Towards a necessary and sufficient condition for wait-free synchronization

Abstract

We define a class of shared objects called snapshot objects, and give a necessary and sufficient condition for the existence of a waitfree implementation of such objects from atomic registers. Snapshot objects can be accessed by means of a read operation that returns the entire object state, or by a set of operations that do not return values. Our condition for the existence of a wait-free implementation requires that for any pair of operation invocations, either the two invocations commute or one overwrites the other.