THE NOTION OF PRIORITY IN REAL-TIME PROGRAMMING-LANGUAGES

Embedded systems often have to operate within hard real-time constraints. Periodic and aperiodic processes must be scheduled to meet specified deadlines, the failure to do so being seen as an error condition. Priority is one means of representing scheduling information in a concurrent real-time programming language. Following the introduction and criticism of the facilities provided by the programming language Ada, the requirements for deadline scheduling and resource scheduling using priorities are introduced. Unfortunately these requirements, are, in some important particulars, contradictory. These contradictions are investigated and methods of resolving them are proposed. © 1990.