[New-bugs-announce] [issue45077] multiprocessing.Pool(64) crashes on Windows

[Kagami Sascha Rosylight]

New submission from Kagami Sascha Rosylight <saschanaz at outlook.com>:

Similar issue as the previous issue 26903.

```
Python 3.9.7 (tags/v3.9.7:1016ef3, Aug 30 2021, 20:19:38) [MSC v.1929 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import multiprocessing
>>> multiprocessing.cpu_count()
64
>>> multiprocessing.Pool(multiprocessing.cpu_count())
Exception in thread Thread-1:
Traceback (most recent call last):
<multiprocessing.pool.Pool state=RUN pool_size=64>
  File "C:\Users\sasch\AppData\Local\Programs\Python\Python39\lib\threading.py", line 973, in _bootstrap_inner
>>>     self.run()
  File "C:\Users\sasch\AppData\Local\Programs\Python\Python39\lib\threading.py", line 910, in run
    self._target(*self._args, **self._kwargs)
  File "C:\Users\sasch\AppData\Local\Programs\Python\Python39\lib\multiprocessing\pool.py", line 519, in _handle_workers
    cls._wait_for_updates(current_sentinels, change_notifier)
  File "C:\Users\sasch\AppData\Local\Programs\Python\Python39\lib\multiprocessing\pool.py", line 499, in _wait_for_updates
    wait(sentinels, timeout=timeout)
  File "C:\Users\sasch\AppData\Local\Programs\Python\Python39\lib\multiprocessing\connection.py", line 884, in wait
    ready_handles = _exhaustive_wait(waithandle_to_obj.keys(), timeout)
  File "C:\Users\sasch\AppData\Local\Programs\Python\Python39\lib\multiprocessing\connection.py", line 816, in _exhaustive_wait
    res = _winapi.WaitForMultipleObjects(L, False, timeout)
ValueError: need at most 63 handles, got a sequence of length 66
```

----------
components: Windows
messages: 400832
nosy: paul.moore, saschanaz, steve.dower, tim.golden, zach.ware
priority: normal
severity: normal
status: open
title: multiprocessing.Pool(64) crashes on Windows
type: behavior
versions: Python 3.9

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue45077>
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