* Add a large amount of extra locking to m_parts in SceneObjectGroup

* Should help stop any InvalidOperationExceptions caused by concurrent read/write 
* The extra locking should be okay, but I'm really surprised we've got away without mucho crashes due to this...

OpenSim/Region/Environment/Scenes/SceneObjectGroup.cs

@@ -48,6 +48,10 @@ namespace OpenSim.Region.Environment.Scenes
         private Encoding enc = Encoding.ASCII;
 
         protected SceneObjectPart m_rootPart;
+        
+        /// <summary>
+        /// The constituent parts of this group
+        /// </summary>
         protected Dictionary<LLUUID, SceneObjectPart> m_parts = new Dictionary<LLUUID, SceneObjectPart>();
 
         protected ulong m_regionHandle;
@@ -389,6 +393,8 @@ namespace OpenSim.Region.Environment.Scenes
 
             EntityIntersection returnresult = new EntityIntersection();
 
+            lock (m_parts)
+            {
                 foreach (SceneObjectPart part in m_parts.Values)
                 {
                     // Temporary commented to stop compiler warning
@@ -420,6 +426,7 @@ namespace OpenSim.Region.Environment.Scenes
                         }
                     }
                 }
+            }
             return returnresult;
         }
 
@@ -476,6 +483,9 @@ namespace OpenSim.Region.Environment.Scenes
             m_rootPart.ToXml(writer);
             writer.WriteEndElement();
             writer.WriteStartElement(String.Empty, "OtherParts", String.Empty);
+            
+            lock (m_parts)
+            {
                 foreach (SceneObjectPart part in m_parts.Values)
                 {
                     if (part.UUID != m_rootPart.UUID)
@@ -485,6 +495,8 @@ namespace OpenSim.Region.Environment.Scenes
                         writer.WriteEndElement();
                     }
                 }
+            }
+            
             writer.WriteEndElement();
             writer.WriteEndElement();
         }
@@ -507,6 +519,9 @@ namespace OpenSim.Region.Environment.Scenes
             writer.WriteStartElement(String.Empty, "SceneObjectGroup", String.Empty);
             m_rootPart.ToXml(writer);
             writer.WriteStartElement(String.Empty, "OtherParts", String.Empty);
+            
+            lock (m_parts)
+            {
                 foreach (SceneObjectPart part in m_parts.Values)
                 {
                     if (part.UUID != m_rootPart.UUID)
@@ -514,6 +529,8 @@ namespace OpenSim.Region.Environment.Scenes
                         part.ToXml(writer);
                     }
                 }
+            }
+            
             writer.WriteEndElement();
             writer.WriteEndElement();
         }
@@ -593,7 +610,12 @@ namespace OpenSim.Region.Environment.Scenes
         {
             SceneObjectPart newPart = part.Copy(m_scene.PrimIDAllocate(), OwnerID, GroupID, m_parts.Count);
             newPart.SetParent(this);
+            
+            lock (m_parts)
+            {
                 m_parts.Add(newPart.UUID, newPart);
+            }
+            
             SetPartAsRoot(newPart);
         }
 
@@ -685,7 +707,12 @@ namespace OpenSim.Region.Environment.Scenes
         {
             SceneObjectPart newPart = part.Copy(m_scene.PrimIDAllocate(), OwnerID, GroupID, m_parts.Count);
             newPart.SetParent(this);
+            
+            lock (m_parts)
+            {
                 m_parts.Add(newPart.UUID, newPart);
+            }
+            
             SetPartAsNonRoot(newPart);
         }
 
@@ -697,6 +724,8 @@ namespace OpenSim.Region.Environment.Scenes
         /// </summary>
         public void ResetIDs()
         {
+            // As this is only ever called for prims which are not currently part of the scene (and hence
+            // not accessible by clients), there should be no need to lock
             List<SceneObjectPart> partsList = new List<SceneObjectPart>(m_parts.Values);
             m_parts.Clear();
             foreach (SceneObjectPart part in partsList)
@@ -753,6 +782,8 @@ namespace OpenSim.Region.Environment.Scenes
         /// Examine this object's parts to see if they've changed sufficiently to warrant an update
         /// </summary>
         public override void Update()
+        {
+            lock (m_parts)
             {
                 if (Util.GetDistanceTo(lastPhysGroupPos, AbsolutePosition) > 0.02)
                 {                
@@ -760,6 +791,7 @@ namespace OpenSim.Region.Environment.Scenes
                     {
                         if (part.UpdateFlag == 0) part.UpdateFlag = 1;
                     }
+                    
                     lastPhysGroupPos = AbsolutePosition;
                 }
                 
@@ -772,6 +804,7 @@ namespace OpenSim.Region.Environment.Scenes
                     {
                         if (part.UpdateFlag == 0) part.UpdateFlag = 1;
                     }
+                    
                     lastPhysGroupRot = GroupRotation;
                 }
                 
@@ -780,22 +813,29 @@ namespace OpenSim.Region.Environment.Scenes
                     part.SendScheduledUpdates();
                 }
             }
+        }
 
         public void ScheduleFullUpdateToAvatar(ScenePresence presence)
+        {
+            lock (m_parts)
             {
                 foreach (SceneObjectPart part in m_parts.Values)
                 {
                     part.AddFullUpdateToAvatar(presence);
                 }
             }
+        }
 
         public void ScheduleTerseUpdateToAvatar(ScenePresence presence)
+        {
+            lock (m_parts)
             {
                 foreach (SceneObjectPart part in m_parts.Values)
                 {
                     part.AddTerseUpdateToAvatar(presence);
                 }
             }
+        }
 
         /// <summary>
         /// Schedule a full update for every part in this object
@@ -803,11 +843,15 @@ namespace OpenSim.Region.Environment.Scenes
         public void ScheduleGroupForFullUpdate()
         {
             HasGroupChanged = true;
+            
+            lock (m_parts)
+            {
                 foreach (SceneObjectPart part in m_parts.Values)
                 {
                     part.ScheduleFullUpdate();
                 }
             }
+        }
 
         /// <summary>
         /// 
@@ -815,11 +859,15 @@ namespace OpenSim.Region.Environment.Scenes
         public void ScheduleGroupForTerseUpdate()
         {
             HasGroupChanged = true;
+            
+            lock (m_parts)
+            {
                 foreach (SceneObjectPart part in m_parts.Values)
                 {
                     part.ScheduleTerseUpdate();
                 }
             }
+        }
 
         /// <summary>
         /// 
@@ -827,11 +875,15 @@ namespace OpenSim.Region.Environment.Scenes
         public void SendGroupFullUpdate()
         {
             HasGroupChanged = true;
+            
+            lock (m_parts)
+            {
                 foreach (SceneObjectPart part in m_parts.Values)
                 {
                     part.SendFullUpdateToAllClients();
                 }
             }
+        }
 
         public void QueueForUpdateCheck()
         {
@@ -844,11 +896,15 @@ namespace OpenSim.Region.Environment.Scenes
         public void SendGroupTerseUpdate()
         {
             HasGroupChanged = true;
+            
+            lock (m_parts)
+            {
                 foreach (SceneObjectPart part in m_parts.Values)
                 {
                     part.SendTerseUpdateToAllClients();
                 }
             }
+        }
 
         #endregion
 
@@ -860,6 +916,8 @@ namespace OpenSim.Region.Environment.Scenes
         /// <param name="linknum"></param>
         /// <returns>null if no child part with that linknum or child part</returns>
         public SceneObjectPart GetLinkNumPart(int linknum)
+        {
+            lock (m_parts)
             {
                 foreach (SceneObjectPart part in m_parts.Values)
                 {
@@ -868,6 +926,8 @@ namespace OpenSim.Region.Environment.Scenes
                         return part;
                     }
                 }
+            }
+            
             return null;
         }
 
@@ -892,6 +952,8 @@ namespace OpenSim.Region.Environment.Scenes
         /// <param name="localID"></param>
         /// <returns>null if a child part with the local ID was not found</returns>
         public SceneObjectPart GetChildPart(uint localID)
+        {
+            lock (m_parts)
             {
                 foreach (SceneObjectPart part in m_parts.Values)
                 {
@@ -900,6 +962,8 @@ namespace OpenSim.Region.Environment.Scenes
                         return part;
                     }
                 }
+            }
+            
             return null;
         }
 
@@ -925,6 +989,8 @@ namespace OpenSim.Region.Environment.Scenes
         /// <param name="localID"></param>
         /// <returns></returns>
         public bool HasChildPrim(uint localID)
+        {
+            lock (m_parts)
             {
                 foreach (SceneObjectPart part in m_parts.Values)
                 {
@@ -933,6 +999,7 @@ namespace OpenSim.Region.Environment.Scenes
                         return true;
                     }
                 }
+            }
             return false;
         }
         
@@ -988,7 +1055,11 @@ namespace OpenSim.Region.Environment.Scenes
             
             linkPart.LinkNum = m_parts.Count;
             
+            lock (m_parts)
+            {
                 m_parts.Add(linkPart.UUID, linkPart);
+            }
+            
             linkPart.SetParent(this);
 
             //if (linkPart.PhysActor != null)
@@ -1038,7 +1109,11 @@ namespace OpenSim.Region.Environment.Scenes
                 LLQuaternion worldRot = linkPart.GetWorldRotation();  
     
                 // Remove the part from this object
+                lock (m_parts)
+                {
                     m_parts.Remove(linkPart.UUID);
+                }
+                
                 linkPart.ParentID = 0;
 
                 if (linkPart.PhysActor != null)
@@ -1121,7 +1196,11 @@ namespace OpenSim.Region.Environment.Scenes
             part.SetParent(this);
             part.ParentID = m_rootPart.LocalId;
             part.LinkNum = m_parts.Count;
+            
+            lock (m_parts)
+            {
                 m_parts.Add(part.UUID, part);
+            }
 
             Vector3 axiomOldPos = new Vector3(part.OffsetPosition.X, part.OffsetPosition.Y, part.OffsetPosition.Z);
             axiomOldPos = oldGroupRotation*axiomOldPos;
@@ -1297,6 +1376,8 @@ namespace OpenSim.Region.Environment.Scenes
             if (part != null)
             {
                 // If we have children
+                lock (m_parts)
+                {                
                     if (m_parts.Count > 1)
                     {
                         foreach (SceneObjectPart parts in m_parts.Values)
@@ -1310,6 +1391,7 @@ namespace OpenSim.Region.Environment.Scenes
                     }
                 }
             }
+        }
 
         public void UpdateExtraParam(uint localID, ushort type, bool inUse, byte[] data)
         {
@@ -1465,6 +1547,8 @@ namespace OpenSim.Region.Environment.Scenes
             diff.Y = axDiff.y;
             diff.Z = axDiff.z;
 
+            lock (m_parts)
+            {
                 foreach (SceneObjectPart obPart in m_parts.Values)
                 {
                     if (obPart.UUID != m_rootPart.UUID)
@@ -1472,6 +1556,8 @@ namespace OpenSim.Region.Environment.Scenes
                         obPart.OffsetPosition = obPart.OffsetPosition + diff;
                     }
                 }
+            }
+            
             AbsolutePosition = newPos;
             ScheduleGroupForTerseUpdate();
         }
@@ -1562,6 +1648,8 @@ namespace OpenSim.Region.Environment.Scenes
                 m_scene.PhysicsScene.AddPhysicsActorTaint(m_rootPart.PhysActor);
             }
 
+            lock (m_parts)
+            {
                 foreach (SceneObjectPart prim in m_parts.Values)
                 {
                     if (prim.UUID != m_rootPart.UUID)
@@ -1579,6 +1667,8 @@ namespace OpenSim.Region.Environment.Scenes
                         prim.ScheduleTerseUpdate();
                     }
                 }
+            }
+            
             m_rootPart.ScheduleTerseUpdate();
         }
 
@@ -1692,16 +1782,21 @@ namespace OpenSim.Region.Environment.Scenes
         #endregion
 
         public override void UpdateMovement()
+        {
+            lock (m_parts)
             {
                 foreach (SceneObjectPart part in m_parts.Values)
                 {
                     part.UpdateMovement();
                 }
             }
+        }
+        
         public float GetTimeDilation()
         {
             return m_scene.TimeDilation;
         }
+        
         /// <summary>
         /// Added as a way for the storage provider to reset the scene, 
         /// most likely a better way to do this sort of thing but for now...
@@ -1719,12 +1814,17 @@ namespace OpenSim.Region.Environment.Scenes
         /// <param name="part"></param>
         public void AddPart(SceneObjectPart part)
         {
-            lock (m_parts) {
+            lock (m_parts) 
+            {
                 part.SetParent(this);
                 part.LinkNum = m_parts.Count;
-                try {
+                
+                try 
+                {
                     m_parts.Add(part.UUID, part);
-                } catch (Exception e) {
+                } 
+                catch (Exception e) 
+                {
                     m_log.Error("Failed to add scened object part", e);
                 }
             }
@@ -1734,6 +1834,8 @@ namespace OpenSim.Region.Environment.Scenes
         /// 
         /// </summary>
         public void UpdateParentIDs()
+        {
+            lock (m_parts)
             {
                 foreach (SceneObjectPart part in m_parts.Values)
                 {
@@ -1743,14 +1845,18 @@ namespace OpenSim.Region.Environment.Scenes
                     }
                 }
             }
+        }
 
         public void RegenerateFullIDs()
+        {
+            lock (m_parts)
             {
                 foreach (SceneObjectPart part in m_parts.Values)
                 {
                     part.UUID = LLUUID.Random();
                 }
             }
+        }
 
         public void ResetChildPrimPhysicsPositions()
         {
@@ -1803,6 +1909,9 @@ namespace OpenSim.Region.Environment.Scenes
         public void DeleteGroup()
         {
             DetachFromBackup(this);
+            
+            lock (m_parts)
+            {
                 foreach (SceneObjectPart part in m_parts.Values)
                 {
                     List<ScenePresence> avatars = GetScenePresences();
@@ -1817,6 +1926,7 @@ namespace OpenSim.Region.Environment.Scenes
                     }
                 }
             }
+        }
 
         /// <summary>
         /// Delete all the parts in this group.
@@ -1829,11 +1939,11 @@ namespace OpenSim.Region.Environment.Scenes
                 {
                     part.StopScripts();
                 }
-            }
                             
                 m_rootPart = null;
                 m_parts.Clear();                
             }
+        }
 
         public void AddScriptLPS(int count)
         {
@@ -1857,10 +1967,10 @@ namespace OpenSim.Region.Environment.Scenes
         }
 
         public void ApplyPhysics(bool m_physicalPrim)
-        {
-            if (m_parts.Count > 1)
         {
             lock (m_parts)
+            {            
+                if (m_parts.Count > 1)
                 {
                     m_rootPart.ApplyPhysics(m_rootPart.ObjectFlags, m_physicalPrim);
                     foreach (SceneObjectPart part in m_parts.Values)
@@ -1874,12 +1984,12 @@ namespace OpenSim.Region.Environment.Scenes
 
                     }
                 }
-            }
                 else
                 {
                     m_rootPart.ApplyPhysics(m_rootPart.ObjectFlags, m_physicalPrim);
                 }                
             }
+        }
 
         public void SetOwnerId(LLUUID userId)
         {