Make sure that tight loop interruption test terminates eventually.

Author: markshannon

Lib/test/test_threading.py

@@ -1606,22 +1606,28 @@ def test_interrupt_main_invalid_signal(self):
 
     @threading_helper.reap_threads
     def test_can_interrupt_tight_loops(self):
-        #Nothing to assert here. It just shouldn't hang.
-
-        cont = True
-        started = False
-        def worker():
-            nonlocal started
-            started = True
-            while cont:
+        cont = [True]
+        started = [False]
+        interrupted = [False]
+
+        def worker(started, cont, interrupted):
+            iterations = 100_000_000
+            started[0] = True
+            while cont[0]:
+                if iterations:
+                    iterations -= 1
+                else:
+                    return
                 pass
+            interrupted[0] = True
 
-        t = threading.Thread(target=worker)
+        t = threading.Thread(target=worker,args=(started, cont, interrupted))
         t.start()
-        while not started:
+        while not started[0]:
             pass
-        cont = False
+        cont[0] = False
         t.join()
+        self.assertTrue(interrupted[0])
 
 
 class AtexitTests(unittest.TestCase):