linux-kernel - Re: cpuset trouble after hibernate

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Message-Id: <20070915010807.b0055e7e.akpm@linux-foundation.org>
Date:	Sat, 15 Sep 2007 01:08:07 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Simon Derr <Simon.Derr@...l.net>
Cc:	Nicolas Capit <nicolas.capit@...g.fr>,
	linux-kernel@...r.kernel.org, Paul Jackson <pj@....com>,
	"Serge E. Hallyn" <serue@...ibm.com>,
	Paul Menage <menage@...gle.com>,
	Balbir Singh <balbir@...ibm.com>
Subject: Re: cpuset trouble after hibernate

On Mon, 10 Sep 2007 11:45:10 +0200 (CEST) Simon Derr <Simon.Derr@...l.net> wrote:

> On Sat, 8 Sep 2007, Nicolas Capit wrote:
> 
> > Hello,
> > 
> > This is my situation:
> >   - I mounted the pseudo cpuset filesystem into /dev/cpuset
> >   - I created a cpuset named oar with my 2 cpus
> > 
> > cat /dev/cpuset/oar/cpus 
> > 0-1
> > 
> >   - Then I hibernate my computer with 'echo -n "disk" >/sys/power/state'
> >   - After reboot:
> > 
> > cat /dev/cpuset/oar/cpus 
> > 0
> > 
> > Why did I lost a cpu?
> > Is this a normal behavior???
> 
> Hi Nicolas,
> 
> I believe this is related to the fact that hibernation uses the hotplug 
> subsystem to disable all CPUs except the boot CPU.
> 
> Thus guarantee_online_cpus() is called on each cpuset and removes all 
> CPUs, except CPU 0, from all cpusets.
> 
> I'm not quite sure about if/how this should be fixed in the kernel, 
> though. Looks like a very simple user-land workaround would be enough.
> 

Yeah.  Bug, surely.  But I guess it's always been there.

What are the implications of this for cpusets-via-containers?

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