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();
             }
@@ -285,30 +300,38 @@ 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);
 
-                if (group.GetSittingAvatarsCount() != 0)
+            if (group.GetSittingAvatarsCount() != 0)
-                {
+            {
 //                    m_log.WarnFormat(
 //                        "[ATTACHMENTS MODULE]: Ignoring request to attach {0} {1} to {2} on {3} since {4} avatars are still sitting on it",
 //                        group.Name, group.LocalId, sp.Name, attachmentPt, group.GetSittingAvatarsCount());
 
-                    return false;
+                return false;
-                }
+            }
 
-                if (sp.GetAttachments(attachmentPt).Contains(group))
+            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;
+                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)
             {
@@ -426,12 +434,10 @@ 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)
             {
-                foreach (KeyValuePair<UUID, uint> rez in rezlist)
+                RezSingleAttachmentFromInventory(sp, rez.Key, rez.Value);
-                {
-                    RezSingleAttachmentFromInventory(sp, rez.Key, rez.Value);
-                }
             }
         }
 
@@ -511,25 +517,33 @@ namespace OpenSim.Region.CoreModules.Avatar.Attachments
 
         public void DetachSingleAttachmentToInv(IScenePresence sp, SceneObjectGroup so)
         {
+            if (so.AttachedAvatar != sp.UUID)
+            {
+                m_log.WarnFormat(
+                    "[ATTACHMENTS MODULE]: Tried to detach object {0} from {1} {2} but attached avatar id was {3} in {4}",
+                    so.Name, sp.Name, sp.UUID, so.AttachedAvatar, m_scene.RegionInfo.RegionName);
+
+                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);
 
-                if (so.AttachedAvatar != sp.UUID)
-                {
-                    m_log.WarnFormat(
-                        "[ATTACHMENTS MODULE]: Tried to detach object {0} from {1} {2} but attached avatar id was {3} in {4}",
-                        so.Name, sp.Name, sp.UUID, so.AttachedAvatar, m_scene.RegionInfo.RegionName);
-
-                    return;
-                }
-
                 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"
@@ -793,91 +821,87 @@ 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;
 
+            SceneObjectGroup objatt;
+
+            if (itemID != UUID.Zero)
+                objatt = m_invAccessModule.RezObject(sp.ControllingClient,
+                    itemID, Vector3.Zero, Vector3.Zero, UUID.Zero, (byte)1, true,
+                    false, false, sp.UUID, true);
+            else
+                objatt = m_invAccessModule.RezObject(sp.ControllingClient,
+                    null, assetID, Vector3.Zero, Vector3.Zero, UUID.Zero, (byte)1, true,
+                    false, false, sp.UUID, true);
+
+            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)
             {
-                SceneObjectGroup objatt;
-
-                if (itemID != UUID.Zero)
-                    objatt = m_invAccessModule.RezObject(sp.ControllingClient,
-                        itemID, Vector3.Zero, Vector3.Zero, UUID.Zero, (byte)1, true,
-                        false, false, sp.UUID, true);
-                else
-                    objatt = m_invAccessModule.RezObject(sp.ControllingClient,
-                        null, assetID, Vector3.Zero, Vector3.Zero, UUID.Zero, (byte)1, true,
-                        false, false, sp.UUID, true);
-
-                if (objatt != null)
-                {
 //                    m_log.DebugFormat(
 //                        "[ATTACHMENTS MODULE]: Rezzed single object {0} for attachment to {1} on point {2} in {3}",
 //                        objatt.Name, sp.Name, attachmentPt, m_scene.Name);
 
-                    // HasGroupChanged is being set from within RezObject.  Ideally it would be set by the caller.
+                // HasGroupChanged is being set from within RezObject.  Ideally it would be set by the caller.
-                    objatt.HasGroupChanged = false;
+                objatt.HasGroupChanged = false;
-                    bool tainted = false;
+                bool tainted = false;
-                    if (attachmentPt != 0 && attachmentPt != objatt.AttachmentPoint)
+                if (attachmentPt != 0 && attachmentPt != objatt.AttachmentPoint)
-                        tainted = true;
+                    tainted = true;
 
-                    // FIXME: Detect whether it's really likely for AttachObject to throw an exception in the normal
+                // FIXME: Detect whether it's really likely for AttachObject to throw an exception in the normal
-                    // course of events.  If not, then it's probably not worth trying to recover the situation
+                // course of events.  If not, then it's probably not worth trying to recover the situation
-                    // since this is more likely to trigger further exceptions and confuse later debugging.  If
+                // since this is more likely to trigger further exceptions and confuse later debugging.  If
-                    // exceptions can be thrown in expected error conditions (not NREs) then make this consistent
+                // exceptions can be thrown in expected error conditions (not NREs) then make this consistent
-                    // since other normal error conditions will simply return false instead.
+                // since other normal error conditions will simply return false instead.
-                    // This will throw if the attachment fails
+                // This will throw if the attachment fails
-                    try
+                try
-                    {
-                        AttachObjectInternal(sp, objatt, attachmentPt, false, false);
-                    }
-                    catch (Exception e)
-                    {
-                        m_log.ErrorFormat(
-                            "[ATTACHMENTS MODULE]: Failed to attach {0} {1} for {2}, exception {3}{4}",
-                            objatt.Name, objatt.UUID, sp.Name, e.Message, e.StackTrace);
-
-                        // Make sure the object doesn't stick around and bail
-                        sp.RemoveAttachment(objatt);
-                        m_scene.DeleteSceneObject(objatt, false);
-                        return null;
-                    }
-
-                    if (tainted)
-                        objatt.HasGroupChanged = true;
-
-                    // Fire after attach, so we don't get messy perms dialogs
-                    // 4 == AttachedRez
-                    objatt.CreateScriptInstances(0, true, m_scene.DefaultScriptEngine, 4);
-                    objatt.ResumeScripts();
-
-                    // 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
                 {
-                    m_log.WarnFormat(
+                    AttachObjectInternal(sp, objatt, attachmentPt, false, false);
-                        "[ATTACHMENTS MODULE]: Could not retrieve item {0} for attaching to avatar {1} at point {2}",
-                        itemID, sp.Name, attachmentPt);
                 }
-            }
+                catch (Exception e)
+                {
+                    m_log.ErrorFormat(
+                        "[ATTACHMENTS MODULE]: Failed to attach {0} {1} for {2}, exception {3}{4}",
+                        objatt.Name, objatt.UUID, sp.Name, e.Message, e.StackTrace);
 
-            return null;
+                    // Make sure the object doesn't stick around and bail
+                    sp.RemoveAttachment(objatt);
+                    m_scene.DeleteSceneObject(objatt, false);
+                    return null;
+                }
+
+                if (tainted)
+                    objatt.HasGroupChanged = true;
+
+                // Fire after attach, so we don't get messy perms dialogs
+                // 4 == AttachedRez
+                objatt.CreateScriptInstances(0, true, m_scene.DefaultScriptEngine, 4);
+                objatt.ResumeScripts();
+
+                // 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;
+            }
         }
 
         /// <summary>
@@ -1027,17 +1051,14 @@ namespace OpenSim.Region.CoreModules.Avatar.Attachments
             ScenePresence sp = m_scene.GetScenePresence(remoteClient.AgentId);
             if (sp != null)
             {
-                lock (sp.AttachmentsSyncLock)
+                List<SceneObjectGroup> attachments = sp.GetAttachments();
-                {
-                    List<SceneObjectGroup> attachments = sp.GetAttachments();
 
-                    foreach (SceneObjectGroup group in attachments)
+                foreach (SceneObjectGroup group in attachments)
+                {
+                    if (group.FromItemID == itemID && group.FromItemID != UUID.Zero)
                     {
-                        if (group.FromItemID == itemID && group.FromItemID != UUID.Zero)
+                        DetachSingleAttachmentToInv(sp, group);
-                        {
+                        return;
-                            DetachSingleAttachmentToInv(sp, group);
-                            return;
-                        }
                     }
                 }
             }