linux-kernel - Re: [ckrm-tech] [PATCH 1/7] containers (V7): Generic container system abstracted from cpusets code

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Message-ID: <20070325050507.GG11794@in.ibm.com>
Date:	Sun, 25 Mar 2007 10:35:07 +0530
From:	Srivatsa Vaddagiri <vatsa@...ibm.com>
To:	Paul Jackson <pj@....com>
Cc:	sekharan@...ibm.com, ckrm-tech@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org, xemul@...ru, dev@...ru,
	rohitseth@...gle.com, ebiederm@...ssion.com, mbligh@...gle.com,
	winget@...gle.com, containers@...ts.osdl.org, serue@...ibm.com,
	menage@...gle.com, devel@...nvz.org
Subject: Re: [ckrm-tech] [PATCH 1/7] containers (V7): Generic container system abstracted from cpusets code

On Sat, Mar 24, 2007 at 09:45:50PM -0700, Paul Jackson wrote:
> Nice work - thanks.  Yes, both an extra cpuset count and a negative
> cpuset count are bad news, opening the door to the usual catastrophes.
> 
> Would you like the honor of submitting the patch to add a task_lock
> to cpuset_exit()?  If you do, be sure to fix, or at least remove,
> the cpuset_exit comment lines:

I will try to send out a patch later today to fix this bug in mainline
cpuset code. I happened to notice this race with my rcfs patch and observed 
same is true with cpuset/container code also.

>  * We don't need to task_lock() this reference to tsk->cpuset,
>  * because tsk is already marked PF_EXITING, so attach_task() won't
>  * mess with it, or task is a failed fork, never visible to attach_task.

Sure, I had seen that.

> So, in real life, this would be a difficult race to trigger.

Agreed, but good to keep code clean isn't it? :)

> Thanks for finding this.

Wellcome!

-- 
Regards,
vatsa
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