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Subject: Re: patch] cpusets, cgroups: disallow attaching kthreadd
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Mike Galbraith <efault@gmx.de>
Cc: LKML <linux-kernel@vger.kernel.org>, Tejun Heo <htejun@gmail.com>,
        Li Zefan <lizf@cn.fujitsu.com>, Paul Menage <paul@paulmenage.org>,
        David Rientjes <rientjes@google.com>
Date: Tue, 18 Oct 2011 11:06:03 +0200
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On Tue, 2011-10-18 at 10:47 +0200, Mike Galbraith wrote:
> On Tue, 2011-10-18 at 10:42 +0200, Peter Zijlstra wrote:
> 
> > Why special case these two, why not simply disallow moving kthreadd into
> > _any_ cgroup what so ever and be done with it?
> 
> These were the cases where it hurt, and cpusets don't have to be a
> component of a cgroup.  So we'd still need the cpuset bit.

but but but,, cpusetes are a cgroup thingy?!

> > 
> > ---
> > diff --git a/kernel/cgroup.c b/kernel/cgroup.c
> > index 453100a..18eed58 100644
> > --- a/kernel/cgroup.c
> > +++ b/kernel/cgroup.c
> > @@ -1824,6 +1824,9 @@ int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
> >  	struct cgroup *oldcgrp;
> >  	struct cgroupfs_root *root = cgrp->root;
> >  
> > +	if (tsk == kthreadd_task)
> > +		return -EINVAL;
> > +
> >  	/* Nothing to do if the task is already in that cgroup */
> >  	oldcgrp = task_cgroup_from_root(tsk, root);
> >  	if (cgrp == oldcgrp)
> > 
> 
>