Distributed data parallel freezes without error message 
  
  
    Env: 

Ubuntu 18.04
Pytorch 1.6.0
CUDA 10.1

Actually, I am using Docker image gemfield/pytorch:1.6.0-devel which stated in https://github.com/DeepVAC/deepvac (same with above env), and use PyTorch DDP (by use the class DeepvacDDP in https://github.com/DeepVAC/deepvac/blob/master/deepvac/syszux_deepvac.py) to train my model, which the code worked perfect yesterday. But today when I launch the train program again, the DDP is stucked in loss.backward()， with cpu 100% and GPU 100%。 
There has no co…