Implementing Priority Inheritance Algorithms in an Ada Runtime System

Abstract

This paper presents a high-level design-in the form of necessary data structures, mechanisms, and algorithms-for implementing the basic priority inheritance and priority ceiling protocols in an Ada runtime system. Both of these protocols solve the unbounded priority inversion problem, where a high-priority task can be forced to wait for a lower priority task for an arbitrary duration of time. The protocols and their implementation also address the issues of non-deterministic selection of open alternatives and FIFO entry call queues. These protocols allow the timing analysis of a given set of Ada tasks in order to guarantee their deadlines in real-time systems. Importantly, it is possible to implement the protocols within the current semantics of the Ada language given the interpretations of Ada rules described by Goodenough and Sha in the Software Engineering Institute Technical Report 33 (1988). Strategies and possible alternatives are discussed for implementing these protocols in an Ada runtime system targeted to a uniprocessor execution environment.

A stack-based resource allocation policy for realtime processes

“…(If the SRP is applied to a system in which runtime stacks are not shared, it is still helpful to think of all the jobs that have started executing, but have not finished, as occupying positions on an imaginary stack, which is ordered by preemption level.) 4 …”

“…One approach uses off-line scheduling [12,7], based on deterministic scheduling theory [6]. A more flexible approach, exemplified by [4], uses on-line preeemptive priority scheduling and is based on the work of [ll]. This paper is motivated by concern for another aspect of adapting the process model to hard realtime requirements: the efficient allocation of memory for process' runtime stacks.…”

Rate Monotonic Analysis for Real-Time Systems

“…In addition, we have addressed the associated hardware scheduling support [10] [22], implications for Ada scheduling rules [5], algorithm implementation in an Ada runtime system [1], and schedulability analysis of input/output paradigms [7]. Finally, we also have performed a number of design and analysis experiments to test the viability of the theory [2,13]. Together, these results constitute a reasonably comprehensive set of analytical methods for real-time system engineering.…”

Object technology for the integration of the infrastructure, data manager, and tracker for command and control applications

“…The GRL queue and LIFO PTL are described in the implementation of [BR89]. The GRL is a priority queue of currently held I O C~S (LRD structures) enqueued in highest to lowest order based on the priority ceiling of the lock.…”