From e935d78bb7f92f3fcddfe14974ab93eb17d74d21 Mon Sep 17 00:00:00 2001
From: Alex Bramley <a.bramley@gmail.com>
Date: Mon, 2 Nov 2015 21:16:07 +0000
Subject: [PATCH] Fix for the deadlock condition.

---
 client/connection.go | 30 ++++++++++++++++++++++++++++--
 1 file changed, 28 insertions(+), 2 deletions(-)

diff --git a/client/connection.go b/client/connection.go
index e46b50d..9b4587e 100644
--- a/client/connection.go
+++ b/client/connection.go
@@ -176,8 +176,6 @@ func Client(cfg *Config) *Conn {
 	conn := &Conn{
 		cfg:         cfg,
 		dialer:      dialer,
-		in:          make(chan *Line, 32),
-		out:         make(chan string, 32),
 		intHandlers: handlerSet(),
 		fgHandlers:  handlerSet(),
 		bgHandlers:  handlerSet(),
@@ -265,6 +263,8 @@ func (conn *Conn) DisableStateTracking() {
 func (conn *Conn) initialise() {
 	conn.io = nil
 	conn.sock = nil
+	conn.in = make(chan *Line, 32)
+	conn.out = make(chan string, 32)
 	conn.die = make(chan struct{})
 	if conn.st != nil {
 		conn.st.Wipe()
@@ -510,6 +510,10 @@ func (conn *Conn) shutdown() {
 	conn.connected = false
 	conn.sock.Close()
 	close(conn.die)
+	// Drain both in and out channels to avoid a deadlock if the buffers
+	// have filled. See TestSendDeadlockOnFullBuffer in connection_test.go.
+	conn.drainIn()
+	conn.drainOut()
 	conn.wg.Wait()
 	conn.mu.Unlock()
 	// Dispatch after closing connection but before reinit
@@ -517,6 +521,28 @@ func (conn *Conn) shutdown() {
 	conn.dispatch(&Line{Cmd: DISCONNECTED, Time: time.Now()})
 }
 
+// drainIn sends all data buffered in conn.in to /dev/null.
+func (conn *Conn) drainIn() {
+	for {
+		select {
+		case <-conn.in:
+		default:
+			return
+		}
+	}
+}
+
+// drainOut does the same for conn.out. Generics!
+func (conn *Conn) drainOut() {
+	for {
+		select {
+		case <-conn.out:
+		default:
+			return
+		}
+	}
+}
+
 // Dumps a load of information about the current state of the connection to a
 // string for debugging state tracking and other such things.
 func (conn *Conn) String() string {