RMW API calls hang in service request callback

[emersonknapp]

System Info

• OS
  • Ubuntu 22.04
• ROS version and installation type
  • rolling/source
• RTI Connext DDS version and installation type
  • Pro 6.0.1/apt
• RMW version or commit hash
  • rolling

Bug Description

When a service callback is registered with rcl_service_set_on_new_request_callback, if rmw_take is called within that callback, a deadlock occurs and the program hangs.

Expected Behavior

Either the API allows this behavior and it works, or it is explicitly disallowed and returns an error code.

How to Reproduce

Run the test in ros2/rcl#1081

Workarounds

#123 fixes the problem from what I can tell, but I'm not 100% sure it's a good idea

[emersonknapp]

@asorbini - maybe you could take a look and see what you think about the problem / proposed fix. You can see my investigation at ros2/rcl#1052 (comment) where I figured out the issue, shows stack traces.

[emersonknapp]

@asorbini could you take a look at this?