From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755032AbaCDTrr (ORCPT ); Tue, 4 Mar 2014 14:47:47 -0500 Received: from mail-qc0-f174.google.com ([209.85.216.174]:47705 "EHLO mail-qc0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752984AbaCDTrp (ORCPT ); Tue, 4 Mar 2014 14:47:45 -0500 Date: Tue, 4 Mar 2014 14:47:41 -0500 From: Tejun Heo To: Sasha Levin Cc: lizefan@huawei.com, 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 Message-ID: <20140304194741.GA2204@htj.dyndns.org> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <53160B6D.8020501@oracle.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 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.... Thanks. -- tejun