Date: Tue, 17 Jun 2008 18:15:27 +0900
From: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
To: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Andrew Morton <akpm@linux-foundation.org>, Rik van Riel <riel@redhat.com>,
       Lee Schermerhorn <lee.schermerhorn@hp.com>,
       Kosaki Motohiro <kosaki.motohiro@jp.fujitsu.com>,
       Nick Piggin <npiggin@suse.de>, linux-mm@kvack.org,
       linux-kernel@vger.kernel.org, kernel-testers@vger.kernel.org
Subject: Re: [Bad page] trying to free locked page? (Re: [PATCH][RFC] fix
 kernel BUG at mm/migrate.c:719! in 2.6.26-rc5-mm3)
Message-Id: <20080617181527.5bcbbccc.nishimura@mxp.nes.nec.co.jp>
In-Reply-To: <20080617180314.2d1b0efa.kamezawa.hiroyu@jp.fujitsu.com>
References: <20080611225945.4da7bb7f.akpm@linux-foundation.org>
	<20080617163501.7cf411ee.nishimura@mxp.nes.nec.co.jp>
	<20080617164709.de4db070.nishimura@mxp.nes.nec.co.jp>
	<20080617180314.2d1b0efa.kamezawa.hiroyu@jp.fujitsu.com>
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On Tue, 17 Jun 2008 18:03:14 +0900, KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:
> On Tue, 17 Jun 2008 16:47:09 +0900
> Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> wrote:
> 
> > On Tue, 17 Jun 2008 16:35:01 +0900, Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> wrote:
> > > Hi.
> > > 
> > > I got this bug while migrating pages only a few times
> > > via memory_migrate of cpuset.
> > > 
> > > Unfortunately, even if this patch is applied,
> > > I got bad_page problem after hundreds times of page migration
> > > (I'll report it in another mail).
> > > But I believe something like this patch is needed anyway.
> > > 
> > 
> > I got bad_page after hundreds times of page migration.
> > It seems that a locked page is being freed.
> > 
> Good catch, and I think your investigation in the last e-mail was correct.
> I'd like to dig this...but it seems some kind of big fix is necessary.
> Did this happen under page-migraion by cpuset-task-move test ?
> 
Yes.

I made 2 cpuset directories, run some processes in each cpusets,
and run a script like below infinitely to move tasks and migrate pages.

---
#!/bin/bash

G1=$1
G2=$2

move_task()
{
        for pid in $1
        do
                echo $pid >$2/tasks 2>/dev/null
        done
}

G1_TASK=`cat ${G1}/tasks`
G2_TASK=`cat ${G2}/tasks`

move_task "${G1_TASK}" ${G2} &
move_task "${G2_TASK}" ${G1} &

wait
---

I got this bad_page after running this script for about 600 times.


Thanks,
Daisuke Nishimura.


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