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Date: Fri, 6 Jan 2012 14:06:25 -0800
From: Andrew Morton <akpm@linux-foundation.org>
To: Mike Galbraith <efault@gmx.de>
Cc: David Rientjes <rientjes@google.com>, Paul Menage <paul@paulmenage.org>,
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        Li Zefan <lizf@cn.fujitsu.com>,
        Peter Zijlstra <a.p.zijlstra@chello.nl>
Subject: Re: [resubmit] Re: [patch-final] Re: patch] cpusets, cgroups:
 disallow attaching kthreadd
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On Wed, 07 Dec 2011 05:36:57 +0100
Mike Galbraith <efault@gmx.de> wrote:

> cpusets, cgroups: disallow attaching kthreadd
> 
> 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.

Someone's been screwing around in linux-next during the merge window. 
afacit some patch which was previously there has magically disappeared.
That killed your patch - the original version of the
kernel/sched/core.c chagne applies to the new linux-next but the
kernel/cpuset.c part is all wrecked.

There's been a lot of screwing around this time.  There were a large
number of rejects merging current linux-next onto current mainline this
morning due to conflicting changes in tools/perf/.