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Date: Wed, 28 Apr 2010 00:32:42 +0200 From: Andrea Arcangeli <aarcange@...hat.com> To: Christoph Lameter <cl@...ux.com> Cc: Mel Gorman <mel@....ul.ie>, Linux-MM <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>, Minchan Kim <minchan.kim@...il.com>, KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>, Rik van Riel <riel@...hat.com>, Andrew Morton <akpm@...ux-foundation.org> Subject: Re: [PATCH 0/3] Fix migration races in rmap_walk() V2 On Tue, Apr 27, 2010 at 05:27:36PM -0500, Christoph Lameter wrote: > Can we simply wait like in the fault path? There is no bug there, no need to wait either. I already audited it before, and I didn't see any bug. Unless you can show a bug with CPU A running the rmap_walk on process1 before process2, there is no bug to fix there. > > > Patch 3 notes that while a VMA is moved under the anon_vma lock, the page > > tables are not similarly protected. Where migration PTEs are > > encountered, they are cleaned up. > > This means they are copied / moved etc and "cleaned" up in a state when > the page was unlocked. Migration entries are not supposed to exist when > a page is not locked. patch 3 is real, and the first thought I had was to lock down the page before running vma_adjust and unlock after move_page_tables. But these are virtual addresses. Maybe there's a simpler way to keep migration away while we run those two operations. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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