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Date: Tue, 16 Dec 2003 11:44:25 -0500 (EST)
From: "Richard B. Johnson" <root@chaos.analogic.com>
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To: "Maciej W. Rozycki" <macro@ds2.pg.gda.pl>
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Subject: Re: Catching NForce2 lockup with NMI watchdog
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On Tue, 16 Dec 2003, Maciej W. Rozycki wrote:

> On Tue, 16 Dec 2003, Richard B. Johnson wrote:
>
> > Masking OFF the timer channel 0 in the interrupt controller
> > is probably the easiest thing to do. The port is read-write,
> > and the OCW default to having it accessible.
>
>  Note we are writing about configurations involving an I/O APIC, so things
> are not that easy -- the 8254 timer IRQ may be wired in different ways.
>
> --
> +  Maciej W. Rozycki, Technical University of Gdansk, Poland   +
> +--------------------------------------------------------------+
> +        e-mail: macro@ds2.pg.gda.pl, PGP key available        +


Well if I was trying to isolate a problem, I would make it
that easy. You boot the machine in its simplist configuration
and work "up" from there.

Although I haven't looked at recent source-code, with APIC, the
problem is even simpler. If you booted with APIC, just set
the global "using_apic_timer" to zero and, voila`, timer-ticks
stop.

Any any event, the caller needs to know that if there is
any code executing anywhere that does the equivalent of

		for(;;)
                      ;

...the machine will lock-up forever because without that timer,
there will be no preemption. Once a CPU-hog gets the CPU, only
and interrupt can get it away.


Cheers,
Dick Johnson
Penguin : Linux version 2.4.22 on an i686 machine (797.90 BogoMips).
            Note 96.31% of all statistics are fiction.