bpo-44422: Fix threading.enumerate() reentrant call (GH-26727)

The threading.enumerate() function now uses a reentrant lock to
prevent a hang on reentrant call.

https://github.com/python/cpython/commit/243fd01047ddce1a7eb0f99a49732d123e942c63

Resolves: rhbz#1959459

diff --git a/Lib/threading.py b/Lib/threading.py
index 0ab1e46..7ab9ad8 100644
--- a/Lib/threading.py
+++ b/Lib/threading.py
@@ -727,8 +727,11 @@ _counter() # Consume 0 so first non-main thread has id 1.
 def _newname(template="Thread-%d"):
     return template % _counter()
 
-# Active thread administration
-_active_limbo_lock = _allocate_lock()
+# Active thread administration.
+#
+# bpo-44422: Use a reentrant lock to allow reentrant calls to functions like
+# threading.enumerate().
+_active_limbo_lock = RLock()
 _active = {}    # maps thread id to Thread object
 _limbo = {}
 _dangling = WeakSet()
@@ -1325,7 +1328,7 @@ def _after_fork():
     # Reset _active_limbo_lock, in case we forked while the lock was held
     # by another (non-forked) thread.  http://bugs.python.org/issue874900
     global _active_limbo_lock, _main_thread
-    _active_limbo_lock = _allocate_lock()
+    _active_limbo_lock = RLock()
 
     # fork() only copied the current thread; clear references to others.
     new_active = {}