From owner-freebsd-bugs@FreeBSD.ORG  Wed Sep  1 18:20:03 2010
Return-Path: <owner-freebsd-bugs@FreeBSD.ORG>
Delivered-To: freebsd-bugs@hub.freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34])
	by hub.freebsd.org (Postfix) with ESMTP id 1A1581065695
	for <freebsd-bugs@hub.freebsd.org>;
	Wed,  1 Sep 2010 18:20:03 +0000 (UTC)
	(envelope-from gnats@FreeBSD.org)
Received: from freefall.freebsd.org (freefall.freebsd.org
	[IPv6:2001:4f8:fff6::28])
	by mx1.freebsd.org (Postfix) with ESMTP id 09ACF8FC18
	for <freebsd-bugs@hub.freebsd.org>;
	Wed,  1 Sep 2010 18:20:03 +0000 (UTC)
Received: from freefall.freebsd.org (localhost [127.0.0.1])
	by freefall.freebsd.org (8.14.4/8.14.4) with ESMTP id o81IK2Ft047566
	for <freebsd-bugs@freefall.freebsd.org>; Wed, 1 Sep 2010 18:20:02 GMT
	(envelope-from gnats@freefall.freebsd.org)
Received: (from gnats@localhost)
	by freefall.freebsd.org (8.14.4/8.14.4/Submit) id o81IK2S9047565;
	Wed, 1 Sep 2010 18:20:02 GMT (envelope-from gnats)
Date: Wed, 1 Sep 2010 18:20:02 GMT
Message-Id: <201009011820.o81IK2S9047565@freefall.freebsd.org>
To: freebsd-bugs@FreeBSD.org
From: mdf@FreeBSD.org
Cc: 
Subject: Re: kern/133289: [vm] [panic] DEBUG_MEMGUARD with
 vm.memguard.desc="devbuf" panics the kernel
X-BeenThere: freebsd-bugs@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
Reply-To: mdf@FreeBSD.org
List-Id: Bug reports <freebsd-bugs.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-bugs>,
	<mailto:freebsd-bugs-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-bugs>
List-Post: <mailto:freebsd-bugs@freebsd.org>
List-Help: <mailto:freebsd-bugs-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-bugs>,
	<mailto:freebsd-bugs-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Wed, 01 Sep 2010 18:20:03 -0000

The following reply was made to PR kern/133289; it has been noted by GNATS.

From: mdf@FreeBSD.org
To: bug-followup@FreeBSD.org, 20080101.freebsd.org@ab.ote.we.lv
Cc:  
Subject: Re: kern/133289: [vm] [panic] DEBUG_MEMGUARD with vm.memguard.desc="devbuf"
 panics the kernel
Date: Wed, 1 Sep 2010 10:54:14 -0700

 Based on the stack trace it looks like mgfifo is NULL (the lines are
 off by one, it appears, but that's the only reasonable place to
 dereference 0x8).
 
 This did not repro on a virtual machine for me.  However, there is a
 new memguard implementation in -current now.  I am unable to determine
 conclusively from just the stack whether this is a bug in memguard or
 if memguard found a bug in the use of M_DEVBUF but didn't print an
 error in a friendly format.
 
 Would it be possible to re-try this on the same hardware, but using
 CURRENT?  If not, I hope to backport the memguard changes in a few
 weeks to stable/8 and stable/7.
 
 Thanks,
 matthew