net: annotate Read/Write for race detector

Fixes #6167.

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/13052043

src/pkg/net/fd_windows.go

@@ -15,7 +15,10 @@ import (
 	"unsafe"
 )
 
-var initErr error
+var (
+	initErr error
+	ioSync  uint64
+)
 
 // CancelIo Windows API cancels all outstanding IO for a particular
 // socket on current thread. To overcome that limitation, we run
@@ -448,6 +451,9 @@ func (fd *netFD) Read(buf []byte) (int, error) {
 	if err == nil && n == 0 {
 		err = io.EOF
 	}
+	if raceenabled {
+		raceAcquire(unsafe.Pointer(&ioSync))
+	}
 	return n, err
 }
 
@@ -480,6 +486,9 @@ func (fd *netFD) Write(buf []byte) (int, error) {
 		return 0, err
 	}
 	defer fd.writeUnlock()
+	if raceenabled {
+		raceReleaseMerge(unsafe.Pointer(&ioSync))
+	}
 	o := &fd.wop
 	o.InitBuf(buf)
 	return iosrv.ExecIO(o, "WSASend", func(o *operation) error {

src/pkg/net/race.go

@@ -0,0 +1,31 @@
+// Copyright 2013 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 race
+// +build windows
+
+package net
+
+import (
+	"runtime"
+	"unsafe"
+)
+
+const raceenabled = true
+
+func raceAcquire(addr unsafe.Pointer) {
+	runtime.RaceAcquire(addr)
+}
+
+func raceReleaseMerge(addr unsafe.Pointer) {
+	runtime.RaceReleaseMerge(addr)
+}
+
+func raceReadRange(addr unsafe.Pointer, len int) {
+	runtime.RaceReadRange(addr, len)
+}
+
+func raceWriteRange(addr unsafe.Pointer, len int) {
+	runtime.RaceWriteRange(addr, len)
+}

src/pkg/net/race0.go

@@ -0,0 +1,26 @@
+// Copyright 2013 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 !race
+// +build windows
+
+package net
+
+import (
+	"unsafe"
+)
+
+const raceenabled = false
+
+func raceAcquire(addr unsafe.Pointer) {
+}
+
+func raceReleaseMerge(addr unsafe.Pointer) {
+}
+
+func raceReadRange(addr unsafe.Pointer, len int) {
+}
+
+func raceWriteRange(addr unsafe.Pointer, len int) {
+}