Mantis #624

Thank you, openlifegrid, for a patch to move new user connections to
thread pool threads.
Reworked by me to fit current trunk.
I believe that that patch may be beneficial in reducing the cases
in which regions become unresponsive and will no longer accept
new logins.

OpenSim/Region/ClientStack/LindenUDP/LLUDPServer.cs

@@ -30,6 +30,7 @@ using System.Collections;
 using System.Collections.Generic;
 using System.Net;
 using System.Net.Sockets;
+using System.Threading;
 using System.Reflection;
 using libsecondlife.Packets;
 using log4net;
@@ -69,6 +70,8 @@ namespace OpenSim.Region.ClientStack.LindenUDP
         protected AssetCache m_assetCache;
         protected AgentCircuitManager m_authenticateSessionsClass;
 
+        protected Queue<Packet> CreateUserPacket = new Queue<Packet>();
+
         public LLPacketServer PacketServer
         {
             get { return m_packetServer; }
@@ -236,7 +239,6 @@ namespace OpenSim.Region.ClientStack.LindenUDP
                     {
                         // new client
                         m_log.Debug("[UDPSERVER]: Adding New Client");
-                        AddNewClient(packet);
 
                         UseCircuitCodePacket p = (UseCircuitCodePacket)packet;
 
@@ -248,6 +250,14 @@ namespace OpenSim.Region.ClientStack.LindenUDP
                         ack_it.Packets[0].ID = packet.Header.Sequence;
                         ack_it.Header.Reliable = false;
                         SendPacketTo(ack_it.ToBytes(),ack_it.ToBytes().Length,SocketFlags.None,p.CircuitCode.Code);
+
+                        // toss it to a worker thread so IOthread can go home
+                        lock (CreateUserPacket)
+                        {
+                            CreateUserPacket.Enqueue(packet);
+                        }
+                        WaitCallback createUserCallback = new WaitCallback(AddNewClient);
+                        ThreadPool.QueueUserWorkItem(createUserCallback);
                     }
                 }
                 catch (Exception e)
@@ -311,6 +321,22 @@ namespace OpenSim.Region.ClientStack.LindenUDP
             }
         }
 
+        /// <summary>
+        /// target of workerthread delegate to create a new user. 
+        /// It assumes we get fired for each new user packet that comes in.
+        /// </summary>
+        /// <param name="o"></param>
+        protected void AddNewClient(object o)
+        {
+            Packet packet;
+            lock (CreateUserPacket)
+            {
+                packet = CreateUserPacket.Dequeue();
+            }
+            if (null != packet)
+                AddNewClient(packet);
+        }
+
         protected virtual void AddNewClient(Packet packet)
         {
             //Slave regions don't accept new clients