From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752880AbZBCE4T (ORCPT ); Mon, 2 Feb 2009 23:56:19 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751907AbZBCE4F (ORCPT ); Mon, 2 Feb 2009 23:56:05 -0500 Received: from e28smtp05.in.ibm.com ([59.145.155.5]:60790 "EHLO e28smtp05.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751724AbZBCE4D (ORCPT ); Mon, 2 Feb 2009 23:56:03 -0500 Date: Tue, 3 Feb 2009 10:25:56 +0530 From: Balbir Singh To: David Rientjes Cc: Li Zefan , KAMEZAWA Hiroyuki , Andrew Morton , "linux-kernel@vger.kernel.org" , "nishimura@mxp.nes.nec.co.jp" , "linux-mm@kvack.org" Subject: Re: [-mm patch] Show memcg information during OOM Message-ID: <20090203045556.GN918@balbir.in.ibm.com> Reply-To: balbir@linux.vnet.ibm.com References: <20090202125240.GA918@balbir.in.ibm.com> <20090202140849.GB918@balbir.in.ibm.com> <49879DE5.8030505@cn.fujitsu.com> <20090203044143.GM918@balbir.in.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * David Rientjes [2009-02-02 20:47:05]: > On Tue, 3 Feb 2009, Balbir Singh wrote: > > > > > diff --git a/mm/oom_kill.c b/mm/oom_kill.c > > > > index d3b9bac..b8e53ae 100644 > > > > --- a/mm/oom_kill.c > > > > +++ b/mm/oom_kill.c > > > > @@ -392,6 +392,7 @@ static int oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order, > > > > current->comm, gfp_mask, order, current->oomkilladj); > > > > task_lock(current); > > > > cpuset_print_task_mems_allowed(current); > > > > + mem_cgroup_print_mem_info(mem); > > > > > > I think this can be put outside the task lock. The lock is used to call task_cs() safely in > > > cpuset_print_task_mems_allowed(). > > > > > > > Thanks, I'll work on that in the next version. > > > > I was also wondering about this and assumed that it was necessary to > prevent the cgroup from disappearing during the oom. If task_lock() isn't > held, is the memcg->css.cgroup->dentry->d_name.name dereference always > safe without rcu? > oom_kill_process is called with tasklist_lock held (read-mode). That should suffice, no? The memcg cannot go away since it has other groups or tasks associated with it. -- Balbir