Summary: This is a preprint of a paper that will appear in the Proceedings of the 24th
Conference on Foundations of Software Technology and Theoretical Computer
Science (FSTTCS 2004), Chennai, India, December 16, 2004 c Springer-Verlag.
Toward a Grainless Semantics for
John C. Reynolds
Carnegie Mellon University
Abstract. Conventional semantics for shared-variable concurrency suf-
fers from the "grain of time" problem, i.e., the necessity of specifying a
default level of atomicity. We propose a semantics that avoids any such
choice by regarding all interference that is not controlled by explicit crit-
ical regions as catastrophic. It is based on three principles:
Operations have duration and can overlap one another during exe-
If two overlapping operations touch the same location, the meaning
of the program execution is "wrong".
If, from a given starting state, execution of a program can give