Semantics-preserving and memory-efficient implementation of inter-task communication on static-priority or EDF schedulers

Abstract

In previous work, we have proposed a method of preserving the functional semantics of model-based designs by the use of static checks and a double-buffer protocol [12]. However, this is restricted to static, fixed-priority scheduling and for high-priority to low-priority communications requires a double buffer to be stored for each pair of communicating tasks. In this paper we extend the method to dynamic-priority scheduling in the form of earliest-deadlinefirst (EDF) scheduling and show that, although scheduling is dynamic, a static buffering scheme can still be used. We also suggest some memory optimizations of our protocol which still preserve the original functional semantics. Finally, we show how model checking can be used to prove correctness of the scheme.

Optimizing the Implementation of Communication in Synchronous Reactive Models

“…First, we provide a better bound for the case of priority-scheduled tasks activated with a minimum interarrival time (sporadic) or periodically, but with unknown phases. The bound shows how it is possible to improve with respect to [8] by leveraging the additional information about the minimum inter-arrival times and the task priorities, and applies to a more general (and practically useful) task model than [7]. Furthermore, our bound also applies to a more general application model than the bounds presented up to now, namely by allowing the case of multiple active instances of tasks at the same time, and communication links with arbitrary delays.…”

“…A different approach is used, in [7], where an optimum number of buffers for the case of only periodic tasks with known activation phases is obtained by simulating the execution of the tasks in the least common multiple of their periods to compute the required bound. Although this approach is optimal, it can only be used when all tasks are periodic and when their activation phases are known.…”

“…The meaning of the columns from the fifth to the last will be explained in the following section. We assume the activation phases of the tasks are unknown, hence, [7] is not applicable.…”

Synchronous Programming

“…This method has been developed in a number of recent works [33,34,35]. We only sketch the main ideas of the method here, and refer the reader to the above publications for details.…”

The Evolution of Real-Time Programming

“…The other difference between the two is the use of real-time scheduling and operating systems [21]. Only the buffered, i.e., LET portions of ZET programs have recently been shown to utilize real-time scheduling services such as EDF [37]. Recent research discussed in Section 7 shows the ZET and LET models also extend to some control systems distributed over networks.…”