ROS 2 MultiThreadedExecutor callback thread‑safety requirement

ROS 2 MultiThreadedExecutor callback execution

The MultiThreadedExecutor dispatches user callbacks from a thread pool without internal locking.

Goal: clarify whether the executor imposes a thread‑safety requirement on callbacks that access shared resources.

Uncertainty: the documentation does not state if callbacks must be synchronized, yet concurrent invocations can cause data races.

• Is thread‑safety required for all callbacks run by a MultiThreadedExecutor?
• Does the executor provide any synchronization primitives or guarantees for shared state?
• What validation approach should be used to confirm that a callback implementation is safe under concurrent execution?