Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030626Ab2K3PKK (ORCPT ); Fri, 30 Nov 2012 10:10:10 -0500 Received: from mx2.parallels.com ([64.131.90.16]:46208 "EHLO mx2.parallels.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1030598Ab2K3PKI (ORCPT ); Fri, 30 Nov 2012 10:10:08 -0500 Message-ID: <50B8CC3D.3040901@parallels.com> Date: Fri, 30 Nov 2012 19:09:49 +0400 From: Glauber Costa User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/17.0 Thunderbird/17.0 MIME-Version: 1.0 To: Tejun Heo CC: Michal Hocko , Kamezawa Hiroyuki , , , , , , , , , Subject: Re: [PATCHSET cgroup/for-3.8] cpuset: decouple cpuset locking from cgroup core References: <1354138460-19286-1-git-send-email-tj@kernel.org> <50B8263C.7060908@jp.fujitsu.com> <50B875B4.2020507@parallels.com> <20121130092435.GD29317@dhcp22.suse.cz> <50B87F84.7040206@parallels.com> <20121130094959.GE29317@dhcp22.suse.cz> <50B883B5.8020705@parallels.com> <20121130145924.GA3873@htj.dyndns.org> In-Reply-To: <20121130145924.GA3873@htj.dyndns.org> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit X-Originating-IP: [46.39.244.6] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1804 Lines: 41 On 11/30/2012 06:59 PM, Tejun Heo wrote: > Hello, > > On Fri, Nov 30, 2012 at 02:00:21PM +0400, Glauber Costa wrote: >> Now, what I am actually seeing with cgroup creation, is that the >> children will copy a lot of the values from the parent, like swappiness, >> hierarchy, etc. Once the child copies it, we should no longer be able to >> change those values in the parent: otherwise we'll get funny things like >> parent.use_hierarchy = 1, child.use_hierarchy = 0. > > So, the best way to do this is from ->css_online(). If memcg > synchronizes and inherits from ->css_online(), it can guarantee that > the new cgroup will be visible in any following iterations. Just have > an online flag which is turned on and off from ->css_on/offline() and > ignore any cgroups w/o online set. > >> One option is to take a global lock in memcg_alloc_css(), and keep it >> locked until we did all the cgroup bookkeeping, and then unlock it in >> css_online. But I am guessing Tejun won't like it very much. > > No, please *NEVER* *EVER* do that. You'll be creating a bunch of > locking dependencies as cgroup walks through different controllers. > > memcg should be able to synchornize fully both css on/offlining and > task attachments in memcg proper. Let's please be boring about > locking. > Of course, there was a purely rhetorical statement, as indicated by "Tejun won't like it very much" =p Take a look at the final result, I just posted a couple of hours ago. Let me know if there is still something extremely funny, and I'll look into fixing it. -- 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/