Question

I have two threads, communicating with each other; each thread employs ‘while(1) ..’. Now I need to let the threads exit upon a specific condition met, and therefore finish the application.

My question: is it safe to just ‘return (NULL)’ from the thread, or do I have to use ‘pthread_exit’ or ‘pthread_join’ functions as well?

Answer 1

It is safe to return null from the thread functions; the code that waits for them should be OK.

POSIX says of pthread_exit():

An implicit call to pthread_exit() is made when a thread other than the thread in which main() was first invoked returns from the start routine that was used to create it.

You do need something to wait for the thread with pthread_join() unless the thread was created with the detached attribute or detached later with pthread_detach().