A multiprocessor data processing system is described wherein the processors (12a, 12b, 12c) communicate to each other via a shared memory (10). Each of the processors comprises an administration unit (18a) and a computational unit (12a). The administration unit of a writing processor (11a) maintains information defining a section in the memory (10) which is free for storing data objects for readout by the reading processor (12b). The administration unit (18b) of the reading processor (11b) maintains information defining a section in the memory (10) in which the writing processor has written completed data for the data objects. The processors are arranged to signal a message (M, M') to another processor via a processor synchronization channel for updating the information in the administration unit of said other processor. Each of the processors is arranged to suspend processing the stream of data objects when a location which it needs to access is outside the section defined by its administration unit.
