osfmk/kern/task_policy.c

1908 	thread_t target_thread = NULL;
1916 		target_thread = self;
1917 		thread_reference(target_thread);
1920 		target_thread = task_findtid(curtask, tid);
1921 		if (target_thread != NULL)
1922 			thread_reference(target_thread);
1952 		if (target_thread->taskwatch != NULL){
1964 		twp->tw_thread = target_thread;		/* holds the thread reference */
1966 		twp->tw_importance = target_thread->importance;
1970 		target_thread->taskwatch = twp;
1978 			set_thread_appbg(target_thread, setbg, INT_MIN);
1982 		target_thread = NULL;
1986 		if ((twp = target_thread->taskwatch) != NULL) {
1988 			target_thread->taskwatch = NULL;
1994 			set_thread_appbg(target_thread, 0, twp->tw_importance);
1995 			thread_deallocate(target_thread);	/* drop thread ref in twp */
2004 	if (target_thread != NULL)
2005 		thread_deallocate(target_thread);	/* drop thread ref acquired in this routine */