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Commit 6715a52a authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge branch 'sched-urgent-for-linus' of... 

Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  sched: Fix/clarify set_task_cpu() locking rules
  lockdep: Fix lock_is_held() on recursion
  sched: Fix schedstat.nr_wakeups_migrate
  sched: Fix cross-cpu clock sync on remote wakeups
parents ef239801 6c6c54e1

include/linux/sched.h

+1 −0
Original line number Diff line number Diff line
@@ -1063,6 +1063,7 @@ struct sched_domain; 
 */

#define WF_SYNC		0x01		/* waker goes to sleep after wakup */

#define WF_FORK		0x02		/* child wakeup after fork */

#define WF_MIGRATED	0x04		/* internal use, task got migrated */



#define ENQUEUE_WAKEUP		1

#define ENQUEUE_HEAD		2

kernel/lockdep.c

+1 −1
Original line number Diff line number Diff line
@@ -3426,7 +3426,7 @@ int lock_is_held(struct lockdep_map *lock) 
	int ret = 0;



	if (unlikely(current->lockdep_recursion))

		return ret;

		return 1; /* avoid false negative lockdep_assert_held() */



	raw_local_irq_save(flags);

	check_flags(flags);

kernel/sched.c

+24 −9
Original line number Diff line number Diff line
@@ -605,10 +605,10 @@ static inline int cpu_of(struct rq *rq) 
/*

 * Return the group to which this tasks belongs.

 *

 * We use task_subsys_state_check() and extend the RCU verification

 * with lockdep_is_held(&p->pi_lock) because cpu_cgroup_attach()

 * holds that lock for each task it moves into the cgroup. Therefore

 * by holding that lock, we pin the task to the current cgroup.

 * We use task_subsys_state_check() and extend the RCU verification with

 * pi->lock and rq->lock because cpu_cgroup_attach() holds those locks for each

 * task it moves into the cgroup. Therefore by holding either of those locks,

 * we pin the task to the current cgroup.

 */

static inline struct task_group *task_group(struct task_struct *p)

{
@@ -616,7 +616,8 @@ static inline struct task_group *task_group(struct task_struct *p) 
	struct cgroup_subsys_state *css;



	css = task_subsys_state_check(p, cpu_cgroup_subsys_id,

			lockdep_is_held(&p->pi_lock));

			lockdep_is_held(&p->pi_lock) ||

			lockdep_is_held(&task_rq(p)->lock));

	tg = container_of(css, struct task_group, css);



	return autogroup_task_group(p, tg);
@@ -2200,6 +2201,16 @@ void set_task_cpu(struct task_struct *p, unsigned int new_cpu) 
			!(task_thread_info(p)->preempt_count & PREEMPT_ACTIVE));



#ifdef CONFIG_LOCKDEP

	/*

	 * The caller should hold either p->pi_lock or rq->lock, when changing

	 * a task's CPU. ->pi_lock for waking tasks, rq->lock for runnable tasks.

	 *

	 * sched_move_task() holds both and thus holding either pins the cgroup,

	 * see set_task_rq().

	 *

	 * Furthermore, all task_rq users should acquire both locks, see

	 * task_rq_lock().

	 */

	WARN_ON_ONCE(debug_locks && !(lockdep_is_held(&p->pi_lock) ||

				      lockdep_is_held(&task_rq(p)->lock)));

#endif
@@ -2447,6 +2458,10 @@ ttwu_stat(struct task_struct *p, int cpu, int wake_flags) 
		}

		rcu_read_unlock();

	}



	if (wake_flags & WF_MIGRATED)

		schedstat_inc(p, se.statistics.nr_wakeups_migrate);



#endif /* CONFIG_SMP */



	schedstat_inc(rq, ttwu_count);
@@ -2455,9 +2470,6 @@ ttwu_stat(struct task_struct *p, int cpu, int wake_flags) 
	if (wake_flags & WF_SYNC)

		schedstat_inc(p, se.statistics.nr_wakeups_sync);



	if (cpu != task_cpu(p))

		schedstat_inc(p, se.statistics.nr_wakeups_migrate);



#endif /* CONFIG_SCHEDSTATS */

}
@@ -2600,6 +2612,7 @@ static void ttwu_queue(struct task_struct *p, int cpu) 


#if defined(CONFIG_SMP)

	if (sched_feat(TTWU_QUEUE) && cpu != smp_processor_id()) {

		sched_clock_cpu(cpu); /* sync clocks x-cpu */

		ttwu_queue_remote(p, cpu);

		return;

	}
@@ -2674,8 +2687,10 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags) 
		p->sched_class->task_waking(p);



	cpu = select_task_rq(p, SD_BALANCE_WAKE, wake_flags);

	if (task_cpu(p) != cpu)

	if (task_cpu(p) != cpu) {

		wake_flags |= WF_MIGRATED;

		set_task_cpu(p, cpu);

	}

#endif /* CONFIG_SMP */



	ttwu_queue(p, cpu);