From owner-freebsd-hackers  Fri Feb  8 17:16:40 2002
Delivered-To: freebsd-hackers@freebsd.org
Received: from mail.taconic.net (mail.taconic.net [205.231.144.5])
	by hub.freebsd.org (Postfix) with ESMTP id 3A4BB37B420
	for <freebsd-hackers@FreeBSD.ORG>; Fri,  8 Feb 2002 17:16:21 -0800 (PST)
Received: from coyotepoint.com ([205.231.27.66])
	by mail.taconic.net (8.10.2+Sun/8.11.4) with ESMTP id g191GEp14872
	for <freebsd-hackers@FreeBSD.ORG>; Fri, 8 Feb 2002 20:16:15 -0500 (EST)
Message-ID: <3C6478BE.BE6F5A70@coyotepoint.com>
Date: Fri, 08 Feb 2002 20:17:50 -0500
From: Bill Kish <kish@coyotepoint.com>
X-Mailer: Mozilla 4.79 [en] (WinNT; U)
X-Accept-Language: en
MIME-Version: 1.0
To: hackers <freebsd-hackers@FreeBSD.ORG>
Subject: Debugging double page fault
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Sender: owner-freebsd-hackers@FreeBSD.ORG
Precedence: bulk
List-ID: <freebsd-hackers.FreeBSD.ORG>
List-Archive: <http://docs.freebsd.org/mail/> (Web Archive)
List-Help: <mailto:majordomo@FreeBSD.ORG?subject=help> (List Instructions)
List-Subscribe: <mailto:majordomo@FreeBSD.ORG?subject=subscribe%20freebsd-hackers>
List-Unsubscribe: <mailto:majordomo@FreeBSD.ORG?subject=unsubscribe%20freebsd-hackers>
X-Loop: FreeBSD.ORG


Hi All,

 I've recently started seeing "double fault" panics on a formerly FreeBSD
2.2.8 based system (It's running 2.2.8 as a somewhat embedded OS, so please
don't flame me about being back rev!)

 The stack trace looks like:

$ gdb -k  kernel.0 vmcore.0
GDB is free software and you are welcome to distribute copies of it
 under certain conditions; type "show copying" to see the conditions.
There is absolutely no warranty for GDB; type "show warranty" for details.
GDB 4.16 (i386-unknown-freebsd),
Copyright 1996 Free Software Foundation, Inc...(no debugging symbols
found)...
IdlePTD 1aa000
current pcb at 1967a0
panic: double fault
#0  0xf010cf63 in boot ()
(kgdb) bt
#0  0xf010cf63 in boot ()
#1  0xf010d232 in panic ()
#2  0xf0176f5a in trap_fatal ()
#3  0xf0176a1c in trap_pfault ()
#4  0xf01766df in trap ()
#5  0xf012baae in vget ()
#6  0xf01558dc in ffs_sync ()
#7  0xf012cf7b in sync ()
#8  0xf010ce2d in boot ()
#9  0xf010d232 in panic ()
#10 0xf0176ff0 in trapwrite ()
(kgdb)

 My rough understanding is that double faults are usually the result of
running out of stack, and that the underlying cause of the panic can probably
be uncovered if I can find the previous stack .

 Can anyone point me towards some hints for debugging this sort of crash. Any
advice greatly appreciated.

                                        -=BK

To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe freebsd-hackers" in the body of the message