Runtime system support for data-oriented synchronization in Ada-9X

Abstract

Ada is a high level language, designed for implementing large embedded systems. It became an ANSI standard in 1983 and in 1988 the Ada Joint Program Office established the ADA-9X project for the revision of the Ada standard. One of the specific areas addressed by the revision team deals with requirements posed by real-time applications and introduces a new building block for real-time Ada: the protected record. Protected records provide a low level data-oriented synchronization mechanism and are a primary support for real-time systems. They can be used to efficiently program solutions for real-time problems such as mutual exclusion, conditionally shared data, counting semaphores and signals. This paper compares two different approaches for the solution of a classical real-time problem: conditional critical regions. The first solution uses Ada83 tasking and the second one uses Ada9X protected records. Finally we will discuss the runtime support and some implementation issues for protected records on multiprocessor target systems.