ENH backport cpython modification in loky (#246)

Author: tomMoral

CHANGES.md

@@ -20,6 +20,10 @@
   ``resource_tracker`` will proceed to unlink the resource. Previously, resource
   unlinking by the ``resource_tracker`` was only done for leaked resources at
   interpreter exit (#228).
+- Fix `shutdown(wait=False)` that was potentially leading to deadlocks and froze
+  interpreters (#246).
+- Backport `ExecutorManagerThread` from cpython to refactor
+  `_queue_management_thread` and ease maintenance (#246).
 
 ### 2.6.0 - 2019-09-18
 

loky/backend/queues.py

@@ -209,6 +209,10 @@ def __init__(self, reducers=None, ctx=None):
         # Add possiblity to use custom reducers
         self._reducers = reducers
 
+    def close(self):
+        self._reader.close()
+        self._writer.close()
+
     # Use custom queue set/get state to be able to reduce the custom reducers
     def __getstate__(self):
         assert_spawning(self)