linux-kernel - Re: [PATCH 2/2] mm,migration: Avoid race between shift_arg_pages() and rmap_walk() during migration by not migrating temporary stacks

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Date:	Sat, 1 May 2010 20:56:18 -0500 (CDT)
From:	Christoph Lameter <cl@...ux.com>
To:	Mel Gorman <mel@....ul.ie>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Linux-MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Minchan Kim <minchan.kim@...il.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Rik van Riel <riel@...hat.com>
Subject: Re: [PATCH 2/2] mm,migration: Avoid race between shift_arg_pages()
 and rmap_walk() during migration by not migrating temporary stacks

On Thu, 29 Apr 2010, Mel Gorman wrote:

> There is a race between shift_arg_pages and migration that triggers this bug.
> A temporary stack is setup during exec and later moved. If migration moves
> a page in the temporary stack and the VMA is then removed before migration
> completes, the migration PTE may not be found leading to a BUG when the
> stack is faulted.

A simpler solution would be to not allow migration of the temporary stack?

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