runtime: add memory barrier for sync send in select

Missed select case when adding the barrier last time.
All the more reason to refactor this code in Go 1.6.

Fixes #11643.

Change-Id: Ib0d19d6e0939296c0a3e06dda5e9b76f813bbc7e
Reviewed-on: https://go-review.googlesource.com/12086
Reviewed-by: Austin Clements <austin@google.com>

1 files changed, 80 insertions, 0 deletions

diff --git a/src/runtime/chanbarrier_test.go b/src/runtime/chanbarrier_test.go
new file mode 100644
index 0000000000..c48fd3c965
--- /dev/null
+++ b/src/runtime/chanbarrier_test.go
@@ -0,0 +1,80 @@
+// Copyright 2015 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.
+
+package runtime_test
+
+import (
+	"runtime"
+	"sync"
+	"testing"
+)
+
+type response struct {
+}
+
+type myError struct {
+}
+
+func (myError) Error() string { return "" }
+
+func doRequest(useSelect bool) (*response, error) {
+	type async struct {
+		resp *response
+		err  error
+	}
+	ch := make(chan *async, 0)
+	done := make(chan struct{}, 0)
+
+	if useSelect {
+		go func() {
+			select {
+			case ch <- &async{resp: nil, err: myError{}}:
+			case <-done:
+			}
+		}()
+	} else {
+		go func() {
+			ch <- &async{resp: nil, err: myError{}}
+		}()
+	}
+
+	r := <-ch
+	runtime.Gosched()
+	return r.resp, r.err
+}
+
+func TestChanSendSelectBarrier(t *testing.T) {
+	testChanSendBarrier(true)
+}
+
+func TestChanSendBarrier(t *testing.T) {
+	testChanSendBarrier(false)
+}
+
+func testChanSendBarrier(useSelect bool) {
+	var wg sync.WaitGroup
+	outer := 100
+	inner := 100000
+	if testing.Short() {
+		outer = 10
+		inner = 1000
+	}
+	for i := 0; i < outer; i++ {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			var garbage []byte
+			for j := 0; j < inner; j++ {
+				_, err := doRequest(useSelect)
+				_, ok := err.(myError)
+				if !ok {
+					panic(1)
+				}
+				garbage = make([]byte, 1<<10)
+			}
+			global = garbage
+		}()
+	}
+	wg.Wait()
+}