From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755983AbZKMJeB (ORCPT ); Fri, 13 Nov 2009 04:34:01 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755953AbZKMJd6 (ORCPT ); Fri, 13 Nov 2009 04:33:58 -0500 Received: from hera.kernel.org ([140.211.167.34]:53403 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755974AbZKMJdy (ORCPT ); Fri, 13 Nov 2009 04:33:54 -0500 Message-ID: <4AFD2801.7020900@kernel.org> Date: Fri, 13 Nov 2009 18:33:53 +0900 From: Tejun Heo User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; ko-KR; rv:1.9.1.4pre) Gecko/20090915 SUSE/3.0b4-3.6 Thunderbird/3.0b4 MIME-Version: 1.0 To: Avi Kivity CC: lkml , Ingo Molnar , Linus Torvalds Subject: [PATCH 2.6.32-rc6] sched, kvm: fix race condition involving sched_in_preempt_notifers Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 Cc: Avi Kivity --- 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)) {