gistfile1.txt

struct spinlock s;
int doomsday = 0;

doomsday_thr() {
   for (;;) {
   	spin_lock(&s);
   	while (doomsday == 0) {
   		spin_unlock(&s);
   		/* XXX */
   		tsleep(BADNESS, 0, "waiting-for-end", 0);
 		spin_lock(&s);
   	}
   	go_for_broke();
   	spin_unlock(&s);
   }
}

doomsday_button_intr() {
	spin_lock(&s);
	doomsday = 1;
	spin_unlock(&s);
	wakeup(BADNESS);
}