Patch that adds stack growth events to the trace viewer

stacktrace.diff

diff --git a/src/cmd/trace/trace.go b/src/cmd/trace/trace.go
index f39a397d0d..de8348e996 100644
--- a/src/cmd/trace/trace.go
+++ b/src/cmd/trace/trace.go
@@ -739,6 +739,8 @@ func generateTrace(params *traceParams, consumer traceConsumer) error {
 			ctx.emitInstant(ev, "task start", "user event")
 		case trace.EvUserTaskEnd:
 			ctx.emitInstant(ev, "task end", "user event")
+		case trace.EvGoCopyStack:
+			ctx.emitInstant(ev, "copystack", "")
 		}
 		// Emit any counter updates.
 		ctx.emitThreadCounters(ev)
diff --git a/src/internal/trace/parser.go b/src/internal/trace/parser.go
index c371ff3092..bf2ec56721 100644
--- a/src/internal/trace/parser.go
+++ b/src/internal/trace/parser.go
@@ -437,8 +437,11 @@ func parseEvents(ver int, rawEvents []rawEvent, strings map[uint64]string) (even
 				EvGoBlockSelect, EvGoBlockSync, EvGoBlockCond, EvGoBlockNet,
 				EvGoSysBlock, EvGoBlockGC:
 				lastG = 0
-			case EvGoSysExit, EvGoWaiting, EvGoInSyscall:
+			case EvGoSysExit, EvGoWaiting, EvGoInSyscall, EvGoCopyStack:
 				e.G = e.Args[0]
+				if raw.typ == EvGoCopyStack {
+					e.P = int(e.Args[1])
+				}
 			case EvUserTaskCreate:
 				// e.Args 0: taskID, 1:parentID, 2:nameID
 				e.SArgs = []string{strings[e.Args[2]]}
@@ -835,6 +838,11 @@ func postProcessTrace(ver int, events []*Event) error {
 			} else {
 				return fmt.Errorf("invalid user region mode: %q", ev)
 			}
+		case EvGoCopyStack:
+			if err := checkRunning(p, g, ev, true); err != nil {
+				return err
+			}
+			g.ev = ev
 		}
 
 		gs[ev.G] = g
@@ -1058,7 +1066,8 @@ const (
 	EvUserTaskEnd       = 46 // end of task [timestamp, internal task id, stack]
 	EvUserRegion        = 47 // trace.WithRegion [timestamp, internal task id, mode(0:start, 1:end), stack, name string]
 	EvUserLog           = 48 // trace.Log [timestamp, internal id, key string id, stack, value string]
-	EvCount             = 49
+	EvGoCopyStack       = 49 // copystack [timestamp, goroutine id]
+	EvCount             = 50
 )
 
 var EventDescriptions = [EvCount]struct {
@@ -1117,4 +1126,5 @@ var EventDescriptions = [EvCount]struct {
 	EvUserTaskEnd:       {"UserTaskEnd", 1011, true, []string{"taskid"}, nil},
 	EvUserRegion:        {"UserRegion", 1011, true, []string{"taskid", "mode", "typeid"}, []string{"name"}},
 	EvUserLog:           {"UserLog", 1011, true, []string{"id", "keyid"}, []string{"category", "message"}},
+	EvGoCopyStack:       {"GoCopyStack", 1011, true, []string{"g", "pid"}, nil},
 }
diff --git a/src/runtime/stack.go b/src/runtime/stack.go
index d5d09ba7d7..5e2fbc875c 100644
--- a/src/runtime/stack.go
+++ b/src/runtime/stack.go
@@ -1052,6 +1052,9 @@ func newstack() {
 		print("stack grow done\n")
 	}
 	casgstatus(gp, _Gcopystack, _Grunning)
+	if trace.enabled {
+		traceCopyStack(gp)
+	}
 	gogo(&gp.sched)
 }
 
diff --git a/src/runtime/trace.go b/src/runtime/trace.go
index 08e92d2efe..52aa3de378 100644
--- a/src/runtime/trace.go
+++ b/src/runtime/trace.go
@@ -68,7 +68,8 @@ const (
 	traceEvUserTaskEnd       = 46 // end of a task [timestamp, internal task id, stack]
 	traceEvUserRegion        = 47 // trace.WithRegion [timestamp, internal task id, mode(0:start, 1:end), stack, name string]
 	traceEvUserLog           = 48 // trace.Log [timestamp, internal task id, key string id, stack, value string]
-	traceEvCount             = 49
+	traceEvGoCopyStack       = 49 // copystack [timestamp, goroutine id]
+	traceEvCount             = 50
 	// Byte is used but only 6 bits are available for event type.
 	// The remaining 2 bits are used to specify the number of arguments.
 	// That means, the max event type value is 63.
@@ -609,6 +610,12 @@ func traceAcquireBuffer() (mp *m, pid int32, bufp *traceBufPtr) {
 	return mp, traceGlobProc, &trace.buf
 }
 
+func traceAcquireGlobal() (mp *m, pid int32, bufp *traceBufPtr) {
+	mp = acquirem()
+	lock(&trace.bufLock)
+	return mp, traceGlobProc, &trace.buf
+}
+
 // traceReleaseBuffer releases a buffer previously acquired with traceAcquireBuffer.
 func traceReleaseBuffer(pid int32) {
 	if pid == traceGlobProc {
@@ -1219,3 +1226,19 @@ func trace_userLog(id uint64, category, message string) {
 
 	traceReleaseBuffer(pid)
 }
+
+func traceCopyStack(gp *g) {
+	if !trace.enabled {
+		return
+	}
+	// we have to use the global proc buffer here
+	// in case we are copying the stack while emitting
+	// a trace event.
+	mp, pid, bufp := traceAcquireGlobal()
+	actualpid := pid
+	if p := mp.p.ptr(); p != nil {
+		actualpid = p.id
+	}
+	traceEventLocked(0, mp, pid, bufp, traceEvGoCopyStack, 1, uint64(gp.goid), uint64(actualpid))
+	traceReleaseBuffer(pid)
+}