From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail172.messagelabs.com (mail172.messagelabs.com [216.82.254.3]) by kanga.kvack.org (Postfix) with ESMTP id 4AA416B01F6 for ; Wed, 28 Apr 2010 05:17:40 -0400 (EDT) Date: Wed, 28 Apr 2010 10:17:18 +0100 From: Mel Gorman Subject: Re: [PATCH 0/3] Fix migration races in rmap_walk() V2 Message-ID: <20100428091718.GC15815@csn.ul.ie> References: <1272403852-10479-1-git-send-email-mel@csn.ul.ie> <20100427223242.GG8860@random.random> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20100427223242.GG8860@random.random> Sender: owner-linux-mm@kvack.org To: Andrea Arcangeli Cc: Christoph Lameter , Linux-MM , LKML , Minchan Kim , KAMEZAWA Hiroyuki , Rik van Riel , Andrew Morton List-ID: On Wed, Apr 28, 2010 at 12:32:42AM +0200, Andrea Arcangeli wrote: > 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. > Yes, this patch is now dropped. > > > > > 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. > I see there is a large discussion on that patch so I'll read that rather than commenting here. -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab -- 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