Function do_lock_pp

freebsd/kern/kern_umtx.c:2129–2290

* Lock a PP mutex. */

 * Lock a PP mutex.
 */
static int
do_lock_pp(struct thread *td, struct umutex *m, uint32_t flags,
    struct _umtx_time *timeout, int try)
{
	struct abs_timeout timo;
	struct umtx_q *uq, *uq2;
	struct umtx_pi *pi;
	uint32_t ceiling;
	uint32_t owner, id;
	int error, pri, old_inherited_pri, su, rv;

	id = td->td_tid;
	uq = td->td_umtxq;
	if ((error = umtx_key_get(m, (flags & UMUTEX_ROBUST) != 0 ?
	    TYPE_PP_ROBUST_UMUTEX : TYPE_PP_UMUTEX, GET_SHARE(flags),
	    &uq->uq_key)) != 0)
		return (error);

	if (timeout != NULL)
		abs_timeout_init2(&timo, timeout);

	su = (priv_check(td, PRIV_SCHED_RTPRIO) == 0);
	for (;;) {
		old_inherited_pri = uq->uq_inherited_pri;
		umtxq_lock(&uq->uq_key);
		umtxq_busy(&uq->uq_key);
		umtxq_unlock(&uq->uq_key);

		rv = fueword32(&m->m_ceilings[0], &ceiling);
		if (rv == -1) {
			error = EFAULT;
			goto out;
		}
		ceiling = RTP_PRIO_MAX - ceiling;
		if (ceiling > RTP_PRIO_MAX) {
			error = EINVAL;
			goto out;
		}

		mtx_lock(&umtx_lock);
		if (UPRI(td) < PRI_MIN_REALTIME + ceiling) {
			mtx_unlock(&umtx_lock);
			error = EINVAL;
			goto out;
		}
		if (su && PRI_MIN_REALTIME + ceiling < uq->uq_inherited_pri) {
			uq->uq_inherited_pri = PRI_MIN_REALTIME + ceiling;
			thread_lock(td);
			if (uq->uq_inherited_pri < UPRI(td))
				sched_lend_user_prio(td, uq->uq_inherited_pri);
			thread_unlock(td);
		}
		mtx_unlock(&umtx_lock);

		rv = casueword32(&m->m_owner, UMUTEX_CONTESTED, &owner,
		    id | UMUTEX_CONTESTED);
		/* The address was invalid. */
		if (rv == -1) {