* 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.
this would be a bug - the jiffy tick should be processed every 1 msec,
regardless of whether there are any ktimers pending. (in the future we
want to use a special ktimer for the jiffy tick, but that's not
implemented yet.)
> 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.
this will be useful for tickless stuff - but right now 'no APIC timer
irq for 5 seconds' is a 'must not happen'.
Ingo
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