// Undetermined case, so this is will simply not fire.
				if creatorG := s.gs[ev.Goroutine()]; creatorG != nil && len(creatorG.activeRegions) > 0 {
					regions := creatorG.activeRegions
					s := regions[len(regions)-1]
					g.activeRegions = []*UserRegionSummary{{TaskID: s.TaskID, Start: ev}}
				}
				s.gs[g.ID] = g
			case GoRunning:
				// Record execution time as we transition out of running

			tasks[ev.Args[0]] = ev

		case EvUserTaskEnd:
			taskid := ev.Args[0]
			delete(tasks, taskid)

		case EvUserRegion:
			mode := ev.Args[1]
			regions := activeRegions[ev.G]
			if mode == 0 { // region start
				activeRegions[ev.G] = append(regions, ev) // push
			} else if mode == 1 { // region end
				n := len(regions)
				if n > 0 { // matching region start event is in the trace.
					s := regions[n-1]