Commit 498657a4 authored Nov 13, 2009 by Tejun Heo Committed by Ingo Molnar Nov 15, 2009

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>

parent 055a0086

kernel/sched.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -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)) {

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