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Date:	Tue, 11 May 2010 13:21:16 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	Mel Gorman <mel@....ul.ie>,
	Andrew Morton <akpm@...ux-foundation.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Linux-MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Minchan Kim <minchan.kim@...il.com>,
	Christoph Lameter <cl@...ux.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH] mm,migration: Avoid race between shift_arg_pages() and
 rmap_walk() during migration by not migrating temporary stacks

On 05/11/2010 01:11 PM, Linus Torvalds wrote:
> On Tue, 11 May 2010, Mel Gorman wrote:
>>
>> This patch closes the most important race in relation to exec and
>> migration. With it applied, the swapops bug is no longer triggering for
>> known problem workloads. If you pick it up, it should go with the other
>> mmmigration-* fixes in mm.
>
> Ack. _Much_ better and clearer.
>
> I'm not entirely sure we need that "maybe_stack" (if we need it, that
> would sound like a problem anyway), but I guess it can't hurt either.

Just a heads up - I am looking at creating a patch now that
allows us to _always_ lock the root anon_vma lock, when locking
the anon_vma.

That should take care of the other issue pretty cleanly, while
still allowing us to only walk the VMAs we have to walk in
places like rmap_walk.

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