Document that atexit execution order is undefined (#9788)
diff --git a/Doc/library/atexit.rst b/Doc/library/atexit.rst
index cc1051b..5b87b94 100644
--- a/Doc/library/atexit.rst
+++ b/Doc/library/atexit.rst
@@ -9,7 +9,9 @@
The :mod:`atexit` module defines functions to register and unregister cleanup
functions. Functions thus registered are automatically executed upon normal
-interpreter termination.
+interpreter termination. The order in which the functions are called is not
+defined; if you have cleanup operations that depend on each other, you should
+wrap them in a function and register that one. This keeps :mod:`atexit` simple.
Note: the functions registered via this module are not called when the program
is killed by a signal not handled by Python, when a Python fatal internal error