Interpreter doesn't exist if s3 object is not closed

I have this absolutely minimal program:

import s3fs
s3 = s3fs.S3FileSystem().open("bucket/file", "wb")
print("END")

Taking a look at this, I would expect that if you start it with python program.py, it will print an END and exit. Instead it prints END and never exits.
If I put an s3.close() it works as expected.

Printing a stack trace after print gives:

Current thread 0x00007f102cfc2740 (most recent call first):
  File "/usr/local/lib/python3.10/threading.py", line 324 in wait
  File "/usr/local/lib/python3.10/threading.py", line 600 in wait
  File "/usr/local/lib/python3.10/site-packages/fsspec/asyn.py", line 59 in sync
  File "/usr/local/lib/python3.10/site-packages/fsspec/asyn.py", line 91 in wrapper
  File "/usr/local/lib/python3.10/site-packages/s3fs/core.py", line 1970 in commit
  File "/usr/local/lib/python3.10/site-packages/s3fs/core.py", line 1961 in _upload_chunk
  File "/usr/local/lib/python3.10/site-packages/fsspec/spec.py", line 1522 in flush
  File "/usr/local/lib/python3.10/site-packages/fsspec/spec.py", line 1651 in close
  File "/usr/local/lib/python3.10/site-packages/fsspec/spec.py", line 1673 in __del__

Packages:

$ pip freeze
aiobotocore==2.0.1
aiohttp==3.8.1
aioitertools==0.8.0
aiosignal==1.2.0
async-timeout==4.0.2
attrs==21.2.0
botocore==1.22.8
charset-normalizer==2.0.9
frozenlist==1.2.0
fsspec==2021.11.1
idna==3.3
jmespath==0.10.0
multidict==5.2.0
python-dateutil==2.8.2
s3fs==2021.11.1
six==1.16.0
urllib3==1.26.7
wrapt==1.13.3
yarl==1.7.2
$ python -V
Python 3.10.1

(but it fails with older python and module versions as well, for eg. we run 2021.8.1 in prod)

Start with the minimal Python reproduction and the stack frames in fsspec/asyn.py, s3fs/core.py, and fsspec/spec.py, focusing on the upload and destructor paths. Check how an unclosed S3 object is finalized and whether the process can exit without an explicit close while preserving the expected upload behavior. Done means the reproduction prints END and exits normally.