Index: Lib/mutex.py
===================================================================
--- Lib/mutex.py	(revisión: 60989)
+++ Lib/mutex.py	(copia de trabajo)
@@ -13,12 +13,14 @@
 """
 
 from collections import deque
+from threading import Lock
 
 class mutex:
     def __init__(self):
         """Create a new mutex -- initially unlocked."""
         self.locked = 0
         self.queue = deque()
+        self.lock = Lock()
 
     def test(self):
         """Test the locked bit of the mutex."""
@@ -27,11 +29,12 @@
     def testandset(self):
         """Atomic test-and-set -- grab the lock if it is not set,
         return True if it succeeded."""
-        if not self.locked:
-            self.locked = 1
-            return True
-        else:
-            return False
+        with self.lock:
+            if not self.locked:
+                self.locked = 1
+                return True
+            else:
+                return False
 
     def lock(self, function, argument):
         """Lock a mutex, call the function with supplied argument
@@ -45,8 +48,12 @@
     def unlock(self):
         """Unlock a mutex.  If the queue is not empty, call the next
         function with its argument."""
-        if self.queue:
-            function, argument = self.queue.popleft()
+        call = False
+        with self.lock:
+            if self.queue:
+                call = True
+                function, argument = self.queue.popleft()
+            else:
+                self.locked = 0
+        if call:
             function(argument)
-        else:
-            self.locked = 0