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

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Pull scheduler fixes from Ingo Molnar:
 "Two fixes: one for a lost wakeup, the other to fix the compiler
  optimizing out preempt operations on ARM64 (and possibly other non-x86
  architectures)"

* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched/core: Fix remote wakeups
  sched/preempt: Fix preempt_count manipulations
This commit is contained in:
Linus Torvalds 2016-05-25 17:11:43 -07:00
commit f89eae4ee7
3 changed files with 14 additions and 9 deletions
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4
include/asm-generic/preempt.h
View file

@ -7,10 +7,10 @@
static __always_inline int preempt_count(void)
{
return current_thread_info()->preempt_count;
return READ_ONCE(current_thread_info()->preempt_count);
}
static __always_inline int *preempt_count_ptr(void)
static __always_inline volatile int *preempt_count_ptr(void)
{
return &current_thread_info()->preempt_count;
}

1
include/linux/sched.h
View file

@ -1539,6 +1539,7 @@ struct task_struct {
unsigned sched_reset_on_fork:1;
unsigned sched_contributes_to_load:1;
unsigned sched_migrated:1;
unsigned sched_remote_wakeup:1;
unsigned :0; /* force alignment to the next boundary */
/* unserialized, strictly 'current' */

18
kernel/sched/core.c
View file

@ -1768,13 +1768,15 @@ void sched_ttwu_pending(void)
cookie = lockdep_pin_lock(&rq->lock);
while (llist) {
int wake_flags = 0;
p = llist_entry(llist, struct task_struct, wake_entry);
llist = llist_next(llist);
/*
* See ttwu_queue(); we only call ttwu_queue_remote() when
* its a x-cpu wakeup.
*/
ttwu_do_activate(rq, p, WF_MIGRATED, cookie);
if (p->sched_remote_wakeup)
wake_flags = WF_MIGRATED;
ttwu_do_activate(rq, p, wake_flags, cookie);
}
lockdep_unpin_lock(&rq->lock, cookie);
@ -1819,10 +1821,12 @@ void scheduler_ipi(void)
irq_exit();
}
static void ttwu_queue_remote(struct task_struct *p, int cpu)
static void ttwu_queue_remote(struct task_struct *p, int cpu, int wake_flags)
{
struct rq *rq = cpu_rq(cpu);
p->sched_remote_wakeup = !!(wake_flags & WF_MIGRATED);
if (llist_add(&p->wake_entry, &cpu_rq(cpu)->wake_list)) {
if (!set_nr_if_polling(rq->idle))
smp_send_reschedule(cpu);
@ -1869,7 +1873,7 @@ static void ttwu_queue(struct task_struct *p, int cpu, int wake_flags)
#if defined(CONFIG_SMP)
if (sched_feat(TTWU_QUEUE) && !cpus_share_cache(smp_processor_id(), cpu)) {
sched_clock_cpu(cpu); /* sync clocks x-cpu */
ttwu_queue_remote(p, cpu);
ttwu_queue_remote(p, cpu, wake_flags);
return;
}
#endif