Regression - Concurrent Futures

[jonathan-lp]

BPO	36120
Nosy	@csabella
Superseder	bpo-35797: concurrent.futures.ProcessPoolExecutor does not work in venv on Windows

^{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 2019-02-26.13:33:29.458>
created_at = <Date 2019-02-26.11:34:43.774>
labels = ['3.7', '3.8']
title = 'Regression - Concurrent Futures'
updated_at = <Date 2019-02-26.13:33:29.457>
user = 'https://bugs.python.org/jonathan-lp'

bugs.python.org fields:

activity = <Date 2019-02-26.13:33:29.457>
actor = 'cheryl.sabella'
assignee = 'none'
closed = True
closed_date = <Date 2019-02-26.13:33:29.458>
closer = 'cheryl.sabella'
components = []
creation = <Date 2019-02-26.11:34:43.774>
creator = 'jonathan-lp'
dependencies = []
files = []
hgrepos = []
issue_num = 36120
keywords = []
message_count = 5.0
messages = ['336649', '336650', '336652', '336654', '336666']
nosy_count = 2.0
nosy_names = ['cheryl.sabella', 'jonathan-lp']
pr_nums = []
priority = 'normal'
resolution = 'duplicate'
stage = 'resolved'
status = 'closed'
superseder = '35797'
type = None
url = 'https://bugs.python.org/issue36120'
versions = ['Python 3.7', 'Python 3.8']

[jonathan-lp]

I'm using Concurrent Futures to run some work in parallel (futures.ProcessPoolExecutor) on windows 7 x64. The code works fine in 3.6.3, and 3.5.x before that.
I've just upgraded to 3.7.2 and it's giving me these errors:

Process SpawnProcess-6:
Traceback (most recent call last):
  File "c:\_libs\Python37\lib\multiprocessing\process.py", line 297, in _bootstrap
    self.run()
  File "c:\_libs\Python37\lib\multiprocessing\process.py", line 99, in run
    self._target(*self._args, **self._kwargs)
  File "c:\_libs\Python37\lib\concurrent\futures\process.py", line 226, in _process_worker
    call_item = call_queue.get(block=True)
  File "c:\_libs\Python37\lib\multiprocessing\queues.py", line 93, in get
    with self._rlock:
  File "c:\_libs\Python37\lib\multiprocessing\synchronize.py", line 95, in __enter__
    return self._semlock.__enter__()
PermissionError: [WinError 5] Access is denied

If I switch back to the 3.6.3 venv it works fine again.

[jonathan-lp]

There's also this error too:

Traceback (most recent call last):
  File "c:\_libs\Python37\lib\multiprocessing\process.py", line 297, in _bootstrap
    self.run()
  File "c:\_libs\Python37\lib\multiprocessing\process.py", line 99, in run
    self._target(*self._args, **self._kwargs)
  File "c:\_libs\Python37\lib\concurrent\futures\process.py", line 226, in _process_worker
    call_item = call_queue.get(block=True)
  File "c:\_libs\Python37\lib\multiprocessing\queues.py", line 94, in get
    res = self._recv_bytes()
  File "c:\_libs\Python37\lib\multiprocessing\synchronize.py", line 98, in __exit__
    return self._semlock.__exit__(*args)
OSError: [WinError 6] The handle is invalid

[csabella]

Thank you for the report. Please add a script that contains the least amount of code that would replicate the error. Thanks!

From the devguide:

last but not least, you have to describe the problem in detail, including what you expected to happen, what did happen, and how to replicate the problem in the Comment field. Be sure to include whether any extension modules were involved, and what hardware and software platform you were using (including version information as appropriate).

[jonathan-lp]

The "ProcessPoolExecutor Example" on this page breaks for me:

https://docs.python.org/3/library/concurrent.futures.html

[csabella]

Thank you. I just tried running the example and it worked OK for me in the 3.8 master build. I believe your report is a duplicate of bpo-35797.