cgroup: fix umount vs cgroup_event_remove() race
cgroup: fix umount vs cgroup_event_remove() race

 commit 5db9a4d99b0157a513944e9a44d29c9cec2e91dc
 Author: Tejun Heo <546b05909706652891a87f7bfe385ae147f61f91@kernel.org>
 Date:   Sat Jul 7 16:08:18 2012 -0700

     cgroup: fix cgroup hierarchy umount race

This commit fixed a race caused by the dput() in css_dput_fn(), but
the dput() in cgroup_event_remove() can also lead to the same BUG().

Signed-off-by: Li Zefan <a8167b9d27aca9c6624754deb52c4c6420eded04@huawei.com>
Signed-off-by: Tejun Heo <546b05909706652891a87f7bfe385ae147f61f91@kernel.org>
Cc: 4fbacc2fa0ffdbb11bf1ad6925b886ebd08dd15f@vger.kernel.org

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs