Hello @ptrblck adding more details,
The code that gets stuck
$ CUDA_VISIBLE_DEVICES=0,1 python -m torch.distributed.launch --nproc_per_node=2 gpu_test_script.py
/home/user/.conda/envs/torch1p9/lib/python3.8/site-packages/torch/distributed/launch.py:177: FutureWarning: The module torch.distributed.launch is deprecated
and will be removed in future. Use torch.distributed.run.
Note that --use_env is set by default in torch.distributed.run.
If your script expects `--local_rank` argument to be set, please
change it to read from `os.environ['LOCAL_RANK']` instead. See
https://pytorch.org/docs/stable/distributed.html#launch-utility for
further instructions

  warnings.warn(
*****************************************
Setting OMP_NUM_THREADS environment variable for each process to be 1 in default, to avoid your system being overloaded, please further tune the variable for optimal performance in your application as needed.
*****************************************
fc1.weight Parameter containing:
tensor([[ 0.0018,  0.6833],
        [-0.4977, -0.3072]], device='cuda:0', requires_grad=True)
x tensor([[0.8429, 0.0000]], device='cuda:0', grad_fn=<FusedDropoutBackward>)
iter 0, out tensor([[0.8429, 0.0000]], device='cuda:0', grad_fn=<_DDPSinkBackward>)

upon KeyboardInterruption,
^CTraceback (most recent call last):
  File "/home/user/.conda/envs/torch1p9/lib/python3.8/runpy.py", line 194, in _run_module_as_main
    return _run_code(code, main_globals, None,
  File "/home/user/.conda/envs/torch1p9/lib/python3.8/runpy.py", line 87, in _run_code
    exec(code, run_globals)
  File "/home/user/.conda/envs/torch1p9/lib/python3.8/site-packages/torch/distributed/launch.py", line 191, in <module>
    main()
  File "/home/user/.conda/envs/torch1p9/lib/python3.8/site-packages/torch/distributed/launch.py", line 187, in main
    launch(args)
  File "/home/user/.conda/envs/torch1p9/lib/python3.8/site-packages/torch/distributed/launch.py", line 173, in launch
    run(args)
  File "/home/user/.conda/envs/torch1p9/lib/python3.8/site-packages/torch/distributed/run.py", line 688, in run
    elastic_launch(
  File "/home/user/.conda/envs/torch1p9/lib/python3.8/site-packages/torch/distributed/launcher/api.py", line 131, in __call__
    return launch_agent(self._config, self._entrypoint, list(args))
  File "/home/user/.conda/envs/torch1p9/lib/python3.8/site-packages/torch/distributed/launcher/api.py", line 252, in launch_agent
    result = agent.run()
  File "/home/user/.conda/envs/torch1p9/lib/python3.8/site-packages/torch/distributed/elastic/metrics/api.py", line 125, in wrapper
    result = f(*args, **kwargs)
  File "/home/user/.conda/envs/torch1p9/lib/python3.8/site-packages/torch/distributed/elastic/agent/server/api.py", line 700, in run
    result = self._invoke_run(role)
  File "/home/user/.conda/envs/torch1p9/lib/python3.8/site-packages/torch/distributed/elastic/agent/server/api.py", line 828, in _invoke_run
    time.sleep(monitor_interval)
KeyboardInterrupt

Version,
$ python -c "import torch;print(torch.__version__)"
1.10.0.dev20210721

/usr/local/cuda-11.4/bin/nvcc
(torch1p9) user@ampere:~/Project$ nvcc -V
nvcc: NVIDIA (R) Cuda compiler driver
Copyright (c) 2005-2021 NVIDIA Corporation
Built on Wed_Jun__2_19:15:15_PDT_2021
Cuda compilation tools, release 11.4, V11.4.48
Build cuda_11.4.r11.4/compiler.30033411_0