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

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Message-ID: <20070307122117.GB2336@in.ibm.com>
Date:	Wed, 7 Mar 2007 17:51:17 +0530
From:	Srivatsa Vaddagiri <vatsa@...ibm.com>
To:	menage@...gle.com
Cc:	akpm@...l.org, pj@....com, sekharan@...ibm.com, dev@...ru,
	xemul@...ru, serue@...ibm.com, ebiederm@...ssion.com,
	ckrm-tech@...ts.sourceforge.net, linux-kernel@...r.kernel.org,
	rohitseth@...gle.com, mbligh@...gle.com, winget@...gle.com,
	containers@...ts.osdl.org, devel@...nvz.org
Subject: Re: [PATCH 1/7] containers (V7): Generic container system abstracted from cpusets code

On Mon, Feb 12, 2007 at 12:15:22AM -0800, menage@...gle.com wrote:
> +/**
> + * container_lock - lock out any changes to container structures
> + *
> + * The out of memory (oom) code needs to mutex_lock containers
> + * from being changed while it scans the tasklist looking for a
> + * task in an overlapping container.

Which specific portion of oom code cares abt container structure being
intact? 

If I understand correctly, only cpuset requires this double locking.
More specifically, cpusets cares about walking cpuset->parent list
safely with callback_mutex held correct?

If that is the case, I think we can push container_lock entirely inside 
cpuset.c and not have others exposed to this double-lock complexity.
This is possible because cpuset.c (build on top of containers) still has
cpuset->parent and walking cpuset->parent list safely can be made
possible with a second lock which is local to only cpuset.c.

-- 
Regards,
vatsa
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