From owner-freebsd-stable@FreeBSD.ORG Sat Dec 30 18:52:24 2006 Return-Path: X-Original-To: freebsd-stable@freebsd.org Delivered-To: freebsd-stable@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id 2E80E16A407; Sat, 30 Dec 2006 18:52:24 +0000 (UTC) (envelope-from freebsd@orchid.homeunix.org) Received: from orchid.homeunix.org (aum95.neoplus.adsl.tpnet.pl [83.27.20.95]) by mx1.freebsd.org (Postfix) with ESMTP id 74ABD13C428; Sat, 30 Dec 2006 18:52:23 +0000 (UTC) (envelope-from freebsd@orchid.homeunix.org) Received: from blackacidevil.orchid.homeunix.org (blackacidevil.orchid.homeunix.org [192.168.1.66]) (authenticated bits=0) by orchid.homeunix.org (8.13.6/8.13.6) with ESMTP id kBUIqIlk022238 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NOT); Sat, 30 Dec 2006 19:52:21 +0100 (CET) (envelope-from freebsd@orchid.homeunix.org) Message-ID: <4596B55B.7080506@orchid.homeunix.org> Date: Sat, 30 Dec 2006 19:52:11 +0100 From: Karol Kwiatkowski User-Agent: Thunderbird 2.0b1 (X11/20061222) MIME-Version: 1.0 To: Robert Watson References: <20061230035722.L39715@thebighonker.lerctr.org> <20061230151933.P18740@fledge.watson.org> <20061230093730.I47579@thebighonker.lerctr.org> <20061230160353.K18740@fledge.watson.org> <45969487.1020806@orchid.homeunix.org> <20061230170358.K50974@fledge.watson.org> <4596AF32.2060205@orchid.homeunix.org> <20061230182714.O18740@fledge.watson.org> In-Reply-To: <20061230182714.O18740@fledge.watson.org> X-Enigmail-Version: 0.94.1.0 OpenPGP: id=06E09309; url=http://www.orchid.homeunix.org/carlos/gpg/0x06E09309.asc Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="------------enig684C0066F830AEE958763581" X-Virus-Scanned: ClamAV 0.88.7/2396/Sat Dec 30 12:57:43 2006 on orchid.homeunix.org X-Virus-Status: Clean Cc: freebsd-stable@freebsd.org Subject: Re: debugging kernel options X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list Reply-To: freebsd@orchid.homeunix.org List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 30 Dec 2006 18:52:24 -0000 This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enig684C0066F830AEE958763581 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Robert Watson wrote: >=20 > On Sat, 30 Dec 2006, Karol Kwiatkowski wrote: >=20 >> Robert Watson wrote: >>>> P.S. out of curiosity - now that I have configured kernel with DDB a= nd >>>> KDB options, is there any performance penalty of running such kernel= ? >>> >>> No, it shouldn't really have any effect on performance. The one >>> thing to watch out for is that your system will no longer reboot >>> automatically on a panic, as it will drop to the debugger, by >>> default. You can change this by setting debug.debugger_on_panic to >>> 0, in which case you will likely want to set debug.trace_on_panic to >>> 1 so it prints a stack trace before rebooting (which is often >>> sufficient, combined with the trap frame and panic message to debug >>> the problem). >>> >>> Right now these are sysctls, not tunables, but you can change the >>> default using options KDB_UNATTENDED (which flips the default to not >>> entering the debugger and rebooting) and options KDB_TRACE (which >>> causes a trace to be printed on panic by default). Probably they >>> should also be tunables so that loader.conf entries will work. >> >> Great explanation, thank you. I turned on debugging on my desktop >> computer which, apart from normal every day use, is 'testing' STABLE >> by running it :) I'm perfectly fine with the defaults, at least for no= w. >=20 > BTW, if you're running X on your desktop, be aware that it's X that doe= s > all the video mode management. If your box enters the debugger while i= n > X, the debugger doesn't know how to switch back to text mode (and X > isn't running, obviously), so while you'll be talking to the debugger, > the chances you'll see anything comprehensible are actually quite low. = > For this reason, I normally also use a serial console when debugging > desktop boxes: I can always plug my notebook in with a serial cable to > see why it's entered the debugger. Right, I haven't thought about that. I guess without a serial console my best option is to set debug.debugger_on_panic to 0, debug.trace_on_panic to 1 and keep crash dump with kernel.debug for later examination, isn't it? The whole point of doing this, as I am not really experienced in debugging, is to have the information saved somewhere in case of a panic.= Regards, Karol --=20 Karol Kwiatkowski OpenPGP: http://www.orchid.homeunix.org/carlos/gpg/0x06E09309.asc --------------enig684C0066F830AEE958763581 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.6 (FreeBSD) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iD8DBQFFlrViezeoPAwGIYsRCJ7iAJ0WhekN2ZzjCvoZfkcatgIpgsEZMwCfRFMD Y01GBkYoJgQ6sfOc5e1sNlk= =7f/I -----END PGP SIGNATURE----- --------------enig684C0066F830AEE958763581--