test_os TestInvalidFD.test_closerange causes test_pipes hang in certain circumstances on linux

[bitdancer]

BPO	6542
Nosy	@avassalotti, @bitdancer
Files	issue6542.patch

^{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 = 'https://github.com/bitdancer'
closed_at = <Date 2009-07-22.18:30:52.899>
created_at = <Date 2009-07-22.02:32:02.293>
labels = ['type-bug', 'tests']
title = 'test_os TestInvalidFD.test_closerange causes test_pipes hang in certain circumstances on linux'
updated_at = <Date 2009-07-22.18:30:52.897>
user = 'https://github.com/bitdancer'

bugs.python.org fields:

activity = <Date 2009-07-22.18:30:52.897>
actor = 'r.david.murray'
assignee = 'r.david.murray'
closed = True
closed_date = <Date 2009-07-22.18:30:52.899>
closer = 'r.david.murray'
components = ['Tests']
creation = <Date 2009-07-22.02:32:02.293>
creator = 'r.david.murray'
dependencies = []
files = ['14535']
hgrepos = []
issue_num = 6542
keywords = ['patch']
message_count = 7.0
messages = ['90791', '90793', '90796', '90799', '90801', '90816', '90818']
nosy_count = 2.0
nosy_names = ['alexandre.vassalotti', 'r.david.murray']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue6542'
versions = ['Python 2.6', 'Python 3.1', 'Python 2.7', 'Python 3.2']

[bitdancer]

The test sequence "test_ttk_guionly test_os test_pipes" hangs almost
every time when run on Gentoo x86 and Ubuntu x86_64 (at least). Note
that this is without the gui resource, so the ttk tests aren't being run.

Commenting out test_closerange in TestInvalidFD in test_os clears the
hang. Playing around with which module imports are commented out in
test_ttk_guionly can clear the hang, but test_pipes then produces the
following errors:

======================================================================
ERROR: testSimplePipe1 (test.test_pipes.SimplePipeTests)
----------------------------------------------------------------------

Traceback (most recent call last):
  File "/home/rdmurray/python/py3k/Lib/test/test_pipes.py", line 23, in
testSimplePipe1
    f = t.open(TESTFN, 'w')
  File "/home/rdmurray/python/py3k/Lib/pipes.py", line 148, in open
    return self.open_w(file)
  File "/home/rdmurray/python/py3k/Lib/pipes.py", line 168, in open_w
    return os.popen(cmd, 'w')
  File "/home/rdmurray/python/py3k/Lib/os.py", line 636, in popen
    bufsize=buffering)
  File "/home/rdmurray/python/py3k/Lib/subprocess.py", line 646, in __init__
    errread, errwrite)
  File "/home/rdmurray/python/py3k/Lib/subprocess.py", line 1138, in
_execute_child
    os.close(errpipe_read)
OSError: [Errno 9] Bad file descriptor

======================================================================
FAIL: testSimplePipe2 (test.test_pipes.SimplePipeTests)
----------------------------------------------------------------------

Traceback (most recent call last):
  File "/home/rdmurray/python/py3k/Lib/test/test_pipes.py", line 33, in
testSimplePipe2
    self.assertEqual(open(TESTFN2).read(), 'HELLO WORLD #2')
AssertionError: '' != 'HELLO WORLD #2'

The first of these appears almost every time, the second one seldom.
Occasinally both tests pass.

[bitdancer]

It appears that TestInvalidFD.test_closerange is in fact closing a valid
file descriptor in this case. I'm not sure how to fix the test...nor
why the close produced the results it does.

[bitdancer]

Here's another buildbot failure that's probably the same thing:

http://www.python.org/dev/buildbot/all/x86%20osx.5%203.x/builds/1220

[bitdancer]

Patch to skip test if it can't get a range of invalid file descriptors
to test. The test sequence passes with this patch in place.

[avassalotti]

Oh, nice catch. That patch looks fine. However, I would probably add a
comment why the fstat checks are required.

[bitdancer]

Applied in r74171 to py3k and r74172 to 3.1.

It occurs to me that I should backport this to trunk, so I'm leaving the
issue open until I do that.

[bitdancer]

Backported to trunk in r74175, and 2.6 in r74176.