Effects for cooperable and serializable threads

  • Authors:

  • Jaeheon Yi;Cormac Flanagan

  • Affiliations:

  • University of California at Santa Cruz, Santa Cruz, CA, USA;University of California at Santa Cruz, Santa Cruz, CA, USA

  • Venue:
  • Proceedings of the 5th ACM SIGPLAN workshop on Types in language design and implementation
  • Year:
  • 2010

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Abstract

Reasoning about the correctness of multithreaded programs is complicated by the potential for unexpected interference between threads. Previous work on controlling thread interference focused on verifying race freedom and/or atomicity. Unfortunately, race freedom is insufficient to prevent unintended thread interference. The notion of atomic blocks provides more semantic guarantees, but offers limited benefits for non-atomic code and it requires bi-modal sequential/multithreaded reasoning (depending on whether code is inside or outside an atomic block). This paper proposes an alternative strategy that uses yield annotations to control thread interference, and we present an effect system for verifying the correctness of these yield annotations. The effect system guarantees that for any preemptively-scheduled execution of a well-formed program, there is a corresponding cooperative execution with equivalent behavior in which context switches happen only at yield annotations. This effect system enables cooperative reasoning: the programmer can adopt the simplifying assumption of cooperative scheduling, even though the program still executes with preemptive scheduling and/or true concurrency on multicore processors. Unlike bimodal sequential/multithreaded reasoning, cooperative reasoning can be applied to all program code.