Real-time systems are collections of tasks where in addition to any ordering constraints imposed by precedences between the tasks, there are also timing constraints, requiring a scheduling strategy. Classical real-time scheduling(实时调度) for Periodic Tasks contains Periodic Rate Monotonic (RM) as well as Earliest Deadline First (EDF). What’s more, tasks share resources and use mutual exclusion to guard access to those resources, resulting in Scheduling Anomalies(调度异常).
本文将讲述 Resources Sharing 给 real-time scheduling 带来的 Priority Inversion(优先级反转)异常,并将重点介绍对应的解决办法:Priority Inheritance Protocol (PIP)、Priority Ceiling Protocol (PCP)、Stack Resource Policy (SRP)。