runtime: if the test program hangs, try to get a stack trace

This is an attempt to get more information for #14809, which seems to
occur rarely.

Updates #14809.

Change-Id: Idbeb136ceb57993644e03266622eb699d2685d02
Reviewed-on: https://go-review.googlesource.com/24110
Reviewed-by: Mikio Hara <mikioh.mikioh@gmail.com>
Reviewed-by: Austin Clements <austin@google.com>

src/runtime/crash_nonunix_test.go

@@ -0,0 +1,13 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build windows plan9 nacl
+
+package runtime_test
+
+import "os"
+
+// sigquit is the signal to send to kill a hanging testdata program.
+// On Unix we send SIGQUIT, but on non-Unix we only have os.Kill.
+var sigquit = os.Kill

src/runtime/crash_test.go

@@ -5,6 +5,7 @@
 package runtime_test
 
 import (
+	"bytes"
 	"fmt"
 	"internal/testenv"
 	"io/ioutil"
@@ -13,9 +14,11 @@ import (
 	"path/filepath"
 	"regexp"
 	"runtime"
+	"strconv"
 	"strings"
 	"sync"
 	"testing"
+	"time"
 )
 
 var toRemove []string
@@ -65,8 +68,45 @@ func runTestProg(t *testing.T, binary, name string) string {
 	if err != nil {
 		t.Fatal(err)
 	}
-	got, _ := testEnv(exec.Command(exe, name)).CombinedOutput()
-	return string(got)
+
+	cmd := testEnv(exec.Command(exe, name))
+	var b bytes.Buffer
+	cmd.Stdout = &b
+	cmd.Stderr = &b
+	if err := cmd.Start(); err != nil {
+		t.Fatalf("starting %s %s: %v", binary, name, err)
+	}
+
+	// If the process doesn't complete within 1 minute,
+	// assume it is hanging and kill it to get a stack trace.
+	p := cmd.Process
+	done := make(chan bool)
+	go func() {
+		scale := 1
+		// This GOARCH/GOOS test is copied from cmd/dist/test.go.
+		// TODO(iant): Have cmd/dist update the environment variable.
+		if runtime.GOARCH == "arm" || runtime.GOOS == "windows" {
+			scale = 2
+		}
+		if s := os.Getenv("GO_TEST_TIMEOUT_SCALE"); s != "" {
+			if sc, err := strconv.Atoi(s); err == nil {
+				scale = sc
+			}
+		}
+
+		select {
+		case <-done:
+		case <-time.After(time.Duration(scale) * time.Minute):
+			p.Signal(sigquit)
+		}
+	}()
+
+	if err := cmd.Wait(); err != nil {
+		t.Logf("%s %s exit status: %v", binary, name, err)
+	}
+	close(done)
+
+	return b.String()
 }
 
 func buildTestProg(t *testing.T, binary string, flags ...string) (string, error) {

src/runtime/crash_unix_test.go

@@ -19,6 +19,10 @@ import (
 	"testing"
 )
 
+// sigquit is the signal to send to kill a hanging testdata program.
+// Send SIGQUIT to get a stack trace.
+var sigquit = syscall.SIGQUIT
+
 func TestCrashDumpsAllThreads(t *testing.T) {
 	switch runtime.GOOS {
 	case "darwin", "dragonfly", "freebsd", "linux", "netbsd", "openbsd", "solaris":