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    SubjectRe: [PATCH] [5/20] x86: Introduce nsec_barrier()

    * Andi Kleen <> wrote:

    > nsec_barrier() is a new barrier primitive that stops RDTSC speculation
    > to avoid races with timer interrupts on other CPUs.
    > Add it to all architectures. Except for x86 it is a nop right now. I
    > only tested x86, but it's a very simple change.
    > On x86 it expands either to LFENCE (for Intel CPUs) or MFENCE (for AMD
    > CPUs) which stops RDTSC on all currently known microarchitectures that
    > implement SSE. On CPUs without SSE there is generally no RDTSC
    > speculation.

    i've picked up your rdtsc patches into x86.git but have simplified it:
    there's no nsec_barrier() anymore - rdtsc() is always synchronous.
    MFENCE/LFENCE is fast enough. Open-coding such barriers almost always
    leads to needless trouble. Please check the next x86.git tree.


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