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If compare-exchange has higher overheads tha= n other atomics=0A= >> > then we should investigate more efficient locking sequences.=0A= >>=0A= >> compare-exchange can be very expensive under contention.=0A= >>=0A= >=0A= > Which locks should we look into dropping CAS? pthread_mutex? Anything els= e?=0A= =0A= There are several internal locking schemes plus uses of CAS spread all over= .=0A= There is also the odd define ATOMIC_EXCHANGE_USES_CAS which almost no targe= t=0A= seems to know what to set to - it is used in pthread_spin_lock in a way tha= t makes no=0A= sense. I believe the answer should be 0 for all since exchange is typically= simpler and=0A= faster than compare-exchange. =0A= =0A= Cheers,=0A= Wilco=