From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756840AbaC0Pf2 (ORCPT ); Thu, 27 Mar 2014 11:35:28 -0400 Received: from aserp1040.oracle.com ([141.146.126.69]:20005 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754893AbaC0PfZ (ORCPT ); Thu, 27 Mar 2014 11:35:25 -0400 Message-ID: <5334452D.4080200@oracle.com> Date: Thu, 27 Mar 2014 11:35:09 -0400 From: Sasha Levin User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.4.0 MIME-Version: 1.0 To: Li Zefan , Tejun Heo CC: containers@lists.linux-foundation.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] cgroup: missing rcu read lock around task_css_set References: <1393729211-937-1-git-send-email-sasha.levin@oracle.com> <20140303223327.GB26523@mtj.dyndns.org> <5315057F.3030602@oracle.com> <20140303224505.GE26523@mtj.dyndns.org> <53150989.70307@oracle.com> <53160B6D.8020501@oracle.com> <20140304194741.GA2204@htj.dyndns.org> <53167662.5000801@huawei.com> In-Reply-To: <53167662.5000801@huawei.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Source-IP: ucsinet21.oracle.com [156.151.31.93] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/04/2014 07:57 PM, Li Zefan wrote: > On 2014/3/5 3:47, Tejun Heo wrote: >> On Tue, Mar 04, 2014 at 12:20:45PM -0500, Sasha Levin wrote: >>>> Hrm... there is a PF_EXITING check there already: >>>> >>>> #define task_css_set_check(task, __c) \ >>>> rcu_dereference_check((task)->cgroups, \ >>>> lockdep_is_held(&cgroup_mutex) || \ >>>> lockdep_is_held(&css_set_rwsem) || \ >>>> ((task)->flags & PF_EXITING) || (__c)) >>>> >>>> I see it's not happening on Linus's master so I'll run a bisection to figure out what broke it. >>> >>> Hi Tejun, >>> >>> It bisects down to your patch: "cgroup: drop task_lock() protection >>> around task->cgroups". I'll look into it later unless it's obvious >>> to you. >> >> Hmmm... maybe I'm confused and PF_EXITING is not set there and >> task_lock was what held off the lockdep warning. Confused.... >> > > Because this cgroup_exit() is called in a failure path in copy_process(). It seems there was no conclusion here and it still happens in -next, anything we can do about it? Thanks, Sasha