From 6e32c5391c5e03723d5d9cf286ac7779eae3c81e Mon Sep 17 00:00:00 2001
From: Victor Stinner <victor.stinner@gmail.com>
Date: Sat, 19 Aug 2017 01:44:00 +0200
Subject: [PATCH 1/2] bpo-31238: pydoc ServerThread.stop() now joins itself

ServerThread.stop() now joins itself to wait until
DocServer.serve_until_quit() completes and then explicitly sets
its docserver attribute to None to break a reference cycle.
---
 Lib/pydoc.py | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/Lib/pydoc.py b/Lib/pydoc.py
index 376c4459fe6b00e..5edc77005a87140 100644
--- a/Lib/pydoc.py
+++ b/Lib/pydoc.py
@@ -2297,6 +2297,10 @@ def ready(self, server):
         def stop(self):
             """Stop the server and this thread nicely"""
             self.docserver.quit = True
+            self.join()
+            # explicitly break a reference cycle: DocServer.callback
+            # has indirectly a reference to ServerThread.
+            self.docserver = None
             self.serving = False
             self.url = None
 

From d080a8bb55bb8b153945a4a3c57077aa30f0a7e7 Mon Sep 17 00:00:00 2001
From: Victor Stinner <victor.stinner@gmail.com>
Date: Mon, 21 Aug 2017 12:31:59 +0200
Subject: [PATCH 2/2] Add NEWS.d entry

---
 .../next/Library/2017-08-21-12-31-53.bpo-31238.Gg0LRH.rst      | 3 +++
 1 file changed, 3 insertions(+)
 create mode 100644 Misc/NEWS.d/next/Library/2017-08-21-12-31-53.bpo-31238.Gg0LRH.rst

diff --git a/Misc/NEWS.d/next/Library/2017-08-21-12-31-53.bpo-31238.Gg0LRH.rst b/Misc/NEWS.d/next/Library/2017-08-21-12-31-53.bpo-31238.Gg0LRH.rst
new file mode 100644
index 000000000000000..3e1cd130100376d
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2017-08-21-12-31-53.bpo-31238.Gg0LRH.rst
@@ -0,0 +1,3 @@
+pydoc: the stop() method of the private ServerThread class now waits until
+DocServer.serve_until_quit() completes and then explicitly sets its
+docserver attribute to None to break a reference cycle.