Panic: spin lock held too long when booting

[Mike Clarke]

I'm getting frequent panics due to spin lock held too long when booting 
my recently built 6.3 system with an Athlon 4850e dual core processor 
on a Foxconn 6150M2MA motherboard (GeForce 6150 and nForce 430 
chipsets).

FreeBSD curlew.lan 6.3-STABLE FreeBSD 6.3-STABLE #2: Sat Jul 12 09:43:21 
BST 2008     root at curlew.lan:/usr/obj/usr/src/sys/CURLEW  i386

I'd welcome any advice on how to understand and fix this. 

The panics usually happen immediately after the "Mounting local 
filesystem" message, but sometimes just before the end of the boot 
process.

The system goes through the motions of producing a crash dump with a 
visible count down on the screen followed with...

Dump complete
Automatic reboot in 15 seconds - press a key on the console to abort
Rebooting...
cpu_reset: Stopping other CPUs

... then it just hangs until I do a hard reset.

The odd thing is that when I reboot there doesn't appear to be any crash 
dump - I see the following messages:

Checking for core dump on /dev/ad4s1b...
savecore: no dumps found

Is the lack of a dump due to some config error of mine, or an effect of 
the spin lock problem?

Here's the head of my kernel file ...

include         GENERIC
nocpu           I486_CPU
nocpu           I586_CPU
ident           CURLEW
nooptions       COMPAT_FREEBSD4         # Compatible with FreeBSD4
nooptions       COMPAT_FREEBSD5         # Compatible with FreeBSD5
options         DDB
options         KDB
options         KDB_UNATTENDED

... the rest of the file is just "nodevice" lines for various devices I 
don't have.

And from /etc/rc.conf ...

dumpdir="/usr/crash"
dumpdev="/dev/ad4s1b"

Messages on the console while booting imply debugging is enabled...

KDB: debugger backends: ddb
KDB: current backend: ddb
...
kernel dumps on /dev/ad4s1b

...

But I'm still a bit dubious as to whether I've really managed to create 
a debugging kernel. I was under the impression that there should be 
some *.symbols files in the /boot/kernel directory but there aren't any 
(or is this just a rev. 7 thing?) and the kernel directory is only 24 
MB.

I also noticed when building the kernel there were lines like ...

objcopy --strip-debug kernel.debug kernel

... though I do still have /usr/obj/usr/src/sys/CURLEW/kernel.debug. 
should I be doing something with this?

-- 
Mike Clarke