From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753390Ab3AOGMI (ORCPT ); Tue, 15 Jan 2013 01:12:08 -0500 Received: from szxga01-in.huawei.com ([119.145.14.64]:46644 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750872Ab3AOGMH (ORCPT ); Tue, 15 Jan 2013 01:12:07 -0500 Message-ID: <50F4F2F1.8070107@huawei.com> Date: Tue, 15 Jan 2013 14:10:57 +0800 From: Li Zefan User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:17.0) Gecko/17.0 Thunderbird/17.0 MIME-Version: 1.0 To: Tejun Heo CC: Sasha Levin , LKML , Cgroups Subject: [PATCH 1/2] cpuset: fix RCU lockdep splat Content-Type: text/plain; charset="GB2312" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.135.68.215] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Reading /proc//cpuset triggered RCU warning, and this bug was introduced by Commit 5d21cc2db040d01f8c19b8602f6987813e1176b4 ("cpuset: replace cgroup_mutex locking with cpuset internal locking") Here we can retreive tsk->cgroups and call cgroup_path() inside RCU read section. Reported-by: Sasha Levin Signed-off-by: Li Zefan --- kernel/cpuset.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/kernel/cpuset.c b/kernel/cpuset.c index 6aa5bbb..1a675e4 100644 --- a/kernel/cpuset.c +++ b/kernel/cpuset.c @@ -2678,15 +2678,15 @@ static int proc_cpuset_show(struct seq_file *m, void *unused_v) goto out_free; retval = -EINVAL; - mutex_lock(&cpuset_mutex); + rcu_read_lock(); css = task_subsys_state(tsk, cpuset_subsys_id); retval = cgroup_path(css->cgroup, buf, PAGE_SIZE); + rcu_read_unlock(); if (retval < 0) - goto out_unlock; + goto out_put_task; seq_puts(m, buf); seq_putc(m, '\n'); -out_unlock: - mutex_unlock(&cpuset_mutex); +out_put_task: put_task_struct(tsk); out_free: kfree(buf); -- 1.8.0.2