Messages in this thread Patch in this message | | | Date | Fri, 13 Nov 2009 18:33:53 +0900 | From | Tejun Heo <> | Subject | [PATCH 2.6.32-rc6] 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. Move it before finish_arch_switch(). This also makes in notifiers symmetric to out notifiers in terms of locking - now both are called under rq lock.
NOT_SIGNED_OFF_YET Cc: Ingo Molnar <mingo@redhat.com> Cc: Avi Kivity <avi@redhat.com> --- Avi, I think kvm should be fine with this but I haven't tested it. Does this look okay to you? If so, can you please route this through kvm tree with my signoff?
Thanks.
kernel/sched.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
Index: work/kernel/sched.c =================================================================== --- work.orig/kernel/sched.c +++ work/kernel/sched.c @@ -2751,9 +2751,9 @@ static void finish_task_switch(struct rq 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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