get-semaphore

Arguments: gate

Gates can be used as semaphores. Each gate created by make-gate has an associated semaphore count that starts at 0. get-semaphore waits, if necessary, until the gate's count is greater than 0 and then decrements the count. If this makes the count 0, the gate is then closed, as well. Using get-semaphore and put-semaphore can be more efficient than using a generic process lock when mediating access to a work queue processed by several threads. mp:enqueue and mp:dequeue use semaphores internally to get the improved efficiency. See put-semaphore.

See multiprocessing.htm for general information on multiprocessing in Allegro CL.

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Created 2019.8.20.