for i := 0; i < N; i++ {
			runtime.Gosched()
			time.Sleep(time.Millisecond)
		}
		c <- true
		// runtime.UnlockOSThread() is deliberately omitted
	}()
	<-c
}

func TestGoroutineParallelism(t *testing.T) {
	if runtime.NumCPU() == 1 {
		// Takes too long, too easy to deadlock, etc.
		t.Skip("skipping on uniprocessor")
	}
	P := 4
	N := 10
	if testing.Short() {
		P = 3
		N = 3