From: Dmitriy Vyukov <dvyukov@google.com>
Date: Sun, 4 Aug 2013 19:31:23 +0000 (+0400)
Subject: net: fix concurrent Accept on windows
X-Git-Tag: go1.2rc2~798
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=77f21eea597f374e025497c167caccfd72864e13;p=gostls13.git

net: fix concurrent Accept on windows
Runtime netpoll supports at most one read waiter
and at most one write waiter. It's responsibility
of net package to ensure that. Currently windows
implementation allows more than one waiter in Accept.
It leads to "fatal error: netpollblock: double wait".

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/12400045
---

diff --git a/src/pkg/net/fd_windows.go b/src/pkg/net/fd_windows.go
index 5d584621a7..f51d1616e0 100644
--- a/src/pkg/net/fd_windows.go
+++ b/src/pkg/net/fd_windows.go
@@ -579,6 +579,8 @@ func (fd *netFD) accept(toAddr func(syscall.Sockaddr) Addr) (*netFD, error) {
 	}
 
 	// Submit accept request.
+	fd.rio.Lock()
+	defer fd.rio.Unlock()
 	var o acceptOp
 	o.Init(fd, 'r')
 	o.newsock = s
diff --git a/src/pkg/net/tcp_test.go b/src/pkg/net/tcp_test.go
index a71b02b477..f356f92f09 100644
--- a/src/pkg/net/tcp_test.go
+++ b/src/pkg/net/tcp_test.go
@@ -8,6 +8,7 @@ import (
 	"fmt"
 	"reflect"
 	"runtime"
+	"sync"
 	"testing"
 	"time"
 )
@@ -294,3 +295,35 @@ func TestIPv6LinkLocalUnicastTCP(t *testing.T) {
 		<-done
 	}
 }
+
+func TestTCPConcurrentAccept(t *testing.T) {
+	defer runtime.GOMAXPROCS(runtime.GOMAXPROCS(4))
+	ln, err := Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatalf("Listen failed: %v", err)
+	}
+	const N = 10
+	var wg sync.WaitGroup
+	wg.Add(N)
+	for i := 0; i < N; i++ {
+		go func() {
+			for {
+				c, err := ln.Accept()
+				if err != nil {
+					break
+				}
+				c.Close()
+			}
+			wg.Done()
+		}()
+	}
+	for i := 0; i < 10*N; i++ {
+		c, err := Dial("tcp", ln.Addr().String())
+		if err != nil {
+			t.Fatalf("Dial failed: %v", err)
+		}
+		c.Close()
+	}
+	ln.Close()
+	wg.Wait()
+}