Function do_unlock_pi

freebsd/kern/kern_umtx.c:1996–2124

* Unlock a PI mutex. */

 * Unlock a PI mutex.
 */
static int
do_unlock_pi(struct thread *td, struct umutex *m, uint32_t flags, bool rb)
{
	struct umtx_key key;
	struct umtx_q *uq_first, *uq_first2, *uq_me;
	struct umtx_pi *pi, *pi2;
	uint32_t id, new_owner, old, owner;
	int count, error, pri;

	id = td->td_tid;

usrloop:
	/*
	 * Make sure we own this mtx.
	 */
	error = fueword32(&m->m_owner, &owner);
	if (error == -1)
		return (EFAULT);

	if ((owner & ~UMUTEX_CONTESTED) != id)
		return (EPERM);

	new_owner = umtx_unlock_val(flags, rb);

	/* This should be done in userland */
	if ((owner & UMUTEX_CONTESTED) == 0) {
		error = casueword32(&m->m_owner, owner, &old, new_owner);
		if (error == -1)
			return (EFAULT);
		if (error == 1) {
			error = thread_check_susp(td, true);
			if (error != 0)
				return (error);
			goto usrloop;
		}
		if (old == owner)
			return (0);
		owner = old;
	}

	/* We should only ever be in here for contested locks */
	if ((error = umtx_key_get(m, (flags & UMUTEX_ROBUST) != 0 ?
	    TYPE_PI_ROBUST_UMUTEX : TYPE_PI_UMUTEX, GET_SHARE(flags),
	    &key)) != 0)
		return (error);

	umtxq_lock(&key);
	umtxq_busy(&key);
	count = umtxq_count_pi(&key, &uq_first);
	if (uq_first != NULL) {
		mtx_lock(&umtx_lock);
		pi = uq_first->uq_pi_blocked;
		KASSERT(pi != NULL, ("pi == NULL?"));
		if (pi->pi_owner != td && !(rb && pi->pi_owner == NULL)) {
			mtx_unlock(&umtx_lock);
			umtxq_unbusy(&key);
			umtxq_unlock(&key);
			umtx_key_release(&key);