Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934997Ab3DIGmx (ORCPT ); Tue, 9 Apr 2013 02:42:53 -0400 Received: from cantor2.suse.de ([195.135.220.15]:39078 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753086Ab3DIGmw (ORCPT ); Tue, 9 Apr 2013 02:42:52 -0400 Date: Tue, 9 Apr 2013 08:42:49 +0200 From: Michal Hocko To: Tejun Heo 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: <20130409064239.GA29860@dhcp22.suse.cz> References: <51627DA9.7020507@huawei.com> <51627DBB.5050005@huawei.com> <20130408144750.GK17178@dhcp22.suse.cz> <20130408180335.GA22512@dhcp22.suse.cz> <20130408213646.GB17159@mtj.dyndns.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130408213646.GB17159@mtj.dyndns.org> 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: 1699 Lines: 48 On Mon 08-04-13 14:36:46, Tejun Heo wrote: > 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? Yes, it is. My selective blindness strikes again :/ I was convinced that it was memcg we tested use_hierarchy for... Sorry about all the churn. > > @@ -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; > > } > > -- Michal Hocko SUSE Labs -- 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/