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ros::ok() within pthread

asked 2012-02-08 05:14:57 -0500

rplankenhorn gravatar image

updated 2012-02-09 01:03:34 -0500

I am have a couple of threads that run in a node. The threads have a while(ros::ok()) infinite loop inside. The problem is that when I Ctrl-C my program, it has to escalate to a SIGTERM because the ros::ok() variable never goes false. I also tried the ros::isShuttingDown() variable and this never goes true.

How should I handle the pthreads so that they exit when the rest of the program exits?

I launch threads with:

pthread_t thread1
pthread_create(&thread1,NULL,thread1Function,NULL);

My thread function looks something like this:

void *thread1Function(void *obj)
{
ros::Rate loop_rate(1);

while(ros::ok())
{
//Do stuff
loop_rate.sleep();
ros::spinOnce();
}

pthread_exit(NULL);
}

The loop never exits.

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answered 2012-02-09 01:42:04 -0500

rplankenhorn gravatar image

Alright I figured it out. I had GDB enabled for the module and it for some reason wasn't killing the threads. As soon as I disabled it in my launch file, the threads get killed when I Ctrl-C the program. Thanks for the suggestions.

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answered 2012-02-08 05:24:46 -0500

DimitriProsser gravatar image

updated 2012-02-09 01:26:51 -0500

I've never had a problem running ROS with threads. Are you calling ros::spinOnce() to poll for updates?

I've never used pthread, but I know for a fact that it works with boost::thread. I know that doesn't solve your issue, but it's something to consider. But since it's really just a nice wrapper for pthreads on *Nix systems, it doesn't really explain the problem.

EDIT:

Try passing a this pointer to pthread_create(). Since the ros::init() is called in the parent class, you need to have access to the ROS variables in your thread.

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Comments

See my sample code above.
rplankenhorn gravatar image rplankenhorn  ( 2012-02-09 01:03:57 -0500 )edit
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answered 2012-02-08 13:58:42 -0500

this post is marked as community wiki

This post is a wiki. Anyone with karma >75 is welcome to improve it.

You need to provide ros a thread to use. The standard way to do this is to call ros::spin() at the bottom of your main thread.

For more information, see the threading section of the roscpp Overview

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I do this in the main thread. I launch individual threads and then drop into a while(ros::ok()) loop that exits fine when I do Ctrl-C.
rplankenhorn gravatar image rplankenhorn  ( 2012-02-09 01:04:48 -0500 )edit

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Asked: 2012-02-08 05:14:57 -0500

Seen: 2,464 times

Last updated: Feb 11 '12