Start locking entire add/remove operations on an IScenePresence.AttachmentsSyncLock object

Attach and detach packets are processed asynchronously when received from a viewer.
Bugs like http://opensimulator.org/mantis/view.php?id=5644 indicate that in some situations (such as attaching/detaching entire folders of objects at once), there are race conditions between these threads.
Since multiple data structures need to be updated on attach/detach, it's not enough to lock the individual collections.
Therefore, this commit introduces a new IScenePresence.AttachmentsSyncLock which add/remove operations lock on.

OpenSim/Region/CoreModules/Avatar/Attachments/AttachmentsModule.cs

@@ -240,15 +240,17 @@ namespace OpenSim.Region.CoreModules.Avatar.Attachments
         
         private bool AttachObject(IScenePresence sp, SceneObjectGroup group, uint attachmentPt, bool silent)
         {
-//            m_log.DebugFormat(
+            lock (sp.AttachmentsSyncLock)
-//                "[ATTACHMENTS MODULE]: Attaching object {0} {1} to {2} point {3} from ground (silent = {4})",
+            {
-//                group.Name, group.LocalId, sp.Name, attachmentPt, silent);
+    //            m_log.DebugFormat(
+    //                "[ATTACHMENTS MODULE]: Attaching object {0} {1} to {2} point {3} from ground (silent = {4})",
+    //                group.Name, group.LocalId, sp.Name, attachmentPt, silent);
     
                 if (sp.GetAttachments(attachmentPt).Contains(group))
                 {
-//                m_log.WarnFormat(
+    //                m_log.WarnFormat(
-//                    "[ATTACHMENTS MODULE]: Ignoring request to attach {0} {1} to {2} on {3} since it's already attached",
+    //                    "[ATTACHMENTS MODULE]: Ignoring request to attach {0} {1} to {2} on {3} since it's already attached",
-//                    group.Name, group.LocalId, sp.Name, AttachmentPt);
+    //                    group.Name, group.LocalId, sp.Name, AttachmentPt);
     
                     return false;
                 }
@@ -313,6 +315,7 @@ namespace OpenSim.Region.CoreModules.Avatar.Attachments
                 }
     
                 AttachToAgent(sp, group, attachmentPt, attachPos, silent);
+            }
 
             return true;
         }
@@ -321,15 +324,27 @@ namespace OpenSim.Region.CoreModules.Avatar.Attachments
             IClientAPI remoteClient, 
             RezMultipleAttachmentsFromInvPacket.HeaderDataBlock header,
             RezMultipleAttachmentsFromInvPacket.ObjectDataBlock[] objects)
+        {
+            ScenePresence sp = m_scene.GetScenePresence(remoteClient.AgentId);
+
+            if (sp == null)
+            {
+                m_log.ErrorFormat(
+                    "[ATTACHMENTS MODULE]: Could not find presence for client {0} {1} in RezMultipleAttachmentsFromInventory()",
+                    remoteClient.Name, remoteClient.AgentId);
+                return;
+            }
+
+            lock (sp.AttachmentsSyncLock)
             {
                 foreach (RezMultipleAttachmentsFromInvPacket.ObjectDataBlock obj in objects)
                 {
-                RezSingleAttachmentFromInventory(remoteClient, obj.ItemID, obj.AttachmentPt);
+                    RezSingleAttachmentFromInventory(sp, obj.ItemID, obj.AttachmentPt);
+                }
             }
         }
         
-        public ISceneEntity RezSingleAttachmentFromInventory(
+        public ISceneEntity RezSingleAttachmentFromInventory(IClientAPI remoteClient, UUID itemID, uint AttachmentPt)
-            IClientAPI remoteClient, UUID itemID, uint AttachmentPt)
         {
 //            m_log.DebugFormat(
 //                "[ATTACHMENTS MODULE]: Rezzing attachment to point {0} from item {1} for {2}", 
@@ -345,6 +360,11 @@ namespace OpenSim.Region.CoreModules.Avatar.Attachments
                 return null;
             }
 
+            return RezSingleAttachmentFromInventory(sp, itemID, AttachmentPt);
+        }
+
+        public ISceneEntity RezSingleAttachmentFromInventory(ScenePresence sp, UUID itemID, uint AttachmentPt)
+        {
             // TODO: this short circuits multiple attachments functionality  in  LL viewer 2.1+ and should
             // be removed when that functionality is implemented in opensim
             AttachmentPt &= 0x7f;
@@ -362,6 +382,8 @@ namespace OpenSim.Region.CoreModules.Avatar.Attachments
         {
             IInventoryAccessModule invAccess = m_scene.RequestModuleInterface<IInventoryAccessModule>();
             if (invAccess != null)
+            {
+                lock (sp.AttachmentsSyncLock)
                 {
                     SceneObjectGroup objatt;
     
@@ -374,9 +396,9 @@ namespace OpenSim.Region.CoreModules.Avatar.Attachments
                             null, assetID, Vector3.Zero, Vector3.Zero, UUID.Zero, (byte)1, true,
                             false, false, sp.UUID, true);
     
-//                m_log.DebugFormat(
+    //                m_log.DebugFormat(
-//                    "[ATTACHMENTS MODULE]: Retrieved single object {0} for attachment to {1} on point {2}",
+    //                    "[ATTACHMENTS MODULE]: Retrieved single object {0} for attachment to {1} on point {2}",
-//                    objatt.Name, remoteClient.Name, AttachmentPt);
+    //                    objatt.Name, remoteClient.Name, AttachmentPt);
                     
                     if (objatt != null)
                     {
@@ -413,6 +435,8 @@ namespace OpenSim.Region.CoreModules.Avatar.Attachments
     
                         // Do this last so that event listeners have access to all the effects of the attachment
                         m_scene.EventManager.TriggerOnAttach(objatt.LocalId, itemID, sp.UUID);
+
+                        return objatt;
                     }
                     else
                     {
@@ -420,8 +444,7 @@ namespace OpenSim.Region.CoreModules.Avatar.Attachments
                             "[ATTACHMENTS MODULE]: Could not retrieve item {0} for attaching to avatar {1} at point {2}",
                             itemID, sp.Name, attachmentPt);
                     }
-                
+                }
-                return objatt;
             }
             
             return null;
@@ -473,6 +496,8 @@ namespace OpenSim.Region.CoreModules.Avatar.Attachments
         {
             ScenePresence presence;
             if (m_scene.TryGetScenePresence(remoteClient.AgentId, out presence))
+            {
+                lock (presence.AttachmentsSyncLock)
                 {
                     // Save avatar attachment information
                     m_log.Debug("[ATTACHMENTS MODULE]: Detaching from UserID: " + remoteClient.AgentId + ", ItemID: " + itemID);
@@ -484,6 +509,7 @@ namespace OpenSim.Region.CoreModules.Avatar.Attachments
                     DetachSingleAttachmentToInv(itemID, presence);
                 }
             }
+        }
 
         public void DetachSingleAttachmentToGround(uint soLocalId, IClientAPI remoteClient)
         {
@@ -507,6 +533,8 @@ namespace OpenSim.Region.CoreModules.Avatar.Attachments
 
             ScenePresence presence;
             if (m_scene.TryGetScenePresence(remoteClient.AgentId, out presence))
+            {
+                lock (presence.AttachmentsSyncLock)
                 {
                     if (!m_scene.Permissions.CanRezObject(
                         so.PrimCount, remoteClient.AgentId, presence.AbsolutePosition))
@@ -527,6 +555,7 @@ namespace OpenSim.Region.CoreModules.Avatar.Attachments
 
                 m_scene.EventManager.TriggerOnAttach(so.LocalId, so.UUID, UUID.Zero);
             }
+        }
 
         /// <summary>
         /// Detach the given scene object to the ground.
@@ -567,6 +596,8 @@ namespace OpenSim.Region.CoreModules.Avatar.Attachments
             EntityBase[] detachEntities = m_scene.GetEntities();
             SceneObjectGroup group;
 
+            lock (sp.AttachmentsSyncLock)
+            {
                 foreach (EntityBase entity in detachEntities)
                 {
                     if (entity is SceneObjectGroup)
@@ -602,6 +633,7 @@ namespace OpenSim.Region.CoreModules.Avatar.Attachments
                     }
                 }
             }
+        }
         
         public void UpdateAttachmentPosition(SceneObjectGroup sog, Vector3 pos)
         {

OpenSim/Region/Framework/Interfaces/IAttachmentsModule.cs

@@ -87,6 +87,15 @@ namespace OpenSim.Region.Framework.Interfaces
         /// <returns>The scene object that was attached.  Null if the scene object could not be found</returns>
         ISceneEntity RezSingleAttachmentFromInventory(IClientAPI remoteClient, UUID itemID, uint AttachmentPt);
 
+        /// <summary>
+        /// Rez an attachment from user inventory and change inventory status to match.
+        /// </summary>
+        /// <param name="sp"></param>
+        /// <param name="itemID"></param>
+        /// <param name="AttachmentPt"></param>
+        /// <returns>The scene object that was attached.  Null if the scene object could not be found</returns>
+        ISceneEntity RezSingleAttachmentFromInventory(ScenePresence sp, UUID itemID, uint AttachmentPt);
+
         /// <summary>
         /// Rez multiple attachments from a user's inventory
         /// </summary>

OpenSim/Region/Framework/Interfaces/IScenePresence.cs

@@ -60,6 +60,14 @@ namespace OpenSim.Region.Framework.Interfaces
         /// </remarks>
         AvatarAppearance Appearance { get; set; }
 
+        /// <summary>
+        /// The AttachmentsModule synchronizes on this to avoid race conditions between commands to add and remove attachments.
+        /// </summary>
+        /// <remarks>
+        /// All add and remove attachment operations must synchronize on this for the lifetime of their operations.
+        /// </remarks>
+        Object AttachmentsSyncLock { get; }
+        
         /// <summary>
         /// The scene objects attached to this avatar.
         /// </summary>

OpenSim/Region/Framework/Scenes/ScenePresence.cs

@@ -120,6 +120,8 @@ namespace OpenSim.Region.Framework.Scenes
         /// </remarks>
         protected List<SceneObjectGroup> m_attachments = new List<SceneObjectGroup>();
 
+        public Object AttachmentsSyncLock { get; private set; }
+
         private Dictionary<UUID, ScriptControllers> scriptedcontrols = new Dictionary<UUID, ScriptControllers>();
         private ScriptControlled IgnoredControls = ScriptControlled.CONTROL_ZERO;
         private ScriptControlled LastCommands = ScriptControlled.CONTROL_ZERO;
@@ -709,6 +711,8 @@ namespace OpenSim.Region.Framework.Scenes
         public ScenePresence(
             IClientAPI client, Scene world, RegionInfo reginfo, AvatarAppearance appearance, PresenceType type)
         {
+            AttachmentsSyncLock = new Object();
+
             m_sendCourseLocationsMethod = SendCoarseLocationsDefault;
             m_sceneViewer = new SceneViewer(this);
             m_animator = new ScenePresenceAnimator(this);