runtime: replace system goroutine whitelist with symbol test

Currently isSystemGoroutine has a hard-coded list of known entry
points into system goroutines. This list is annoying to maintain. For
example, it's missing the ensureSigM goroutine.

Replace it with a check that simply looks for any goroutine with
runtime function as its entry point, with a few exceptions. This also
matches the definition recently added to the trace viewer (CL 81315).

Change-Id: Iaed723d4a6e8c2ffb7c0c48fbac1688b00b30f01
Reviewed-on: https://go-review.googlesource.com/81655
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

src/cmd/internal/objabi/funcid.go

@@ -13,6 +13,7 @@ type FuncID uint32
 
 const (
 	FuncID_normal FuncID = iota // not a special function
+	FuncID_runtime_main
 	FuncID_goexit
 	FuncID_jmpdefer
 	FuncID_mcall
@@ -22,9 +23,6 @@ const (
 	FuncID_asmcgocall
 	FuncID_sigpanic
 	FuncID_runfinq
-	FuncID_bgsweep
-	FuncID_forcegchelper
-	FuncID_timerproc
 	FuncID_gcBgMarkWorker
 	FuncID_systemstack_switch
 	FuncID_systemstack

src/cmd/link/internal/ld/pcln.go

@@ -312,6 +312,8 @@ func (ctxt *Link) pclntab() {
 		// funcID uint32
 		funcID := objabi.FuncID_normal
 		switch s.Name {
+		case "runtime.main":
+			funcID = objabi.FuncID_runtime_main
 		case "runtime.goexit":
 			funcID = objabi.FuncID_goexit
 		case "runtime.jmpdefer":
@@ -330,12 +332,6 @@ func (ctxt *Link) pclntab() {
 			funcID = objabi.FuncID_sigpanic
 		case "runtime.runfinq":
 			funcID = objabi.FuncID_runfinq
-		case "runtime.bgsweep":
-			funcID = objabi.FuncID_bgsweep
-		case "runtime.forcegchelper":
-			funcID = objabi.FuncID_forcegchelper
-		case "runtime.timerproc":
-			funcID = objabi.FuncID_timerproc
 		case "runtime.gcBgMarkWorker":
 			funcID = objabi.FuncID_gcBgMarkWorker
 		case "runtime.systemstack_switch":

src/cmd/trace/trace.go

@@ -576,7 +576,7 @@ func generateTrace(params *traceParams, consumer traceConsumer) error {
 
 			fname := stk[0].Fn
 			info.name = fmt.Sprintf("G%v %s", newG, fname)
-			info.isSystemG = strings.HasPrefix(fname, "runtime.") && fname != "runtime.main"
+			info.isSystemG = isSystemGoroutine(fname)
 
 			ctx.gcount++
 			setGState(ev, newG, gDead, gRunnable)
@@ -1125,6 +1125,12 @@ func (ctx *traceContext) buildBranch(parent frameNode, stk []*trace.Frame) int {
 	return ctx.buildBranch(node, stk)
 }
 
+func isSystemGoroutine(entryFn string) bool {
+	// This mimics runtime.isSystemGoroutine as closely as
+	// possible.
+	return entryFn != "runtime.main" && strings.HasPrefix(entryFn, "runtime.")
+}
+
 // firstTimestamp returns the timestamp of the first event record.
 func firstTimestamp() int64 {
 	res, _ := parseTrace()

src/runtime/symtab.go

@@ -358,6 +358,7 @@ type funcID uint32
 
 const (
 	funcID_normal funcID = iota // not a special function
+	funcID_runtime_main
 	funcID_goexit
 	funcID_jmpdefer
 	funcID_mcall
@@ -367,9 +368,6 @@ const (
 	funcID_asmcgocall
 	funcID_sigpanic
 	funcID_runfinq
-	funcID_bgsweep
-	funcID_forcegchelper
-	funcID_timerproc
 	funcID_gcBgMarkWorker
 	funcID_systemstack_switch
 	funcID_systemstack

src/runtime/traceback.go

@@ -990,18 +990,25 @@ func topofstack(f funcInfo, g0 bool) bool {
 		(g0 && f.funcID == funcID_asmcgocall)
 }
 
-// isSystemGoroutine reports whether the goroutine g must be omitted in
+// isSystemGoroutine reports whether the goroutine g must be omitted
-// stack dumps and deadlock detector.
+// in stack dumps and deadlock detector. This is any goroutine that
+// starts at a runtime.* entry point, except for runtime.main and
+// sometimes runtime.runfinq.
 func isSystemGoroutine(gp *g) bool {
+	// Keep this in sync with cmd/trace/trace.go:isSystemGoroutine.
 	f := findfunc(gp.startpc)
 	if !f.valid() {
 		return false
 	}
-	return f.funcID == funcID_runfinq && !fingRunning ||
+	if f.funcID == funcID_runtime_main {
-		f.funcID == funcID_bgsweep ||
+		return false
-		f.funcID == funcID_forcegchelper ||
+	}
-		f.funcID == funcID_timerproc ||
+	if f.funcID == funcID_runfinq {
-		f.funcID == funcID_gcBgMarkWorker
+		// We include the finalizer goroutine if it's calling
+		// back into user code.
+		return !fingRunning
+	}
+	return hasprefix(funcname(f), "runtime.")
 }
 
 // SetCgoTraceback records three C functions to use to gather