wg.Add(1)
	go func() {
		defer wg.Done()
		start := time.Now()
		growStack(nil)
		growDuration = time.Since(start)
	}()
	wg.Wait()
	t.Log("first growStack took", growDuration)

	// in locked goroutine
	wg.Add(1)
	go func() {
		defer wg.Done()
		LockOSThread()
		growStack(nil)
		UnlockOSThread()
	}()
	wg.Wait()

	// in finalizer
	var finalizerStart time.Time

//export issue7978cb
func issue7978cb() {
	// Force a stack growth from the callback to put extra
	// pressure on the runtime. See issue #17785.
	growStack(64)
	issue7978wait(3, 4)
}

func growStack(n int) int {
	var buf [128]int
	if n == 0 {
		return 0
	}
	return buf[growStack(n-1)]
}

func issue7978go() {
	C.issue7978c((*C.uint32_t)(&issue7978sync))
	issue7978wait(7, 8)
}

		Time:  viewerTime(a.Start),
		Stack: a.FromStack,
	})
	e.OptionalEvent(&format.Event{
		Name:  a.Name,
		Phase: "t",
		TID:   a.ToResource,
		PID:   sectionID,
		ID:    e.arrowSeq,
		Time:  viewerTime(a.End),
	})
}

type ArrowEvent struct {
	Name         string
	Start        time.Duration
	End          time.Duration
	FromResource uint64
	FromStack    int
	ToResource   uint64
}

			Name:         gs.startCause.name,
			Start:        ctx.elapsed(gs.startCause.time),
			End:          ctx.elapsed(ts),
			FromResource: uint64(gs.startCause.resource),
			ToResource:   uint64(resource),
			FromStack:    ctx.Stack(viewerFrames(gs.startCause.stack)),
		})
		gs.startCause.time = 0
		gs.startCause.name = ""
		gs.startCause.resource = 0
		gs.startCause.stack = trace.NoStack
	}
	gs.executing = resource

			Name:         "newTask",
			Start:        ctx.elapsed(task.Start.Time()),
			End:          ctx.elapsed(task.Start.Time()),
			FromResource: uint64(task.Parent.ID),
			ToResource:   uint64(task.ID),
			FromStack:    ctx.Stack(viewerFrames(task.Start.Stack())),
		})
	}
}

// emitRegion emits goroutine-based slice events to the UI. The caller
// must be emitting for a goroutine-oriented trace.
//

	lockedInt     uint32      // tracking for internal lockOSThread
	nextwaitm     muintptr    // next m waiting for lock

	mLockProfile mLockProfile // fields relating to runtime.lock contention
	profStack    []uintptr    // used for memory/block/mutex stack traces

	// wait* are used to carry arguments from gopark into park_m, because
	// there's no stack to put them on. That is their sole purpose.