diff --git a/Lib/multiprocessing/pool.py b/Lib/multiprocessing/pool.py --- a/Lib/multiprocessing/pool.py +++ b/Lib/multiprocessing/pool.py @@ -321,7 +321,11 @@ @staticmethod def _handle_workers(pool): - while pool._worker_handler._state == RUN and pool._state == RUN: + thread = threading.current_thread() + + # Keep maintaining workers until the cache gets drained, unless the pool + # is terminated. + while thread._state == RUN or (pool._cache and thread._state != TERMINATE): pool._maintain_pool() time.sleep(0.1) # send sentinel to stop workers diff --git a/Lib/test/test_multiprocessing.py b/Lib/test/test_multiprocessing.py --- a/Lib/test/test_multiprocessing.py +++ b/Lib/test/test_multiprocessing.py @@ -1266,6 +1266,20 @@ p.close() p.join() + def test_pool_worker_lifetime_early_close(self): + # Issue #10332: closing a pool whose workers have limited lifetimes + # before all the tasks completed would make join() hang. + p = multiprocessing.Pool(3, maxtasksperchild=1) + results = [] + for i in range(6): + results.append(p.apply_async(sqr, (i, 0.3))) + p.close() + p.join() + # check the results + for (j, res) in enumerate(results): + self.assertEqual(res.get(), sqr(j)) + + # # Test that manager has expected number of shared objects left #