Messages in this thread | | | Date | Thu, 3 Jan 2008 11:47:54 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH] [5/20] x86: Introduce nsec_barrier() |
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* Andi Kleen <ak@suse.de> 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.
Ingo
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