From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753158AbaBNQu0 (ORCPT ); Fri, 14 Feb 2014 11:50:26 -0500 Received: from mail-qc0-f174.google.com ([209.85.216.174]:59636 "EHLO mail-qc0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753101AbaBNQuX (ORCPT ); Fri, 14 Feb 2014 11:50:23 -0500 Date: Fri, 14 Feb 2014 11:50:19 -0500 From: Tejun Heo To: Li Zefan Cc: cgroups@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH cgroup/for-3.14-fixes] cgroup: update cgroup_enable_task_cg_lists() to grab siglock Message-ID: <20140214165019.GI31544@htj.dyndns.org> References: <20140213182931.GB17608@htj.dyndns.org> <52FD9256.1080801@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <52FD9256.1080801@huawei.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, On Fri, Feb 14, 2014 at 11:49:42AM +0800, Li Zefan wrote: > Now the only race I see is caused by checking tsk->cg_list without locking > in cgroup_exit(): Yeah, that's the one I was trying to fix. > Your patch can fix this race, but after diving into the code I don't think > the race exists, because exit_mm() locks&unlocks task_lock, and exit_mm() > is called after exit_signal() and before cgroup_exit(), and task_lock is > also taken by cgroup_enable_task_cg_lists(). Ah, okay, so there's a task_lock somewhere in the exit path. Extremely fragile, but not broken. > I totally agree the code is fragile and we should take your patch. I just > want to make it clear if the bug exists in real life or not, and then we > can write better changelog and decide to queue the patch for 3.14 or 3.15 > and decide to mark it for stable or not. Yeap, no reason to mark it for -stable if it doesn't actually happen. I'll update the description and respin it for for-3.15. Thanks! -- tejun