Challenges with Probabilities in Response-Time Analysis of Real-Time Systems

The Worst-Case Response-Time (WCRT) of a task is the maximum time after activation within which the task will finish its execution. The WCRT is constructed by the Worst-Case Execution Time (WCET) of the task itself, as well as the interference of other higher priority tasks, along with potential blocking by lower priority tasks if blocking is allowed by the task model. The interference of other higher priority tasks is constructed using the higher priority tasks’ WCET and period. Hence, the WCET of tasks in a real-time system is central in deriving the WCRT of a particular task. Usually the WCET is derived using static analysis of the source code in a context of a specific processor on which the task is to execute on. The context is needed to get the correct timing characteristics.