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    SubjectRe: [PATCH 0/24] make atomic_read() behave consistently across all architectures
    On Mon, Sep 10, 2007 at 11:59:29AM -0700, Christoph Lameter wrote:
    > On Fri, 17 Aug 2007, Segher Boessenkool wrote:
    >
    > > "volatile" has nothing to do with reordering. atomic_dec() writes
    > > to memory, so it _does_ have "volatile semantics", implicitly, as
    > > long as the compiler cannot optimise the atomic variable away
    > > completely -- any store counts as a side effect.
    >
    > Stores can be reordered. Only x86 has (mostly) implicit write ordering. So
    > no atomic_dec has no volatile semantics and may be reordered on a variety
    > of processors. Writes to memory may not follow code order on several
    > processors.

    The one exception to this being the case where process-level code is
    communicating to an interrupt handler running on that same CPU -- on
    all CPUs that I am aware of, a given CPU always sees its own writes
    in order.

    Thanx, Paul
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