Apparatus and method for providing synchronization between processes and events occurring at different times in a data processing system

摘要

An information structure, or semaphore, serves as a signalling mechanism in process synchronization to connect a process and a non-simultaneously occurring event or resource. The semaphore is a data structure which stores representations of processes awaiting particular events or alternatively stores representations of events awaiting processes. Semaphore data structures are developed in two storage areas. First and second groups of process links are stored in the first storage area to establish, respectively, a first queue of processes ready to operate and a second queue, associated with the semaphore structure, of processes awaiting occurrences of a first particular event prior to being ready to operate. In the second storage area are stored first and second groups of message links to establish respectively a first queue, associated with a semaphore structure, representing second particular events and a second queue of unused links. A signal is generated in response to operation of a first process to denote the occurrence of a first event. In response to the signal, the first event is associated with a process represented by a process link in the second queue of process links when the first event is the first particular event. When no queue has a process link identifying a process awaiting the occurrence of the first event, a representation of the first event occurrence is stored in a message link of the second queue of message links to be transferred to the first queue of message links. Process and event occurrence representations are thus transferred among the process and event queues during synchronization that takes place between the processes and events.