@Jimmy2027:  I was able to make logging work by moving SummaryWriter creation from main process to child process, specifically remove
self.logger = SummaryWriter(dir_logs)

And add in run_epochs
exp.logger = SummaryWriter(exp.dir_logs)

So that we don’t have to folk the lock inside SummaryWriter (in _AsyncWriter https://github.com/tensorflow/tensorboard/blob/master/tensorboard/summary/writer/event_file_writer.py#L163 13). In general each child process should create their own SummaryWriter instead of forking from parent process.
Also unrelated to your issue, tensorboardX has long been deprecated and no longer actively maintained, being replaced by pytorch native support for TensorBoard since Pytorch 1.2. To use it simply replace
from tensorboardX import SummaryWriter

With
from torch.utils.tensorboard import SummaryWriter