}
		l.Update(advance(0))
		if l.NeedUpdate(advance(0)) {
			t.Fatal("need update even though just updated")
		}

		// Test transitioning the bucket to enable the GC.

		l.StartGCTransition(true, advance(109*time.Millisecond))
		l.FinishGCTransition(advance(2*time.Millisecond + 1*time.Microsecond))

		if expect := uint64((2*time.Millisecond + 1*time.Microsecond) * procs); l.Fill() != expect {

	return l.enabled.Load()
}

// startGCTransition notifies the limiter of a GC transition.
//
// This call takes ownership of the limiter and disables all other means of
// updating the limiter. Release ownership by calling finishGCTransition.
//
// It is safe to call concurrently with other operations.
func (l *gcCPULimiterState) startGCTransition(enableGC bool, now int64) {
	if !l.tryLock() {

	return l.limiter.limiting()
}

func (l *GCCPULimiter) NeedUpdate(now int64) bool {
	return l.limiter.needUpdate(now)
}

func (l *GCCPULimiter) StartGCTransition(enableGC bool, now int64) {
	l.limiter.startGCTransition(enableGC, now)
}

func (l *GCCPULimiter) FinishGCTransition(now int64) {
	l.limiter.finishGCTransition(now)
}

func (l *GCCPULimiter) Update(now int64) {

	// Assists and workers can start the moment we start
	// the world.
	gcController.startCycle(now, int(gomaxprocs), trigger)

	// Notify the CPU limiter that assists may begin.
	gcCPULimiter.startGCTransition(true, now)

	// In STW mode, disable scheduling of user Gs. This may also
	// disable scheduling of this goroutine, so it may block as
	// soon as we start the world again.
	if mode != gcBackgroundMode {