Re: Unhandled IRQs on AMD E-450
From: Jeroen Van den Keybus
Date: Fri Apr 27 2012 - 09:28:34 EST
> Apparently there are
> some pieces of hardware that generate a small number of spurious IRQs
> "normally" and lowering the threshold to such a small value caused
> those machines to kick into polling mode when they really didn't need
> to.
Hm. I'd really expect a spurious IRQ to happen as its name suggests:
spuriously. What kind of hardware behaves like this ?
> 1) While the quirk helps shield people without the buggy bridge, it
> doesn't help the case where people have the bridge, but they have no
> devices actually behind it. That means such setups hit the polling
> mode when they don't really need to as described above.
Curious, the polling mode is left until a new spurious IRQ is detected.
> 2) People, rightfully, complain that it makes inter-activity on their
> desktop pretty laggy. The mouse pointer jumps around a lot and key
> strokes are often missed. For a server class machine, I doubt it
> would matter much but Fedora is essentially a desktop distro so that
> tends to be a high priority.
Again, I am a bit surprised. However, according to your patch:
> + if (!irq_poll_and_retry)
> + if (likely(desc->irq_count < 100000))
> + return;
> + else
> + if (likely(desc->irq_count < 10))
> + return;
Don't you mean :
+ if (!irq_poll_and_retry) {
+ if (likely(desc->irq_count < 100000))
+ return;
+ }
+ else {
+ if (likely(desc->irq_count < 10))
+ return;
+ }
Jeroen.
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