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    SubjectRe: [PATCH 2/2] arm64: bpf: add BPF XADD instruction
    On Wed, Nov 11, 2015 at 12:35:48PM -0500, David Miller wrote:
    > From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
    > Date: Wed, 11 Nov 2015 09:27:00 -0800
    >
    > > BPF_XADD == atomic_add() in kernel. period.
    > > we are not going to deprecate it or introduce something else.
    >
    > Agreed, it makes no sense to try and tie C99 or whatever atomic
    > semantics to something that is already clearly defined to have
    > exactly kernel atomic_add() semantics.

    ... and which is emitted by LLVM when asked to compile __sync_fetch_and_add,
    which has clearly defined (yet conflicting) semantics.

    If the discrepancy is in LLVM (and it sounds like it is), then I'll raise
    a bug over there instead.

    Will


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