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    SubjectRe: [PATCH 0/24] make atomic_read() behave consistently across all architectures
    >>>> 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.

    It's all completely beside the point, see the other subthread, but...

    Yeah, you can't do LL/SC to MMIO space; ARM isn't alone in that.
    You could still implement atomic operations on MMIO space by taking
    a lock elsewhere, in normal cacheable memory space. Why you would
    do this is a separate question, you probably don't want it :-)


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      Last update: 2007-08-21 16:59    [W:0.034 / U:40.764 seconds]
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