addressed comments.

Author: doujiang24

src/runtime/crash_cgo_test.go

@@ -713,10 +713,7 @@ func TestCgoTracebackGoroutineProfile(t *testing.T) {
 
 func TestCgoTraceParser(t *testing.T) {
 	// Test issue 29707.
-	switch runtime.GOOS {
-	case "windows", "plan9":
-		t.Skipf("skipping cgo trace parser test on %s", runtime.GOOS)
-	}
+	testenv.MustHaveCGO(t)
 	output := runTestProg(t, "testprogcgo", "CgoTraceParser")
 	want := "OK\n"
 	if output != want {
@@ -726,10 +723,7 @@ func TestCgoTraceParser(t *testing.T) {
 
 func TestCgoTraceParserWithOneProc(t *testing.T) {
 	// Test issue 29707.
-	switch runtime.GOOS {
-	case "windows", "plan9":
-		t.Skipf("skipping cgo trace parser test on %s", runtime.GOOS)
-	}
+	testenv.MustHaveCGO(t)
 	output := runTestProg(t, "testprogcgo", "CgoTraceParser", "GOMAXPROCS=1")
 	want := "OK\n"
 	if output != want {

src/runtime/proc.go

@@ -1927,7 +1927,7 @@ func oneNewExtraM() {
 		gp.racectx = racegostart(abi.FuncPCABIInternal(newextram) + sys.PCQuantum)
 	}
 	if trace.enabled {
-		// trigger two trace events for the locked g in the extra m,
+		// Trigger two trace events for the locked g in the extra m,
 		// since the next event of the g will be traceEvGoSysExit in exitsyscall,
 		// while calling from C thread to Go.
 		traceGoCreate(gp, 0) // no start pc

src/runtime/testdata/testprogcgo/issue29707.go

@@ -2,8 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build !plan9 && !windows
-// +build !plan9,!windows
+//go:build unix
 
 // This is for issue #29707
 

src/runtime/trace.go

@@ -272,7 +272,7 @@ func StartTrace() error {
 			gp.traceseq++
 			traceEvent(traceEvGoInSyscall, -1, gp.goid)
 		} else if status == _Gdead && gp.m != nil && gp.m.isextra {
-			// trigger two trace events for the dead g in the extra m,
+			// Trigger two trace events for the dead g in the extra m,
 			// since the next event of the g will be traceEvGoSysExit in exitsyscall,
 			// while calling from C thread to Go.
 			gp.traceseq = 0