From 07dbf8603aa1ac3c9a3762f5baee0ec45b29655c Mon Sep 17 00:00:00 2001
From: Yuriy Taraday <yorik.sar@gmail.com>
Date: Mon, 5 Feb 2018 01:28:14 +0400
Subject: [PATCH] Drain callback channel when try to deregister it

callback() is blocked on sending into channel otherwise.
---
 rpc.go | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/rpc.go b/rpc.go
index bea3317..6e019d0 100644
--- a/rpc.go
+++ b/rpc.go
@@ -191,10 +191,10 @@ func (l *Libvirt) listen() {
 func (l *Libvirt) callback(id uint32, res response) {
 	l.cm.Lock()
 	c, ok := l.callbacks[id]
-	l.cm.Unlock()
 	if ok {
 		c <- res
 	}
+	l.cm.Unlock()
 }
 
 // route sends incoming packets to their listeners.
@@ -281,7 +281,19 @@ func (l *Libvirt) register(id uint32, c chan response) {
 
 // deregister destroys a method response callback
 func (l *Libvirt) deregister(id uint32) {
-	l.cm.Lock()
+	lockChan := make(chan bool)
+	go func() {
+		l.cm.Lock()
+		lockChan <- true
+	}()
+Loop:
+	for {
+		select {
+		case _ = <-l.callbacks[id]:
+		case _ = <-lockChan:
+			break Loop
+		}
+	}
 	close(l.callbacks[id])
 	delete(l.callbacks, id)
 	l.cm.Unlock()