From: Tejun Heo <tj@kernel.org>
Date: Fri, 19 Oct 2012 00:52:07 +0000 (-0700)
Subject: Revert "cgroup: Drop task_lock(parent) on cgroup_fork()"
X-Git-Tag: v3.7-rc3~35^2~1
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=9bb71308b8133d643648776243e4d5599b1c193d;p=pandora-kernel.git

Revert "cgroup: Drop task_lock(parent) on cgroup_fork()"

This reverts commit 7e381b0eb1e1a9805c37335562e8dc02e7d7848c.

The commit incorrectly assumed that fork path always performed
threadgroup_change_begin/end() and depended on that for
synchronization against task exit and cgroup migration paths instead
of explicitly grabbing task_lock().

threadgroup_change is not locked when forking a new process (as
opposed to a new thread in the same process) and even if it were it
wouldn't be effective as different processes use different threadgroup
locks.

Revert the incorrect optimization.

Signed-off-by: Tejun Heo <tj@kernel.org>
LKML-Reference: <20121008020000.GB2575@localhost>
Acked-by: Li Zefan <lizefan@huawei.com>
Bitterly-Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: stable@vger.kernel.org
---

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