// Handle syscalls.
	if to == trace.GoSyscall {
		start := ev.Time()
		if from == trace.GoUndetermined {
			// Back-date the event to the start of the trace.
			start = ctx.startTime
		}
		// Write down that we've entered a syscall. Note: we might have no G or P here
		// if we're in a cgo callback or this is a transition from GoUndetermined
		// (i.e. the G has been blocked in a syscall).
		gs.syscallBegin(start, goID, ev.Stack())

	// Handle syscalls.
	if to == trace.GoSyscall {
		start := ev.Time()
		if from == trace.GoUndetermined {
			// Back-date the event to the start of the trace.
			start = ctx.startTime
		}
		// Write down that we've entered a syscall. Note: we might have no P here
		// if we're in a cgo callback or this is a transition from GoUndetermined
		// (i.e. the G has been blocked in a syscall).
		gs.syscallBegin(start, ev.Thread(), ev.Stack())

	if to == trace.GoSyscall && ev.Proc() != trace.NoProc {
		start := ev.Time()
		if from == trace.GoUndetermined {
			// Back-date the event to the start of the trace.
			start = ctx.startTime
		}
		// Write down that we've entered a syscall. Note: we might have no P here
		// if we're in a cgo callback or this is a transition from GoUndetermined
		// (i.e. the G has been blocked in a syscall).
		gs.syscallBegin(start, ev.Proc(), ev.Stack())

			File: f.File,
			Line: int(f.Line),
		})
		return true
	})
	return frames
}

func viewerGState(state trace.GoState, inMarkAssist bool) traceviewer.GState {
	switch state {
	case trace.GoUndetermined:
		return traceviewer.GDead
	case trace.GoNotExist:
		return traceviewer.GDead
	case trace.GoRunnable:
		return traceviewer.GRunnable
	case trace.GoRunning:
		return traceviewer.GRunning
	case trace.GoWaiting:

const NoGoroutine = GoID(-1)

// GoState represents the state of a goroutine.
//
// New GoStates may be added in the future. Users of this type must be robust
// to that possibility.
type GoState uint8

const (
	GoUndetermined GoState = iota // No information is known about the goroutine.
	GoNotExist                    // Goroutine does not exist.
	GoRunnable                    // Goroutine is runnable but not running.