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    SubjectRe: [RFC PATCH] x86 alternatives : fix LOCK_PREFIX race with preemptible kernel and CPU hotplug
    * H. Peter Anvin ( wrote:
    > Jeremy Fitzhardinge wrote:
    >> Ah, OK. I'd thought we started unlocked, but given that I've just been
    >> disassembling the kernel and looking at the lock prefixes, that's a bit of
    >> a braino on my part.
    >> BTW, using the ds prefix allows us to undo the hack of dealing with locked
    >> instructions with exception handlers. There was a bug where if we do
    >> lock->nop, then the address of a faulting instruction changes, so we need
    >> exception records for both the locked and unlocked forms. Using ds means
    >> the instruction size doesn't change, so we only need one exception record.
    >> I don't remember off hand where that happens.
    > Using %ds: rather than nop really seems to solve a whole lot of problems,
    > and might even be faster to boot. It really sounds like a no-brainer.
    > -hpa

    So should I wait a bit for more comments or straightforwardly submit
    this as a patch rather than RFC ?


    Mathieu Desnoyers
    OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68

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