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

摘要

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 △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.