu_node *rnp; - - gpnum = rsp->gpnum; - seq_printf(m, "c=%ld g=%ld s=%d jfq=%ld j=%x ", - ulong2long(rsp->completed), ulong2long(gpnum), - rsp->gp_state, - (long)(rsp->jiffies_force_qs - jiffies), - (int)(jiffies & 0xffff)); - seq_printf(m, "nfqs=%lu/nfqsng=%lu(%lu) fqlh=%lu oqlen=%ld/%ld\n", - rsp->n_force_qs, rsp->n_force_qs_ngp, - rsp->n_force_qs - rsp->n_force_qs_ngp, - READ_ONCE(rsp->n_force_qs_lh), - rsp->orphan_done.len_lazy, - rsp->orphan_done.len); - for (rnp = &rsp->node[0]; rnp - &rsp->node[0] < rcu_num_nodes; rnp++) { - if (rnp->level != level) { - seq_puts(m, "\n"); - level = rnp->level; - } - seq_printf(m, "%lx/%lx->%lx %c%c>%c %d:%d ^%d ", - rnp->qsmask, rnp->qsmaskinit, rnp->qsmaskinitnext, - ".G"[rnp->gp_tasks != NULL], - ".E"[rnp->exp_tasks != NULL], - ".T"[!list_empty(&rnp->blkd_tasks)], - rnp->grplo, rnp->grphi, rnp->grpnum); - } - seq_puts(m, "\n"); -} - -static int show_rcuhier(struct seq_file *m, void *v) -{ - struct rcu_state *rsp = (struct rcu_state *)m->private; - print_one_rcu_state(m, rsp); - return 0; -} - -static int rcuhier_open(struct inode *inode, struct file *file) -{ - return single_open(file, show_rcuhier, inode->i_private); -} - -static const struct file_operations rcuhier_fops = { - .owner = THIS_MODULE, - .open = rcuhier_open, - .read = seq_read, - .llseek = no_llseek, - .release = single_release, -}; - -static void show_one_rcugp(struct seq_file *m, struct rcu_state *rsp) -{ - unsigned long flags; - unsigned long completed; - unsigned long gpnum; - unsigned long gpage; - unsigned long gpmax; - struct rcu_node *rnp = &rsp->node[0]; - - raw_spin_lock_irqsave_rcu_node(rnp, flags); - completed = READ_ONCE(rsp->completed); - gpnum = READ_ONCE(rsp->gpnum); - if (completed == gpnum) - gpage = 0; - else - gpage = jiffies - rsp->gp_start; - gpmax = rsp->gp_max; - raw_spin_unlock_irqrestore(&rnp->lock, flags); - seq_printf(m, "completed=%ld gpnum=%ld age=%ld max=%ld\n", - ulong2long(completed), ulong2long(gpnum), gpage, gpmax); -} - -static int show_rcugp(struct seq_file *m, void *v) -{ - struct rcu_state *rsp = (struct rcu_state *)m->private; - show_one_rcugp(m, rsp); - return 0; -} - -static int rcugp_open(struct inode *inode, struct file *file) -{ - return single_open(file, show_rcugp, inode->i_private); -} - -static const struct file_operations rcugp_fops = { - .owner = THIS_MODULE, - .open = rcugp_open, - .read = seq_read, - .llseek = no_llseek, - .release = single_release, -}; - -static void print_one_rcu_pending(struct seq_file *m, struct rcu_data *rdp) -{ - if (!rdp->beenonline) - return; - seq_printf(m, "%3d%cnp=%ld ", - rdp->cpu, - cpu_is_offline(rdp->cpu) ? '!' : ' ', - rdp->n_rcu_pending); - seq_printf(m, "qsp=%ld rpq=%ld cbr=%ld cng=%ld ", - rdp->n_rp_core_needs_qs, - rdp->n_rp_report_qs, - rdp->n_rp_cb_ready, - rdp->n_rp_cpu_needs_gp); - seq_printf(m, "gpc=%ld gps=%ld nn=%ld ndw%ld\n", - rdp->n_rp_gp_completed, - rdp->n_rp_gp_started, - rdp->n_rp_nocb_defer_wakeup, - rdp->n_rp_need_nothing); -} - -static int show_rcu_pending(struct seq_file *m, void *v) -{ - print_one_rcu_pending(m, (struct rcu_data *)v); - return 0; -} - -static const struct seq_operations rcu_pending_op = { - .start = r_start, - .next = r_next, - .stop = r_stop, - .show = show_rcu_pending, -}; - -static int rcu_pending_open(struct inode *inode, struct file *file) -{ - return r_open(inode, file, &rcu_pending_op); -} - -static const struct file_operations rcu_pending_fops = { - .owner = THIS_MODULE, - .open = rcu_pending_open, - .read = seq_read, - .llseek = no_llseek, - .release = seq_release, -}; - -static int show_rcutorture(struct seq_file *m, void *unused) -{ - seq_printf(m, "rcutorture test sequence: %lu %s\n", - rcutorture_testseq >> 1, - (rcutorture_testseq & 0x1) ? "(test in progress)" : ""); - seq_printf(m, "rcutorture update version number: %lu\n", - rcutorture_vernum); - return 0; -} - -static int rcutorture_open(struct inode *inode, struct file *file) -{ - return single_open(file, show_rcutorture, NULL); -} - -static const struct file_operations rcutorture_fops = { - .owner = THIS_MODULE, - .open = rcutorture_open, - .read = seq_read, - .llseek = seq_lseek, - .release = single_release, -}; - -static struct dentry *rcudir; - -static int __init rcutree_trace_init(void) -{ - struct rcu_state *rsp; - struct dentry *retval; - struct dentry *rspdir; - - rcudir = debugfs_create_dir("rcu", NULL); - if (!rcudir) - goto free_out; - - for_each_rcu_flavor(rsp) { - rspdir = debugfs_create_dir(rsp->name, rcudir); - if (!rspdir) - goto free_out; - - retval = debugfs_create_file("rcudata", 0444, - rspdir, rsp, &rcudata_fops); - if (!retval) - goto free_out; - - retval = debugfs_create_file("rcuexp", 0444, - rspdir, rsp, &rcuexp_fops); - if (!retval) - goto free_out; - - retval = debugfs_create_file("rcu_pending", 0444, - rspdir, rsp, &rcu_pending_fops); - if (!retval) - goto free_out; - - retval = debugfs_create_file("rcubarrier", 0444, - rspdir, rsp, &rcubarrier_fops); - if (!retval) - goto free_out; - -#ifdef CONFIG_RCU_BOOST - if (rsp == &rcu_preempt_state) { - retval = debugfs_create_file("rcuboost", 0444, - rspdir, NULL, &rcu_node_boost_fops); - if (!retval) - goto free_out; - } -#endif - - retval = debugfs_create_file("rcugp", 0444, - rspdir, rsp, &rcugp_fops); - if (!retval) - goto free_out; - - retval = debugfs_create_file("rcuhier", 0444, - rspdir, rsp, &rcuhier_fops); - if (!retval) - goto free_out; - } - - retval = debugfs_create_file("rcutorture", 0444, rcudir, - NULL, &rcutorture_fops); - if (!retval) - goto free_out; - return 0; -free_out: - debugfs_remove_recursive(rcudir); - return 1; -} -device_initcall(rcutree_trace_init); diff --git a/kernel/rcu/update.c b/kernel/rcu/update.c index 273e869ca21d..00e77c470017 100644 --- a/kernel/rcu/update.c +++ b/kernel/rcu/update.c @@ -62,7 +62,9 @@ #define MODULE_PARAM_PREFIX "rcupdate." #ifndef CONFIG_TINY_RCU +extern int rcu_expedited; /* from sysctl */ module_param(rcu_expedited, int, 0); +extern int rcu_normal; /* from sysctl */ module_param(rcu_normal, int, 0); static int rcu_normal_after_boot; module_param(rcu_normal_after_boot, int, 0); @@ -379,6 +381,7 @@ void __wait_rcu_gp(bool checktiny, int n, call_rcu_func_t *crcu_array, struct rcu_synchronize *rs_array) { int i; + int j; /* Initialize and register callbacks for each flavor specified. */ for (i = 0; i < n; i++) { @@ -390,7 +393,11 @@ void __wait_rcu_gp(bool checktiny, int n, call_rcu_func_t *crcu_array, } 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); + for (j = 0; j < i; j++) + if (crcu_array[j] == crcu_array[i]) + break; + if (j == i) + (crcu_array[i])(&rs_array[i].head, wakeme_after_rcu); } /* Wait for all callbacks to be invoked. */ @@ -399,7 +406,11 @@ void __wait_rcu_gp(bool checktiny, int n, call_rcu_func_t *crcu_array, (crcu_array[i] == call_rcu || crcu_array[i] == call_rcu_bh)) continue; - wait_for_completion(&rs_array[i].completion); + for (j = 0; j < i; j++) + if (crcu_array[j] == crcu_array[i]) + break; + if (j == i) + wait_for_completion(&rs_array[i].completion); destroy_rcu_head_on_stack(&rs_array[i].head); } } @@ -560,15 +571,30 @@ static DEFINE_RAW_SPINLOCK(rcu_tasks_cbs_lock); DEFINE_SRCU(tasks_rcu_exit_srcu); /* Control stall timeouts. Disable with <= 0, otherwise jiffies till stall. */ -static int rcu_task_stall_timeout __read_mostly = HZ * 60 * 10; +#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 void rcu_spawn_tasks_kthread(void); static struct task_struct *rcu_tasks_kthread_ptr; -/* - * Post an RCU-tasks callback. First call must be from process context - * after the scheduler if fully operational. +/** + * 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!), 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) { @@ -851,6 +877,23 @@ static void rcu_spawn_tasks_kthread(void) #endif /* #ifdef CONFIG_TASKS_RCU */ +#ifndef CONFIG_TINY_RCU + +/* + * Print any non-default Tasks RCU settings. + */ +static void __init rcu_tasks_bootup_oddness(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 */ +} + +#endif /* #ifndef CONFIG_TINY_RCU */ + #ifdef CONFIG_PROVE_RCU /* @@ -935,3 +978,25 @@ late_initcall(rcu_verify_early_boot_tests); #else void rcu_early_boot_tests(void) {} #endif /* CONFIG_PROVE_RCU */ + +#ifndef CONFIG_TINY_RCU + +/* + * Print any significant non-default boot-time settings. + */ +void __init rcupdate_announce_bootup_oddness(void) +{ + if (rcu_normal) + pr_info("\tNo expedited grace period (rcu_normal).\n"); + else if (rcu_normal_after_boot) + pr_info("\tNo expedited grace period (rcu_normal_after_boot).\n"); + else if (rcu_expedited) + pr_info("\tAll grace periods are expedited (rcu_expedited).\n"); + if (rcu_cpu_stall_suppress) + pr_info("\tRCU CPU stall warnings suppressed (rcu_cpu_stall_suppress).\n"); + if (rcu_cpu_stall_timeout != CONFIG_RCU_CPU_STALL_TIMEOUT) + pr_info("\tRCU CPU stall warnings timeout set to %d (rcu_cpu_stall_timeout).\n", rcu_cpu_stall_timeout); + rcu_tasks_bootup_oddness(); +} + +#endif /* #ifndef CONFIG_TINY_RCU */ |