Physics step hangs indefinitely and GPU usage at 100%

[jeferal]

Description

Hello. I encounter an issue where the physics step seems to hang indefinitely. I have only noticed this in an RL training when I use a model that has closed linkages. I implemented the closed linkages by excluding a joint from the loop as mentioned here:
isaac-sim/IsaacLab#4593 (comment)

(Closed linkages might not be the issue, but mentioning just in case)

Here is where I see it seems to hang in the physics step:

Thread 3223885 (idle): "MainThread"
    _step (api/physics_context/physics_context.py:565)
    step (api/simulation_context/simulation_context.py:713)
    step (isaaclab/sim/simulation_context.py:545)
    step (isaaclab/envs/direct_rl_env.py:357)

The GPU usage is at 100% when hanging in the physics step.

Have you encountered this issue in the past? Is there any other issue related to this?

Thanks a lot for the help.

Isaac Sim version

5.1.0

Operating System (OS)

Ubuntu 24.04

GPU Name

RTX 3090

GPU Driver and CUDA versions

570.211.01 Cuda 12.8

Logs

No response

Additional information

No response

[vick-yu]

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