A memory lock mechanism within a multi-processor system is disclosed. A lock control section is initially assigned to a data block within a system memory of the multiprocessor system. In response to a request for accessing the data block by a processing unit within the multiprocessor system, a determination is made by a memory controller whether or not the lock control section of the data block has been set. If the lock control section of the data block has been set, the request for accessing the data block is denied. Otherwise, if the lock control section of the data block has not been set, the lock control section of the data block is set, and the request for accessing the data block is allowed.