Abstract: Each of processors in a multiprocessor system has a circuit for sending a synchronizing signal to a storage controller (SC) connected thereto when executing a synchronization instruction such as a start, end or barrier synchronization instruction. Each of the SCs has a circuit for notifying the corresponding processor of establishment of a synchronization upon detection of completion of a check to be made by an address management table FAA and of the issuing of necessary cache cancel requests corresponding to a store instruction issued before the synchronization instruction and upon recognition of the fact that all the processors have sent their synchronizing signals and that the issuing of all the cache cancel requests have been complete.