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SubjectRe: [PATCH][RFC] per isr in_progress markers

On Mon, 9 Sep 2002, Ingo Molnar wrote:
>
> There's also the following effect that could generate additional
> interrupts: the *same* IRQ source that is currently executing might
> generate a (spurious but otherwise harmless) interrupt if we first ACK the
> card then ACK the APIC and then do processing. Our current way of masking
> interrupts in the IO-APIC at least leaves them pending there until the
> handler's main work loop is finished and mitigates irqs.

I agree with you, but that is only true for edge-triggered APIC
interrupts, though - for level-triggered ones we will just re-take the
interrupt when we unmask it again.

Which is kind of sad. Is there some fast way to read the status of a
level-trigger irq off the IO-APIC in case it is still pending, and to do
the mitigation even for level-triggered?

(Btw, if there is, that would also allow us to notice the "constantly
screaming PCI interrupt" without help from the low-level isrs)

Linus

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