From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail138.messagelabs.com (mail138.messagelabs.com [216.82.249.35]) by kanga.kvack.org (Postfix) with SMTP id 13A756B0251 for ; Mon, 10 May 2010 13:41:42 -0400 (EDT) Date: Mon, 10 May 2010 12:41:07 -0500 (CDT) From: Christoph Lameter Subject: Re: [PATCH 2/2] mm,migration: Avoid race between shift_arg_pages() and rmap_walk() during migration by not migrating temporary stacks In-Reply-To: <20100504094522.GA20979@csn.ul.ie> Message-ID: References: <1272529930-29505-1-git-send-email-mel@csn.ul.ie> <1272529930-29505-3-git-send-email-mel@csn.ul.ie> <20100504094522.GA20979@csn.ul.ie> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org To: Mel Gorman Cc: Andrew Morton , Linux-MM , LKML , Minchan Kim , KAMEZAWA Hiroyuki , Andrea Arcangeli , Rik van Riel List-ID: On Tue, 4 May 2010, Mel Gorman wrote: > On Sat, May 01, 2010 at 08:56:18PM -0500, Christoph Lameter wrote: > > 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? > > > > The patch's intention is to not migrate pages within the temporary > stack. What are you suggesting that is different? A simple way to disallow migration of pages is to increment the refcount of a page. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org