diff --git a/Lib/threading.py b/Lib/threading.py
--- a/Lib/threading.py
+++ b/Lib/threading.py
@@ -2,6 +2,8 @@
 
 import sys as _sys
 import _thread
+from _collections import deque as _deque
+from itertools import islice as _islice
 
 from time import sleep as _sleep
 try:
@@ -146,7 +148,7 @@
             self._is_owned = lock._is_owned
         except AttributeError:
             pass
-        self._waiters = []
+        self._waiters = _deque()
 
     def __enter__(self):
         return self._lock.__enter__()
@@ -217,7 +219,7 @@
         if not self._is_owned():
             raise RuntimeError("cannot notify on un-acquired lock")
         __waiters = self._waiters
-        waiters = __waiters[:n]
+        waiters = list(_islice(__waiters, n))
         if not waiters:
             return
         for waiter in waiters: