From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756406AbYKUI4f (ORCPT ); Fri, 21 Nov 2008 03:56:35 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754743AbYKUIw4 (ORCPT ); Fri, 21 Nov 2008 03:52:56 -0500 Received: from cn.fujitsu.com ([222.73.24.84]:51442 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1754635AbYKUIwz (ORCPT ); Fri, 21 Nov 2008 03:52:55 -0500 Message-ID: <4926762A.7000602@cn.fujitsu.com> Date: Fri, 21 Nov 2008 16:49:46 +0800 From: Lai Jiangshan User-Agent: Thunderbird 2.0.0.17 (Windows/20080914) MIME-Version: 1.0 To: Andrew Morton , Paul Menage , Linux Kernel Mailing List , Linux Containers Subject: [PATCH 1/2] cgroups: enhance task_cgroup() Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org task_cgroup() calls cgroup_subsys_state(). and we must use rcu_read_lock() to protect cgroup_subsys_state(). so we must use rcu_read_lock() to protect task_cgroup(). but it'll not so friendly to caller: the callers of task_cgroup() have held cgroup_lock(). it means that struct cgroup will not be freed. So this patch add rcu_read_lock() in task_cgroup() to enhance task_cgroup(). And we do NOT NEED FIX task_cgroup()'s callers, and cgroup_lock() can protect task_cgroup(). Signed-off-by: Lai Jiangshan --- diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index 1164963..22901ff 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -359,6 +360,10 @@ static inline struct cgroup* task_cgroup(struct task_struct *task, int subsys_id) { - return task_subsys_state(task, subsys_id)->cgroup; + struct cgroup *ret; + rcu_read_lock(); + ret = task_subsys_state(task, subsys_id)->cgroup; + rcu_read_unlock(); + return ret; } int cgroup_clone(struct task_struct *tsk, struct cgroup_subsys *ss,