fix race in signal handling

kumaraditya303 · kumaraditya303 · commit ace9cf5c167d · 2023-03-03T15:02:50.000Z
diff --git a/Lib/test/test_signal.py b/Lib/test/test_signal.py
@@ -1,3 +1,4 @@
+import _thread
 import enum
 import errno
 import inspect
@@ -1406,6 +1407,20 @@ def handler(a, b):
         signal.raise_signal(signal.SIGINT)
         self.assertTrue(is_ok)
 
+    def test__thread_interrupt_main(self):
+        code = """if 1:
+        import _thread
+        class Foo():
+            def __del__(self):
+                _thread.interrupt_main()
+
+        x = Foo()
+        """
+
+        rc, out, err = assert_python_ok('-c', code)
+        self.assertIn(b'OSError: Signal 2 ignored due to race condition', err)
+
+
 
 class PidfdSignalTest(unittest.TestCase):
 
diff --git a/Modules/signalmodule.c b/Modules/signalmodule.c
@@ -148,6 +148,9 @@ get_signal_state(PyObject *module)
 static inline int
 compare_handler(PyObject *func, PyObject *dfl_ign_handler)
 {
+    if (func == NULL || dfl_ign_handler == NULL) {
+        return 0;
+    }
     assert(PyLong_CheckExact(dfl_ign_handler));
     if (!PyLong_CheckExact(func)) {
         return 0;
