Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755566AbYLJCYx (ORCPT ); Tue, 9 Dec 2008 21:24:53 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753832AbYLJCYp (ORCPT ); Tue, 9 Dec 2008 21:24:45 -0500 Received: from fgwmail7.fujitsu.co.jp ([192.51.44.37]:60116 "EHLO fgwmail7.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753391AbYLJCYo (ORCPT ); Tue, 9 Dec 2008 21:24:44 -0500 Date: Wed, 10 Dec 2008 11:23:48 +0900 From: KAMEZAWA Hiroyuki To: Li Zefan Cc: "linux-mm@kvack.org" , "balbir@linux.vnet.ibm.com" , "nishimura@mxp.nes.nec.co.jp" , "menage@google.com" , "kosaki.motohiro@jp.fujitsu.com" , "linux-kernel@vger.kernel.org" Subject: Re: [RFC][PATCH 1/6] memcg: fix pre_destory handler Message-Id: <20081210112348.3060f1d8.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <493F2737.9060901@cn.fujitsu.com> References: <20081209200213.0e2128c1.kamezawa.hiroyu@jp.fujitsu.com> <20081209200647.a1fa76a9.kamezawa.hiroyu@jp.fujitsu.com> <493F2737.9060901@cn.fujitsu.com> Organization: FUJITSU Co. LTD. X-Mailer: Sylpheed 2.5.0 (GTK+ 2.10.14; i686-pc-mingw32) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1703 Lines: 60 On Wed, 10 Dec 2008 10:19:35 +0800 Li Zefan wrote: > > +static bool memcg_is_obsolete(struct mem_cgroup *mem) > > +{ > > Will this function be called with mem->css.refcnt == 0? If yes, then > this function is racy. > > cg = mem->css.cgroup > cgroup_diput() > mem_cgroup_destroy() > mem->css.cgroup = NULL; > kfree(cg); > if (!cg || cgroup_is_removed(cg)...) > > (accessing invalid cg) > Hmm. then we have to add flag to css itself, anyway. > > + struct cgroup *cg = mem->css.cgroup; > > + /* > > + * "Being Removed" means pre_destroy() handler is called. > > + * After "pre_destroy" handler is called, memcg should not > > + * have any additional charges. > > + * This means there are small races for mis-accounting. But this > > + * mis-accounting should happen only under swap-in opration. > > + * (Attachin new task will fail if cgroup is under rmdir()). > > + */ > > + > > + if (!cg || cgroup_is_removed(cg) || cgroup_is_being_removed(cg)) > > + return true; > > + return false; > > +} > > + > > ... > > > static void mem_cgroup_destroy(struct cgroup_subsys *ss, > > struct cgroup *cont) > > { > > - mem_cgroup_free(mem_cgroup_from_cont(cont)); > > + struct mem_cgroup *mem = mem_cgroup_from_cont(cont): > > + mem_cgroup_free(mem); > > + /* forget */ > > + mem->css.cgroup = NULL; > > mem might already be destroyed by mem_cgroup_free(mem). > Ah, maybe. will fix. Thanks, -Kame -- 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/