On Tue, Dec 10, 2013 at 06:25:28PM +0100, Peter Zijlstra wrote: > On Tue, Dec 10, 2013 at 09:12:47AM -0800, Paul E. McKenney wrote: > > > The way I read the above it says that you need > > > smp_mb__after_unlock_lock() when the UNLOCK and LOCK are on the same > > > variable. That doesn't make sense, I thought that was the one case we > > > all agreed on it would indeed be a full barrier without extra trickery. > > > > On x86, sure, but smp_mb__after_unlock_lock() is nothingness on x86 > > anyway. Other architectures might benefit from requiring that the > > smp_mb__after_unlock_lock() be used in this case. > > Confused, UNLOCK X, LOCK X, must always be fully serializing. That's the > entire purpose of the thing. > > The only place you can go play games (and clearly we are going there) is > when the UNLOCK and LOCK are on different variables.
That would certainly be a good assumption to preserve, and it would eliminate most of the need for smp_mb__after_unlock_lock(). - Josh Triplett -- 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/
