/*
* Routine: wait_queue_link_internal
* Purpose:
* Insert a set wait queue into a wait queue. This
* requires us to link the two together using a wait_queue_link
* structure that was provided.
* Conditions:
* The wait queue being inserted must be inited as a set queue
* The wait_queue_link structure must already be properly typed
*/
static
kern_return_t
wait_queue_link_internal(
wait_queue_t wq,
wait_queue_set_t wq_set,
wait_queue_link_t wql)
{
wait_queue_element_t wq_element;
queue_t q;
spl_t s;
if (!wait_queue_is_valid(wq) || !wait_queue_is_set(wq_set))
return KERN_INVALID_ARGUMENT;
/*
* There are probably fewer threads and sets associated with
* the wait queue than there are wait queues associated with
* the set. So let's validate it that way.
*/
s = splsched();
wait_queue_lock(wq);
q = &wq->wq_queue;
wq_element = (wait_queue_element_t) queue_first(q);
while (!queue_end(q, (queue_entry_t)wq_element)) {
WAIT_QUEUE_ELEMENT_CHECK(wq, wq_element);
if ((wq_element->wqe_type == WAIT_QUEUE_LINK ||
wq_element->wqe_type == WAIT_QUEUE_LINK_NOALLOC) &&
((wait_queue_link_t)wq_element)->wql_setqueue == wq_set) {
wait_queue_unlock(wq);
splx(s);
return KERN_ALREADY_IN_SET;
}
wq_element = (wait_queue_element_t)
queue_next((queue_t) wq_element);
}
/*
* Not already a member, so we can add it.
*/
wqs_lock(wq_set);
WAIT_QUEUE_SET_CHECK(wq_set);
assert(wql->wql_type == WAIT_QUEUE_LINK ||
wql->wql_type == WAIT_QUEUE_LINK_NOALLOC);
wql->wql_queue = wq;
wql_clear_prepost(wql);
queue_enter(&wq->wq_queue, wql, wait_queue_link_t, wql_links);
wql->wql_setqueue = wq_set;
queue_enter(&wq_set->wqs_setlinks, wql, wait_queue_link_t, wql_setlinks);
wqs_unlock(wq_set);
wait_queue_unlock(wq);
splx(s);
return KERN_SUCCESS;
}
/*
* Routine: wait_queue_unlink_nofree
* Purpose:
* Undo the linkage between a wait queue and a set.
*/
static void
wait_queue_unlink_locked(
wait_queue_t wq,
wait_queue_set_t wq_set,
wait_queue_link_t wql)
{
assert(wait_queue_held(wq));
assert(wait_queue_held(&wq_set->wqs_wait_queue));
wql->wql_queue = WAIT_QUEUE_NULL;
queue_remove(&wq->wq_queue, wql, wait_queue_link_t, wql_links);
wql->wql_setqueue = WAIT_QUEUE_SET_NULL;
queue_remove(&wq_set->wqs_setlinks, wql, wait_queue_link_t, wql_setlinks);
wql->wql_type = WAIT_QUEUE_UNLINKED;
WAIT_QUEUE_CHECK(wq);
WAIT_QUEUE_SET_CHECK(wq_set);
}
kern_return_t
wait_queue_set_unlink_one(
wait_queue_set_t wq_set,
wait_queue_link_t wql)
{
wait_queue_t wq;
spl_t s;
assert(wait_queue_is_set(wq_set));
retry:
s = splsched();
wqs_lock(wq_set);
WAIT_QUEUE_SET_CHECK(wq_set);
/* Already unlinked, e.g. by selclearthread() */
if (wql->wql_type == WAIT_QUEUE_UNLINKED) {
goto out;
}
WAIT_QUEUE_SET_LINK_CHECK(wq_set, wql);
/* On a wait queue, and we hold set queue lock ... */
wq = wql->wql_queue;
if (wait_queue_lock_try(wq)) {
wait_queue_unlink_locked(wq, wq_set, wql);
wait_queue_unlock(wq);
} else {
wqs_unlock(wq_set);
splx(s);
delay(1);
goto retry;
}
out:
wqs_unlock(wq_set);
splx(s);
return KERN_SUCCESS;
}