Re: PCI, ACPI, IRQ, IOAPIC: reroute PCI interrupt to legacy boot interrupt equivalent

[Olaf Dabrunz <od@suse.de>]

On 14-Jan-09, Bjorn Helgaas wrote:
> On Wednesday 14 January 2009 02:57:22 am Stefan Assmann wrote:
> > Shaohua Li wrote:
> > > So a device can generate interrupt from two irqs. And we can get the irq
> > > number for the routing table. Can we extend the irq mechanism and
> > > automatically register the interrupt handler for the two irqs?
> > 
> > This would not solve the problem of asserting 2 different interrupt
> > lines, in the masked interrupt handling case, for 1 interrupt request.
> > The result would be that the ISR is called twice and at the second call
> > you can't be sure that the device hasn't already been serviced.
> 
> Calling the ISR twice isn't a problem, is it?  We're talking about
> PCI interrupts, which are shareable, so ISRs have to handle being
> called extra times.
> 
> There's still the problem that the core will disable an IRQ if we
> take it too many times without any ISR that cares about it.  But that's
> a core issue, not an ISR issue.

It is not solvable in the core. How do you find out that the "nobody
cared" spurious IRQ is benign?

Regards,

-- 
Olaf Dabrunz (od/odabrunz), SUSE Linux Products GmbH, Nürnberg

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