Where memory is guaranteed to be consistent only following certain synchronization operations. Acquiring processor determines which incoming writes have timestamps larger than its local timestamp. Responses may include an invalidation or an update.
Eager protocols push modifications to all cachers at synchronization variable releases.
When the locking processor releases its writes, all other cachers are notified that they must invalidate their copies. When the locking processor releases its writes, all other cachers are sent an update. Lazy protocols pull the modifications at synchronization variable acquires, and communicate only with the acquirer. The last releaser piggybacks write notices onto the lock grant message sent to the acquirer. Local copies of pages for which a write notice with a larger timestamp is received are invalidated.