Attached import_module_not_found.py consistently fails for me on Python 3.7.5 and earlier Python 3 versions that I have tried with 

  File "/usr/lib/python3.7/threading.py", line 926, in _bootstrap_inner
    self.run()
  File "/usr/lib/python3.7/threading.py", line 870, in run
    self._target(*self._args, **self._kwargs)
  File "import_module_not_found.py", line 8, in t2
    return __import__("tensorflow.estimator", level=0)
ModuleNotFoundError: No module named 'tensorflow.estimator

Threads in this example finish successfully if executed sequentially.

I have not tried higher versions of Python, but I cannot reproduce this on Python 2.7. 

Is this an expected behavior?

Thank you.

Attached import_deadlock.py fails with   

...
File "<frozen importlib._bootstrap>", line 980, in _find_and_load
  File "<frozen importlib._bootstrap>", line 149, in __enter__
  File "<frozen importlib._bootstrap>", line 94, in acquire
_frozen_importlib._DeadlockError: deadlock detected by _ModuleLock('tensorflow_transform.tf_metadata.metadata_io')

under the same conditions.

Possibly related: https://bugs.python.org/issue35943

Can you test this with a package that isn't tensorflow (e.g. something else in the stdlib or something created manually; basically a smaller reproducer)? It's hard to diagnose if this is really Python or not without a smaller reproducer as tensorflow might be doing some things behind the scenes that would break this due to it being an extension module.

Attaching a minimal repro with simple project hierarchy.

Repro: unpack issue38884.zip
python input_deadlock.py

(fails on Python 3.7, but not on 2.7).

input_deadlock.py in issue38884.zip has a left-over comment:
# Requires pip install tensorflow==2.0.0 tensorflow-transform==0.15.0 
Please ignore that.

The behavior changes between Python 3.2 (no deadlock) and Python 3.3 (deadlock). Deadlock also reproducible on Python 3.8.

@brett.cannon, looks like I inadvertently dropped you from nosy list, so in case you missed the updates - please take a look at issue38884.zip. Thank you.

Just checking - is issue38884.zip an acceptable repro for this issue?
Thanks.

@valentyn just assume it's good enough unless some asks otherwise. People are probably too busy right now to be looking at this and so you might be waiting a while for a more definitive answer.

I believe I'm also encountering some version of this bug while importing code from the kombu library within a multi-threaded context.

For what it's worth, I'm able to reproduce the reported deadlock (https://bugs.python.org/file48737/issue38884.zip) using python3.8 on RHEL8 and CentOS 8 builds.

More details about what I'm encountering here: https://github.com/ansible/awx/issues/5617
https://github.com/ansible/awx/issues/5617#issuecomment-591618205

My intended workaround for now is to just not use a thread (we'll see if it helps):

https://github.com/ansible/awx/pull/6093

Was able to reproduce with Python 3.9.0rc1 using issue38884.zip. macOS 10.15.5

Given that the behavior changes between Python 3.2 (no deadlock) and Python 3.3 (deadlock), this should be easily bisectable if someone has the right setup to build and run Python versions from sources in that range.