Implementing and Verifying EDF Preemption-Level Resource Control

To support Earliest Deadline First (EDF) dispatching of application tasks the Ada language has had to incorporate Baker's Stack Resource Protocol (SRP). This protocol has proved problematic both in terms of its language definition and implementation. This paper proposes a means of verifying the implementation of complex language features. It describes a prototype tool that allows a comparison to be made between the output of an executing program and a diverse simulator that directly implements EDF+SRP. The tool creates a collection of cases (scenarios); for each of which a program is automatically generated (and executed) and a separate simulation script produced. Tests on an existing run-time for Ada has shown that in certain circumstances an Ada pro-gram and its corresponding simulation diverge.