On Tue, 2005-11-01 at 12:33 +0100, Ingo Molnar wrote:
> * Steven Rostedt <[email protected]> wrote:
>
> > Hi Ingo and Thomas,
> >
> > On some of my machines, I've been experiencing false NMI lockups.
> > This usually happens on slower machines, and taking a look into this,
> > it seems to be due to a short time where no processes are using
> > timers, and the ktimer interrupts aren't needed. So the APIC timer,
> > which now is used only for the ktimers, has a five second pause, and
> > causes the NMI to go off. The NMI uses the apic timer to determine
> > lockups.
> >
> > So, I added a more generic method. This only works for x86 for now,
> > but it has a #ifdef to keep other archs working until it implements
> > this as well. I added a nmi_irq_incr which is called by __do_IRQ in
> > the generic code. This is what is used in the NMI code to determine
> > if the CPU has locked up. This way we don't have to worry about what
> > resource we are using for timers.
>
> but e.g. the APIC timer doesnt go through do_IRQ(), it has its own
> special IRQ entry code. The simple solution would be to also include the
> IRQ#0 count in the NMI watchdog detection condition - i.e. something
> like the patch below. Hm?
>
> Ingo
>
> Index: linux/arch/i386/kernel/nmi.c
> ===================================================================
> --- linux.orig/arch/i386/kernel/nmi.c
> +++ linux/arch/i386/kernel/nmi.c
> @@ -521,7 +521,7 @@ void notrace nmi_watchdog_tick (struct p
> */
> int sum, cpu = smp_processor_id();
>
> - sum = per_cpu(irq_stat, cpu).apic_timer_irqs;
> + sum = per_cpu(irq_stat, cpu).apic_timer_irqs + kstat_irqs(0);
>
> profile_tick(CPU_PROFILING, regs);
> if (nmi_show_regs[cpu]) {
:) I thought about doing that too, but I wanted a more generic solution.
I think I would have just put the nmi_incr in the apic interrupt handler
as well. That way we might some day be able to pull out the
nmi_watchdog detect code out of the arch specific all together.
-- Steve
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