From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757336Ab2JSJd4 (ORCPT ); Fri, 19 Oct 2012 05:33:56 -0400 Received: from szxga01-in.huawei.com ([119.145.14.64]:4372 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753908Ab2JSJdy (ORCPT ); Fri, 19 Oct 2012 05:33:54 -0400 Message-ID: <50811E5E.1090205@huawei.com> Date: Fri, 19 Oct 2012 17:33:18 +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: Michal Hocko CC: , , , Tejun Heo , Johannes Weiner , KAMEZAWA Hiroyuki , Balbir Singh Subject: Re: [PATCH 4/6] cgroups: forbid pre_destroy callback to fail References: <1350480648-10905-1-git-send-email-mhocko@suse.cz> <1350480648-10905-5-git-send-email-mhocko@suse.cz> In-Reply-To: <1350480648-10905-5-git-send-email-mhocko@suse.cz> Content-Type: text/plain; charset="GB2312" 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 On 2012/10/17 21:30, Michal Hocko wrote: > Now that mem_cgroup_pre_destroy callback doesn't fail finally we can > safely move on and forbit all the callbacks to fail. The last missing > piece is moving cgroup_call_pre_destroy after cgroup_clear_css_refs so > that css_tryget fails so no new charges for the memcg can happen. > The callbacks are also called from within cgroup_lock to guarantee that > no new tasks show up. I'm afraid this won't work. See commit 3fa59dfbc3b223f02c26593be69ce6fc9a940405 ("cgroup: fix potential deadlock in pre_destroy") > We could theoretically call them outside of the > lock but then we have to move after CGRP_REMOVED flag is set. > > Signed-off-by: Michal Hocko > --- > kernel/cgroup.c | 30 +++++++++--------------------- > 1 file changed, 9 insertions(+), 21 deletions(-)