From 0fd544f256c212485402a9cf27506fc33a098eeb Mon Sep 17 00:00:00 2001
From: Daniel Kwasnick <dkwasnick@justin.tv>
Date: Tue, 10 Nov 2015 14:02:38 -0800
Subject: [PATCH] Fix cc.Close() state race
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Fix a race condition in which a Conn's state is set to TransientFailure after Close() has been invoked – Close() should irrevocably set state to Shutdown.
---
 clientconn.go | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/clientconn.go b/clientconn.go
index 4729bbd6abef..6da8867d6020 100644
--- a/clientconn.go
+++ b/clientconn.go
@@ -359,6 +359,7 @@ func (cc *Conn) resetTransport(closeTransport bool) error {
 		cc.mu.Lock()
 		cc.printf("connecting")
 		if cc.state == Shutdown {
+			// cc.Close() has been invoked.
 			cc.mu.Unlock()
 			return ErrClientConnClosing
 		}
@@ -393,6 +394,11 @@ func (cc *Conn) resetTransport(closeTransport bool) error {
 		newTransport, err := transport.NewClientTransport(cc.target, &copts)
 		if err != nil {
 			cc.mu.Lock()
+			if cc.state == Shutdown {
+				// cc.Close() has been invoked.
+				cc.mu.Unlock()
+				return ErrClientConnClosing
+			}
 			cc.errorf("transient failure: %v", err)
 			cc.state = TransientFailure
 			cc.stateCV.Broadcast()
@@ -450,6 +456,11 @@ func (cc *Conn) transportMonitor() {
 			return
 		case <-cc.transport.Error():
 			cc.mu.Lock()
+			if cc.state == Shutdown {
+				// cc.Close() has been invoked.
+				cc.mu.Unlock()
+				return
+			}
 			cc.state = TransientFailure
 			cc.stateCV.Broadcast()
 			cc.mu.Unlock()