[Python-checkins] bpo-31326: ProcessPoolExecutor waits for the call queue thread (#3265)

[Victor Stinner]

https://github.com/python/cpython/commit/b713adf27a76b5df95e3ee5f85f9064a2763ae35
commit: b713adf27a76b5df95e3ee5f85f9064a2763ae35
branch: master
author: Victor Stinner <victor.stinner at gmail.com>
committer: GitHub <noreply at github.com>
date: 2017-09-02T00:25:11+02:00
summary:

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.

files:
A Misc/NEWS.d/next/Library/2017-09-01-18-48-06.bpo-31326.TB05tV.rst
M Lib/concurrent/futures/process.py

diff --git a/Lib/concurrent/futures/process.py b/Lib/concurrent/futures/process.py
index 03b28ab5d68..50ee296ac89 100644
--- a/Lib/concurrent/futures/process.py
+++ b/Lib/concurrent/futures/process.py
@@ -507,7 +507,11 @@ def shutdown(self, wait=True):
         # 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__
diff --git a/Misc/NEWS.d/next/Library/2017-09-01-18-48-06.bpo-31326.TB05tV.rst b/Misc/NEWS.d/next/Library/2017-09-01-18-48-06.bpo-31326.TB05tV.rst
new file mode 100644
index 00000000000..ea0ff2b4580
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2017-09-01-18-48-06.bpo-31326.TB05tV.rst
@@ -0,0 +1,3 @@
+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.