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    Subject[patch 0/2] x86/fpu: Make fpu_lock() RT compliant
    FPU serialization uses

    preempt_disable(); local_bh_disable();

    which is silly because local_bh_disable() implicitly disables
    preemption. So this can be reduced to local_bh_disable().

    But this does not work on RT kernels because local_bh_disable() only
    serializes bottom half related processing via a local lock, but does not
    disable preemption.

    On RT kernels preempt_disable() is the right choice because on RT bottom
    half processing is always in thread context, so preempt_disable()
    implicitly protects against bottom half processing there.

    Thanks,

    tglx

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