Issue 20633: SystemError: Parent module 'multiprocessing' not loaded, cannot perform relative import (original) (raw)

Using multiprocessing.Manager to share a dict between two processes raises the below exception at main process termination. Child process is joined and terminates gracefully before the main process.

Replacing multiprocessing/forking.py:135 with from multiprocessing.connection import wait fixes the issue.

Python 3.3.1 (default, Sep 25 2013, 19:29:01) [GCC 4.7.3] on linux Type "help", "copyright", "credits" or "license" for more information.

import sys sys.version '3.3.1 (default, Sep 25 2013, 19:29:01) \n[GCC 4.7.3]'

multiprocessing/forking.py:135

132 def wait(self, timeout=None):
133 if self.returncode is None:
134 if timeout is not None:
135 from .connection import wait
136 if not wait([self.sentinel], timeout):
137 return None
138 # This shouldn't block if wait() returned successfully.
139 return self.poll(os.WNOHANG if timeout == 0.0 else 0)
140 return self.returncode

Traceback

Traceback (most recent call last): File "/home/d4de/work/redacted/redacted-engine/venv/lib/python3.3/multiprocessing/util.py", line 255, in _run_finalizers finalizer() File "/home/d4de/work/redacted/redacted-engine/venv/lib/python3.3/multiprocessing/util.py", line 188, in call res = self._callback(*self._args, **self._kwargs) File "/home/d4de/work/redacted/redacted-engine/venv/lib/python3.3/multiprocessing/managers.py", line 588, in _finalize_manager process.join(timeout=1.0) File "/home/d4de/work/redacted/redacted-engine/venv/lib/python3.3/multiprocessing/process.py", line 127, in join res = self._popen.wait(timeout) File "/home/d4de/work/redacted/redacted-engine/venv/lib/python3.3/multiprocessing/forking.py", line 135, in wait from .connection import wait SystemError: Parent module 'multiprocessing' not loaded, cannot perform relative import Traceback (most recent call last): File "/home/d4de/work/redacted/redacted-engine/venv/lib/python3.3/multiprocessing/util.py", line 255, in _run_finalizers finalizer() File "/home/d4de/work/redacted/redacted-engine/venv/lib/python3.3/multiprocessing/util.py", line 188, in call res = self._callback(*self._args, **self._kwargs) File "/home/d4de/work/redacted/redacted-engine/venv/lib/python3.3/multiprocessing/managers.py", line 588, in _finalize_manager process.join(timeout=1.0) File "/home/d4de/work/redacted/redacted-engine/venv/lib/python3.3/multiprocessing/process.py", line 127, in join res = self._popen.wait(timeout) File "/home/d4de/work/redacted/redacted-engine/venv/lib/python3.3/multiprocessing/forking.py", line 135, in wait from .connection import wait SystemError: Parent module 'multiprocessing' not loaded, cannot perform relative import