Re: nmi watchdog failure on dual Athlon box

[Joerg Sommrey <jo175@sommrey.de>]

On Tue, Sep 28, 2004 at 06:08:37PM +0100, Maciej W. Rozycki wrote:
> On Tue, 28 Sep 2004, Joerg Sommrey wrote:
> 
> > just tried Ingo's "lockupcli" nmi watchdog test - it fails to unlock the
> > box.
> > 
> > boot-parm:
> > ...nmi_watchdog=2...
> 
>  The local APIC NMI watchdog has limited capabilities.  It may fail to 
> trigger for certain lockups because there is no available event that would 
> happen periodically regardless of the CPU state.  I can only suspect what 
> "lockupcli" does (where is it available from, anyway?), but if it runs 
> "cli; hlt", then the watchdog *will* fail.

Here's the quote from Ingo's mail:
In <2Jo20-7ry-33@gated-at.bofh.it> Ingo Molnar <mingo@elte.hu> writes:
|once the NMI watchdog is up and running it should catch all hard lockups
|and print backtraces to the serial console - even if you are within X
|while the lockup happens. You can test hard lockups by running the
|attached 'lockupcli' userspace code as root - it turns off interrupts
|and goes into an infinite loop => instant lockup. The NMI watchdog
|should notice this condition after a couple of seconds and should abort
|the task, printing a kernel trace as well. Your box should be back in
|working order after that point.

[...]

|--- lockupcli.c
|
|main ()
|{
|	iopl(3);
|	for (;;) asm("cli");
|}

Does this mean there is a good reason for further investigations on why
the IO-APIC NMI watchdog doesn't work? Until now I thought it would
be ok as long as the local APIC NMI watchdog is set up.

-jo

-- 
-rw-r--r--  1 jo users 63 2004-09-28 18:42 /home/jo/.signature