From mboxrd@z Thu Jan  1 00:00:00 1970
From: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Subject: Re: [PATCH] cgroups: fix a css_set not found bug in
 cgroup_attach_proc
Date: Thu, 15 Dec 2011 13:23:29 -0800
Message-ID: <20111215212329.GH32002@google.com>
References: <1323977803-5385-1-git-send-email-msb@chromium.org>
Mime-Version: 1.0
Return-path: <cgroups-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;
        d=gmail.com; s=gamma;
        h=sender:date:from:to:cc:subject:message-id:references:mime-version
         :content-type:content-disposition:in-reply-to:user-agent;
        bh=hwazH1c5phDOrgAy1gijWMRqe2H6CYz2845Y5FOYUu0=;
        b=U5fS3u0czor0NT94GAdhI46wMbiLcSKU89sstvEoJFsowErfTaAGSfW+OuelkBsPZ1
         DZtAkxe3ENiv0mdiYUODkthYUTMolNlnUBf5seNxtl4C7otzTJav55vsyDJ6gDtRGXQ3
         GprucTYJCcaY5gjQWAiSDIDzncGFkdq6U1IsE=
Content-Disposition: inline
In-Reply-To: <1323977803-5385-1-git-send-email-msb-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>
Sender: cgroups-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
List-ID: <cgroups.vger.kernel.org>
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
To: Mandeep Singh Baines <msb-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>
Cc: Li Zefan <lizf-BthXqXjhjHXQFUHtdCDX3A@public.gmane.org>, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, stable-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, KAMEZAWA Hiroyuki <kamezawa.hiroyu-+CUm20s59erQFUHtdCDX3A@public.gmane.org>, Frederic Weisbecker <fweisbec-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>, Oleg Nesterov <oleg-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>, Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>, Paul Menage <paul-inf54ven1CmVyaH7bEyXVA@public.gmane.org>, Olof Johansson <olofj-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>

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?

Thanks.

-- 
tejun
--
To unsubscribe from this list: send the line "unsubscribe cgroups" in
the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html