From owner-freebsd-arch@FreeBSD.ORG Fri Oct 1 11:08:21 2004 Return-Path: Delivered-To: freebsd-arch@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 9E74A16A4CE for ; Fri, 1 Oct 2004 11:08:21 +0000 (GMT) Received: from relay.pair.com (relay.pair.com [209.68.1.20]) by mx1.FreeBSD.org (Postfix) with SMTP id 0B9E743D46 for ; Fri, 1 Oct 2004 11:08:21 +0000 (GMT) (envelope-from pho@holm.cc) Received: (qmail 61626 invoked from network); 1 Oct 2004 11:08:19 -0000 Received: from 0x50a43fc7.hknxx1.adsl-dhcp.tele.dk (HELO peter.osted.lan) (80.164.63.199) by relay.pair.com with SMTP; 1 Oct 2004 11:08:19 -0000 X-pair-Authenticated: 80.164.63.199 Received: from peter.osted.lan (localhost.osted.lan [127.0.0.1]) by peter.osted.lan (8.12.10/8.12.10) with ESMTP id i91B8ICs058177; Fri, 1 Oct 2004 13:08:18 +0200 (CEST) (envelope-from pho@peter.osted.lan) Received: (from pho@localhost) by peter.osted.lan (8.12.10/8.12.10/Submit) id i91B8HOt058176; Fri, 1 Oct 2004 13:08:17 +0200 (CEST) (envelope-from pho) Date: Fri, 1 Oct 2004 13:08:17 +0200 From: Peter Holm To: Stephan Uphoff Message-ID: <20041001110817.GA58111@peter.osted.lan> References: <1095468747.31297.241.camel@palm.tree.com> <1096477932.3733.1471.camel@palm.tree.com> <1096489576.3733.1868.camel@palm.tree.com> <200409291652.29990.jhb@FreeBSD.org> <1096496057.3733.2163.camel@palm.tree.com> <1096603981.21577.195.camel@palm.tree.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1096603981.21577.195.camel@palm.tree.com> User-Agent: Mutt/1.4.1i cc: Peter Holm cc: Julian Elischer cc: John Baldwin cc: "freebsd-arch@freebsd.org" Subject: Re: scheduler (sched_4bsd) questions X-BeenThere: freebsd-arch@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Discussion related to FreeBSD architecture List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 01 Oct 2004 11:08:21 -0000 On Fri, Oct 01, 2004 at 12:13:01AM -0400, Stephan Uphoff wrote: > On Wed, 2004-09-29 at 18:14, Stephan Uphoff wrote: > > I was looking at the MUTEX_WAKE_ALL undefined case when I used the > > critical section for turnstile_claim(). > > However there are bigger problems with MUTEX_WAKE_ALL undefined > > so you are right - the critical section for turnstile_claim is pretty > > useless. > > Arghhh !!! > > MUTEX_WAKE_ALL is NOT an option in GENERIC. > I recall verifying that it is defined twice. Guess I must have looked at > the wrong source tree :-( > This means yes - we have bigger problems! > > Example: > > Thread A holds a mutex x contested by Thread B and C and has priority > pri(A). > > Thread C holds a mutex y and pri(B) < pri(C) > > Thread A releases the lock wakes thread B but lets C on the turnstile > wait queue. > > An interrupt thread I tries to lock mutex y owned by C. > > However priority inheritance does not work since B needs to run first to > take ownership of the lock. > > I is blocked :-( > > This was found using Peter Holm's test and a slight modification of this > giant hog detector. (kern_clock.diff) > > I definitely won't have time to fix kern_mutex.c for the next few days > so please add the line: > > options MUTEX_WAKE_ALL # Needed do not remove > I like to test one thing at a time, so I added MUTEX_WAKE_ALL to HEAD from Sep 30 09:58 UTC. This did not seem to change any thing :-( I'll proceed with adding your switch_patch_v2 patch + your sched_4bsd.c patch, but without MUTEX_WAKE_ALL. - Peter > to your configuration files. > > I also had overlooked > http://www.holm.cc/stress/log/cons80.html > Showing that my patch for kern_switch.c (switch_patch) has a bug. > I will send an updated patch later today. > > Stephan > > PS: I love the firewire debugging speed! -- Peter Holm