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    SubjectRe: call_function_many: fix list delete vs add race
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    On Mon, 2011-01-31 at 22:17 +0100, Peter Zijlstra wrote:
    > That's wrong:
    >
    > ->foo =
    > LOCK
    > UNLOCK
    > ->bar =
    >
    > can be re-ordered as:
    >
    > LOCK
    > ->bar =
    > ->foo =
    > UNLOCK

    Can it ? I though UNLOCK had a write barrier semantic ? It does on power
    at least :-) It should have since it shall prevent stores inside the
    lock region to pass the store of the unlock itself anyways.

    So yes, ->bar = can leak into the lock, as can ->foo =, but they can't
    be re-ordered vs. each other because the implied barrier will keep ->foo
    = in the same "domain" as the unlock itself.

    Or do other archs do something really nasty here that don't provide this
    guarantee ?

    Cheers,
    Ben.




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