Summary
Sometimes computers have jobs that pause and wait during their work, making it tricky to schedule them so they always finish on time. Wang and colleagues proposed a method to check if these jobs can be scheduled safely, but the authors of this paper found an example that breaks that method. They also showed that one part of Wang's method that was supposed to be necessary is actually incorrect. This means the previous scheduling checks for these pausing tasks need to be reconsidered.
What this means in practice
- •For real-time system engineers: Avoid using the flawed schedulability tests from Wang et al. when verifying timing guarantees in systems with self-suspending tasks under EDF-like scheduling.
- •For embedded software developers: Reassess timing analysis methods for applications with tasks that pause, preventing reliance on incorrect necessary and sufficient conditions.
Authors
Michael Frichert, Mario Günzel, Marion Sudvarg, Jian-Jia Chen
Abstract
This paper provides a counterexample of the sufficient schedulability test for self-suspending real-time tasks under EDF-Like scheduling given by Wang et al. in Theorem 11 of IEEE Transactions on Computers, 74(7):2364-2375, 2025. This paper also shows that their necessary condition is unsound.