Messages in this thread | | | Date | Thu, 1 Oct 2015 14:27:16 +0200 | From | Peter Zijlstra <> | Subject | Re: [RFC v2 5/7] powerpc: atomic: Implement cmpxchg{,64}_* and atomic{,64}_cmpxchg_* variants |
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On Wed, Sep 16, 2015 at 11:49:33PM +0800, Boqun Feng wrote: > Unlike other atomic operation variants, cmpxchg{,64}_acquire and > atomic{,64}_cmpxchg_acquire don't have acquire semantics if the cmp part > fails, so we need to implement these using assembly.
I think that is actually expected and documented. That is, a cmpxchg only implies barriers on success. See:
ed2de9f74ecb ("locking/Documentation: Clarify failed cmpxchg() memory ordering semantics")
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