bpo-41503: Fix race between setTarget and flush in logging.handlers.MemoryHandler (GH-21765)

1 files changed, 5 insertions, 1 deletions

diff --git a/Lib/logging/handlers.py b/Lib/logging/handlers.py
index 4a120e9f1e..867ef4ebc7 100644
--- a/Lib/logging/handlers.py
+++ b/Lib/logging/handlers.py
@@ -1324,7 +1324,11 @@ class MemoryHandler(BufferingHandler):
         """
         Set the target handler for this handler.
         """
-        self.target = target
+        self.acquire()
+        try:
+            self.target = target
+        finally:
+            self.release()
 
     def flush(self):
         """