}
		if goids := r.FormValue("goid"); goids != "" {
			// Render trace focused on a particular goroutine.

			id, err := strconv.ParseUint(goids, 10, 64)
			if err != nil {
				log.Printf("failed to parse goid parameter %q: %v", goids, err)
				return
			}
			goid := trace.GoID(id)
			g, ok := parsed.summary.Goroutines[goid]
			if !ok {
				log.Printf("failed to find goroutine %d", goid)

	globalMetricGenerator
	stackSampleGenerator[trace.GoID]
	logEventGenerator[trace.GoID]

	gStates map[trace.GoID]*gState[trace.GoID]
	focus   trace.GoID
	filter  map[trace.GoID]struct{}
}

func newGoroutineGenerator(ctx *traceContext, focus trace.GoID, filter map[trace.GoID]struct{}) *goroutineGenerator {
	gg := new(goroutineGenerator)
	rg := func(ev *trace.Event) trace.GoID {
		return ev.Goroutine()
	}

// P in particular.
const NoProc = ProcID(-1)

// GoID is the runtime-internal G structure's goid field. This is unique
// for each goroutine.
type GoID int64

// NoGoroutine indicates that the relevant events don't correspond to any
// goroutine in particular.
const NoGoroutine = GoID(-1)

// GoState represents the state of a goroutine.
//

	b21.Event("GoStart", trace.GoID(1), testgen.Seq(2))

	// The goroutine starts running, then stops, then starts again.
	b20 := g2.Batch(trace.ThreadID(0), 5)
	b20.Event("ProcStatus", trace.ProcID(0), go122.ProcRunning)
	b20.Event("GoStatus", trace.GoID(1), trace.ThreadID(0), go122.GoRunnable)
	b20.Event("GoStart", trace.GoID(1), testgen.Seq(1))
	b20.Event("GoStop", "whatever", testgen.NoStack)

	b0.Event("GoCreateSyscall", trace.GoID(4))
	b0.Event("ProcStatus", trace.ProcID(0), go122.ProcIdle)
	b0.Event("ProcStart", trace.ProcID(0), testgen.Seq(1))
	b0.Event("GoSyscallEndBlocked")
	b0.Event("GoStart", trace.GoID(4), testgen.Seq(1))
	b0.Event("GoSyscallBegin", testgen.Seq(2), testgen.NoStack)
	b0.Event("GoDestroySyscall")
	b0.Event("GoCreateSyscall", trace.GoID(4))
	b0.Event("GoSyscallEnd")

}

func (g *procGenerator) GoroutineTransition(ctx *traceContext, ev *trace.Event) {
	st := ev.StateTransition()
	goID := st.Resource.Goroutine()

	// If we haven't seen this goroutine before, create a new
	// gState for it.
	gs, ok := g.gStates[goID]
	if !ok {
		gs = newGState[trace.ProcID](goID)
		g.gStates[goID] = gs
	}
	// If we haven't already named this goroutine, try to name it.
	gs.augmentName(st.Stack)

	b0.Event("ProcStatus", trace.ProcID(1), go122.ProcRunning)
	b0.Event("GoStatus", trace.GoID(1), trace.ThreadID(0), go122.GoSyscall)
	b0.Event("GoSyscallEndBlocked")

	// A running goroutine stole P0 at the generation boundary.
	b1 := g.Batch(trace.ThreadID(1), 0)
	b1.Event("ProcStatus", trace.ProcID(2), go122.ProcRunning)
	b1.Event("GoStatus", trace.GoID(2), trace.ThreadID(1), go122.GoRunning)

			g.threads[ev.Thread()] = struct{}{}
		}
	}

	st := ev.StateTransition()
	goID := st.Resource.Goroutine()

	// If we haven't seen this goroutine before, create a new
	// gState for it.
	gs, ok := g.gStates[goID]
	if !ok {
		gs = newGState[trace.ThreadID](goID)
		g.gStates[goID] = gs
	}
	// If we haven't already named this goroutine, try to name it.
	gs.augmentName(st.Stack)

// If an exit hook invokes exit in another goroutine, that exit will block.
func Run(code int) {
	for !locked.CompareAndSwap(0, 1) {
		if Goid() == runGoid.Load() {
			Throw("exit hook invoked exit")
		}
		Gosched()
	}
	defer locked.Store(0)
	runGoid.Store(Goid())
	defer runGoid.Store(0)

	defer func() {
		if e := recover(); e != nil {
			Throw("exit hook invoked panic")
		}
	}()

// writeGoStatus emits a GoStatus event as well as any active ranges on the goroutine.
func (w traceWriter) writeGoStatus(goid uint64, mid int64, status traceGoStatus, markAssist bool, stackID uint64) traceWriter {
	// The status should never be bad. Some invariant must have been violated.
	if status == traceGoBad {
		print("runtime: goid=", goid, "\n")
		throw("attempted to trace a bad status for a goroutine")
	}

	// Trace the status.