Buzz Lock

buzzLock.c

int buzz_lock(buzz_t lock) {
...
	if(full_active_threads(lock)) {
		add_to_waiting_threads(thread, lock);

		do {
			wait(lock);

			if(is_gold(thread)) {
				if(is_old(thread, lock)) {
					add_active(thread, lock);
				}
			  else if(num_black_waiting(lock) <= 0) {
					add_active(thread, lock);
				}
			}
			else {
				if(num_old_gold_waiting(lock) <= 0) {
					add_active(thread, lock);
				}
			}
			free_threads = lock.max_active_threads - lock.active_threads;
		} while(free_threads <= 0);
	}
	else {
		add_active(thread, lock);
	}
...
}

Intent: Two colors of threads, gold and black. Threads try to acquire lock, and priority is given to old gold threads, then black threads, and lastly gold threads.