From mboxrd@z Thu Jan  1 00:00:00 1970
From: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Subject: Re: Is not locking task_lock in cgroup_fork() safe?
Date: Thu, 18 Oct 2012 17:38:35 -0700
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To: Frederic Weisbecker <fweisbec-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Cc: Li Zefan <lizefan-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>, containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, LKML <linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>

Hello, Frederic.

On Thu, Oct 18, 2012 at 10:53:47PM +0200, Frederic Weisbecker wrote:
> > For now, I'll revert the patches and cc stable.  Let's think about
> > improving it later.
> 
> Ok for reverting in cgroup_fork(). Is it necessary for the
> cgroup_post_fork() thing? I don't immediately see any race involved
> there.

Even if there isn't an actual race, the comment is dead wrong.  I'm
reverting the following three patches.  Let's try again later.

  7e381b0eb1 ("cgroup: Drop task_lock(parent) on cgroup_fork()")
  7e3aa30ac8 ("cgroup: Remove task_lock() from cgroup_post_fork()")
  c84cdf75cc ("cgroup: Remove unnecessary task_lock before fetching css_set on migration")

Thanks.

-- 
tejun