BARRIERS PROCESSING IN A MULTIPROCESSOR SYSTEM HAVING A WEAKLY ORDERED STORAGE ARCHITECTURE WITHOUT BROADCAST OF A SYNCHRONIZING OPERATION

A data processing system employing a weakly ordered storage architecture includes first and second sets of processing units coupled to each other and data storage by an interconnect fabric. Each processing unit has a processor core having an associated cache hierarchy including at least a level one, level two and level three cache memories. A request to perform an update to a portion of a first image of memory contained in the level three cache memory of a first processing unit while at last one kill-type command is pending at the first processing unit, the cache hierarchy of the first processing unit permitting the update to be exposed to any first processor core only after the at least one kill-type command is complete.