linux-kernel - Re: cpuset trouble after hibernate

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Message-ID: <46EEC359.8070508@linux.vnet.ibm.com>
Date:	Mon, 17 Sep 2007 23:41:37 +0530
From:	Balbir Singh <balbir@...ux.vnet.ibm.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	Simon Derr <Simon.Derr@...l.net>,
	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

Andrew Morton wrote:
> 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?
> 

I suspect the functionality of cpusets is not affected by containers.

I wonder if containers should become suspend/resume aware and pass
that option on to controllers. I think it's only the bus drivers
and device drivers that do that now.



-- 
	Warm Regards,
	Balbir Singh
	Linux Technology Center
	IBM, ISTL
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