bpo-31326: ProcessPoolExecutor waits for the call queue thread (#3265)
* bpo-31326: ProcessPoolExecutor waits for the call queue thread
concurrent.futures.ProcessPoolExecutor.shutdown() now explicitly
closes the call queue. Moreover, shutdown(wait=True) now also join
the call queue thread, to prevent leaking a dangling thread.
* Fix for shutdown() being called twice.
diff --git a/Lib/concurrent/futures/process.py b/Lib/concurrent/futures/process.py
index 03b28ab..50ee296 100644
--- a/Lib/concurrent/futures/process.py
+++ b/Lib/concurrent/futures/process.py
@@ -507,7 +507,11 @@
# To reduce the risk of opening too many files, remove references to
# objects that use file descriptors.
self._queue_management_thread = None
- self._call_queue = None
+ if self._call_queue is not None:
+ self._call_queue.close()
+ if wait:
+ self._call_queue.join_thread()
+ self._call_queue = None
self._result_queue = None
self._processes = None
shutdown.__doc__ = _base.Executor.shutdown.__doc__