From 2b3fc35f6919344e3cf722dde8308f47235c0b70 Mon Sep 17 00:00:00 2001 From: Lai Jiangshan Date: Tue, 20 Apr 2010 16:23:07 +0800 Subject: rcu: optionally leave lockdep enabled after RCU lockdep splat There is no need to disable lockdep after an RCU lockdep splat, so remove the debug_lockdeps_off() from lockdep_rcu_dereference(). To avoid repeated lockdep splats, use a static variable in the inlined rcu_dereference_check() and rcu_dereference_protected() macros so that a given instance splats only once, but so that multiple instances can be detected per boot. This is controlled by a new config variable CONFIG_PROVE_RCU_REPEATEDLY, which is disabled by default. This provides the normal lockdep behavior by default, but permits people who want to find multiple RCU-lockdep splats per boot to easily do so. Requested-by: Eric Paris Signed-off-by: Lai Jiangshan Tested-by: Eric Paris Signed-off-by: Paul E. McKenney --- include/linux/rcupdate.h | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-) (limited to 'include') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index db266bbed23f..4dca2752cfde 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -192,6 +192,15 @@ static inline int rcu_read_lock_sched_held(void) extern int rcu_my_thread_group_empty(void); +#define __do_rcu_dereference_check(c) \ + do { \ + static bool __warned; \ + if (debug_lockdep_rcu_enabled() && !__warned && !(c)) { \ + __warned = true; \ + lockdep_rcu_dereference(__FILE__, __LINE__); \ + } \ + } while (0) + /** * rcu_dereference_check - rcu_dereference with debug checking * @p: The pointer to read, prior to dereferencing @@ -221,8 +230,7 @@ extern int rcu_my_thread_group_empty(void); */ #define rcu_dereference_check(p, c) \ ({ \ - if (debug_lockdep_rcu_enabled() && !(c)) \ - lockdep_rcu_dereference(__FILE__, __LINE__); \ + __do_rcu_dereference_check(c); \ rcu_dereference_raw(p); \ }) @@ -239,8 +247,7 @@ extern int rcu_my_thread_group_empty(void); */ #define rcu_dereference_protected(p, c) \ ({ \ - if (debug_lockdep_rcu_enabled() && !(c)) \ - lockdep_rcu_dereference(__FILE__, __LINE__); \ + __do_rcu_dereference_check(c); \ (p); \ }) -- cgit v1.2.3 From d20200b591f59847ab6a5c23507084a7d29e23c5 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Tue, 30 Mar 2010 10:52:21 -0700 Subject: rcu: Fix bogus CONFIG_PROVE_LOCKING in comments to reflect reality. It is CONFIG_DEBUG_LOCK_ALLOC rather than CONFIG_PROVE_LOCKING, so fix it. Signed-off-by: Paul E. McKenney --- include/linux/rcupdate.h | 15 ++++++++------- include/linux/srcu.h | 4 ++-- 2 files changed, 10 insertions(+), 9 deletions(-) (limited to 'include') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 4dca2752cfde..a150af0e5cd5 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -106,8 +106,8 @@ extern int debug_lockdep_rcu_enabled(void); /** * rcu_read_lock_held - might we be in RCU read-side critical section? * - * If CONFIG_PROVE_LOCKING is selected and enabled, returns nonzero iff in - * an RCU read-side critical section. In absence of CONFIG_PROVE_LOCKING, + * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an RCU + * read-side critical section. In absence of CONFIG_DEBUG_LOCK_ALLOC, * this assumes we are in an RCU read-side critical section unless it can * prove otherwise. * @@ -129,11 +129,12 @@ extern int rcu_read_lock_bh_held(void); /** * rcu_read_lock_sched_held - might we be in RCU-sched read-side critical section? * - * If CONFIG_PROVE_LOCKING is selected and enabled, returns nonzero iff in an - * RCU-sched read-side critical section. In absence of CONFIG_PROVE_LOCKING, - * this assumes we are in an RCU-sched read-side critical section unless it - * can prove otherwise. Note that disabling of preemption (including - * disabling irqs) counts as an RCU-sched read-side critical section. + * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an + * RCU-sched read-side critical section. In absence of + * CONFIG_DEBUG_LOCK_ALLOC, this assumes we are in an RCU-sched read-side + * critical section unless it can prove otherwise. Note that disabling + * of preemption (including disabling irqs) counts as an RCU-sched + * read-side critical section. * * Check rcu_scheduler_active to prevent false positives during boot. */ diff --git a/include/linux/srcu.h b/include/linux/srcu.h index 4d5ecb222af9..9c01f1022428 100644 --- a/include/linux/srcu.h +++ b/include/linux/srcu.h @@ -84,8 +84,8 @@ long srcu_batches_completed(struct srcu_struct *sp); /** * srcu_read_lock_held - might we be in SRCU read-side critical section? * - * If CONFIG_PROVE_LOCKING is selected and enabled, returns nonzero iff in - * an SRCU read-side critical section. In absence of CONFIG_PROVE_LOCKING, + * If CONFIG_DEBUG_LOCK_ALLOC is selected, returns nonzero iff in an SRCU + * read-side critical section. In absence of CONFIG_DEBUG_LOCK_ALLOC, * this assumes we are in an SRCU read-side critical section unless it can * prove otherwise. */ -- cgit v1.2.3 From 32c141a0a1dfa29e0a07d78bec0c0919fc4b9f88 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Tue, 30 Mar 2010 10:59:28 -0700 Subject: rcu: fix now-bogus rcu_scheduler_active comments. The rcu_scheduler_active check has been wrapped into the new debug_lockdep_rcu_enabled() function, so update the comments to reflect this new reality. Signed-off-by: Paul E. McKenney --- include/linux/rcupdate.h | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) (limited to 'include') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index a150af0e5cd5..02537a72aaa4 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -111,7 +111,8 @@ extern int debug_lockdep_rcu_enabled(void); * this assumes we are in an RCU read-side critical section unless it can * prove otherwise. * - * Check rcu_scheduler_active to prevent false positives during boot. + * Check debug_lockdep_rcu_enabled() to prevent false positives during boot + * and while lockdep is disabled. */ static inline int rcu_read_lock_held(void) { @@ -136,7 +137,8 @@ extern int rcu_read_lock_bh_held(void); * of preemption (including disabling irqs) counts as an RCU-sched * read-side critical section. * - * Check rcu_scheduler_active to prevent false positives during boot. + * Check debug_lockdep_rcu_enabled() to prevent false positives during boot + * and while lockdep is disabled. */ #ifdef CONFIG_PREEMPT static inline int rcu_read_lock_sched_held(void) -- cgit v1.2.3 From da848c47bc6e873a54a445ea1960423a495b6b32 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Tue, 30 Mar 2010 15:46:01 -0700 Subject: rcu: shrink rcutiny by making synchronize_rcu_bh() be inline Because synchronize_rcu_bh() is identical to synchronize_sched(), make the former a static inline invoking the latter, saving the overhead of an EXPORT_SYMBOL_GPL() and the duplicate code. Signed-off-by: Paul E. McKenney --- include/linux/rcupdate.h | 2 -- include/linux/rcutiny.h | 12 +++++++++++- include/linux/rcutree.h | 2 ++ kernel/rcutiny.c | 9 ++------- 4 files changed, 15 insertions(+), 10 deletions(-) (limited to 'include') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 02537a72aaa4..d8fb2abcf303 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -56,8 +56,6 @@ struct rcu_head { }; /* Exported common interfaces */ -extern void synchronize_rcu_bh(void); -extern void synchronize_sched(void); extern void rcu_barrier(void); extern void rcu_barrier_bh(void); extern void rcu_barrier_sched(void); diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h index a5195875480a..bbeb55b7709b 100644 --- a/include/linux/rcutiny.h +++ b/include/linux/rcutiny.h @@ -74,7 +74,17 @@ static inline void rcu_sched_force_quiescent_state(void) { } -#define synchronize_rcu synchronize_sched +extern void synchronize_sched(void); + +static inline void synchronize_rcu(void) +{ + synchronize_sched(); +} + +static inline void synchronize_rcu_bh(void) +{ + synchronize_sched(); +} static inline void synchronize_rcu_expedited(void) { diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h index 42cc3a04779e..7484fe66a3aa 100644 --- a/include/linux/rcutree.h +++ b/include/linux/rcutree.h @@ -86,6 +86,8 @@ static inline void __rcu_read_unlock_bh(void) extern void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *rcu)); +extern void synchronize_rcu_bh(void); +extern void synchronize_sched(void); extern void synchronize_rcu_expedited(void); static inline void synchronize_rcu_bh_expedited(void) diff --git a/kernel/rcutiny.c b/kernel/rcutiny.c index 9f6d9ff2572c..272c6d21a75f 100644 --- a/kernel/rcutiny.c +++ b/kernel/rcutiny.c @@ -187,7 +187,8 @@ static void rcu_process_callbacks(struct softirq_action *unused) * * Cool, huh? (Due to Josh Triplett.) * - * But we want to make this a static inline later. + * But we want to make this a static inline later. The cond_resched() + * currently makes this problematic. */ void synchronize_sched(void) { @@ -195,12 +196,6 @@ void synchronize_sched(void) } EXPORT_SYMBOL_GPL(synchronize_sched); -void synchronize_rcu_bh(void) -{ - synchronize_sched(); -} -EXPORT_SYMBOL_GPL(synchronize_rcu_bh); - /* * Helper function for call_rcu() and call_rcu_bh(). */ -- cgit v1.2.3 From 25502a6c13745f4650cc59322bd198194f55e796 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Thu, 1 Apr 2010 17:37:01 -0700 Subject: rcu: refactor RCU's context-switch handling The addition of preemptible RCU to treercu resulted in a bit of confusion and inefficiency surrounding the handling of context switches for RCU-sched and for RCU-preempt. For RCU-sched, a context switch is a quiescent state, pure and simple, just like it always has been. For RCU-preempt, a context switch is in no way a quiescent state, but special handling is required when a task blocks in an RCU read-side critical section. However, the callout from the scheduler and the outer loop in ksoftirqd still calls something named rcu_sched_qs(), whose name is no longer accurate. Furthermore, when rcu_check_callbacks() notes an RCU-sched quiescent state, it ends up unnecessarily (though harmlessly, aside from the performance hit) enqueuing the current task if it happens to be running in an RCU-preempt read-side critical section. This not only increases the maximum latency of scheduler_tick(), it also needlessly increases the overhead of the next outermost rcu_read_unlock() invocation. This patch addresses this situation by separating the notion of RCU's context-switch handling from that of RCU-sched's quiescent states. The context-switch handling is covered by rcu_note_context_switch() in general and by rcu_preempt_note_context_switch() for preemptible RCU. This permits rcu_sched_qs() to handle quiescent states and only quiescent states. It also reduces the maximum latency of scheduler_tick(), though probably by much less than a microsecond. Finally, it means that tasks within preemptible-RCU read-side critical sections avoid incurring the overhead of queuing unless there really is a context switch. Suggested-by: Lai Jiangshan Acked-by: Lai Jiangshan Signed-off-by: Paul E. McKenney Cc: Ingo Molnar Cc: Peter Zijlstra --- include/linux/rcutiny.h | 4 ++++ include/linux/rcutree.h | 1 + kernel/rcutree.c | 17 ++++++++++++----- kernel/rcutree_plugin.h | 11 +++++++---- kernel/sched.c | 2 +- kernel/softirq.c | 2 +- 6 files changed, 26 insertions(+), 11 deletions(-) (limited to 'include') diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h index bbeb55b7709b..ff22b97fb979 100644 --- a/include/linux/rcutiny.h +++ b/include/linux/rcutiny.h @@ -29,6 +29,10 @@ void rcu_sched_qs(int cpu); void rcu_bh_qs(int cpu); +static inline void rcu_note_context_switch(int cpu) +{ + rcu_sched_qs(cpu); +} #define __rcu_read_lock() preempt_disable() #define __rcu_read_unlock() preempt_enable() diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h index 7484fe66a3aa..b9f74606f320 100644 --- a/include/linux/rcutree.h +++ b/include/linux/rcutree.h @@ -34,6 +34,7 @@ struct notifier_block; extern void rcu_sched_qs(int cpu); extern void rcu_bh_qs(int cpu); +extern void rcu_note_context_switch(int cpu); extern int rcu_needs_cpu(int cpu); extern int rcu_expedited_torture_stats(char *page); diff --git a/kernel/rcutree.c b/kernel/rcutree.c index 86bb9499aae6..e33631354b69 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -97,25 +97,32 @@ static int rcu_gp_in_progress(struct rcu_state *rsp) */ void rcu_sched_qs(int cpu) { - struct rcu_data *rdp; + struct rcu_data *rdp = &per_cpu(rcu_sched_data, cpu); - rdp = &per_cpu(rcu_sched_data, cpu); rdp->passed_quiesc_completed = rdp->gpnum - 1; barrier(); rdp->passed_quiesc = 1; - rcu_preempt_note_context_switch(cpu); } void rcu_bh_qs(int cpu) { - struct rcu_data *rdp; + struct rcu_data *rdp = &per_cpu(rcu_bh_data, cpu); - rdp = &per_cpu(rcu_bh_data, cpu); rdp->passed_quiesc_completed = rdp->gpnum - 1; barrier(); rdp->passed_quiesc = 1; } +/* + * Note a context switch. This is a quiescent state for RCU-sched, + * and requires special handling for preemptible RCU. + */ +void rcu_note_context_switch(int cpu) +{ + rcu_sched_qs(cpu); + rcu_preempt_note_context_switch(cpu); +} + #ifdef CONFIG_NO_HZ DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = { .dynticks_nesting = 1, diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h index 687c4e90722e..f9bc83a047da 100644 --- a/kernel/rcutree_plugin.h +++ b/kernel/rcutree_plugin.h @@ -75,13 +75,19 @@ EXPORT_SYMBOL_GPL(rcu_force_quiescent_state); * 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. + * + * Unlike the other rcu_*_qs() functions, callers to this function + * must disable irqs in order to protect the assignment to + * ->rcu_read_unlock_special. */ static void rcu_preempt_qs(int cpu) { struct rcu_data *rdp = &per_cpu(rcu_preempt_data, cpu); + rdp->passed_quiesc_completed = rdp->gpnum - 1; barrier(); rdp->passed_quiesc = 1; + current->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_NEED_QS; } /* @@ -144,9 +150,8 @@ static void rcu_preempt_note_context_switch(int cpu) * grace period, then the fact that the task has been enqueued * means that we continue to block the current grace period. */ - rcu_preempt_qs(cpu); local_irq_save(flags); - t->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_NEED_QS; + rcu_preempt_qs(cpu); local_irq_restore(flags); } @@ -236,7 +241,6 @@ static void rcu_read_unlock_special(struct task_struct *t) */ special = t->rcu_read_unlock_special; if (special & RCU_READ_UNLOCK_NEED_QS) { - t->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_NEED_QS; rcu_preempt_qs(smp_processor_id()); } @@ -473,7 +477,6 @@ 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_preempt_qs(cpu); return; } diff --git a/kernel/sched.c b/kernel/sched.c index 3c2a54f70ffe..d8a213ccdc3b 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -3706,7 +3706,7 @@ need_resched: preempt_disable(); cpu = smp_processor_id(); rq = cpu_rq(cpu); - rcu_sched_qs(cpu); + rcu_note_context_switch(cpu); prev = rq->curr; switch_count = &prev->nivcsw; diff --git a/kernel/softirq.c b/kernel/softirq.c index 7c1a67ef0274..0db913a5c60f 100644 --- a/kernel/softirq.c +++ b/kernel/softirq.c @@ -716,7 +716,7 @@ static int run_ksoftirqd(void * __bind_cpu) preempt_enable_no_resched(); cond_resched(); preempt_disable(); - rcu_sched_qs((long)__bind_cpu); + rcu_note_context_switch((long)__bind_cpu); } preempt_enable(); set_current_state(TASK_INTERRUPTIBLE); -- cgit v1.2.3 From bbad937983147c017c25406860287cb94da9af7c Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Fri, 2 Apr 2010 16:17:17 -0700 Subject: rcu: slim down rcutiny by removing rcu_scheduler_active and friends TINY_RCU does not need rcu_scheduler_active unless CONFIG_DEBUG_LOCK_ALLOC. So conditionally compile rcu_scheduler_active in order to slim down rcutiny a bit more. Also gets rid of an EXPORT_SYMBOL_GPL, which is responsible for most of the slimming. Signed-off-by: Paul E. McKenney --- include/linux/rcupdate.h | 4 +--- include/linux/rcutiny.h | 13 +++++++++++++ include/linux/rcutree.h | 3 +++ kernel/rcupdate.c | 19 ------------------- kernel/rcutiny.c | 7 +++++++ kernel/rcutiny_plugin.h | 39 +++++++++++++++++++++++++++++++++++++++ kernel/rcutree.c | 19 +++++++++++++++++++ 7 files changed, 82 insertions(+), 22 deletions(-) create mode 100644 kernel/rcutiny_plugin.h (limited to 'include') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index d8fb2abcf303..23be3a702516 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -64,8 +64,6 @@ extern int sched_expedited_torture_stats(char *page); /* Internal to kernel */ extern void rcu_init(void); -extern int rcu_scheduler_active; -extern void rcu_scheduler_starting(void); #if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU) #include @@ -178,7 +176,7 @@ static inline int rcu_read_lock_bh_held(void) #ifdef CONFIG_PREEMPT static inline int rcu_read_lock_sched_held(void) { - return !rcu_scheduler_active || preempt_count() != 0 || irqs_disabled(); + return preempt_count() != 0 || irqs_disabled(); } #else /* #ifdef CONFIG_PREEMPT */ static inline int rcu_read_lock_sched_held(void) diff --git a/include/linux/rcutiny.h b/include/linux/rcutiny.h index ff22b97fb979..14e5a76b2c06 100644 --- a/include/linux/rcutiny.h +++ b/include/linux/rcutiny.h @@ -128,4 +128,17 @@ static inline int rcu_preempt_depth(void) return 0; } +#ifdef CONFIG_DEBUG_LOCK_ALLOC + +extern int rcu_scheduler_active __read_mostly; +extern void rcu_scheduler_starting(void); + +#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ + +static inline void rcu_scheduler_starting(void) +{ +} + +#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ + #endif /* __LINUX_RCUTINY_H */ diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h index b9f74606f320..48282055e83d 100644 --- a/include/linux/rcutree.h +++ b/include/linux/rcutree.h @@ -123,4 +123,7 @@ static inline int rcu_blocking_is_gp(void) return num_online_cpus() == 1; } +extern void rcu_scheduler_starting(void); +extern int rcu_scheduler_active __read_mostly; + #endif /* __LINUX_RCUTREE_H */ diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c index 49d808e833b0..72a8dc9567f5 100644 --- a/kernel/rcupdate.c +++ b/kernel/rcupdate.c @@ -44,7 +44,6 @@ #include #include #include -#include #include #ifdef CONFIG_DEBUG_LOCK_ALLOC @@ -64,9 +63,6 @@ struct lockdep_map rcu_sched_lock_map = EXPORT_SYMBOL_GPL(rcu_sched_lock_map); #endif -int rcu_scheduler_active __read_mostly; -EXPORT_SYMBOL_GPL(rcu_scheduler_active); - #ifdef CONFIG_DEBUG_LOCK_ALLOC int debug_lockdep_rcu_enabled(void) @@ -96,21 +92,6 @@ EXPORT_SYMBOL_GPL(rcu_read_lock_bh_held); #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ -/* - * This function is invoked towards the end of the scheduler's initialization - * process. Before this is called, the idle task might contain - * RCU read-side critical sections (during which time, this idle - * task is booting the system). After this function is called, the - * idle tasks are prohibited from containing RCU read-side critical - * sections. - */ -void rcu_scheduler_starting(void) -{ - WARN_ON(num_online_cpus() != 1); - WARN_ON(nr_context_switches() > 0); - rcu_scheduler_active = 1; -} - /* * Awaken the corresponding synchronize_rcu() instance now that a * grace period has elapsed. diff --git a/kernel/rcutiny.c b/kernel/rcutiny.c index d9f8a623c9fa..b1804ff83d5e 100644 --- a/kernel/rcutiny.c +++ b/kernel/rcutiny.c @@ -54,6 +54,11 @@ static struct rcu_ctrlblk rcu_bh_ctrlblk = { .curtail = &rcu_bh_ctrlblk.rcucblist, }; +#ifdef CONFIG_DEBUG_LOCK_ALLOC +int rcu_scheduler_active __read_mostly; +EXPORT_SYMBOL_GPL(rcu_scheduler_active); +#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ + #ifdef CONFIG_NO_HZ static long rcu_dynticks_nesting = 1; @@ -276,3 +281,5 @@ void __init rcu_init(void) { open_softirq(RCU_SOFTIRQ, rcu_process_callbacks); } + +#include "rcutiny_plugin.h" diff --git a/kernel/rcutiny_plugin.h b/kernel/rcutiny_plugin.h new file mode 100644 index 000000000000..d223a92bc742 --- /dev/null +++ b/kernel/rcutiny_plugin.h @@ -0,0 +1,39 @@ +/* + * 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 IBM Corporation, 2009 + * + * Author: Paul E. McKenney + */ + +#ifdef CONFIG_DEBUG_LOCK_ALLOC + +#include + +/* + * During boot, we forgive RCU lockdep issues. After this function is + * invoked, we start taking RCU lockdep issues seriously. + */ +void rcu_scheduler_starting(void) +{ + WARN_ON(nr_context_switches() > 0); + rcu_scheduler_active = 1; +} + +#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ diff --git a/kernel/rcutree.c b/kernel/rcutree.c index e33631354b69..3623f8e10220 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -46,6 +46,7 @@ #include #include #include +#include #include "rcutree.h" @@ -80,6 +81,9 @@ 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); +int rcu_scheduler_active __read_mostly; +EXPORT_SYMBOL_GPL(rcu_scheduler_active); + /* * Return true if an RCU grace period is in progress. The ACCESS_ONCE()s * permit this function to be invoked without holding the root rcu_node @@ -1783,6 +1787,21 @@ static int __cpuinit rcu_cpu_notify(struct notifier_block *self, return NOTIFY_OK; } +/* + * This function is invoked towards the end of the scheduler's initialization + * process. Before this is called, the idle task might contain + * RCU read-side critical sections (during which time, this idle + * task is booting the system). After this function is called, the + * idle tasks are prohibited from containing RCU read-side critical + * sections. This function also enables RCU lockdep checking. + */ +void rcu_scheduler_starting(void) +{ + WARN_ON(num_online_cpus() != 1); + WARN_ON(nr_context_switches() > 0); + rcu_scheduler_active = 1; +} + /* * Compute the per-level fanout, either using the exact fanout specified * or balancing the tree, depending on CONFIG_RCU_FANOUT_EXACT. -- cgit v1.2.3 From d14aada8e20bdf81ffd43f433b123972cf575b32 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Mon, 19 Apr 2010 22:24:22 -0700 Subject: rcu: make SRCU usable in modules Add a #include for mutex.h to allow SRCU to be more easily used in kernel modules. Signed-off-by: Lai Jiangshan Signed-off-by: Paul E. McKenney --- include/linux/srcu.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include') diff --git a/include/linux/srcu.h b/include/linux/srcu.h index 9c01f1022428..4d5d2f546dbf 100644 --- a/include/linux/srcu.h +++ b/include/linux/srcu.h @@ -27,6 +27,8 @@ #ifndef _LINUX_SRCU_H #define _LINUX_SRCU_H +#include + struct srcu_struct_array { int c[2]; }; -- cgit v1.2.3 From a5d8e467f83f6672104f276223a88e3b50cbd375 Mon Sep 17 00:00:00 2001 From: Mathieu Desnoyers Date: Sat, 17 Apr 2010 08:48:38 -0400 Subject: Debugobjects transition check Implement a basic state machine checker in the debugobjects. This state machine checker detects races and inconsistencies within the "active" life of a debugobject. The checker only keeps track of the current state; all the state machine logic is kept at the object instance level. The checker works by adding a supplementary "unsigned int astate" field to the debug_obj structure. It keeps track of the current "active state" of the object. The only constraints that are imposed on the states by the debugobjects system is that: - activation of an object sets the current active state to 0, - deactivation of an object expects the current active state to be 0. For the rest of the states, the state mapping is determined by the specific object instance. Therefore, the logic keeping track of the state machine is within the specialized instance, without any need to know about it at the debugobject level. The current object active state is changed by calling: debug_object_active_state(addr, descr, expect, next) where "expect" is the expected state and "next" is the next state to move to if the expected state is found. A warning is generated if the expected is not found. Signed-off-by: Mathieu Desnoyers Reviewed-by: Thomas Gleixner Acked-by: David S. Miller CC: "Paul E. McKenney" CC: akpm@linux-foundation.org CC: mingo@elte.hu CC: laijs@cn.fujitsu.com CC: dipankar@in.ibm.com CC: josh@joshtriplett.org CC: dvhltc@us.ibm.com CC: niv@us.ibm.com CC: peterz@infradead.org CC: rostedt@goodmis.org CC: Valdis.Kletnieks@vt.edu CC: dhowells@redhat.com CC: eric.dumazet@gmail.com CC: Alexey Dobriyan Signed-off-by: Paul E. McKenney --- include/linux/debugobjects.h | 11 +++++++++ lib/debugobjects.c | 59 +++++++++++++++++++++++++++++++++++++++++--- 2 files changed, 67 insertions(+), 3 deletions(-) (limited to 'include') diff --git a/include/linux/debugobjects.h b/include/linux/debugobjects.h index 8c243aaa86a7..597692f1fc8d 100644 --- a/include/linux/debugobjects.h +++ b/include/linux/debugobjects.h @@ -20,12 +20,14 @@ struct debug_obj_descr; * struct debug_obj - representaion of an tracked object * @node: hlist node to link the object into the tracker list * @state: tracked object state + * @astate: current active state * @object: pointer to the real object * @descr: pointer to an object type specific debug description structure */ struct debug_obj { struct hlist_node node; enum debug_obj_state state; + unsigned int astate; void *object; struct debug_obj_descr *descr; }; @@ -60,6 +62,15 @@ extern void debug_object_deactivate(void *addr, struct debug_obj_descr *descr); extern void debug_object_destroy (void *addr, struct debug_obj_descr *descr); extern void debug_object_free (void *addr, struct debug_obj_descr *descr); +/* + * Active state: + * - Set at 0 upon initialization. + * - Must return to 0 before deactivation. + */ +extern void +debug_object_active_state(void *addr, struct debug_obj_descr *descr, + unsigned int expect, unsigned int next); + extern void debug_objects_early_init(void); extern void debug_objects_mem_init(void); #else diff --git a/lib/debugobjects.c b/lib/debugobjects.c index b862b30369ff..076464fd2072 100644 --- a/lib/debugobjects.c +++ b/lib/debugobjects.c @@ -141,6 +141,7 @@ alloc_object(void *addr, struct debug_bucket *b, struct debug_obj_descr *descr) obj->object = addr; obj->descr = descr; obj->state = ODEBUG_STATE_NONE; + obj->astate = 0; hlist_del(&obj->node); hlist_add_head(&obj->node, &b->list); @@ -252,8 +253,10 @@ static void debug_print_object(struct debug_obj *obj, char *msg) if (limit < 5 && obj->descr != descr_test) { limit++; - WARN(1, KERN_ERR "ODEBUG: %s %s object type: %s\n", msg, - obj_states[obj->state], obj->descr->name); + WARN(1, KERN_ERR "ODEBUG: %s %s (active state %u) " + "object type: %s\n", + msg, obj_states[obj->state], obj->astate, + obj->descr->name); } debug_objects_warnings++; } @@ -447,7 +450,10 @@ void debug_object_deactivate(void *addr, struct debug_obj_descr *descr) case ODEBUG_STATE_INIT: case ODEBUG_STATE_INACTIVE: case ODEBUG_STATE_ACTIVE: - obj->state = ODEBUG_STATE_INACTIVE; + if (!obj->astate) + obj->state = ODEBUG_STATE_INACTIVE; + else + debug_print_object(obj, "deactivate"); break; case ODEBUG_STATE_DESTROYED: @@ -553,6 +559,53 @@ out_unlock: raw_spin_unlock_irqrestore(&db->lock, flags); } +/** + * debug_object_active_state - debug checks object usage state machine + * @addr: address of the object + * @descr: pointer to an object specific debug description structure + * @expect: expected state + * @next: state to move to if expected state is found + */ +void +debug_object_active_state(void *addr, struct debug_obj_descr *descr, + unsigned int expect, unsigned int next) +{ + struct debug_bucket *db; + struct debug_obj *obj; + unsigned long flags; + + if (!debug_objects_enabled) + return; + + db = get_bucket((unsigned long) addr); + + raw_spin_lock_irqsave(&db->lock, flags); + + obj = lookup_object(addr, db); + if (obj) { + switch (obj->state) { + case ODEBUG_STATE_ACTIVE: + if (obj->astate == expect) + obj->astate = next; + else + debug_print_object(obj, "active_state"); + break; + + default: + debug_print_object(obj, "active_state"); + break; + } + } else { + struct debug_obj o = { .object = addr, + .state = ODEBUG_STATE_NOTAVAILABLE, + .descr = descr }; + + debug_print_object(&o, "active_state"); + } + + raw_spin_unlock_irqrestore(&db->lock, flags); +} + #ifdef CONFIG_DEBUG_OBJECTS_FREE static void __debug_check_no_obj_freed(const void *address, unsigned long size) { -- cgit v1.2.3 From 4376030a54860dedab9d848dfa7cc700a6025c0b Mon Sep 17 00:00:00 2001 From: Mathieu Desnoyers Date: Sat, 17 Apr 2010 08:48:39 -0400 Subject: rcu head introduce rcu head init on stack PEM: o Would it be possible to make this bisectable as follows? a. Insert a new patch after current patch 4/6 that defines destroy_rcu_head_on_stack(), init_rcu_head_on_stack(), and init_rcu_head() with their !CONFIG_DEBUG_OBJECTS_RCU_HEAD definitions. This patch performs this transition. Signed-off-by: Mathieu Desnoyers CC: "Paul E. McKenney" CC: David S. Miller CC: akpm@linux-foundation.org CC: mingo@elte.hu CC: laijs@cn.fujitsu.com CC: dipankar@in.ibm.com CC: josh@joshtriplett.org CC: dvhltc@us.ibm.com CC: niv@us.ibm.com CC: tglx@linutronix.de CC: peterz@infradead.org CC: rostedt@goodmis.org CC: Valdis.Kletnieks@vt.edu CC: dhowells@redhat.com CC: eric.dumazet@gmail.com CC: Alexey Dobriyan Signed-off-by: Paul E. McKenney --- include/linux/rcupdate.h | 8 ++++++++ 1 file changed, 8 insertions(+) (limited to 'include') diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 23be3a702516..b653b4aaa8a6 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -79,6 +79,14 @@ extern void rcu_init(void); (ptr)->next = NULL; (ptr)->func = NULL; \ } while (0) +static inline void init_rcu_head_on_stack(struct rcu_head *head) +{ +} + +static inline void destroy_rcu_head_on_stack(struct rcu_head *head) +{ +} + #ifdef CONFIG_DEBUG_LOCK_ALLOC extern struct lockdep_map rcu_lock_map; -- cgit v1.2.3 From 72d5a9f7a9542f88397558c65bcfc3b115a65e34 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Mon, 10 May 2010 17:12:17 -0700 Subject: rcu: remove all rcu head initializations, except on_stack initializations Remove all rcu head inits. We don't care about the RCU head state before passing it to call_rcu() anyway. Only leave the "on_stack" variants so debugobjects can keep track of objects on stack. Signed-off-by: Mathieu Desnoyers Signed-off-by: Paul E. McKenney --- include/linux/init_task.h | 1 - kernel/rcutiny.c | 6 ++++++ kernel/rcutorture.c | 2 ++ kernel/rcutree.c | 4 ++++ kernel/rcutree_plugin.h | 2 ++ 5 files changed, 14 insertions(+), 1 deletion(-) (limited to 'include') diff --git a/include/linux/init_task.h b/include/linux/init_task.h index b1ed1cd8e2a8..7996fc2c9ba9 100644 --- a/include/linux/init_task.h +++ b/include/linux/init_task.h @@ -49,7 +49,6 @@ extern struct group_info init_groups; { .first = &init_task.pids[PIDTYPE_PGID].node }, \ { .first = &init_task.pids[PIDTYPE_SID].node }, \ }, \ - .rcu = RCU_HEAD_INIT, \ .level = 0, \ .numbers = { { \ .nr = 0, \ diff --git a/kernel/rcutiny.c b/kernel/rcutiny.c index b1804ff83d5e..38729d3cd236 100644 --- a/kernel/rcutiny.c +++ b/kernel/rcutiny.c @@ -245,11 +245,13 @@ void rcu_barrier(void) { struct rcu_synchronize rcu; + init_rcu_head_on_stack(&rcu.head); init_completion(&rcu.completion); /* Will wake me after RCU finished. */ call_rcu(&rcu.head, wakeme_after_rcu); /* Wait for it. */ wait_for_completion(&rcu.completion); + destroy_rcu_head_on_stack(&rcu.head); } EXPORT_SYMBOL_GPL(rcu_barrier); @@ -257,11 +259,13 @@ void rcu_barrier_bh(void) { struct rcu_synchronize rcu; + init_rcu_head_on_stack(&rcu.head); 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); + destroy_rcu_head_on_stack(&rcu.head); } EXPORT_SYMBOL_GPL(rcu_barrier_bh); @@ -269,11 +273,13 @@ void rcu_barrier_sched(void) { struct rcu_synchronize rcu; + init_rcu_head_on_stack(&rcu.head); 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); + destroy_rcu_head_on_stack(&rcu.head); } EXPORT_SYMBOL_GPL(rcu_barrier_sched); diff --git a/kernel/rcutorture.c b/kernel/rcutorture.c index 58df55bf83ed..077defb34571 100644 --- a/kernel/rcutorture.c +++ b/kernel/rcutorture.c @@ -464,9 +464,11 @@ static void rcu_bh_torture_synchronize(void) { struct rcu_bh_torture_synchronize rcu; + init_rcu_head_on_stack(&rcu.head); init_completion(&rcu.completion); call_rcu_bh(&rcu.head, rcu_bh_torture_wakeme_after_cb); wait_for_completion(&rcu.completion); + destroy_rcu_head_on_stack(&rcu.head); } static struct rcu_torture_ops rcu_bh_ops = { diff --git a/kernel/rcutree.c b/kernel/rcutree.c index ba6996943e28..d4437345706f 100644 --- a/kernel/rcutree.c +++ b/kernel/rcutree.c @@ -1484,11 +1484,13 @@ void synchronize_sched(void) if (rcu_blocking_is_gp()) return; + init_rcu_head_on_stack(&rcu.head); 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); + destroy_rcu_head_on_stack(&rcu.head); } EXPORT_SYMBOL_GPL(synchronize_sched); @@ -1508,11 +1510,13 @@ void synchronize_rcu_bh(void) if (rcu_blocking_is_gp()) return; + init_rcu_head_on_stack(&rcu.head); 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); + destroy_rcu_head_on_stack(&rcu.head); } EXPORT_SYMBOL_GPL(synchronize_rcu_bh); diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h index ac7d80fa895c..0e4f420245d9 100644 --- a/kernel/rcutree_plugin.h +++ b/kernel/rcutree_plugin.h @@ -557,11 +557,13 @@ void synchronize_rcu(void) if (!rcu_scheduler_active) return; + init_rcu_head_on_stack(&rcu.head); init_completion(&rcu.completion); /* Will wake me after RCU finished. */ call_rcu(&rcu.head, wakeme_after_rcu); /* Wait for it. */ wait_for_completion(&rcu.completion); + destroy_rcu_head_on_stack(&rcu.head); } EXPORT_SYMBOL_GPL(synchronize_rcu); -- cgit v1.2.3