Low Cost Low Contention Shared Exclusive Locks
Original Publication Date: 1981-Mar-01
Included in the Prior Art Database: 2005-Feb-11
Systems need shared/exclusive lock mechanisms to control access to shared resources. The microinstruction set of the computer system provides Djikstra-style semaphores with built-in dispatching. However, the primitives provided do not in themselves provide a shared/exclusive lock mechanism. The contention properties of the present method are superior over the prior art described in Appendix A. The shared/ exchange lock mechanism used by storage management of the computer system satisfies the following design constraints: 1. The implementation, especially the shared path, must be efficient. Since it is used by page faults, excessive cost is intolerable. 2. The implementation must have low contention. Users desiring to obtain the lock shared must not wait for significant periods of time unless the lock is held exclusively.