diff --git a/Lib/logging/__init__.py b/Lib/logging/__init__.py
index 5922ed3..c8e5ac2 100644
--- a/Lib/logging/__init__.py
+++ b/Lib/logging/__init__.py
@@ -1497,22 +1497,28 @@
     using sys.stdout or sys.stderr), whereas FileHandler closes its stream
     when the handler is closed.
     """
-    if len(root.handlers) == 0:
-        filename = kwargs.get("filename")
-        if filename:
-            mode = kwargs.get("filemode", 'a')
-            hdlr = FileHandler(filename, mode)
-        else:
-            stream = kwargs.get("stream")
-            hdlr = StreamHandler(stream)
-        fs = kwargs.get("format", BASIC_FORMAT)
-        dfs = kwargs.get("datefmt", None)
-        fmt = Formatter(fs, dfs)
-        hdlr.setFormatter(fmt)
-        root.addHandler(hdlr)
-        level = kwargs.get("level")
-        if level is not None:
-            root.setLevel(level)
+    # Add thread safety in case someone mistakenly calls
+    # basicConfig() from multiple threads
+    _acquireLock()
+    try:
+        if len(root.handlers) == 0:
+            filename = kwargs.get("filename")
+            if filename:
+                mode = kwargs.get("filemode", 'a')
+                hdlr = FileHandler(filename, mode)
+            else:
+                stream = kwargs.get("stream")
+                hdlr = StreamHandler(stream)
+            fs = kwargs.get("format", BASIC_FORMAT)
+            dfs = kwargs.get("datefmt", None)
+            fmt = Formatter(fs, dfs)
+            hdlr.setFormatter(fmt)
+            root.addHandler(hdlr)
+            level = kwargs.get("level")
+            if level is not None:
+                root.setLevel(level)
+    finally:
+        _releaseLock()
 
 #---------------------------------------------------------------------------
 # Utility functions at module level.