From owner-freebsd-current@FreeBSD.ORG  Fri Dec 12 10:41:02 2008
Return-Path: <owner-freebsd-current@FreeBSD.ORG>
Delivered-To: current@freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34])
	by hub.freebsd.org (Postfix) with ESMTP id 6D8F41065676
	for <current@freebsd.org>; Fri, 12 Dec 2008 10:41:02 +0000 (UTC)
	(envelope-from rwatson@FreeBSD.org)
Received: from cyrus.watson.org (cyrus.watson.org [65.122.17.42])
	by mx1.freebsd.org (Postfix) with ESMTP id 48C2D8FC16
	for <current@freebsd.org>; Fri, 12 Dec 2008 10:41:02 +0000 (UTC)
	(envelope-from rwatson@FreeBSD.org)
Received: from fledge.watson.org (fledge.watson.org [65.122.17.41])
	by cyrus.watson.org (Postfix) with ESMTP id E0A6246B64;
	Fri, 12 Dec 2008 05:41:01 -0500 (EST)
Date: Fri, 12 Dec 2008 10:41:01 +0000 (GMT)
From: Robert Watson <rwatson@FreeBSD.org>
X-X-Sender: robert@fledge.watson.org
To: Bartosz Stec <admin@kkip.pl>
In-Reply-To: <49423E5A.10900@kkip.pl>
Message-ID: <alpine.BSF.1.10.0812121039180.41885@fledge.watson.org>
References: <4940A685.7040608@psg.com> <494216C2.7080606@kkip.pl>
	<20081212095238.GY2038@deviant.kiev.zoral.com.ua>
	<49423E5A.10900@kkip.pl>
User-Agent: Alpine 1.10 (BSF 962 2008-03-14)
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed
Cc: Kostik Belousov <kostikbel@gmail.com>, Randy Bush <randy@psg.com>,
	FreeBSD Current <current@freebsd.org>
Subject: Re: panic: sleeping thread & bufwrite: buffer is not busy???
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: Fri, 12 Dec 2008 10:41:02 -0000


On Fri, 12 Dec 2008, Bartosz Stec wrote:

> OK. I'll try to build debug kernel today and I will provide backtrace. I 
> forgot to mention in my last post that I saw very similiar (if not 
> identical) lines to:
>
>   Sleeping thread (tid 100054, pid 646) owns a non-sleepable lock
>   panic: sleeping thread
>   panic: bufwrite: buffer is not busy???
>
> while checking dmesg buffer after one of the panics earlier. That's why I 
> assumed it's probably the same issue. Sorry for confusion, they're my first 
> steps with CURRENT and very first experience with kernel panic :).

Yeah, secondary panics can significantly complicate the debugging process, 
unfortunately.  Another similar class of confusing cases exist when panics 
occur and are then preempted during the panic by another thread that promptly 
trips over state left behind by the first thread, and panics. :-)

Robert N M Watson
Computer Laboratory
University of Cambridge