linux-kernel - Re: [PATCH] cgroups: fix a css_set not found bug in cgroup_attach

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Message-ID: <20111219171307.GG24519@google.com>
Date:	Mon, 19 Dec 2011 09:13:07 -0800
From:	Tejun Heo <tj@...nel.org>
To:	Li Zefan <lizf@...fujitsu.com>
Cc:	Mandeep Singh Baines <msb@...omium.org>,
	linux-kernel@...r.kernel.org,
	containers@...ts.linux-foundation.org, cgroups@...r.kernel.org,
	stable@...nel.org,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Oleg Nesterov <oleg@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Paul Menage <paul@...lmenage.org>,
	Olof Johansson <olofj@...omium.org>
Subject: Re: [PATCH] cgroups: fix a css_set not found bug in
 cgroup_attach_proc

On Fri, Dec 16, 2011 at 10:12:51AM +0800, Li Zefan wrote:
> Tejun Heo wrote:
> > On Thu, Dec 15, 2011 at 11:36:43AM -0800, Mandeep Singh Baines wrote:
> >> There is a BUG when migrating a PF_EXITING proc. Since css_set_prefetch()
> >> is not called for the PF_EXITING case, find_existing_css_set() will return
> >> NULL inside cgroup_task_migrate() causing a BUG.
> >>
> >> This bug is easy to reproduce. Create a zombie and echo its pid to
> >> cgroup.procs.
> >>
> >> $ cat zombie.c
> >> \#include <unistd.h>
> >>
> >> int main()
> >> {
> >>   if (fork())
> >>       pause();
> >>   return 0;
> >> }
> >> $
> >>
> >> We are hitting this bug pretty regularly on ChromeOS.
> >>
> >> This bug is already fixed by Tejun Heo's cgroup patchset which is
> >> targetted for the next merge window:
> >>
> >> https://lkml.org/lkml/2011/11/1/356
> >>
> >> I've create a smaller patch here which just fixes this bug so that a
> >> fix can be merged into the current release and stable.
> > 
> > Looks safe to me.  Li?
> > 
> 
> It should be fine.
> 
> Reviewed-by: Li Zefan <lizf@...fujitsu.com>

Applied to cgroup/for-fixes-3.2.  Will push to Linus in a couple of
days.  It's already rc6 and a bit late tho.

Thank you.

-- 
tejun
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