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    SubjectRe: MMIO and gcc re-ordering issue
    Jeremy Higdon wrote:
    > We don't actually have that problem on the Altix. All writes issued
    > by CPU X will be ordered with respect to each other. But writes by
    > CPU X and CPU Y will not be, unless an mmiowb() is done by the
    > original CPU before the second CPU writes. I.e.
    >
    > CPU X writel
    > CPU X writel
    > CPU X mmiowb
    >
    > CPU Y writel
    > ...
    >
    > Note that this implies some sort of locking. Also note that if in
    > the above, CPU Y did the mmiowb, that would not work.

    Hmmm,

    Then it's less bad than I thought - my apologies for the confusion.

    Would we be able to use Ben's trick of setting a per cpu flag in
    writel() then and checking that in spin unlock issuing the mmiowb()
    there if needed?


    Cheers,
    Jes


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