Re: [RFC PATCH v2] memory-barriers: remove smp_mb__after_unlock_lock()

[Peter Zijlstra]

On Mon, Jul 13, 2015 at 01:15:04PM +0100, Will Deacon wrote:
> smp_mb__after_unlock_lock is used to promote an UNLOCK + LOCK sequence
> into a full memory barrier.
> 
> However:

>   - The barrier only applies to UNLOCK + LOCK, not general
>     RELEASE + ACQUIRE operations

No it does too; note that on ppc both acquire and release use lwsync and
two lwsyncs do not make a sync.


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