New submission from Ole Streicher:
On Debian Hurd, there is no sem_open implementation. When I try there to create
a Queue, I get different errors, depending on the Python version:
import multiprocessing
q = multiprocessing.Queue()
gives on Python 2.7.9:
maxsize = 0
def Queue(maxsize=0):
'''
Returns a queue object
'''
> from multiprocessing.queues import Queue
/usr/lib/python2.7/multiprocessing/__init__.py:217:
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
__all__ = ['Queue', 'SimpleQueue', 'JoinableQueue']
import sys
import os
import threading
import collections
import time
import atexit
import weakref
from Queue import Empty, Full
import _multiprocessing
from multiprocessing import Pipe
> from multiprocessing.synchronize import Lock, BoundedSemaphore, Semaphore,
> Condition
/usr/lib/python2.7/multiprocessing/queues.py:48:
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
'Lock', 'RLock', 'Semaphore', 'BoundedSemaphore', 'Condition', 'Event'
]
import threading
import os
import sys
from time import time as _time, sleep as _sleep
import _multiprocessing
from multiprocessing.process import current_process
from multiprocessing.util import Finalize, register_after_fork, debug
from multiprocessing.forking import assert_spawning, Popen
# Try to import the mp.synchronize module cleanly, if it fails
# raise ImportError for platforms lacking a working sem_open implementation.
# See issue 3770
try:
from _multiprocessing import SemLock
except (ImportError):
raise ImportError("This platform lacks a functioning sem_open" +
" implementation, therefore, the required" +
" synchronization primitives needed will not" +
> " function, see issue 3770.")
E ImportError: This platform lacks a functioning sem_open
implementation, therefore, the required synchronization primitives needed will
not function, see issue 3770.
/usr/lib/python2.7/multiprocessing/synchronize.py:59: ImportError
and on 3.4.2:
self = <multiprocessing.context.DefaultContext object at 0x1449b0c>, maxsize = 0
def Queue(self, maxsize=0):
'''Returns a queue object'''
from .queues import Queue
> return Queue(maxsize, ctx=self.get_context())
/usr/lib/python3.4/multiprocessing/context.py:101:
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
self = <multiprocessing.queues.Queue object at 0x511e8cc>, maxsize = 0
def __init__(self, maxsize=0, *, ctx):
if maxsize <= 0:
> maxsize = _multiprocessing.SemLock.SEM_VALUE_MAX
E AttributeError: 'module' object has no attribute 'SemLock'
/usr/lib/python3.4/multiprocessing/queues.py:38: AttributeError
Both traces are actually copied from Debian build logs:
2.7.9:
https://buildd.debian.org/status/fetch.php?pkg=python-astropy&arch=hurd-i386&ver=1.0~rc1-1&stamp=1422724845
3.4.2:
https://buildd.debian.org/status/fetch.php?pkg=python-astropy&arch=hurd-i386&ver=1.0~rc1-2&stamp=1423153281
Neither for 2.7.9 nor for 3.4.2 this behaviour is documented. Also, I would
expect to have a NotImplementedError and not an ImportError or an
AttributeError in such a case.
Please:
* document the behaviour of multiprocessing.Queue() in the case of an absent
sem_open for both Python2 and Python3
* Consider raising NotImplementedError or being consistent in some other way.
----------
components: Library (Lib)
messages: 235474
nosy: olebole
priority: normal
severity: normal
status: open
title: Inconsistent behaviour of multiprocessing.Queue() if sem_open is not
implemented
type: behavior
versions: Python 2.7, Python 3.4
_______________________________________
Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue23400>
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