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 SMTP id 23E436B01EE for ; Mon, 26 Apr 2010 05:48:44 -0400 (EDT) Received: by iwn30 with SMTP id 30so1366407iwn.28 for ; Mon, 26 Apr 2010 02:48:42 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <20100426182838.2cab9844.kamezawa.hiroyu@jp.fujitsu.com> References: <20100423120148.9ffa5881.kamezawa.hiroyu@jp.fujitsu.com> <20100423095922.GJ30306@csn.ul.ie> <20100423155801.GA14351@csn.ul.ie> <20100424110200.b491ec5f.kamezawa.hiroyu@jp.fujitsu.com> <20100424104324.GD14351@csn.ul.ie> <20100426084901.15c09a29.kamezawa.hiroyu@jp.fujitsu.com> <20100426182838.2cab9844.kamezawa.hiroyu@jp.fujitsu.com> Date: Mon, 26 Apr 2010 18:48:42 +0900 Message-ID: Subject: Re: [BUGFIX][mm][PATCH] fix migration race in rmap_walk From: Minchan Kim Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org To: KAMEZAWA Hiroyuki Cc: Mel Gorman , "linux-mm@kvack.org" , Christoph Lameter , "akpm@linux-foundation.org" , "linux-kernel@vger.kernel.org" List-ID: On Mon, Apr 26, 2010 at 6:28 PM, KAMEZAWA Hiroyuki wrote: > On Mon, 26 Apr 2010 08:49:01 +0900 > KAMEZAWA Hiroyuki wrote: > >> On Sat, 24 Apr 2010 11:43:24 +0100 >> Mel Gorman wrote: > >> > It looks nice but it still broke after 28 hours of running. The >> > seq-counter is still insufficient to catch all changes that are made t= o >> > the list. I'm beginning to wonder if a) this really can be fully safel= y >> > locked with the anon_vma changes and b) if it has to be a spinlock to >> > catch the majority of cases but still a lazy cleanup if there happens = to >> > be a race. It's unsatisfactory and I'm expecting I'll either have some >> > insight to the new anon_vma changes that allow it to be locked or Rik >> > knows how to restore the original behaviour which as Andrea pointed ou= t >> > was safe. >> > >> Ouch. > > Ok, reproduced. Here is status in my test + printk(). > > =C2=A0* A race doesn't seem to happen if swap=3Doff. > =C2=A0 =C2=A0I need to swapon to cause the bug FYI, Do you have a swapon/off bomb test? When I saw your mail, I feel it might be culprit. http://lkml.org/lkml/2010/4/22/762. It is just guessing. I don't have a time to look into, now. --=20 Kind regards, Minchan Kim -- 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