cc [options] -Kthread file
In this implementation, a multiplexed thread calling thr_yield will yield its lightweight process (LWP) only if another thread of higher or equal priority is runnable. In that case, the calling thread will be halted and it will be placed on the end of its priority queue. If only lower priority threads are runnable, or no other thread is runnable, the caller will continue executing. Likewise, a bound thread calling thr_yield will cause its LWP to yield the processor if another thread of higher or equal priority is runnable.
This function should be viewed as a hint from the caller to the system, indicating that the caller has reached a point at which it is convenient to yield the processor to other threads.
thr_yield requires no special permissions or privilege.