From 498657a478c60be092208422fefa9c7b248729c2 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Fri, 13 Nov 2009 18:33:53 +0900 Subject: [PATCH] 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 Acked-by: Avi Kivity Cc: Peter Zijlstra LKML-Reference: <4AFD2801.7020900@kernel.org> Signed-off-by: Ingo Molnar --- kernel/sched.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) 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)) { -- 2.7.4