From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx202.postini.com [74.125.245.202]) by kanga.kvack.org (Postfix) with SMTP id AFC4F6B0005 for ; Mon, 8 Apr 2013 17:36:52 -0400 (EDT) Received: by mail-qe0-f48.google.com with SMTP id 2so3355022qea.35 for ; Mon, 08 Apr 2013 14:36:51 -0700 (PDT) Date: Mon, 8 Apr 2013 14:36:46 -0700 From: Tejun Heo Subject: Re: [PATCH 1/8] cgroup: implement cgroup_is_ancestor() Message-ID: <20130408213646.GB17159@mtj.dyndns.org> References: <51627DA9.7020507@huawei.com> <51627DBB.5050005@huawei.com> <20130408144750.GK17178@dhcp22.suse.cz> <20130408180335.GA22512@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130408180335.GA22512@dhcp22.suse.cz> Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: Li Zefan , Andrew Morton , Glauber Costa , KAMEZAWA Hiroyuki , Johannes Weiner , LKML , Cgroups , linux-mm@kvack.org On Mon, Apr 08, 2013 at 08:03:44PM +0200, Michal Hocko wrote: > __mem_cgroup_same_or_subtree relies on css_is_ancestor if hierarchy is > enabled for ages. This, however, is not correct because use_hierarchy > doesn't need to be true all the way up the cgroup hierarchy. Consider > the following example: > root (use_hierarchy=0) > \ > A (use_hierarchy=0) > \ > B (use_hierarchy=1) > \ > C (use_hierarchy=1) > > __mem_cgroup_same_or_subtree(A, C) would return true even though C is > not from the same hierarchy subtree. The bug shouldn't be critical but > at least dump_tasks might print unrelated tasks (via > task_in_mem_cgroup). Huh? Isn't that avoided by the !root_memcg->use_hierarchy test? > @@ -1470,9 +1470,12 @@ bool __mem_cgroup_same_or_subtree(const struct mem_cgroup *root_memcg, > { > if (root_memcg == memcg) > return true; > - if (!root_memcg->use_hierarchy || !memcg) ^^^^^^^^^^^^^^^^^^^^^^^^^^ > + if (!memcg) > return false; > - return css_is_ancestor(&memcg->css, &root_memcg->css); > + while ((memcg = parent_mem_cgroup(memcg))) > + if (memcg == root_memcg) > + return true; > + return false; > } > > static bool mem_cgroup_same_or_subtree(const struct mem_cgroup *root_memcg, > -- > 1.7.10.4 > > -- > Michal Hocko > SUSE Labs -- tejun -- 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