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From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Chris Mason <chris.mason@oracle.com>,
	Frank Rowand <frank.rowand@am.sony.com>,
	Ingo Molnar <mingo@elte.hu>, Thomas Gleixner <tglx@linutronix.de>,
	Mike Galbraith <efault@gmx.de>, Oleg Nesterov <oleg@redhat.com>,
	Paul Turner <pjt@google.com>, Jens Axboe <axboe@kernel.dk>,
	Yong Zhang <yong.zhang0@gmail.com>
Cc: linux-kernel@vger.kernel.org, Peter Zijlstra <a.p.zijlstra@chello.nl>
Subject: [PATCH 03/21] mutex: Use p->on_cpu for the adaptive spin
Date: Tue, 05 Apr 2011 17:23:41 +0200
Message-ID: <20110405152728.826338173@chello.nl> (raw)
In-Reply-To: <20110405152338.692966333@chello.nl>

[-- Attachment #0: sched-on_cpu-use.patch --]
[-- Type: text/plain, Size: 5922 bytes --]

Since we now have p->on_cpu unconditionally available, use it to
re-implement mutex_spin_on_owner.

Requested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Reviewed-by: Frank Rowand <frank.rowand@am.sony.com>
---
 include/linux/mutex.h |    2 -
 include/linux/sched.h |    2 -
 kernel/mutex-debug.c  |    2 -
 kernel/mutex-debug.h  |    2 -
 kernel/mutex.c        |    2 -
 kernel/mutex.h        |    2 -
 kernel/sched.c        |   83 +++++++++++++++++++-------------------------------
 7 files changed, 39 insertions(+), 56 deletions(-)

Index: linux-2.6/include/linux/mutex.h
===================================================================
--- linux-2.6.orig/include/linux/mutex.h
+++ linux-2.6/include/linux/mutex.h
@@ -51,7 +51,7 @@ struct mutex {
 	spinlock_t		wait_lock;
 	struct list_head	wait_list;
 #if defined(CONFIG_DEBUG_MUTEXES) || defined(CONFIG_SMP)
-	struct thread_info	*owner;
+	struct task_struct	*owner;
 #endif
 #ifdef CONFIG_DEBUG_MUTEXES
 	const char 		*name;
Index: linux-2.6/kernel/mutex-debug.c
===================================================================
--- linux-2.6.orig/kernel/mutex-debug.c
+++ linux-2.6/kernel/mutex-debug.c
@@ -75,7 +75,7 @@ void debug_mutex_unlock(struct mutex *lo
 		return;
 
 	DEBUG_LOCKS_WARN_ON(lock->magic != lock);
-	DEBUG_LOCKS_WARN_ON(lock->owner != current_thread_info());
+	DEBUG_LOCKS_WARN_ON(lock->owner != current);
 	DEBUG_LOCKS_WARN_ON(!lock->wait_list.prev && !lock->wait_list.next);
 	mutex_clear_owner(lock);
 }
Index: linux-2.6/kernel/mutex-debug.h
===================================================================
--- linux-2.6.orig/kernel/mutex-debug.h
+++ linux-2.6/kernel/mutex-debug.h
@@ -29,7 +29,7 @@ extern void debug_mutex_init(struct mute
 
 static inline void mutex_set_owner(struct mutex *lock)
 {
-	lock->owner = current_thread_info();
+	lock->owner = current;
 }
 
 static inline void mutex_clear_owner(struct mutex *lock)
Index: linux-2.6/kernel/mutex.c
===================================================================
--- linux-2.6.orig/kernel/mutex.c
+++ linux-2.6/kernel/mutex.c
@@ -160,7 +160,7 @@ __mutex_lock_common(struct mutex *lock, 
 	 */
 
 	for (;;) {
-		struct thread_info *owner;
+		struct task_struct *owner;
 
 		/*
 		 * If we own the BKL, then don't spin. The owner of
Index: linux-2.6/kernel/mutex.h
===================================================================
--- linux-2.6.orig/kernel/mutex.h
+++ linux-2.6/kernel/mutex.h
@@ -19,7 +19,7 @@
 #ifdef CONFIG_SMP
 static inline void mutex_set_owner(struct mutex *lock)
 {
-	lock->owner = current_thread_info();
+	lock->owner = current;
 }
 
 static inline void mutex_clear_owner(struct mutex *lock)
Index: linux-2.6/kernel/sched.c
===================================================================
--- linux-2.6.orig/kernel/sched.c
+++ linux-2.6/kernel/sched.c
@@ -4034,70 +4034,53 @@ asmlinkage void __sched schedule(void)
 EXPORT_SYMBOL(schedule);
 
 #ifdef CONFIG_MUTEX_SPIN_ON_OWNER
-/*
- * Look out! "owner" is an entirely speculative pointer
- * access and not reliable.
- */
-int mutex_spin_on_owner(struct mutex *lock, struct thread_info *owner)
-{
-	unsigned int cpu;
-	struct rq *rq;
 
-	if (!sched_feat(OWNER_SPIN))
-		return 0;
+static inline bool owner_running(struct mutex *lock, struct task_struct *owner)
+{
+	bool ret = false;
 
-#ifdef CONFIG_DEBUG_PAGEALLOC
-	/*
-	 * Need to access the cpu field knowing that
-	 * DEBUG_PAGEALLOC could have unmapped it if
-	 * the mutex owner just released it and exited.
-	 */
-	if (probe_kernel_address(&owner->cpu, cpu))
-		return 0;
-#else
-	cpu = owner->cpu;
-#endif
+	rcu_read_lock();
+	if (lock->owner != owner)
+		goto fail;
 
 	/*
-	 * Even if the access succeeded (likely case),
-	 * the cpu field may no longer be valid.
+	 * Ensure we emit the owner->on_cpu, dereference _after_ checking
+	 * lock->owner still matches owner, if that fails, owner might
+	 * point to free()d memory, if it still matches, the rcu_read_lock()
+	 * ensures the memory stays valid.
 	 */
-	if (cpu >= nr_cpumask_bits)
-		return 0;
+	barrier();
 
-	/*
-	 * We need to validate that we can do a
-	 * get_cpu() and that we have the percpu area.
-	 */
-	if (!cpu_online(cpu))
-		return 0;
+	ret = owner->on_cpu;
+fail:
+	rcu_read_unlock();
 
-	rq = cpu_rq(cpu);
+	return ret;
+}
 
-	for (;;) {
-		/*
-		 * Owner changed, break to re-assess state.
-		 */
-		if (lock->owner != owner) {
-			/*
-			 * If the lock has switched to a different owner,
-			 * we likely have heavy contention. Return 0 to quit
-			 * optimistic spinning and not contend further:
-			 */
-			if (lock->owner)
-				return 0;
-			break;
-		}
+/*
+ * Look out! "owner" is an entirely speculative pointer
+ * access and not reliable.
+ */
+int mutex_spin_on_owner(struct mutex *lock, struct task_struct *owner)
+{
+	if (!sched_feat(OWNER_SPIN))
+		return 0;
 
-		/*
-		 * Is that owner really running on that cpu?
-		 */
-		if (task_thread_info(rq->curr) != owner || need_resched())
+	while (owner_running(lock, owner)) {
+		if (need_resched())
 			return 0;
 
 		arch_mutex_cpu_relax();
 	}
 
+	/*
+	 * If the owner changed to another task there is likely
+	 * heavy contention, stop spinning.
+	 */
+	if (lock->owner)
+		return 0;
+
 	return 1;
 }
 #endif
Index: linux-2.6/include/linux/sched.h
===================================================================
--- linux-2.6.orig/include/linux/sched.h
+++ linux-2.6/include/linux/sched.h
@@ -360,7 +360,7 @@ extern signed long schedule_timeout_inte
 extern signed long schedule_timeout_killable(signed long timeout);
 extern signed long schedule_timeout_uninterruptible(signed long timeout);
 asmlinkage void schedule(void);
-extern int mutex_spin_on_owner(struct mutex *lock, struct thread_info *owner);
+extern int mutex_spin_on_owner(struct mutex *lock, struct task_struct *owner);
 
 struct nsproxy;
 struct user_namespace;



  parent reply index

Thread overview: 152+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-04-05 15:23 [PATCH 00/21] sched: Reduce runqueue lock contention -v6 Peter Zijlstra
2011-04-05 15:23 ` [PATCH 01/21] sched: Provide scheduler_ipi() callback in response to smp_send_reschedule() Peter Zijlstra
2011-04-13 21:15   ` Tony Luck
2011-04-13 21:38     ` Peter Zijlstra
2011-04-14  8:31   ` [tip:sched/locking] " tip-bot for Peter Zijlstra
2011-04-05 15:23 ` [PATCH 02/21] sched: Always provide p->on_cpu Peter Zijlstra
2011-04-14  8:31   ` [tip:sched/locking] " tip-bot for Peter Zijlstra
2011-04-05 15:23 ` Peter Zijlstra [this message]
2011-04-14  8:32   ` [tip:sched/locking] mutex: Use p->on_cpu for the adaptive spin tip-bot for Peter Zijlstra
2011-04-05 15:23 ` [PATCH 04/21] sched: Change the ttwu success details Peter Zijlstra
2011-04-13  9:23   ` Peter Zijlstra
2011-04-13 10:48     ` Peter Zijlstra
2011-04-13 11:06       ` Peter Zijlstra
2011-04-13 18:39         ` Tejun Heo
2011-04-13 19:11           ` Peter Zijlstra
2011-04-14  8:32   ` [tip:sched/locking] sched: Change the ttwu() " tip-bot for Peter Zijlstra
2011-04-05 15:23 ` [PATCH 05/21] sched: Clean up ttwu stats Peter Zijlstra
2011-04-14  8:33   ` [tip:sched/locking] sched: Clean up ttwu() stats tip-bot for Peter Zijlstra
2011-04-05 15:23 ` [PATCH 06/21] sched: Provide p->on_rq Peter Zijlstra
2011-04-14  8:33   ` [tip:sched/locking] " tip-bot for Peter Zijlstra
2011-04-05 15:23 ` [PATCH 07/21] sched: Serialize p->cpus_allowed and ttwu() using p->pi_lock Peter Zijlstra
2011-04-14  8:34   ` [tip:sched/locking] " tip-bot for Peter Zijlstra
2011-04-05 15:23 ` [PATCH 08/21] sched: Drop the rq argument to sched_class::select_task_rq() Peter Zijlstra
2011-04-14  8:34   ` [tip:sched/locking] " tip-bot for Peter Zijlstra
2011-04-05 15:23 ` [PATCH 09/21] sched: Remove rq argument to sched_class::task_waking() Peter Zijlstra
2011-04-14  8:35   ` [tip:sched/locking] " tip-bot for Peter Zijlstra
2011-04-05 15:23 ` [PATCH 10/21] sched: Deal with non-atomic min_vruntime reads on 32bits Peter Zijlstra
2011-04-14  8:35   ` [tip:sched/locking] " tip-bot for Peter Zijlstra
2011-04-05 15:23 ` [PATCH 11/21] sched: Delay task_contributes_to_load() Peter Zijlstra
2011-04-14  8:35   ` [tip:sched/locking] " tip-bot for Peter Zijlstra
2011-04-05 15:23 ` [PATCH 12/21] sched: Also serialize ttwu_local() with p->pi_lock Peter Zijlstra
2011-04-14  8:36   ` [tip:sched/locking] " tip-bot for Peter Zijlstra
2011-04-05 15:23 ` [PATCH 13/21] sched: Add p->pi_lock to task_rq_lock() Peter Zijlstra
2011-04-14  8:36   ` [tip:sched/locking] " tip-bot for Peter Zijlstra
2011-06-01 13:58     ` Arne Jansen
2011-06-01 16:35       ` Peter Zijlstra
2011-06-01 17:20         ` Arne Jansen
2011-06-01 18:09           ` Peter Zijlstra
2011-06-01 18:44             ` Peter Zijlstra
2011-06-01 19:30               ` Arne Jansen
2011-06-01 21:09                 ` Linus Torvalds
2011-06-03  9:15                   ` Peter Zijlstra
2011-06-03 10:02                     ` Arne Jansen
2011-06-03 10:30                       ` Peter Zijlstra
2011-06-03 11:52                         ` Arne Jansen
2011-06-05  8:17                         ` Ingo Molnar
2011-06-05  8:53                           ` Arne Jansen
2011-06-05  9:41                             ` Ingo Molnar
2011-06-05  9:45                               ` Ingo Molnar
2011-06-05  9:43                           ` Arne Jansen
2011-06-05  9:55                             ` Ingo Molnar
2011-06-05 10:22                               ` Arne Jansen
2011-06-05 11:01                                 ` Ingo Molnar
2011-06-05 11:19                                   ` [debug patch] printk: Add a printk killswitch to robustify NMI watchdog messages Ingo Molnar
2011-06-05 11:36                                     ` Ingo Molnar
2011-06-05 11:57                                       ` Arne Jansen
2011-06-05 13:39                                         ` Ingo Molnar
2011-06-05 13:54                                           ` Arne Jansen
2011-06-05 14:06                                             ` Ingo Molnar
2011-06-05 14:45                                               ` Arne Jansen
2011-06-05 14:10                                             ` Ingo Molnar
2011-06-05 14:31                                               ` Arne Jansen
2011-06-05 15:13                                                 ` Ingo Molnar
2011-06-05 15:26                                                   ` Ingo Molnar
2011-06-05 15:32                                                     ` Ingo Molnar
2011-06-05 16:07                                                       ` Arne Jansen
2011-06-05 16:35                                                         ` Arne Jansen
2011-06-05 16:50                                                           ` Arne Jansen
2011-06-05 17:20                                                             ` Ingo Molnar
2011-06-05 17:42                                                               ` Arne Jansen
2011-06-05 18:59                                                                 ` Ingo Molnar
2011-06-05 19:30                                                                   ` Arne Jansen
2011-06-05 19:44                                                                     ` Ingo Molnar
2011-06-05 20:15                                                                       ` Arne Jansen
2011-06-06  6:56                                                                         ` Arne Jansen
2011-06-06  9:01                                                                         ` Peter Zijlstra
2011-06-06  9:18                                                                           ` Arne Jansen
2011-06-06  9:24                                                                             ` Peter Zijlstra
2011-06-06  9:52                                                                               ` Peter Zijlstra
2011-06-06 10:00                                                                           ` Arne Jansen
2011-06-06 10:26                                                                             ` Peter Zijlstra
2011-06-06 13:25                                                                               ` Peter Zijlstra
2011-06-06 15:04                                                                           ` Ingo Molnar
2011-06-06 15:08                                                                             ` Ingo Molnar
2011-06-06 17:44                                                                               ` Mike Galbraith
2011-06-07  5:20                                                                           ` Mike Galbraith
2011-06-06 13:10                                                                   ` Ingo Molnar
2011-06-06 13:12                                                                     ` Peter Zijlstra
2011-06-06 13:21                                                                       ` Ingo Molnar
2011-06-06 13:31                                                                         ` Peter Zijlstra
2011-06-06  7:34                                                     ` Arne Jansen
2011-06-05 15:34                                                   ` Arne Jansen
2011-06-06  8:38                                                   ` Peter Zijlstra
2011-06-06 14:58                                                     ` Ingo Molnar
2011-06-06 15:09                                                       ` Peter Zijlstra
2011-06-06 15:47                                                         ` Peter Zijlstra
2011-06-06 15:52                                                           ` Ingo Molnar
2011-06-06 16:00                                                             ` Peter Zijlstra
2011-06-06 16:08                                                               ` Ingo Molnar
2011-06-06 16:12                                                                 ` Peter Zijlstra
2011-06-06 16:17                                                                   ` Ingo Molnar
2011-06-06 16:38                                                                     ` Arne Jansen
2011-06-06 16:45                                                                       ` Arne Jansen
2011-06-06 16:53                                                                         ` Peter Zijlstra
2011-06-06 17:07                                                                         ` Ingo Molnar
2011-06-06 17:11                                                                           ` Peter Zijlstra
2011-06-08 15:50                                                                             ` Peter Zijlstra
2011-06-08 19:17                                                                               ` Ingo Molnar
2011-06-08 19:27                                                                                 ` Linus Torvalds
2011-06-08 20:32                                                                                   ` Peter Zijlstra
2011-06-08 20:53                                                                                     ` Linus Torvalds
2011-06-08 20:54                                                                                     ` Thomas Gleixner
2011-06-08 19:45                                                                                 ` Peter Zijlstra
2011-06-08 20:52                                                                                   ` Ingo Molnar
2011-06-08 21:49                                                                                     ` Peter Zijlstra
2011-06-08 21:57                                                                                       ` Thomas Gleixner
2011-06-06 16:44                                                                     ` Peter Zijlstra
2011-06-06 16:50                                                                       ` Peter Zijlstra
2011-06-06 17:13                                                                         ` Ingo Molnar
2011-06-06 17:04                                                                       ` Peter Zijlstra
2011-06-06 17:11                                                                       ` Ingo Molnar
2011-06-06 17:57                                                                         ` Arne Jansen
2011-06-06 18:07                                                                           ` Ingo Molnar
2011-06-06 18:14                                                                             ` Arne Jansen
2011-06-06 18:19                                                                             ` Peter Zijlstra
2011-06-06 22:08                                                                               ` Ingo Molnar
2011-06-03 12:44                       ` [tip:sched/locking] sched: Add p->pi_lock to task_rq_lock() Linus Torvalds
2011-06-03 13:05                         ` Arne Jansen
2011-06-04 21:29                           ` Linus Torvalds
2011-06-04 22:08                             ` Peter Zijlstra
2011-06-04 22:50                               ` Linus Torvalds
2011-06-05  6:01                               ` Arne Jansen
2011-06-05  7:57                                 ` Mike Galbraith
2011-04-05 15:23 ` [PATCH 14/21] sched: Drop rq->lock from first part of wake_up_new_task() Peter Zijlstra
2011-04-14  8:37   ` [tip:sched/locking] " tip-bot for Peter Zijlstra
2011-04-05 15:23 ` [PATCH 15/21] sched: Drop rq->lock from sched_exec() Peter Zijlstra
2011-04-14  8:37   ` [tip:sched/locking] " tip-bot for Peter Zijlstra
2011-04-05 15:23 ` [PATCH 16/21] sched: Remove rq->lock from the first half of ttwu() Peter Zijlstra
2011-04-14  8:38   ` [tip:sched/locking] " tip-bot for Peter Zijlstra
2011-04-05 15:23 ` [PATCH 17/21] sched: Remove rq argument from ttwu_stat() Peter Zijlstra
2011-04-14  8:38   ` [tip:sched/locking] " tip-bot for Peter Zijlstra
2011-04-05 15:23 ` [PATCH 18/21] sched: Rename ttwu_post_activation Peter Zijlstra
2011-04-14  8:39   ` [tip:sched/locking] sched: Rename ttwu_post_activation() to ttwu_do_wakeup() tip-bot for Peter Zijlstra
2011-04-05 15:23 ` [PATCH 19/21] sched: Restructure ttwu some more Peter Zijlstra
2011-04-14  8:39   ` [tip:sched/locking] sched: Restructure ttwu() " tip-bot for Peter Zijlstra
2011-04-05 15:23 ` [PATCH 20/21] sched: Move the second half of ttwu() to the remote cpu Peter Zijlstra
2011-04-14  8:39   ` [tip:sched/locking] " tip-bot for Peter Zijlstra
2011-04-05 15:23 ` [PATCH 21/21] sched: Remove need_migrate_task() Peter Zijlstra
2011-04-14  8:40   ` [tip:sched/locking] " tip-bot for Peter Zijlstra
2011-04-05 15:59 ` [PATCH 00/21] sched: Reduce runqueue lock contention -v6 Peter Zijlstra
2011-04-06 11:00 ` Peter Zijlstra
2011-04-27 16:54 ` Dave Kleikamp

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