Function do_cv_wait

freebsd/kern/kern_umtx.c:2534–2620

}

static int
do_cv_wait(struct thread *td, struct ucond *cv, struct umutex *m,
    struct timespec *timeout, u_long wflags)
{
	struct abs_timeout timo;
	struct umtx_q *uq;
	uint32_t flags, clockid, hasw;
	int error;

	uq = td->td_umtxq;
	error = fueword32(&cv->c_flags, &flags);
	if (error == -1)
		return (EFAULT);
	error = umtx_key_get(cv, TYPE_CV, GET_SHARE(flags), &uq->uq_key);
	if (error != 0)
		return (error);

	if ((wflags & CVWAIT_CLOCKID) != 0) {
		error = fueword32(&cv->c_clockid, &clockid);
		if (error == -1) {
			umtx_key_release(&uq->uq_key);
			return (EFAULT);
		}
		if (clockid < CLOCK_REALTIME ||
		    clockid >= CLOCK_THREAD_CPUTIME_ID) {
			/* hmm, only HW clock id will work. */
			umtx_key_release(&uq->uq_key);
			return (EINVAL);
		}
	} else {
		clockid = CLOCK_REALTIME;
	}

	umtxq_lock(&uq->uq_key);
	umtxq_busy(&uq->uq_key);
	umtxq_insert(uq);
	umtxq_unlock(&uq->uq_key);

	/*
	 * Set c_has_waiters to 1 before releasing user mutex, also
	 * don't modify cache line when unnecessary.
	 */
	error = fueword32(&cv->c_has_waiters, &hasw);
	if (error == 0 && hasw == 0)
		suword32(&cv->c_has_waiters, 1);

	umtxq_unbusy_unlocked(&uq->uq_key);

	error = do_unlock_umutex(td, m, false);

	if (timeout != NULL)
		abs_timeout_init(&timo, clockid, (wflags & CVWAIT_ABSTIME) != 0,
		    timeout);

	umtxq_lock(&uq->uq_key);
	if (error == 0) {
		error = umtxq_sleep(uq, "ucond", timeout == NULL ?
		    NULL : &timo);