From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <493F2737.9060901@cn.fujitsu.com> Date: Wed, 10 Dec 2008 10:19:35 +0800 From: Li Zefan MIME-Version: 1.0 Subject: Re: [RFC][PATCH 1/6] memcg: fix pre_destory handler References: <20081209200213.0e2128c1.kamezawa.hiroyu@jp.fujitsu.com> <20081209200647.a1fa76a9.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <20081209200647.a1fa76a9.kamezawa.hiroyu@jp.fujitsu.com> 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" , "nishimura@mxp.nes.nec.co.jp" , "menage@google.com" , "kosaki.motohiro@jp.fujitsu.com" , "linux-kernel@vger.kernel.org" List-ID: > +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) > + 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). > } -- 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