On Tue, Jan 26, 2016 at 12:13:39PM -0800, Paul E. McKenney wrote: > On Tue, Jan 26, 2016 at 11:19:27AM +0100, Peter Zijlstra wrote: > > So isn't smp_mb__after_unlock_lock() exactly such a scenario? And would > > not someone trying to implement RCsc locks using locally transitive > > RELEASE/ACQUIRE operations need exactly this stuff? > > > > That is, I am afraid we need to cover the mix of local and global > > transitive operations at least in overview. > > True, but we haven't gotten to locking yet. The mythical smp_mb__after_release_acquire() then ;-) (and yes, I know you're going to say we don't have that) > That said, I would argue > that smp_mb__after_unlock_lock() upgrades locks to transitive, and > thus would not be an exception to the "no combining transitive and > non-transitive steps in cycles" rule. But But But ;-) It does that exactly by combining. I suspect this is (partly) the source of your SC chains with one PC link example.
