linux-kernel - Re: [PATCHSET] stop_machine: implement stop_machine_from_offline

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Message-ID: <20110616121505.GB2611@htj.dyndns.org>
Date:	Thu, 16 Jun 2011 14:15:05 +0200
From:	Tejun Heo <tj@...nel.org>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	x86@...nel.org, mingo@...e.hu, akpm@...ux-foundation.org,
	torvalds@...ux-foundation.org, suresh.b.siddha@...el.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCHSET] stop_machine: implement
 stop_machine_from_offline_cpu()

Hello, Peter.

On Thu, Jun 16, 2011 at 02:10:19PM +0200, Peter Zijlstra wrote:
> Maybe a silly question, but why does mtrr need all this? Surely mtrr can
> serialize state by other means than stopping all cpus. A simple mutex
> around the shared state blocking other cpus from updating the mtrr state
> while we're copying the state to our newly born cpu should cure things.

Hmmm... good question.  I don't know mtrr too well either but the
stop-machine requirement seems to directly come from intel's
specification.  I suppose Suresh can fill us in better.

Thanks.

-- 
tejun
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