Can we at least include the fix, until we can come up with a better test?

That test fails on 3.9 as well as 3.10 and main.

With a 3.9 build and the test in #27194:

./python -m test test_threading -R :
0:00:00 load avg: 0.95 Run tests sequentially
0:00:00 load avg: 0.95 [1/1] test_threading
beginning 9 repetitions
123456789
...test test_threading failed -- Traceback (most recent call last):
  File "/home/mark/repos/cpython/Lib/test/test_threading.py", line 1479, in test_can_interrupt_tight_loops
    self.assertNotEqual(iterations, 0)
AssertionError: 0 == 0



I don't know what the underlying issue is.

Can you observe a failure without the -R flag?