基于MPCP协议的任务最坏阻塞时间分析

Worst-Case Blocking Time Analysis for MPCP

多处理器天花板协议(MPCP)是经典的基于挂起机制的实时锁协议,被广泛应用于分组固定优先级(P-FP)调度下的多核/多处理器实时系统中。然而针对P-FP+MPCP调度的任务最坏阻塞时间分析往往过于保守,影响系统的可调度性。因此,该文提出一种计算实时任务最坏阻塞时间的新方法。其中实时任务模拟为非临界区与临界区的交替序列。该方法通过分析任务多次请求某一共享资源所需的最短执行时间,以及任务在任意时间内累计执行临界区时间的上限,提高了已有分析方法的计算准确性。可调度性实验表明,该方法优于已有方法,提高了系统可调度性。

Multiprocessor priority ceiling protocol （MPCP） is a classical suspension-based real-time locking protocol, wildly used in partitioned fixed-priority （P-FP） scheduled multiprocessor/multicore real-time systems. However, prior worst-ease task blocking time （WCTBT） analysis is pessimistic, which negatively impacts the system schedulability. Therefore, a novel WCTBT analysis is proposed. In this analysis, a task is modeled to be an alternative sequence of normal and critical section segments. By analyzing the minimum execution time required for a task to request several shared resources, this method improves the accuracy of prior work and provides an upper bound on the cumulative execution time for a task to execute critical sections in any time interval. Schedulability experiments indicate that the proposed method outperforms the existing methods and improves the system schedulability significantly.