From owner-freebsd-hackers@FreeBSD.ORG  Sun Nov 25 12:38:10 2012
Return-Path: <owner-freebsd-hackers@FreeBSD.ORG>
Delivered-To: freebsd-hackers@freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52])
 by hub.freebsd.org (Postfix) with ESMTP id A3272E3B;
 Sun, 25 Nov 2012 12:38:10 +0000 (UTC)
 (envelope-from pawel@dawidek.net)
Received: from mail.dawidek.net (garage.dawidek.net [91.121.88.72])
 by mx1.freebsd.org (Postfix) with ESMTP id 5CB6F8FC19;
 Sun, 25 Nov 2012 12:38:09 +0000 (UTC)
Received: from localhost (89-73-195-149.dynamic.chello.pl [89.73.195.149])
 by mail.dawidek.net (Postfix) with ESMTPSA id 19DBAC33;
 Sun, 25 Nov 2012 13:36:21 +0100 (CET)
Date: Sun, 25 Nov 2012 13:39:21 +0100
From: Pawel Jakub Dawidek <pjd@FreeBSD.org>
To: Attilio Rao <attilio@freebsd.org>
Subject: Re: [RFQ] make witness panic an option
Message-ID: <20121125123920.GI1460@garage.freebsd.pl>
References: <CAJ-Vmo=i=Amo_QqHi4GnGie0Gc0YnK3XaRKjvBO-=SFboFYPmA@mail.gmail.com>
 <CACfq090EiEiG7Ou2ZMUafWN6GLT9RNK1Q4tiOHnOBWe8GYJDjA@mail.gmail.com>
 <CAJ-VmonE3myRyeZ+Ae0ZOXf7wKvC44rRVkFfDaEwnk8C-=5uoA@mail.gmail.com>
 <CAJ-FndCZPand_rx_uXUeetGMUZu1syGwjdFS7jv9BwdzuXvXOA@mail.gmail.com>
MIME-Version: 1.0
Content-Type: multipart/signed; micalg=pgp-sha1;
 protocol="application/pgp-signature"; boundary="EdRE1UL8d3mMOE6m"
Content-Disposition: inline
In-Reply-To: <CAJ-FndCZPand_rx_uXUeetGMUZu1syGwjdFS7jv9BwdzuXvXOA@mail.gmail.com>
X-OS: FreeBSD 10.0-CURRENT amd64
User-Agent: Mutt/1.5.21 (2010-09-15)
Cc: "freebsd-hackers@freebsd.org" <freebsd-hackers@freebsd.org>,
 Adrian Chadd <adrian@freebsd.org>,
 Giovanni Trematerra <giovanni.trematerra@gmail.com>, freebsd-arch@freebsd.org
X-BeenThere: freebsd-hackers@freebsd.org
X-Mailman-Version: 2.1.14
Precedence: list
List-Id: Technical Discussions relating to FreeBSD
 <freebsd-hackers.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/options/freebsd-hackers>, 
 <mailto:freebsd-hackers-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-hackers>
List-Post: <mailto:freebsd-hackers@freebsd.org>
List-Help: <mailto:freebsd-hackers-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-hackers>,
 <mailto:freebsd-hackers-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Sun, 25 Nov 2012 12:38:10 -0000


--EdRE1UL8d3mMOE6m
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
Content-Transfer-Encoding: quoted-printable

On Thu, Nov 15, 2012 at 04:39:55PM +0000, Attilio Rao wrote:
> On 11/15/12, Adrian Chadd <adrian@freebsd.org> wrote:
> > On 15 November 2012 05:27, Giovanni Trematerra
> > <giovanni.trematerra@gmail.com> wrote:
> >
> >> I really do think that is a very bad idea.
> >> When a locking assertion fails you have just to stop your mind and
> >> think what's wrong,
> >> no way to postpone on this.
> >
> > Not all witness panics are actually fatal. For a developer who is
> > sufficiently cluey in their area, they are quite likely able to just
> > stare at the code paths for a while to figure out why the
> > incorrectness occured.
>=20
> The problem is that such mechanism can be abused, just like the
> BLESSING one and that's why this is disabled by default.

WITNESS is a development tool. We don't ship production kernels with
WITNESS even compiled in. What is more efficient use of developer time:
going through full reboot cycle every time or reading the warning from
console, unloading a module, fixing the bug and loading it again?

And if this option is turned off by default what is the problem?

--=20
Pawel Jakub Dawidek                       http://www.wheelsystems.com
FreeBSD committer                         http://www.FreeBSD.org
Am I Evil? Yes, I Am!                     http://tupytaj.pl

--EdRE1UL8d3mMOE6m
Content-Type: application/pgp-signature

-----BEGIN PGP SIGNATURE-----
Version: GnuPG v2.0.19 (FreeBSD)

iEYEARECAAYFAlCyEXgACgkQForvXbEpPzRdpwCbBmzAAu4KdDaHCcDdEr/xq5SE
HDwAoMpyO7TPU8jPupmwrg1EgSJXLljn
=gpTY
-----END PGP SIGNATURE-----

--EdRE1UL8d3mMOE6m--