Multiprocessing.Queue created by sub-process fails when used in sub-sub-process ("bad file descriptor" in q.get())

[bbutler]

BPO	5155
Files	queue_test.py: Test script

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2009-06-30.17:14:17.766>
created_at = <Date 2009-02-05.01:52:52.621>
labels = ['library', 'type-crash']
title = 'Multiprocessing.Queue created by sub-process fails when used in sub-sub-process ("bad file descriptor" in q.get())'
updated_at = <Date 2009-06-30.17:14:17.764>
user = 'https://bugs.python.org/bbutler'

bugs.python.org fields:

activity = <Date 2009-06-30.17:14:17.764>
actor = 'jnoller'
assignee = 'jnoller'
closed = True
closed_date = <Date 2009-06-30.17:14:17.766>
closer = 'jnoller'
components = ['Library (Lib)']
creation = <Date 2009-02-05.01:52:52.621>
creator = 'bbutler'
dependencies = []
files = ['12944']
hgrepos = []
issue_num = 5155
keywords = []
message_count = 6.0
messages = ['81183', '81184', '84947', '89196', '89902', '89944']
nosy_count = 3.0
nosy_names = ['OG7', 'jnoller', 'bbutler']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = None
status = 'closed'
superseder = None
type = 'crash'
url = 'https://bugs.python.org/issue5155'
versions = ['Python 2.6', 'Python 3.0']

[bbutler]

(Note: This issue only happens on linux - on Windows things work fine.)

Please see the attached script.

The script creates a process (TestProcess()). That process runs and
creates a sub-process (TestSubProcess()). When TestSubProcess tries to
access a Queue created by TestProcess, the .get() call fails with the
following stack trace:

Process Process-1:1:
Traceback (most recent call last):
  File "/opt/python2.6/lib/python2.6/multiprocessing/process.py", line
231, in _bootstrap
    self.run()
  File "/opt/python2.6/lib/python2.6/multiprocessing/process.py", line
88, in run
    self._target(*self._args, **self._kwargs)
  File "queue_test.py", line 7, in TestSubProcess
    item = q.get()                        # Fails with IOError if queue
created in TestProcess
  File "/opt/python2.6/lib/python2.6/multiprocessing/queues.py", line
91, in get
    res = self._recv()
IOError: [Errno 9] Bad file descriptor

If the same queue is created by main (top level), TestSubProcess
accesses it with no errors. This behavior can be stimulated by
uncommenting the q = multiprocessing.Queue() line in TestProcess.

Tested using:
Python 2.6.1 (r261:67517, Dec 4 2008, 16:51:00) [MSC v.1500 32 bit
(Intel)] on win32
(Installed using binary installer, windows XPSP2)

*No problems*

Python 2.6.1 (r261:67515, Jan 6 2009, 15:23:19) [GCC 4.2.4 (Ubuntu
4.2.4-1ubuntu3)] on linux2
(Compiled from source due to ubuntu 8.04 (Hardy) not having python2.6 yet)

*Fails on q.get() in TestSubProcess*

[bbutler]

Also reproduced in Python3.0 on OSX 10.5

[bbutler]

Quick note: Have tracked this down to what appears to be buggy behaviour
on the part of os.pipe() when called from within a Process.

First invocation of os.pipe() in a Process returns (0,x) - stdin(?)
resulting in the 'bad file descriptor' error.

Interactive prompt test follows:

>>> import multiprocessing as MP, os
>>> def r():  print os.pipe(), os.pipe(), os.pipe()
... 
>>> r()
(9, 10) (11, 12) (13, 14)
>>> MP.Process(target=r).start()
(0, 15) (16, 17) (18, 19)
>>> MP.Process(target=r).start()
(0, 15) (16, 17) (18, 19)

[OG7]

bpo-5313 seems to be the culprit.

[jnoller]

Patch attached to bpo-5313, please review.

[jnoller]

Committed in r73708 on trunk