Re: [PATCH] cgroups: fix a css_set not found bug in cgroup_attach_proc

[Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@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
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