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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
hifive-unleashed-5.1
Linus Torvalds 2011-06-07 19:20:28 -07:00
parent ef2398019b 6c6c54e180
commit 6715a52a58
3 changed files with 26 additions and 10 deletions
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1
include/linux/sched.h
View File

@ -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

2
kernel/lockdep.c
View File

@ -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);

33
kernel/sched.c
View File

@ -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);