Flake8 hangs on a windows machine with > 61 procs when running on > 1 file

[pylbert]

how did you install flake8?

D:\temp>uv venv flake8
Using CPython 3.10.15
Creating virtual environment at: flake8
Activate with: flake8\Scripts\activate

D:\temp>flake8\Scripts\activate

(flake8) D:\temp>uv pip install flake8
Using Python 3.10.15 environment at: flake8
Resolved 4 packages in 85ms
Prepared 4 packages in 110ms
░░░░░░░░░░░░░░░░░░░░ [0/4] Installing wheels...
Installed 4 packages in 115ms
 + flake8==7.1.1
 + mccabe==0.7.0
 + pycodestyle==2.12.1
 + pyflakes==3.2.0

unmodified output of flake8 --bug-report

{
  "platform": {
    "python_implementation": "CPython",
    "python_version": "3.10.15",
    "system": "Windows"
  },
  "plugins": [
    {
      "plugin": "mccabe",
      "version": "0.7.0"
    },
    {
      "plugin": "pycodestyle",
      "version": "2.12.1"
    },
    {
      "plugin": "pyflakes",
      "version": "3.2.0"
    }
  ],
  "version": "7.1.1"
}

describe the problem

what I expected to happen

Flake8 should run and exit with defaults from the command line

Runs/does not exit (hangs after printing stack trace):

(flake8) D:\temp>flake8 testit0.py testit1.py
Exception in thread Thread-1 (_handle_workers):
Traceback (most recent call last):
  File "lib\threading.py", line 1016, in _bootstrap_inner
    self.run()
  File "lib\threading.py", line 953, in run
    self._target(*self._args, **self._kwargs)
  File "lib\multiprocessing\pool.py", line 522, in _handle_workers
    cls._wait_for_updates(current_sentinels, change_notifier)
  File "lib\multiprocessing\pool.py", line 502, in _wait_for_updates
    wait(sentinels, timeout=timeout)
  File "lib\multiprocessing\connection.py", line 879, in wait
    ready_handles = _exhaustive_wait(waithandle_to_obj.keys(), timeout)
  File "lib\multiprocessing\connection.py", line 811, in _exhaustive_wait
    res = _winapi.WaitForMultipleObjects(L, False, timeout)
ValueError: need at most 63 handles, got a sequence of length 194   # <-- hangs here

Runs/exits (does NOT hang) when constrained to 61 jobs:

(flake8) D:\temp>flake8 testit0.py testit1.py --jobs 61

See possible fix #1964

[asottile]

this issue claims that this is fixed -- what version of windows are you running on? python/cpython#71090 python/cpython#84444

[pylbert]

Ah, ok - the cpython would be much preferred to a work around here. I can close my issue and pr.

I'm seeing this on:

Python 3.10.15 with flake8 7.1.0 on Windows Server 2022 Standard 21H2

(note: #1964 originally mentioned Windows 11, this should have been Windows Server 2022 - I've updated the PR text)