Add comments about trying to avoid synchronous work off the EventManager.OnMakeRootAgent event since this is on the critical path for transfer of avatars from one region to another.

OpenSim/Region/CoreModules/Avatar/Friends/FriendsModule.cs

@@ -29,6 +29,7 @@ using System;
 using System.Collections;
 using System.Collections.Generic;
 using System.Reflection;
+using System.Threading;
 using log4net;
 using Nini.Config;
 using Nwc.XmlRpc;
@@ -856,7 +857,7 @@ namespace OpenSim.Region.CoreModules.Avatar.Friends
             IClientAPI friendClient = LocateClientObject(friendID);
             if (friendClient != null)
             {
-                // the  friend in this sim as root agent
+                // the friend in this sim as root agent
                 if (online)
                     friendClient.SendAgentOnline(new UUID[] { userID });
                 else
@@ -913,6 +914,8 @@ namespace OpenSim.Region.CoreModules.Avatar.Friends
 
         private void RecacheFriends(IClientAPI client)
         {
+            // FIXME: Ideally, we want to avoid doing this here since it sits the EventManager.OnMakeRootAgent event
+            // is on the critical path for transferring an avatar from one region to another.
             UUID agentID = client.AgentId;
             lock (m_Friends)
             {

OpenSim/Region/Framework/Scenes/EventManager.cs

@@ -212,10 +212,15 @@ namespace OpenSim.Region.Framework.Scenes
         public delegate void OnMakeChildAgentDelegate(ScenePresence presence);
         public event OnMakeChildAgentDelegate OnMakeChildAgent;
 
-        public delegate void OnMakeRootAgentDelegate(ScenePresence presence);
         public delegate void OnSaveNewWindlightProfileDelegate();
         public delegate void OnSendNewWindlightProfileTargetedDelegate(RegionLightShareData wl, UUID user);
-        public event OnMakeRootAgentDelegate OnMakeRootAgent;
+
+        /// <summary>
+        /// This event is on the critical path for transferring an avatar from one region to another.  Try and do
+        /// as little work on this event as possible, or do work asynchronously.
+        /// </summary>
+        public event Action<ScenePresence> OnMakeRootAgent;
+        
         public event OnSendNewWindlightProfileTargetedDelegate OnSendNewWindlightProfileTargeted;
         public event OnSaveNewWindlightProfileDelegate OnSaveNewWindlightProfile;
 
@@ -1322,10 +1327,10 @@ namespace OpenSim.Region.Framework.Scenes
 
         public void TriggerOnMakeRootAgent(ScenePresence presence)
         {
-            OnMakeRootAgentDelegate handlerMakeRootAgent = OnMakeRootAgent;
+            Action<ScenePresence> handlerMakeRootAgent = OnMakeRootAgent;
             if (handlerMakeRootAgent != null)
             {
-                foreach (OnMakeRootAgentDelegate d in handlerMakeRootAgent.GetInvocationList())
+                foreach (Action<ScenePresence> d in handlerMakeRootAgent.GetInvocationList())
                 {
                     try
                     {

OpenSim/Region/Framework/Scenes/ScenePresence.cs

@@ -865,6 +865,9 @@ namespace OpenSim.Region.Framework.Scenes
         /// avatar is actual in the sim.  They can perform all actions.
         /// This change is made whenever an avatar enters a region, whether by crossing over from a neighbouring sim,
         /// teleporting in or on initial login.
+        ///
+        /// This method is on the critical path for transferring an avatar from one region to another.  Delay here
+        /// delays that crossing.
         /// </summary>
         public void MakeRootAgent(Vector3 pos, bool isFlying)
         {