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    SubjectRe: [PATCH 0/24] make atomic_read() behave consistently across all architectures
    On Tue, Aug 21, 2007 at 01:02:01AM +0200, Segher Boessenkool wrote:
    > >>And no, RMW on MMIO isn't "problematic" at all, either.
    > >>
    > >>An RMW op is a read op, a modify op, and a write op, all rolled
    > >>into one opcode. But three actual operations.
    > >
    > >Maybe for some CPUs, but not all. ARM for instance can't use the
    > >load exclusive and store exclusive instructions to MMIO space.
    > Sure, your CPU doesn't have RMW instructions -- how to emulate
    > those if you don't have them is a totally different thing.

    Let me say it more clearly: On ARM, it is impossible to perform atomic
    operations on MMIO space.

    Russell King
    Linux kernel 2.6 ARM Linux -
    maintainer of:
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