[PATCH cgroup/for-3.7-fixes 2/2] Revert "cgroup: Drop task_lock(parent) on cgroup_fork()"

Li Zefan lizefan at huawei.com
Fri Oct 19 08:51:58 UTC 2012


On 2012/10/19 8:59, Tejun Heo wrote:
>>From c8b27924a8b6fd74066088f1cf07c256bbc6ed74 Mon Sep 17 00:00:00 2001
> From: Tejun Heo <tj at kernel.org>
> Date: Thu, 18 Oct 2012 17:52:07 -0700
> 
> 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 at kernel.org>
> LKML-Reference: <20121008020000.GB2575 at localhost>
> Cc: Frederic Weisbecker <fweisbec at gmail.com>
> Cc: Li Zefan <lizefan at huawei.com>
> Cc: stable at vger.kernel.org

Acked-by: Li Zefan <lizefan at huawei.com>



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