On Tue, Jul 14, 2015 at 08:43:44AM +1000, Benjamin Herrenschmidt wrote: > On Tue, 2015-07-14 at 00:15 +0200, Peter Zijlstra wrote: > > > > This is instead the sequence that is of concern: > > > > > > store a > > > unlock M > > > lock N > > > load b > > > > So its late and that table didn't parse, but that should be ordered too. > > The load of b should not be able to escape the lock N. > > > > If only because LWSYNC is a valid RMB and any LOCK implementation must > > load the lock state to observe it unlocked. > > What happens is that the load passes the store conditional, though it > doesn't pass the load with reserve. However, both store A and unlock M > being just stores with an lwsync, can pass a load, so they can pass the > load with reserve. And thus inside the LL/SC loop, our store A has > passed our load B.
Ah cute.. Thanks, clearly I wasn't awake enough anymore :-) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
