The complexity of obstruction-free implementations

Hagit Attiya, Rachid Guerraoui, Danny Hendler, Petr Kuznetsov

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


Obstruction-free implementations of concurrent objects are optimized for the common case where there is no step contention, and were recently advocated as a solution to the costs associated with synchronization without locks. In this article, we study this claim and this goes through precisely defining the notions of obstruction-freedom and step contention. We consider several classes of obstruction-free implementations, present corresponding generic object implementations, and prove lower bounds on their complexity. Viewed collectively, our results establish that the worst-case operation time complexity of obstruction-free implementations is high, even in the absence of step contention. We also show that lock-based implementations are not subject to some of the time-complexity lower bounds we present.

Original languageEnglish
Article number24
JournalJournal of the ACM
Issue number4
StatePublished - 1 Jun 2009


  • Lower bounds
  • Memory contention
  • Perturbable objects
  • Shared memory
  • Solo-fast implementations
  • Step contention

ASJC Scopus subject areas

  • Software
  • Control and Systems Engineering
  • Information Systems
  • Hardware and Architecture
  • Artificial Intelligence


Dive into the research topics of 'The complexity of obstruction-free implementations'. Together they form a unique fingerprint.

Cite this