[3.13] gh-122187: Avoid TSan reported race in run_udp_echo_server (GH-122189) (#122263)

miss-islington · colesbury · web-flow · commit 977c7992860a · 2024-07-25T08:42:38.000Z
gh-122187: Avoid TSan reported race in `run_udp_echo_server` (GH-122189) TSan doesn't fully recognize the synchronization via I/O, so ensure that socket name is retrieved earlier and use a different socket for sending the "STOP" message. (cherry picked from commit 2f74b70) Co-authored-by: Sam Gross <colesbury@gmail.com>
diff --git a/Lib/test/test_asyncio/utils.py b/Lib/test/test_asyncio/utils.py
@@ -301,12 +301,17 @@ def run_udp_echo_server(*, host='127.0.0.1', port=0):
     family, type, proto, _, sockaddr = addr_info[0]
     sock = socket.socket(family, type, proto)
     sock.bind((host, port))
+    sockname = sock.getsockname()
     thread = threading.Thread(target=lambda: echo_datagrams(sock))
     thread.start()
     try:
-        yield sock.getsockname()
+        yield sockname
     finally:
-        sock.sendto(b'STOP', sock.getsockname())
+        # gh-122187: use a separate socket to send the stop message to avoid
+        # TSan reported race on the same socket.
+        sock2 = socket.socket(family, type, proto)
+        sock2.sendto(b'STOP', sockname)
+        sock2.close()
         thread.join()
 
 
