On Mon, Jul 13, 2015 at 02:09:50PM +0100, Peter Hurley wrote: > On 07/13/2015 08:15 AM, Will Deacon wrote: > > smp_mb__after_unlock_lock is used to promote an UNLOCK + LOCK sequence > > into a full memory barrier. > > > > However: > > > > - This ordering guarantee is already provided without the barrier on > > all architectures apart from PowerPC > > > > - The barrier only applies to UNLOCK + LOCK, not general > > RELEASE + ACQUIRE operations > > I'm unclear what you mean here: do you mean > A) a memory barrier is not required between RELEASE M + ACQUIRE N when you > want to maintain distinct order between those operations on all arches > (with the possible exception of PowerPC), or, > B) no one is using smp_mb__after_unlock_lock() in that way right now.
My understanding is (B), but Peter and I don't seem to agree yet! I'll tighten up the text once we reach a conclusion. Will -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
