From 52be4235517fd277c9ee17d7ee4f601e7c70c464 Mon Sep 17 00:00:00 2001
From: Antoine Pitrou <antoine@python.org>
Date: Wed, 17 Jan 2018 13:04:59 +0100
Subject: [PATCH] bpo-32576: use queue.SimpleQueue in critical places

Where a queue may be invoked from a weakref callback, we need
to use the reentrant SimpleQueue.
---
 Lib/concurrent/futures/thread.py              |  2 +-
 Lib/multiprocessing/pool.py                   | 19 +++++++++++--------
 .../2018-01-17-13-04-16.bpo-32576.iDL09t.rst  |  2 ++
 3 files changed, 14 insertions(+), 9 deletions(-)
 create mode 100644 Misc/NEWS.d/next/Library/2018-01-17-13-04-16.bpo-32576.iDL09t.rst

diff --git a/Lib/concurrent/futures/thread.py b/Lib/concurrent/futures/thread.py
index 2e7100bc3529d4..6e22950a157db6 100644
--- a/Lib/concurrent/futures/thread.py
+++ b/Lib/concurrent/futures/thread.py
@@ -128,7 +128,7 @@ def __init__(self, max_workers=None, thread_name_prefix='',
             raise TypeError("initializer must be a callable")
 
         self._max_workers = max_workers
-        self._work_queue = queue.Queue()
+        self._work_queue = queue.SimpleQueue()
         self._threads = set()
         self._broken = False
         self._shutdown = False
diff --git a/Lib/multiprocessing/pool.py b/Lib/multiprocessing/pool.py
index b1ee725fac6c25..3e9a0d6b48679f 100644
--- a/Lib/multiprocessing/pool.py
+++ b/Lib/multiprocessing/pool.py
@@ -156,7 +156,7 @@ def __init__(self, processes=None, initializer=None, initargs=(),
                  maxtasksperchild=None, context=None):
         self._ctx = context or get_context()
         self._setup_queues()
-        self._taskqueue = queue.Queue()
+        self._taskqueue = queue.SimpleQueue()
         self._cache = {}
         self._state = RUN
         self._maxtasksperchild = maxtasksperchild
@@ -802,15 +802,18 @@ def __init__(self, processes=None, initializer=None, initargs=()):
         Pool.__init__(self, processes, initializer, initargs)
 
     def _setup_queues(self):
-        self._inqueue = queue.Queue()
-        self._outqueue = queue.Queue()
+        self._inqueue = queue.SimpleQueue()
+        self._outqueue = queue.SimpleQueue()
         self._quick_put = self._inqueue.put
         self._quick_get = self._outqueue.get
 
     @staticmethod
     def _help_stuff_finish(inqueue, task_handler, size):
-        # put sentinels at head of inqueue to make workers finish
-        with inqueue.not_empty:
-            inqueue.queue.clear()
-            inqueue.queue.extend([None] * size)
-            inqueue.not_empty.notify_all()
+        # drain inqueue, and put sentinels at its head to make workers finish
+        try:
+            while True:
+                inqueue.get(block=False)
+        except queue.Empty:
+            pass
+        for i in range(size):
+            inqueue.put(None)
diff --git a/Misc/NEWS.d/next/Library/2018-01-17-13-04-16.bpo-32576.iDL09t.rst b/Misc/NEWS.d/next/Library/2018-01-17-13-04-16.bpo-32576.iDL09t.rst
new file mode 100644
index 00000000000000..143a83e0fcc2b1
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2018-01-17-13-04-16.bpo-32576.iDL09t.rst
@@ -0,0 +1,2 @@
+Use queue.SimpleQueue() in places where it can be invoked from a weakref
+callback.