net: fix data race in benchmarks

Fixes #10307.

Change-Id: If70f36a6f1c4e465a47a0bc4d38b318424111106
Reviewed-on: https://go-review.googlesource.com/8330Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/net/dnsclient_unix_test.go

@@ -219,8 +219,7 @@ func TestReloadResolvConfChange(t *testing.T) {
 }
 
 func BenchmarkGoLookupIP(b *testing.B) {
-	uninstallTestHooks()
-	defer installTestHooks()
+	testHookUninstaller.Do(func() { uninstallTestHooks() })
 
 	for i := 0; i < b.N; i++ {
 		goLookupIP("www.example.com")
@@ -228,8 +227,7 @@ func BenchmarkGoLookupIP(b *testing.B) {
 }
 
 func BenchmarkGoLookupIPNoSuchHost(b *testing.B) {
-	uninstallTestHooks()
-	defer installTestHooks()
+	testHookUninstaller.Do(func() { uninstallTestHooks() })
 
 	for i := 0; i < b.N; i++ {
 		goLookupIP("some.nonexistent")
@@ -237,8 +235,7 @@ func BenchmarkGoLookupIPNoSuchHost(b *testing.B) {
 }
 
 func BenchmarkGoLookupIPWithBrokenNameServer(b *testing.B) {
-	uninstallTestHooks()
-	defer installTestHooks()
+	testHookUninstaller.Do(func() { uninstallTestHooks() })
 
 	onceLoadConfig.Do(loadDefaultConfig)
 	if cfg.dnserr != nil || cfg.dnsConfig == nil {

src/net/dnsname_test.go

@@ -69,8 +69,7 @@ func TestDNSNames(t *testing.T) {
 }
 
 func BenchmarkDNSNames(b *testing.B) {
-	uninstallTestHooks()
-	defer installTestHooks()
+	testHookUninstaller.Do(func() { uninstallTestHooks() })
 
 	benchmarks := append(tests, []testCase{
 		{strings.Repeat("a", 63), true},

src/net/interface_test.go

@@ -229,8 +229,7 @@ func testMulticastAddrs(t *testing.T, ifmat []Addr) (nmaf4, nmaf6 int) {
 }
 
 func BenchmarkInterfaces(b *testing.B) {
-	uninstallTestHooks()
-	defer installTestHooks()
+	testHookUninstaller.Do(func() { uninstallTestHooks() })
 
 	for i := 0; i < b.N; i++ {
 		if _, err := Interfaces(); err != nil {
@@ -240,8 +239,7 @@ func BenchmarkInterfaces(b *testing.B) {
 }
 
 func BenchmarkInterfaceByIndex(b *testing.B) {
-	uninstallTestHooks()
-	defer installTestHooks()
+	testHookUninstaller.Do(func() { uninstallTestHooks() })
 
 	ifi := loopbackInterface()
 	if ifi == nil {
@@ -255,8 +253,7 @@ func BenchmarkInterfaceByIndex(b *testing.B) {
 }
 
 func BenchmarkInterfaceByName(b *testing.B) {
-	uninstallTestHooks()
-	defer installTestHooks()
+	testHookUninstaller.Do(func() { uninstallTestHooks() })
 
 	ifi := loopbackInterface()
 	if ifi == nil {
@@ -270,8 +267,7 @@ func BenchmarkInterfaceByName(b *testing.B) {
 }
 
 func BenchmarkInterfaceAddrs(b *testing.B) {
-	uninstallTestHooks()
-	defer installTestHooks()
+	testHookUninstaller.Do(func() { uninstallTestHooks() })
 
 	for i := 0; i < b.N; i++ {
 		if _, err := InterfaceAddrs(); err != nil {
@@ -281,8 +277,7 @@ func BenchmarkInterfaceAddrs(b *testing.B) {
 }
 
 func BenchmarkInterfacesAndAddrs(b *testing.B) {
-	uninstallTestHooks()
-	defer installTestHooks()
+	testHookUninstaller.Do(func() { uninstallTestHooks() })
 
 	ifi := loopbackInterface()
 	if ifi == nil {
@@ -296,8 +291,7 @@ func BenchmarkInterfacesAndAddrs(b *testing.B) {
 }
 
 func BenchmarkInterfacesAndMulticastAddrs(b *testing.B) {
-	uninstallTestHooks()
-	defer installTestHooks()
+	testHookUninstaller.Do(func() { uninstallTestHooks() })
 
 	ifi := loopbackInterface()
 	if ifi == nil {

src/net/ip_test.go

@@ -53,8 +53,7 @@ func TestParseIP(t *testing.T) {
 }
 
 func BenchmarkParseIP(b *testing.B) {
-	uninstallTestHooks()
-	defer installTestHooks()
+	testHookUninstaller.Do(func() { uninstallTestHooks() })
 
 	for i := 0; i < b.N; i++ {
 		for _, tt := range parseIPTests {
@@ -111,8 +110,7 @@ func TestIPString(t *testing.T) {
 }
 
 func BenchmarkIPString(b *testing.B) {
-	uninstallTestHooks()
-	defer installTestHooks()
+	testHookUninstaller.Do(func() { uninstallTestHooks() })
 
 	for i := 0; i < b.N; i++ {
 		for _, tt := range ipStringTests {
@@ -164,8 +162,7 @@ func TestIPMaskString(t *testing.T) {
 }
 
 func BenchmarkIPMaskString(b *testing.B) {
-	uninstallTestHooks()
-	defer installTestHooks()
+	testHookUninstaller.Do(func() { uninstallTestHooks() })
 
 	for i := 0; i < b.N; i++ {
 		for _, tt := range ipMaskStringTests {

src/net/main_test.go

@@ -11,23 +11,29 @@ import (
 	"runtime"
 	"sort"
 	"strings"
+	"sync"
 	"testing"
 )
 
-var sw socktest.Switch
+var (
+	sw socktest.Switch
+
+	// uninstallTestHooks runs just before a run of benchmarks.
+	testHookUninstaller sync.Once
+)
 
 func TestMain(m *testing.M) {
 	installTestHooks()
 
 	st := m.Run()
 
+	testHookUninstaller.Do(func() { uninstallTestHooks() })
 	if !testing.Short() {
 		printLeakedGoroutines()
 		printLeakedSockets()
 		printSocketStats()
 	}
 	forceCloseSockets()
-	uninstallTestHooks()
 	os.Exit(st)
 }
 

src/net/tcp_test.go

@@ -59,8 +59,7 @@ func BenchmarkTCP6PersistentTimeout(b *testing.B) {
 }
 
 func benchmarkTCP(b *testing.B, persistent, timeout bool, laddr string) {
-	uninstallTestHooks()
-	defer installTestHooks()
+	testHookUninstaller.Do(func() { uninstallTestHooks() })
 
 	const msgLen = 512
 	conns := b.N
@@ -170,13 +169,13 @@ func BenchmarkTCP6ConcurrentReadWrite(b *testing.B) {
 }
 
 func benchmarkTCPConcurrentReadWrite(b *testing.B, laddr string) {
+	testHookUninstaller.Do(func() { uninstallTestHooks() })
+
 	// The benchmark creates GOMAXPROCS client/server pairs.
 	// Each pair creates 4 goroutines: client reader/writer and server reader/writer.
 	// The benchmark stresses concurrent reading and writing to the same connection.
 	// Such pattern is used in net/http and net/rpc.
 
-	uninstallTestHooks()
-	defer installTestHooks()
 	b.StopTimer()
 
 	P := runtime.GOMAXPROCS(0)