Recent kernel crashes at shutdown

[Dave Tyson <dtyson%anduin.org.uk@localhost>]

I having been running 6.99.16 on a i386 desktop system using the releng
snapshot from 28th January. Its been completely stable and I have been
using it with XFCE4 with no problems until today. I added a bunch of
extra packages and started them from rc.conf. On shutting down the
system it paniced with an assertion failure:

 Feb 11 19:58:11 darkstar savecore: reboot after panic: panic: kernel
diagnostic
assertion "lwpcnt >= 0" failed: file
"/home/builds/ab/HEAD/src/sys/kern/kern_uid
info.c", line 217

$NetBSD: kern_uidinfo.c,v 1.7 2012/06/09 02:55:32 christos Exp $


This happened just after swap and the shutdown hooks had been run.
Sometimes the system hangs, but mostly it takes a dump and reboots. A
bit of investigation showed that if HAL is running then the system will
crash, but if it isn't then shutdown proceeds OK.

I tried with the latest releng kernel from 10th Feb and that exhibits
the same issue.

kernel which first showed the problem:

NetBSD 6.99.16 (GENERIC) #0: Mon Jan 28 16:05: 30 UTC 2013
builds%b8.netbsd.org@localhost:/home/builds/ab/HEAD/i386/201301281320Z-obj/home/builds/ab/HEAD/src/sys/arch/i386/compile/GENERIC

I have core dumps from the crash on both the Jan 28/Feb 10 kernels if
needed.

Worth a PR ?

Dave