Deadlock control with Ada95

Abstract

The Ada programming language is unique in its high-level concurrency facilities, supported by a secure and powerful set of programming constructs. Ada 95 now has additional capabilities, specifically the protected type construct.Although the Ada rendezvous is prone to deadlock, a careful discipline can ensure that this type of dead state does not occur. Restricting task communication assists in preventing deadlock, yet such restrictions may be too limiting and/or too inefficient for an application. Indeed, several researchers have suggested that deadlock should not be prevented, but monitored and corrected during testing and/or run time.This paper takes the position that deadlock should be prevented by following specific guidelines in the use of the rendezvous. We define deadlock, show how it can occur with Ada tasks, and outline mechanisms that are appropriate for its control.