Processors

Improved Analysis and Evaluation of Real-Time Semaphore Protocols for P-FP Scheduling

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Executive Summary

Several suspension-based multiprocessor real-time locking protocols for Partitioned Fixed-Priority (P-FP) scheduling have been proposed in prior work. These protocols differ in key design choices that affect implementation complexity, overheads, and worst-case blocking, and it is not obvious which is "Best" when implemented in a real OS. In particular, should blocked tasks wait in FIFO or in priority order? Should tasks execute critical sections locally on their assigned processor, or should resource access be centralized on designated processors? This paper reports on a large-scale, overhead-aware schedulability study comparing four protocols, namely the MPCP, FMLP+, DPCP, and the DFLP, which together cover each possible combination.

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