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Semaphores are lightweight synchronization primitives used to constrain concurrent access to a shared resource
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They are widely used to implement other synchronization primitives and, whenever both are applicable, can be more efficient than condition variables
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A counting semaphore is a semaphore object that models a non-negative resource count
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A binary semaphore is a semaphore object that has only two states
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A binary semaphore should be more efficient than the default implementation of a counting semaphore with a unit resource count
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