Global Real-Time Semaphore Protocols: A Survey, Unified Analysis, and Comparison

All major real-time suspension-based locking protocols (or semaphore protocols) for global fixed-priority scheduling are reviewed and a new, unified response-time analysis framework applicable to all protocols is proposed. The newly proposed analysis, based on linear programming, is shown to be clearly preferable compared to all prior conventional approaches. Based on the new analysis, all protocols are directly compared with each other in a large-scale schedulability study. Interestingly, the Priority Inheritance Protocol (PIP) and the Flexible Multiprocessor Locking Protocol (FMLP), which are the two oldest and simplest of the considered protocols, are found to perform best.