On Thu, 26 Jul 2007, Matthew Wilcox wrote:
>
> I noticed that we only look at the first action in the chain when
> determining whether to re-enable local interrupts during handle_IRQ_event.
You can't really share an interrupt handler that wants to run with
interrupts on with one that wants to run with them off.
That said, I think the whole IRQF_DISABLED thing should go away. It is
total legacy crud, methinks - it used to be SA_INTERRUPT, and it's always
worked the way IRQF_DISABLED works now: it only looks at the first one in
the chain.
> But we don't try to exclude sharing interrupts with mixtures of
> IRQF_DISABLED set and clear.
I think you should just consider it to be a "if you mix them, you get
randomr results".
> I just tried to do that locally, and one
> of my USB ports disappears, because it shares an interrupt with qla2xxx
> which sets IRQF_DISABLED, and UHCI doesn't.
There really is no excuse for using IRQF_DISABLED unless you're something
like a system device (like the timer interrupt or similar) and you have an
exclusive irq handler. A SCSI driver almost certainly has no business
doing it.
Generally, I would say that "IRQF_DISABLED | IRQF_SHARED" is an insane
combination, but a quick grep shows that it's distressingly common.
The real fix is to just leave it as it is. It's always worked that way.
IRQF_DISABLED basically cannot have any sane behaviour in the presense of
mixing.
Linus
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