From mboxrd@z Thu Jan 1 00:00:00 1970 From: Li Zefan Subject: [PATCH 1/2] cpuset: fix RCU lockdep splat Date: Tue, 15 Jan 2013 14:10:57 +0800 Message-ID: <50F4F2F1.8070107@huawei.com> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: Sender: linux-kernel-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii" To: Tejun Heo Cc: Sasha Levin , LKML , Cgroups 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