Priority Scheduling in SDL

In real-time systems, the capability to achieve short or even predictable reaction times is essential. In this paper, we take a pragmatic approach by proposing priority-based scheduling in SDL combined with a mechanism to suspend and resume SDL agents. More specifically, we define adequate syntactical extensions of SDL and show that they are compliant with the formal SDL semantics. We have implemented all proposed extensions in our SDL tool chain, consisting of SDL compiler, SDL runtime environment, and environment interfacing routines, thereby being compatible with model-driven development processes with SDL. In a series of runtime experiments on sensor nodes, we show that compared to customary SDL scheduling policies, priority scheduling with suspension of SDL agents indeed achieves significantly shortened reaction times.