From fae9c791703606636c1220e47f6690660042ce7f Mon Sep 17 00:00:00 2001
From: Li Zefan <lizf@cn.fujitsu.com>
Date: Thu, 22 Apr 2010 17:30:00 +0800
Subject: [PATCH] cgroup: Fix an RCU warning in alloc_css_id()

With CONFIG_PROVE_RCU=y, a warning can be triggered:

  # mount -t cgroup -o memory xxx /mnt
  # mkdir /mnt/0

...
kernel/cgroup.c:4442 invoked rcu_dereference_check() without protection!
...

This is a false-positive. It's safe to directly access parent_css->id.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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