Phasers: a Unified Deadlock-Free Construct for Collective and Point-to-point Synchronization

Coordination and synchronization of parallel tasks is a ma-jor source of complexity in parallel programming. These constructs take many forms in practice including mutual exclusion in accesses to shared resources, termination detec-tion of child tasks, collective barrier synchronization, and point-to-point synchronization. In this paper, we introduce phasers, a new coordination construct that unifies collec-tive and point-to-point synchronizations. We establish two safety properties for phasers: deadlock-freedom and phase-ordering. Performance results obtained from a portable im-plementation of phasers on three different SMP platforms demonstrate that phasers can deliver superior performance to existing barrier implementations, in addition to the pro-ductivity benefits that result from their generality and safety properties