[Win] Call subprocess.Popen() twice makes Thread.join() interruptible and deadlock

[zby1234]

BPO	43409
Nosy	@pfmoore, @tjguk, @zware, @eryksun, @zooba
Superseder	bpo-21822: [Windows] KeyboardInterrupt during Thread.join hangs that Thread
Files	joinbug.py

^{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 2021-03-05.17:51:25.495>
created_at = <Date 2021-03-05.16:16:07.390>
labels = ['type-bug', '3.9', 'OS-windows']
title = '[Win] Call subprocess.Popen() twice makes Thread.join() interruptible and deadlock'
updated_at = <Date 2021-03-05.17:51:25.494>
user = 'https://bugs.python.org/zby1234'

bugs.python.org fields:

activity = <Date 2021-03-05.17:51:25.494>
actor = 'eryksun'
assignee = 'none'
closed = True
closed_date = <Date 2021-03-05.17:51:25.495>
closer = 'eryksun'
components = ['Windows']
creation = <Date 2021-03-05.16:16:07.390>
creator = 'zby1234'
dependencies = []
files = ['49853']
hgrepos = []
issue_num = 43409
keywords = []
message_count = 2.0
messages = ['388156', '388160']
nosy_count = 6.0
nosy_names = ['paul.moore', 'tim.golden', 'zach.ware', 'eryksun', 'steve.dower', 'zby1234']
pr_nums = []
priority = 'normal'
resolution = 'duplicate'
stage = 'resolved'
status = 'closed'
superseder = '21822'
type = 'behavior'
url = 'https://bugs.python.org/issue43409'
versions = ['Python 3.9']

[zby1234]

Please run joinbug.py and press Ctrl-C twice.

============= The output =============

1st join
PLEASE PRESS CTRL-C TWICE, IGNORE THE 'Press any key to continue'
Press any key to continue . . . Press any key to continue . . .

thread exit
Traceback (most recent call last):
  File "D:\xxx\joinbug.py", line 21, in <module>
    t.join() # subprocess.Popen() makes join() can be interrupted
  File "C:\Users\xxx\AppData\Local\Programs\Python\Python39\lib\threading.py", line 1033, in join
    self._wait_for_tstate_lock()
  File "C:\Users\xxx\AppData\Local\Programs\Python\Python39\lib\threading.py", line 1049, in _wait_for_tstate_lock
    elif lock.acquire(block, timeout):
KeyboardInterrupt
2nd join
(stuck here)

============= Expected behaviour =============
either join uninterruptible
or the 2nd join doesn't deadlock.

[eryksun]

This is a variation on bpo-21822. If join() is called in the main thread, and it gets interrupted immediately after the lock.acquire(block, timeout) call, then subsequent calls will hang. In Windows, the acquire() call is not interruptible with Ctrl+C, so the KeyboardInterrupt gets raised immediately after acquire() returns, so the problem is easy to reproduce in Windows.