From owner-freebsd-current@FreeBSD.ORG  Wed May 23 13:50:38 2012
Return-Path: <owner-freebsd-current@FreeBSD.ORG>
Delivered-To: freebsd-current@freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52])
	by hub.freebsd.org (Postfix) with ESMTP id 8A68F1065741
	for <freebsd-current@freebsd.org>; Wed, 23 May 2012 13:50:38 +0000 (UTC)
	(envelope-from jhb@freebsd.org)
Received: from bigwig.baldwin.cx (bigknife-pt.tunnel.tserv9.chi1.ipv6.he.net
	[IPv6:2001:470:1f10:75::2])
	by mx1.freebsd.org (Postfix) with ESMTP id 607A78FC12
	for <freebsd-current@freebsd.org>; Wed, 23 May 2012 13:50:38 +0000 (UTC)
Received: from jhbbsd.localnet (unknown [209.249.190.124])
	by bigwig.baldwin.cx (Postfix) with ESMTPSA id BBE1FB9AD;
	Wed, 23 May 2012 09:50:37 -0400 (EDT)
From: John Baldwin <jhb@freebsd.org>
To: Ian FREISLICH <ianf@clue.co.za>
Date: Wed, 23 May 2012 09:50:36 -0400
User-Agent: KMail/1.13.5 (FreeBSD/8.2-CBSD-20110714-p13; KDE/4.5.5; amd64; ; )
References: <201205230930.03282.jhb@freebsd.org>
	<E1SX3Bt-0000qb-JF@clue.co.za> <E1SXBpO-0001ep-Ei@clue.co.za>
In-Reply-To: <E1SXBpO-0001ep-Ei@clue.co.za>
MIME-Version: 1.0
Content-Type: Text/Plain;
  charset="iso-8859-15"
Content-Transfer-Encoding: 7bit
Message-Id: <201205230950.36450.jhb@freebsd.org>
X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.2.7
	(bigwig.baldwin.cx); Wed, 23 May 2012 09:50:37 -0400 (EDT)
Cc: freebsd-current@freebsd.org
Subject: Re:
X-BeenThere: freebsd-current@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: Discussions about the use of FreeBSD-current
	<freebsd-current.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-current>, 
	<mailto:freebsd-current-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-current>
List-Post: <mailto:freebsd-current@freebsd.org>
List-Help: <mailto:freebsd-current-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-current>,
	<mailto:freebsd-current-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Wed, 23 May 2012 13:50:38 -0000

On Wednesday, May 23, 2012 9:42:14 am Ian FREISLICH wrote:
> John Baldwin wrote:
> > On Wednesday, May 23, 2012 12:28:53 am Ian FREISLICH wrote:
> > > (kgdb) frame 7
> > > #7  0xc0878682 in pmap_enter (pmap=0xc09e4060, va=3359633408, access=7 
'\a'
> , 
> > >     m=0xc191bf70, prot=7 '\a', wired=1) at 
> > /usr/src/sys/i386/i386/pmap.c:1596
> > > 1596                    root = vm_page_splay(mpte->pindex, root);
> > > (kgdb) l
> > > 1591            root = pmap->pm_root;
> > > 1592            if (root == NULL) {
> > > 1593                    mpte->left = NULL;
> > > 1594                    mpte->right = NULL;
> > > 1595            } else {
> > > 1596                    root = vm_page_splay(mpte->pindex, root);
> > > 1597                    if (mpte->pindex < root->pindex) {
> > > 1598                            mpte->left = root->left;
> > > 1599                            mpte->right = root;
> > > 1600                            root->left = NULL;
> > 
> > Ok, can you do 'p root', 'p mpte', and 'p *mpte'?
> 
> (kgdb) frame 7
> #7  0xc0878682 in pmap_enter (pmap=0xc09e4060, va=3359633408, access=7 '\a', 
>     m=0xc191bf70, prot=7 '\a', wired=1) at 
/usr/src/sys/i386/i386/pmap.c:1596
> 1596                    root = vm_page_splay(mpte->pindex, root);
> (kgdb) p root
> No symbol "root" in current context.
> (kgdb) p mpte
> $1 = 0x0
> (kgdb) p *mpte
> Cannot access memory at address 0x0

Well, mpte being NULL is the cause of your fault. :(  It also seems that the
system is trying to promote a superpage, but it can't find the page table
page that currently maps the individual pages that make up the superpage 
(which is odd).

-- 
John Baldwin