From c17ef45342cc033fdf7bdd5b28615e0090f8d2e7 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Tue, 23 Jun 2009 17:12:47 -0700 Subject: rcu: Remove Classic RCU Remove Classic RCU, given that the combination of Tree RCU and the proposed Bloatwatch RCU do everything that Classic RCU can with fewer bugs. Tree RCU has been default in x86 builds for almost six months, and seems to be quite reliable, so there does not seem to be much justification for keeping the Classic RCU code and config complexity around anymore. Signed-off-by: Paul E. McKenney Cc: akpm@linux-foundation.org Cc: niv@us.ibm.com Cc: dvhltc@us.ibm.com Cc: dipankar@in.ibm.com Cc: dhowells@redhat.com Cc: lethal@linux-sh.org Cc: kernel@wantstofly.org Signed-off-by: Ingo Molnar --- include/linux/rcuclassic.h | 178 --------------------------------------------- include/linux/rcupdate.h | 4 +- 2 files changed, 1 insertion(+), 181 deletions(-) delete mode 100644 include/linux/rcuclassic.h (limited to 'include') diff --git a/include/linux/rcuclassic.h b/include/linux/rcuclassic.h deleted file mode 100644 index bfd92e1e5d2c..000000000000 --- a/include/linux/rcuclassic.h +++ /dev/null @@ -1,178 +0,0 @@ -/* - * Read-Copy Update mechanism for mutual exclusion (classic version) - * - * 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, write to the Free Software - * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. - * - * Copyright IBM Corporation, 2001 - * - * Author: Dipankar Sarma - * - * Based on the original work by Paul McKenney - * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen. - * Papers: - * http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf - * http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001) - * - * For detailed explanation of Read-Copy Update mechanism see - - * Documentation/RCU - * - */ - -#ifndef __LINUX_RCUCLASSIC_H -#define __LINUX_RCUCLASSIC_H - -#include -#include -#include -#include -#include - -#ifdef CONFIG_RCU_CPU_STALL_DETECTOR -#define RCU_SECONDS_TILL_STALL_CHECK (10 * HZ) /* for rcp->jiffies_stall */ -#define RCU_SECONDS_TILL_STALL_RECHECK (30 * HZ) /* for rcp->jiffies_stall */ -#endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ - -/* Global control variables for rcupdate callback mechanism. */ -struct rcu_ctrlblk { - long cur; /* Current batch number. */ - long completed; /* Number of the last completed batch */ - long pending; /* Number of the last pending batch */ -#ifdef CONFIG_RCU_CPU_STALL_DETECTOR - unsigned long gp_start; /* Time at which GP started in jiffies. */ - unsigned long jiffies_stall; - /* Time at which to check for CPU stalls. */ -#endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ - - int signaled; - - spinlock_t lock ____cacheline_internodealigned_in_smp; - DECLARE_BITMAP(cpumask, NR_CPUS); /* CPUs that need to switch for */ - /* current batch to proceed. */ -} ____cacheline_internodealigned_in_smp; - -/* Is batch a before batch b ? */ -static inline int rcu_batch_before(long a, long b) -{ - return (a - b) < 0; -} - -/* Is batch a after batch b ? */ -static inline int rcu_batch_after(long a, long b) -{ - return (a - b) > 0; -} - -/* Per-CPU data for Read-Copy UPdate. */ -struct rcu_data { - /* 1) quiescent state handling : */ - long quiescbatch; /* Batch # for grace period */ - int passed_quiesc; /* User-mode/idle loop etc. */ - int qs_pending; /* core waits for quiesc state */ - - /* 2) batch handling */ - /* - * if nxtlist is not NULL, then: - * batch: - * The batch # for the last entry of nxtlist - * [*nxttail[1], NULL = *nxttail[2]): - * Entries that batch # <= batch - * [*nxttail[0], *nxttail[1]): - * Entries that batch # <= batch - 1 - * [nxtlist, *nxttail[0]): - * Entries that batch # <= batch - 2 - * The grace period for these entries has completed, and - * the other grace-period-completed entries may be moved - * here temporarily in rcu_process_callbacks(). - */ - long batch; - struct rcu_head *nxtlist; - struct rcu_head **nxttail[3]; - long qlen; /* # of queued callbacks */ - struct rcu_head *donelist; - struct rcu_head **donetail; - long blimit; /* Upper limit on a processed batch */ - int cpu; - struct rcu_head barrier; -}; - -/* - * Increment the quiescent state counter. - * The counter is a bit degenerated: We do not need to know - * how many quiescent states passed, just if there was at least - * one since the start of the grace period. Thus just a flag. - */ -extern void rcu_qsctr_inc(int cpu); -extern void rcu_bh_qsctr_inc(int cpu); - -extern int rcu_pending(int cpu); -extern int rcu_needs_cpu(int cpu); - -#ifdef CONFIG_DEBUG_LOCK_ALLOC -extern struct lockdep_map rcu_lock_map; -# define rcu_read_acquire() \ - lock_acquire(&rcu_lock_map, 0, 0, 2, 1, NULL, _THIS_IP_) -# define rcu_read_release() lock_release(&rcu_lock_map, 1, _THIS_IP_) -#else -# define rcu_read_acquire() do { } while (0) -# define rcu_read_release() do { } while (0) -#endif - -#define __rcu_read_lock() \ - do { \ - preempt_disable(); \ - __acquire(RCU); \ - rcu_read_acquire(); \ - } while (0) -#define __rcu_read_unlock() \ - do { \ - rcu_read_release(); \ - __release(RCU); \ - preempt_enable(); \ - } while (0) -#define __rcu_read_lock_bh() \ - do { \ - local_bh_disable(); \ - __acquire(RCU_BH); \ - rcu_read_acquire(); \ - } while (0) -#define __rcu_read_unlock_bh() \ - do { \ - rcu_read_release(); \ - __release(RCU_BH); \ - local_bh_enable(); \ - } while (0) - -#define __synchronize_sched() synchronize_rcu() - -#define call_rcu_sched(head, func) call_rcu(head, func) - -extern void __rcu_init(void); -#define rcu_init_sched() do { } while (0) -extern void rcu_check_callbacks(int cpu, int user); -extern void rcu_restart_cpu(int cpu); - -extern long rcu_batches_completed(void); -extern long rcu_batches_completed_bh(void); - -#define rcu_enter_nohz() do { } while (0) -#define rcu_exit_nohz() do { } while (0) - -/* A context switch is a grace period for rcuclassic. */ -static inline int rcu_blocking_is_gp(void) -{ - return num_online_cpus() == 1; -} - -#endif /* __LINUX_RCUCLASSIC_H */ diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 15fbb3ca634d..0cdfdb622faa 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -54,9 +54,7 @@ struct rcu_head { /* Internal to kernel, but needed by rcupreempt.h. */ extern int rcu_scheduler_active; -#if defined(CONFIG_CLASSIC_RCU) -#include -#elif defined(CONFIG_TREE_RCU) +#if defined(CONFIG_TREE_RCU) #include #elif defined(CONFIG_PREEMPT_RCU) #include -- cgit v1.2.3-59-g8ed1b From 03b042bf1dc14a268a3d65d38b4ec2a4261e8477 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Thu, 25 Jun 2009 09:08:16 -0700 Subject: rcu: Add synchronize_sched_expedited() primitive This adds the synchronize_sched_expedited() primitive that implements the "big hammer" expedited RCU grace periods. This primitive is placed in kernel/sched.c rather than kernel/rcupdate.c due to its need to interact closely with the migration_thread() kthread. The idea is to wake up this kthread with req->task set to NULL, in response to which the kthread reports the quiescent state resulting from the kthread having been scheduled. Because this patch needs to fallback to the slow versions of the primitives in response to some races with CPU onlining and offlining, a new synchronize_rcu_bh() primitive is added as well. Signed-off-by: Paul E. McKenney Cc: akpm@linux-foundation.org Cc: torvalds@linux-foundation.org Cc: davem@davemloft.net Cc: dada1@cosmosbay.com Cc: zbr@ioremap.net Cc: jeff.chua.linux@gmail.com Cc: paulus@samba.org Cc: laijs@cn.fujitsu.com Cc: jengelh@medozas.de Cc: r000n@r000n.net Cc: benh@kernel.crashing.org Cc: mathieu.desnoyers@polymtl.ca LKML-Reference: <12459460982947-git-send-email-> Signed-off-by: Ingo Molnar --- include/linux/rcupdate.h | 25 ++++----- include/linux/rcupreempt.h | 10 ++++ include/linux/rcutree.h | 12 ++++- kernel/rcupdate.c | 25 +++++++++ kernel/sched.c | 129 ++++++++++++++++++++++++++++++++++++++++++++- 5 files changed, 186 insertions(+), 15 deletions(-) (limited to 'include') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 0cdfdb622faa..3c89d6a2591f 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -51,7 +51,19 @@ struct rcu_head { void (*func)(struct rcu_head *head); }; -/* Internal to kernel, but needed by rcupreempt.h. */ +/* Exported common interfaces */ +extern void synchronize_rcu(void); +extern void synchronize_rcu_bh(void); +extern void rcu_barrier(void); +extern void rcu_barrier_bh(void); +extern void rcu_barrier_sched(void); +extern void synchronize_sched_expedited(void); +extern int sched_expedited_torture_stats(char *page); + +/* Internal to kernel */ +extern void rcu_init(void); +extern void rcu_scheduler_starting(void); +extern int rcu_needs_cpu(int cpu); extern int rcu_scheduler_active; #if defined(CONFIG_TREE_RCU) @@ -257,15 +269,4 @@ extern void call_rcu(struct rcu_head *head, extern void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *head)); -/* Exported common interfaces */ -extern void synchronize_rcu(void); -extern void rcu_barrier(void); -extern void rcu_barrier_bh(void); -extern void rcu_barrier_sched(void); - -/* Internal to kernel */ -extern void rcu_init(void); -extern void rcu_scheduler_starting(void); -extern int rcu_needs_cpu(int cpu); - #endif /* __LINUX_RCUPDATE_H */ diff --git a/include/linux/rcupreempt.h b/include/linux/rcupreempt.h index fce522782ffa..f164ac9b7807 100644 --- a/include/linux/rcupreempt.h +++ b/include/linux/rcupreempt.h @@ -74,6 +74,16 @@ extern int rcu_needs_cpu(int cpu); extern void __synchronize_sched(void); +static inline void synchronize_rcu_expedited(void) +{ + synchronize_rcu(); /* Placeholder for new rcupreempt implementation. */ +} + +static inline void synchronize_rcu_bh_expedited(void) +{ + synchronize_rcu_bh(); /* Placeholder for new rcupreempt impl. */ +} + extern void __rcu_init(void); extern void rcu_init_sched(void); extern void rcu_check_callbacks(int cpu, int user); diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h index 5a5153806c42..d4dfd2489633 100644 --- a/include/linux/rcutree.h +++ b/include/linux/rcutree.h @@ -286,8 +286,14 @@ static inline void __rcu_read_unlock_bh(void) #define call_rcu_sched(head, func) call_rcu(head, func) -static inline void rcu_init_sched(void) +static inline void synchronize_rcu_expedited(void) +{ + synchronize_sched_expedited(); +} + +static inline void synchronize_rcu_bh_expedited(void) { + synchronize_sched_expedited(); } extern void __rcu_init(void); @@ -297,6 +303,10 @@ extern void rcu_restart_cpu(int cpu); extern long rcu_batches_completed(void); extern long rcu_batches_completed_bh(void); +static inline void rcu_init_sched(void) +{ +} + #ifdef CONFIG_NO_HZ void rcu_enter_nohz(void); void rcu_exit_nohz(void); diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c index a967c9feb90a..eae29c25fb14 100644 --- a/kernel/rcupdate.c +++ b/kernel/rcupdate.c @@ -98,6 +98,30 @@ void synchronize_rcu(void) } EXPORT_SYMBOL_GPL(synchronize_rcu); +/** + * synchronize_rcu_bh - wait until an rcu_bh grace period has elapsed. + * + * Control will return to the caller some time after a full rcu_bh grace + * period has elapsed, in other words after all currently executing rcu_bh + * read-side critical sections have completed. RCU read-side critical + * sections are delimited by rcu_read_lock_bh() and rcu_read_unlock_bh(), + * and may be nested. + */ +void synchronize_rcu_bh(void) +{ + struct rcu_synchronize rcu; + + if (rcu_blocking_is_gp()) + return; + + init_completion(&rcu.completion); + /* Will wake me after RCU finished. */ + call_rcu_bh(&rcu.head, wakeme_after_rcu); + /* Wait for it. */ + wait_for_completion(&rcu.completion); +} +EXPORT_SYMBOL_GPL(synchronize_rcu_bh); + static void rcu_barrier_callback(struct rcu_head *notused) { if (atomic_dec_and_test(&rcu_barrier_cpu_count)) @@ -129,6 +153,7 @@ static void rcu_barrier_func(void *type) static inline void wait_migrated_callbacks(void) { wait_event(rcu_migrate_wq, !atomic_read(&rcu_migrate_type_count)); + smp_mb(); /* In case we didn't sleep. */ } /* diff --git a/kernel/sched.c b/kernel/sched.c index 7c9098d186e6..9ae80bec1c1e 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -7024,6 +7024,11 @@ fail: return ret; } +#define RCU_MIGRATION_IDLE 0 +#define RCU_MIGRATION_NEED_QS 1 +#define RCU_MIGRATION_GOT_QS 2 +#define RCU_MIGRATION_MUST_SYNC 3 + /* * migration_thread - this is a highprio system thread that performs * thread migration by bumping thread off CPU then 'pushing' onto @@ -7031,6 +7036,7 @@ fail: */ static int migration_thread(void *data) { + int badcpu; int cpu = (long)data; struct rq *rq; @@ -7065,8 +7071,17 @@ static int migration_thread(void *data) req = list_entry(head->next, struct migration_req, list); list_del_init(head->next); - spin_unlock(&rq->lock); - __migrate_task(req->task, cpu, req->dest_cpu); + if (req->task != NULL) { + spin_unlock(&rq->lock); + __migrate_task(req->task, cpu, req->dest_cpu); + } else if (likely(cpu == (badcpu = smp_processor_id()))) { + req->dest_cpu = RCU_MIGRATION_GOT_QS; + spin_unlock(&rq->lock); + } else { + req->dest_cpu = RCU_MIGRATION_MUST_SYNC; + spin_unlock(&rq->lock); + WARN_ONCE(1, "migration_thread() on CPU %d, expected %d\n", badcpu, cpu); + } local_irq_enable(); complete(&req->done); @@ -10554,3 +10569,113 @@ struct cgroup_subsys cpuacct_subsys = { .subsys_id = cpuacct_subsys_id, }; #endif /* CONFIG_CGROUP_CPUACCT */ + +#ifndef CONFIG_SMP + +int rcu_expedited_torture_stats(char *page) +{ + return 0; +} +EXPORT_SYMBOL_GPL(rcu_expedited_torture_stats); + +void synchronize_sched_expedited(void) +{ +} +EXPORT_SYMBOL_GPL(synchronize_sched_expedited); + +#else /* #ifndef CONFIG_SMP */ + +static DEFINE_PER_CPU(struct migration_req, rcu_migration_req); +static DEFINE_MUTEX(rcu_sched_expedited_mutex); + +#define RCU_EXPEDITED_STATE_POST -2 +#define RCU_EXPEDITED_STATE_IDLE -1 + +static int rcu_expedited_state = RCU_EXPEDITED_STATE_IDLE; + +int rcu_expedited_torture_stats(char *page) +{ + int cnt = 0; + int cpu; + + cnt += sprintf(&page[cnt], "state: %d /", rcu_expedited_state); + for_each_online_cpu(cpu) { + cnt += sprintf(&page[cnt], " %d:%d", + cpu, per_cpu(rcu_migration_req, cpu).dest_cpu); + } + cnt += sprintf(&page[cnt], "\n"); + return cnt; +} +EXPORT_SYMBOL_GPL(rcu_expedited_torture_stats); + +static long synchronize_sched_expedited_count; + +/* + * Wait for an rcu-sched grace period to elapse, but use "big hammer" + * approach to force grace period to end quickly. This consumes + * significant time on all CPUs, and is thus not recommended for + * any sort of common-case code. + * + * Note that it is illegal to call this function while holding any + * lock that is acquired by a CPU-hotplug notifier. Failing to + * observe this restriction will result in deadlock. + */ +void synchronize_sched_expedited(void) +{ + int cpu; + unsigned long flags; + bool need_full_sync = 0; + struct rq *rq; + struct migration_req *req; + long snap; + int trycount = 0; + + smp_mb(); /* ensure prior mod happens before capturing snap. */ + snap = ACCESS_ONCE(synchronize_sched_expedited_count) + 1; + get_online_cpus(); + while (!mutex_trylock(&rcu_sched_expedited_mutex)) { + put_online_cpus(); + if (trycount++ < 10) + udelay(trycount * num_online_cpus()); + else { + synchronize_sched(); + return; + } + if (ACCESS_ONCE(synchronize_sched_expedited_count) - snap > 0) { + smp_mb(); /* ensure test happens before caller kfree */ + return; + } + get_online_cpus(); + } + rcu_expedited_state = RCU_EXPEDITED_STATE_POST; + for_each_online_cpu(cpu) { + rq = cpu_rq(cpu); + req = &per_cpu(rcu_migration_req, cpu); + init_completion(&req->done); + req->task = NULL; + req->dest_cpu = RCU_MIGRATION_NEED_QS; + spin_lock_irqsave(&rq->lock, flags); + list_add(&req->list, &rq->migration_queue); + spin_unlock_irqrestore(&rq->lock, flags); + wake_up_process(rq->migration_thread); + } + for_each_online_cpu(cpu) { + rcu_expedited_state = cpu; + req = &per_cpu(rcu_migration_req, cpu); + rq = cpu_rq(cpu); + wait_for_completion(&req->done); + spin_lock_irqsave(&rq->lock, flags); + if (unlikely(req->dest_cpu == RCU_MIGRATION_MUST_SYNC)) + need_full_sync = 1; + req->dest_cpu = RCU_MIGRATION_IDLE; + spin_unlock_irqrestore(&rq->lock, flags); + } + rcu_expedited_state = RCU_EXPEDITED_STATE_IDLE; + mutex_unlock(&rcu_sched_expedited_mutex); + put_online_cpus(); + if (need_full_sync) + synchronize_sched(); +} +EXPORT_SYMBOL_GPL(synchronize_sched_expedited); + +#endif /* #else #ifndef CONFIG_SMP */ -- cgit v1.2.3-59-g8ed1b From 799e64f05f4bfaad2bb3165cab95c8c992a1c296 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Sat, 15 Aug 2009 09:53:47 -0700 Subject: cpu hotplug: Introduce cpu_notifier() to handle !HOTPLUG_CPU case This patch introduces a new cpu_notifier() API that is similar to hotcpu_notifier(), but which also notifies of CPUs coming online during boot in the !HOTPLUG_CPU case. Reported-by: Ingo Molnar Reported-by: Hugh Dickins Tested-by: Hugh Dickins Signed-off-by: Paul E. McKenney Cc: laijs@cn.fujitsu.com Cc: dipankar@in.ibm.com Cc: josht@linux.vnet.ibm.com Cc: akpm@linux-foundation.org Cc: mathieu.desnoyers@polymtl.ca Cc: dvhltc@us.ibm.com Cc: niv@us.ibm.com Cc: peterz@infradead.org Cc: rostedt@goodmis.org Cc: benh@kernel.crashing.org LKML-Reference: <12503552312611-git-send-email-> Signed-off-by: Ingo Molnar --- include/linux/cpu.h | 17 ++++++++++++----- 1 file changed, 12 insertions(+), 5 deletions(-) (limited to 'include') diff --git a/include/linux/cpu.h b/include/linux/cpu.h index 4d668e05d458..47536197ffdd 100644 --- a/include/linux/cpu.h +++ b/include/linux/cpu.h @@ -48,6 +48,15 @@ struct notifier_block; #ifdef CONFIG_SMP /* Need to know about CPUs going up/down? */ +#if defined(CONFIG_HOTPLUG_CPU) || !defined(MODULE) +#define cpu_notifier(fn, pri) { \ + static struct notifier_block fn##_nb __cpuinitdata = \ + { .notifier_call = fn, .priority = pri }; \ + register_cpu_notifier(&fn##_nb); \ +} +#else /* #if defined(CONFIG_HOTPLUG_CPU) || !defined(MODULE) */ +#define cpu_notifier(fn, pri) do { (void)(fn); } while (0) +#endif /* #else #if defined(CONFIG_HOTPLUG_CPU) || !defined(MODULE) */ #ifdef CONFIG_HOTPLUG_CPU extern int register_cpu_notifier(struct notifier_block *nb); extern void unregister_cpu_notifier(struct notifier_block *nb); @@ -74,6 +83,8 @@ extern void cpu_maps_update_done(void); #else /* CONFIG_SMP */ +#define cpu_notifier(fn, pri) do { (void)(fn); } while (0) + static inline int register_cpu_notifier(struct notifier_block *nb) { return 0; @@ -99,11 +110,7 @@ extern struct sysdev_class cpu_sysdev_class; extern void get_online_cpus(void); extern void put_online_cpus(void); -#define hotcpu_notifier(fn, pri) { \ - static struct notifier_block fn##_nb __cpuinitdata = \ - { .notifier_call = fn, .priority = pri }; \ - register_cpu_notifier(&fn##_nb); \ -} +#define hotcpu_notifier(fn, pri) cpu_notifier(fn, pri) #define register_hotcpu_notifier(nb) register_cpu_notifier(nb) #define unregister_hotcpu_notifier(nb) unregister_cpu_notifier(nb) int cpu_down(unsigned int cpu); -- cgit v1.2.3-59-g8ed1b From b560d8ad8583803978aaaeba50ef29dc8e97a610 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Fri, 21 Aug 2009 22:08:51 -0700 Subject: rcu: Expunge lingering references to CONFIG_CLASSIC_RCU, optimize on !SMP A couple of references to CONFIG_CLASSIC_RCU have survived. Although these are harmless, it is past time for them to go. The one in hardirq.h is strictly a readability problem. The two in pagemap.h appear to disable a !SMP performance optimization (which this patch re-enables). This does raise the issue as to whether pagemap.h should really be referring to the CPU implementation. Long term, I intend to make the RCU implementation driven by CONFIG_PREEMPT, at which point these should change from defined(CONFIG_TREE_RCU) to !defined(CONFIG_PREEMPT). In the meantime, is there something else that could be done in pagemap.h? Signed-off-by: Paul E. McKenney Cc: laijs@cn.fujitsu.com Cc: dipankar@in.ibm.com Cc: akpm@linux-foundation.org Cc: mathieu.desnoyers@polymtl.ca Cc: josht@linux.vnet.ibm.com Cc: dvhltc@us.ibm.com Cc: niv@us.ibm.com Cc: peterz@infradead.org Cc: rostedt@goodmis.org LKML-Reference: <20090822050851.GA8414@linux.vnet.ibm.com> Signed-off-by: Ingo Molnar --- include/linux/hardirq.h | 4 ++-- include/linux/pagemap.h | 4 ++-- 2 files changed, 4 insertions(+), 4 deletions(-) (limited to 'include') diff --git a/include/linux/hardirq.h b/include/linux/hardirq.h index 8246c697863d..330cb31bb496 100644 --- a/include/linux/hardirq.h +++ b/include/linux/hardirq.h @@ -132,7 +132,7 @@ static inline void account_system_vtime(struct task_struct *tsk) } #endif -#if defined(CONFIG_NO_HZ) && !defined(CONFIG_CLASSIC_RCU) +#if defined(CONFIG_NO_HZ) extern void rcu_irq_enter(void); extern void rcu_irq_exit(void); extern void rcu_nmi_enter(void); @@ -142,7 +142,7 @@ extern void rcu_nmi_exit(void); # define rcu_irq_exit() do { } while (0) # define rcu_nmi_enter() do { } while (0) # define rcu_nmi_exit() do { } while (0) -#endif /* #if defined(CONFIG_NO_HZ) && !defined(CONFIG_CLASSIC_RCU) */ +#endif /* #if defined(CONFIG_NO_HZ) */ /* * It is safe to do non-atomic ops on ->hardirq_context, diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h index aec3252afcf5..ed5d7501e181 100644 --- a/include/linux/pagemap.h +++ b/include/linux/pagemap.h @@ -132,7 +132,7 @@ static inline int page_cache_get_speculative(struct page *page) { VM_BUG_ON(in_interrupt()); -#if !defined(CONFIG_SMP) && defined(CONFIG_CLASSIC_RCU) +#if !defined(CONFIG_SMP) && defined(CONFIG_TREE_RCU) # ifdef CONFIG_PREEMPT VM_BUG_ON(!in_atomic()); # endif @@ -170,7 +170,7 @@ static inline int page_cache_add_speculative(struct page *page, int count) { VM_BUG_ON(in_interrupt()); -#if !defined(CONFIG_SMP) && defined(CONFIG_CLASSIC_RCU) +#if !defined(CONFIG_SMP) && defined(CONFIG_TREE_RCU) # ifdef CONFIG_PREEMPT VM_BUG_ON(!in_atomic()); # endif -- cgit v1.2.3-59-g8ed1b From 9f77da9f40045253e91f55c12d4481254b513d2d Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Sat, 22 Aug 2009 13:56:45 -0700 Subject: rcu: Move private definitions from include/linux/rcutree.h to kernel/rcutree.h Some information hiding that makes it easier to merge preemptability into rcutree without descending into #include hell. Signed-off-by: Paul E. McKenney Cc: laijs@cn.fujitsu.com Cc: dipankar@in.ibm.com Cc: akpm@linux-foundation.org Cc: mathieu.desnoyers@polymtl.ca Cc: josht@linux.vnet.ibm.com Cc: dvhltc@us.ibm.com Cc: niv@us.ibm.com Cc: peterz@infradead.org Cc: rostedt@goodmis.org LKML-Reference: <1250974613373-git-send-email-> Signed-off-by: Ingo Molnar --- include/linux/rcutree.h | 211 ------------------------------------------ kernel/rcutree.c | 2 + kernel/rcutree.h | 238 ++++++++++++++++++++++++++++++++++++++++++++++++ kernel/rcutree_trace.c | 1 + 4 files changed, 241 insertions(+), 211 deletions(-) (limited to 'include') diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h index d4dfd2489633..e37d5e2a8353 100644 --- a/include/linux/rcutree.h +++ b/include/linux/rcutree.h @@ -30,217 +30,6 @@ #ifndef __LINUX_RCUTREE_H #define __LINUX_RCUTREE_H -#include -#include -#include -#include -#include - -/* - * Define shape of hierarchy based on NR_CPUS and CONFIG_RCU_FANOUT. - * In theory, it should be possible to add more levels straightforwardly. - * In practice, this has not been tested, so there is probably some - * bug somewhere. - */ -#define MAX_RCU_LVLS 3 -#define RCU_FANOUT (CONFIG_RCU_FANOUT) -#define RCU_FANOUT_SQ (RCU_FANOUT * RCU_FANOUT) -#define RCU_FANOUT_CUBE (RCU_FANOUT_SQ * RCU_FANOUT) - -#if NR_CPUS <= RCU_FANOUT -# define NUM_RCU_LVLS 1 -# define NUM_RCU_LVL_0 1 -# define NUM_RCU_LVL_1 (NR_CPUS) -# define NUM_RCU_LVL_2 0 -# define NUM_RCU_LVL_3 0 -#elif NR_CPUS <= RCU_FANOUT_SQ -# define NUM_RCU_LVLS 2 -# define NUM_RCU_LVL_0 1 -# define NUM_RCU_LVL_1 (((NR_CPUS) + RCU_FANOUT - 1) / RCU_FANOUT) -# define NUM_RCU_LVL_2 (NR_CPUS) -# define NUM_RCU_LVL_3 0 -#elif NR_CPUS <= RCU_FANOUT_CUBE -# define NUM_RCU_LVLS 3 -# define NUM_RCU_LVL_0 1 -# define NUM_RCU_LVL_1 (((NR_CPUS) + RCU_FANOUT_SQ - 1) / RCU_FANOUT_SQ) -# define NUM_RCU_LVL_2 (((NR_CPUS) + (RCU_FANOUT) - 1) / (RCU_FANOUT)) -# define NUM_RCU_LVL_3 NR_CPUS -#else -# error "CONFIG_RCU_FANOUT insufficient for NR_CPUS" -#endif /* #if (NR_CPUS) <= RCU_FANOUT */ - -#define RCU_SUM (NUM_RCU_LVL_0 + NUM_RCU_LVL_1 + NUM_RCU_LVL_2 + NUM_RCU_LVL_3) -#define NUM_RCU_NODES (RCU_SUM - NR_CPUS) - -/* - * Dynticks per-CPU state. - */ -struct rcu_dynticks { - int dynticks_nesting; /* Track nesting level, sort of. */ - int dynticks; /* Even value for dynticks-idle, else odd. */ - int dynticks_nmi; /* Even value for either dynticks-idle or */ - /* not in nmi handler, else odd. So this */ - /* remains even for nmi from irq handler. */ -}; - -/* - * Definition for node within the RCU grace-period-detection hierarchy. - */ -struct rcu_node { - spinlock_t lock; - unsigned long qsmask; /* CPUs or groups that need to switch in */ - /* order for current grace period to proceed.*/ - unsigned long qsmaskinit; - /* Per-GP initialization for qsmask. */ - unsigned long grpmask; /* Mask to apply to parent qsmask. */ - int grplo; /* lowest-numbered CPU or group here. */ - int grphi; /* highest-numbered CPU or group here. */ - u8 grpnum; /* CPU/group number for next level up. */ - u8 level; /* root is at level 0. */ - struct rcu_node *parent; -} ____cacheline_internodealigned_in_smp; - -/* Index values for nxttail array in struct rcu_data. */ -#define RCU_DONE_TAIL 0 /* Also RCU_WAIT head. */ -#define RCU_WAIT_TAIL 1 /* Also RCU_NEXT_READY head. */ -#define RCU_NEXT_READY_TAIL 2 /* Also RCU_NEXT head. */ -#define RCU_NEXT_TAIL 3 -#define RCU_NEXT_SIZE 4 - -/* Per-CPU data for read-copy update. */ -struct rcu_data { - /* 1) quiescent-state and grace-period handling : */ - long completed; /* Track rsp->completed gp number */ - /* in order to detect GP end. */ - long gpnum; /* Highest gp number that this CPU */ - /* is aware of having started. */ - long passed_quiesc_completed; - /* Value of completed at time of qs. */ - bool passed_quiesc; /* User-mode/idle loop etc. */ - bool qs_pending; /* Core waits for quiesc state. */ - bool beenonline; /* CPU online at least once. */ - struct rcu_node *mynode; /* This CPU's leaf of hierarchy */ - unsigned long grpmask; /* Mask to apply to leaf qsmask. */ - - /* 2) batch handling */ - /* - * If nxtlist is not NULL, it is partitioned as follows. - * Any of the partitions might be empty, in which case the - * pointer to that partition will be equal to the pointer for - * the following partition. When the list is empty, all of - * the nxttail elements point to nxtlist, which is NULL. - * - * [*nxttail[RCU_NEXT_READY_TAIL], NULL = *nxttail[RCU_NEXT_TAIL]): - * Entries that might have arrived after current GP ended - * [*nxttail[RCU_WAIT_TAIL], *nxttail[RCU_NEXT_READY_TAIL]): - * Entries known to have arrived before current GP ended - * [*nxttail[RCU_DONE_TAIL], *nxttail[RCU_WAIT_TAIL]): - * Entries that batch # <= ->completed - 1: waiting for current GP - * [nxtlist, *nxttail[RCU_DONE_TAIL]): - * Entries that batch # <= ->completed - * The grace period for these entries has completed, and - * the other grace-period-completed entries may be moved - * here temporarily in rcu_process_callbacks(). - */ - struct rcu_head *nxtlist; - struct rcu_head **nxttail[RCU_NEXT_SIZE]; - long qlen; /* # of queued callbacks */ - long blimit; /* Upper limit on a processed batch */ - -#ifdef CONFIG_NO_HZ - /* 3) dynticks interface. */ - struct rcu_dynticks *dynticks; /* Shared per-CPU dynticks state. */ - int dynticks_snap; /* Per-GP tracking for dynticks. */ - int dynticks_nmi_snap; /* Per-GP tracking for dynticks_nmi. */ -#endif /* #ifdef CONFIG_NO_HZ */ - - /* 4) reasons this CPU needed to be kicked by force_quiescent_state */ -#ifdef CONFIG_NO_HZ - unsigned long dynticks_fqs; /* Kicked due to dynticks idle. */ -#endif /* #ifdef CONFIG_NO_HZ */ - unsigned long offline_fqs; /* Kicked due to being offline. */ - unsigned long resched_ipi; /* Sent a resched IPI. */ - - /* 5) __rcu_pending() statistics. */ - long n_rcu_pending; /* rcu_pending() calls since boot. */ - long n_rp_qs_pending; - long n_rp_cb_ready; - long n_rp_cpu_needs_gp; - long n_rp_gp_completed; - long n_rp_gp_started; - long n_rp_need_fqs; - long n_rp_need_nothing; - - int cpu; -}; - -/* Values for signaled field in struct rcu_state. */ -#define RCU_GP_INIT 0 /* Grace period being initialized. */ -#define RCU_SAVE_DYNTICK 1 /* Need to scan dyntick state. */ -#define RCU_FORCE_QS 2 /* Need to force quiescent state. */ -#ifdef CONFIG_NO_HZ -#define RCU_SIGNAL_INIT RCU_SAVE_DYNTICK -#else /* #ifdef CONFIG_NO_HZ */ -#define RCU_SIGNAL_INIT RCU_FORCE_QS -#endif /* #else #ifdef CONFIG_NO_HZ */ - -#define RCU_JIFFIES_TILL_FORCE_QS 3 /* for rsp->jiffies_force_qs */ -#ifdef CONFIG_RCU_CPU_STALL_DETECTOR -#define RCU_SECONDS_TILL_STALL_CHECK (10 * HZ) /* for rsp->jiffies_stall */ -#define RCU_SECONDS_TILL_STALL_RECHECK (30 * HZ) /* for rsp->jiffies_stall */ -#define RCU_STALL_RAT_DELAY 2 /* Allow other CPUs time */ - /* to take at least one */ - /* scheduling clock irq */ - /* before ratting on them. */ - -#endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ - -/* - * RCU global state, including node hierarchy. This hierarchy is - * represented in "heap" form in a dense array. The root (first level) - * of the hierarchy is in ->node[0] (referenced by ->level[0]), the second - * level in ->node[1] through ->node[m] (->node[1] referenced by ->level[1]), - * and the third level in ->node[m+1] and following (->node[m+1] referenced - * by ->level[2]). The number of levels is determined by the number of - * CPUs and by CONFIG_RCU_FANOUT. Small systems will have a "hierarchy" - * consisting of a single rcu_node. - */ -struct rcu_state { - struct rcu_node node[NUM_RCU_NODES]; /* Hierarchy. */ - struct rcu_node *level[NUM_RCU_LVLS]; /* Hierarchy levels. */ - u32 levelcnt[MAX_RCU_LVLS + 1]; /* # nodes in each level. */ - u8 levelspread[NUM_RCU_LVLS]; /* kids/node in each level. */ - struct rcu_data *rda[NR_CPUS]; /* array of rdp pointers. */ - - /* The following fields are guarded by the root rcu_node's lock. */ - - u8 signaled ____cacheline_internodealigned_in_smp; - /* Force QS state. */ - long gpnum; /* Current gp number. */ - long completed; /* # of last completed gp. */ - spinlock_t onofflock; /* exclude on/offline and */ - /* starting new GP. */ - spinlock_t fqslock; /* Only one task forcing */ - /* quiescent states. */ - unsigned long jiffies_force_qs; /* Time at which to invoke */ - /* force_quiescent_state(). */ - unsigned long n_force_qs; /* Number of calls to */ - /* force_quiescent_state(). */ - unsigned long n_force_qs_lh; /* ~Number of calls leaving */ - /* due to lock unavailable. */ - unsigned long n_force_qs_ngp; /* Number of calls leaving */ - /* due to no GP active. */ -#ifdef CONFIG_RCU_CPU_STALL_DETECTOR - unsigned long gp_start; /* Time at which GP started, */ - /* but in jiffies. */ - unsigned long jiffies_stall; /* Time at which to check */ - /* for CPU stalls. */ -#endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ -#ifdef CONFIG_NO_HZ - long dynticks_completed; /* Value of completed @ snap. */ -#endif /* #ifdef CONFIG_NO_HZ */ -}; - extern void rcu_qsctr_inc(int cpu); extern void rcu_bh_qsctr_inc(int cpu); diff --git a/kernel/rcutree.c b/kernel/rcutree.c index 75762cddbe03..a162f859dd32 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -46,6 +46,8 @@ #include #include +#include "rcutree.h" + #ifdef CONFIG_DEBUG_LOCK_ALLOC static struct lock_class_key rcu_lock_key; struct lockdep_map rcu_lock_map = diff --git a/kernel/rcutree.h b/kernel/rcutree.h index 5e872bbf07f5..7cc830a1c44a 100644 --- a/kernel/rcutree.h +++ b/kernel/rcutree.h @@ -1,3 +1,239 @@ +/* + * Read-Copy Update mechanism for mutual exclusion (tree-based version) + * Internal non-public definitions. + * + * 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, write to the Free Software + * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. + * + * Copyright IBM Corporation, 2008 + * + * Author: Ingo Molnar + * Paul E. McKenney + */ + +#include +#include +#include +#include +#include + +/* + * Define shape of hierarchy based on NR_CPUS and CONFIG_RCU_FANOUT. + * In theory, it should be possible to add more levels straightforwardly. + * In practice, this has not been tested, so there is probably some + * bug somewhere. + */ +#define MAX_RCU_LVLS 3 +#define RCU_FANOUT (CONFIG_RCU_FANOUT) +#define RCU_FANOUT_SQ (RCU_FANOUT * RCU_FANOUT) +#define RCU_FANOUT_CUBE (RCU_FANOUT_SQ * RCU_FANOUT) + +#if NR_CPUS <= RCU_FANOUT +# define NUM_RCU_LVLS 1 +# define NUM_RCU_LVL_0 1 +# define NUM_RCU_LVL_1 (NR_CPUS) +# define NUM_RCU_LVL_2 0 +# define NUM_RCU_LVL_3 0 +#elif NR_CPUS <= RCU_FANOUT_SQ +# define NUM_RCU_LVLS 2 +# define NUM_RCU_LVL_0 1 +# define NUM_RCU_LVL_1 (((NR_CPUS) + RCU_FANOUT - 1) / RCU_FANOUT) +# define NUM_RCU_LVL_2 (NR_CPUS) +# define NUM_RCU_LVL_3 0 +#elif NR_CPUS <= RCU_FANOUT_CUBE +# define NUM_RCU_LVLS 3 +# define NUM_RCU_LVL_0 1 +# define NUM_RCU_LVL_1 (((NR_CPUS) + RCU_FANOUT_SQ - 1) / RCU_FANOUT_SQ) +# define NUM_RCU_LVL_2 (((NR_CPUS) + (RCU_FANOUT) - 1) / (RCU_FANOUT)) +# define NUM_RCU_LVL_3 NR_CPUS +#else +# error "CONFIG_RCU_FANOUT insufficient for NR_CPUS" +#endif /* #if (NR_CPUS) <= RCU_FANOUT */ + +#define RCU_SUM (NUM_RCU_LVL_0 + NUM_RCU_LVL_1 + NUM_RCU_LVL_2 + NUM_RCU_LVL_3) +#define NUM_RCU_NODES (RCU_SUM - NR_CPUS) + +/* + * Dynticks per-CPU state. + */ +struct rcu_dynticks { + int dynticks_nesting; /* Track nesting level, sort of. */ + int dynticks; /* Even value for dynticks-idle, else odd. */ + int dynticks_nmi; /* Even value for either dynticks-idle or */ + /* not in nmi handler, else odd. So this */ + /* remains even for nmi from irq handler. */ +}; + +/* + * Definition for node within the RCU grace-period-detection hierarchy. + */ +struct rcu_node { + spinlock_t lock; + unsigned long qsmask; /* CPUs or groups that need to switch in */ + /* order for current grace period to proceed.*/ + unsigned long qsmaskinit; + /* Per-GP initialization for qsmask. */ + unsigned long grpmask; /* Mask to apply to parent qsmask. */ + int grplo; /* lowest-numbered CPU or group here. */ + int grphi; /* highest-numbered CPU or group here. */ + u8 grpnum; /* CPU/group number for next level up. */ + u8 level; /* root is at level 0. */ + struct rcu_node *parent; +} ____cacheline_internodealigned_in_smp; + +/* Index values for nxttail array in struct rcu_data. */ +#define RCU_DONE_TAIL 0 /* Also RCU_WAIT head. */ +#define RCU_WAIT_TAIL 1 /* Also RCU_NEXT_READY head. */ +#define RCU_NEXT_READY_TAIL 2 /* Also RCU_NEXT head. */ +#define RCU_NEXT_TAIL 3 +#define RCU_NEXT_SIZE 4 + +/* Per-CPU data for read-copy update. */ +struct rcu_data { + /* 1) quiescent-state and grace-period handling : */ + long completed; /* Track rsp->completed gp number */ + /* in order to detect GP end. */ + long gpnum; /* Highest gp number that this CPU */ + /* is aware of having started. */ + long passed_quiesc_completed; + /* Value of completed at time of qs. */ + bool passed_quiesc; /* User-mode/idle loop etc. */ + bool qs_pending; /* Core waits for quiesc state. */ + bool beenonline; /* CPU online at least once. */ + struct rcu_node *mynode; /* This CPU's leaf of hierarchy */ + unsigned long grpmask; /* Mask to apply to leaf qsmask. */ + + /* 2) batch handling */ + /* + * If nxtlist is not NULL, it is partitioned as follows. + * Any of the partitions might be empty, in which case the + * pointer to that partition will be equal to the pointer for + * the following partition. When the list is empty, all of + * the nxttail elements point to nxtlist, which is NULL. + * + * [*nxttail[RCU_NEXT_READY_TAIL], NULL = *nxttail[RCU_NEXT_TAIL]): + * Entries that might have arrived after current GP ended + * [*nxttail[RCU_WAIT_TAIL], *nxttail[RCU_NEXT_READY_TAIL]): + * Entries known to have arrived before current GP ended + * [*nxttail[RCU_DONE_TAIL], *nxttail[RCU_WAIT_TAIL]): + * Entries that batch # <= ->completed - 1: waiting for current GP + * [nxtlist, *nxttail[RCU_DONE_TAIL]): + * Entries that batch # <= ->completed + * The grace period for these entries has completed, and + * the other grace-period-completed entries may be moved + * here temporarily in rcu_process_callbacks(). + */ + struct rcu_head *nxtlist; + struct rcu_head **nxttail[RCU_NEXT_SIZE]; + long qlen; /* # of queued callbacks */ + long blimit; /* Upper limit on a processed batch */ + +#ifdef CONFIG_NO_HZ + /* 3) dynticks interface. */ + struct rcu_dynticks *dynticks; /* Shared per-CPU dynticks state. */ + int dynticks_snap; /* Per-GP tracking for dynticks. */ + int dynticks_nmi_snap; /* Per-GP tracking for dynticks_nmi. */ +#endif /* #ifdef CONFIG_NO_HZ */ + + /* 4) reasons this CPU needed to be kicked by force_quiescent_state */ +#ifdef CONFIG_NO_HZ + unsigned long dynticks_fqs; /* Kicked due to dynticks idle. */ +#endif /* #ifdef CONFIG_NO_HZ */ + unsigned long offline_fqs; /* Kicked due to being offline. */ + unsigned long resched_ipi; /* Sent a resched IPI. */ + + /* 5) __rcu_pending() statistics. */ + long n_rcu_pending; /* rcu_pending() calls since boot. */ + long n_rp_qs_pending; + long n_rp_cb_ready; + long n_rp_cpu_needs_gp; + long n_rp_gp_completed; + long n_rp_gp_started; + long n_rp_need_fqs; + long n_rp_need_nothing; + + int cpu; +}; + +/* Values for signaled field in struct rcu_state. */ +#define RCU_GP_INIT 0 /* Grace period being initialized. */ +#define RCU_SAVE_DYNTICK 1 /* Need to scan dyntick state. */ +#define RCU_FORCE_QS 2 /* Need to force quiescent state. */ +#ifdef CONFIG_NO_HZ +#define RCU_SIGNAL_INIT RCU_SAVE_DYNTICK +#else /* #ifdef CONFIG_NO_HZ */ +#define RCU_SIGNAL_INIT RCU_FORCE_QS +#endif /* #else #ifdef CONFIG_NO_HZ */ + +#define RCU_JIFFIES_TILL_FORCE_QS 3 /* for rsp->jiffies_force_qs */ +#ifdef CONFIG_RCU_CPU_STALL_DETECTOR +#define RCU_SECONDS_TILL_STALL_CHECK (10 * HZ) /* for rsp->jiffies_stall */ +#define RCU_SECONDS_TILL_STALL_RECHECK (30 * HZ) /* for rsp->jiffies_stall */ +#define RCU_STALL_RAT_DELAY 2 /* Allow other CPUs time */ + /* to take at least one */ + /* scheduling clock irq */ + /* before ratting on them. */ + +#endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ + +/* + * RCU global state, including node hierarchy. This hierarchy is + * represented in "heap" form in a dense array. The root (first level) + * of the hierarchy is in ->node[0] (referenced by ->level[0]), the second + * level in ->node[1] through ->node[m] (->node[1] referenced by ->level[1]), + * and the third level in ->node[m+1] and following (->node[m+1] referenced + * by ->level[2]). The number of levels is determined by the number of + * CPUs and by CONFIG_RCU_FANOUT. Small systems will have a "hierarchy" + * consisting of a single rcu_node. + */ +struct rcu_state { + struct rcu_node node[NUM_RCU_NODES]; /* Hierarchy. */ + struct rcu_node *level[NUM_RCU_LVLS]; /* Hierarchy levels. */ + u32 levelcnt[MAX_RCU_LVLS + 1]; /* # nodes in each level. */ + u8 levelspread[NUM_RCU_LVLS]; /* kids/node in each level. */ + struct rcu_data *rda[NR_CPUS]; /* array of rdp pointers. */ + + /* The following fields are guarded by the root rcu_node's lock. */ + + u8 signaled ____cacheline_internodealigned_in_smp; + /* Force QS state. */ + long gpnum; /* Current gp number. */ + long completed; /* # of last completed gp. */ + spinlock_t onofflock; /* exclude on/offline and */ + /* starting new GP. */ + spinlock_t fqslock; /* Only one task forcing */ + /* quiescent states. */ + unsigned long jiffies_force_qs; /* Time at which to invoke */ + /* force_quiescent_state(). */ + unsigned long n_force_qs; /* Number of calls to */ + /* force_quiescent_state(). */ + unsigned long n_force_qs_lh; /* ~Number of calls leaving */ + /* due to lock unavailable. */ + unsigned long n_force_qs_ngp; /* Number of calls leaving */ + /* due to no GP active. */ +#ifdef CONFIG_RCU_CPU_STALL_DETECTOR + unsigned long gp_start; /* Time at which GP started, */ + /* but in jiffies. */ + unsigned long jiffies_stall; /* Time at which to check */ + /* for CPU stalls. */ +#endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ +#ifdef CONFIG_NO_HZ + long dynticks_completed; /* Value of completed @ snap. */ +#endif /* #ifdef CONFIG_NO_HZ */ +}; + +#ifdef RCU_TREE_NONCORE /* * RCU implementation internal declarations: @@ -8,3 +244,5 @@ DECLARE_PER_CPU(struct rcu_data, rcu_data); extern struct rcu_state rcu_bh_state; DECLARE_PER_CPU(struct rcu_data, rcu_bh_data); +#endif /* #ifdef RCU_TREE_NONCORE */ + diff --git a/kernel/rcutree_trace.c b/kernel/rcutree_trace.c index fe1dcdbf1ca3..0cb52b887758 100644 --- a/kernel/rcutree_trace.c +++ b/kernel/rcutree_trace.c @@ -43,6 +43,7 @@ #include #include +#define RCU_TREE_NONCORE #include "rcutree.h" static void print_one_rcu_data(struct seq_file *m, struct rcu_data *rdp) -- cgit v1.2.3-59-g8ed1b From d6714c22b43fbcbead7e7b706ff270e15f04a791 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Sat, 22 Aug 2009 13:56:46 -0700 Subject: rcu: Renamings to increase RCU clarity Make RCU-sched, RCU-bh, and RCU-preempt be underlying implementations, with "RCU" defined in terms of one of the three. Update the outdated rcu_qsctr_inc() names, as these functions no longer increment anything. Signed-off-by: Paul E. McKenney Cc: laijs@cn.fujitsu.com Cc: dipankar@in.ibm.com Cc: akpm@linux-foundation.org Cc: mathieu.desnoyers@polymtl.ca Cc: josht@linux.vnet.ibm.com Cc: dvhltc@us.ibm.com Cc: niv@us.ibm.com Cc: peterz@infradead.org Cc: rostedt@goodmis.org LKML-Reference: <12509746132696-git-send-email-> Signed-off-by: Ingo Molnar --- Documentation/RCU/trace.txt | 7 ++-- include/linux/rcupdate.h | 21 +++++++++--- include/linux/rcupreempt.h | 4 +-- include/linux/rcutree.h | 8 +++-- kernel/rcupreempt.c | 8 ++--- kernel/rcutree.c | 80 ++++++++++++++++++++++++++++----------------- kernel/rcutree.h | 4 +-- kernel/rcutree_trace.c | 20 ++++++------ kernel/sched.c | 2 +- kernel/softirq.c | 4 +-- 10 files changed, 95 insertions(+), 63 deletions(-) (limited to 'include') diff --git a/Documentation/RCU/trace.txt b/Documentation/RCU/trace.txt index 02cced183b2d..187bbf10c923 100644 --- a/Documentation/RCU/trace.txt +++ b/Documentation/RCU/trace.txt @@ -191,8 +191,7 @@ rcu/rcuhier (which displays the struct rcu_node hierarchy). The output of "cat rcu/rcudata" looks as follows: -rcu: -rcu: +rcu_sched: 0 c=17829 g=17829 pq=1 pqc=17829 qp=0 dt=10951/1 dn=0 df=1101 of=0 ri=36 ql=0 b=10 1 c=17829 g=17829 pq=1 pqc=17829 qp=0 dt=16117/1 dn=0 df=1015 of=0 ri=0 ql=0 b=10 2 c=17829 g=17829 pq=1 pqc=17829 qp=0 dt=1445/1 dn=0 df=1839 of=0 ri=0 ql=0 b=10 @@ -306,7 +305,7 @@ comma-separated-variable spreadsheet format. The output of "cat rcu/rcugp" looks as follows: -rcu: completed=33062 gpnum=33063 +rcu_sched: completed=33062 gpnum=33063 rcu_bh: completed=464 gpnum=464 Again, this output is for both "rcu" and "rcu_bh". The fields are @@ -413,7 +412,7 @@ o Each element of the form "1/1 0:127 ^0" represents one struct The output of "cat rcu/rcu_pending" looks as follows: -rcu: +rcu_sched: 0 np=255892 qsp=53936 cbr=0 cng=14417 gpc=10033 gps=24320 nf=6445 nn=146741 1 np=261224 qsp=54638 cbr=0 cng=25723 gpc=16310 gps=2849 nf=5912 nn=155792 2 np=237496 qsp=49664 cbr=0 cng=2762 gpc=45478 gps=1762 nf=1201 nn=136629 diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 3c89d6a2591f..e920f0fd59d8 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -157,17 +157,28 @@ extern int rcu_scheduler_active; * - call_rcu_sched() and rcu_barrier_sched() * on the write-side to insure proper synchronization. */ -#define rcu_read_lock_sched() preempt_disable() -#define rcu_read_lock_sched_notrace() preempt_disable_notrace() +static inline void rcu_read_lock_sched(void) +{ + preempt_disable(); +} +static inline void rcu_read_lock_sched_notrace(void) +{ + preempt_disable_notrace(); +} /* * rcu_read_unlock_sched - marks the end of a RCU-classic critical section * * See rcu_read_lock_sched for more information. */ -#define rcu_read_unlock_sched() preempt_enable() -#define rcu_read_unlock_sched_notrace() preempt_enable_notrace() - +static inline void rcu_read_unlock_sched(void) +{ + preempt_enable(); +} +static inline void rcu_read_unlock_sched_notrace(void) +{ + preempt_enable_notrace(); +} /** diff --git a/include/linux/rcupreempt.h b/include/linux/rcupreempt.h index f164ac9b7807..2963f080e48d 100644 --- a/include/linux/rcupreempt.h +++ b/include/linux/rcupreempt.h @@ -40,8 +40,8 @@ #include #include -extern void rcu_qsctr_inc(int cpu); -static inline void rcu_bh_qsctr_inc(int cpu) { } +extern void rcu_sched_qs(int cpu); +static inline void rcu_bh_qs(int cpu) { } /* * Someone might want to pass call_rcu_bh as a function pointer. diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h index e37d5e2a8353..a0852d0d915b 100644 --- a/include/linux/rcutree.h +++ b/include/linux/rcutree.h @@ -30,8 +30,8 @@ #ifndef __LINUX_RCUTREE_H #define __LINUX_RCUTREE_H -extern void rcu_qsctr_inc(int cpu); -extern void rcu_bh_qsctr_inc(int cpu); +extern void rcu_sched_qs(int cpu); +extern void rcu_bh_qs(int cpu); extern int rcu_pending(int cpu); extern int rcu_needs_cpu(int cpu); @@ -73,7 +73,8 @@ static inline void __rcu_read_unlock_bh(void) #define __synchronize_sched() synchronize_rcu() -#define call_rcu_sched(head, func) call_rcu(head, func) +extern void call_rcu_sched(struct rcu_head *head, + void (*func)(struct rcu_head *rcu)); static inline void synchronize_rcu_expedited(void) { @@ -91,6 +92,7 @@ extern void rcu_restart_cpu(int cpu); extern long rcu_batches_completed(void); extern long rcu_batches_completed_bh(void); +extern long rcu_batches_completed_sched(void); static inline void rcu_init_sched(void) { diff --git a/kernel/rcupreempt.c b/kernel/rcupreempt.c index 510898a7bd69..7d777c9f394c 100644 --- a/kernel/rcupreempt.c +++ b/kernel/rcupreempt.c @@ -159,7 +159,7 @@ static DEFINE_PER_CPU_SHARED_ALIGNED(struct rcu_dyntick_sched, rcu_dyntick_sched .dynticks = 1, }; -void rcu_qsctr_inc(int cpu) +void rcu_sched_qs(int cpu) { struct rcu_dyntick_sched *rdssp = &per_cpu(rcu_dyntick_sched, cpu); @@ -967,12 +967,12 @@ void rcu_check_callbacks(int cpu, int user) * If this CPU took its interrupt from user mode or from the * idle loop, and this is not a nested interrupt, then * this CPU has to have exited all prior preept-disable - * sections of code. So increment the counter to note this. + * sections of code. So invoke rcu_sched_qs() to note this. * * The memory barrier is needed to handle the case where * writes from a preempt-disable section of code get reordered * into schedule() by this CPU's write buffer. So the memory - * barrier makes sure that the rcu_qsctr_inc() is seen by other + * barrier makes sure that the rcu_sched_qs() is seen by other * CPUs to happen after any such write. */ @@ -980,7 +980,7 @@ void rcu_check_callbacks(int cpu, int user) (idle_cpu(cpu) && !in_softirq() && hardirq_count() <= (1 << HARDIRQ_SHIFT))) { smp_mb(); /* Guard against aggressive schedule(). */ - rcu_qsctr_inc(cpu); + rcu_sched_qs(cpu); } rcu_check_mb(cpu); diff --git a/kernel/rcutree.c b/kernel/rcutree.c index a162f859dd32..4d71d4e8b5a8 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -74,26 +74,25 @@ EXPORT_SYMBOL_GPL(rcu_lock_map); .n_force_qs_ngp = 0, \ } -struct rcu_state rcu_state = RCU_STATE_INITIALIZER(rcu_state); -DEFINE_PER_CPU(struct rcu_data, rcu_data); +struct rcu_state rcu_sched_state = RCU_STATE_INITIALIZER(rcu_sched_state); +DEFINE_PER_CPU(struct rcu_data, rcu_sched_data); struct rcu_state rcu_bh_state = RCU_STATE_INITIALIZER(rcu_bh_state); DEFINE_PER_CPU(struct rcu_data, rcu_bh_data); /* - * Increment the quiescent state counter. - * The counter is a bit degenerated: We do not need to know + * Note a quiescent state. Because we do not need to know * how many quiescent states passed, just if there was at least - * one since the start of the grace period. Thus just a flag. + * one since the start of the grace period, this just sets a flag. */ -void rcu_qsctr_inc(int cpu) +void rcu_sched_qs(int cpu) { - struct rcu_data *rdp = &per_cpu(rcu_data, cpu); + struct rcu_data *rdp = &per_cpu(rcu_sched_data, cpu); rdp->passed_quiesc = 1; rdp->passed_quiesc_completed = rdp->completed; } -void rcu_bh_qsctr_inc(int cpu) +void rcu_bh_qs(int cpu) { struct rcu_data *rdp = &per_cpu(rcu_bh_data, cpu); rdp->passed_quiesc = 1; @@ -113,12 +112,22 @@ static int qlowmark = 100; /* Once only this many pending, use blimit. */ static void force_quiescent_state(struct rcu_state *rsp, int relaxed); +/* + * Return the number of RCU-sched batches processed thus far for debug & stats. + */ +long rcu_batches_completed_sched(void) +{ + return rcu_sched_state.completed; +} +EXPORT_SYMBOL_GPL(rcu_batches_completed_sched); + /* * Return the number of RCU batches processed thus far for debug & stats. + * @@@ placeholder, maps to rcu_batches_completed_sched(). */ long rcu_batches_completed(void) { - return rcu_state.completed; + return rcu_batches_completed_sched(); } EXPORT_SYMBOL_GPL(rcu_batches_completed); @@ -310,7 +319,7 @@ void rcu_irq_exit(void) WARN_ON_RATELIMIT(rdtp->dynticks & 0x1, &rcu_rs); /* If the interrupt queued a callback, get out of dyntick mode. */ - if (__get_cpu_var(rcu_data).nxtlist || + if (__get_cpu_var(rcu_sched_data).nxtlist || __get_cpu_var(rcu_bh_data).nxtlist) set_need_resched(); } @@ -847,7 +856,7 @@ static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp) /* * Move callbacks from the outgoing CPU to the running CPU. * Note that the outgoing CPU is now quiscent, so it is now - * (uncharacteristically) safe to access it rcu_data structure. + * (uncharacteristically) safe to access its rcu_data structure. * Note also that we must carefully retain the order of the * outgoing CPU's callbacks in order for rcu_barrier() to work * correctly. Finally, note that we start all the callbacks @@ -878,7 +887,7 @@ static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp) */ static void rcu_offline_cpu(int cpu) { - __rcu_offline_cpu(cpu, &rcu_state); + __rcu_offline_cpu(cpu, &rcu_sched_state); __rcu_offline_cpu(cpu, &rcu_bh_state); } @@ -973,17 +982,16 @@ void rcu_check_callbacks(int cpu, int user) * Get here if this CPU took its interrupt from user * mode or from the idle loop, and if this is not a * nested interrupt. In this case, the CPU is in - * a quiescent state, so count it. + * a quiescent state, so note it. * * No memory barrier is required here because both - * rcu_qsctr_inc() and rcu_bh_qsctr_inc() reference - * only CPU-local variables that other CPUs neither - * access nor modify, at least not while the corresponding - * CPU is online. + * rcu_sched_qs() and rcu_bh_qs() reference only CPU-local + * variables that other CPUs neither access nor modify, + * at least not while the corresponding CPU is online. */ - rcu_qsctr_inc(cpu); - rcu_bh_qsctr_inc(cpu); + rcu_sched_qs(cpu); + rcu_bh_qs(cpu); } else if (!in_softirq()) { @@ -991,10 +999,10 @@ void rcu_check_callbacks(int cpu, int user) * Get here if this CPU did not take its interrupt from * softirq, in other words, if it is not interrupting * a rcu_bh read-side critical section. This is an _bh - * critical section, so count it. + * critical section, so note it. */ - rcu_bh_qsctr_inc(cpu); + rcu_bh_qs(cpu); } raise_softirq(RCU_SOFTIRQ); } @@ -1174,7 +1182,8 @@ static void rcu_process_callbacks(struct softirq_action *unused) */ smp_mb(); /* See above block comment. */ - __rcu_process_callbacks(&rcu_state, &__get_cpu_var(rcu_data)); + __rcu_process_callbacks(&rcu_sched_state, + &__get_cpu_var(rcu_sched_data)); __rcu_process_callbacks(&rcu_bh_state, &__get_cpu_var(rcu_bh_data)); /* @@ -1231,14 +1240,25 @@ __call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu), } /* - * Queue an RCU callback for invocation after a grace period. + * Queue an RCU-sched callback for invocation after a grace period. + */ +void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) +{ + __call_rcu(head, func, &rcu_sched_state); +} +EXPORT_SYMBOL_GPL(call_rcu_sched); + +/* + * @@@ Queue an RCU callback for invocation after a grace period. + * @@@ Placeholder pending rcutree_plugin.h. */ void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) { - __call_rcu(head, func, &rcu_state); + call_rcu_sched(head, func); } EXPORT_SYMBOL_GPL(call_rcu); + /* * Queue an RCU for invocation after a quicker grace period. */ @@ -1311,7 +1331,7 @@ static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp) */ int rcu_pending(int cpu) { - return __rcu_pending(&rcu_state, &per_cpu(rcu_data, cpu)) || + return __rcu_pending(&rcu_sched_state, &per_cpu(rcu_sched_data, cpu)) || __rcu_pending(&rcu_bh_state, &per_cpu(rcu_bh_data, cpu)); } @@ -1324,7 +1344,7 @@ int rcu_pending(int cpu) int rcu_needs_cpu(int cpu) { /* RCU callbacks either ready or pending? */ - return per_cpu(rcu_data, cpu).nxtlist || + return per_cpu(rcu_sched_data, cpu).nxtlist || per_cpu(rcu_bh_data, cpu).nxtlist; } @@ -1418,7 +1438,7 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp) static void __cpuinit rcu_online_cpu(int cpu) { - rcu_init_percpu_data(cpu, &rcu_state); + rcu_init_percpu_data(cpu, &rcu_sched_state); rcu_init_percpu_data(cpu, &rcu_bh_state); } @@ -1545,10 +1565,10 @@ void __init __rcu_init(void) #ifdef CONFIG_RCU_CPU_STALL_DETECTOR printk(KERN_INFO "RCU-based detection of stalled CPUs is enabled.\n"); #endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ - rcu_init_one(&rcu_state); - RCU_DATA_PTR_INIT(&rcu_state, rcu_data); + rcu_init_one(&rcu_sched_state); + RCU_DATA_PTR_INIT(&rcu_sched_state, rcu_sched_data); for_each_possible_cpu(i) - rcu_boot_init_percpu_data(i, &rcu_state); + rcu_boot_init_percpu_data(i, &rcu_sched_state); rcu_init_one(&rcu_bh_state); RCU_DATA_PTR_INIT(&rcu_bh_state, rcu_bh_data); for_each_possible_cpu(i) diff --git a/kernel/rcutree.h b/kernel/rcutree.h index 7cc830a1c44a..0024e5ddcc68 100644 --- a/kernel/rcutree.h +++ b/kernel/rcutree.h @@ -238,8 +238,8 @@ struct rcu_state { /* * RCU implementation internal declarations: */ -extern struct rcu_state rcu_state; -DECLARE_PER_CPU(struct rcu_data, rcu_data); +extern struct rcu_state rcu_sched_state; +DECLARE_PER_CPU(struct rcu_data, rcu_sched_data); extern struct rcu_state rcu_bh_state; DECLARE_PER_CPU(struct rcu_data, rcu_bh_data); diff --git a/kernel/rcutree_trace.c b/kernel/rcutree_trace.c index 0cb52b887758..236c0504fee2 100644 --- a/kernel/rcutree_trace.c +++ b/kernel/rcutree_trace.c @@ -77,8 +77,8 @@ static void print_one_rcu_data(struct seq_file *m, struct rcu_data *rdp) static int show_rcudata(struct seq_file *m, void *unused) { - seq_puts(m, "rcu:\n"); - PRINT_RCU_DATA(rcu_data, print_one_rcu_data, m); + seq_puts(m, "rcu_sched:\n"); + PRINT_RCU_DATA(rcu_sched_data, print_one_rcu_data, m); seq_puts(m, "rcu_bh:\n"); PRINT_RCU_DATA(rcu_bh_data, print_one_rcu_data, m); return 0; @@ -125,8 +125,8 @@ static int show_rcudata_csv(struct seq_file *m, void *unused) seq_puts(m, "\"dt\",\"dt nesting\",\"dn\",\"df\","); #endif /* #ifdef CONFIG_NO_HZ */ seq_puts(m, "\"of\",\"ri\",\"ql\",\"b\"\n"); - seq_puts(m, "\"rcu:\"\n"); - PRINT_RCU_DATA(rcu_data, print_one_rcu_data_csv, m); + seq_puts(m, "\"rcu_sched:\"\n"); + PRINT_RCU_DATA(rcu_sched_data, print_one_rcu_data_csv, m); seq_puts(m, "\"rcu_bh:\"\n"); PRINT_RCU_DATA(rcu_bh_data, print_one_rcu_data_csv, m); return 0; @@ -172,8 +172,8 @@ static void print_one_rcu_state(struct seq_file *m, struct rcu_state *rsp) static int show_rcuhier(struct seq_file *m, void *unused) { - seq_puts(m, "rcu:\n"); - print_one_rcu_state(m, &rcu_state); + seq_puts(m, "rcu_sched:\n"); + print_one_rcu_state(m, &rcu_sched_state); seq_puts(m, "rcu_bh:\n"); print_one_rcu_state(m, &rcu_bh_state); return 0; @@ -194,8 +194,8 @@ static struct file_operations rcuhier_fops = { static int show_rcugp(struct seq_file *m, void *unused) { - seq_printf(m, "rcu: completed=%ld gpnum=%ld\n", - rcu_state.completed, rcu_state.gpnum); + seq_printf(m, "rcu_sched: completed=%ld gpnum=%ld\n", + rcu_sched_state.completed, rcu_sched_state.gpnum); seq_printf(m, "rcu_bh: completed=%ld gpnum=%ld\n", rcu_bh_state.completed, rcu_bh_state.gpnum); return 0; @@ -244,8 +244,8 @@ static void print_rcu_pendings(struct seq_file *m, struct rcu_state *rsp) static int show_rcu_pending(struct seq_file *m, void *unused) { - seq_puts(m, "rcu:\n"); - print_rcu_pendings(m, &rcu_state); + seq_puts(m, "rcu_sched:\n"); + print_rcu_pendings(m, &rcu_sched_state); seq_puts(m, "rcu_bh:\n"); print_rcu_pendings(m, &rcu_bh_state); return 0; diff --git a/kernel/sched.c b/kernel/sched.c index cda8b81f8801..c9beca67a53e 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -5325,7 +5325,7 @@ need_resched: preempt_disable(); cpu = smp_processor_id(); rq = cpu_rq(cpu); - rcu_qsctr_inc(cpu); + rcu_sched_qs(cpu); prev = rq->curr; switch_count = &prev->nivcsw; diff --git a/kernel/softirq.c b/kernel/softirq.c index eb5e131a0485..7db25067cd2d 100644 --- a/kernel/softirq.c +++ b/kernel/softirq.c @@ -227,7 +227,7 @@ restart: preempt_count() = prev_count; } - rcu_bh_qsctr_inc(cpu); + rcu_bh_qs(cpu); } h++; pending >>= 1; @@ -721,7 +721,7 @@ static int ksoftirqd(void * __bind_cpu) preempt_enable_no_resched(); cond_resched(); preempt_disable(); - rcu_qsctr_inc((long)__bind_cpu); + rcu_sched_qs((long)__bind_cpu); } preempt_enable(); set_current_state(TASK_INTERRUPTIBLE); -- cgit v1.2.3-59-g8ed1b From bc33f24bdca8b6e97376e3a182ab69e6cdefa989 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Sat, 22 Aug 2009 13:56:47 -0700 Subject: rcu: Consolidate sparse and lockdep declarations in include/linux/rcupdate.h Signed-off-by: Paul E. McKenney Cc: laijs@cn.fujitsu.com Cc: dipankar@in.ibm.com Cc: akpm@linux-foundation.org Cc: mathieu.desnoyers@polymtl.ca Cc: josht@linux.vnet.ibm.com Cc: dvhltc@us.ibm.com Cc: niv@us.ibm.com Cc: peterz@infradead.org Cc: rostedt@goodmis.org LKML-Reference: <12509746132349-git-send-email-> Signed-off-by: Ingo Molnar --- include/linux/rcupdate.h | 46 ++++++++++++++++++++++++++++++++++++++++++---- include/linux/rcupreempt.h | 4 ++-- include/linux/rcutree.h | 18 ------------------ 3 files changed, 44 insertions(+), 24 deletions(-) (limited to 'include') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index e920f0fd59d8..9d85ee19492a 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -80,6 +80,16 @@ extern int rcu_scheduler_active; (ptr)->next = NULL; (ptr)->func = NULL; \ } while (0) +#ifdef CONFIG_DEBUG_LOCK_ALLOC +extern struct lockdep_map rcu_lock_map; +# define rcu_read_acquire() \ + lock_acquire(&rcu_lock_map, 0, 0, 2, 1, NULL, _THIS_IP_) +# define rcu_read_release() lock_release(&rcu_lock_map, 1, _THIS_IP_) +#else +# define rcu_read_acquire() do { } while (0) +# define rcu_read_release() do { } while (0) +#endif + /** * rcu_read_lock - mark the beginning of an RCU read-side critical section. * @@ -109,7 +119,12 @@ extern int rcu_scheduler_active; * * It is illegal to block while in an RCU read-side critical section. */ -#define rcu_read_lock() __rcu_read_lock() +static inline void rcu_read_lock(void) +{ + __rcu_read_lock(); + __acquire(RCU); + rcu_read_acquire(); +} /** * rcu_read_unlock - marks the end of an RCU read-side critical section. @@ -126,7 +141,12 @@ extern int rcu_scheduler_active; * used as well. RCU does not care how the writers keep out of each * others' way, as long as they do so. */ -#define rcu_read_unlock() __rcu_read_unlock() +static inline void rcu_read_unlock(void) +{ + rcu_read_release(); + __release(RCU); + __rcu_read_unlock(); +} /** * rcu_read_lock_bh - mark the beginning of a softirq-only RCU critical section @@ -139,14 +159,24 @@ extern int rcu_scheduler_active; * can use just rcu_read_lock(). * */ -#define rcu_read_lock_bh() __rcu_read_lock_bh() +static inline void rcu_read_lock_bh(void) +{ + __rcu_read_lock_bh(); + __acquire(RCU_BH); + rcu_read_acquire(); +} /* * rcu_read_unlock_bh - marks the end of a softirq-only RCU critical section * * See rcu_read_lock_bh() for more information. */ -#define rcu_read_unlock_bh() __rcu_read_unlock_bh() +static inline void rcu_read_unlock_bh(void) +{ + rcu_read_release(); + __release(RCU_BH); + __rcu_read_unlock_bh(); +} /** * rcu_read_lock_sched - mark the beginning of a RCU-classic critical section @@ -160,10 +190,14 @@ extern int rcu_scheduler_active; static inline void rcu_read_lock_sched(void) { preempt_disable(); + __acquire(RCU_SCHED); + rcu_read_acquire(); } static inline void rcu_read_lock_sched_notrace(void) { preempt_disable_notrace(); + __acquire(RCU_SCHED); + rcu_read_acquire(); } /* @@ -173,10 +207,14 @@ static inline void rcu_read_lock_sched_notrace(void) */ static inline void rcu_read_unlock_sched(void) { + rcu_read_release(); + __release(RCU_SCHED); preempt_enable(); } static inline void rcu_read_unlock_sched_notrace(void) { + rcu_read_release(); + __release(RCU_SCHED); preempt_enable_notrace(); } diff --git a/include/linux/rcupreempt.h b/include/linux/rcupreempt.h index 2963f080e48d..6c9dd9cf8b8e 100644 --- a/include/linux/rcupreempt.h +++ b/include/linux/rcupreempt.h @@ -64,8 +64,8 @@ static inline void rcu_bh_qs(int cpu) { } extern void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *head)); -extern void __rcu_read_lock(void) __acquires(RCU); -extern void __rcu_read_unlock(void) __releases(RCU); +extern void __rcu_read_lock(void); +extern void __rcu_read_unlock(void); extern int rcu_pending(int cpu); extern int rcu_needs_cpu(int cpu); diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h index a0852d0d915b..8a0222ce3b13 100644 --- a/include/linux/rcutree.h +++ b/include/linux/rcutree.h @@ -36,38 +36,20 @@ extern void rcu_bh_qs(int cpu); extern int rcu_pending(int cpu); extern int rcu_needs_cpu(int cpu); -#ifdef CONFIG_DEBUG_LOCK_ALLOC -extern struct lockdep_map rcu_lock_map; -# define rcu_read_acquire() \ - lock_acquire(&rcu_lock_map, 0, 0, 2, 1, NULL, _THIS_IP_) -# define rcu_read_release() lock_release(&rcu_lock_map, 1, _THIS_IP_) -#else -# define rcu_read_acquire() do { } while (0) -# define rcu_read_release() do { } while (0) -#endif - static inline void __rcu_read_lock(void) { preempt_disable(); - __acquire(RCU); - rcu_read_acquire(); } static inline void __rcu_read_unlock(void) { - rcu_read_release(); - __release(RCU); preempt_enable(); } static inline void __rcu_read_lock_bh(void) { local_bh_disable(); - __acquire(RCU_BH); - rcu_read_acquire(); } static inline void __rcu_read_unlock_bh(void) { - rcu_read_release(); - __release(RCU_BH); local_bh_enable(); } -- cgit v1.2.3-59-g8ed1b From a157229cabd6dd8cfa82525fc9bf730c94cc9ac2 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Sat, 22 Aug 2009 13:56:51 -0700 Subject: rcu: Simplify rcu_pending()/rcu_check_callbacks() API All calls from outside RCU are of the form: if (rcu_pending(cpu)) rcu_check_callbacks(cpu, user); This is silly, instead we put a call to rcu_pending() in rcu_check_callbacks(), and then make the outside calls be to rcu_check_callbacks(). This cuts down on the code a bit and also gives the compiler a better chance of optimizing. Signed-off-by: Paul E. McKenney Cc: laijs@cn.fujitsu.com Cc: dipankar@in.ibm.com Cc: akpm@linux-foundation.org Cc: mathieu.desnoyers@polymtl.ca Cc: josht@linux.vnet.ibm.com Cc: dvhltc@us.ibm.com Cc: niv@us.ibm.com Cc: peterz@infradead.org Cc: rostedt@goodmis.org LKML-Reference: <125097461311-git-send-email-> Signed-off-by: Ingo Molnar --- arch/ia64/xen/time.c | 3 +-- include/linux/rcupreempt.h | 1 - include/linux/rcutree.h | 1 - kernel/rcupreempt.c | 10 ++++++++-- kernel/rcutree.c | 5 ++++- kernel/timer.c | 3 +-- 6 files changed, 14 insertions(+), 9 deletions(-) (limited to 'include') diff --git a/arch/ia64/xen/time.c b/arch/ia64/xen/time.c index fb8332690179..dbeadb9c8e20 100644 --- a/arch/ia64/xen/time.c +++ b/arch/ia64/xen/time.c @@ -133,8 +133,7 @@ consider_steal_time(unsigned long new_itm) account_idle_ticks(blocked); run_local_timers(); - if (rcu_pending(cpu)) - rcu_check_callbacks(cpu, user_mode(get_irq_regs())); + rcu_check_callbacks(cpu, user_mode(get_irq_regs())); scheduler_tick(); run_posix_cpu_timers(p); diff --git a/include/linux/rcupreempt.h b/include/linux/rcupreempt.h index 6c9dd9cf8b8e..aff4772fb49e 100644 --- a/include/linux/rcupreempt.h +++ b/include/linux/rcupreempt.h @@ -66,7 +66,6 @@ extern void call_rcu_sched(struct rcu_head *head, extern void __rcu_read_lock(void); extern void __rcu_read_unlock(void); -extern int rcu_pending(int cpu); extern int rcu_needs_cpu(int cpu); #define __rcu_read_lock_bh() { rcu_read_lock(); local_bh_disable(); } diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h index 8a0222ce3b13..c739d90f5e68 100644 --- a/include/linux/rcutree.h +++ b/include/linux/rcutree.h @@ -33,7 +33,6 @@ extern void rcu_sched_qs(int cpu); extern void rcu_bh_qs(int cpu); -extern int rcu_pending(int cpu); extern int rcu_needs_cpu(int cpu); static inline void __rcu_read_lock(void) diff --git a/kernel/rcupreempt.c b/kernel/rcupreempt.c index 7d777c9f394c..0053ce56e326 100644 --- a/kernel/rcupreempt.c +++ b/kernel/rcupreempt.c @@ -159,6 +159,8 @@ static DEFINE_PER_CPU_SHARED_ALIGNED(struct rcu_dyntick_sched, rcu_dyntick_sched .dynticks = 1, }; +static int rcu_pending(int cpu); + void rcu_sched_qs(int cpu) { struct rcu_dyntick_sched *rdssp = &per_cpu(rcu_dyntick_sched, cpu); @@ -961,7 +963,10 @@ static void rcu_check_mb(int cpu) void rcu_check_callbacks(int cpu, int user) { unsigned long flags; - struct rcu_data *rdp = RCU_DATA_CPU(cpu); + struct rcu_data *rdp; + + if (!rcu_pending(cpu)) + return; /* if nothing for RCU to do. */ /* * If this CPU took its interrupt from user mode or from the @@ -976,6 +981,7 @@ void rcu_check_callbacks(int cpu, int user) * CPUs to happen after any such write. */ + rdp = RCU_DATA_CPU(cpu); if (user || (idle_cpu(cpu) && !in_softirq() && hardirq_count() <= (1 << HARDIRQ_SHIFT))) { @@ -1382,7 +1388,7 @@ int rcu_needs_cpu(int cpu) rdp->waitschedlist != NULL); } -int rcu_pending(int cpu) +static int rcu_pending(int cpu) { struct rcu_data *rdp = RCU_DATA_CPU(cpu); diff --git a/kernel/rcutree.c b/kernel/rcutree.c index 7c515082ae84..4ce3adcfa94d 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -111,6 +111,7 @@ static int qhimark = 10000; /* If this many pending, ignore blimit. */ static int qlowmark = 100; /* Once only this many pending, use blimit. */ static void force_quiescent_state(struct rcu_state *rsp, int relaxed); +static int rcu_pending(int cpu); /* * Return the number of RCU-sched batches processed thus far for debug & stats. @@ -974,6 +975,8 @@ static void rcu_do_batch(struct rcu_data *rdp) */ void rcu_check_callbacks(int cpu, int user) { + if (!rcu_pending(cpu)) + return; /* if nothing for RCU to do. */ if (user || (idle_cpu(cpu) && rcu_scheduler_active && !in_softirq() && hardirq_count() <= (1 << HARDIRQ_SHIFT))) { @@ -1329,7 +1332,7 @@ static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp) * by the current CPU, returning 1 if so. This function is part of the * RCU implementation; it is -not- an exported member of the RCU API. */ -int rcu_pending(int cpu) +static int rcu_pending(int cpu) { return __rcu_pending(&rcu_sched_state, &per_cpu(rcu_sched_data, cpu)) || __rcu_pending(&rcu_bh_state, &per_cpu(rcu_bh_data, cpu)); diff --git a/kernel/timer.c b/kernel/timer.c index a7f07d5a6241..a3d25f415019 100644 --- a/kernel/timer.c +++ b/kernel/timer.c @@ -1156,8 +1156,7 @@ void update_process_times(int user_tick) /* Note: this timer irq context must be accounted for as well. */ account_process_tick(p, user_tick); run_local_timers(); - if (rcu_pending(cpu)) - rcu_check_callbacks(cpu, user_tick); + rcu_check_callbacks(cpu, user_tick); printk_tick(); scheduler_tick(); run_posix_cpu_timers(p); -- cgit v1.2.3-59-g8ed1b From f41d911f8c49a5d65c86504c19e8204bb605c4fd Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Sat, 22 Aug 2009 13:56:52 -0700 Subject: rcu: Merge preemptable-RCU functionality into hierarchical RCU Create a kernel/rcutree_plugin.h file that contains definitions for preemptable RCU (or, under the #else branch of the #ifdef, empty definitions for the classic non-preemptable semantics). These definitions fit into plugins defined in kernel/rcutree.c for this purpose. This variant of preemptable RCU uses a new algorithm whose read-side expense is roughly that of classic hierarchical RCU under CONFIG_PREEMPT. This new algorithm's update-side expense is similar to that of classic hierarchical RCU, and, in absence of read-side preemption or blocking, is exactly that of classic hierarchical RCU. Perhaps more important, this new algorithm has a much simpler implementation, saving well over 1,000 lines of code compared to mainline's implementation of preemptable RCU, which will hopefully be retired in favor of this new algorithm. The simplifications are obtained by maintaining per-task nesting state for running tasks, and using a simple lock-protected algorithm to handle accounting when tasks block within RCU read-side critical sections, making use of lessons learned while creating numerous user-level RCU implementations over the past 18 months. Signed-off-by: Paul E. McKenney Cc: laijs@cn.fujitsu.com Cc: dipankar@in.ibm.com Cc: akpm@linux-foundation.org Cc: mathieu.desnoyers@polymtl.ca Cc: josht@linux.vnet.ibm.com Cc: dvhltc@us.ibm.com Cc: niv@us.ibm.com Cc: peterz@infradead.org Cc: rostedt@goodmis.org LKML-Reference: <12509746134003-git-send-email-> Signed-off-by: Ingo Molnar --- include/linux/init_task.h | 15 ++ include/linux/rcupdate.h | 2 +- include/linux/rcupreempt.h | 4 + include/linux/rcutree.h | 16 ++ include/linux/sched.h | 37 ++++ init/Kconfig | 22 ++- kernel/Makefile | 1 + kernel/exit.c | 1 + kernel/fork.c | 5 +- kernel/rcutree.c | 135 +++++++++----- kernel/rcutree.h | 9 + kernel/rcutree_plugin.h | 447 +++++++++++++++++++++++++++++++++++++++++++++ kernel/rcutree_trace.c | 20 ++ lib/Kconfig.debug | 2 +- 14 files changed, 661 insertions(+), 55 deletions(-) create mode 100644 kernel/rcutree_plugin.h (limited to 'include') diff --git a/include/linux/init_task.h b/include/linux/init_task.h index 7fc01b13be43..971a968831bf 100644 --- a/include/linux/init_task.h +++ b/include/linux/init_task.h @@ -94,6 +94,20 @@ extern struct group_info init_groups; # define CAP_INIT_BSET CAP_INIT_EFF_SET #endif +#ifdef CONFIG_PREEMPT_RCU +#define INIT_TASK_RCU_PREEMPT(tsk) \ + .rcu_read_lock_nesting = 0, \ + .rcu_flipctr_idx = 0, +#elif defined(CONFIG_TREE_PREEMPT_RCU) +#define INIT_TASK_RCU_PREEMPT(tsk) \ + .rcu_read_lock_nesting = 0, \ + .rcu_read_unlock_special = 0, \ + .rcu_blocked_cpu = -1, \ + .rcu_node_entry = LIST_HEAD_INIT(tsk.rcu_node_entry), +#else +#define INIT_TASK_RCU_PREEMPT(tsk) +#endif + extern struct cred init_cred; #ifdef CONFIG_PERF_COUNTERS @@ -173,6 +187,7 @@ extern struct cred init_cred; INIT_LOCKDEP \ INIT_FTRACE_GRAPH \ INIT_TRACE_RECURSION \ + INIT_TASK_RCU_PREEMPT(tsk) \ } diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 9d85ee19492a..26892f5e7bd8 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -66,7 +66,7 @@ extern void rcu_scheduler_starting(void); extern int rcu_needs_cpu(int cpu); extern int rcu_scheduler_active; -#if defined(CONFIG_TREE_RCU) +#if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU) #include #elif defined(CONFIG_PREEMPT_RCU) #include diff --git a/include/linux/rcupreempt.h b/include/linux/rcupreempt.h index aff4772fb49e..a42ab88e9210 100644 --- a/include/linux/rcupreempt.h +++ b/include/linux/rcupreempt.h @@ -98,6 +98,10 @@ static inline long rcu_batches_completed_bh(void) return rcu_batches_completed(); } +static inline void exit_rcu(void) +{ +} + #ifdef CONFIG_RCU_TRACE struct rcupreempt_trace; extern long *rcupreempt_flipctr(int cpu); diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h index c739d90f5e68..a89307717825 100644 --- a/include/linux/rcutree.h +++ b/include/linux/rcutree.h @@ -35,14 +35,30 @@ extern void rcu_bh_qs(int cpu); extern int rcu_needs_cpu(int cpu); +#ifdef CONFIG_TREE_PREEMPT_RCU + +extern void __rcu_read_lock(void); +extern void __rcu_read_unlock(void); +extern void exit_rcu(void); + +#else /* #ifdef CONFIG_TREE_PREEMPT_RCU */ + static inline void __rcu_read_lock(void) { preempt_disable(); } + static inline void __rcu_read_unlock(void) { preempt_enable(); } + +static inline void exit_rcu(void) +{ +} + +#endif /* #else #ifdef CONFIG_TREE_PREEMPT_RCU */ + static inline void __rcu_read_lock_bh(void) { local_bh_disable(); diff --git a/include/linux/sched.h b/include/linux/sched.h index 3ab08e4bb6b8..d7f98f637a2a 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1210,6 +1210,13 @@ struct task_struct { int rcu_flipctr_idx; #endif /* #ifdef CONFIG_PREEMPT_RCU */ +#ifdef CONFIG_TREE_PREEMPT_RCU + int rcu_read_lock_nesting; + char rcu_read_unlock_special; + int rcu_blocked_cpu; + struct list_head rcu_node_entry; +#endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */ + #if defined(CONFIG_SCHEDSTATS) || defined(CONFIG_TASK_DELAY_ACCT) struct sched_info sched_info; #endif @@ -1723,6 +1730,36 @@ extern cputime_t task_gtime(struct task_struct *p); #define tsk_used_math(p) ((p)->flags & PF_USED_MATH) #define used_math() tsk_used_math(current) +#ifdef CONFIG_TREE_PREEMPT_RCU + +#define RCU_READ_UNLOCK_BLOCKED (1 << 0) /* blocked while in RCU read-side. */ +#define RCU_READ_UNLOCK_NEED_QS (1 << 1) /* RCU core needs CPU response. */ +#define RCU_READ_UNLOCK_GOT_QS (1 << 2) /* CPU has responded to RCU core. */ + +static inline void rcu_copy_process(struct task_struct *p) +{ + p->rcu_read_lock_nesting = 0; + p->rcu_read_unlock_special = 0; + p->rcu_blocked_cpu = -1; + INIT_LIST_HEAD(&p->rcu_node_entry); +} + +#elif defined(CONFIG_PREEMPT_RCU) + +static inline void rcu_copy_process(struct task_struct *p) +{ + p->rcu_read_lock_nesting = 0; + p->rcu_flipctr_idx = 0; +} + +#else + +static inline void rcu_copy_process(struct task_struct *p) +{ +} + +#endif + #ifdef CONFIG_SMP extern int set_cpus_allowed_ptr(struct task_struct *p, const struct cpumask *new_mask); diff --git a/init/Kconfig b/init/Kconfig index 25373cf32672..f88da2d1c1fb 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -335,11 +335,20 @@ config PREEMPT_RCU now-naive assumptions about each RCU read-side critical section remaining on a given CPU through its execution. +config TREE_PREEMPT_RCU + bool "Preemptable tree-based hierarchical RCU" + depends on 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. + endchoice config RCU_TRACE bool "Enable tracing for RCU" - depends on TREE_RCU || PREEMPT_RCU + depends on TREE_RCU || PREEMPT_RCU || TREE_PREEMPT_RCU help This option provides tracing in RCU which presents stats in debugfs for debugging RCU implementation. @@ -351,7 +360,7 @@ config RCU_FANOUT int "Tree-based hierarchical RCU fanout value" range 2 64 if 64BIT range 2 32 if !64BIT - depends on TREE_RCU + depends on TREE_RCU || TREE_PREEMPT_RCU default 64 if 64BIT default 32 if !64BIT help @@ -366,7 +375,7 @@ config RCU_FANOUT config RCU_FANOUT_EXACT bool "Disable tree-based hierarchical RCU auto-balancing" - depends on TREE_RCU + depends on TREE_RCU || TREE_PREEMPT_RCU default n help This option forces use of the exact RCU_FANOUT value specified, @@ -379,11 +388,12 @@ config RCU_FANOUT_EXACT Say N if unsure. config TREE_RCU_TRACE - def_bool RCU_TRACE && TREE_RCU + def_bool RCU_TRACE && ( TREE_RCU || TREE_PREEMPT_RCU ) select DEBUG_FS help - This option provides tracing for the TREE_RCU implementation, - permitting Makefile to trivially select kernel/rcutree_trace.c. + This option provides tracing for the TREE_RCU and + TREE_PREEMPT_RCU implementations, permitting Makefile to + trivially select kernel/rcutree_trace.c. config PREEMPT_RCU_TRACE def_bool RCU_TRACE && PREEMPT_RCU diff --git a/kernel/Makefile b/kernel/Makefile index 2419c9d43918..1a38b4789dda 100644 --- a/kernel/Makefile +++ b/kernel/Makefile @@ -81,6 +81,7 @@ obj-$(CONFIG_GENERIC_HARDIRQS) += irq/ obj-$(CONFIG_SECCOMP) += seccomp.o obj-$(CONFIG_RCU_TORTURE_TEST) += rcutorture.o obj-$(CONFIG_TREE_RCU) += rcutree.o +obj-$(CONFIG_TREE_PREEMPT_RCU) += rcutree.o obj-$(CONFIG_PREEMPT_RCU) += rcupreempt.o obj-$(CONFIG_TREE_RCU_TRACE) += rcutree_trace.o obj-$(CONFIG_PREEMPT_RCU_TRACE) += rcupreempt_trace.o diff --git a/kernel/exit.c b/kernel/exit.c index 869dc221733e..263f95ed7201 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -1010,6 +1010,7 @@ NORET_TYPE void do_exit(long code) __free_pipe_info(tsk->splice_pipe); preempt_disable(); + exit_rcu(); /* causes final put_task_struct in finish_task_switch(). */ tsk->state = TASK_DEAD; schedule(); diff --git a/kernel/fork.c b/kernel/fork.c index 021e1138556e..642e8b5edf00 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1022,10 +1022,7 @@ static struct task_struct *copy_process(unsigned long clone_flags, copy_flags(clone_flags, p); INIT_LIST_HEAD(&p->children); INIT_LIST_HEAD(&p->sibling); -#ifdef CONFIG_PREEMPT_RCU - p->rcu_read_lock_nesting = 0; - p->rcu_flipctr_idx = 0; -#endif /* #ifdef CONFIG_PREEMPT_RCU */ + rcu_copy_process(p); p->vfork_done = NULL; spin_lock_init(&p->alloc_lock); diff --git a/kernel/rcutree.c b/kernel/rcutree.c index 4ce3adcfa94d..cc0255714075 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -80,6 +80,21 @@ DEFINE_PER_CPU(struct rcu_data, rcu_sched_data); struct rcu_state rcu_bh_state = RCU_STATE_INITIALIZER(rcu_bh_state); DEFINE_PER_CPU(struct rcu_data, rcu_bh_data); +extern long rcu_batches_completed_sched(void); +static void cpu_quiet_msk(unsigned long mask, struct rcu_state *rsp, + struct rcu_node *rnp, unsigned long flags); +static void cpu_quiet_msk_finish(struct rcu_state *rsp, unsigned long flags); +static void __rcu_process_callbacks(struct rcu_state *rsp, + struct rcu_data *rdp); +static void __call_rcu(struct rcu_head *head, + void (*func)(struct rcu_head *rcu), + struct rcu_state *rsp); +static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp); +static void __cpuinit rcu_init_percpu_data(int cpu, struct rcu_state *rsp, + int preemptable); + +#include "rcutree_plugin.h" + /* * Note a quiescent state. Because we do not need to know * how many quiescent states passed, just if there was at least @@ -87,16 +102,27 @@ DEFINE_PER_CPU(struct rcu_data, rcu_bh_data); */ void rcu_sched_qs(int cpu) { - struct rcu_data *rdp = &per_cpu(rcu_sched_data, cpu); + unsigned long flags; + struct rcu_data *rdp; + + local_irq_save(flags); + rdp = &per_cpu(rcu_sched_data, cpu); rdp->passed_quiesc = 1; rdp->passed_quiesc_completed = rdp->completed; + rcu_preempt_qs(cpu); + local_irq_restore(flags); } void rcu_bh_qs(int cpu) { - struct rcu_data *rdp = &per_cpu(rcu_bh_data, cpu); + unsigned long flags; + struct rcu_data *rdp; + + local_irq_save(flags); + rdp = &per_cpu(rcu_bh_data, cpu); rdp->passed_quiesc = 1; rdp->passed_quiesc_completed = rdp->completed; + local_irq_restore(flags); } #ifdef CONFIG_NO_HZ @@ -122,16 +148,6 @@ long rcu_batches_completed_sched(void) } EXPORT_SYMBOL_GPL(rcu_batches_completed_sched); -/* - * Return the number of RCU batches processed thus far for debug & stats. - * @@@ placeholder, maps to rcu_batches_completed_sched(). - */ -long rcu_batches_completed(void) -{ - return rcu_batches_completed_sched(); -} -EXPORT_SYMBOL_GPL(rcu_batches_completed); - /* * Return the number of RCU BH batches processed thus far for debug & stats. */ @@ -193,6 +209,10 @@ static int rcu_implicit_offline_qs(struct rcu_data *rdp) return 1; } + /* If preemptable RCU, no point in sending reschedule IPI. */ + if (rdp->preemptable) + return 0; + /* The CPU is online, so send it a reschedule IPI. */ if (rdp->cpu != smp_processor_id()) smp_send_reschedule(rdp->cpu); @@ -473,6 +493,7 @@ static void print_other_cpu_stall(struct rcu_state *rsp) printk(KERN_ERR "INFO: RCU detected CPU stalls:"); for (; rnp_cur < rnp_end; rnp_cur++) { + rcu_print_task_stall(rnp); if (rnp_cur->qsmask == 0) continue; for (cpu = 0; cpu <= rnp_cur->grphi - rnp_cur->grplo; cpu++) @@ -685,6 +706,19 @@ rcu_process_gp_end(struct rcu_state *rsp, struct rcu_data *rdp) local_irq_restore(flags); } +/* + * Clean up after the prior grace period and let rcu_start_gp() start up + * the next grace period if one is needed. Note that the caller must + * hold rnp->lock, as required by rcu_start_gp(), which will release it. + */ +static void cpu_quiet_msk_finish(struct rcu_state *rsp, unsigned long flags) + __releases(rnp->lock) +{ + rsp->completed = rsp->gpnum; + rcu_process_gp_end(rsp, rsp->rda[smp_processor_id()]); + rcu_start_gp(rsp, flags); /* releases root node's rnp->lock. */ +} + /* * Similar to cpu_quiet(), for which it is a helper function. Allows * a group of CPUs to be quieted at one go, though all the CPUs in the @@ -706,7 +740,7 @@ cpu_quiet_msk(unsigned long mask, struct rcu_state *rsp, struct rcu_node *rnp, return; } rnp->qsmask &= ~mask; - if (rnp->qsmask != 0) { + if (rnp->qsmask != 0 || rcu_preempted_readers(rnp)) { /* Other bits still set at this level, so done. */ spin_unlock_irqrestore(&rnp->lock, flags); @@ -726,14 +760,10 @@ cpu_quiet_msk(unsigned long mask, struct rcu_state *rsp, struct rcu_node *rnp, /* * Get here if we are the last CPU to pass through a quiescent - * state for this grace period. Clean up and let rcu_start_gp() - * start up the next grace period if one is needed. Note that - * we still hold rnp->lock, as required by rcu_start_gp(), which - * will release it. + * state for this grace period. Invoke cpu_quiet_msk_finish() + * to clean up and start the next grace period if one is needed. */ - rsp->completed = rsp->gpnum; - rcu_process_gp_end(rsp, rsp->rda[smp_processor_id()]); - rcu_start_gp(rsp, flags); /* releases rnp->lock. */ + cpu_quiet_msk_finish(rsp, flags); /* releases rnp->lock. */ } /* @@ -840,11 +870,11 @@ static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp) spin_lock(&rnp->lock); /* irqs already disabled. */ rnp->qsmaskinit &= ~mask; if (rnp->qsmaskinit != 0) { - spin_unlock(&rnp->lock); /* irqs already disabled. */ + spin_unlock(&rnp->lock); /* irqs remain disabled. */ break; } mask = rnp->grpmask; - spin_unlock(&rnp->lock); /* irqs already disabled. */ + spin_unlock(&rnp->lock); /* irqs remain disabled. */ rnp = rnp->parent; } while (rnp != NULL); lastcomp = rsp->completed; @@ -1007,6 +1037,7 @@ void rcu_check_callbacks(int cpu, int user) rcu_bh_qs(cpu); } + rcu_preempt_check_callbacks(cpu); raise_softirq(RCU_SOFTIRQ); } @@ -1188,6 +1219,7 @@ static void rcu_process_callbacks(struct softirq_action *unused) __rcu_process_callbacks(&rcu_sched_state, &__get_cpu_var(rcu_sched_data)); __rcu_process_callbacks(&rcu_bh_state, &__get_cpu_var(rcu_bh_data)); + rcu_preempt_process_callbacks(); /* * Memory references from any later RCU read-side critical sections @@ -1251,17 +1283,6 @@ void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) } EXPORT_SYMBOL_GPL(call_rcu_sched); -/* - * @@@ Queue an RCU callback for invocation after a grace period. - * @@@ Placeholder pending rcutree_plugin.h. - */ -void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) -{ - call_rcu_sched(head, func); -} -EXPORT_SYMBOL_GPL(call_rcu); - - /* * Queue an RCU for invocation after a quicker grace period. */ @@ -1335,7 +1356,8 @@ static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp) static int rcu_pending(int cpu) { return __rcu_pending(&rcu_sched_state, &per_cpu(rcu_sched_data, cpu)) || - __rcu_pending(&rcu_bh_state, &per_cpu(rcu_bh_data, cpu)); + __rcu_pending(&rcu_bh_state, &per_cpu(rcu_bh_data, cpu)) || + rcu_preempt_pending(cpu); } /* @@ -1348,7 +1370,8 @@ int rcu_needs_cpu(int cpu) { /* RCU callbacks either ready or pending? */ return per_cpu(rcu_sched_data, cpu).nxtlist || - per_cpu(rcu_bh_data, cpu).nxtlist; + per_cpu(rcu_bh_data, cpu).nxtlist || + rcu_preempt_needs_cpu(cpu); } /* @@ -1383,7 +1406,7 @@ rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp) * that this CPU cannot possibly have any RCU callbacks in flight yet. */ static void __cpuinit -rcu_init_percpu_data(int cpu, struct rcu_state *rsp) +rcu_init_percpu_data(int cpu, struct rcu_state *rsp, int preemptable) { unsigned long flags; long lastcomp; @@ -1399,6 +1422,7 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp) rdp->passed_quiesc = 0; /* We could be racing with new GP, */ rdp->qs_pending = 1; /* so set up to respond to current GP. */ rdp->beenonline = 1; /* We have now been online. */ + rdp->preemptable = preemptable; rdp->passed_quiesc_completed = lastcomp - 1; rdp->blimit = blimit; spin_unlock(&rnp->lock); /* irqs remain disabled. */ @@ -1441,12 +1465,13 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp) static void __cpuinit rcu_online_cpu(int cpu) { - rcu_init_percpu_data(cpu, &rcu_sched_state); - rcu_init_percpu_data(cpu, &rcu_bh_state); + rcu_init_percpu_data(cpu, &rcu_sched_state, 0); + rcu_init_percpu_data(cpu, &rcu_bh_state, 0); + rcu_preempt_init_percpu_data(cpu); } /* - * Handle CPU online/offline notifcation events. + * Handle CPU online/offline notification events. */ int __cpuinit rcu_cpu_notify(struct notifier_block *self, unsigned long action, void *hcpu) @@ -1521,6 +1546,7 @@ static void __init rcu_init_one(struct rcu_state *rsp) rnp = rsp->level[i]; for (j = 0; j < rsp->levelcnt[i]; j++, rnp++) { spin_lock_init(&rnp->lock); + rnp->gpnum = 0; rnp->qsmask = 0; rnp->qsmaskinit = 0; rnp->grplo = j * cpustride; @@ -1538,13 +1564,16 @@ static void __init rcu_init_one(struct rcu_state *rsp) j / rsp->levelspread[i - 1]; } rnp->level = i; + INIT_LIST_HEAD(&rnp->blocked_tasks[0]); + INIT_LIST_HEAD(&rnp->blocked_tasks[1]); } } } /* - * Helper macro for __rcu_init(). To be used nowhere else! - * Assigns leaf node pointers into each CPU's rcu_data structure. + * Helper macro for __rcu_init() and __rcu_init_preempt(). To be used + * nowhere else! Assigns leaf node pointers into each CPU's rcu_data + * structure. */ #define RCU_INIT_FLAVOR(rsp, rcu_data) \ do { \ @@ -1560,18 +1589,38 @@ do { \ } \ } while (0) +#ifdef CONFIG_TREE_PREEMPT_RCU + +void __init __rcu_init_preempt(void) +{ + int i; /* All used by RCU_INIT_FLAVOR(). */ + int j; + struct rcu_node *rnp; + + RCU_INIT_FLAVOR(&rcu_preempt_state, rcu_preempt_data); +} + +#else /* #ifdef CONFIG_TREE_PREEMPT_RCU */ + +void __init __rcu_init_preempt(void) +{ +} + +#endif /* #else #ifdef CONFIG_TREE_PREEMPT_RCU */ + void __init __rcu_init(void) { - int i; /* All used by RCU_DATA_PTR_INIT(). */ + int i; /* All used by RCU_INIT_FLAVOR(). */ int j; struct rcu_node *rnp; - printk(KERN_INFO "Hierarchical RCU implementation.\n"); + rcu_bootup_announce(); #ifdef CONFIG_RCU_CPU_STALL_DETECTOR printk(KERN_INFO "RCU-based detection of stalled CPUs is enabled.\n"); #endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ RCU_INIT_FLAVOR(&rcu_sched_state, rcu_sched_data); RCU_INIT_FLAVOR(&rcu_bh_state, rcu_bh_data); + __rcu_init_preempt(); open_softirq(RCU_SOFTIRQ, rcu_process_callbacks); } diff --git a/kernel/rcutree.h b/kernel/rcutree.h index 0024e5ddcc68..ca560364d8cd 100644 --- a/kernel/rcutree.h +++ b/kernel/rcutree.h @@ -80,6 +80,7 @@ struct rcu_dynticks { */ struct rcu_node { spinlock_t lock; + long gpnum; /* Current grace period for this node. */ unsigned long qsmask; /* CPUs or groups that need to switch in */ /* order for current grace period to proceed.*/ unsigned long qsmaskinit; @@ -90,6 +91,8 @@ struct rcu_node { u8 grpnum; /* CPU/group number for next level up. */ u8 level; /* root is at level 0. */ struct rcu_node *parent; + struct list_head blocked_tasks[2]; + /* Tasks blocked in RCU read-side critsect. */ } ____cacheline_internodealigned_in_smp; /* Index values for nxttail array in struct rcu_data. */ @@ -111,6 +114,7 @@ struct rcu_data { bool passed_quiesc; /* User-mode/idle loop etc. */ bool qs_pending; /* Core waits for quiesc state. */ bool beenonline; /* CPU online at least once. */ + bool preemptable; /* Preemptable RCU? */ struct rcu_node *mynode; /* This CPU's leaf of hierarchy */ unsigned long grpmask; /* Mask to apply to leaf qsmask. */ @@ -244,5 +248,10 @@ DECLARE_PER_CPU(struct rcu_data, rcu_sched_data); extern struct rcu_state rcu_bh_state; DECLARE_PER_CPU(struct rcu_data, rcu_bh_data); +#ifdef CONFIG_TREE_PREEMPT_RCU +extern struct rcu_state rcu_preempt_state; +DECLARE_PER_CPU(struct rcu_data, rcu_preempt_data); +#endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */ + #endif /* #ifdef RCU_TREE_NONCORE */ diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h new file mode 100644 index 000000000000..cd2ab67400c6 --- /dev/null +++ b/kernel/rcutree_plugin.h @@ -0,0 +1,447 @@ +/* + * Read-Copy Update mechanism for mutual exclusion (tree-based version) + * Internal non-public definitions that provide either classic + * or preemptable semantics. + * + * 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, write to the Free Software + * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. + * + * Copyright Red Hat, 2009 + * Copyright IBM Corporation, 2009 + * + * Author: Ingo Molnar + * Paul E. McKenney + */ + + +#ifdef CONFIG_TREE_PREEMPT_RCU + +struct rcu_state rcu_preempt_state = RCU_STATE_INITIALIZER(rcu_preempt_state); +DEFINE_PER_CPU(struct rcu_data, rcu_preempt_data); + +/* + * Tell them what RCU they are running. + */ +static inline void rcu_bootup_announce(void) +{ + printk(KERN_INFO + "Experimental preemptable hierarchical RCU implementation.\n"); +} + +/* + * Return the number of RCU-preempt batches processed thus far + * for debug and statistics. + */ +long rcu_batches_completed_preempt(void) +{ + return rcu_preempt_state.completed; +} +EXPORT_SYMBOL_GPL(rcu_batches_completed_preempt); + +/* + * Return the number of RCU batches processed thus far for debug & stats. + */ +long rcu_batches_completed(void) +{ + return rcu_batches_completed_preempt(); +} +EXPORT_SYMBOL_GPL(rcu_batches_completed); + +/* + * Record a preemptable-RCU quiescent state for the specified CPU. Note + * that this just means that the task currently running on the CPU is + * not in a quiescent state. There might be any number of tasks blocked + * while in an RCU read-side critical section. + */ +static void rcu_preempt_qs_record(int cpu) +{ + struct rcu_data *rdp = &per_cpu(rcu_preempt_data, cpu); + rdp->passed_quiesc = 1; + rdp->passed_quiesc_completed = rdp->completed; +} + +/* + * We have entered the scheduler or are between softirqs in ksoftirqd. + * If we are in an RCU read-side critical section, we need to reflect + * that in the state of the rcu_node structure corresponding to this CPU. + * Caller must disable hardirqs. + */ +static void rcu_preempt_qs(int cpu) +{ + struct task_struct *t = current; + int phase; + struct rcu_data *rdp; + struct rcu_node *rnp; + + if (t->rcu_read_lock_nesting && + (t->rcu_read_unlock_special & RCU_READ_UNLOCK_BLOCKED) == 0) { + + /* Possibly blocking in an RCU read-side critical section. */ + rdp = rcu_preempt_state.rda[cpu]; + rnp = rdp->mynode; + spin_lock(&rnp->lock); + t->rcu_read_unlock_special |= RCU_READ_UNLOCK_BLOCKED; + t->rcu_blocked_cpu = cpu; + + /* + * If this CPU has already checked in, then this task + * will hold up the next grace period rather than the + * current grace period. Queue the task accordingly. + * If the task is queued for the current grace period + * (i.e., this CPU has not yet passed through a quiescent + * state for the current grace period), then as long + * as that task remains queued, the current grace period + * cannot end. + */ + phase = !(rnp->qsmask & rdp->grpmask) ^ (rnp->gpnum & 0x1); + list_add(&t->rcu_node_entry, &rnp->blocked_tasks[phase]); + smp_mb(); /* Ensure later ctxt swtch seen after above. */ + spin_unlock(&rnp->lock); + } + + /* + * Either we were not in an RCU read-side critical section to + * begin with, or we have now recorded that critical section + * globally. Either way, we can now note a quiescent state + * for this CPU. Again, if we were in an RCU read-side critical + * section, and if that critical section was blocking the current + * grace period, then the fact that the task has been enqueued + * means that we continue to block the current grace period. + */ + rcu_preempt_qs_record(cpu); + t->rcu_read_unlock_special &= ~(RCU_READ_UNLOCK_NEED_QS | + RCU_READ_UNLOCK_GOT_QS); +} + +/* + * Tree-preemptable RCU implementation for rcu_read_lock(). + * Just increment ->rcu_read_lock_nesting, shared state will be updated + * if we block. + */ +void __rcu_read_lock(void) +{ + ACCESS_ONCE(current->rcu_read_lock_nesting)++; + barrier(); /* needed if we ever invoke rcu_read_lock in rcutree.c */ +} +EXPORT_SYMBOL_GPL(__rcu_read_lock); + +static void rcu_read_unlock_special(struct task_struct *t) +{ + int empty; + unsigned long flags; + unsigned long mask; + struct rcu_node *rnp; + int special; + + /* NMI handlers cannot block and cannot safely manipulate state. */ + if (in_nmi()) + return; + + local_irq_save(flags); + + /* + * If RCU core is waiting for this CPU to exit critical section, + * let it know that we have done so. + */ + special = t->rcu_read_unlock_special; + if (special & RCU_READ_UNLOCK_NEED_QS) { + t->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_NEED_QS; + t->rcu_read_unlock_special |= RCU_READ_UNLOCK_GOT_QS; + } + + /* Hardware IRQ handlers cannot block. */ + if (in_irq()) { + local_irq_restore(flags); + return; + } + + /* Clean up if blocked during RCU read-side critical section. */ + if (special & RCU_READ_UNLOCK_BLOCKED) { + t->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_BLOCKED; + + /* Remove this task from the list it blocked on. */ + rnp = rcu_preempt_state.rda[t->rcu_blocked_cpu]->mynode; + spin_lock(&rnp->lock); + empty = list_empty(&rnp->blocked_tasks[rnp->gpnum & 0x1]); + list_del_init(&t->rcu_node_entry); + t->rcu_blocked_cpu = -1; + + /* + * If this was the last task on the current list, and if + * we aren't waiting on any CPUs, report the quiescent state. + * Note that both cpu_quiet_msk_finish() and cpu_quiet_msk() + * drop rnp->lock and restore irq. + */ + if (!empty && rnp->qsmask == 0 && + list_empty(&rnp->blocked_tasks[rnp->gpnum & 0x1])) { + t->rcu_read_unlock_special &= + ~(RCU_READ_UNLOCK_NEED_QS | + RCU_READ_UNLOCK_GOT_QS); + if (rnp->parent == NULL) { + /* Only one rcu_node in the tree. */ + cpu_quiet_msk_finish(&rcu_preempt_state, flags); + return; + } + /* Report up the rest of the hierarchy. */ + mask = rnp->grpmask; + spin_unlock_irqrestore(&rnp->lock, flags); + rnp = rnp->parent; + spin_lock_irqsave(&rnp->lock, flags); + cpu_quiet_msk(mask, &rcu_preempt_state, rnp, flags); + return; + } + spin_unlock(&rnp->lock); + } + local_irq_restore(flags); +} + +/* + * Tree-preemptable RCU implementation for rcu_read_unlock(). + * Decrement ->rcu_read_lock_nesting. If the result is zero (outermost + * rcu_read_unlock()) and ->rcu_read_unlock_special is non-zero, then + * invoke rcu_read_unlock_special() to clean up after a context switch + * in an RCU read-side critical section and other special cases. + */ +void __rcu_read_unlock(void) +{ + struct task_struct *t = current; + + barrier(); /* needed if we ever invoke rcu_read_unlock in rcutree.c */ + if (--ACCESS_ONCE(t->rcu_read_lock_nesting) == 0 && + unlikely(ACCESS_ONCE(t->rcu_read_unlock_special))) + rcu_read_unlock_special(t); +} +EXPORT_SYMBOL_GPL(__rcu_read_unlock); + +#ifdef CONFIG_RCU_CPU_STALL_DETECTOR + +/* + * Scan the current list of tasks blocked within RCU read-side critical + * sections, printing out the tid of each. + */ +static void rcu_print_task_stall(struct rcu_node *rnp) +{ + unsigned long flags; + struct list_head *lp; + int phase = rnp->gpnum & 0x1; + struct task_struct *t; + + if (!list_empty(&rnp->blocked_tasks[phase])) { + spin_lock_irqsave(&rnp->lock, flags); + phase = rnp->gpnum & 0x1; /* re-read under lock. */ + lp = &rnp->blocked_tasks[phase]; + list_for_each_entry(t, lp, rcu_node_entry) + printk(" P%d", t->pid); + spin_unlock_irqrestore(&rnp->lock, flags); + } +} + +#endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ + +/* + * Check for preempted RCU readers for the specified rcu_node structure. + * If the caller needs a reliable answer, it must hold the rcu_node's + * >lock. + */ +static int rcu_preempted_readers(struct rcu_node *rnp) +{ + return !list_empty(&rnp->blocked_tasks[rnp->gpnum & 0x1]); +} + +/* + * Check for a quiescent state from the current CPU. When a task blocks, + * the task is recorded in the corresponding CPU's rcu_node structure, + * which is checked elsewhere. + * + * Caller must disable hard irqs. + */ +static void rcu_preempt_check_callbacks(int cpu) +{ + struct task_struct *t = current; + + if (t->rcu_read_lock_nesting == 0) { + t->rcu_read_unlock_special &= + ~(RCU_READ_UNLOCK_NEED_QS | RCU_READ_UNLOCK_GOT_QS); + rcu_preempt_qs_record(cpu); + return; + } + if (per_cpu(rcu_preempt_data, cpu).qs_pending) { + if (t->rcu_read_unlock_special & RCU_READ_UNLOCK_GOT_QS) { + rcu_preempt_qs_record(cpu); + t->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_GOT_QS; + } else if (!(t->rcu_read_unlock_special & + RCU_READ_UNLOCK_NEED_QS)) { + t->rcu_read_unlock_special |= RCU_READ_UNLOCK_NEED_QS; + } + } +} + +/* + * Process callbacks for preemptable RCU. + */ +static void rcu_preempt_process_callbacks(void) +{ + __rcu_process_callbacks(&rcu_preempt_state, + &__get_cpu_var(rcu_preempt_data)); +} + +/* + * Queue a preemptable-RCU callback for invocation after a grace period. + */ +void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) +{ + __call_rcu(head, func, &rcu_preempt_state); +} +EXPORT_SYMBOL_GPL(call_rcu); + +/* + * Check to see if there is any immediate preemptable-RCU-related work + * to be done. + */ +static int rcu_preempt_pending(int cpu) +{ + return __rcu_pending(&rcu_preempt_state, + &per_cpu(rcu_preempt_data, cpu)); +} + +/* + * Does preemptable RCU need the CPU to stay out of dynticks mode? + */ +static int rcu_preempt_needs_cpu(int cpu) +{ + return !!per_cpu(rcu_preempt_data, cpu).nxtlist; +} + +/* + * Initialize preemptable RCU's per-CPU data. + */ +static void __cpuinit rcu_preempt_init_percpu_data(int cpu) +{ + rcu_init_percpu_data(cpu, &rcu_preempt_state, 1); +} + +/* + * Check for a task exiting while in a preemptable-RCU read-side + * critical section, clean up if so. No need to issue warnings, + * as debug_check_no_locks_held() already does this if lockdep + * is enabled. + */ +void exit_rcu(void) +{ + struct task_struct *t = current; + + if (t->rcu_read_lock_nesting == 0) + return; + t->rcu_read_lock_nesting = 1; + rcu_read_unlock(); +} + +#else /* #ifdef CONFIG_TREE_PREEMPT_RCU */ + +/* + * Tell them what RCU they are running. + */ +static inline void rcu_bootup_announce(void) +{ + printk(KERN_INFO "Hierarchical RCU implementation.\n"); +} + +/* + * Return the number of RCU batches processed thus far for debug & stats. + */ +long rcu_batches_completed(void) +{ + return rcu_batches_completed_sched(); +} +EXPORT_SYMBOL_GPL(rcu_batches_completed); + +/* + * Because preemptable RCU does not exist, we never have to check for + * CPUs being in quiescent states. + */ +static void rcu_preempt_qs(int cpu) +{ +} + +#ifdef CONFIG_RCU_CPU_STALL_DETECTOR + +/* + * Because preemptable RCU does not exist, we never have to check for + * tasks blocked within RCU read-side critical sections. + */ +static void rcu_print_task_stall(struct rcu_node *rnp) +{ +} + +#endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ + +/* + * Because preemptable RCU does not exist, there are never any preempted + * RCU readers. + */ +static int rcu_preempted_readers(struct rcu_node *rnp) +{ + return 0; +} + +/* + * Because preemptable RCU does not exist, it never has any callbacks + * to check. + */ +void rcu_preempt_check_callbacks(int cpu) +{ +} + +/* + * Because preemptable RCU does not exist, it never has any callbacks + * to process. + */ +void rcu_preempt_process_callbacks(void) +{ +} + +/* + * In classic RCU, call_rcu() is just call_rcu_sched(). + */ +void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) +{ + call_rcu_sched(head, func); +} +EXPORT_SYMBOL_GPL(call_rcu); + +/* + * Because preemptable RCU does not exist, it never has any work to do. + */ +static int rcu_preempt_pending(int cpu) +{ + return 0; +} + +/* + * Because preemptable RCU does not exist, it never needs any CPU. + */ +static int rcu_preempt_needs_cpu(int cpu) +{ + return 0; +} + +/* + * Because preemptable RCU does not exist, there is no per-CPU + * data to initialize. + */ +static void __cpuinit rcu_preempt_init_percpu_data(int cpu) +{ +} + +#endif /* #else #ifdef CONFIG_TREE_PREEMPT_RCU */ diff --git a/kernel/rcutree_trace.c b/kernel/rcutree_trace.c index 31af3a0fb6d5..0ea1bff69727 100644 --- a/kernel/rcutree_trace.c +++ b/kernel/rcutree_trace.c @@ -77,6 +77,10 @@ static void print_one_rcu_data(struct seq_file *m, struct rcu_data *rdp) static int show_rcudata(struct seq_file *m, void *unused) { +#ifdef CONFIG_TREE_PREEMPT_RCU + seq_puts(m, "rcu_preempt:\n"); + PRINT_RCU_DATA(rcu_preempt_data, print_one_rcu_data, m); +#endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */ seq_puts(m, "rcu_sched:\n"); PRINT_RCU_DATA(rcu_sched_data, print_one_rcu_data, m); seq_puts(m, "rcu_bh:\n"); @@ -125,6 +129,10 @@ static int show_rcudata_csv(struct seq_file *m, void *unused) seq_puts(m, "\"dt\",\"dt nesting\",\"dn\",\"df\","); #endif /* #ifdef CONFIG_NO_HZ */ seq_puts(m, "\"of\",\"ri\",\"ql\",\"b\"\n"); +#ifdef CONFIG_TREE_PREEMPT_RCU + seq_puts(m, "\"rcu_preempt:\"\n"); + PRINT_RCU_DATA(rcu_preempt_data, print_one_rcu_data_csv, m); +#endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */ seq_puts(m, "\"rcu_sched:\"\n"); PRINT_RCU_DATA(rcu_sched_data, print_one_rcu_data_csv, m); seq_puts(m, "\"rcu_bh:\"\n"); @@ -172,6 +180,10 @@ static void print_one_rcu_state(struct seq_file *m, struct rcu_state *rsp) static int show_rcuhier(struct seq_file *m, void *unused) { +#ifdef CONFIG_TREE_PREEMPT_RCU + seq_puts(m, "rcu_preempt:\n"); + print_one_rcu_state(m, &rcu_preempt_state); +#endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */ seq_puts(m, "rcu_sched:\n"); print_one_rcu_state(m, &rcu_sched_state); seq_puts(m, "rcu_bh:\n"); @@ -194,6 +206,10 @@ static struct file_operations rcuhier_fops = { static int show_rcugp(struct seq_file *m, void *unused) { +#ifdef CONFIG_TREE_PREEMPT_RCU + seq_printf(m, "rcu_preempt: completed=%ld gpnum=%ld\n", + rcu_preempt_state.completed, rcu_preempt_state.gpnum); +#endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */ seq_printf(m, "rcu_sched: completed=%ld gpnum=%ld\n", rcu_sched_state.completed, rcu_sched_state.gpnum); seq_printf(m, "rcu_bh: completed=%ld gpnum=%ld\n", @@ -244,6 +260,10 @@ static void print_rcu_pendings(struct seq_file *m, struct rcu_state *rsp) static int show_rcu_pending(struct seq_file *m, void *unused) { +#ifdef CONFIG_TREE_PREEMPT_RCU + seq_puts(m, "rcu_preempt:\n"); + print_rcu_pendings(m, &rcu_preempt_state); +#endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */ seq_puts(m, "rcu_sched:\n"); print_rcu_pendings(m, &rcu_sched_state); seq_puts(m, "rcu_bh:\n"); diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index 12327b2bb785..f87fb0c8f924 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -725,7 +725,7 @@ config RCU_TORTURE_TEST_RUNNABLE config RCU_CPU_STALL_DETECTOR bool "Check for stalled CPUs delaying RCU grace periods" - depends on CLASSIC_RCU || TREE_RCU + depends on CLASSIC_RCU || TREE_RCU || TREE_PREEMPT_RCU default n help This option causes RCU to printk information on which -- cgit v1.2.3-59-g8ed1b From 6b3ef48adf847f7adf11c870e3ffacac150f1564 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Sat, 22 Aug 2009 13:56:53 -0700 Subject: rcu: Remove CONFIG_PREEMPT_RCU Now that CONFIG_TREE_PREEMPT_RCU is in place, there is no further need for CONFIG_PREEMPT_RCU. Remove it, along with whatever subtle bugs it may (or may not) contain. Signed-off-by: Paul E. McKenney Cc: laijs@cn.fujitsu.com Cc: dipankar@in.ibm.com Cc: akpm@linux-foundation.org Cc: mathieu.desnoyers@polymtl.ca Cc: josht@linux.vnet.ibm.com Cc: dvhltc@us.ibm.com Cc: niv@us.ibm.com Cc: peterz@infradead.org Cc: rostedt@goodmis.org LKML-Reference: <125097461396-git-send-email-> Signed-off-by: Ingo Molnar --- Documentation/RCU/rcu.txt | 10 +- Documentation/RCU/whatisRCU.txt | 8 +- include/linux/init_task.h | 6 +- include/linux/rcupdate.h | 4 +- include/linux/rcupreempt.h | 140 ---- include/linux/rcupreempt_trace.h | 97 --- include/linux/sched.h | 13 - init/Kconfig | 20 +- kernel/Makefile | 2 - kernel/rcupreempt.c | 1518 -------------------------------------- kernel/rcupreempt_trace.c | 335 --------- lib/Kconfig.debug | 2 +- 12 files changed, 13 insertions(+), 2142 deletions(-) delete mode 100644 include/linux/rcupreempt.h delete mode 100644 include/linux/rcupreempt_trace.h delete mode 100644 kernel/rcupreempt.c delete mode 100644 kernel/rcupreempt_trace.c (limited to 'include') diff --git a/Documentation/RCU/rcu.txt b/Documentation/RCU/rcu.txt index 7aa2002ade77..2a23523ce471 100644 --- a/Documentation/RCU/rcu.txt +++ b/Documentation/RCU/rcu.txt @@ -36,7 +36,7 @@ o How can the updater tell when a grace period has completed executed in user mode, or executed in the idle loop, we can safely free up that item. - Preemptible variants of RCU (CONFIG_PREEMPT_RCU) get the + Preemptible variants of RCU (CONFIG_TREE_PREEMPT_RCU) get the same effect, but require that the readers manipulate CPU-local counters. These counters allow limited types of blocking within RCU read-side critical sections. SRCU also uses @@ -79,10 +79,10 @@ o I hear that RCU is patented? What is with that? o I hear that RCU needs work in order to support realtime kernels? This work is largely completed. Realtime-friendly RCU can be - enabled via the CONFIG_PREEMPT_RCU kernel configuration parameter. - However, work is in progress for enabling priority boosting of - preempted RCU read-side critical sections. This is needed if you - have CPU-bound realtime threads. + enabled via the CONFIG_TREE_PREEMPT_RCU kernel configuration + parameter. However, work is in progress for enabling priority + boosting of preempted RCU read-side critical sections. This is + needed if you have CPU-bound realtime threads. o Where can I find more information on RCU? diff --git a/Documentation/RCU/whatisRCU.txt b/Documentation/RCU/whatisRCU.txt index 97ded2432c59..e41a7fecf0d3 100644 --- a/Documentation/RCU/whatisRCU.txt +++ b/Documentation/RCU/whatisRCU.txt @@ -136,10 +136,10 @@ rcu_read_lock() Used by a reader to inform the reclaimer that the reader is entering an RCU read-side critical section. It is illegal to block while in an RCU read-side critical section, though - kernels built with CONFIG_PREEMPT_RCU can preempt RCU read-side - critical sections. Any RCU-protected data structure accessed - during an RCU read-side critical section is guaranteed to remain - unreclaimed for the full duration of that critical section. + kernels built with CONFIG_TREE_PREEMPT_RCU can preempt RCU + read-side critical sections. Any RCU-protected data structure + accessed during an RCU read-side critical section is guaranteed to + remain unreclaimed for the full duration of that critical section. Reference counts may be used in conjunction with RCU to maintain longer-term references to data structures. diff --git a/include/linux/init_task.h b/include/linux/init_task.h index 971a968831bf..79d4baee31b6 100644 --- a/include/linux/init_task.h +++ b/include/linux/init_task.h @@ -94,11 +94,7 @@ extern struct group_info init_groups; # define CAP_INIT_BSET CAP_INIT_EFF_SET #endif -#ifdef CONFIG_PREEMPT_RCU -#define INIT_TASK_RCU_PREEMPT(tsk) \ - .rcu_read_lock_nesting = 0, \ - .rcu_flipctr_idx = 0, -#elif defined(CONFIG_TREE_PREEMPT_RCU) +#ifdef CONFIG_TREE_PREEMPT_RCU #define INIT_TASK_RCU_PREEMPT(tsk) \ .rcu_read_lock_nesting = 0, \ .rcu_read_unlock_special = 0, \ diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 26892f5e7bd8..ec90fc34fea9 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -68,11 +68,9 @@ extern int rcu_scheduler_active; #if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU) #include -#elif defined(CONFIG_PREEMPT_RCU) -#include #else #error "Unknown RCU implementation specified to kernel configuration" -#endif /* #else #if defined(CONFIG_CLASSIC_RCU) */ +#endif #define RCU_HEAD_INIT { .next = NULL, .func = NULL } #define RCU_HEAD(head) struct rcu_head head = RCU_HEAD_INIT diff --git a/include/linux/rcupreempt.h b/include/linux/rcupreempt.h deleted file mode 100644 index a42ab88e9210..000000000000 --- a/include/linux/rcupreempt.h +++ /dev/null @@ -1,140 +0,0 @@ -/* - * Read-Copy Update mechanism for mutual exclusion (RT 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, write to the Free Software - * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. - * - * Copyright (C) IBM Corporation, 2006 - * - * Author: Paul McKenney - * - * Based on the original work by Paul McKenney - * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen. - * Papers: - * http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf - * http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001) - * - * For detailed explanation of Read-Copy Update mechanism see - - * Documentation/RCU - * - */ - -#ifndef __LINUX_RCUPREEMPT_H -#define __LINUX_RCUPREEMPT_H - -#include -#include -#include -#include -#include -#include - -extern void rcu_sched_qs(int cpu); -static inline void rcu_bh_qs(int cpu) { } - -/* - * Someone might want to pass call_rcu_bh as a function pointer. - * So this needs to just be a rename and not a macro function. - * (no parentheses) - */ -#define call_rcu_bh call_rcu - -/** - * call_rcu_sched - Queue RCU callback for invocation after sched grace period. - * @head: structure to be used for queueing the RCU updates. - * @func: actual update function to be invoked after the grace period - * - * The update function will be invoked some time after a full - * synchronize_sched()-style grace period elapses, in other words after - * all currently executing preempt-disabled sections of code (including - * hardirq handlers, NMI handlers, and local_irq_save() blocks) have - * completed. - */ -extern void call_rcu_sched(struct rcu_head *head, - void (*func)(struct rcu_head *head)); - -extern void __rcu_read_lock(void); -extern void __rcu_read_unlock(void); -extern int rcu_needs_cpu(int cpu); - -#define __rcu_read_lock_bh() { rcu_read_lock(); local_bh_disable(); } -#define __rcu_read_unlock_bh() { local_bh_enable(); rcu_read_unlock(); } - -extern void __synchronize_sched(void); - -static inline void synchronize_rcu_expedited(void) -{ - synchronize_rcu(); /* Placeholder for new rcupreempt implementation. */ -} - -static inline void synchronize_rcu_bh_expedited(void) -{ - synchronize_rcu_bh(); /* Placeholder for new rcupreempt impl. */ -} - -extern void __rcu_init(void); -extern void rcu_init_sched(void); -extern void rcu_check_callbacks(int cpu, int user); -extern void rcu_restart_cpu(int cpu); -extern long rcu_batches_completed(void); - -/* - * Return the number of RCU batches processed thus far. Useful for debug - * and statistic. The _bh variant is identifcal to straight RCU - */ -static inline long rcu_batches_completed_bh(void) -{ - return rcu_batches_completed(); -} - -static inline void exit_rcu(void) -{ -} - -#ifdef CONFIG_RCU_TRACE -struct rcupreempt_trace; -extern long *rcupreempt_flipctr(int cpu); -extern long rcupreempt_data_completed(void); -extern int rcupreempt_flip_flag(int cpu); -extern int rcupreempt_mb_flag(int cpu); -extern char *rcupreempt_try_flip_state_name(void); -extern struct rcupreempt_trace *rcupreempt_trace_cpu(int cpu); -#endif - -struct softirq_action; - -#ifdef CONFIG_NO_HZ -extern void rcu_enter_nohz(void); -extern void rcu_exit_nohz(void); -#else -# define rcu_enter_nohz() do { } while (0) -# define rcu_exit_nohz() do { } while (0) -#endif - -/* - * A context switch is a grace period for rcupreempt synchronize_rcu() - * only during early boot, before the scheduler has been initialized. - * So, how the heck do we get a context switch? Well, if the caller - * invokes synchronize_rcu(), they are willing to accept a context - * switch, so we simply pretend that one happened. - * - * After boot, there might be a blocked or preempted task in an RCU - * read-side critical section, so we cannot then take the fastpath. - */ -static inline int rcu_blocking_is_gp(void) -{ - return num_online_cpus() == 1 && !rcu_scheduler_active; -} - -#endif /* __LINUX_RCUPREEMPT_H */ diff --git a/include/linux/rcupreempt_trace.h b/include/linux/rcupreempt_trace.h deleted file mode 100644 index b99ae073192a..000000000000 --- a/include/linux/rcupreempt_trace.h +++ /dev/null @@ -1,97 +0,0 @@ -/* - * Read-Copy Update mechanism for mutual exclusion (RT 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, write to the Free Software - * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. - * - * Copyright (C) IBM Corporation, 2006 - * - * Author: Paul McKenney - * - * Based on the original work by Paul McKenney - * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen. - * Papers: - * http://www.rdrop.com/users/paulmck/paper/rclockpdcsproof.pdf - * http://lse.sourceforge.net/locking/rclock_OLS.2001.05.01c.sc.pdf (OLS2001) - * - * For detailed explanation of the Preemptible Read-Copy Update mechanism see - - * http://lwn.net/Articles/253651/ - */ - -#ifndef __LINUX_RCUPREEMPT_TRACE_H -#define __LINUX_RCUPREEMPT_TRACE_H - -#include -#include - -#include - -/* - * PREEMPT_RCU data structures. - */ - -struct rcupreempt_trace { - long next_length; - long next_add; - long wait_length; - long wait_add; - long done_length; - long done_add; - long done_remove; - atomic_t done_invoked; - long rcu_check_callbacks; - atomic_t rcu_try_flip_1; - atomic_t rcu_try_flip_e1; - long rcu_try_flip_i1; - long rcu_try_flip_ie1; - long rcu_try_flip_g1; - long rcu_try_flip_a1; - long rcu_try_flip_ae1; - long rcu_try_flip_a2; - long rcu_try_flip_z1; - long rcu_try_flip_ze1; - long rcu_try_flip_z2; - long rcu_try_flip_m1; - long rcu_try_flip_me1; - long rcu_try_flip_m2; -}; - -#ifdef CONFIG_RCU_TRACE -#define RCU_TRACE(fn, arg) fn(arg); -#else -#define RCU_TRACE(fn, arg) -#endif - -extern void rcupreempt_trace_move2done(struct rcupreempt_trace *trace); -extern void rcupreempt_trace_move2wait(struct rcupreempt_trace *trace); -extern void rcupreempt_trace_try_flip_1(struct rcupreempt_trace *trace); -extern void rcupreempt_trace_try_flip_e1(struct rcupreempt_trace *trace); -extern void rcupreempt_trace_try_flip_i1(struct rcupreempt_trace *trace); -extern void rcupreempt_trace_try_flip_ie1(struct rcupreempt_trace *trace); -extern void rcupreempt_trace_try_flip_g1(struct rcupreempt_trace *trace); -extern void rcupreempt_trace_try_flip_a1(struct rcupreempt_trace *trace); -extern void rcupreempt_trace_try_flip_ae1(struct rcupreempt_trace *trace); -extern void rcupreempt_trace_try_flip_a2(struct rcupreempt_trace *trace); -extern void rcupreempt_trace_try_flip_z1(struct rcupreempt_trace *trace); -extern void rcupreempt_trace_try_flip_ze1(struct rcupreempt_trace *trace); -extern void rcupreempt_trace_try_flip_z2(struct rcupreempt_trace *trace); -extern void rcupreempt_trace_try_flip_m1(struct rcupreempt_trace *trace); -extern void rcupreempt_trace_try_flip_me1(struct rcupreempt_trace *trace); -extern void rcupreempt_trace_try_flip_m2(struct rcupreempt_trace *trace); -extern void rcupreempt_trace_check_callbacks(struct rcupreempt_trace *trace); -extern void rcupreempt_trace_done_remove(struct rcupreempt_trace *trace); -extern void rcupreempt_trace_invoke(struct rcupreempt_trace *trace); -extern void rcupreempt_trace_next_add(struct rcupreempt_trace *trace); - -#endif /* __LINUX_RCUPREEMPT_TRACE_H */ diff --git a/include/linux/sched.h b/include/linux/sched.h index d7f98f637a2a..bfca26d63b13 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1205,11 +1205,6 @@ struct task_struct { unsigned int policy; cpumask_t cpus_allowed; -#ifdef CONFIG_PREEMPT_RCU - int rcu_read_lock_nesting; - int rcu_flipctr_idx; -#endif /* #ifdef CONFIG_PREEMPT_RCU */ - #ifdef CONFIG_TREE_PREEMPT_RCU int rcu_read_lock_nesting; char rcu_read_unlock_special; @@ -1744,14 +1739,6 @@ static inline void rcu_copy_process(struct task_struct *p) INIT_LIST_HEAD(&p->rcu_node_entry); } -#elif defined(CONFIG_PREEMPT_RCU) - -static inline void rcu_copy_process(struct task_struct *p) -{ - p->rcu_read_lock_nesting = 0; - p->rcu_flipctr_idx = 0; -} - #else static inline void rcu_copy_process(struct task_struct *p) diff --git a/init/Kconfig b/init/Kconfig index f88da2d1c1fb..8e8b76d8a272 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -324,17 +324,6 @@ config TREE_RCU thousands of CPUs. It also scales down nicely to smaller systems. -config PREEMPT_RCU - bool "Preemptible RCU" - depends on PREEMPT - help - This option reduces the latency of the kernel by making certain - RCU sections preemptible. Normally RCU code is non-preemptible, if - this option is selected then read-only RCU sections become - preemptible. This helps latency, but may expose bugs due to - now-naive assumptions about each RCU read-side critical section - remaining on a given CPU through its execution. - config TREE_PREEMPT_RCU bool "Preemptable tree-based hierarchical RCU" depends on PREEMPT @@ -348,7 +337,7 @@ endchoice config RCU_TRACE bool "Enable tracing for RCU" - depends on TREE_RCU || PREEMPT_RCU || TREE_PREEMPT_RCU + depends on TREE_RCU || TREE_PREEMPT_RCU help This option provides tracing in RCU which presents stats in debugfs for debugging RCU implementation. @@ -395,13 +384,6 @@ config TREE_RCU_TRACE TREE_PREEMPT_RCU implementations, permitting Makefile to trivially select kernel/rcutree_trace.c. -config PREEMPT_RCU_TRACE - def_bool RCU_TRACE && PREEMPT_RCU - select DEBUG_FS - help - This option provides tracing for the PREEMPT_RCU implementation, - permitting Makefile to trivially select kernel/rcupreempt_trace.c. - endmenu # "RCU Subsystem" config IKCONFIG diff --git a/kernel/Makefile b/kernel/Makefile index 1a38b4789dda..b833bd5cc127 100644 --- a/kernel/Makefile +++ b/kernel/Makefile @@ -82,9 +82,7 @@ obj-$(CONFIG_SECCOMP) += seccomp.o obj-$(CONFIG_RCU_TORTURE_TEST) += rcutorture.o obj-$(CONFIG_TREE_RCU) += rcutree.o obj-$(CONFIG_TREE_PREEMPT_RCU) += rcutree.o -obj-$(CONFIG_PREEMPT_RCU) += rcupreempt.o obj-$(CONFIG_TREE_RCU_TRACE) += rcutree_trace.o -obj-$(CONFIG_PREEMPT_RCU_TRACE) += rcupreempt_trace.o obj-$(CONFIG_RELAY) += relay.o obj-$(CONFIG_SYSCTL) += utsname_sysctl.o obj-$(CONFIG_TASK_DELAY_ACCT) += delayacct.o diff --git a/kernel/rcupreempt.c b/kernel/rcupreempt.c deleted file mode 100644 index 0053ce56e326..000000000000 --- a/kernel/rcupreempt.c +++ /dev/null @@ -1,1518 +0,0 @@ -/* - * Read-Copy Update mechanism for mutual exclusion, realtime 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, write to the Free Software - * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. - * - * Copyright IBM Corporation, 2006 - * - * Authors: Paul E. McKenney - * With thanks to Esben Nielsen, Bill Huey, and Ingo Molnar - * for pushing me away from locks and towards counters, and - * to Suparna Bhattacharya for pushing me completely away - * from atomic instructions on the read side. - * - * - Added handling of Dynamic Ticks - * Copyright 2007 - Paul E. Mckenney - * - Steven Rostedt - * - * Papers: http://www.rdrop.com/users/paulmck/RCU - * - * Design Document: http://lwn.net/Articles/253651/ - * - * For detailed explanation of Read-Copy Update mechanism see - - * Documentation/RCU/ *.txt - * - */ -#include -#include -#include -#include -#include -#include -#include -#include -#include -#include -#include -#include -#include -#include -#include -#include -#include -#include -#include -#include -#include -#include - -/* - * PREEMPT_RCU data structures. - */ - -/* - * GP_STAGES specifies the number of times the state machine has - * to go through the all the rcu_try_flip_states (see below) - * in a single Grace Period. - * - * GP in GP_STAGES stands for Grace Period ;) - */ -#define GP_STAGES 2 -struct rcu_data { - spinlock_t lock; /* Protect rcu_data fields. */ - long completed; /* Number of last completed batch. */ - int waitlistcount; - struct rcu_head *nextlist; - struct rcu_head **nexttail; - struct rcu_head *waitlist[GP_STAGES]; - struct rcu_head **waittail[GP_STAGES]; - struct rcu_head *donelist; /* from waitlist & waitschedlist */ - struct rcu_head **donetail; - long rcu_flipctr[2]; - struct rcu_head *nextschedlist; - struct rcu_head **nextschedtail; - struct rcu_head *waitschedlist; - struct rcu_head **waitschedtail; - int rcu_sched_sleeping; -#ifdef CONFIG_RCU_TRACE - struct rcupreempt_trace trace; -#endif /* #ifdef CONFIG_RCU_TRACE */ -}; - -/* - * States for rcu_try_flip() and friends. - */ - -enum rcu_try_flip_states { - - /* - * Stay here if nothing is happening. Flip the counter if somthing - * starts happening. Denoted by "I" - */ - rcu_try_flip_idle_state, - - /* - * Wait here for all CPUs to notice that the counter has flipped. This - * prevents the old set of counters from ever being incremented once - * we leave this state, which in turn is necessary because we cannot - * test any individual counter for zero -- we can only check the sum. - * Denoted by "A". - */ - rcu_try_flip_waitack_state, - - /* - * Wait here for the sum of the old per-CPU counters to reach zero. - * Denoted by "Z". - */ - rcu_try_flip_waitzero_state, - - /* - * Wait here for each of the other CPUs to execute a memory barrier. - * This is necessary to ensure that these other CPUs really have - * completed executing their RCU read-side critical sections, despite - * their CPUs wildly reordering memory. Denoted by "M". - */ - rcu_try_flip_waitmb_state, -}; - -/* - * States for rcu_ctrlblk.rcu_sched_sleep. - */ - -enum rcu_sched_sleep_states { - rcu_sched_not_sleeping, /* Not sleeping, callbacks need GP. */ - rcu_sched_sleep_prep, /* Thinking of sleeping, rechecking. */ - rcu_sched_sleeping, /* Sleeping, awaken if GP needed. */ -}; - -struct rcu_ctrlblk { - spinlock_t fliplock; /* Protect state-machine transitions. */ - long completed; /* Number of last completed batch. */ - enum rcu_try_flip_states rcu_try_flip_state; /* The current state of - the rcu state machine */ - spinlock_t schedlock; /* Protect rcu_sched sleep state. */ - enum rcu_sched_sleep_states sched_sleep; /* rcu_sched state. */ - wait_queue_head_t sched_wq; /* Place for rcu_sched to sleep. */ -}; - -struct rcu_dyntick_sched { - int dynticks; - int dynticks_snap; - int sched_qs; - int sched_qs_snap; - int sched_dynticks_snap; -}; - -static DEFINE_PER_CPU_SHARED_ALIGNED(struct rcu_dyntick_sched, rcu_dyntick_sched) = { - .dynticks = 1, -}; - -static int rcu_pending(int cpu); - -void rcu_sched_qs(int cpu) -{ - struct rcu_dyntick_sched *rdssp = &per_cpu(rcu_dyntick_sched, cpu); - - rdssp->sched_qs++; -} - -#ifdef CONFIG_NO_HZ - -void rcu_enter_nohz(void) -{ - static DEFINE_RATELIMIT_STATE(rs, 10 * HZ, 1); - - smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */ - __get_cpu_var(rcu_dyntick_sched).dynticks++; - WARN_ON_RATELIMIT(__get_cpu_var(rcu_dyntick_sched).dynticks & 0x1, &rs); -} - -void rcu_exit_nohz(void) -{ - static DEFINE_RATELIMIT_STATE(rs, 10 * HZ, 1); - - __get_cpu_var(rcu_dyntick_sched).dynticks++; - smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */ - WARN_ON_RATELIMIT(!(__get_cpu_var(rcu_dyntick_sched).dynticks & 0x1), - &rs); -} - -#endif /* CONFIG_NO_HZ */ - - -static DEFINE_PER_CPU(struct rcu_data, rcu_data); - -static struct rcu_ctrlblk rcu_ctrlblk = { - .fliplock = __SPIN_LOCK_UNLOCKED(rcu_ctrlblk.fliplock), - .completed = 0, - .rcu_try_flip_state = rcu_try_flip_idle_state, - .schedlock = __SPIN_LOCK_UNLOCKED(rcu_ctrlblk.schedlock), - .sched_sleep = rcu_sched_not_sleeping, - .sched_wq = __WAIT_QUEUE_HEAD_INITIALIZER(rcu_ctrlblk.sched_wq), -}; - -static struct task_struct *rcu_sched_grace_period_task; - -#ifdef CONFIG_RCU_TRACE -static char *rcu_try_flip_state_names[] = - { "idle", "waitack", "waitzero", "waitmb" }; -#endif /* #ifdef CONFIG_RCU_TRACE */ - -static DECLARE_BITMAP(rcu_cpu_online_map, NR_CPUS) __read_mostly - = CPU_BITS_NONE; - -/* - * Enum and per-CPU flag to determine when each CPU has seen - * the most recent counter flip. - */ - -enum rcu_flip_flag_values { - rcu_flip_seen, /* Steady/initial state, last flip seen. */ - /* Only GP detector can update. */ - rcu_flipped /* Flip just completed, need confirmation. */ - /* Only corresponding CPU can update. */ -}; -static DEFINE_PER_CPU_SHARED_ALIGNED(enum rcu_flip_flag_values, rcu_flip_flag) - = rcu_flip_seen; - -/* - * Enum and per-CPU flag to determine when each CPU has executed the - * needed memory barrier to fence in memory references from its last RCU - * read-side critical section in the just-completed grace period. - */ - -enum rcu_mb_flag_values { - rcu_mb_done, /* Steady/initial state, no mb()s required. */ - /* Only GP detector can update. */ - rcu_mb_needed /* Flip just completed, need an mb(). */ - /* Only corresponding CPU can update. */ -}; -static DEFINE_PER_CPU_SHARED_ALIGNED(enum rcu_mb_flag_values, rcu_mb_flag) - = rcu_mb_done; - -/* - * RCU_DATA_ME: find the current CPU's rcu_data structure. - * RCU_DATA_CPU: find the specified CPU's rcu_data structure. - */ -#define RCU_DATA_ME() (&__get_cpu_var(rcu_data)) -#define RCU_DATA_CPU(cpu) (&per_cpu(rcu_data, cpu)) - -/* - * Helper macro for tracing when the appropriate rcu_data is not - * cached in a local variable, but where the CPU number is so cached. - */ -#define RCU_TRACE_CPU(f, cpu) RCU_TRACE(f, &(RCU_DATA_CPU(cpu)->trace)); - -/* - * Helper macro for tracing when the appropriate rcu_data is not - * cached in a local variable. - */ -#define RCU_TRACE_ME(f) RCU_TRACE(f, &(RCU_DATA_ME()->trace)); - -/* - * Helper macro for tracing when the appropriate rcu_data is pointed - * to by a local variable. - */ -#define RCU_TRACE_RDP(f, rdp) RCU_TRACE(f, &((rdp)->trace)); - -#define RCU_SCHED_BATCH_TIME (HZ / 50) - -/* - * Return the number of RCU batches processed thus far. Useful - * for debug and statistics. - */ -long rcu_batches_completed(void) -{ - return rcu_ctrlblk.completed; -} -EXPORT_SYMBOL_GPL(rcu_batches_completed); - -void __rcu_read_lock(void) -{ - int idx; - struct task_struct *t = current; - int nesting; - - nesting = ACCESS_ONCE(t->rcu_read_lock_nesting); - if (nesting != 0) { - - /* An earlier rcu_read_lock() covers us, just count it. */ - - t->rcu_read_lock_nesting = nesting + 1; - - } else { - unsigned long flags; - - /* - * We disable interrupts for the following reasons: - * - If we get scheduling clock interrupt here, and we - * end up acking the counter flip, it's like a promise - * that we will never increment the old counter again. - * Thus we will break that promise if that - * scheduling clock interrupt happens between the time - * we pick the .completed field and the time that we - * increment our counter. - * - * - We don't want to be preempted out here. - * - * NMIs can still occur, of course, and might themselves - * contain rcu_read_lock(). - */ - - local_irq_save(flags); - - /* - * Outermost nesting of rcu_read_lock(), so increment - * the current counter for the current CPU. Use volatile - * casts to prevent the compiler from reordering. - */ - - idx = ACCESS_ONCE(rcu_ctrlblk.completed) & 0x1; - ACCESS_ONCE(RCU_DATA_ME()->rcu_flipctr[idx])++; - - /* - * Now that the per-CPU counter has been incremented, we - * are protected from races with rcu_read_lock() invoked - * from NMI handlers on this CPU. We can therefore safely - * increment the nesting counter, relieving further NMIs - * of the need to increment the per-CPU counter. - */ - - ACCESS_ONCE(t->rcu_read_lock_nesting) = nesting + 1; - - /* - * Now that we have preventing any NMIs from storing - * to the ->rcu_flipctr_idx, we can safely use it to - * remember which counter to decrement in the matching - * rcu_read_unlock(). - */ - - ACCESS_ONCE(t->rcu_flipctr_idx) = idx; - local_irq_restore(flags); - } -} -EXPORT_SYMBOL_GPL(__rcu_read_lock); - -void __rcu_read_unlock(void) -{ - int idx; - struct task_struct *t = current; - int nesting; - - nesting = ACCESS_ONCE(t->rcu_read_lock_nesting); - if (nesting > 1) { - - /* - * We are still protected by the enclosing rcu_read_lock(), - * so simply decrement the counter. - */ - - t->rcu_read_lock_nesting = nesting - 1; - - } else { - unsigned long flags; - - /* - * Disable local interrupts to prevent the grace-period - * detection state machine from seeing us half-done. - * NMIs can still occur, of course, and might themselves - * contain rcu_read_lock() and rcu_read_unlock(). - */ - - local_irq_save(flags); - - /* - * Outermost nesting of rcu_read_unlock(), so we must - * decrement the current counter for the current CPU. - * This must be done carefully, because NMIs can - * occur at any point in this code, and any rcu_read_lock() - * and rcu_read_unlock() pairs in the NMI handlers - * must interact non-destructively with this code. - * Lots of volatile casts, and -very- careful ordering. - * - * Changes to this code, including this one, must be - * inspected, validated, and tested extremely carefully!!! - */ - - /* - * First, pick up the index. - */ - - idx = ACCESS_ONCE(t->rcu_flipctr_idx); - - /* - * Now that we have fetched the counter index, it is - * safe to decrement the per-task RCU nesting counter. - * After this, any interrupts or NMIs will increment and - * decrement the per-CPU counters. - */ - ACCESS_ONCE(t->rcu_read_lock_nesting) = nesting - 1; - - /* - * It is now safe to decrement this task's nesting count. - * NMIs that occur after this statement will route their - * rcu_read_lock() calls through this "else" clause, and - * will thus start incrementing the per-CPU counter on - * their own. They will also clobber ->rcu_flipctr_idx, - * but that is OK, since we have already fetched it. - */ - - ACCESS_ONCE(RCU_DATA_ME()->rcu_flipctr[idx])--; - local_irq_restore(flags); - } -} -EXPORT_SYMBOL_GPL(__rcu_read_unlock); - -/* - * If a global counter flip has occurred since the last time that we - * advanced callbacks, advance them. Hardware interrupts must be - * disabled when calling this function. - */ -static void __rcu_advance_callbacks(struct rcu_data *rdp) -{ - int cpu; - int i; - int wlc = 0; - - if (rdp->completed != rcu_ctrlblk.completed) { - if (rdp->waitlist[GP_STAGES - 1] != NULL) { - *rdp->donetail = rdp->waitlist[GP_STAGES - 1]; - rdp->donetail = rdp->waittail[GP_STAGES - 1]; - RCU_TRACE_RDP(rcupreempt_trace_move2done, rdp); - } - for (i = GP_STAGES - 2; i >= 0; i--) { - if (rdp->waitlist[i] != NULL) { - rdp->waitlist[i + 1] = rdp->waitlist[i]; - rdp->waittail[i + 1] = rdp->waittail[i]; - wlc++; - } else { - rdp->waitlist[i + 1] = NULL; - rdp->waittail[i + 1] = - &rdp->waitlist[i + 1]; - } - } - if (rdp->nextlist != NULL) { - rdp->waitlist[0] = rdp->nextlist; - rdp->waittail[0] = rdp->nexttail; - wlc++; - rdp->nextlist = NULL; - rdp->nexttail = &rdp->nextlist; - RCU_TRACE_RDP(rcupreempt_trace_move2wait, rdp); - } else { - rdp->waitlist[0] = NULL; - rdp->waittail[0] = &rdp->waitlist[0]; - } - rdp->waitlistcount = wlc; - rdp->completed = rcu_ctrlblk.completed; - } - - /* - * Check to see if this CPU needs to report that it has seen - * the most recent counter flip, thereby declaring that all - * subsequent rcu_read_lock() invocations will respect this flip. - */ - - cpu = raw_smp_processor_id(); - if (per_cpu(rcu_flip_flag, cpu) == rcu_flipped) { - smp_mb(); /* Subsequent counter accesses must see new value */ - per_cpu(rcu_flip_flag, cpu) = rcu_flip_seen; - smp_mb(); /* Subsequent RCU read-side critical sections */ - /* seen -after- acknowledgement. */ - } -} - -#ifdef CONFIG_NO_HZ -static DEFINE_PER_CPU(int, rcu_update_flag); - -/** - * rcu_irq_enter - Called from Hard irq handlers and NMI/SMI. - * - * If the CPU was idle with dynamic ticks active, this updates the - * rcu_dyntick_sched.dynticks to let the RCU handling know that the - * CPU is active. - */ -void rcu_irq_enter(void) -{ - int cpu = smp_processor_id(); - struct rcu_dyntick_sched *rdssp = &per_cpu(rcu_dyntick_sched, cpu); - - if (per_cpu(rcu_update_flag, cpu)) - per_cpu(rcu_update_flag, cpu)++; - - /* - * Only update if we are coming from a stopped ticks mode - * (rcu_dyntick_sched.dynticks is even). - */ - if (!in_interrupt() && - (rdssp->dynticks & 0x1) == 0) { - /* - * The following might seem like we could have a race - * with NMI/SMIs. But this really isn't a problem. - * Here we do a read/modify/write, and the race happens - * when an NMI/SMI comes in after the read and before - * the write. But NMI/SMIs will increment this counter - * twice before returning, so the zero bit will not - * be corrupted by the NMI/SMI which is the most important - * part. - * - * The only thing is that we would bring back the counter - * to a postion that it was in during the NMI/SMI. - * But the zero bit would be set, so the rest of the - * counter would again be ignored. - * - * On return from the IRQ, the counter may have the zero - * bit be 0 and the counter the same as the return from - * the NMI/SMI. If the state machine was so unlucky to - * see that, it still doesn't matter, since all - * RCU read-side critical sections on this CPU would - * have already completed. - */ - rdssp->dynticks++; - /* - * The following memory barrier ensures that any - * rcu_read_lock() primitives in the irq handler - * are seen by other CPUs to follow the above - * increment to rcu_dyntick_sched.dynticks. This is - * required in order for other CPUs to correctly - * determine when it is safe to advance the RCU - * grace-period state machine. - */ - smp_mb(); /* see above block comment. */ - /* - * Since we can't determine the dynamic tick mode from - * the rcu_dyntick_sched.dynticks after this routine, - * we use a second flag to acknowledge that we came - * from an idle state with ticks stopped. - */ - per_cpu(rcu_update_flag, cpu)++; - /* - * If we take an NMI/SMI now, they will also increment - * the rcu_update_flag, and will not update the - * rcu_dyntick_sched.dynticks on exit. That is for - * this IRQ to do. - */ - } -} - -/** - * rcu_irq_exit - Called from exiting Hard irq context. - * - * If the CPU was idle with dynamic ticks active, update the - * rcu_dyntick_sched.dynticks to let the RCU handling be - * aware that the CPU is going back to idle with no ticks. - */ -void rcu_irq_exit(void) -{ - int cpu = smp_processor_id(); - struct rcu_dyntick_sched *rdssp = &per_cpu(rcu_dyntick_sched, cpu); - - /* - * rcu_update_flag is set if we interrupted the CPU - * when it was idle with ticks stopped. - * Once this occurs, we keep track of interrupt nesting - * because a NMI/SMI could also come in, and we still - * only want the IRQ that started the increment of the - * rcu_dyntick_sched.dynticks to be the one that modifies - * it on exit. - */ - if (per_cpu(rcu_update_flag, cpu)) { - if (--per_cpu(rcu_update_flag, cpu)) - return; - - /* This must match the interrupt nesting */ - WARN_ON(in_interrupt()); - - /* - * If an NMI/SMI happens now we are still - * protected by the rcu_dyntick_sched.dynticks being odd. - */ - - /* - * The following memory barrier ensures that any - * rcu_read_unlock() primitives in the irq handler - * are seen by other CPUs to preceed the following - * increment to rcu_dyntick_sched.dynticks. This - * is required in order for other CPUs to determine - * when it is safe to advance the RCU grace-period - * state machine. - */ - smp_mb(); /* see above block comment. */ - rdssp->dynticks++; - WARN_ON(rdssp->dynticks & 0x1); - } -} - -void rcu_nmi_enter(void) -{ - rcu_irq_enter(); -} - -void rcu_nmi_exit(void) -{ - rcu_irq_exit(); -} - -static void dyntick_save_progress_counter(int cpu) -{ - struct rcu_dyntick_sched *rdssp = &per_cpu(rcu_dyntick_sched, cpu); - - rdssp->dynticks_snap = rdssp->dynticks; -} - -static inline int -rcu_try_flip_waitack_needed(int cpu) -{ - long curr; - long snap; - struct rcu_dyntick_sched *rdssp = &per_cpu(rcu_dyntick_sched, cpu); - - curr = rdssp->dynticks; - snap = rdssp->dynticks_snap; - smp_mb(); /* force ordering with cpu entering/leaving dynticks. */ - - /* - * If the CPU remained in dynticks mode for the entire time - * and didn't take any interrupts, NMIs, SMIs, or whatever, - * then it cannot be in the middle of an rcu_read_lock(), so - * the next rcu_read_lock() it executes must use the new value - * of the counter. So we can safely pretend that this CPU - * already acknowledged the counter. - */ - - if ((curr == snap) && ((curr & 0x1) == 0)) - return 0; - - /* - * If the CPU passed through or entered a dynticks idle phase with - * no active irq handlers, then, as above, we can safely pretend - * that this CPU already acknowledged the counter. - */ - - if ((curr - snap) > 2 || (curr & 0x1) == 0) - return 0; - - /* We need this CPU to explicitly acknowledge the counter flip. */ - - return 1; -} - -static inline int -rcu_try_flip_waitmb_needed(int cpu) -{ - long curr; - long snap; - struct rcu_dyntick_sched *rdssp = &per_cpu(rcu_dyntick_sched, cpu); - - curr = rdssp->dynticks; - snap = rdssp->dynticks_snap; - smp_mb(); /* force ordering with cpu entering/leaving dynticks. */ - - /* - * If the CPU remained in dynticks mode for the entire time - * and didn't take any interrupts, NMIs, SMIs, or whatever, - * then it cannot have executed an RCU read-side critical section - * during that time, so there is no need for it to execute a - * memory barrier. - */ - - if ((curr == snap) && ((curr & 0x1) == 0)) - return 0; - - /* - * If the CPU either entered or exited an outermost interrupt, - * SMI, NMI, or whatever handler, then we know that it executed - * a memory barrier when doing so. So we don't need another one. - */ - if (curr != snap) - return 0; - - /* We need the CPU to execute a memory barrier. */ - - return 1; -} - -static void dyntick_save_progress_counter_sched(int cpu) -{ - struct rcu_dyntick_sched *rdssp = &per_cpu(rcu_dyntick_sched, cpu); - - rdssp->sched_dynticks_snap = rdssp->dynticks; -} - -static int rcu_qsctr_inc_needed_dyntick(int cpu) -{ - long curr; - long snap; - struct rcu_dyntick_sched *rdssp = &per_cpu(rcu_dyntick_sched, cpu); - - curr = rdssp->dynticks; - snap = rdssp->sched_dynticks_snap; - smp_mb(); /* force ordering with cpu entering/leaving dynticks. */ - - /* - * If the CPU remained in dynticks mode for the entire time - * and didn't take any interrupts, NMIs, SMIs, or whatever, - * then it cannot be in the middle of an rcu_read_lock(), so - * the next rcu_read_lock() it executes must use the new value - * of the counter. Therefore, this CPU has been in a quiescent - * state the entire time, and we don't need to wait for it. - */ - - if ((curr == snap) && ((curr & 0x1) == 0)) - return 0; - - /* - * If the CPU passed through or entered a dynticks idle phase with - * no active irq handlers, then, as above, this CPU has already - * passed through a quiescent state. - */ - - if ((curr - snap) > 2 || (snap & 0x1) == 0) - return 0; - - /* We need this CPU to go through a quiescent state. */ - - return 1; -} - -#else /* !CONFIG_NO_HZ */ - -# define dyntick_save_progress_counter(cpu) do { } while (0) -# define rcu_try_flip_waitack_needed(cpu) (1) -# define rcu_try_flip_waitmb_needed(cpu) (1) - -# define dyntick_save_progress_counter_sched(cpu) do { } while (0) -# define rcu_qsctr_inc_needed_dyntick(cpu) (1) - -#endif /* CONFIG_NO_HZ */ - -static void save_qsctr_sched(int cpu) -{ - struct rcu_dyntick_sched *rdssp = &per_cpu(rcu_dyntick_sched, cpu); - - rdssp->sched_qs_snap = rdssp->sched_qs; -} - -static inline int rcu_qsctr_inc_needed(int cpu) -{ - struct rcu_dyntick_sched *rdssp = &per_cpu(rcu_dyntick_sched, cpu); - - /* - * If there has been a quiescent state, no more need to wait - * on this CPU. - */ - - if (rdssp->sched_qs != rdssp->sched_qs_snap) { - smp_mb(); /* force ordering with cpu entering schedule(). */ - return 0; - } - - /* We need this CPU to go through a quiescent state. */ - - return 1; -} - -/* - * Get here when RCU is idle. Decide whether we need to - * move out of idle state, and return non-zero if so. - * "Straightforward" approach for the moment, might later - * use callback-list lengths, grace-period duration, or - * some such to determine when to exit idle state. - * Might also need a pre-idle test that does not acquire - * the lock, but let's get the simple case working first... - */ - -static int -rcu_try_flip_idle(void) -{ - int cpu; - - RCU_TRACE_ME(rcupreempt_trace_try_flip_i1); - if (!rcu_pending(smp_processor_id())) { - RCU_TRACE_ME(rcupreempt_trace_try_flip_ie1); - return 0; - } - - /* - * Do the flip. - */ - - RCU_TRACE_ME(rcupreempt_trace_try_flip_g1); - rcu_ctrlblk.completed++; /* stands in for rcu_try_flip_g2 */ - - /* - * Need a memory barrier so that other CPUs see the new - * counter value before they see the subsequent change of all - * the rcu_flip_flag instances to rcu_flipped. - */ - - smp_mb(); /* see above block comment. */ - - /* Now ask each CPU for acknowledgement of the flip. */ - - for_each_cpu(cpu, to_cpumask(rcu_cpu_online_map)) { - per_cpu(rcu_flip_flag, cpu) = rcu_flipped; - dyntick_save_progress_counter(cpu); - } - - return 1; -} - -/* - * Wait for CPUs to acknowledge the flip. - */ - -static int -rcu_try_flip_waitack(void) -{ - int cpu; - - RCU_TRACE_ME(rcupreempt_trace_try_flip_a1); - for_each_cpu(cpu, to_cpumask(rcu_cpu_online_map)) - if (rcu_try_flip_waitack_needed(cpu) && - per_cpu(rcu_flip_flag, cpu) != rcu_flip_seen) { - RCU_TRACE_ME(rcupreempt_trace_try_flip_ae1); - return 0; - } - - /* - * Make sure our checks above don't bleed into subsequent - * waiting for the sum of the counters to reach zero. - */ - - smp_mb(); /* see above block comment. */ - RCU_TRACE_ME(rcupreempt_trace_try_flip_a2); - return 1; -} - -/* - * Wait for collective ``last'' counter to reach zero, - * then tell all CPUs to do an end-of-grace-period memory barrier. - */ - -static int -rcu_try_flip_waitzero(void) -{ - int cpu; - int lastidx = !(rcu_ctrlblk.completed & 0x1); - int sum = 0; - - /* Check to see if the sum of the "last" counters is zero. */ - - RCU_TRACE_ME(rcupreempt_trace_try_flip_z1); - for_each_possible_cpu(cpu) - sum += RCU_DATA_CPU(cpu)->rcu_flipctr[lastidx]; - if (sum != 0) { - RCU_TRACE_ME(rcupreempt_trace_try_flip_ze1); - return 0; - } - - /* - * This ensures that the other CPUs see the call for - * memory barriers -after- the sum to zero has been - * detected here - */ - smp_mb(); /* ^^^^^^^^^^^^ */ - - /* Call for a memory barrier from each CPU. */ - for_each_cpu(cpu, to_cpumask(rcu_cpu_online_map)) { - per_cpu(rcu_mb_flag, cpu) = rcu_mb_needed; - dyntick_save_progress_counter(cpu); - } - - RCU_TRACE_ME(rcupreempt_trace_try_flip_z2); - return 1; -} - -/* - * Wait for all CPUs to do their end-of-grace-period memory barrier. - * Return 0 once all CPUs have done so. - */ - -static int -rcu_try_flip_waitmb(void) -{ - int cpu; - - RCU_TRACE_ME(rcupreempt_trace_try_flip_m1); - for_each_cpu(cpu, to_cpumask(rcu_cpu_online_map)) - if (rcu_try_flip_waitmb_needed(cpu) && - per_cpu(rcu_mb_flag, cpu) != rcu_mb_done) { - RCU_TRACE_ME(rcupreempt_trace_try_flip_me1); - return 0; - } - - smp_mb(); /* Ensure that the above checks precede any following flip. */ - RCU_TRACE_ME(rcupreempt_trace_try_flip_m2); - return 1; -} - -/* - * Attempt a single flip of the counters. Remember, a single flip does - * -not- constitute a grace period. Instead, the interval between - * at least GP_STAGES consecutive flips is a grace period. - * - * If anyone is nuts enough to run this CONFIG_PREEMPT_RCU implementation - * on a large SMP, they might want to use a hierarchical organization of - * the per-CPU-counter pairs. - */ -static void rcu_try_flip(void) -{ - unsigned long flags; - - RCU_TRACE_ME(rcupreempt_trace_try_flip_1); - if (unlikely(!spin_trylock_irqsave(&rcu_ctrlblk.fliplock, flags))) { - RCU_TRACE_ME(rcupreempt_trace_try_flip_e1); - return; - } - - /* - * Take the next transition(s) through the RCU grace-period - * flip-counter state machine. - */ - - switch (rcu_ctrlblk.rcu_try_flip_state) { - case rcu_try_flip_idle_state: - if (rcu_try_flip_idle()) - rcu_ctrlblk.rcu_try_flip_state = - rcu_try_flip_waitack_state; - break; - case rcu_try_flip_waitack_state: - if (rcu_try_flip_waitack()) - rcu_ctrlblk.rcu_try_flip_state = - rcu_try_flip_waitzero_state; - break; - case rcu_try_flip_waitzero_state: - if (rcu_try_flip_waitzero()) - rcu_ctrlblk.rcu_try_flip_state = - rcu_try_flip_waitmb_state; - break; - case rcu_try_flip_waitmb_state: - if (rcu_try_flip_waitmb()) - rcu_ctrlblk.rcu_try_flip_state = - rcu_try_flip_idle_state; - } - spin_unlock_irqrestore(&rcu_ctrlblk.fliplock, flags); -} - -/* - * Check to see if this CPU needs to do a memory barrier in order to - * ensure that any prior RCU read-side critical sections have committed - * their counter manipulations and critical-section memory references - * before declaring the grace period to be completed. - */ -static void rcu_check_mb(int cpu) -{ - if (per_cpu(rcu_mb_flag, cpu) == rcu_mb_needed) { - smp_mb(); /* Ensure RCU read-side accesses are visible. */ - per_cpu(rcu_mb_flag, cpu) = rcu_mb_done; - } -} - -void rcu_check_callbacks(int cpu, int user) -{ - unsigned long flags; - struct rcu_data *rdp; - - if (!rcu_pending(cpu)) - return; /* if nothing for RCU to do. */ - - /* - * If this CPU took its interrupt from user mode or from the - * idle loop, and this is not a nested interrupt, then - * this CPU has to have exited all prior preept-disable - * sections of code. So invoke rcu_sched_qs() to note this. - * - * The memory barrier is needed to handle the case where - * writes from a preempt-disable section of code get reordered - * into schedule() by this CPU's write buffer. So the memory - * barrier makes sure that the rcu_sched_qs() is seen by other - * CPUs to happen after any such write. - */ - - rdp = RCU_DATA_CPU(cpu); - if (user || - (idle_cpu(cpu) && !in_softirq() && - hardirq_count() <= (1 << HARDIRQ_SHIFT))) { - smp_mb(); /* Guard against aggressive schedule(). */ - rcu_sched_qs(cpu); - } - - rcu_check_mb(cpu); - if (rcu_ctrlblk.completed == rdp->completed) - rcu_try_flip(); - spin_lock_irqsave(&rdp->lock, flags); - RCU_TRACE_RDP(rcupreempt_trace_check_callbacks, rdp); - __rcu_advance_callbacks(rdp); - if (rdp->donelist == NULL) { - spin_unlock_irqrestore(&rdp->lock, flags); - } else { - spin_unlock_irqrestore(&rdp->lock, flags); - raise_softirq(RCU_SOFTIRQ); - } -} - -/* - * Needed by dynticks, to make sure all RCU processing has finished - * when we go idle: - */ -void rcu_advance_callbacks(int cpu, int user) -{ - unsigned long flags; - struct rcu_data *rdp = RCU_DATA_CPU(cpu); - - if (rcu_ctrlblk.completed == rdp->completed) { - rcu_try_flip(); - if (rcu_ctrlblk.completed == rdp->completed) - return; - } - spin_lock_irqsave(&rdp->lock, flags); - RCU_TRACE_RDP(rcupreempt_trace_check_callbacks, rdp); - __rcu_advance_callbacks(rdp); - spin_unlock_irqrestore(&rdp->lock, flags); -} - -#ifdef CONFIG_HOTPLUG_CPU -#define rcu_offline_cpu_enqueue(srclist, srctail, dstlist, dsttail) do { \ - *dsttail = srclist; \ - if (srclist != NULL) { \ - dsttail = srctail; \ - srclist = NULL; \ - srctail = &srclist;\ - } \ - } while (0) - -void rcu_offline_cpu(int cpu) -{ - int i; - struct rcu_head *list = NULL; - unsigned long flags; - struct rcu_data *rdp = RCU_DATA_CPU(cpu); - struct rcu_head *schedlist = NULL; - struct rcu_head **schedtail = &schedlist; - struct rcu_head **tail = &list; - - /* - * Remove all callbacks from the newly dead CPU, retaining order. - * Otherwise rcu_barrier() will fail - */ - - spin_lock_irqsave(&rdp->lock, flags); - rcu_offline_cpu_enqueue(rdp->donelist, rdp->donetail, list, tail); - for (i = GP_STAGES - 1; i >= 0; i--) - rcu_offline_cpu_enqueue(rdp->waitlist[i], rdp->waittail[i], - list, tail); - rcu_offline_cpu_enqueue(rdp->nextlist, rdp->nexttail, list, tail); - rcu_offline_cpu_enqueue(rdp->waitschedlist, rdp->waitschedtail, - schedlist, schedtail); - rcu_offline_cpu_enqueue(rdp->nextschedlist, rdp->nextschedtail, - schedlist, schedtail); - rdp->rcu_sched_sleeping = 0; - spin_unlock_irqrestore(&rdp->lock, flags); - rdp->waitlistcount = 0; - - /* Disengage the newly dead CPU from the grace-period computation. */ - - spin_lock_irqsave(&rcu_ctrlblk.fliplock, flags); - rcu_check_mb(cpu); - if (per_cpu(rcu_flip_flag, cpu) == rcu_flipped) { - smp_mb(); /* Subsequent counter accesses must see new value */ - per_cpu(rcu_flip_flag, cpu) = rcu_flip_seen; - smp_mb(); /* Subsequent RCU read-side critical sections */ - /* seen -after- acknowledgement. */ - } - - cpumask_clear_cpu(cpu, to_cpumask(rcu_cpu_online_map)); - - spin_unlock_irqrestore(&rcu_ctrlblk.fliplock, flags); - - /* - * Place the removed callbacks on the current CPU's queue. - * Make them all start a new grace period: simple approach, - * in theory could starve a given set of callbacks, but - * you would need to be doing some serious CPU hotplugging - * to make this happen. If this becomes a problem, adding - * a synchronize_rcu() to the hotplug path would be a simple - * fix. - */ - - local_irq_save(flags); /* disable preempt till we know what lock. */ - rdp = RCU_DATA_ME(); - spin_lock(&rdp->lock); - *rdp->nexttail = list; - if (list) - rdp->nexttail = tail; - *rdp->nextschedtail = schedlist; - if (schedlist) - rdp->nextschedtail = schedtail; - spin_unlock_irqrestore(&rdp->lock, flags); -} - -#else /* #ifdef CONFIG_HOTPLUG_CPU */ - -void rcu_offline_cpu(int cpu) -{ -} - -#endif /* #else #ifdef CONFIG_HOTPLUG_CPU */ - -void __cpuinit rcu_online_cpu(int cpu) -{ - unsigned long flags; - struct rcu_data *rdp; - - spin_lock_irqsave(&rcu_ctrlblk.fliplock, flags); - cpumask_set_cpu(cpu, to_cpumask(rcu_cpu_online_map)); - spin_unlock_irqrestore(&rcu_ctrlblk.fliplock, flags); - - /* - * The rcu_sched grace-period processing might have bypassed - * this CPU, given that it was not in the rcu_cpu_online_map - * when the grace-period scan started. This means that the - * grace-period task might sleep. So make sure that if this - * should happen, the first callback posted to this CPU will - * wake up the grace-period task if need be. - */ - - rdp = RCU_DATA_CPU(cpu); - spin_lock_irqsave(&rdp->lock, flags); - rdp->rcu_sched_sleeping = 1; - spin_unlock_irqrestore(&rdp->lock, flags); -} - -static void rcu_process_callbacks(struct softirq_action *unused) -{ - unsigned long flags; - struct rcu_head *next, *list; - struct rcu_data *rdp; - - local_irq_save(flags); - rdp = RCU_DATA_ME(); - spin_lock(&rdp->lock); - list = rdp->donelist; - if (list == NULL) { - spin_unlock_irqrestore(&rdp->lock, flags); - return; - } - rdp->donelist = NULL; - rdp->donetail = &rdp->donelist; - RCU_TRACE_RDP(rcupreempt_trace_done_remove, rdp); - spin_unlock_irqrestore(&rdp->lock, flags); - while (list) { - next = list->next; - list->func(list); - list = next; - RCU_TRACE_ME(rcupreempt_trace_invoke); - } -} - -void call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) -{ - unsigned long flags; - struct rcu_data *rdp; - - head->func = func; - head->next = NULL; - local_irq_save(flags); - rdp = RCU_DATA_ME(); - spin_lock(&rdp->lock); - __rcu_advance_callbacks(rdp); - *rdp->nexttail = head; - rdp->nexttail = &head->next; - RCU_TRACE_RDP(rcupreempt_trace_next_add, rdp); - spin_unlock_irqrestore(&rdp->lock, flags); -} -EXPORT_SYMBOL_GPL(call_rcu); - -void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) -{ - unsigned long flags; - struct rcu_data *rdp; - int wake_gp = 0; - - head->func = func; - head->next = NULL; - local_irq_save(flags); - rdp = RCU_DATA_ME(); - spin_lock(&rdp->lock); - *rdp->nextschedtail = head; - rdp->nextschedtail = &head->next; - if (rdp->rcu_sched_sleeping) { - - /* Grace-period processing might be sleeping... */ - - rdp->rcu_sched_sleeping = 0; - wake_gp = 1; - } - spin_unlock_irqrestore(&rdp->lock, flags); - if (wake_gp) { - - /* Wake up grace-period processing, unless someone beat us. */ - - spin_lock_irqsave(&rcu_ctrlblk.schedlock, flags); - if (rcu_ctrlblk.sched_sleep != rcu_sched_sleeping) - wake_gp = 0; - rcu_ctrlblk.sched_sleep = rcu_sched_not_sleeping; - spin_unlock_irqrestore(&rcu_ctrlblk.schedlock, flags); - if (wake_gp) - wake_up_interruptible(&rcu_ctrlblk.sched_wq); - } -} -EXPORT_SYMBOL_GPL(call_rcu_sched); - -/* - * Wait until all currently running preempt_disable() code segments - * (including hardware-irq-disable segments) complete. Note that - * in -rt this does -not- necessarily result in all currently executing - * interrupt -handlers- having completed. - */ -void __synchronize_sched(void) -{ - struct rcu_synchronize rcu; - - if (num_online_cpus() == 1) - return; /* blocking is gp if only one CPU! */ - - init_completion(&rcu.completion); - /* Will wake me after RCU finished. */ - call_rcu_sched(&rcu.head, wakeme_after_rcu); - /* Wait for it. */ - wait_for_completion(&rcu.completion); -} -EXPORT_SYMBOL_GPL(__synchronize_sched); - -/* - * kthread function that manages call_rcu_sched grace periods. - */ -static int rcu_sched_grace_period(void *arg) -{ - int couldsleep; /* might sleep after current pass. */ - int couldsleepnext = 0; /* might sleep after next pass. */ - int cpu; - unsigned long flags; - struct rcu_data *rdp; - int ret; - - /* - * Each pass through the following loop handles one - * rcu_sched grace period cycle. - */ - do { - /* Save each CPU's current state. */ - - for_each_online_cpu(cpu) { - dyntick_save_progress_counter_sched(cpu); - save_qsctr_sched(cpu); - } - - /* - * Sleep for about an RCU grace-period's worth to - * allow better batching and to consume less CPU. - */ - schedule_timeout_interruptible(RCU_SCHED_BATCH_TIME); - - /* - * If there was nothing to do last time, prepare to - * sleep at the end of the current grace period cycle. - */ - couldsleep = couldsleepnext; - couldsleepnext = 1; - if (couldsleep) { - spin_lock_irqsave(&rcu_ctrlblk.schedlock, flags); - rcu_ctrlblk.sched_sleep = rcu_sched_sleep_prep; - spin_unlock_irqrestore(&rcu_ctrlblk.schedlock, flags); - } - - /* - * Wait on each CPU in turn to have either visited - * a quiescent state or been in dynticks-idle mode. - */ - for_each_online_cpu(cpu) { - while (rcu_qsctr_inc_needed(cpu) && - rcu_qsctr_inc_needed_dyntick(cpu)) { - /* resched_cpu(cpu); @@@ */ - schedule_timeout_interruptible(1); - } - } - - /* Advance callbacks for each CPU. */ - - for_each_online_cpu(cpu) { - - rdp = RCU_DATA_CPU(cpu); - spin_lock_irqsave(&rdp->lock, flags); - - /* - * We are running on this CPU irq-disabled, so no - * CPU can go offline until we re-enable irqs. - * The current CPU might have already gone - * offline (between the for_each_offline_cpu and - * the spin_lock_irqsave), but in that case all its - * callback lists will be empty, so no harm done. - * - * Advance the callbacks! We share normal RCU's - * donelist, since callbacks are invoked the - * same way in either case. - */ - if (rdp->waitschedlist != NULL) { - *rdp->donetail = rdp->waitschedlist; - rdp->donetail = rdp->waitschedtail; - - /* - * Next rcu_check_callbacks() will - * do the required raise_softirq(). - */ - } - if (rdp->nextschedlist != NULL) { - rdp->waitschedlist = rdp->nextschedlist; - rdp->waitschedtail = rdp->nextschedtail; - couldsleep = 0; - couldsleepnext = 0; - } else { - rdp->waitschedlist = NULL; - rdp->waitschedtail = &rdp->waitschedlist; - } - rdp->nextschedlist = NULL; - rdp->nextschedtail = &rdp->nextschedlist; - - /* Mark sleep intention. */ - - rdp->rcu_sched_sleeping = couldsleep; - - spin_unlock_irqrestore(&rdp->lock, flags); - } - - /* If we saw callbacks on the last scan, go deal with them. */ - - if (!couldsleep) - continue; - - /* Attempt to block... */ - - spin_lock_irqsave(&rcu_ctrlblk.schedlock, flags); - if (rcu_ctrlblk.sched_sleep != rcu_sched_sleep_prep) { - - /* - * Someone posted a callback after we scanned. - * Go take care of it. - */ - spin_unlock_irqrestore(&rcu_ctrlblk.schedlock, flags); - couldsleepnext = 0; - continue; - } - - /* Block until the next person posts a callback. */ - - rcu_ctrlblk.sched_sleep = rcu_sched_sleeping; - spin_unlock_irqrestore(&rcu_ctrlblk.schedlock, flags); - ret = 0; /* unused */ - __wait_event_interruptible(rcu_ctrlblk.sched_wq, - rcu_ctrlblk.sched_sleep != rcu_sched_sleeping, - ret); - - couldsleepnext = 0; - - } while (!kthread_should_stop()); - - return (0); -} - -/* - * Check to see if any future RCU-related work will need to be done - * by the current CPU, even if none need be done immediately, returning - * 1 if so. Assumes that notifiers would take care of handling any - * outstanding requests from the RCU core. - * - * This function is part of the RCU implementation; it is -not- - * an exported member of the RCU API. - */ -int rcu_needs_cpu(int cpu) -{ - struct rcu_data *rdp = RCU_DATA_CPU(cpu); - - return (rdp->donelist != NULL || - !!rdp->waitlistcount || - rdp->nextlist != NULL || - rdp->nextschedlist != NULL || - rdp->waitschedlist != NULL); -} - -static int rcu_pending(int cpu) -{ - struct rcu_data *rdp = RCU_DATA_CPU(cpu); - - /* The CPU has at least one callback queued somewhere. */ - - if (rdp->donelist != NULL || - !!rdp->waitlistcount || - rdp->nextlist != NULL || - rdp->nextschedlist != NULL || - rdp->waitschedlist != NULL) - return 1; - - /* The RCU core needs an acknowledgement from this CPU. */ - - if ((per_cpu(rcu_flip_flag, cpu) == rcu_flipped) || - (per_cpu(rcu_mb_flag, cpu) == rcu_mb_needed)) - return 1; - - /* This CPU has fallen behind the global grace-period number. */ - - if (rdp->completed != rcu_ctrlblk.completed) - return 1; - - /* Nothing needed from this CPU. */ - - return 0; -} - -int __cpuinit rcu_cpu_notify(struct notifier_block *self, - unsigned long action, void *hcpu) -{ - long cpu = (long)hcpu; - - switch (action) { - case CPU_UP_PREPARE: - case CPU_UP_PREPARE_FROZEN: - rcu_online_cpu(cpu); - break; - case CPU_UP_CANCELED: - case CPU_UP_CANCELED_FROZEN: - case CPU_DEAD: - case CPU_DEAD_FROZEN: - rcu_offline_cpu(cpu); - break; - default: - break; - } - return NOTIFY_OK; -} - -void __init __rcu_init(void) -{ - int cpu; - int i; - struct rcu_data *rdp; - - printk(KERN_NOTICE "Preemptible RCU implementation.\n"); - for_each_possible_cpu(cpu) { - rdp = RCU_DATA_CPU(cpu); - spin_lock_init(&rdp->lock); - rdp->completed = 0; - rdp->waitlistcount = 0; - rdp->nextlist = NULL; - rdp->nexttail = &rdp->nextlist; - for (i = 0; i < GP_STAGES; i++) { - rdp->waitlist[i] = NULL; - rdp->waittail[i] = &rdp->waitlist[i]; - } - rdp->donelist = NULL; - rdp->donetail = &rdp->donelist; - rdp->rcu_flipctr[0] = 0; - rdp->rcu_flipctr[1] = 0; - rdp->nextschedlist = NULL; - rdp->nextschedtail = &rdp->nextschedlist; - rdp->waitschedlist = NULL; - rdp->waitschedtail = &rdp->waitschedlist; - rdp->rcu_sched_sleeping = 0; - } - open_softirq(RCU_SOFTIRQ, rcu_process_callbacks); -} - -/* - * Late-boot-time RCU initialization that must wait until after scheduler - * has been initialized. - */ -void __init rcu_init_sched(void) -{ - rcu_sched_grace_period_task = kthread_run(rcu_sched_grace_period, - NULL, - "rcu_sched_grace_period"); - WARN_ON(IS_ERR(rcu_sched_grace_period_task)); -} - -#ifdef CONFIG_RCU_TRACE -long *rcupreempt_flipctr(int cpu) -{ - return &RCU_DATA_CPU(cpu)->rcu_flipctr[0]; -} -EXPORT_SYMBOL_GPL(rcupreempt_flipctr); - -int rcupreempt_flip_flag(int cpu) -{ - return per_cpu(rcu_flip_flag, cpu); -} -EXPORT_SYMBOL_GPL(rcupreempt_flip_flag); - -int rcupreempt_mb_flag(int cpu) -{ - return per_cpu(rcu_mb_flag, cpu); -} -EXPORT_SYMBOL_GPL(rcupreempt_mb_flag); - -char *rcupreempt_try_flip_state_name(void) -{ - return rcu_try_flip_state_names[rcu_ctrlblk.rcu_try_flip_state]; -} -EXPORT_SYMBOL_GPL(rcupreempt_try_flip_state_name); - -struct rcupreempt_trace *rcupreempt_trace_cpu(int cpu) -{ - struct rcu_data *rdp = RCU_DATA_CPU(cpu); - - return &rdp->trace; -} -EXPORT_SYMBOL_GPL(rcupreempt_trace_cpu); - -#endif /* #ifdef RCU_TRACE */ diff --git a/kernel/rcupreempt_trace.c b/kernel/rcupreempt_trace.c deleted file mode 100644 index 11640346a507..000000000000 --- a/kernel/rcupreempt_trace.c +++ /dev/null @@ -1,335 +0,0 @@ -/* - * Read-Copy Update tracing for realtime 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, write to the Free Software - * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. - * - * Copyright IBM Corporation, 2006 - * - * Papers: http://www.rdrop.com/users/paulmck/RCU - * - * For detailed explanation of Read-Copy Update mechanism see - - * Documentation/RCU/ *.txt - * - */ -#include -#include -#include -#include -#include -#include -#include -#include -#include -#include -#include -#include -#include -#include -#include -#include -#include -#include -#include - -static struct mutex rcupreempt_trace_mutex; -static char *rcupreempt_trace_buf; -#define RCUPREEMPT_TRACE_BUF_SIZE 4096 - -void rcupreempt_trace_move2done(struct rcupreempt_trace *trace) -{ - trace->done_length += trace->wait_length; - trace->done_add += trace->wait_length; - trace->wait_length = 0; -} -void rcupreempt_trace_move2wait(struct rcupreempt_trace *trace) -{ - trace->wait_length += trace->next_length; - trace->wait_add += trace->next_length; - trace->next_length = 0; -} -void rcupreempt_trace_try_flip_1(struct rcupreempt_trace *trace) -{ - atomic_inc(&trace->rcu_try_flip_1); -} -void rcupreempt_trace_try_flip_e1(struct rcupreempt_trace *trace) -{ - atomic_inc(&trace->rcu_try_flip_e1); -} -void rcupreempt_trace_try_flip_i1(struct rcupreempt_trace *trace) -{ - trace->rcu_try_flip_i1++; -} -void rcupreempt_trace_try_flip_ie1(struct rcupreempt_trace *trace) -{ - trace->rcu_try_flip_ie1++; -} -void rcupreempt_trace_try_flip_g1(struct rcupreempt_trace *trace) -{ - trace->rcu_try_flip_g1++; -} -void rcupreempt_trace_try_flip_a1(struct rcupreempt_trace *trace) -{ - trace->rcu_try_flip_a1++; -} -void rcupreempt_trace_try_flip_ae1(struct rcupreempt_trace *trace) -{ - trace->rcu_try_flip_ae1++; -} -void rcupreempt_trace_try_flip_a2(struct rcupreempt_trace *trace) -{ - trace->rcu_try_flip_a2++; -} -void rcupreempt_trace_try_flip_z1(struct rcupreempt_trace *trace) -{ - trace->rcu_try_flip_z1++; -} -void rcupreempt_trace_try_flip_ze1(struct rcupreempt_trace *trace) -{ - trace->rcu_try_flip_ze1++; -} -void rcupreempt_trace_try_flip_z2(struct rcupreempt_trace *trace) -{ - trace->rcu_try_flip_z2++; -} -void rcupreempt_trace_try_flip_m1(struct rcupreempt_trace *trace) -{ - trace->rcu_try_flip_m1++; -} -void rcupreempt_trace_try_flip_me1(struct rcupreempt_trace *trace) -{ - trace->rcu_try_flip_me1++; -} -void rcupreempt_trace_try_flip_m2(struct rcupreempt_trace *trace) -{ - trace->rcu_try_flip_m2++; -} -void rcupreempt_trace_check_callbacks(struct rcupreempt_trace *trace) -{ - trace->rcu_check_callbacks++; -} -void rcupreempt_trace_done_remove(struct rcupreempt_trace *trace) -{ - trace->done_remove += trace->done_length; - trace->done_length = 0; -} -void rcupreempt_trace_invoke(struct rcupreempt_trace *trace) -{ - atomic_inc(&trace->done_invoked); -} -void rcupreempt_trace_next_add(struct rcupreempt_trace *trace) -{ - trace->next_add++; - trace->next_length++; -} - -static void rcupreempt_trace_sum(struct rcupreempt_trace *sp) -{ - struct rcupreempt_trace *cp; - int cpu; - - memset(sp, 0, sizeof(*sp)); - for_each_possible_cpu(cpu) { - cp = rcupreempt_trace_cpu(cpu); - sp->next_length += cp->next_length; - sp->next_add += cp->next_add; - sp->wait_length += cp->wait_length; - sp->wait_add += cp->wait_add; - sp->done_length += cp->done_length; - sp->done_add += cp->done_add; - sp->done_remove += cp->done_remove; - atomic_add(atomic_read(&cp->done_invoked), &sp->done_invoked); - sp->rcu_check_callbacks += cp->rcu_check_callbacks; - atomic_add(atomic_read(&cp->rcu_try_flip_1), - &sp->rcu_try_flip_1); - atomic_add(atomic_read(&cp->rcu_try_flip_e1), - &sp->rcu_try_flip_e1); - sp->rcu_try_flip_i1 += cp->rcu_try_flip_i1; - sp->rcu_try_flip_ie1 += cp->rcu_try_flip_ie1; - sp->rcu_try_flip_g1 += cp->rcu_try_flip_g1; - sp->rcu_try_flip_a1 += cp->rcu_try_flip_a1; - sp->rcu_try_flip_ae1 += cp->rcu_try_flip_ae1; - sp->rcu_try_flip_a2 += cp->rcu_try_flip_a2; - sp->rcu_try_flip_z1 += cp->rcu_try_flip_z1; - sp->rcu_try_flip_ze1 += cp->rcu_try_flip_ze1; - sp->rcu_try_flip_z2 += cp->rcu_try_flip_z2; - sp->rcu_try_flip_m1 += cp->rcu_try_flip_m1; - sp->rcu_try_flip_me1 += cp->rcu_try_flip_me1; - sp->rcu_try_flip_m2 += cp->rcu_try_flip_m2; - } -} - -static ssize_t rcustats_read(struct file *filp, char __user *buffer, - size_t count, loff_t *ppos) -{ - struct rcupreempt_trace trace; - ssize_t bcount; - int cnt = 0; - - rcupreempt_trace_sum(&trace); - mutex_lock(&rcupreempt_trace_mutex); - snprintf(&rcupreempt_trace_buf[cnt], RCUPREEMPT_TRACE_BUF_SIZE - cnt, - "ggp=%ld rcc=%ld\n", - rcu_batches_completed(), - trace.rcu_check_callbacks); - snprintf(&rcupreempt_trace_buf[cnt], RCUPREEMPT_TRACE_BUF_SIZE - cnt, - "na=%ld nl=%ld wa=%ld wl=%ld da=%ld dl=%ld dr=%ld di=%d\n" - "1=%d e1=%d i1=%ld ie1=%ld g1=%ld a1=%ld ae1=%ld a2=%ld\n" - "z1=%ld ze1=%ld z2=%ld m1=%ld me1=%ld m2=%ld\n", - - trace.next_add, trace.next_length, - trace.wait_add, trace.wait_length, - trace.done_add, trace.done_length, - trace.done_remove, atomic_read(&trace.done_invoked), - atomic_read(&trace.rcu_try_flip_1), - atomic_read(&trace.rcu_try_flip_e1), - trace.rcu_try_flip_i1, trace.rcu_try_flip_ie1, - trace.rcu_try_flip_g1, - trace.rcu_try_flip_a1, trace.rcu_try_flip_ae1, - trace.rcu_try_flip_a2, - trace.rcu_try_flip_z1, trace.rcu_try_flip_ze1, - trace.rcu_try_flip_z2, - trace.rcu_try_flip_m1, trace.rcu_try_flip_me1, - trace.rcu_try_flip_m2); - bcount = simple_read_from_buffer(buffer, count, ppos, - rcupreempt_trace_buf, strlen(rcupreempt_trace_buf)); - mutex_unlock(&rcupreempt_trace_mutex); - return bcount; -} - -static ssize_t rcugp_read(struct file *filp, char __user *buffer, - size_t count, loff_t *ppos) -{ - long oldgp = rcu_batches_completed(); - ssize_t bcount; - - mutex_lock(&rcupreempt_trace_mutex); - synchronize_rcu(); - snprintf(rcupreempt_trace_buf, RCUPREEMPT_TRACE_BUF_SIZE, - "oldggp=%ld newggp=%ld\n", oldgp, rcu_batches_completed()); - bcount = simple_read_from_buffer(buffer, count, ppos, - rcupreempt_trace_buf, strlen(rcupreempt_trace_buf)); - mutex_unlock(&rcupreempt_trace_mutex); - return bcount; -} - -static ssize_t rcuctrs_read(struct file *filp, char __user *buffer, - size_t count, loff_t *ppos) -{ - int cnt = 0; - int cpu; - int f = rcu_batches_completed() & 0x1; - ssize_t bcount; - - mutex_lock(&rcupreempt_trace_mutex); - - cnt += snprintf(&rcupreempt_trace_buf[cnt], RCUPREEMPT_TRACE_BUF_SIZE, - "CPU last cur F M\n"); - for_each_possible_cpu(cpu) { - long *flipctr = rcupreempt_flipctr(cpu); - cnt += snprintf(&rcupreempt_trace_buf[cnt], - RCUPREEMPT_TRACE_BUF_SIZE - cnt, - "%3d%c %4ld %3ld %d %d\n", - cpu, - cpu_is_offline(cpu) ? '!' : ' ', - flipctr[!f], - flipctr[f], - rcupreempt_flip_flag(cpu), - rcupreempt_mb_flag(cpu)); - } - cnt += snprintf(&rcupreempt_trace_buf[cnt], - RCUPREEMPT_TRACE_BUF_SIZE - cnt, - "ggp = %ld, state = %s\n", - rcu_batches_completed(), - rcupreempt_try_flip_state_name()); - cnt += snprintf(&rcupreempt_trace_buf[cnt], - RCUPREEMPT_TRACE_BUF_SIZE - cnt, - "\n"); - bcount = simple_read_from_buffer(buffer, count, ppos, - rcupreempt_trace_buf, strlen(rcupreempt_trace_buf)); - mutex_unlock(&rcupreempt_trace_mutex); - return bcount; -} - -static struct file_operations rcustats_fops = { - .owner = THIS_MODULE, - .read = rcustats_read, -}; - -static struct file_operations rcugp_fops = { - .owner = THIS_MODULE, - .read = rcugp_read, -}; - -static struct file_operations rcuctrs_fops = { - .owner = THIS_MODULE, - .read = rcuctrs_read, -}; - -static struct dentry *rcudir, *statdir, *ctrsdir, *gpdir; -static int rcupreempt_debugfs_init(void) -{ - rcudir = debugfs_create_dir("rcu", NULL); - if (!rcudir) - goto out; - statdir = debugfs_create_file("rcustats", 0444, rcudir, - NULL, &rcustats_fops); - if (!statdir) - goto free_out; - - gpdir = debugfs_create_file("rcugp", 0444, rcudir, NULL, &rcugp_fops); - if (!gpdir) - goto free_out; - - ctrsdir = debugfs_create_file("rcuctrs", 0444, rcudir, - NULL, &rcuctrs_fops); - if (!ctrsdir) - goto free_out; - return 0; -free_out: - if (statdir) - debugfs_remove(statdir); - if (gpdir) - debugfs_remove(gpdir); - debugfs_remove(rcudir); -out: - return 1; -} - -static int __init rcupreempt_trace_init(void) -{ - int ret; - - mutex_init(&rcupreempt_trace_mutex); - rcupreempt_trace_buf = kmalloc(RCUPREEMPT_TRACE_BUF_SIZE, GFP_KERNEL); - if (!rcupreempt_trace_buf) - return 1; - ret = rcupreempt_debugfs_init(); - if (ret) - kfree(rcupreempt_trace_buf); - return ret; -} - -static void __exit rcupreempt_trace_cleanup(void) -{ - debugfs_remove(statdir); - debugfs_remove(gpdir); - debugfs_remove(ctrsdir); - debugfs_remove(rcudir); - kfree(rcupreempt_trace_buf); -} - - -module_init(rcupreempt_trace_init); -module_exit(rcupreempt_trace_cleanup); diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index f87fb0c8f924..82fbc49728df 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -725,7 +725,7 @@ config RCU_TORTURE_TEST_RUNNABLE config RCU_CPU_STALL_DETECTOR bool "Check for stalled CPUs delaying RCU grace periods" - depends on CLASSIC_RCU || TREE_RCU || TREE_PREEMPT_RCU + depends on TREE_RCU || TREE_PREEMPT_RCU default n help This option causes RCU to printk information on which -- cgit v1.2.3-59-g8ed1b From 7c614d6461399acca5c0ba444f5db49cb332fc08 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Mon, 24 Aug 2009 09:42:00 -0700 Subject: rcu: Add "notrace" to RCU function headers used by ftrace Both rcu_read_lock_sched_notrace() and rcu_read_unlock_sched_notrace() are used by ftrace, and thus need to be marked "notrace". Unfortunately, my naive assumption that gcc would see the inner "notrace" does not hold. Kudos to Lai Jiangshan for noting this. Reported-by: Ingo Molnar Bug-spotted-by: Lai Jiangshan Signed-off-by: Paul E. McKenney Cc: laijs@cn.fujitsu.com Cc: dipankar@in.ibm.com Cc: akpm@linux-foundation.org Cc: mathieu.desnoyers@polymtl.ca Cc: josht@linux.vnet.ibm.com Cc: dvhltc@us.ibm.com Cc: niv@us.ibm.com Cc: peterz@infradead.org Cc: rostedt@goodmis.org LKML-Reference: <12511321213243-git-send-email-> Signed-off-by: Ingo Molnar --- include/linux/rcupdate.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'include') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index ec90fc34fea9..8b4422c558da 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -191,7 +191,7 @@ static inline void rcu_read_lock_sched(void) __acquire(RCU_SCHED); rcu_read_acquire(); } -static inline void rcu_read_lock_sched_notrace(void) +static inline notrace void rcu_read_lock_sched_notrace(void) { preempt_disable_notrace(); __acquire(RCU_SCHED); @@ -209,7 +209,7 @@ static inline void rcu_read_unlock_sched(void) __release(RCU_SCHED); preempt_enable(); } -static inline void rcu_read_unlock_sched_notrace(void) +static inline notrace void rcu_read_unlock_sched_notrace(void) { rcu_read_release(); __release(RCU_SCHED); -- cgit v1.2.3-59-g8ed1b From 06e799764eb7c2e4640888d438c3524d756613e1 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Tue, 25 Aug 2009 18:53:37 -0700 Subject: rcu: Remove lockdep annotations from RCU's _notrace() API members The lockdep annotations rcu_read_acquire() and rcu_read_release() might lead to infinite looping if called from lockdep. So this patch removes them. Formal repost of http://lkml.org/lkml/2009/8/25/309 on the strength of Lai Jiangshan's review. Suggested-by: Lai Jiangshan Suggested-by: Mathieu Desnoyers Reviewed-by: Lai Jiangshan Signed-off-by: Paul E. McKenney Cc: dipankar@in.ibm.com Cc: akpm@linux-foundation.org Cc: josht@linux.vnet.ibm.com Cc: dvhltc@us.ibm.com Cc: niv@us.ibm.com Cc: peterz@infradead.org Cc: rostedt@goodmis.org LKML-Reference: <20090826015337.GA18904@linux.vnet.ibm.com> Signed-off-by: Ingo Molnar --- include/linux/rcupdate.h | 2 -- 1 file changed, 2 deletions(-) (limited to 'include') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 8b4422c558da..95e0615f4d75 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -195,7 +195,6 @@ static inline notrace void rcu_read_lock_sched_notrace(void) { preempt_disable_notrace(); __acquire(RCU_SCHED); - rcu_read_acquire(); } /* @@ -211,7 +210,6 @@ static inline void rcu_read_unlock_sched(void) } static inline notrace void rcu_read_unlock_sched_notrace(void) { - rcu_read_release(); __release(RCU_SCHED); preempt_enable_notrace(); } -- cgit v1.2.3-59-g8ed1b From dd5d19bafd90d33043a4a14b2e2d98612caa293c Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Thu, 27 Aug 2009 14:58:16 -0700 Subject: rcu: Create rcutree plugins to handle hotplug CPU for multi-level trees When offlining CPUs from a multi-level tree, there is the possibility of offlining the last CPU from a given node when there are preempted RCU read-side critical sections that started life on one of the CPUs on that node. In this case, the corresponding tasks will be enqueued via the task_struct's rcu_node_entry list_head onto one of the rcu_node's blocked_tasks[] lists. These tasks need to be moved somewhere else so that they will prevent the current grace period from ending. That somewhere is the root rcu_node. Signed-off-by: Paul E. McKenney Cc: laijs@cn.fujitsu.com Cc: dipankar@in.ibm.com Cc: akpm@linux-foundation.org Cc: mathieu.desnoyers@polymtl.ca Cc: josht@linux.vnet.ibm.com Cc: dvhltc@us.ibm.com Cc: niv@us.ibm.com Cc: peterz@infradead.org Cc: rostedt@goodmis.org LKML-Reference: <20090827215816.GA30472@linux.vnet.ibm.com> Signed-off-by: Ingo Molnar --- include/linux/init_task.h | 2 +- include/linux/sched.h | 4 +-- kernel/rcutree.c | 2 ++ kernel/rcutree_plugin.h | 69 +++++++++++++++++++++++++++++++++++++++++++---- 4 files changed, 69 insertions(+), 8 deletions(-) (limited to 'include') diff --git a/include/linux/init_task.h b/include/linux/init_task.h index 79d4baee31b6..9e7f2e8fc66e 100644 --- a/include/linux/init_task.h +++ b/include/linux/init_task.h @@ -98,7 +98,7 @@ extern struct group_info init_groups; #define INIT_TASK_RCU_PREEMPT(tsk) \ .rcu_read_lock_nesting = 0, \ .rcu_read_unlock_special = 0, \ - .rcu_blocked_cpu = -1, \ + .rcu_blocked_node = NULL, \ .rcu_node_entry = LIST_HEAD_INIT(tsk.rcu_node_entry), #else #define INIT_TASK_RCU_PREEMPT(tsk) diff --git a/include/linux/sched.h b/include/linux/sched.h index bfca26d63b13..3fe03151a8e6 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1208,7 +1208,7 @@ struct task_struct { #ifdef CONFIG_TREE_PREEMPT_RCU int rcu_read_lock_nesting; char rcu_read_unlock_special; - int rcu_blocked_cpu; + void *rcu_blocked_node; struct list_head rcu_node_entry; #endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */ @@ -1735,7 +1735,7 @@ static inline void rcu_copy_process(struct task_struct *p) { p->rcu_read_lock_nesting = 0; p->rcu_read_unlock_special = 0; - p->rcu_blocked_cpu = -1; + p->rcu_blocked_node = NULL; INIT_LIST_HEAD(&p->rcu_node_entry); } diff --git a/kernel/rcutree.c b/kernel/rcutree.c index fee6316a8673..d903e2f2b840 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -81,6 +81,7 @@ struct rcu_state rcu_bh_state = RCU_STATE_INITIALIZER(rcu_bh_state); DEFINE_PER_CPU(struct rcu_data, rcu_bh_data); extern long rcu_batches_completed_sched(void); +static struct rcu_node *rcu_get_root(struct rcu_state *rsp); static void cpu_quiet_msk(unsigned long mask, struct rcu_state *rsp, struct rcu_node *rnp, unsigned long flags); static void cpu_quiet_msk_finish(struct rcu_state *rsp, unsigned long flags); @@ -876,6 +877,7 @@ static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp) spin_unlock(&rnp->lock); /* irqs remain disabled. */ break; } + rcu_preempt_offline_tasks(rsp, rnp); mask = rnp->grpmask; spin_unlock(&rnp->lock); /* irqs remain disabled. */ rnp = rnp->parent; diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h index 201334cdc200..04343bee646d 100644 --- a/kernel/rcutree_plugin.h +++ b/kernel/rcutree_plugin.h @@ -92,7 +92,7 @@ static void rcu_preempt_qs(int cpu) rnp = rdp->mynode; spin_lock(&rnp->lock); t->rcu_read_unlock_special |= RCU_READ_UNLOCK_BLOCKED; - t->rcu_blocked_cpu = cpu; + t->rcu_blocked_node = (void *)rnp; /* * If this CPU has already checked in, then this task @@ -170,12 +170,21 @@ static void rcu_read_unlock_special(struct task_struct *t) if (special & RCU_READ_UNLOCK_BLOCKED) { t->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_BLOCKED; - /* Remove this task from the list it blocked on. */ - rnp = rcu_preempt_state.rda[t->rcu_blocked_cpu]->mynode; - spin_lock(&rnp->lock); + /* + * Remove this task from the list it blocked on. The + * task can migrate while we acquire the lock, but at + * most one time. So at most two passes through loop. + */ + for (;;) { + rnp = (struct rcu_node *)t->rcu_blocked_node; + spin_lock(&rnp->lock); + if (rnp == (struct rcu_node *)t->rcu_blocked_node) + break; + spin_unlock(&rnp->lock); + } empty = list_empty(&rnp->blocked_tasks[rnp->gpnum & 0x1]); list_del_init(&t->rcu_node_entry); - t->rcu_blocked_cpu = -1; + t->rcu_blocked_node = NULL; /* * If this was the last task on the current list, and if @@ -261,6 +270,47 @@ static int rcu_preempted_readers(struct rcu_node *rnp) #ifdef CONFIG_HOTPLUG_CPU +/* + * Handle tasklist migration for case in which all CPUs covered by the + * specified rcu_node have gone offline. Move them up to the root + * rcu_node. The reason for not just moving them to the immediate + * parent is to remove the need for rcu_read_unlock_special() to + * make more than two attempts to acquire the target rcu_node's lock. + * + * The caller must hold rnp->lock with irqs disabled. + */ +static void rcu_preempt_offline_tasks(struct rcu_state *rsp, + struct rcu_node *rnp) +{ + int i; + struct list_head *lp; + struct list_head *lp_root; + struct rcu_node *rnp_root = rcu_get_root(rsp); + struct task_struct *tp; + + if (rnp == rnp_root) + return; /* Shouldn't happen: at least one CPU online. */ + + /* + * Move tasks up to root rcu_node. Rely on the fact that the + * root rcu_node can be at most one ahead of the rest of the + * rcu_nodes in terms of gp_num value. This fact allows us to + * move the blocked_tasks[] array directly, element by element. + */ + for (i = 0; i < 2; i++) { + lp = &rnp->blocked_tasks[i]; + lp_root = &rnp_root->blocked_tasks[i]; + while (!list_empty(lp)) { + tp = list_entry(lp->next, typeof(*tp), rcu_node_entry); + spin_lock(&rnp_root->lock); /* irqs already disabled */ + list_del(&tp->rcu_node_entry); + tp->rcu_blocked_node = rnp_root; + list_add(&tp->rcu_node_entry, lp_root); + spin_unlock(&rnp_root->lock); /* irqs remain disabled */ + } + } +} + /* * Do CPU-offline processing for preemptable RCU. */ @@ -409,6 +459,15 @@ static int rcu_preempted_readers(struct rcu_node *rnp) #ifdef CONFIG_HOTPLUG_CPU +/* + * Because preemptable RCU does not exist, it never needs to migrate + * tasks that were blocked within RCU read-side critical sections. + */ +static void rcu_preempt_offline_tasks(struct rcu_state *rsp, + struct rcu_node *rnp) +{ +} + /* * Because preemptable RCU does not exist, it never needs CPU-offline * processing. -- cgit v1.2.3-59-g8ed1b From 868489660dabc0c28087cca3dbc1adbbc398c6fe Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Thu, 27 Aug 2009 15:00:12 -0700 Subject: rcu: Changes from reviews: avoid casts, fix/add warnings, improve comments Changes suggested by review comments from Josh Triplett and Mathieu Desnoyers. Signed-off-by: Paul E. McKenney Acked-by: Josh Triplett Acked-by: Mathieu Desnoyers Cc: laijs@cn.fujitsu.com Cc: dipankar@in.ibm.com Cc: akpm@linux-foundation.org Cc: dvhltc@us.ibm.com Cc: niv@us.ibm.com Cc: peterz@infradead.org Cc: rostedt@goodmis.org LKML-Reference: <20090827220012.GA30525@linux.vnet.ibm.com> Signed-off-by: Ingo Molnar --- include/linux/sched.h | 4 +++- kernel/rcutree.c | 13 ++++++------- kernel/rcutree.h | 2 ++ kernel/rcutree_plugin.h | 10 ++++++---- 4 files changed, 17 insertions(+), 12 deletions(-) (limited to 'include') diff --git a/include/linux/sched.h b/include/linux/sched.h index 3fe03151a8e6..855fd0d3f174 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1163,6 +1163,8 @@ struct sched_rt_entity { #endif }; +struct rcu_node; + struct task_struct { volatile long state; /* -1 unrunnable, 0 runnable, >0 stopped */ void *stack; @@ -1208,7 +1210,7 @@ struct task_struct { #ifdef CONFIG_TREE_PREEMPT_RCU int rcu_read_lock_nesting; char rcu_read_unlock_special; - void *rcu_blocked_node; + struct rcu_node *rcu_blocked_node; struct list_head rcu_node_entry; #endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */ diff --git a/kernel/rcutree.c b/kernel/rcutree.c index d903e2f2b840..71bc79791cd9 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -229,7 +229,6 @@ static int rcu_implicit_offline_qs(struct rcu_data *rdp) #endif /* #ifdef CONFIG_SMP */ #ifdef CONFIG_NO_HZ -static DEFINE_RATELIMIT_STATE(rcu_rs, 10 * HZ, 5); /** * rcu_enter_nohz - inform RCU that current CPU is entering nohz @@ -249,7 +248,7 @@ void rcu_enter_nohz(void) rdtp = &__get_cpu_var(rcu_dynticks); rdtp->dynticks++; rdtp->dynticks_nesting--; - WARN_ON_RATELIMIT(rdtp->dynticks & 0x1, &rcu_rs); + WARN_ON_ONCE(rdtp->dynticks & 0x1); local_irq_restore(flags); } @@ -268,7 +267,7 @@ void rcu_exit_nohz(void) rdtp = &__get_cpu_var(rcu_dynticks); rdtp->dynticks++; rdtp->dynticks_nesting++; - WARN_ON_RATELIMIT(!(rdtp->dynticks & 0x1), &rcu_rs); + WARN_ON_ONCE(!(rdtp->dynticks & 0x1)); local_irq_restore(flags); smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */ } @@ -287,7 +286,7 @@ void rcu_nmi_enter(void) if (rdtp->dynticks & 0x1) return; rdtp->dynticks_nmi++; - WARN_ON_RATELIMIT(!(rdtp->dynticks_nmi & 0x1), &rcu_rs); + WARN_ON_ONCE(!(rdtp->dynticks_nmi & 0x1)); smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */ } @@ -306,7 +305,7 @@ void rcu_nmi_exit(void) return; smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */ rdtp->dynticks_nmi++; - WARN_ON_RATELIMIT(rdtp->dynticks_nmi & 0x1, &rcu_rs); + WARN_ON_ONCE(rdtp->dynticks_nmi & 0x1); } /** @@ -322,7 +321,7 @@ void rcu_irq_enter(void) if (rdtp->dynticks_nesting++) return; rdtp->dynticks++; - WARN_ON_RATELIMIT(!(rdtp->dynticks & 0x1), &rcu_rs); + WARN_ON_ONCE(!(rdtp->dynticks & 0x1)); smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */ } @@ -341,7 +340,7 @@ void rcu_irq_exit(void) return; smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */ rdtp->dynticks++; - WARN_ON_RATELIMIT(rdtp->dynticks & 0x1, &rcu_rs); + WARN_ON_ONCE(rdtp->dynticks & 0x1); /* If the interrupt queued a callback, get out of dyntick mode. */ if (__get_cpu_var(rcu_sched_data).nxtlist || diff --git a/kernel/rcutree.h b/kernel/rcutree.h index ca560364d8cd..bf8a6f9f134d 100644 --- a/kernel/rcutree.h +++ b/kernel/rcutree.h @@ -81,6 +81,8 @@ struct rcu_dynticks { struct rcu_node { spinlock_t lock; long gpnum; /* Current grace period for this node. */ + /* This will either be equal to or one */ + /* behind the root rcu_node's gpnum. */ unsigned long qsmask; /* CPUs or groups that need to switch in */ /* order for current grace period to proceed.*/ unsigned long qsmaskinit; diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h index 04343bee646d..47789369ea59 100644 --- a/kernel/rcutree_plugin.h +++ b/kernel/rcutree_plugin.h @@ -92,7 +92,7 @@ static void rcu_preempt_qs(int cpu) rnp = rdp->mynode; spin_lock(&rnp->lock); t->rcu_read_unlock_special |= RCU_READ_UNLOCK_BLOCKED; - t->rcu_blocked_node = (void *)rnp; + t->rcu_blocked_node = rnp; /* * If this CPU has already checked in, then this task @@ -176,9 +176,9 @@ static void rcu_read_unlock_special(struct task_struct *t) * most one time. So at most two passes through loop. */ for (;;) { - rnp = (struct rcu_node *)t->rcu_blocked_node; + rnp = t->rcu_blocked_node; spin_lock(&rnp->lock); - if (rnp == (struct rcu_node *)t->rcu_blocked_node) + if (rnp == t->rcu_blocked_node) break; spin_unlock(&rnp->lock); } @@ -288,8 +288,10 @@ static void rcu_preempt_offline_tasks(struct rcu_state *rsp, struct rcu_node *rnp_root = rcu_get_root(rsp); struct task_struct *tp; - if (rnp == rnp_root) + if (rnp == rnp_root) { + WARN_ONCE(1, "Last CPU thought to be offlined?"); return; /* Shouldn't happen: at least one CPU online. */ + } /* * Move tasks up to root rcu_node. Rely on the fact that the -- cgit v1.2.3-59-g8ed1b