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sched, kvm: Fix race condition involving sched_in_preempt_notifers

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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 <[email protected]>
Acked-by: Avi Kivity <[email protected]>
Cc: Peter Zijlstra <[email protected]>
LKML-Reference: <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
This commit is contained in:
Tejun Heo authored and Ingo Molnar committed 2009-11-15 09:59:54 +01:00
1 parent 055a00865d
commit 498657a478
1 file changed
+1 -1
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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)) {