From fcdb0a37a859ad564870d78d06705f36122fe006 Mon Sep 17 00:00:00 2001
From: Qing Wang <kingchin1218@gmail.com>
Date: Wed, 5 Jul 2023 12:27:05 +0800
Subject: [PATCH] Fix reset variables in thread safe way.

---
 fed/cleanup.py | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/fed/cleanup.py b/fed/cleanup.py
index 495ff0d..a770094 100644
--- a/fed/cleanup.py
+++ b/fed/cleanup.py
@@ -67,10 +67,6 @@ def _signal_exit():
             break
 
     logger.info('Check sending thread was exited.')
-    global _check_send_thread
-    _check_send_thread = None
-    logger.info('Clearing sending queue.')
-    _sending_obj_refs_q = None
 
 
 def _main_thread_monitor():
@@ -117,3 +113,9 @@ def wait_sending():
     if _check_send_thread:
         notify_to_exit()
         _check_send_thread.join()
+        _check_send_thread = None
+
+        # It's safe to reset `_sending_obj_refs_q` as another
+        # thread is stoped.
+        global _sending_obj_refs_q
+        _sending_obj_refs_q = None