A TimeStamp based Multi-version STM Protocol that satisfies Opacity and Multi-Version Permissiveness

TL;DR

This paper introduces a new timestamp-based multi-version STM protocol that guarantees opacity and mv-permissiveness, with formal proofs of correctness and a garbage collection method.

Contribution

It presents the first formally proven multi-version STM system satisfying both opacity and mv-permissiveness, including a verified garbage collection process.

Findings

The proposed STM system guarantees opacity.

The system is mv-permissive, avoiding aborts for read-only transactions.

Formal proofs validate the correctness of the protocol and garbage collection.

Abstract

Software Transactional Memory Systems (STM) are a promising alternative to lock based systems for concurrency control in shared memory systems. In multiversion STM systems, each write on a transaction object produces a new version of that object. The advantage obtained by storing multiple versions is that one can ensure that read operations do not fail. Opacity is a commonly used correctness criterion for STM systems. Multi-Version permissive STM system never aborts a read-only transaction. Although many multi-version STM systems have been proposed, to the best of our knowledge none of them have been formally proved to satisfy opacity. In this paper we present a time-stamp based multiversion STM system that satisfies opacity and mv-permissiveness. We formally prove the correctness of the proposed STM system. We also present garbage collection procedure which deletes unwanted versions of the transaction objects and formally prove it correctness.