@@ -213,15 +213,21 @@ func (r *bufReader) Close() error {

 }

 type writeBroadcaster struct {

+	mu      sync.Mutex

 	writers *list.List

 }

 func (w *writeBroadcaster) AddWriter(writer io.WriteCloser) {

+	w.mu.Lock()

 	w.writers.PushBack(writer)

+	w.mu.Unlock()

 }

 // FIXME: Is that function used?

+// FIXME: This relies on the concrete writer type used having equality operator

 func (w *writeBroadcaster) RemoveWriter(writer io.WriteCloser) {

+	w.mu.Lock()

+	defer w.mu.Unlock()

 	for e := w.writers.Front(); e != nil; e = e.Next() {

 		v := e.Value.(io.Writer)

 		if v == writer {

@@ -232,6 +238,8 @@ func (w *writeBroadcaster) RemoveWriter(writer io.WriteCloser) {

 }

 func (w *writeBroadcaster) Write(p []byte) (n int, err error) {

+	w.mu.Lock()

+	defer w.mu.Unlock()

 	failed := []*list.Element{}

 	for e := w.writers.Front(); e != nil; e = e.Next() {

 		writer := e.Value.(io.Writer)

@@ -249,6 +257,8 @@ func (w *writeBroadcaster) Write(p []byte) (n int, err error) {

 }

 func (w *writeBroadcaster) Close() error {

+	w.mu.Lock()

+	defer w.mu.Unlock()

 	for e := w.writers.Front(); e != nil; e = e.Next() {

 		writer := e.Value.(io.WriteCloser)

 		writer.Close()

@@ -258,5 +268,5 @@ func (w *writeBroadcaster) Close() error {

 }

 func newWriteBroadcaster() *writeBroadcaster {

-	return &writeBroadcaster{list.New()}

+	return &writeBroadcaster{writers: list.New()}

 }

@@ -124,3 +124,25 @@ func TestWriteBroadcaster(t *testing.T) {

 	writer.Close()

 }

+

+type devNullCloser int

+

+func (d devNullCloser) Close() error {

+	return nil

+}

+

+func (d devNullCloser) Write(buf []byte) (int, error) {

+	return len(buf), nil

+}

+

+// This test checks for races. It is only useful when run with the race detector.

+func TestRaceWriteBroadcaster(t *testing.T) {

+	writer := newWriteBroadcaster()

+	c := make(chan bool)

+	go func() {

+		writer.AddWriter(devNullCloser(0))

+		c <- true

+	}()

+	writer.Write([]byte("hello"))

+	<-c

+}