Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757743Ab2JSIvX (ORCPT ); Fri, 19 Oct 2012 04:51:23 -0400 Received: from szxga01-in.huawei.com ([119.145.14.64]:19877 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753183Ab2JSIvU (ORCPT ); Fri, 19 Oct 2012 04:51:20 -0400 Message-ID: <5081145A.2010307@huawei.com> Date: Fri, 19 Oct 2012 16:50:34 +0800 From: Li Zefan User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:15.0) Gecko/20120907 Thunderbird/15.0.1 MIME-Version: 1.0 To: Tejun Heo CC: Frederic Weisbecker , , , LKML Subject: Re: Is not locking task_lock in cgroup_fork() safe? References: <20121008020000.GB2575@localhost> <20121016193341.GD16166@google.com> <20121018200705.GG13370@google.com> <20121019003835.GE13370@google.com> <20121019005801.GF13370@google.com> In-Reply-To: <20121019005801.GF13370@google.com> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.135.68.215] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1089 Lines: 28 On 2012/10/19 8:58, Tejun Heo wrote: > Hello, again. > > On Thu, Oct 18, 2012 at 05:38:35PM -0700, Tejun Heo wrote: >> Even if there isn't an actual race, the comment is dead wrong. I'm >> reverting the following three patches. Let's try again later. >> >> 7e381b0eb1 ("cgroup: Drop task_lock(parent) on cgroup_fork()") >> 7e3aa30ac8 ("cgroup: Remove task_lock() from cgroup_post_fork()") > > So, after some more looking, I think the following is correct and > doesn't need to be reverted. It's depending on threadgroup locking > from migration path to synchronize against exit path which is always > performed. > >> c84cdf75cc ("cgroup: Remove unnecessary task_lock before fetching css_set on migration") > > Frederic, were you trying to say that the above commit is correct? > Li, do you agree? > This one does look innocent. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/