Function knlist_cleardel

freebsd/kern/kern_event.c:2494–2548

* Even if we are locked, we may need to drop the lock to allow any influx * knotes time to "settle". */

 * knotes time to "settle".
 */
void
knlist_cleardel(struct knlist *knl, struct thread *td, int islocked, int killkn)
{
	struct knote *kn, *kn2;
	struct kqueue *kq;

	KASSERT(!knl->kl_autodestroy, ("cleardel for autodestroy %p", knl));
	if (islocked)
		KNL_ASSERT_LOCKED(knl);
	else {
		KNL_ASSERT_UNLOCKED(knl);
again:		/* need to reacquire lock since we have dropped it */
		knl->kl_lock(knl->kl_lockarg);
	}

	SLIST_FOREACH_SAFE(kn, &knl->kl_list, kn_selnext, kn2) {
		kq = kn->kn_kq;
		KQ_LOCK(kq);
		if (kn_in_flux(kn)) {
			KQ_UNLOCK(kq);
			continue;
		}
		knlist_remove_kq(knl, kn, 1, 1);
		if (killkn) {
			kn_enter_flux(kn);
			KQ_UNLOCK(kq);
			knote_drop_detached(kn, td);
		} else {
			/* Make sure cleared knotes disappear soon */
			kn->kn_flags |= EV_EOF | EV_ONESHOT;
			KQ_UNLOCK(kq);
		}
		kq = NULL;
	}

	if (!SLIST_EMPTY(&knl->kl_list)) {
		/* there are still in flux knotes remaining */
		kn = SLIST_FIRST(&knl->kl_list);
		kq = kn->kn_kq;
		KQ_LOCK(kq);
		KASSERT(kn_in_flux(kn), ("knote removed w/o list lock"));
		knl->kl_unlock(knl->kl_lockarg);
		kq->kq_state |= KQ_FLUXWAIT;
		msleep(kq, &kq->kq_lock, PSOCK | PDROP, "kqkclr", 0);
		kq = NULL;
		goto again;
	}

	if (islocked)
		KNL_ASSERT_LOCKED(knl);
	else {
		knl->kl_unlock(knl->kl_lockarg);
		KNL_ASSERT_UNLOCKED(knl);
	}
}

/*
 * Remove all knotes referencing a specified fd must be called with FILEDESC