runtime: don't run TestCrashDumpsAllThreads in parallel

It sometimes seems to time out on slow systems, perhaps due to
being run at the same time as a lot of other work.

Also move the code to testdata/testprog, so that we don't have to
build it separately.

I hope that this
Fixes #35356

Change-Id: I875b858fa23836513ae14d3116461e22fffd5352
Reviewed-on: https://go-review.googlesource.com/c/go/+/312510
Trust: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Go Bot <gobot@golang.org>

src/runtime/crash_unix_test.go

@@ -13,7 +13,6 @@ import (
 	"io"
 	"os"
 	"os/exec"
-	"path/filepath"
 	"runtime"
 	"strings"
 	"sync"
@@ -78,27 +77,14 @@ func TestCrashDumpsAllThreads(t *testing.T) {
 		t.Skip("skipping; SIGQUIT is blocked, see golang.org/issue/19196")
 	}
 
-	// We don't use executeTest because we need to kill the
-	// program while it is running.
-
 	testenv.MustHaveGoBuild(t)
 
-	t.Parallel()
+	exe, err := buildTestProg(t, "testprog")
-
-	dir := t.TempDir()
-
-	if err := os.WriteFile(filepath.Join(dir, "main.go"), []byte(crashDumpsAllThreadsSource), 0666); err != nil {
-		t.Fatalf("failed to create Go file: %v", err)
-	}
-
-	cmd := exec.Command(testenv.GoToolPath(t), "build", "-o", "a.exe", "main.go")
-	cmd.Dir = dir
-	out, err := testenv.CleanCmdEnv(cmd).CombinedOutput()
 	if err != nil {
-		t.Fatalf("building source: %v\n%s", err, out)
+		t.Fatal(err)
 	}
 
-	cmd = exec.Command(filepath.Join(dir, "a.exe"))
+	cmd := exec.Command(exe, "CrashDumpsAllThreads")
 	cmd = testenv.CleanCmdEnv(cmd)
 	cmd.Env = append(cmd.Env,
 		"GOTRACEBACK=crash",
@@ -120,9 +106,12 @@ func TestCrashDumpsAllThreads(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
+	defer rp.Close()
+
 	cmd.ExtraFiles = []*os.File{wp}
 
 	if err := cmd.Start(); err != nil {
+		wp.Close()
 		t.Fatalf("starting program: %v", err)
 	}
 
@@ -144,56 +133,14 @@ func TestCrashDumpsAllThreads(t *testing.T) {
 	// We want to see a stack trace for each thread.
 	// Before https://golang.org/cl/2811 running threads would say
 	// "goroutine running on other thread; stack unavailable".
-	out = outbuf.Bytes()
+	out := outbuf.Bytes()
-	n := bytes.Count(out, []byte("main.loop("))
+	n := bytes.Count(out, []byte("main.crashDumpsAllThreadsLoop("))
 	if n != 4 {
 		t.Errorf("found %d instances of main.loop; expected 4", n)
 		t.Logf("%s", out)
 	}
 }
 
-const crashDumpsAllThreadsSource = `
-package main
-
-import (
-	"fmt"
-	"os"
-	"runtime"
-)
-
-func main() {
-	const count = 4
-	runtime.GOMAXPROCS(count + 1)
-
-	chans := make([]chan bool, count)
-	for i := range chans {
-		chans[i] = make(chan bool)
-		go loop(i, chans[i])
-	}
-
-	// Wait for all the goroutines to start executing.
-	for _, c := range chans {
-		<-c
-	}
-
-	// Tell our parent that all the goroutines are executing.
-	if _, err := os.NewFile(3, "pipe").WriteString("x"); err != nil {
-		fmt.Fprintf(os.Stderr, "write to pipe failed: %v\n", err)
-		os.Exit(2)
-	}
-
-	select {}
-}
-
-func loop(i int, c chan bool) {
-	close(c)
-	for {
-		for j := 0; j < 0x7fffffff; j++ {
-		}
-	}
-}
-`
-
 func TestPanicSystemstack(t *testing.T) {
 	// Test that GOTRACEBACK=crash prints both the system and user
 	// stack of other threads.

src/runtime/testdata/testprog/crashdump.go

@@ -0,0 +1,47 @@
+// Copyright 2021 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.
+
+package main
+
+import (
+	"fmt"
+	"os"
+	"runtime"
+)
+
+func init() {
+	register("CrashDumpsAllThreads", CrashDumpsAllThreads)
+}
+
+func CrashDumpsAllThreads() {
+	const count = 4
+	runtime.GOMAXPROCS(count + 1)
+
+	chans := make([]chan bool, count)
+	for i := range chans {
+		chans[i] = make(chan bool)
+		go crashDumpsAllThreadsLoop(i, chans[i])
+	}
+
+	// Wait for all the goroutines to start executing.
+	for _, c := range chans {
+		<-c
+	}
+
+	// Tell our parent that all the goroutines are executing.
+	if _, err := os.NewFile(3, "pipe").WriteString("x"); err != nil {
+		fmt.Fprintf(os.Stderr, "write to pipe failed: %v\n", err)
+		os.Exit(2)
+	}
+
+	select {}
+}
+
+func crashDumpsAllThreadsLoop(i int, c chan bool) {
+	close(c)
+	for {
+		for j := 0; j < 0x7fffffff; j++ {
+		}
+	}
+}