A simple semaphore-queue management for multiprocessing systems

I. Recent issues of OSR (see Keedy 10/79, Denning and Dennis 4/80) witness a renewal of interest in solutions to the venerable problem of mutual exclusion. Indeed, the question seemed to have been settled with the introduction of the variable type SEMAPHORE, which may only be modified by primitive operations, and the commendable haste with which manufacturers introduced suitable instructions into their machines repertoires. These, coupled with concommitant (hardware implemented) locking at the storage access mechanism assured the primitivity of the operations. Even with semaphores however, one is still left with a number of problems, which the latter invention of MONITORs may be said to have by-passed rather than solved.