Index: Modules/signalmodule.c
===================================================================
--- Modules/signalmodule.c	(revision 53537)
+++ Modules/signalmodule.c	(working copy)
@@ -75,7 +75,8 @@
         PyObject *func;
 } Handlers[NSIG];
 
-static int is_tripped = 0; /* Speed up sigcheck() when none tripped */
+/* Speed up sigcheck() when none tripped */
+static volatile sig_atomic_t is_tripped = 0;
 
 static PyObject *DefaultHandler;
 static PyObject *IgnoreHandler;
@@ -122,7 +123,7 @@
 	/* See NOTES section above */
 	if (getpid() == main_pid) {
 #endif
-		is_tripped++;
+		is_tripped = 1;
 		Handlers[sig_num].tripped = 1;
 		Py_AddPendingCall(checksignals_witharg, NULL);
 #ifdef WITH_THREAD
@@ -597,13 +598,16 @@
 
 	if (!is_tripped)
 		return 0;
+	is_tripped = 0;
+
 #ifdef WITH_THREAD
 	if (PyThread_get_thread_ident() != main_thread)
 		return 0;
 #endif
+
 	if (!(f = (PyObject *)PyEval_GetFrame()))
 		f = Py_None;
-	
+
 	for (i = 1; i < NSIG; i++) {
 		if (Handlers[i].tripped) {
 			PyObject *result = NULL;
@@ -621,7 +625,7 @@
 			Py_DECREF(result);
 		}
 	}
-	is_tripped = 0;
+
 	return 0;
 }
 
@@ -632,7 +636,7 @@
 void
 PyErr_SetInterrupt(void)
 {
-	is_tripped++;
+	is_tripped = 1;
 	Handlers[SIGINT].tripped = 1;
 	Py_AddPendingCall((int (*)(void *))PyErr_CheckSignals, NULL);
 }