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    SubjectRe: [PATCH 13/15] x86: add cmpxchg_flag() variant
    On Tue, 23 Aug 2011, H. Peter Anvin wrote:

    > On 08/23/2011 03:15 PM, Jeremy Fitzhardinge wrote:
    > >
    > > However, having prototyped it, I dunno, it doesn't really seem like much
    > > of a win for all the extra code it adds. I just can't get too excited
    > > about an extra test instruction adjacent to a monster like a locked
    > > cmpxchg. The jump variant avoids the test, but gcc still generates some
    > > pretty bogus stuff:
    > >
    > A compare is hardly a big cost, as you're quite correctly pointing out.

    Could become relatively costly if the cmpxchg is not locked or the compare
    involves comparing multiple words.

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