From 02ee475ee3ce9468d44758df2cd79df9f0926303 Mon Sep 17 00:00:00 2001
From: Itamar Oren <itamarost@gmail.com>
Date: Wed, 6 Mar 2024 06:39:51 -0800
Subject: [PATCH] gh-116143: Fix race condition in pydoc _start_server
 (#116144)

---
 Lib/pydoc.py                                               | 7 ++++---
 .../Library/2024-03-05-20-53-34.gh-issue-116143.sww6Zl.rst | 3 +++
 2 files changed, 7 insertions(+), 3 deletions(-)
 create mode 100644 Misc/NEWS.d/next/Library/2024-03-05-20-53-34.gh-issue-116143.sww6Zl.rst

diff --git a/Lib/pydoc.py b/Lib/pydoc.py
index 407c0205c7a..08fd7aba7c9 100755
--- a/Lib/pydoc.py
+++ b/Lib/pydoc.py
@@ -2504,6 +2504,7 @@ def _start_server(urlhandler, hostname, port):
             threading.Thread.__init__(self)
             self.serving = False
             self.error = None
+            self.docserver = None
 
         def run(self):
             """Start the server."""
@@ -2536,9 +2537,9 @@ def _start_server(urlhandler, hostname, port):
 
     thread = ServerThread(urlhandler, hostname, port)
     thread.start()
-    # Wait until thread.serving is True to make sure we are
-    # really up before returning.
-    while not thread.error and not thread.serving:
+    # Wait until thread.serving is True and thread.docserver is set
+    # to make sure we are really up before returning.
+    while not thread.error and not (thread.serving and thread.docserver):
         time.sleep(.01)
     return thread
 
diff --git a/Misc/NEWS.d/next/Library/2024-03-05-20-53-34.gh-issue-116143.sww6Zl.rst b/Misc/NEWS.d/next/Library/2024-03-05-20-53-34.gh-issue-116143.sww6Zl.rst
new file mode 100644
index 00000000000..07aa312ee25
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2024-03-05-20-53-34.gh-issue-116143.sww6Zl.rst
@@ -0,0 +1,3 @@
+Fix a race in pydoc ``_start_server``, eliminating a window in which
+``_start_server`` can return a thread that is "serving" but without a
+``docserver`` set.