Fix MultiThreadedExecutor spinning (backport #315) #321
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…h MultiThreadedExecutor (#315) Co-authored-by: Alejandro Hernández Cordero <[email protected]> (cherry picked from commit 4503507)
ahcorde
approved these changes
Jun 3, 2024
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I noticed that the MultiThreadedExecutor was not operating in a multi-threaded manner, so I made some changes.
From my review of the rclcpp code, it appears that the current rclcpp::MultiThreadedExecutor only implements spin(), and spin_once() and spin_some() simply execute the implementation from the base class rclcpp::Executor.
Implementation of MultiThreadedExecutor::spin():
Even after checking the implementation of rclcpp::Executor, I found no instances where the overridden spin is utilized. As a result, spin_once() and spin_some() seem to operate in a single-threaded mode. Indeed, in the header file of rclcpp::Executor, spin_some() and spin_once() are described as "suitable for a single-threaded model of execution."
Additionally, similar observations were made in a related pull request for rclcpp.
ros2/rclcpp#2454
There was also an old issue related to this problem, but it seems to have been closed without appropriate changes.
ros2/rclcpp#85
Therefore, in this pull request, I changed the implementation to use spin() instead of spin_once() for MultiThreadedExecutor. Consequently, the stop_ flag became unnecessary and was removed. It has been confirmed that the spin thread terminates correctly with executor_->cancel(), without using the stop_ flag.
As a side note, I would like to mention that MultiThreadedExecutor::spin() is also used in the ros2_control_node.
This is an automatic backport of pull request #315 done by Mergify.