Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756792AbYLDJoS (ORCPT ); Thu, 4 Dec 2008 04:44:18 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753862AbYLDJoF (ORCPT ); Thu, 4 Dec 2008 04:44:05 -0500 Received: from fgwmail6.fujitsu.co.jp ([192.51.44.36]:48195 "EHLO fgwmail6.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752327AbYLDJoE (ORCPT ); Thu, 4 Dec 2008 04:44:04 -0500 Date: Thu, 4 Dec 2008 18:43:09 +0900 From: KAMEZAWA Hiroyuki To: Daisuke Nishimura Cc: "linux-mm@kvack.org" , "balbir@linux.vnet.ibm.com" , "kosaki.motohiro@jp.fujitsu.com" , "linux-kernel@vger.kernel.org" , "lizf@cn.fujitsu.com" , Paul Menage Subject: Re: [Experimental][PATCH 19/21] memcg-fix-pre-destroy.patch Message-Id: <20081204184309.da8264c0.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <20081204183428.19cbd22d.nishimura@mxp.nes.nec.co.jp> References: <20081203134718.6b60986f.kamezawa.hiroyu@jp.fujitsu.com> <20081203141117.d3685413.kamezawa.hiroyu@jp.fujitsu.com> <20081204183428.19cbd22d.nishimura@mxp.nes.nec.co.jp> 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: 1435 Lines: 45 On Thu, 4 Dec 2008 18:34:28 +0900 Daisuke Nishimura wrote: > Added CC: Paul Menage > > > @@ -2096,7 +2112,7 @@ static void mem_cgroup_get(struct mem_cg > > static void mem_cgroup_put(struct mem_cgroup *mem) > > { > > if (atomic_dec_and_test(&mem->refcnt)) { > > - if (!mem->obsolete) > > + if (!css_under_removal(&mem->css)) > > return; > > mem_cgroup_free(mem); > > } > I don't think it's safe to check css_under_removal here w/o cgroup_lock. > (It's safe *NOW* just because memcg is the only user of css->refcnt.) > > As Li said before, css_under_removal doesn't necessarily mean > this this group has been destroyed, but mem_cgroup will be freed. > > But adding cgroup_lock/unlock here causes another dead lock, > because mem_cgroup_get_next_node calls mem_cgroup_put. > > hmm.. hierarchical reclaim code will be re-written completely by [21/21], > so would it be better to change patch order or to take another approach ? > Hmm, ok. How about this ? == At initlization, mem_cgroup_create(), set memcg->refcnt to be 1. At destroy(), put this refcnt by 1. remove css_under_removal(&mem->css) check. == -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/