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sched, kvm: Fix race condition involving sched_in_preempt_notifers 

In finish_task_switch(), fire_sched_in_preempt_notifiers() is
called after finish_lock_switch().

However, depending on architecture, preemption can be enabled after
finish_lock_switch() which breaks the semantics of preempt
notifiers.

So move it before finish_arch_switch(). This also makes the in-
notifiers symmetric to out- notifiers in terms of locking - now
both are called under rq lock.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Avi Kivity <avi@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <4AFD2801.7020900@kernel.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Tejun Heo 2009-11-13 18:33:53 +09:00 committed by Ingo Molnar
parent 055a00865d
commit 498657a478
1 changed files with 1 additions and 1 deletions
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2
kernel/sched.c
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@ -2758,9 +2758,9 @@ static void finish_task_switch(struct rq *rq, struct task_struct *prev)
prev_state = prev->state;
finish_arch_switch(prev);
perf_event_task_sched_in(current, cpu_of(rq));
fire_sched_in_preempt_notifiers(current);
finish_lock_switch(rq, prev);
fire_sched_in_preempt_notifiers(current);
if (mm)
mmdrop(mm);
if (unlikely(prev_state == TASK_DEAD)) {