A Concurrent Calculus with Atomic Transactions

Abstract

The Software Transactional Memory (STM) model is an original approach for controlling concurrent accesses to resources without the need for explicit lock-based synchronization mechanisms. A key feature of STMis to provide a way to group sequences of read and write actions inside atomic blocks, similar to database transactions, whose whole effect should occur atomically. In this paper, we investigate STM from a process algebra perspective and define an extension of asynchronous CCS with atomic blocks of actions. We show that the addition of atomic transactions results in a very expressive calculus, enough to easily encode other concurrent primitives such as guarded choice and multiset-synchronization (a la join-calculus). The correctness of our encodings is proved using a suitable notion of bisimulation equivalence. The equivalence is then applied to prove interesting "laws of transactions" and to obtain a simple normal form for transactions.