[3.12] gh-116143: Fix race condition in pydoc _start_server (GH-116144) (#116415)

gh-116143: Fix race condition in pydoc _start_server (GH-116144)
(cherry picked from commit 02ee475ee3ce9468d44758df2cd79df9f0926303)

Co-authored-by: Itamar Oren <itamarost@gmail.com>

1 files changed, 4 insertions, 3 deletions

diff --git a/Lib/pydoc.py b/Lib/pydoc.py
index bf855b4..9a88123 100755
--- a/Lib/pydoc.py
+++ b/Lib/pydoc.py
@@ -2493,6 +2493,7 @@ 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."""
@@ -2525,9 +2526,9 @@ 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