b0 := g.Batch(trace.ThreadID(0), 0)
	b0.Event("ProcStatus", trace.ProcID(1), go122.ProcIdle)
	b0.Event("ProcStatus", trace.ProcID(0), go122.ProcRunning)
	b0.Event("GoStatus", trace.GoID(1), trace.ThreadID(0), go122.GoRunning)
	b0.Event("GoSyscallBegin", testgen.Seq(1), testgen.NoStack)
	b0.Event("ProcStart", trace.ProcID(1), testgen.Seq(1))
	b0.Event("GoSyscallEndBlocked")

	b0.Event("ProcSteal", trace.ProcID(0), testgen.Seq(1), trace.ThreadID(1))

	// Status event for a goroutine blocked in a syscall for the entire generation.
	bz := g.Batch(trace.NoThread, 0)
	bz.Event("GoStatus", trace.GoID(1), trace.ThreadID(1), go122.GoSyscall)

	// A goroutine execute a syscall and steals its own P, then starts running
	// on that P.
	b0 := g.Batch(trace.ThreadID(0), 0)
	b0.Event("ProcStatus", trace.ProcID(0), go122.ProcRunning)
	b0.Event("GoStatus", trace.GoID(1), trace.ThreadID(0), go122.GoRunning)
	b0.Event("GoSyscallBegin", testgen.Seq(1), testgen.NoStack)
	b0.Event("ProcSteal", trace.ProcID(0), testgen.Seq(2), trace.ThreadID(0))
	b0.Event("ProcStart", trace.ProcID(0), testgen.Seq(3))

}

func gen(t *testgen.Trace) {
	g := t.Generation(1)

	// One goroutine is exiting with a syscall. It already
	// acquired a new P.
	b0 := g.Batch(trace.ThreadID(0), 0)
	b0.Event("GoStatus", trace.GoID(1), trace.ThreadID(0), go122.GoSyscall)
	b0.Event("ProcStatus", trace.ProcID(1), go122.ProcIdle)
	b0.Event("ProcStart", trace.ProcID(1), testgen.Seq(1))
	b0.Event("GoSyscallEndBlocked")

//
// See the documentation of Args for more details.
var ArgTypes = [...]string{
	"seq",     // sequence number
	"pstatus", // P status
	"gstatus", // G status
	"g",       // trace.GoID
	"m",       // trace.ThreadID
	"p",       // trace.ProcID
	"string",  // string ID
	"stack",   // stack ID
	"value",   // uint64
	"task",    // trace.TaskID
}

		}, nil
	case version.Go122, version.Go123:
		return &Reader{
			r: br,
			order: ordering{
				mStates:     make(map[ThreadID]*mState),
				pStates:     make(map[ProcID]*pState),
				gStates:     make(map[GoID]*gState),
				activeTasks: make(map[TaskID]taskState),
			},
			// Don't emit a sync event when we first go to emit events.
			emittedSync: true,
		}, nil
	default:

		w = w.writeProcStatus(uint64(pp.id), procStatus, pp.trace.inSweep)
	}
	if gp := tl.mp.curg; gp != nil && !gp.trace.statusWasTraced(tl.gen) && gp.trace.acquireStatus(tl.gen) {
		w = w.writeGoStatus(uint64(gp.goid), int64(tl.mp.procid), goStatus, gp.inMarkAssist, 0 /* no stack */)
	}
	return traceEventWriter{w}
}

// commit writes out a trace event and calls end. It's a helper to make the

	case "seq":
		u = uint64(arg.(Seq))
	case "pstatus":
		u = uint64(arg.(go122.ProcStatus))
	case "gstatus":
		u = uint64(arg.(go122.GoStatus))
	case "g":
		u = uint64(arg.(trace.GoID))
	case "m":
		u = uint64(arg.(trace.ThreadID))
	case "p":
		u = uint64(arg.(trace.ProcID))
	case "string":
		u = b.gen.String(arg.(string))
	case "task":
		u = uint64(arg.(trace.TaskID))
	default: