From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753110AbaENEVs (ORCPT ); Wed, 14 May 2014 00:21:48 -0400 Received: from szxga01-in.huawei.com ([119.145.14.64]:32645 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751236AbaENEVq (ORCPT ); Wed, 14 May 2014 00:21:46 -0400 Message-ID: <5372EF45.8060701@huawei.com> Date: Wed, 14 May 2014 12:21:25 +0800 From: Li Zefan User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:17.0) Gecko/20130801 Thunderbird/17.0.8 MIME-Version: 1.0 To: Tejun Heo CC: , , Subject: Re: [PATCHSET cgroup/for-3.16] cgroup: iterate cgroup_subsys_states directly References: <1399671091-23867-1-git-send-email-tj@kernel.org> In-Reply-To: <1399671091-23867-1-git-send-email-tj@kernel.org> Content-Type: text/plain; charset="GB2312" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.177.18.230] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Tejun, On 2014/5/10 5:31, Tejun Heo wrote: > Hello, > > Currently, while csses (cgroup_subsys_states) have ->parent linkage > too, only cgroups form full tree through their ->children and > ->sibling fields and css iterations naturally is implemented by > iterating cgroups and then dereferencing the css for the specified > subsystem. > > There are now use cases where controllers need to iterate through > csses regardless of their online state as long as they have positive What use cases are we talking about here? > reference. This can't easily be achieved by iterating cgroups because > its css pointer array needs to be cleared on offline and there may be > multiple dying csses for a cgroup for the same subsystem and there's > only one pointer per cgroup-subsystem pair. >