do not leak blocked signals out of unit test

Author: stephen-hansen

Lib/test/_test_multiprocessing.py

@@ -6044,21 +6044,27 @@ def test_resource_tracker_exit_code(self):
                 self._test_resource_tracker_leak_resources(
                     cleanup=cleanup,
                 )
+
     @unittest.skipUnless(hasattr(signal, "pthread_sigmask"), "pthread_sigmask is not available")
     def test_resource_tracker_blocked_signals(self):
         #
         # gh-127586: Check that resource_tracker does not override blocked signals of caller.
         #
         from multiprocessing.resource_tracker import ResourceTracker
+        orig_sigmask = signal.pthread_sigmask(signal.SIG_BLOCK, set())
         signals = {signal.SIGTERM, signal.SIGINT, signal.SIGUSR1}
 
-        for sig in signals:
-            signal.pthread_sigmask(signal.SIG_SETMASK, {sig})
-            self.assertEqual(signal.pthread_sigmask(signal.SIG_BLOCK, set()), {sig})
-            tracker = ResourceTracker()
-            tracker.ensure_running()
-            self.assertEqual(signal.pthread_sigmask(signal.SIG_BLOCK, set()), {sig})
-            tracker._stop()
+        try:
+            for sig in signals:
+                signal.pthread_sigmask(signal.SIG_SETMASK, {sig})
+                self.assertEqual(signal.pthread_sigmask(signal.SIG_BLOCK, set()), {sig})
+                tracker = ResourceTracker()
+                tracker.ensure_running()
+                self.assertEqual(signal.pthread_sigmask(signal.SIG_BLOCK, set()), {sig})
+                tracker._stop()
+        finally:
+            # restore sigmask to what it was before executing test
+            signal.pthread_sigmask(signal.SIG_SETMASK, orig_sigmask)
 
 class TestSimpleQueue(unittest.TestCase):