linux-kernel - Re: [PATCH] cpuset: mm: Remove memory barrier damage from the page allocator

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Message-ID: <1330723262.11248.233.camel@twins>
Date:	Fri, 02 Mar 2012 22:21:02 +0100
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Mel Gorman <mgorman@...e.de>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Miao Xie <miaox@...fujitsu.com>,
	Christoph Lameter <cl@...ux.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] cpuset: mm: Remove memory barrier damage from the page
 allocator

On Fri, 2012-03-02 at 11:23 +0000, Mel Gorman wrote:
> For extra style points, the commit introduced the use of yield() in an
> implementation of what looks like a spinning mutex.

Andrew, could you simply say no to any patch adding a yield()? There's a
99% chance its a bug, as was this. 

This code would life-lock when cpuset_change_task_nodemask() would be
called by the highest priority FIFO task on UP or when pinned to the
same cpu the task doing get_mems_allowed().
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