Delay-Bounded Scheduling

We provide a new characterization of scheduling nondeterminism by allowing deterministic schedulers to delay their next-scheduled task. In limiting the delays an otherwise-deterministic scheduler is allowed, we discover concurrency bugs efficiently—by exploring few schedules—and robustly—i.e., independent of the number of tasks, context switches, or buffered events. Our characterization elegantly applies to any systematic exploration (e.g., testing, model checking) of concurrent programs with dynamic task-creation. Additionally, we show that certain delaying schedulers admit efficient reductions from concurrent to sequential program analysis.