runtime: Goexit on C-created thread report more useful error message

Fixes #68275

Change-Id: I47b7a2092f1b4d48aebf437db4e329815c956bb9
GitHub-Last-Rev: b89bf3cab7
GitHub-Pull-Request: golang/go#69126
Reviewed-on: https://go-review.googlesource.com/c/go/+/609296
Reviewed-by: Tim King <taking@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>

src/runtime/panic.go

@@ -614,6 +614,8 @@ func deferreturn() {
 // without func main returning. Since func main has not returned,
 // the program continues execution of other goroutines.
 // If all other goroutines exit, the program crashes.
+//
+// It crashes if called from a thread not created by the Go runtime.
 func Goexit() {
 	// Create a panic object for Goexit, so we can recognize when it might be
 	// bypassed by a recover().

src/runtime/proc.go

@@ -4321,6 +4321,9 @@ func gdestroy(gp *g) {
 
 	if locked && mp.lockedInt != 0 {
 		print("runtime: mp.lockedInt = ", mp.lockedInt, "\n")
+		if mp.isextra {
+			throw("runtime.Goexit called in a thread that was not created by the Go runtime")
+		}
 		throw("exited a goroutine internally locked to the OS thread")
 	}
 	gfput(pp, gp)

src/runtime/proc_test.go

@@ -1158,3 +1158,13 @@ func TestBigGOMAXPROCS(t *testing.T) {
 		t.Errorf("output:\n%s\nwanted:\nunknown function: NonexistentTest", output)
 	}
 }
+
+func TestCgoToGoCallGoexit(t *testing.T) {
+	if runtime.GOOS == "plan9" || runtime.GOOS == "windows" {
+		t.Skipf("no pthreads on %s", runtime.GOOS)
+	}
+	output := runTestProg(t, "testprogcgo", "CgoToGoCallGoexit")
+	if !strings.Contains(output, "runtime.Goexit called in a thread that was not created by the Go runtime") {
+		t.Fatalf("output should contain %s, got %s", "runtime.Goexit called in a thread that was not created by the Go runtime", output)
+	}
+}

src/runtime/testdata/testprogcgo/callback.go

@@ -38,10 +38,21 @@ import (
 
 func init() {
 	register("CgoCallbackGC", CgoCallbackGC)
+	register("CgoToGoCallGoexit", CgoToGoCallGoexit)
 }
 
+func CgoToGoCallGoexit() {
+	goexit = true
+	C.foo()
+}
+
+var goexit = false
+
 //export go_callback
 func go_callback() {
+	if goexit {
+		runtime.Goexit()
+	}
 	if e := extraMInUse.Load(); e == 0 {
 		fmt.Printf("in callback extraMInUse got %d want >0\n", e)
 		os.Exit(1)