redshift-gtk: Make sure that child process is closed after signals

Instead of calling sys.exit() the signal handlers now try to terminate
the child process. After the child exits, the process will be reaped by
the GLib callback which will call Gtk.main_quit() which will then quit
redshift-gtk. This ensures that the redshift process does not outlive
the redshift-gtk process.

src/redshift-gtk/statusicon.py

@@ -143,9 +143,13 @@ def set_inhibit(self, inhibit):
         if inhibit != self._inhibited:
             self._child_toggle_inhibit()
 
+    def _child_signal(self, sg):
+        """Send signal to child process."""
+        os.kill(self._process[0], sg)
+
     def _child_toggle_inhibit(self):
         '''Sends a request to the child process to toggle state'''
-        os.kill(self._process[0], signal.SIGUSR1)
+        self._child_signal(signal.SIGUSR1)
 
     def _child_cb(self, pid, status, data=None):
         '''Called when the child process exists'''
@@ -163,13 +167,12 @@ def _child_cb(self, pid, status, data=None):
         report_errors = False
         try:
             GLib.spawn_check_exit_status(status)
-            Gtk.main_quit()
         except GLib.GError:
-            report_errors = True
-
-        if report_errors:
             self.emit('error-occured', self._errors)
 
+        GLib.spawn_close_pid(self._process[0])
+        Gtk.main_quit()
+
     def _child_key_change_cb(self, key, value):
         '''Called when the child process reports a change of internal state'''
 
@@ -227,14 +230,13 @@ def _child_data_cb(self, f, cond, data):
 
         return True
 
-    def termwait(self):
-        '''Send SIGINT and wait for the child process to quit'''
-        try:
-            os.kill(self._process[0], signal.SIGINT)
-            os.waitpid(self._process[0], 0)
-        except ProcessLookupError:
-            # Process has apparently already disappeared
-            pass
+    def terminate_child(self):
+        """Send SIGINT to child process."""
+        self._child_signal(signal.SIGINT)
+
+    def kill_child(self):
+        """Send SIGKILL to child process."""
+        self._child_signal(signal.SIGKILL)
 
 
 class RedshiftStatusIcon(object):
@@ -490,35 +492,36 @@ def destroy_cb(self, widget, data=None):
         '''Callback when a request to quit the application is made'''
         if not appindicator:
             self.status_icon.set_visible(False)
-        Gtk.main_quit()
+        self._controller.terminate_child()
         return False
 
 
-def sigterm_handler(data=None):
-    sys.exit(0)
-
-
 def run():
     utils.setproctitle('redshift-gtk')
 
-    # Install TERM signal handler
-    GLib.unix_signal_add(GLib.PRIORITY_DEFAULT, signal.SIGTERM,
-                         sigterm_handler, None)
-    GLib.unix_signal_add(GLib.PRIORITY_DEFAULT, signal.SIGINT,
-                         sigterm_handler, None)
-
     # Internationalisation
     gettext.bindtextdomain('redshift', defs.LOCALEDIR)
     gettext.textdomain('redshift')
 
     # Create redshift child process controller
     c = RedshiftController(sys.argv[1:])
+
+    def terminate_child(data=None):
+        c.terminate_child()
+        return False
+
+    # Install signal handlers
+    GLib.unix_signal_add(GLib.PRIORITY_DEFAULT, signal.SIGTERM,
+                         terminate_child, None)
+    GLib.unix_signal_add(GLib.PRIORITY_DEFAULT, signal.SIGINT,
+                         terminate_child, None)
+
     try:
         # Create status icon
         s = RedshiftStatusIcon(c)
 
         # Run main loop
         Gtk.main()
-    finally:
-        # Always make sure that the child process is closed
-        c.termwait()
+    except:
+        c.kill_child()
+        raise