From 7edd13355f1a407a95c7a084c201867501f48ec6 Mon Sep 17 00:00:00 2001
From: Roger Peppe <rogpeppe@gmail.com>
Date: Mon, 25 Feb 2013 16:22:00 +0000
Subject: [PATCH] net/rpc: avoid racy use of closing flag.

It's accessed without mutex protection
in a different goroutine from the one that
sets it.

Also make sure that Client.Call after Client.Close
will reliably return ErrShutdown, and that clients
see ErrShutdown rather than io.EOF when appropriate.

Suggestions welcome for a way to reliably test
the mutex issue.

R=r, iant
CC=golang-dev
https://golang.org/cl/7338045
---
 src/pkg/net/rpc/client.go      | 12 ++++++++----
 src/pkg/net/rpc/server_test.go | 17 +++++++++++++++++
 2 files changed, 25 insertions(+), 4 deletions(-)

diff --git a/src/pkg/net/rpc/client.go b/src/pkg/net/rpc/client.go
index ee3cc4d34d..4b0c9c3bba 100644
--- a/src/pkg/net/rpc/client.go
+++ b/src/pkg/net/rpc/client.go
@@ -71,7 +71,7 @@ func (client *Client) send(call *Call) {
 
 	// Register this call.
 	client.mutex.Lock()
-	if client.shutdown {
+	if client.shutdown || client.closing {
 		call.Error = ErrShutdown
 		client.mutex.Unlock()
 		call.done()
@@ -105,9 +105,6 @@ func (client *Client) input() {
 		response = Response{}
 		err = client.codec.ReadResponseHeader(&response)
 		if err != nil {
-			if err == io.EOF && !client.closing {
-				err = io.ErrUnexpectedEOF
-			}
 			break
 		}
 		seq := response.Seq
@@ -150,6 +147,13 @@ func (client *Client) input() {
 	client.mutex.Lock()
 	client.shutdown = true
 	closing := client.closing
+	if err == io.EOF {
+		if closing {
+			err = ErrShutdown
+		} else {
+			err = io.ErrUnexpectedEOF
+		}
+	}
 	for _, call := range client.pending {
 		call.Error = err
 		call.done()
diff --git a/src/pkg/net/rpc/server_test.go b/src/pkg/net/rpc/server_test.go
index db7778dcb2..8a15306235 100644
--- a/src/pkg/net/rpc/server_test.go
+++ b/src/pkg/net/rpc/server_test.go
@@ -524,6 +524,23 @@ func TestTCPClose(t *testing.T) {
 	}
 }
 
+func TestErrorAfterClientClose(t *testing.T) {
+	once.Do(startServer)
+
+	client, err := dialHTTP()
+	if err != nil {
+		t.Fatalf("dialing: %v", err)
+	}
+	err = client.Close()
+	if err != nil {
+		t.Fatal("close error:", err)
+	}
+	err = client.Call("Arith.Add", &Args{7, 9}, new(Reply))
+	if err != ErrShutdown {
+		t.Errorf("Forever: expected ErrShutdown got %v", err)
+	}
+}
+
 func benchmarkEndToEnd(dial func() (*Client, error), b *testing.B) {
 	b.StopTimer()
 	once.Do(startServer)