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authorTejun Heo <tj@kernel.org>2009-11-13 18:33:53 +0900
committerIngo Molnar <mingo@elte.hu>2009-11-15 09:59:54 +0100
commit498657a478c60be092208422fefa9c7b248729c2 (patch)
treec04542330fbbfaaa863fbec0f565b79c89df7033 /kernel
parent055a00865dcfc8e61f3cbefbb879c9577bd36ae5 (diff)
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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>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/sched.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/sched.c b/kernel/sched.c
index 701eca4..cea2bea 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -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)) {