runtime: fix select pass 3

Fixes issue 2075

R=rsc, ken, r
CC=golang-dev
http://codereview.appspot.com/4748045

Committer: Russ Cox <rsc@golang.org>

1 files changed, 34 insertions, 0 deletions

diff --git a/test/chan/select6.go b/test/chan/select6.go
new file mode 100644
index 000000000..2ba6810ac
--- /dev/null
+++ b/test/chan/select6.go
@@ -0,0 +1,34 @@
+// $G $D/$F.go && $L $F.$A && ./$A.out
+
+// Copyright 2011 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.
+
+// Issue 2075
+// A bug in select corrupts channel queues of failed cases
+// if there are multiple waiters on those channels and the
+// select is the last in the queue. If further waits are made
+// on the channel without draining it first then those waiters
+// will never wake up. In the code below c1 is such a channel.
+
+package main
+
+func main() {
+	c1 := make(chan bool)
+	c2 := make(chan bool)
+	c3 := make(chan bool)
+	go func() { <-c1 }()
+	go func() {
+		select {
+		case <-c1:
+			panic("dummy")
+		case <-c2:
+			c3 <- true
+		}
+		<-c1
+	}()
+	go func() { c2 <- true }()
+	<-c3
+	c1 <- true
+	c1 <- true
+}