On the Implementation of Concurrent Objects

• Published in: Dependable and Historic Computing pp. 453 - 478
• Main Author: Raynal, Michel
• Format: Book Chapter
• Language: English
• Published: Berlin, Heidelberg Springer Berlin Heidelberg 2011
• Series: Lecture Notes in Computer Science
• Subjects: Asynchronous shared memory system; Atomicity; Compare&Swap; Consensus number; Consensus object; Enriched system; Failure detector; Linearizability; Lock; Lock-freedom; Non-Blocking; Obstruction-freedom; Process crash; Progress condition; Queue; Read/Write atomic register; Set; Snapshot; Splitter; Synchronization; System boosting; Timestamp; Wait-free algorithm
• ISBN: 9783642245404; 3642245404
• ISSN: 0302-9743; 1611-3349
• DOI: 10.1007/978-3-642-24541-1_33

The implementation of objects shared by concurrent processes, with provable safety and liveness guarantees, is a fundamental issue of concurrent programming in shared memory systems. It is now largely accepted that linearizability (or atomicity) is an appropriate consistency condition for concurrent objects. On the liveness side, progress conditions (mainly absence of deadlock or the stronger absence of starvation) have been stated and investigated for a long time and are now well-mastered. The situation is different in asynchronous shared memory systems prone to process failures. This paper visits three progress conditions suited to concurrent objects in presence of failures, namely obstruction-freedom, non-blocking and wait-freedom. To that end, the paper also visits appropriate computation models and paradigm problems to illustrate this family of progress conditions. The paper has consequently an introductory and survey flavor. Its aim is to help people better understand the difficulties, subtleties and beauties encountered when one has to implement concurrent objects despite the net effect of asynchrony and failures.