From: Li Zefan <lizefan@huawei.com>
Date: Fri, 1 Mar 2013 07:06:07 +0000 (+0800)
Subject: cgroup: no need to check css refs for release notification
X-Git-Tag: omap-for-v3.10/dt-fixes-for-merge-window~124^2~42
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f50daa704f36a6544a902c52b6cf37b0493dfc5d;p=pandora-kernel.git

cgroup: no need to check css refs for release notification

We no longer fail rmdir() when there're still css refs, so we don't
need to check css refs in check_for_release().

This also voids a bug. cgroup_has_css_refs() accesses subsys[i]
without cgroup_mutex, so it can race with cgroup_unload_subsys().

cgroup_has_css_refs()
...
  if (ss == NULL || ss->root != cgrp->root)

if ss pointers to net_cls_subsys, and cls_cgroup module is unloaded
right after the former check but before the latter, the memory that
net_cls_subsys resides has become invalid.

Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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