RE: [Xen-devel] bogus HPET initialization order on x86

["Wei, Gang" <gang.wei@xxxxxxxxx>]

Jan Beulich wrote on 2011-03-11:
>>>> On 10.03.11 at 04:35, "Wei, Gang" <gang.wei@xxxxxxxxx> wrote:
>> Jan Beulich wrote on 2011-03-09:
>>> Also, what's the point of decrementing the per-CPU irq_count in
>>> hpet_legacy_irq_tick()?
>> 
>> The per-CPU irq_count are used for calculate the total irq number
>> excluding hpet irqs in a past period to give a estimation of IO
>> frequence. The hpet irq was counted in do_IRQ, so need to reduce it
>> while handling it. You can see another one in hpet_interrupt_handler().
> 
> I can understand the latter, but the one I was asking about decrements
> irq_count even if not calling the event handler (i.e.
> when returning zero from the function). In other words, I would have
> understood what this is for if it was sitting after the initial if().

The irq_count is added to count the total irq number excluding hpet/pit irqs, 
so even the real event handler was not called, the adjustment should still be 
done.

Jimmy



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