linux-kernel - Re: cpuset trouble after hibernate

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Message-ID: <Pine.LNX.4.64.0709101141180.3467@frecb006381.adech.frec.bull.fr>
Date:	Mon, 10 Sep 2007 11:45:10 +0200 (CEST)
From:	Simon Derr <Simon.Derr@...l.net>
To:	Nicolas Capit <nicolas.capit@...g.fr>
Cc:	linux-kernel@...r.kernel.org, Paul Jackson <pj@....com>
Subject: Re: cpuset trouble after hibernate

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.

	Simon.

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