[Question] Safetensors seem to block the main thread -- but torch.save does not?

[vedantroy]

I have the following code in my training loop:

                if rank == 0:
                    t = Thread(
                        target=save_file,
                        args=(model_sd, f"{cfg.model_dir}/model_{step + 1}.safetensors"),
                        daemon=True
                    )
                    t.start()

Which saves the checkpoint to disk using safetensors. However, I notice that this blocks the training loop, even though the thread should be running in the background.

When I switch the code to use torch.save, there's no issue. What should I do?