Any way to debug a hard lockup?

[Sean McNeil]

On Wed, 2004-07-07 at 12:03, Conrad J. Sabatier wrote:
> For the last few days, my amd64 box (Athlon 64 3200+, 5.2-CURRENT,
> updating just about daily lately) has been locking up hard fairly
> often, and I have no clue as to why.
> 
> Checking the logs after rebooting reveals nothing at all out of the
> ordinary.  The box just "seizes up" and that's that.  Only thing to do
> is a power-down and restart.
> 
> Changing from SCHED_ULE to SCHED_4BSD appears to make no difference at
> all.
> 
> My other box, an older (32-bit) Athlon, has been rock stable.  I've
> been keeping both machines updated simultaneously to exactly the same
> revisions, using as near-identical system settings as possible also,
> the main difference being I'm running X.org/GNOME on the amd64 box and
> no X on the i386 box.
> 
> Any suggestions?  Instinct tells me it may be a problem with some of
> the ports I'm running (X.org/GNOME, hence the Cc:s), but how to verify?
> Sure, I could run without X a while and see how it goes, but that still
> won't help to isolate the problem, if it is, in fact, port-related.
> 
> Thanks.

I've had the same problem, but not the time to look into it.  You may
want to try to telnet, ssh, or use the serial port.  I'm not sure, but
it seems the machine is still running but X is locked up solid and
ctl-alt-f1 doesn't work.  Serial port access would be your best bet. 
The lockups started for me after the native preemption stuff was added
in.

Sean