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    SubjectRe: smp_call_function_single lockups
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    On Fri, Feb 20, 2015 at 11:41 AM, Ingo Molnar <mingo@kernel.org> wrote:
    >
    > I'm not so sure about that aspect: I think disabling IRQs
    > might be necessary with some APICs (if lower levels don't
    > disable IRQs), to make sure the 'local APIC busy' bit isn't
    > set:

    Right. But afaik not for the x2apic case, which this is. The x2apic
    doesn't even have a busy bit, and sending the ipi is a single write,

    I agree that when doing other apic implementations, we may need to
    guarantee atomicity for things like "wait for apic idle, then send the
    ipi".

    Linus


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