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    SubjectRe: 2.6.19-rc1 genirq causes either boot hang or "do_IRQ: cannot handle IRQ -1"


    On Fri, 6 Oct 2006, Eric W. Biederman wrote:
    >
    > The change the patch introduced was that we are now always
    > pointing irqs towards individual cpus, and not accepting an irq
    > if it comes into the wrong cpu.

    I think we should just revert that thing. I don't think there is any real
    reason to force irq's to specific cpu's: the vectors haven't been _that_
    problematic a resource, and being limited to just 200+ possible vectors
    globally really hasn't been a real problem once we started giving out the
    vectors more sanely.

    And the new code clearly causes problems, and it seems to limit our use of
    irq's in fairly arbitrary ways. It also would seem to depend on the irq
    routing being both sane and reliable, something I'm not sure we should
    rely on.

    Also, I suspect the whole notion of only accepting an irq on one
    particular CPU is fundamentally fragile. The irq delivery tends to be a
    multi-phase process that we can't even _control_ from software (ie the irq
    may be pending inside an APIC or a bridge chip or other system logic, so
    things may be happening _while_ we possibly try to change the cpu
    delivery).

    So how about just reverting that change?

    Linus
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