if (timer->it.cpu.firing) return TIMER_RETRY;  if (unlikely(p == NULL)) return 0;  if (!list_empty(&timer->it.cpu.entry)) {
if (likely(p != NULL)) {
int posix_cpu_timer_del(struct k_itimer *timer){	struct task_struct *p = timer->it.cpu.task;	if (timer->it.cpu.firing)		return TIMER_RETRY;	if (unlikely(p == NULL))		return 0;	if (!list_empty(&timer->it.cpu.entry)) {		read_lock(&tasklist_lock);		if (unlikely(p->signal == NULL)) {			/*			 * We raced with the reaping of the task.			 * The deletion should have cleared us off the list.			 */			BUG_ON(!list_empty(&timer->it.cpu.entry));		} else {			/*			 * Take us off the task's timer list.			 */			spin_lock(&p->sighand->siglock);			list_del(&timer->it.cpu.entry);			spin_unlock(&p->sighand->siglock);		}		read_unlock(&tasklist_lock);	}	put_task_struct(p);	return 0;}