From mboxrd@z Thu Jan 1 00:00:00 1970 From: Li Zefan Subject: Re: [PATCH v2] cgroup: Remove task_lock() from cgroup_post_fork() Date: Tue, 27 Dec 2011 09:33:35 +0800 Message-ID: <4EF9206F.3090207@cn.fujitsu.com> References: <1324610723-30080-1-git-send-email-fweisbec@gmail.com> <20111223230013.GV17084@google.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20111223230013.GV17084-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Tejun Heo Cc: Frederic Weisbecker , Containers , Oleg Nesterov , LKML , Mandeep Singh Baines , Cgroups , Andrew Morton , Paul Menage Tejun Heo wrote: > On Fri, Dec 23, 2011 at 04:25:23AM +0100, Frederic Weisbecker wrote: >> cgroup_post_fork() is protected between threadgroup_change_begin() >> and threadgroup_change_end() against concurrent changes of the >> child's css_set in cgroup_task_migrate(). Also the child can't >> exit and call cgroup_exit() at this stage, this means it's css_set >> can't be changed with init_css_set concurrently. >> >> For these reasons, we don't need to hold task_lock() on the child >> because it's css_set can only remain stable in this place. >> >> Let's remove the lock there. >> >> v2: Update comment to explain that we are safe against >> cgroup_exit() >> >> Signed-off-by: Frederic Weisbecker >> Cc: Li Zefan >> Cc: Tejun Heo >> Cc: Containers >> Cc: Cgroups >> Cc: KAMEZAWA Hiroyuki >> Cc: Oleg Nesterov >> Cc: Andrew Morton >> Cc: Paul Menage >> Cc: Mandeep Singh Baines > > Li, does this look good to you? > Acked-by: Li Zefan From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754023Ab1L0Bba (ORCPT ); Mon, 26 Dec 2011 20:31:30 -0500 Received: from cn.fujitsu.com ([222.73.24.84]:60662 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1753513Ab1L0BbY (ORCPT ); Mon, 26 Dec 2011 20:31:24 -0500 Message-ID: <4EF9206F.3090207@cn.fujitsu.com> Date: Tue, 27 Dec 2011 09:33:35 +0800 From: Li Zefan User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.2.9) Gecko/20100921 Fedora/3.1.4-1.fc14 Thunderbird/3.1.4 MIME-Version: 1.0 To: Tejun Heo CC: Frederic Weisbecker , LKML , Containers , Cgroups , KAMEZAWA Hiroyuki , Oleg Nesterov , Andrew Morton , Paul Menage , Mandeep Singh Baines Subject: Re: [PATCH v2] cgroup: Remove task_lock() from cgroup_post_fork() References: <1324610723-30080-1-git-send-email-fweisbec@gmail.com> <20111223230013.GV17084@google.com> In-Reply-To: <20111223230013.GV17084@google.com> X-MIMETrack: Itemize by SMTP Server on mailserver/fnst(Release 8.5.1FP4|July 25, 2010) at 2011-12-27 09:30:32, Serialize by Router on mailserver/fnst(Release 8.5.1FP4|July 25, 2010) at 2011-12-27 09:30:34, Serialize complete at 2011-12-27 09:30:34 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Tejun Heo wrote: > On Fri, Dec 23, 2011 at 04:25:23AM +0100, Frederic Weisbecker wrote: >> cgroup_post_fork() is protected between threadgroup_change_begin() >> and threadgroup_change_end() against concurrent changes of the >> child's css_set in cgroup_task_migrate(). Also the child can't >> exit and call cgroup_exit() at this stage, this means it's css_set >> can't be changed with init_css_set concurrently. >> >> For these reasons, we don't need to hold task_lock() on the child >> because it's css_set can only remain stable in this place. >> >> Let's remove the lock there. >> >> v2: Update comment to explain that we are safe against >> cgroup_exit() >> >> Signed-off-by: Frederic Weisbecker >> Cc: Li Zefan >> Cc: Tejun Heo >> Cc: Containers >> Cc: Cgroups >> Cc: KAMEZAWA Hiroyuki >> Cc: Oleg Nesterov >> Cc: Andrew Morton >> Cc: Paul Menage >> Cc: Mandeep Singh Baines > > Li, does this look good to you? > Acked-by: Li Zefan