// Ms that may be preparing to drop their P.
		sched.needspinning.Store(1)
		return nil, now
	}

	return pp, now
}

// runqempty reports whether pp has no Gs on its local run queue.
// It never returns true spuriously.
func runqempty(pp *p) bool {
	// Defend against a race where 1) pp has G1 in runqnext but runqhead == runqtail,

	for i := 0; i < iters; i++ {
		*ready = 0
		next0 := (i & 1) == 0
		next1 := (i & 2) == 0
		runqput(p, &gs[0], next0)
		go func() {
			for atomic.Xadd(ready, 1); atomic.Load(ready) != 2; {
			}
			if runqempty(p) {
				println("next:", next0, next1)
				throw("queue is empty")
			}
			done <- true
		}()
		for atomic.Xadd(ready, 1); atomic.Load(ready) != 2; {
		}
		runqput(p, &gs[1], next1)
		runqget(p)