From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755757AbaEPVaL (ORCPT ); Fri, 16 May 2014 17:30:11 -0400 Received: from forward7l.mail.yandex.net ([84.201.143.140]:45039 "EHLO forward7l.mail.yandex.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753701AbaEPVaJ (ORCPT ); Fri, 16 May 2014 17:30:09 -0400 X-Yandex-Uniq: acc410b4-5a08-4631-a3e5-64d94f57a5e3 Authentication-Results: smtp8.mail.yandex.net; dkim=pass header.i=@yandex.ru Subject: [PATCH] sched/dl: Fix race between dl_task_timer() and sched_setaffinity() From: Kirill Tkhai To: linux-kernel@vger.kernel.org Cc: peterz@infradead.org, tkhai@yandex.ru, mingo@redhat.com, stable@vger.kernel.org, juri.lelli@gmail.com Date: Sat, 17 May 2014 01:30:03 +0400 Message-ID: <20140516213003.10384.7946.stgit@localhost> User-Agent: StGit/0.17.1-dirty MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The race is in unlocked task_rq() access. In pair with parallel call of sched_setaffinity() it may be a reason of corruption of internal rq's data. Signed-off-by: Kirill Tkhai CC: Juri Lelli CC: Peter Zijlstra CC: Ingo Molnar Cc: # v3.14 --- kernel/sched/deadline.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index 800e99b..ffb023a 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -513,9 +513,16 @@ static enum hrtimer_restart dl_task_timer(struct hrtimer *timer) struct sched_dl_entity, dl_timer); struct task_struct *p = dl_task_of(dl_se); - struct rq *rq = task_rq(p); + struct rq *rq; +again: + rq = task_rq(p); raw_spin_lock(&rq->lock); + if (unlikely(rq != task_rq(p))) { + raw_spin_unlock(&rq->lock); + goto again; + } + /* * We need to take care of a possible races here. In fact, the * task might have changed its scheduling policy to something