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multiprocessing.queues.SimpleQueue should have a close() method. This is needed to explicitly release the two file descriptors of the Pipe used internally. Without it, the file descriptors leak if a reference to the SimpleQueue object happens to stay around for longer than expected (e.g. in a reference cycle, or with PyPy).
I think the following would do:
diff -r 0b72fd1a7641 lib-python/2.7/multiprocessing/queues.py
--- a/lib-python/2.7/multiprocessing/queues.py Sun Jul 16 13:41:28 2017 +0200
+++ b/lib-python/2.7/multiprocessing/queues.py Wed Jul 19 10:45:03 2017 +0200
@@ -358,6 +358,11 @@
 self._wlock = Lock()
 self._make_methods()
+ def close(self):
+ # PyPy extension: CPython doesn't have this method!
+ self._reader.close()
+ self._writer.close()
+
 def empty(self):
 return not self._reader.poll()