linux-kernel - Re: [patch] cgroups: disallow attaching kthreadd

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Date:	Mon, 23 Apr 2012 11:05:05 -0700
From:	Tejun Heo <tj@...nel.org>
To:	Mike Galbraith <mgalbraith@...e.de>
Cc:	Li Zefan <lizefan@...wei.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	David Rientjes <rientjes@...gle.com>,
	Paul Menage <paul@...lmenage.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [patch] cgroups: disallow attaching kthreadd

On Sat, Apr 21, 2012 at 09:13:46AM +0200, Mike Galbraith wrote:
> On Sat, 2012-04-21 at 14:54 +0800, Li Zefan wrote:
> 
> > forgot rcu_read_unlock() ?
> 
> Eek, we don't need another one of those. Thanks.
> 
> > Otherwise Acked-by: Li Zefan <lizefan@...wei.com>
> 
> cgroups: disallow attaching kthreadd or PF_THREAD_BOUND threads
> 
> Allowing kthreadd to be moved to a non-root group makes no sense, it being
> a global resource, and needlessly leads unsuspecting users toward trouble.
> 
> 1. An RT workqueue worker thread spawned in a task group with no rt_runtime
> allocated is not schedulable.  Simple user error, but harmful to the box.
> 
> 2. A worker thread which acquires PF_THREAD_BOUND can never leave a cpuset,
> rendering the cpuset immortal.
> 
> Save the user some unexpected trouble, just say no.
> 
> Signed-off-by: Mike Galbraith <mgalbraith@...e.de>
> Acked-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
> Acked-by: Thomas Gleixner <tglx@...utronix.de>
> Acked-by: Li Zefan <lizefan@...wei.com>

Applied to cgroup/for-3.5.  Thanks.

-- 
tejun
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