On Wed, Feb 21, 2018 at 09:42:08PM -0800, Daniel Lustig wrote: > And yes, if we go with a purely RCpc interpretation of acquire and > release, then I don't believe the writes in the previous critical > section would be ordered with the writes in the subsequent critical > section.
Excuse my ignorance (also jumping in the middle of things), but how can this be? spin_unlock() is a store-release, this means the write to the lock word must happen after any stores inside the critical section. spin_lock() is a load-acquire + test-and-set-ctrl-dep, we'll only proceed with the critical section if we observe the lock 'unlocked', which also means we must observe the stores prior to the unlock. And both the ctrl-dep and the ACQUIRE ensure future stores cannot happen before. So while the lock store and subsequent critical section stores are unordered, I don't see how it would be possible to not be ordered against stores from a previous critical section.