new ddp is blocked

[chenjingcheng]

iHello, thank you very much for your project. I'm testing with multiple GPUs, but the code is blocking at ：
self.ddp_model = DDP(
self.model,
device_ids=[dist_util.dev()],
output_device=dist_util.dev(),
broadcast_buffers=False,
bucket_cap_mb=128,
find_unused_parameters=find_unused_parameters,
)
I've tested other DDP codes and they work fine. Could you please give me some advice on where the problem might be? Thank you!