// Don't make other Acquire calls block on one that's doomed to fail.
		s.mu.Unlock()
		<-done
		return ctx.Err()
	}

	ready := make(chan struct{})
	w := waiter{n: n, ready: ready}
	elem := s.waiters.PushBack(w)
	s.mu.Unlock()

	select {
	case <-done:
		s.mu.Lock()
		select {
		case <-ready:
			// Acquired the semaphore after we were canceled.
			// Pretend we didn't and put the tokens back.
			s.cur -= n

	tail    []*wantConn
}

// len returns the number of items in the queue.
func (q *wantConnQueue) len() int {
	return len(q.head) - q.headPos + len(q.tail)
}

// pushBack adds w to the back of the queue.
func (q *wantConnQueue) pushBack(w *wantConn) {
	q.tail = append(q.tail, w)
}

// popFront removes and returns the wantConn at the front of the queue.
func (q *wantConnQueue) popFront() *wantConn {

	// lock.
	if atomic.Load(&gcBlackenEnabled) == 0 {
		unlock(&work.assistQueue.lock)
		return true
	}

	gp := getg()
	oldList := work.assistQueue.q
	work.assistQueue.q.pushBack(gp)

	// Recheck for background credit now that this G is in
	// the queue, but can still back out. This avoids a
	// race in case background marking has flushed more
	// credit since we checked above.

	}
	pInfo := obj.(*framework.QueuedPodInfo)
	pInfo.Attempts++
	p.schedulingCycle++
	// In flight, no concurrent events yet.
	if p.isSchedulingQueueHintEnabled {
		p.inFlightPods[pInfo.Pod.UID] = p.inFlightEvents.PushBack(pInfo.Pod)
	}

	// Update metrics and reset the set of unschedulable plugins for the next attempt.
	for plugin := range pInfo.UnschedulablePlugins.Union(pInfo.PendingPlugins) {

}

// push adds gp to the head of q.
func (q *gQueue) push(gp *g) {
	gp.schedlink = q.head
	q.head.set(gp)
	if q.tail == 0 {
		q.tail.set(gp)
	}
}

// pushBack adds gp to the tail of q.
func (q *gQueue) pushBack(gp *g) {
	gp.schedlink = 0
	if q.tail != 0 {
		q.tail.ptr().schedlink.set(gp)
	} else {
		q.head.set(gp)
	}
	q.tail.set(gp)
}

		return http2errClientDisconnected
	}
}

// writeFrame schedules a frame to write and sends it if there's nothing
// already being written.
//
// There is no pushback here (the serve goroutine never blocks). It's
// the http.Handlers that block, waiting for their previous frames to
// make it onto the wire
//
// If you're not on the serve goroutine, use writeFrameFromHandler instead.

		{"(*List).Len", Method, 0},
		{"(*List).MoveAfter", Method, 2},
		{"(*List).MoveBefore", Method, 2},
		{"(*List).MoveToBack", Method, 0},
		{"(*List).MoveToFront", Method, 0},
		{"(*List).PushBack", Method, 0},
		{"(*List).PushBackList", Method, 0},
		{"(*List).PushFront", Method, 0},
		{"(*List).PushFrontList", Method, 0},
		{"(*List).Remove", Method, 0},
		{"Element", Type, 0},

pkg container/list, method (*List) Len() int
pkg container/list, method (*List) MoveToBack(*Element)
pkg container/list, method (*List) MoveToFront(*Element)
pkg container/list, method (*List) PushBack(interface{}) *Element
pkg container/list, method (*List) PushBackList(*List)
pkg container/list, method (*List) PushFront(interface{}) *Element
pkg container/list, method (*List) PushFrontList(*List)