Subject: Re: Methods of debugging a locked-up/hung system that doesn't generate a kernel core dump?
To: None <>
From: Manuel Bouyer <>
List: tech-kern
Date: 04/13/2005 12:20:54
On Tue, Apr 12, 2005 at 08:59:57PM -0400, wrote:
> I have a NetBSD 1.6 based system that randomly locks-up/hangs
> (as though a thread had indefinitely disabled interrupts).
> Eventually, our H/W based watchdog resets the CPU, and the system 
> reboots
> but without saving the kernel core (since the normal panic path wasn't 
> executed).
> Are there any debugging techniques that can be used to capture the 
> state of the
> system when such a lock-up occurs?
> One idea is to reconfigure the H/W watchdog to instead generate a NMI 
> to the processor;
> the NMI handler could then capture system state prior to resetting the 
> CPU.

I assume it's x86 ?
If ddb is compiled in the kernel, a NMI should drop the box to debugger.

Manuel Bouyer, LIP6, Universite Paris VI. 
     NetBSD: 26 ans d'experience feront toujours la difference