Messages in this thread | | | Date | Thu, 17 Jul 2008 19:04:05 +0200 (CEST) | From | Thomas Gleixner <> | Subject | Re: PCI: MSI interrupts masked using prohibited method |
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On Thu, 17 Jul 2008, Matthew Wilcox wrote:
> On Thu, Jul 17, 2008 at 05:58:26PM +0200, Thomas Gleixner wrote: > > > This is a good thought, let's follow it through. What if we simply make > > > ->mask a no-op for devices which don't support mask bits? > > > > Yep. You can also use fasteoi_handler, which just calls ->eoi() after > > the handler. > > I think that exposes us to a race. > > CPU takes the first interrupt, calls handle_fasteoi_irq(). That > calls handle_IRQ_event() which calls the device's interrupt handler. > Interrupt handler reads status register to determine what to do next. > Device generates second interrupt and changes status register. Second > interrupt is never delivered because the ->eoi hasn't been called yet.
Yeah, I know. The question is how the hardware works; there is fasteoi capable hardware around (not on x86) which works with edge type interrupts.
> I plan to keep using the edge handler which solves this race by > calling mask_ack(). For MSIs without mask bits, it will do nothing.
Ah, there are ones w/o a mask bit. That detail slipped through.
Thanks,
tglx
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