From f665ebac1602d581d8a45353d57d0e436539a213 Mon Sep 17 00:00:00 2001
From: Daniel Oaks <daniel@danieloaks.net>
Date: Tue, 18 Apr 2017 17:19:44 +1000
Subject: [PATCH] channels: Help prevent issues when join/parting

---
 irc/client.go | 2 ++
 irc/server.go | 9 +++++++++
 2 files changed, 11 insertions(+)

diff --git a/irc/client.go b/irc/client.go
index ca986273..1eb1fa11 100644
--- a/irc/client.go
+++ b/irc/client.go
@@ -483,9 +483,11 @@ func (client *Client) destroy() {
 	client.clearMonitorList()
 
 	// clean up channels
+	client.server.channelJoinPartMutex.Lock()
 	for channel := range client.channels {
 		channel.Quit(client, &friends)
 	}
+	client.server.channelJoinPartMutex.Unlock()
 
 	// clean up server
 	client.server.clients.Remove(client)
diff --git a/irc/server.go b/irc/server.go
index 0921433b..aa9440bc 100644
--- a/irc/server.go
+++ b/irc/server.go
@@ -86,6 +86,7 @@ type Server struct {
 	accounts                     map[string]*ClientAccount
 	channelRegistrationEnabled   bool
 	channels                     ChannelNameMap
+	channelJoinPartMutex         sync.Mutex // used when joining/parting channels to prevent stomping over each others' access and all
 	checkIdent                   bool
 	clients                      *ClientLookupSet
 	commands                     chan Command
@@ -802,6 +803,10 @@ func joinHandler(server *Server, client *Client, msg ircmsg.IrcMessage) bool {
 		keys = strings.Split(msg.Params[1], ",")
 	}
 
+	// get lock
+	server.channelJoinPartMutex.Lock()
+	defer server.channelJoinPartMutex.Unlock()
+
 	for i, name := range channels {
 		casefoldedName, err := CasefoldChannel(name)
 		if err != nil {
@@ -838,6 +843,10 @@ func partHandler(server *Server, client *Client, msg ircmsg.IrcMessage) bool {
 		reason = msg.Params[1]
 	}
 
+	// get lock
+	server.channelJoinPartMutex.Lock()
+	defer server.channelJoinPartMutex.Unlock()
+
 	for _, chname := range channels {
 		casefoldedChannelName, err := CasefoldChannel(chname)
 		channel := server.channels.Get(casefoldedChannelName)