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SubjectRe: Strange interrupt behaviour
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> I'm also seeing interrupt funnies in various later 2.1.x.
> The extremely trivial interrupt routine in baycom_ser_hdx (if
> you uncomment calls to the actual rx/tx functions) fails
> there with 3600int/s, however if I reduce the int rate
> it works.

I've now catalogued four different types of breakage still present in
2.1.10x IRQ handling

1. The latency has gone completely to shit. Its so slow handling IRQ's
that I can no longer run 64Kbit synchronous on 2.1.x kernels. People
with sync cards are trapped in 2.0 or blow $500 on a smart card.
This we have to sort - even NT can do 64K sync cards.

2. Edge triggered PCI on old motherboards (PPro 120 sort of era) running
SMP crash and burn on boot (third party report)

3. Drivers that get repeated interrupts appear to re-enter the handler
uncontrollably blow the stack and crash. I suspect nested interrupt
handling problems may be half the 8K stack issue, and could be tons
of our other remaining bugs.

With my sync card this works

foo_interrupt(){...return...}

this crashes

foo_interrupt(){save_flags(flags);restore_flags(flags);}

4. We've lost the fast irq stuff. Thats unbelievably bad and may be part
of #1.

Alan


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