Re: how to debug a deadlock'ed kernel?

[Brian Horton]

Thanks, I'll try the nmi_watchdog option out. It appears to not be in
the 2.2.14 kernel, but is in a 2.2.19 kernel that I have from RedHat.

Is there a version of kgdb that works with 2.2.x kernels? I only see 2.4
kernels on the web page (http://kgdb.sourceforge.net)

thx.bri.

george anzinger wrote:
> 
> Brian Horton wrote:
> >
> > Anyone got any good tips on how to debug a SMP system that is locked up
> > in a deadlock situation in the kernel? I'm working on a kernel module,
> > and after some number of hours of stress testing, the box locks up. None
> > of the sysrq options show anything on the display, though the reBoot
> > option does reboot the system. RedHat 6.2 and its 2.2.14 kernel. Doesn't
> > hang for me on 2.4, so I need to debug it here...
> >
> > Any hints?
> 
> First read about the NMI boot option in Documentation/nmi_watchdog.txt.
> If you have this turned on and are not oopsing, then the timer (at
> least) is interrupting.  The next step I would take would be to used
> either kdb (no experience) or kgdb.  I have my own version of this if
> you are interested.  It does, however, require an RS232 (serial)
> connection to a host machine.
> 
> I don't know about kdb, but kgdb (my version) uses the NMI to trap the
> other cpus and also traps NMIs on the way to oopsing.
> --
> George           [e-mail]
> High-res-timers: http://sourceforge.net/projects/high-res-timers/
> Real time sched: http://sourceforge.net/projects/rtsched/