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    SubjectRe: Cache coherency... and locking
    On Fri, 21 Jul 2000 12:57:21 +0200, 
    Manfred Spraul <> wrote:
    >Keith Owens wrote:
    >> Linux requires strong write ordering[*]. That is, write A followed by
    >> write B will appear in memory in the order of A then B. So if any
    >> write on processor 1 is committed to memory then all preceding writes
    >> by processor 1 must already have been committed to memory.
    >Are you sure? Do you know a certain function that relies on strong write

    I could not find an absolute statement of this requirement, just lots
    of mail about spinlock optimisation that assume strong write ordering.
    where Linus says "Basically, everybody agrees on ordering of writes".
    It would be nice if the kernel gods made a definitive statement about
    the need or otherwise for strong write ordering.

    >Neither ia64 nor the other RISC processors guarantee strong write

    IA64 load.acquire and store.release are available to do strong write
    ordering, although the default option is weak order.

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