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On 04/13/2017 10:16 AM, Torvald Riegel wrote:
On Thu, 2017-04-13 at 07:10 +0200, Florian Weimer wrote:On 11/28/2016 12:51 PM, Torvald Riegel wrote:This means that for an LP32 architecture such as i686 which could conceivable provide 64-bit atomics, we might try to perform an atomic operation on a potentially misaligned uint64_t value.i686 has no 64b atomic loads or stores.double loads and stores via the FPU are atomic, and they preserve all bit patterns.I believe that the precise status on this is that we believe that they are atomic, but it's not explicitly guaranteed.
No, it is guaranteed. See Vol 3, Section 8.1.1: # The Pentium processor (and newer processors since) guarantees that # the following additional memory operations will always be carried # out atomically: # • Reading or writing a quadword aligned on a 64-bit boundary r~
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