From owner-freebsd-current@FreeBSD.ORG  Wed Jun  9 15:04:53 2004
Return-Path: <owner-freebsd-current@FreeBSD.ORG>
Delivered-To: freebsd-current@freebsd.org
Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125])
	by hub.freebsd.org (Postfix) with ESMTP
	id 413BC16A4CE; Wed,  9 Jun 2004 15:04:53 +0000 (GMT)
Received: from hetzner.co.za (lfw.hetzner.co.za [196.7.18.226])
	by mx1.FreeBSD.org (Postfix) with ESMTP
	id CE1F543D5A; Wed,  9 Jun 2004 15:04:52 +0000 (GMT)
	(envelope-from ianf@hetzner.co.za)
Received: from localhost ([127.0.0.1])
	by hetzner.co.za with esmtp (Exim 3.36 #1)
	id 1BY4dE-000AOa-00; Wed, 09 Jun 2004 17:04:48 +0200
To: John Baldwin <jhb@FreeBSD.org>
From: Ian FREISLICH <if@hetzner.co.za>
In-Reply-To: Message from John Baldwin <jhb@FreeBSD.org> 
   of "Wed, 09 Jun 2004 10:27:43 -0400." <200406091027.43054.jhb@FreeBSD.org> 
Date: Wed, 09 Jun 2004 17:04:48 +0200
Sender: ianf@hetzner.co.za
Message-Id: <E1BY4dE-000AOa-00@hetzner.co.za>
cc: freebsd-current@FreeBSD.org
Subject: Re: panic: spin lock held too long (reasonable load) 
X-BeenThere: freebsd-current@freebsd.org
X-Mailman-Version: 2.1.1
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: Wed, 09 Jun 2004 15:04:53 -0000

> On Wednesday 09 June 2004 09:25 am, Ian FREISLICH wrote:
> > Hi
> >
> > I got this about an hour ago, maybe 10 minutes into a 'make world
> > -j8' on my SMP system.  I'll reproduce the panic and drop into the
> > debugger if possible if someone is willing to tell me what information
> > appart from this backtrace will be helpful.
> 
> Unfortunately this is a known deadlock that can happen with swapping that 
> there isn't an easy fix for.  If you want a quick hack, try commenting out 
> the 'wakeup(&proc0)' line in setrunnable().  It might take a bit longer for 
> the kernel to swap processes back in but should avoid the deadlock.

You mean like this?

diff -u -d -r1.249 kern_synch.c
--- kern_synch.c        7 Jun 2004 09:35:00 -0000       1.249
+++ kern_synch.c        9 Jun 2004 15:03:09 -0000
@@ -402,7 +402,14 @@
        if ((p->p_sflag & PS_INMEM) == 0) {
                if ((p->p_sflag & PS_SWAPPINGIN) == 0) {
                        p->p_sflag |= PS_SWAPINREQ;
-                       wakeup(&proc0);
+                       /*
+                        * XXX Nasty, Tricksy hack!!!!
+                        * Perhaps avoid a deadlock at the expense of swap
+                        * performance.
+                        */
+                       /*
+                        * wakeup(&proc0);
+                        */
                }
        } else
                sched_wakeup(td);

Ian

--
Ian Freislich