From owner-freebsd-stable@FreeBSD.ORG Mon Jun 26 13:32:48 2006 Return-Path: X-Original-To: freebsd-stable@freebsd.org Delivered-To: freebsd-stable@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 645BB16A400; Mon, 26 Jun 2006 13:32:48 +0000 (UTC) (envelope-from gavin.atkinson@ury.york.ac.uk) Received: from mail-gw4.york.ac.uk (mail-gw4.york.ac.uk [144.32.128.249]) by mx1.FreeBSD.org (Postfix) with ESMTP id E340043D72; Mon, 26 Jun 2006 13:32:41 +0000 (GMT) (envelope-from gavin.atkinson@ury.york.ac.uk) Received: from buffy.york.ac.uk (buffy-128.york.ac.uk [144.32.128.160]) by mail-gw4.york.ac.uk (8.13.6/8.13.6) with ESMTP id k5QDWce4003788; Mon, 26 Jun 2006 14:32:38 +0100 (BST) Received: from buffy.york.ac.uk (localhost [127.0.0.1]) by buffy.york.ac.uk (8.13.6/8.13.6) with ESMTP id k5QDWbhP081309; Mon, 26 Jun 2006 14:32:37 +0100 (BST) (envelope-from gavin.atkinson@ury.york.ac.uk) Received: (from ga9@localhost) by buffy.york.ac.uk (8.13.6/8.13.6/Submit) id k5QDWZfK081308; Mon, 26 Jun 2006 14:32:35 +0100 (BST) (envelope-from gavin.atkinson@ury.york.ac.uk) X-Authentication-Warning: buffy.york.ac.uk: ga9 set sender to gavin.atkinson@ury.york.ac.uk using -f From: Gavin Atkinson To: Martin Blapp In-Reply-To: <20060626151138.C14714@godot.imp.ch> References: <20060621202508.S17514@godot.imp.ch> <20060623133915.S14714@godot.imp.ch> <1151078632.62769.30.camel@buffy.york.ac.uk> <200606231928.58063.max@love2party.net> <20060626115110.O14714@godot.imp.ch> <20060626133540.G14714@godot.imp.ch> <20060626151138.C14714@godot.imp.ch> Content-Type: text/plain Content-Transfer-Encoding: 7bit Date: Mon, 26 Jun 2006 14:32:35 +0100 Message-Id: <1151328755.80434.17.camel@buffy.york.ac.uk> Mime-Version: 1.0 X-Mailer: Evolution 2.6.1 FreeBSD GNOME Team Port X-York-MailScanner: Found to be clean X-York-MailScanner-From: gavin.atkinson@ury.york.ac.uk Cc: freebsd-stable@freebsd.org, "Wojciech A. Koszek" , csjp@freebsd.org, Robert Watson , Max Laier , Patrick Guelat Subject: Re: Crash with FreeBSD 6.1 STABLE of today X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 26 Jun 2006 13:32:48 -0000 On Mon, 2006-06-26 at 15:15 +0200, Martin Blapp wrote: > A remote stress testing of a tty session over serial cable > with a patched kernel worked fine. > > How to proceed now ? The patch also applies to CURRENT > as there where no big changes since the repo has been > branched. > > Should I commit it to CURRENT ? > > > http://mx.imp.ch/patch-tty.t_pgrp.diff I'm still not convinced that the proctree lock is the correct lock to use - maybe a new lock for the tty subsystem? Also, some of the locking in the patch appears to be unnecessary. I can't help feeling that this patch is the heavy-handed solution to the problem, and given how heavyweight locks can be, maybe it's not a good solution. Is the problem actually understood? Do we know what's racing with what? Given there only ever seems to be a single backtrace involved, as far as I can tell, it's ttymodem racing with tty_close - can those two functions alone be locked? Alas, I can't recreate the problem on-demand so can't really find a better solution. Gavin