From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752773AbZKOK35 (ORCPT ); Sun, 15 Nov 2009 05:29:57 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752654AbZKOK34 (ORCPT ); Sun, 15 Nov 2009 05:29:56 -0500 Received: from hera.kernel.org ([140.211.167.34]:46989 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752670AbZKOK3x (ORCPT ); Sun, 15 Nov 2009 05:29:53 -0500 Date: Sun, 15 Nov 2009 10:29:08 GMT From: tip-bot for Tejun Heo Cc: linux-kernel@vger.kernel.org, hpa@zytor.com, mingo@redhat.com, a.p.zijlstra@chello.nl, tj@kernel.org, tglx@linutronix.de, avi@redhat.com, mingo@elte.hu Reply-To: mingo@redhat.com, hpa@zytor.com, linux-kernel@vger.kernel.org, a.p.zijlstra@chello.nl, tj@kernel.org, tglx@linutronix.de, avi@redhat.com, mingo@elte.hu In-Reply-To: <4AFD2801.7020900@kernel.org> References: <4AFD2801.7020900@kernel.org> To: linux-tip-commits@vger.kernel.org Subject: [tip:sched/urgent] sched, kvm: Fix race condition involving sched_in_preempt_notifers Message-ID: Git-Commit-ID: 498657a478c60be092208422fefa9c7b248729c2 X-Mailer: tip-git-log-daemon MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 498657a478c60be092208422fefa9c7b248729c2 Gitweb: http://git.kernel.org/tip/498657a478c60be092208422fefa9c7b248729c2 Author: Tejun Heo AuthorDate: Fri, 13 Nov 2009 18:33:53 +0900 Committer: Ingo Molnar CommitDate: Sun, 15 Nov 2009 09:59:54 +0100 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 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)) {