From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Thu, 4 Dec 2008 19:17:02 +0900 From: Daisuke Nishimura Subject: Re: [Experimental][PATCH 19/21] memcg-fix-pre-destroy.patch Message-Id: <20081204191702.d845d79c.nishimura@mxp.nes.nec.co.jp> In-Reply-To: <20081204184309.da8264c0.kamezawa.hiroyu@jp.fujitsu.com> References: <20081203134718.6b60986f.kamezawa.hiroyu@jp.fujitsu.com> <20081203141117.d3685413.kamezawa.hiroyu@jp.fujitsu.com> <20081204183428.19cbd22d.nishimura@mxp.nes.nec.co.jp> <20081204184309.da8264c0.kamezawa.hiroyu@jp.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: KAMEZAWA Hiroyuki 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 , nishimura@mxp.nes.nec.co.jp List-ID: On Thu, 4 Dec 2008 18:43:09 +0900, KAMEZAWA Hiroyuki wrote: > 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. > == > would be make sence. Thanks, Daisuke Nishimura. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org