From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756132AbaICJLT (ORCPT ); Wed, 3 Sep 2014 05:11:19 -0400 Received: from forward18.mail.yandex.net ([95.108.253.143]:44270 "EHLO forward18.mail.yandex.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755341AbaICJLR (ORCPT ); Wed, 3 Sep 2014 05:11:17 -0400 X-Greylist: delayed 394 seconds by postgrey-1.27 at vger.kernel.org; Wed, 03 Sep 2014 05:11:17 EDT From: Kirill Tkhai To: Oleg Nesterov , Kautuk Consul , Peter Zijlstra , Ingo Molnar Cc: Andrew Morton , Michal Hocko , David Rientjes , Ionut Alexa , Guillaume Morin , "linux-kernel@vger.kernel.org" In-Reply-To: <20140825155738.GA5944@redhat.com> References: <1408964064-21447-1-git-send-email-consul.kautuk@gmail.com> <20140825155738.GA5944@redhat.com> Subject: Re: [PATCH 1/1] do_exit(): Solve possibility of BUG() due to race with try_to_wake_up() MIME-Version: 1.0 Message-Id: <3702911409735076@web26g.yandex.ru> X-Mailer: Yamail [ http://yandex.ru ] 5.0 Date: Wed, 03 Sep 2014 13:04:36 +0400 Content-Transfer-Encoding: 7bit Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 25.08.2014, 20:01, "Oleg Nesterov" : > Peter, do you remember another problem with TASK_DEAD we discussed recently? > (prev_state == TASK_DEAD detection in finish_task_switch() still looks racy). One more problem with task_dead just to mention it here. Below is racy with the change of sched_class: if (prev->sched_class->task_dead) prev->sched_class->task_dead(prev); switched_from_dl() does not cancel running timers. So, if dl_task_timer() is slow (it is unhappy with rq->lock acquiring), the timer is executing when tasks is already dead. Kirill