Skip signal handler re-installation if it is not necessary.  Issue 8354.
diff --git a/Modules/signalmodule.c b/Modules/signalmodule.c
index bb7e4b0..b1ee890 100644
--- a/Modules/signalmodule.c
+++ b/Modules/signalmodule.c
@@ -198,7 +198,12 @@
 		return;
 	}
 #endif
+#ifndef HAVE_SIGACTION
+	/* If the handler was not set up with sigaction, reinstall it.  See
+	 * Python/pythonrun.c for the implementation of PyOS_setsig which
+	 * makes this true.  See also issue8354. */
 	PyOS_setsig(sig_num, signal_handler);
+#endif
 }