Polling in concurrent programming

Abstract

Hoare introduced the concept of polling in his Communicating Sequential Processes (CSP) to handle nondeterministic message communication in distributed and concurrent programming. In order to introduce the polling concept effectively in a programming language, the problems of simultaneous polling, effective termination, busy waiting, and expressive power in one-to-many or many-to-one communication must be solved. This paper discusses the concept of polling, the details about the problems, and how a new concurrent programming language, COPL, solves the problems. COPL introduces a general algorithm to establish a hierarchical relationship between two communicating processes, an efficient mechanism to handle polling termination, a flexible polling to avoid busy waiting, and implicit polling to add asymmetry in the language for more expressive power. [Key words: concurrent programming, programming languages, polling, nondeterminism, and distributed systems]