nav2_controller: stop mutex from deadlocking on parameter change

[dkuenster]

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Basic Info

Info	Please fill out this column
Ticket(s) this addresses	#2833
Primary OS tested on	Debian
Robotic platform tested on	gazebo simulation

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Description of contribution in a few bullet points

• Don't cause a deadlock when we try to dynamically change controller
  parameters while the controller is running.
• Also provide a appropriate
  error message on failure to change parameters.

Description of documentation updates required from your changes

Shouldn't be necessary

Future work that may be required in bullet points

• Maybe add correct handling of dynamic parameter changes to the plugins

For Maintainers:

• Check that any new parameters added are updated in navigation.ros.org
• Check that any significant change is added to the migration guide
• Check that any new features OR changes to existing behaviors are reflected in the tuning guide
• Check that any new functions have Doxygen added
• Check that any new features have test coverage
• Check that any new plugins is added to the plugins page
• If BT Node, Additionally: add to BT's XML index of nodes for groot, BT package's readme table, and BT library lists

[mergify]

@dkuenster, please properly fill in PR template in the future. @SteveMacenski, use this instead.

• Check that any new parameters added are updated in navigation.ros.org
• Check that any significant change is added to the migration guide
• Check that any new features OR changes to existing behaviors are reflected in the tuning guide
• Check that any new functions have Doxygen added
• Check that any new features have test coverage
• Check that any new plugins is added to the plugins page
• If BT Node, Additionally: add to BT's XML index of nodes for groot, BT package's readme table, and BT library lists

[SteveMacenski]

Any update? Does my concern make sense or is there something I'm overlooking?

[SteveMacenski]

Dynamic Callback LGTM, but I think the main server should require a lock strictly since that's the main task and is latency sensitive

[SteveMacenski]

No worries, just circling back since I hadn't heard back in a bit! :smile

[SteveMacenski]

Awesome! Thanks! That return warning will be helpful too