Improved Blocking Time Analysis and Evaluation for the Multiprocessor Priority Ceiling Protocol

The Multiprocessor Priority Ceiling Protocol (MPCP) is a classic suspension-based real-time locking protocol for partitioned fixed-priority (P-FP) scheduling. However, existing blocking time analysis is pessimistic under the P-FP + MPCP scheduling, which negatively impacts the schedulability for real-time tasks. In this paper, we model each task as an alternating sequence of normal and critical sections, and use both the best-case execution time (BCET) and the worst-case execution time (WCET) to describe the execution requirement for each section. Based on this model, a novel analysis is proposed to bound shared resource requests. This analysis uses BCET to derive the lower bound on the inter-arrival time for shared resource requests, and uses WCET to obtain the upper bound on the execution time of a task on critical sections during an arbitrary time interval of Delta t. Based on this analysis, improved blocking analysis and its associated worst-case response time (WCRT) analysis are proposed for P-FP + MPCP scheduling. Schedulability experiments indicate that the proposed method outperforms the existing methods and improves the schedulability significantly.