net/internal/socktest: fix data race

Fixes #10796.

Change-Id: Ifcd2e771c64114e210fbfc5efaaceb53c534f745
Reviewed-on: https://go-review.googlesource.com/10007
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/net/internal/socktest/main_test.go

@@ -9,6 +9,7 @@ package socktest_test
 import (
 	"net/internal/socktest"
 	"os"
+	"sync"
 	"syscall"
 	"testing"
 )
@@ -27,6 +28,21 @@ func TestMain(m *testing.M) {
 	os.Exit(st)
 }
 
+func TestSwitch(t *testing.T) {
+	const N = 10
+	var wg sync.WaitGroup
+	wg.Add(N)
+	for i := 0; i < N; i++ {
+		go func() {
+			defer wg.Done()
+			for _, family := range []int{syscall.AF_INET, syscall.AF_INET6} {
+				socketFunc(family, syscall.SOCK_STREAM, syscall.IPPROTO_TCP)
+			}
+		}()
+	}
+	wg.Wait()
+}
+
 func TestSocket(t *testing.T) {
 	for _, f := range []socktest.Filter{
 		func(st *socktest.Status) (socktest.AfterFilter, error) { return nil, nil },

src/net/internal/socktest/switch.go

@@ -10,12 +10,6 @@ import (
 	"sync"
 )
 
-func switchInit(sw *Switch) {
-	sw.fltab = make(map[FilterType]Filter)
-	sw.sotab = make(Sockets)
-	sw.stats = make(stats)
-}
-
 // A Switch represents a callpath point switch for socket system
 // calls.
 type Switch struct {
@@ -29,6 +23,12 @@ type Switch struct {
 	stats stats
 }
 
+func (sw *Switch) init() {
+	sw.fltab = make(map[FilterType]Filter)
+	sw.sotab = make(Sockets)
+	sw.stats = make(stats)
+}
+
 // Stats returns a list of per-cookie socket statistics.
 func (sw *Switch) Stats() []Stat {
 	var st []Stat
@@ -162,7 +162,7 @@ func (f AfterFilter) apply(st *Status) error {
 
 // Set deploys the socket system call filter f for the filter type t.
 func (sw *Switch) Set(t FilterType, f Filter) {
-	sw.once.Do(func() { switchInit(sw) })
+	sw.once.Do(sw.init)
 	sw.fmu.Lock()
 	sw.fltab[t] = f
 	sw.fmu.Unlock()

src/net/internal/socktest/switch_unix.go

@@ -22,7 +22,7 @@ func (sw *Switch) sockso(s int) *Status {
 // addLocked returns a new Status without locking.
 // sw.smu must be held before call.
 func (sw *Switch) addLocked(s, family, sotype, proto int) *Status {
-	sw.once.Do(func() { switchInit(sw) })
+	sw.once.Do(sw.init)
 	so := Status{Cookie: cookie(family, sotype, proto)}
 	sw.sotab[s] = so
 	return &so

src/net/internal/socktest/switch_windows.go

@@ -22,7 +22,7 @@ func (sw *Switch) sockso(s syscall.Handle) *Status {
 // addLocked returns a new Status without locking.
 // sw.smu must be held before call.
 func (sw *Switch) addLocked(s syscall.Handle, family, sotype, proto int) *Status {
-	sw.once.Do(func() { switchInit(sw) })
+	sw.once.Do(sw.init)
 	so := Status{Cookie: cookie(family, sotype, proto)}
 	sw.sotab[s] = so
 	return &so

src/net/internal/socktest/sys_unix.go

@@ -10,6 +10,8 @@ import "syscall"
 
 // Socket wraps syscall.Socket.
 func (sw *Switch) Socket(family, sotype, proto int) (s int, err error) {
+	sw.once.Do(sw.init)
+
 	so := &Status{Cookie: cookie(family, sotype, proto)}
 	sw.fmu.RLock()
 	f, _ := sw.fltab[FilterSocket]

src/net/internal/socktest/sys_windows.go

@@ -8,6 +8,8 @@ import "syscall"
 
 // Socket wraps syscall.Socket.
 func (sw *Switch) Socket(family, sotype, proto int) (s syscall.Handle, err error) {
+	sw.once.Do(sw.init)
+
 	so := &Status{Cookie: cookie(family, sotype, proto)}
 	sw.fmu.RLock()
 	f, _ := sw.fltab[FilterSocket]