Messages in this thread | | | Date | Thu, 26 Jul 2007 13:41:23 -0700 (PDT) | From | Linus Torvalds <> | Subject | Re: IRQF_DISABLED problem |
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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.
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