Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S936298Ab3DHVgx (ORCPT ); Mon, 8 Apr 2013 17:36:53 -0400 Received: from mail-qe0-f44.google.com ([209.85.128.44]:32878 "EHLO mail-qe0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934661Ab3DHVgw (ORCPT ); Mon, 8 Apr 2013 17:36:52 -0400 Date: Mon, 8 Apr 2013 14:36:46 -0700 From: Tejun Heo To: Michal Hocko Cc: Li Zefan , Andrew Morton , Glauber Costa , KAMEZAWA Hiroyuki , Johannes Weiner , LKML , Cgroups , linux-mm@kvack.org 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> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1559 Lines: 50 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 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/