Commit 498657a4 authored by Tejun Heo's avatar Tejun Heo Committed by Ingo Molnar
Browse files

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: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarAvi Kivity <avi@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <4AFD2801.7020900@kernel.org>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 055a0086
......@@ -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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