Get attachment script state before taking sp.AttachmentsSyncLock() to avoid race conditions between closing agents and scripts that may be doing attachment manipulation.

This is in an effort to resolve http://opensimulator.org/mantis/view.php?id=6557

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

@@ -241,12 +241,27 @@ namespace OpenSim.Region.CoreModules.Avatar.Attachments
 
 //            m_log.DebugFormat("[ATTACHMENTS MODULE]: Saving changed attachments for {0}", sp.Name);
 
+            List<SceneObjectGroup> attachments = sp.GetAttachments();
+
+            if (attachments.Count <= 0)
+                return;
+
+            Dictionary<SceneObjectGroup, string> scriptStates = new Dictionary<SceneObjectGroup, string>();
+
+            foreach (SceneObjectGroup so in attachments)
+            {
+                // Scripts MUST be snapshotted before the object is
+                // removed from the scene because doing otherwise will
+                // clobber the run flag
+                // This must be done outside the sp.AttachmentSyncLock so that there is no risk of a deadlock from
+                // scripts performing attachment operations at the same time.  Getting object states stops the scripts.
+                scriptStates[so] = PrepareScriptInstanceForSave(so, false);
+            }
+
             lock (sp.AttachmentsSyncLock)
             {
-                foreach (SceneObjectGroup so in sp.GetAttachments())
+                foreach (SceneObjectGroup so in attachments)
-                {
+                    UpdateDetachedObject(sp, so, scriptStates[so]);
-                    UpdateDetachedObject(sp, so);
-                }
     
                 sp.ClearAttachments();
             }
@@ -285,8 +300,6 @@ namespace OpenSim.Region.CoreModules.Avatar.Attachments
         
         private bool AttachObjectInternal(IScenePresence sp, SceneObjectGroup group, uint attachmentPt, bool silent, bool temp)
         {
-            lock (sp.AttachmentsSyncLock)
-            {
 //                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);
@@ -302,13 +315,23 @@ namespace OpenSim.Region.CoreModules.Avatar.Attachments
 
             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;
             }
 
+            // Remove any previous attachments
+            List<SceneObjectGroup> existingAttachments = sp.GetAttachments(attachmentPt);
+            string existingAttachmentScriptState = null;
+
+            // At the moment we can only deal with a single attachment
+            if (existingAttachments.Count != 0 && existingAttachments[0].FromItemID != UUID.Zero)
+                DetachSingleAttachmentToInv(sp, group);
+
+            lock (sp.AttachmentsSyncLock)
+            {
                 Vector3 attachPos = group.AbsolutePosition;
 
                 // TODO: this short circuits multiple attachments functionality  in  LL viewer 2.1+ and should
@@ -352,21 +375,6 @@ namespace OpenSim.Region.CoreModules.Avatar.Attachments
 
         private void UpdateUserInventoryWithAttachment(IScenePresence sp, SceneObjectGroup group, uint attachmentPt, bool temp)
         {
-            // Remove any previous attachments
-            List<SceneObjectGroup> attachments = sp.GetAttachments(attachmentPt);
-
-            // At the moment we can only deal with a single attachment
-            if (attachments.Count != 0)
-            {
-                if (attachments[0].FromItemID != UUID.Zero)
-                    DetachSingleAttachmentToInvInternal(sp, attachments[0]);
-            // Error logging commented because UUID.Zero now means temp attachment
-//                else
-//                    m_log.WarnFormat(
-//                        "[ATTACHMENTS MODULE]: When detaching existing attachment {0} {1} at point {2} to make way for {3} {4} for {5}, couldn't find the associated item ID to adjust inventory attachment record!",
-//                        attachments[0].Name, attachments[0].LocalId, attachmentPt, group.Name, group.LocalId, sp.Name);
-            }
-
             // Add the new attachment to inventory if we don't already have it.
             if (!temp)
             {
@@ -426,14 +434,12 @@ namespace OpenSim.Region.CoreModules.Avatar.Attachments
                 return;
 
             //                m_log.DebugFormat("[ATTACHMENTS MODULE]: Rezzing multiple attachments from inventory for {0}", sp.Name);
-            lock (sp.AttachmentsSyncLock)
+
-            {
             foreach (KeyValuePair<UUID, uint> rez in rezlist)
             {
                 RezSingleAttachmentFromInventory(sp, rez.Key, rez.Value);
             }
         }
-        }
 
         public void DetachSingleAttachmentToGround(IScenePresence sp, uint soLocalId)
         {
@@ -511,11 +517,6 @@ namespace OpenSim.Region.CoreModules.Avatar.Attachments
 
         public void DetachSingleAttachmentToInv(IScenePresence sp, SceneObjectGroup so)
         {
-            lock (sp.AttachmentsSyncLock)
-            {
-                // Save avatar attachment information
-//                m_log.Debug("[ATTACHMENTS MODULE]: Detaching from UserID: " + sp.UUID + ", ItemID: " + itemID);
-
             if (so.AttachedAvatar != sp.UUID)
             {
                 m_log.WarnFormat(
@@ -525,11 +526,24 @@ namespace OpenSim.Region.CoreModules.Avatar.Attachments
                 return;
             }
 
+            // Scripts MUST be snapshotted before the object is
+            // removed from the scene because doing otherwise will
+            // clobber the run flag
+            // This must be done outside the sp.AttachmentSyncLock so that there is no risk of a deadlock from
+            // scripts performing attachment operations at the same time.  Getting object states stops the scripts.
+            string scriptedState = PrepareScriptInstanceForSave(so, true);
+
+            lock (sp.AttachmentsSyncLock)
+            {
+                // Save avatar attachment information
+//                m_log.Debug("[ATTACHMENTS MODULE]: Detaching from UserID: " + sp.UUID + ", ItemID: " + itemID);
+
                 bool changed = sp.Appearance.DetachAttachment(so.FromItemID);
                 if (changed && m_scene.AvatarFactory != null)
                     m_scene.AvatarFactory.QueueAppearanceSave(sp.UUID);
 
-                DetachSingleAttachmentToInvInternal(sp, so);
+                sp.RemoveAttachment(so);
+                UpdateDetachedObject(sp, so, scriptedState);
             }
         }
         
@@ -739,8 +753,27 @@ namespace OpenSim.Region.CoreModules.Avatar.Attachments
             return newItem;
         }
 
-        private string GetObjectScriptStates(SceneObjectGroup grp)
+        /// <summary>
+        /// Prepares the script instance for save.
+        /// </summary>
+        /// <remarks>
+        /// This involves triggering the detach event and getting the script state (which also stops the script)
+        /// This MUST be done outside sp.AttachmentsSyncLock, since otherwise there is a chance of deadlock if a 
+        /// running script is performing attachment operations.
+        /// </remarks>
+        /// <returns>
+        /// The script state ready for persistence.
+        /// </returns>
+        /// <param name='grp'>
+        /// </param>
+        /// <param name='fireDetachEvent'>
+        /// If true, then fire the script event before we save its state.
+        /// </param>
+        private string PrepareScriptInstanceForSave(SceneObjectGroup grp, bool fireDetachEvent)
         {
+            if (fireDetachEvent)
+                m_scene.EventManager.TriggerOnAttach(grp.LocalId, grp.FromItemID, UUID.Zero);
+
             using (StringWriter sw = new StringWriter())
             {
                 using (XmlTextWriter writer = new XmlTextWriter(sw))
@@ -752,7 +785,7 @@ namespace OpenSim.Region.CoreModules.Avatar.Attachments
             }
         }
 
-        private void UpdateDetachedObject(IScenePresence sp, SceneObjectGroup so)
+        private void UpdateDetachedObject(IScenePresence sp, SceneObjectGroup so, string scriptedState)
         {
             // Don't save attachments for HG visitors, it
             // messes up their inventory. When a HG visitor logs
@@ -765,11 +798,6 @@ namespace OpenSim.Region.CoreModules.Avatar.Attachments
                     && (m_scene.UserManagementModule == null
                     || m_scene.UserManagementModule.IsLocalGridUser(sp.UUID));
 
-            // Scripts MUST be snapshotted before the object is
-            // removed from the scene because doing otherwise will
-            // clobber the run flag
-            string scriptedState = GetObjectScriptStates(so);
-
             // Remove the object from the scene so no more updates
             // are sent. Doing this before the below changes will ensure
             // updates can't cause "HUD artefacts"
@@ -793,24 +821,12 @@ namespace OpenSim.Region.CoreModules.Avatar.Attachments
             so.RemoveScriptInstances(true);
         }
 
-        private void DetachSingleAttachmentToInvInternal(IScenePresence sp, SceneObjectGroup so)
-        {
-            //            m_log.DebugFormat("[ATTACHMENTS MODULE]: Detaching item {0} to inventory for {1}", itemID, sp.Name);
-
-            m_scene.EventManager.TriggerOnAttach(so.LocalId, so.FromItemID, UUID.Zero);
-            sp.RemoveAttachment(so);
-
-            UpdateDetachedObject(sp, so);
-        }
-
         private SceneObjectGroup RezSingleAttachmentFromInventoryInternal(
             IScenePresence sp, UUID itemID, UUID assetID, uint attachmentPt)
         {
             if (m_invAccessModule == null)
                 return null;
 
-            lock (sp.AttachmentsSyncLock)
-            {
             SceneObjectGroup objatt;
 
             if (itemID != UUID.Zero)
@@ -822,7 +838,24 @@ namespace OpenSim.Region.CoreModules.Avatar.Attachments
                     null, assetID, Vector3.Zero, Vector3.Zero, UUID.Zero, (byte)1, true,
                     false, false, sp.UUID, true);
 
-                if (objatt != null)
+            if (objatt == null)
+            {
+                m_log.WarnFormat(
+                    "[ATTACHMENTS MODULE]: Could not retrieve item {0} for attaching to avatar {1} at point {2}",
+                    itemID, sp.Name, attachmentPt);
+
+                return null;
+            }
+
+            // Remove any previous attachments
+            List<SceneObjectGroup> attachments = sp.GetAttachments(attachmentPt);
+            string previousAttachmentScriptedState = null;
+
+            // At the moment we can only deal with a single attachment
+            if (attachments.Count != 0)
+                DetachSingleAttachmentToInv(sp, attachments[0]);
+
+            lock (sp.AttachmentsSyncLock)
             {
 //                    m_log.DebugFormat(
 //                        "[ATTACHMENTS MODULE]: Rezzed single object {0} for attachment to {1} on point {2} in {3}",
@@ -869,15 +902,6 @@ namespace OpenSim.Region.CoreModules.Avatar.Attachments
 
                 return objatt;
             }
-                else
-                {
-                    m_log.WarnFormat(
-                        "[ATTACHMENTS MODULE]: Could not retrieve item {0} for attaching to avatar {1} at point {2}",
-                        itemID, sp.Name, attachmentPt);
-                }
-            }
-
-            return null;
         }
 
         /// <summary>
@@ -1026,8 +1050,6 @@ namespace OpenSim.Region.CoreModules.Avatar.Attachments
 
             ScenePresence sp = m_scene.GetScenePresence(remoteClient.AgentId);
             if (sp != null)
-            {
-                lock (sp.AttachmentsSyncLock)
             {
                 List<SceneObjectGroup> attachments = sp.GetAttachments();
 
@@ -1041,7 +1063,6 @@ namespace OpenSim.Region.CoreModules.Avatar.Attachments
                 }
             }
         }
-        }
 
         private void Client_OnObjectDrop(uint soLocalId, IClientAPI remoteClient)
         {