diff --git a/Lib/logging/__init__.py b/Lib/logging/__init__.py
index 4c3dd15..79ec9ef 100644
--- a/Lib/logging/__init__.py
+++ b/Lib/logging/__init__.py
@@ -1226,19 +1226,23 @@
         """
         Add the specified handler to this logger.
         """
-        if not (hdlr in self.handlers):
-            self.handlers.append(hdlr)
+        _acquireLock()
+        try:
+            if not (hdlr in self.handlers):
+                self.handlers.append(hdlr)
+        finally:
+            _releaseLock()
 
     def removeHandler(self, hdlr):
         """
         Remove the specified handler from this logger.
         """
-        if hdlr in self.handlers:
-            hdlr.acquire()
-            try:
+        _acquireLock()
+        try:
+            if hdlr in self.handlers:
                 self.handlers.remove(hdlr)
-            finally:
-                hdlr.release()
+        finally:
+            _releaseLock()
 
     def hasHandlers(self):
         """
diff --git a/Misc/NEWS b/Misc/NEWS
index 489d6a9..c84a8ef 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -68,6 +68,8 @@
 Library
 -------
 
+- Issue #9945: logging: Fixed locking bugs in addHandler/removeHandler.
+
 - Issue #9936: Fixed executable lines' search in the trace module.
 
 - Issue #9790: Rework imports necessary for samefile and sameopenfile