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Subject: Re: patch] cpusets, cgroups: disallow attaching kthreadd
From: Mike Galbraith <efault@gmx.de>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>
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>
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Date: Tue, 18 Oct 2011 11:23:45 +0200
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On Tue, 2011-10-18 at 11:06 +0200, Peter Zijlstra wrote:
> 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?!

By golly, mount -t cpuset and the thing does say type cgroup.  How 'bout
that, learn something new every day.  Dinkier is better.

> > > ---
> > > 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)
> > > 
> > 
> > 
>