Separate parent functionality from ParentPollerWindows

ParentPollerWindows contained a mixture of methods to run in the parent
and the child, which was revealed by test failures now that
jupyter_client and ipython_kernel are separate packages. This moves the
parent methods into a new module jupyter_client.win_interrupt

Closes gh-8201

jupyter_client/win_interrupt.py

@@ -0,0 +1,39 b''
+"""Use a Windows event to interrupt a child process like SIGINT.
+
+The child needs to explicitly listen for this - see
+ipython_kernel.parentpoller.ParentPollerWindows for a Python implementation.
+"""
+
+import ctypes
+
+def create_interrupt_event():
+    """Create an interrupt event handle.
+
+    The parent process should call this to create the
+    interrupt event that is passed to the child process. It should store
+    this handle and use it with ``send_interrupt`` to interrupt the child
+    process.
+    """
+    # Create a security attributes struct that permits inheritance of the
+    # handle by new processes.
+    # FIXME: We can clean up this mess by requiring pywin32 for IPython.
+    class SECURITY_ATTRIBUTES(ctypes.Structure):
+        _fields_ = [ ("nLength", ctypes.c_int),
+                     ("lpSecurityDescriptor", ctypes.c_void_p),
+                     ("bInheritHandle", ctypes.c_int) ]
+    sa = SECURITY_ATTRIBUTES()
+    sa_p = ctypes.pointer(sa)
+    sa.nLength = ctypes.sizeof(SECURITY_ATTRIBUTES)
+    sa.lpSecurityDescriptor = 0
+    sa.bInheritHandle = 1
+
+    return ctypes.windll.kernel32.CreateEventA(
+        sa_p,  # lpEventAttributes
+        False, # bManualReset
+        False, # bInitialState
+        '')    # lpName
+
+def send_interrupt(interrupt_handle):
+    """ Sends an interrupt event using the specified handle.
+    """
+    ctypes.windll.kernel32.SetEvent(interrupt_handle)

ipython_kernel/parentpoller.py

@@ -1,148 +1,114 b''
 # Copyright (c) IPython Development Team.
 # Distributed under the terms of the Modified BSD License.
 
 try:
     import ctypes
 except:
     ctypes = None
 import os
 import platform
 import signal
 import time
 try:
     from _thread import interrupt_main  # Py 3
 except ImportError:
     from thread import interrupt_main  # Py 2
 from threading import Thread
 
 from IPython.utils.warn import warn
 
 
 class ParentPollerUnix(Thread):
     """ A Unix-specific daemon thread that terminates the program immediately
     when the parent process no longer exists.
     """
 
     def __init__(self):
         super(ParentPollerUnix, self).__init__()
         self.daemon = True
 
     def run(self):
         # We cannot use os.waitpid because it works only for child processes.
         from errno import EINTR
         while True:
             try:
                 if os.getppid() == 1:
                     os._exit(1)
                 time.sleep(1.0)
             except OSError as e:
                 if e.errno == EINTR:
                     continue
                 raise
 
 
 class ParentPollerWindows(Thread):
     """ A Windows-specific daemon thread that listens for a special event that
     signals an interrupt and, optionally, terminates the program immediately
     when the parent process no longer exists.
     """
 
     def __init__(self, interrupt_handle=None, parent_handle=None):
         """ Create the poller. At least one of the optional parameters must be
         provided.
 
         Parameters
         ----------
         interrupt_handle : HANDLE (int), optional
             If provided, the program will generate a Ctrl+C event when this
             handle is signaled.
 
         parent_handle : HANDLE (int), optional
             If provided, the program will terminate immediately when this
             handle is signaled.
         """
         assert(interrupt_handle or parent_handle)
         super(ParentPollerWindows, self).__init__()
         if ctypes is None:
             raise ImportError("ParentPollerWindows requires ctypes")
         self.daemon = True
         self.interrupt_handle = interrupt_handle
         self.parent_handle = parent_handle
 
-    @staticmethod
-    def create_interrupt_event():
-        """ Create an interrupt event handle.
-
-        The parent process should use this static method for creating the
-        interrupt event that is passed to the child process. It should store
-        this handle and use it with ``send_interrupt`` to interrupt the child
-        process.
-        """
-        # Create a security attributes struct that permits inheritance of the
-        # handle by new processes.
-        # FIXME: We can clean up this mess by requiring pywin32 for IPython.
-        class SECURITY_ATTRIBUTES(ctypes.Structure):
-            _fields_ = [ ("nLength", ctypes.c_int),
-                         ("lpSecurityDescriptor", ctypes.c_void_p),
-                         ("bInheritHandle", ctypes.c_int) ]
-        sa = SECURITY_ATTRIBUTES()
-        sa_p = ctypes.pointer(sa)
-        sa.nLength = ctypes.sizeof(SECURITY_ATTRIBUTES)
-        sa.lpSecurityDescriptor = 0
-        sa.bInheritHandle = 1
-
-        return ctypes.windll.kernel32.CreateEventA(
-            sa_p,  # lpEventAttributes
-            False, # bManualReset
-            False, # bInitialState
-            '')    # lpName
-
-    @staticmethod
-    def send_interrupt(interrupt_handle):
-        """ Sends an interrupt event using the specified handle.
-        """
-        ctypes.windll.kernel32.SetEvent(interrupt_handle)
-
     def run(self):
         """ Run the poll loop. This method never returns.
         """
         try:
             from _winapi import WAIT_OBJECT_0, INFINITE
         except ImportError:
             from _subprocess import WAIT_OBJECT_0, INFINITE
 
         # Build the list of handle to listen on.
         handles = []
         if self.interrupt_handle:
             handles.append(self.interrupt_handle)
         if self.parent_handle:
             handles.append(self.parent_handle)
         arch = platform.architecture()[0]
         c_int = ctypes.c_int64 if arch.startswith('64') else ctypes.c_int
 
         # Listen forever.
         while True:
             result = ctypes.windll.kernel32.WaitForMultipleObjects(
                 len(handles),                            # nCount
                 (c_int * len(handles))(*handles),        # lpHandles
                 False,                                   # bWaitAll
                 INFINITE)                                # dwMilliseconds
 
             if WAIT_OBJECT_0 <= result < len(handles):
                 handle = handles[result - WAIT_OBJECT_0]
 
                 if handle == self.interrupt_handle:
                     # check if signal handler is callable
                     # to avoid 'int not callable' error (Python issue #23395)
                     if callable(signal.getsignal(signal.SIGINT)):
                         interrupt_main()
 
                 elif handle == self.parent_handle:
                     os._exit(1)
             elif result < 0:
                 # wait failed, just give up and stop polling.
                 warn("""Parent poll failed.  If the frontend dies,
                 the kernel may be left running.  Please let us know
                 about your system (bitness, Python, etc.) at
                 [e-mail]""")
                 return

jupyter_client/launcher.py

@@ -1,226 +1,226 b''
 """Utilities for launching kernels
 """
 
 # Copyright (c) IPython Development Team.
 # Distributed under the terms of the Modified BSD License.
 
 import os
 import sys
 from subprocess import Popen, PIPE
 
 from IPython.utils.encoding import getdefaultencoding
 from IPython.utils.py3compat import cast_bytes_py2
 
 
 def swallow_argv(argv, aliases=None, flags=None):
     """strip frontend-specific aliases and flags from an argument list
 
     For use primarily in frontend apps that want to pass a subset of command-line
     arguments through to a subprocess, where frontend-specific flags and aliases
     should be removed from the list.
 
     Parameters
     ----------
 
     argv : list(str)
         The starting argv, to be filtered
     aliases : container of aliases (dict, list, set, etc.)
         The frontend-specific aliases to be removed
     flags : container of flags (dict, list, set, etc.)
         The frontend-specific flags to be removed
 
     Returns
     -------
 
     argv : list(str)
         The argv list, excluding flags and aliases that have been stripped
     """
 
     if aliases is None:
         aliases = set()
     if flags is None:
         flags = set()
 
     stripped = list(argv) # copy
 
     swallow_next = False
     was_flag = False
     for a in argv:
         if a == '--':
             break
         if swallow_next:
             swallow_next = False
             # last arg was an alias, remove the next one
             # *unless* the last alias has a no-arg flag version, in which
             # case, don't swallow the next arg if it's also a flag:
             if not (was_flag and a.startswith('-')):
                 stripped.remove(a)
                 continue
         if a.startswith('-'):
             split = a.lstrip('-').split('=')
             name = split[0]
             # we use startswith because argparse accepts any arg to be specified
             # by any leading section, as long as it is unique,
             # so `--no-br` means `--no-browser` in the notebook, etc.
             if any(alias.startswith(name) for alias in aliases):
                 stripped.remove(a)
                 if len(split) == 1:
                     # alias passed with arg via space
                     swallow_next = True
                     # could have been a flag that matches an alias, e.g. `existing`
                     # in which case, we might not swallow the next arg
                     was_flag = name in flags
             elif len(split) == 1 and any(flag.startswith(name) for flag in flags):
                 # strip flag, but don't swallow next, as flags don't take args
                 stripped.remove(a)
 
     # return shortened list
     return stripped
 
 
 def make_ipkernel_cmd(mod='ipython_kernel', executable=None, extra_arguments=[], **kw):
     """Build Popen command list for launching an IPython kernel.
 
     Parameters
     ----------
     mod : str, optional (default 'ipython_kernel')
         A string of an IPython module whose __main__ starts an IPython kernel
 
     executable : str, optional (default sys.executable)
         The Python executable to use for the kernel process.
 
     extra_arguments : list, optional
         A list of extra arguments to pass when executing the launch code.
 
     Returns
     -------
 
     A Popen command list
     """
     if executable is None:
         executable = sys.executable
     arguments = [ executable, '-m', mod, '-f', '{connection_file}' ]
     arguments.extend(extra_arguments)
 
     return arguments
 
 
 def launch_kernel(cmd, stdin=None, stdout=None, stderr=None, env=None,
                         independent=False,
                         cwd=None,
                         **kw
                         ):
     """ Launches a localhost kernel, binding to the specified ports.
 
     Parameters
     ----------
     cmd : Popen list,
         A string of Python code that imports and executes a kernel entry point.
 
     stdin, stdout, stderr : optional (default None)
         Standards streams, as defined in subprocess.Popen.
 
     independent : bool, optional (default False)
         If set, the kernel process is guaranteed to survive if this process
         dies. If not set, an effort is made to ensure that the kernel is killed
         when this process dies. Note that in this case it is still good practice
         to kill kernels manually before exiting.
 
     cwd : path, optional
         The working dir of the kernel process (default: cwd of this process).
 
     Returns
     -------
 
     Popen instance for the kernel subprocess
     """
 
     # Popen will fail (sometimes with a deadlock) if stdin, stdout, and stderr
     # are invalid. Unfortunately, there is in general no way to detect whether
     # they are valid.  The following two blocks redirect them to (temporary)
     # pipes in certain important cases.
 
     # If this process has been backgrounded, our stdin is invalid. Since there
     # is no compelling reason for the kernel to inherit our stdin anyway, we'll
     # place this one safe and always redirect.
     redirect_in = True
     _stdin = PIPE if stdin is None else stdin
 
     # If this process in running on pythonw, we know that stdin, stdout, and
     # stderr are all invalid.
     redirect_out = sys.executable.endswith('pythonw.exe')
     if redirect_out:
         blackhole = open(os.devnull, 'w')
         _stdout = blackhole if stdout is None else stdout
         _stderr = blackhole if stderr is None else stderr
     else:
         _stdout, _stderr = stdout, stderr
 
     env = env if (env is not None) else os.environ.copy()
 
     encoding = getdefaultencoding(prefer_stream=False)
     kwargs = dict(
         stdin=_stdin,
         stdout=_stdout,
         stderr=_stderr,
         cwd=cwd,
         env=env,
     )
 
     # Spawn a kernel.
     if sys.platform == 'win32':
         # Popen on Python 2 on Windows cannot handle unicode args or cwd
         cmd = [ cast_bytes_py2(c, encoding) for c in cmd ]
         if cwd:
             cwd = cast_bytes_py2(cwd, sys.getfilesystemencoding() or 'ascii')
             kwargs['cwd'] = cwd
 
-        from jupyter_client.parentpoller import ParentPollerWindows
+        from .win_interrupt import create_interrupt_event
         # Create a Win32 event for interrupting the kernel
         # and store it in an environment variable.
-        interrupt_event = ParentPollerWindows.create_interrupt_event()
+        interrupt_event = create_interrupt_event()
         env["JPY_INTERRUPT_EVENT"] = str(interrupt_event)
         # deprecated old env name:
         env["IPY_INTERRUPT_EVENT"] = env["JPY_INTERRUPT_EVENT"]
 
         try:
             from _winapi import DuplicateHandle, GetCurrentProcess, \
                 DUPLICATE_SAME_ACCESS, CREATE_NEW_PROCESS_GROUP
         except:
             from _subprocess import DuplicateHandle, GetCurrentProcess, \
                 DUPLICATE_SAME_ACCESS, CREATE_NEW_PROCESS_GROUP
         # Launch the kernel process
         if independent:
             kwargs['creationflags'] = CREATE_NEW_PROCESS_GROUP
         else:
             pid = GetCurrentProcess()
             handle = DuplicateHandle(pid, pid, pid, 0,
                                      True, # Inheritable by new processes.
                                      DUPLICATE_SAME_ACCESS)
             env['JPY_PARENT_PID'] = str(int(handle))
 
         proc = Popen(cmd, **kwargs)
 
         # Attach the interrupt event to the Popen objet so it can be used later.
         proc.win32_interrupt_event = interrupt_event
 
     else:
         if independent:
             kwargs['preexec_fn'] = lambda: os.setsid()
         else:
             env['JPY_PARENT_PID'] = str(os.getpid())
 
         proc = Popen(cmd, **kwargs)
 
     # Clean up pipes created to work around Popen bug.
     if redirect_in:
         if stdin is None:
             proc.stdin.close()
 
     return proc
 
 __all__ = [
     'swallow_argv',
     'make_ipkernel_cmd',
     'launch_kernel',
 ]

jupyter_client/manager.py

@@ -1,442 +1,442 b''
 """Base class to manage a running kernel"""
 
 # Copyright (c) IPython Development Team.
 # Distributed under the terms of the Modified BSD License.
 
 from __future__ import absolute_import
 
 from contextlib import contextmanager
 import os
 import re
 import signal
 import sys
 import time
 import warnings
 try:
     from queue import Empty  # Py 3
 except ImportError:
     from Queue import Empty  # Py 2
 
 import zmq
 
 from IPython.utils.importstring import import_item
 from IPython.utils.localinterfaces import is_local_ip, local_ips
 from IPython.utils.path import get_ipython_dir
 from IPython.utils.traitlets import (
     Any, Instance, Unicode, List, Bool, Type, DottedObjectName
 )
 from jupyter_client import (
     launch_kernel,
     kernelspec,
 )
 from .connect import ConnectionFileMixin
 from .session import Session
 from .managerabc import (
     KernelManagerABC
 )
 
 
 class KernelManager(ConnectionFileMixin):
     """Manages a single kernel in a subprocess on this host.
 
     This version starts kernels with Popen.
     """
 
     # The PyZMQ Context to use for communication with the kernel.
     context = Instance(zmq.Context)
     def _context_default(self):
         return zmq.Context.instance()
 
     # the class to create with our `client` method
     client_class = DottedObjectName('jupyter_client.blocking.BlockingKernelClient')
     client_factory = Type(allow_none=True)
     def _client_class_changed(self, name, old, new):
         self.client_factory = import_item(str(new))
 
     # The kernel process with which the KernelManager is communicating.
     # generally a Popen instance
     kernel = Any()
 
     kernel_spec_manager = Instance(kernelspec.KernelSpecManager)
 
     def _kernel_spec_manager_default(self):
         return kernelspec.KernelSpecManager(ipython_dir=self.ipython_dir)
 
     kernel_name = Unicode(kernelspec.NATIVE_KERNEL_NAME)
 
     kernel_spec = Instance(kernelspec.KernelSpec)
 
     def _kernel_spec_default(self):
         return self.kernel_spec_manager.get_kernel_spec(self.kernel_name)
 
     def _kernel_name_changed(self, name, old, new):
         if new == 'python':
             self.kernel_name = kernelspec.NATIVE_KERNEL_NAME
             # This triggered another run of this function, so we can exit now
             return
         self.kernel_spec = self.kernel_spec_manager.get_kernel_spec(new)
         self.ipython_kernel = new in {'python', 'python2', 'python3'}
 
     kernel_cmd = List(Unicode, config=True,
         help="""DEPRECATED: Use kernel_name instead.
 
         The Popen Command to launch the kernel.
         Override this if you have a custom kernel.
         If kernel_cmd is specified in a configuration file,
         IPython does not pass any arguments to the kernel,
         because it cannot make any assumptions about the
         arguments that the kernel understands. In particular,
         this means that the kernel does not receive the
         option --debug if it given on the IPython command line.
         """
     )
 
     def _kernel_cmd_changed(self, name, old, new):
         warnings.warn("Setting kernel_cmd is deprecated, use kernel_spec to "
                       "start different kernels.")
         self.ipython_kernel = False
 
     ipython_kernel = Bool(True)
 
     ipython_dir = Unicode()
     def _ipython_dir_default(self):
         return get_ipython_dir()
 
     # Protected traits
     _launch_args = Any()
     _control_socket = Any()
 
     _restarter = Any()
 
     autorestart = Bool(False, config=True,
         help="""Should we autorestart the kernel if it dies."""
     )
 
     def __del__(self):
         self._close_control_socket()
         self.cleanup_connection_file()
 
     #--------------------------------------------------------------------------
     # Kernel restarter
     #--------------------------------------------------------------------------
 
     def start_restarter(self):
         pass
 
     def stop_restarter(self):
         pass
 
     def add_restart_callback(self, callback, event='restart'):
         """register a callback to be called when a kernel is restarted"""
         if self._restarter is None:
             return
         self._restarter.add_callback(callback, event)
 
     def remove_restart_callback(self, callback, event='restart'):
         """unregister a callback to be called when a kernel is restarted"""
         if self._restarter is None:
             return
         self._restarter.remove_callback(callback, event)
 
     #--------------------------------------------------------------------------
     # create a Client connected to our Kernel
     #--------------------------------------------------------------------------
 
     def client(self, **kwargs):
         """Create a client configured to connect to our kernel"""
         if self.client_factory is None:
             self.client_factory = import_item(self.client_class)
 
         kw = {}
         kw.update(self.get_connection_info())
         kw.update(dict(
             connection_file=self.connection_file,
             session=self.session,
             parent=self,
         ))
 
         # add kwargs last, for manual overrides
         kw.update(kwargs)
         return self.client_factory(**kw)
 
     #--------------------------------------------------------------------------
     # Kernel management
     #--------------------------------------------------------------------------
 
     def format_kernel_cmd(self, extra_arguments=None):
         """replace templated args (e.g. {connection_file})"""
         extra_arguments = extra_arguments or []
         if self.kernel_cmd:
             cmd = self.kernel_cmd + extra_arguments
         else:
             cmd = self.kernel_spec.argv + extra_arguments
 
         ns = dict(connection_file=self.connection_file)
         ns.update(self._launch_args)
 
         pat = re.compile(r'\{([A-Za-z0-9_]+)\}')
         def from_ns(match):
             """Get the key out of ns if it's there, otherwise no change."""
             return ns.get(match.group(1), match.group())
 
         return [ pat.sub(from_ns, arg) for arg in cmd ]
 
     def _launch_kernel(self, kernel_cmd, **kw):
         """actually launch the kernel
 
         override in a subclass to launch kernel subprocesses differently
         """
         return launch_kernel(kernel_cmd, **kw)
 
     # Control socket used for polite kernel shutdown
 
     def _connect_control_socket(self):
         if self._control_socket is None:
             self._control_socket = self.connect_control()
             self._control_socket.linger = 100
 
     def _close_control_socket(self):
         if self._control_socket is None:
             return
         self._control_socket.close()
         self._control_socket = None
 
     def start_kernel(self, **kw):
         """Starts a kernel on this host in a separate process.
 
         If random ports (port=0) are being used, this method must be called
         before the channels are created.
 
         Parameters
         ----------
         **kw : optional
              keyword arguments that are passed down to build the kernel_cmd
              and launching the kernel (e.g. Popen kwargs).
         """
         if self.transport == 'tcp' and not is_local_ip(self.ip):
             raise RuntimeError("Can only launch a kernel on a local interface. "
                                "Make sure that the '*_address' attributes are "
                                "configured properly. "
                                "Currently valid addresses are: %s" % local_ips()
                                )
 
         # write connection file / get default ports
         self.write_connection_file()
 
         # save kwargs for use in restart
         self._launch_args = kw.copy()
         # build the Popen cmd
         extra_arguments = kw.pop('extra_arguments', [])
         kernel_cmd = self.format_kernel_cmd(extra_arguments=extra_arguments)
         if self.kernel_cmd:
             # If kernel_cmd has been set manually, don't refer to a kernel spec
             env = os.environ
         else:
             # Environment variables from kernel spec are added to os.environ
             env = os.environ.copy()
             env.update(self.kernel_spec.env or {})
         # launch the kernel subprocess
         self.kernel = self._launch_kernel(kernel_cmd, env=env,
                                     **kw)
         self.start_restarter()
         self._connect_control_socket()
 
     def request_shutdown(self, restart=False):
         """Send a shutdown request via control channel
 
         On Windows, this just kills kernels instead, because the shutdown
         messages don't work.
         """
         content = dict(restart=restart)
         msg = self.session.msg("shutdown_request", content=content)
         self.session.send(self._control_socket, msg)
 
     def finish_shutdown(self, waittime=1, pollinterval=0.1):
         """Wait for kernel shutdown, then kill process if it doesn't shutdown.
 
         This does not send shutdown requests - use :meth:`request_shutdown`
         first.
         """
         for i in range(int(waittime/pollinterval)):
             if self.is_alive():
                 time.sleep(pollinterval)
             else:
                 break
         else:
             # OK, we've waited long enough.
             if self.has_kernel:
                 self._kill_kernel()
 
     def cleanup(self, connection_file=True):
         """Clean up resources when the kernel is shut down"""
         if connection_file:
             self.cleanup_connection_file()
 
         self.cleanup_ipc_files()
         self._close_control_socket()
 
     def shutdown_kernel(self, now=False, restart=False):
         """Attempts to the stop the kernel process cleanly.
 
         This attempts to shutdown the kernels cleanly by:
 
         1. Sending it a shutdown message over the shell channel.
         2. If that fails, the kernel is shutdown forcibly by sending it
            a signal.
 
         Parameters
         ----------
         now : bool
             Should the kernel be forcible killed *now*. This skips the
             first, nice shutdown attempt.
         restart: bool
             Will this kernel be restarted after it is shutdown. When this
             is True, connection files will not be cleaned up.
         """
         # Stop monitoring for restarting while we shutdown.
         self.stop_restarter()
 
         if now:
             self._kill_kernel()
         else:
             self.request_shutdown(restart=restart)
             # Don't send any additional kernel kill messages immediately, to give
             # the kernel a chance to properly execute shutdown actions. Wait for at
             # most 1s, checking every 0.1s.
             self.finish_shutdown()
 
         self.cleanup(connection_file=not restart)
 
     def restart_kernel(self, now=False, **kw):
         """Restarts a kernel with the arguments that were used to launch it.
 
         If the old kernel was launched with random ports, the same ports will be
         used for the new kernel. The same connection file is used again.
 
         Parameters
         ----------
         now : bool, optional
             If True, the kernel is forcefully restarted *immediately*, without
             having a chance to do any cleanup action.  Otherwise the kernel is
             given 1s to clean up before a forceful restart is issued.
 
             In all cases the kernel is restarted, the only difference is whether
             it is given a chance to perform a clean shutdown or not.
 
         **kw : optional
             Any options specified here will overwrite those used to launch the
             kernel.
         """
         if self._launch_args is None:
             raise RuntimeError("Cannot restart the kernel. "
                                "No previous call to 'start_kernel'.")
         else:
             # Stop currently running kernel.
             self.shutdown_kernel(now=now, restart=True)
 
             # Start new kernel.
             self._launch_args.update(kw)
             self.start_kernel(**self._launch_args)
 
     @property
     def has_kernel(self):
         """Has a kernel been started that we are managing."""
         return self.kernel is not None
 
     def _kill_kernel(self):
         """Kill the running kernel.
 
         This is a private method, callers should use shutdown_kernel(now=True).
         """
         if self.has_kernel:
 
             # Signal the kernel to terminate (sends SIGKILL on Unix and calls
             # TerminateProcess() on Win32).
             try:
                 self.kernel.kill()
             except OSError as e:
                 # In Windows, we will get an Access Denied error if the process
                 # has already terminated. Ignore it.
                 if sys.platform == 'win32':
                     if e.winerror != 5:
                         raise
                 # On Unix, we may get an ESRCH error if the process has already
                 # terminated. Ignore it.
                 else:
                     from errno import ESRCH
                     if e.errno != ESRCH:
                         raise
 
             # Block until the kernel terminates.
             self.kernel.wait()
             self.kernel = None
         else:
             raise RuntimeError("Cannot kill kernel. No kernel is running!")
 
     def interrupt_kernel(self):
         """Interrupts the kernel by sending it a signal.
 
         Unlike ``signal_kernel``, this operation is well supported on all
         platforms.
         """
         if self.has_kernel:
             if sys.platform == 'win32':
-                from .parentpoller import ParentPollerWindows as Poller
-                Poller.send_interrupt(self.kernel.win32_interrupt_event)
+                from .win_interrupt import send_interrupt
+                send_interrupt(self.kernel.win32_interrupt_event)
             else:
                 self.kernel.send_signal(signal.SIGINT)
         else:
             raise RuntimeError("Cannot interrupt kernel. No kernel is running!")
 
     def signal_kernel(self, signum):
         """Sends a signal to the kernel.
 
         Note that since only SIGTERM is supported on Windows, this function is
         only useful on Unix systems.
         """
         if self.has_kernel:
             self.kernel.send_signal(signum)
         else:
             raise RuntimeError("Cannot signal kernel. No kernel is running!")
 
     def is_alive(self):
         """Is the kernel process still running?"""
         if self.has_kernel:
             if self.kernel.poll() is None:
                 return True
             else:
                 return False
         else:
             # we don't have a kernel
             return False
 
 
 KernelManagerABC.register(KernelManager)
 
 
 def start_new_kernel(startup_timeout=60, kernel_name='python', **kwargs):
     """Start a new kernel, and return its Manager and Client"""
     km = KernelManager(kernel_name=kernel_name)
     km.start_kernel(**kwargs)
     kc = km.client()
     kc.start_channels()
     kc.wait_for_ready()
 
     return km, kc
 
 @contextmanager
 def run_kernel(**kwargs):
     """Context manager to create a kernel in a subprocess.
 
     The kernel is shut down when the context exits.
 
     Returns
     -------
     kernel_client: connected KernelClient instance
     """
     km, kc = start_new_kernel(**kwargs)
     try:
         yield kc
     finally:
         kc.stop_channels()
         km.shutdown_kernel(now=True)