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

From: Gunther Mayer (gunther.mayer@gmx.net)
Date: Tue Sep 10 2002 - 13:07:22 EST


Zwane Mwaikambo wrote:

>On Mon, 9 Sep 2002, Linus Torvalds wrote:
>
>
>
>>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?
>>
>>
>
>perhaps Remote IRR might help there?
>
>
>
>>(Btw, if there is, that would also allow us to notice the "constantly
>>screaming PCI interrupt" without help from the low-level isrs)
>>
>>
>
>As an aside, i just had an idea for another way to improve interrupt
>handling latency. Instead of walking through all the isrs in the chain,
>we can have an isr flag wether it was the source of the irq, and if so we
>stop right there and not walk through the other isrs.
>
This method is flawed for edge-triggered interrupts: you will miss any
interrupts which come in before you acked the first.

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