Merge pull request ipython#233 from minrk/master

Disable parent-poller if PID is 1

ipykernel/kernelapp.py

@@ -165,7 +165,10 @@ def init_poller(self):
         if sys.platform == 'win32':
             if self.interrupt or self.parent_handle:
                 self.poller = ParentPollerWindows(self.interrupt, self.parent_handle)
-        elif self.parent_handle:
+        elif self.parent_handle and self.parent_handle != 1:
+            # PID 1 (init) is special and will never go away,
+            # only be reassigned.
+            # Parent polling doesn't work if ppid == 1 to start with.
             self.poller = ParentPollerUnix()
 
     def _bind_socket(self, s, port):

ipykernel/parentpoller.py

@@ -15,6 +15,8 @@
     from thread import interrupt_main  # Py 2
 from threading import Thread
 
+from traitlets.log import get_logger
+
 import warnings
 
 class ParentPollerUnix(Thread):
@@ -32,6 +34,7 @@ def run(self):
         while True:
             try:
                 if os.getppid() == 1:
+                    get_logger().warning("Parent appears to have exited, shutting down.")
                     os._exit(1)
                 time.sleep(1.0)
             except OSError as e:
@@ -103,6 +106,7 @@ def run(self):
                         interrupt_main()
 
                 elif handle == self.parent_handle:
+                    get_logger().warning("Parent appears to have exited, shutting down.")
                     os._exit(1)
             elif result < 0:
                 # wait failed, just give up and stop polling.