reactor: Add explicit finalize() method to clean up reactor state

The existence of a __del__() method prevents deallocation on python2
if there are circular references.  Replace the __del__() method with a
new finalize() call and arrange for it to be called when the main
reactor is released.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

klippy/klippy.py

@@ -48,10 +48,10 @@ Printer is shutdown
 class Printer:
     config_error = configfile.error
     command_error = homing.CommandError
-    def __init__(self, bglogger, start_args):
+    def __init__(self, main_reactor, bglogger, start_args):
         self.bglogger = bglogger
         self.start_args = start_args
-        self.reactor = reactor.Reactor()
+        self.reactor = main_reactor
         self.reactor.register_callback(self._connect)
         self.state_message = message_startup
         self.in_shutdown_state = False
@@ -312,11 +312,13 @@ def main():
         if bglogger is not None:
             bglogger.clear_rollover_info()
             bglogger.set_rollover_info('versions', versions)
-        printer = Printer(bglogger, start_args)
+        main_reactor = reactor.Reactor()
+        printer = Printer(main_reactor, bglogger, start_args)
         res = printer.run()
         if res in ['exit', 'error_exit']:
             break
         time.sleep(1.)
+        main_reactor.finalize()
         logging.info("Restarting printer")
         start_args['start_reason'] = res
 

klippy/reactor.py

@@ -178,11 +178,6 @@ class SelectReactor:
         util.set_nonblock(self._pipe_fds[0])
         util.set_nonblock(self._pipe_fds[1])
         self.register_fd(self._pipe_fds[0], self._got_pipe_signal)
-    def __del__(self):
-        if self._pipe_fds is not None:
-            os.close(self._pipe_fds[0])
-            os.close(self._pipe_fds[1])
-            self._pipe_fds = None
     # Greenlets
     def _sys_pause(self, waketime):
         # Pause using system sleep for when reactor not running
@@ -251,6 +246,11 @@ class SelectReactor:
         g_next.switch()
     def end(self):
         self._process = False
+    def finalize(self):
+        if self._pipe_fds is not None:
+            os.close(self._pipe_fds[0])
+            os.close(self._pipe_fds[1])
+            self._pipe_fds = None
 
 class PollReactor(SelectReactor):
     def __init__(self):