Bounded Concurrent Time-Stamping

Abstract

We introduce concurrent time-stamping, a paradigm that allows processes to temporally order concurrent events in an asynchronous shared-memory system. Concurrent time-stamp systems are powerful tools for concurrency control, serving as the basis for solutions to coordination problems such as mutual exclusion, $\ell$-exclusion, randomized consensus, and multiwriter multireader atomic registers. Unfortunately, all previously known methods for implementing concurrent time-stamp systems have been theoretically unsatisfying since they require unbounded-size time-stamps---in other words, unbounded-size memory. This work presents the first bounded implementation of a concurrent time-stamp system, providing a modular unbounded-to-bounded transformation of the simple unbounded solutions to problems such as those mentioned above. It allows solutions to two formerly open problems, the bounded-probabilistic-consensus problem of Abrahamson and the fifo-$\ell$-exclusion problem of Fischer, Lynch, Burns and Borodin, and a more efficient construction of multireader multiwriter atomic registers.