ABSTRACT
This chapter analyzes a different situation where tasks correspond to processes or threads and are scheduled by the operating system based on their current priority. Before discussing about priority assignment policies, it considers an important fact: what happens if, during the execution of a task at a given priority, another task with higher priority becomes ready? Scheduling analysis refers to two broad categories in task priority assignment to tasks: Fixed Priority and Variable Priority. Rate monotonic (RM) is a policy for fixed-priority assignment in periodic tasks, which assigns a priority that is inversely proportional to the task period: the shorter the task period, the higher its priority. The Earliest Deadline First (EDF) algorithm selects tasks according to their absolute deadlines. The chapter introduces the basics of task based scheduling, providing two "optimal" scheduling procedures: RM for fixed task priority assignment, and EDF for dynamic task priority assignment.
