On Thu, Oct 01, 2015 at 02:27:15PM +0200, Peter Zijlstra wrote: > 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")
Also: 654672d4ba1a6 (Will Deacon 2015-08-06 17:54:37 +0100 28) * store portion of the operation. Note that a failed cmpxchg_acquire 654672d4ba1a6 (Will Deacon 2015-08-06 17:54:37 +0100 29) * does -not- imply any memory ordering constraints. _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev