Start IOPubThread at creation

ipykernel/inprocess/ipkernel.py

@@ -57,7 +57,6 @@ class InProcessKernel(IPythonKernel):
     @default('iopub_thread')
     def _default_iopub_thread(self):
         thread = IOPubThread(self._underlying_iopub_socket)
-        thread.start()
         return thread
 
     iopub_socket = Instance(BackgroundSocket)

ipykernel/iostream.py

@@ -45,7 +45,7 @@ class IOPubThread:
     """
 
     def __init__(self, socket, pipe=False):
-        """Create IOPub thread
+        """Create IOPub thread and start it
 
         Parameters
         ----------
@@ -73,6 +73,9 @@ def __init__(self, socket, pipe=False):
         self._events = deque()
         self._event_pipes = WeakSet()
         self._setup_event_pipe()
+        # make sure we don't prevent process exit
+        # I'm not sure why setting daemon=True above isn't enough, but it doesn't appear to be.
+        atexit.register(self.stop)
 
     def _thread_main(self):
         """The inner loop that's actually run in a thread"""
@@ -177,14 +180,6 @@ def _check_mp_mode(self):
         else:
             return CHILD
 
-    def start(self):
-        """Start the IOPub thread"""
-        self.thread.name = "IOPub"
-        self.thread.start()
-        # make sure we don't prevent process exit
-        # I'm not sure why setting daemon=True above isn't enough, but it doesn't appear to be.
-        atexit.register(self.stop)
-
     def stop(self):
         """Stop the IOPub thread"""
         if not self.thread.is_alive():
@@ -369,7 +364,6 @@ def __init__(
                 stacklevel=2,
             )
             pub_thread = IOPubThread(pub_thread)
-            pub_thread.start()
         self.pub_thread = pub_thread
         self.name = name
         self.topic = b"stream." + name.encode()

ipykernel/ipkernel.py

@@ -282,7 +282,7 @@ def set_sigint_result():
                 if sigint_future.cancelled() or sigint_future.done():
                     return
                 sigint_future.set_result(1)
-            # use call_soon_threadsage for thread safety
+            # use call_soon_threadsafe for thread safety
             self.io_loop.call_soon_threadsafe(set_sigint_result)
 
         # set the custom sigint hander during this context

ipykernel/tests/test_io.py

@@ -16,7 +16,6 @@ def test_io_api():
     ctx = zmq.Context()
     pub = ctx.socket(zmq.PUB)
     thread = IOPubThread(pub)
-    thread.start()
 
     stream = OutStream(session, thread, 'stdout')
 
@@ -47,7 +46,6 @@ def test_io_isatty():
     ctx = zmq.Context()
     pub = ctx.socket(zmq.PUB)
     thread = IOPubThread(pub)
-    thread.start()
 
     stream = OutStream(session, thread, 'stdout', isatty=True)
     assert stream.isatty()