Prevent a race condition between the script engine backup thread and script removal by locking on the script's EventQueue and only proceeding if it's flagged as still running.

Relates to http://opensimulator.org/mantis/view.php?id=7407

OpenSim/Region/ScriptEngine/Interfaces/IScriptInstance.cs

@@ -178,8 +178,9 @@ namespace OpenSim.Region.ScriptEngine.Interfaces
         /// <param name="timeout"></param>
         /// How many milliseconds we will wait for an existing script event to finish before
         /// forcibly aborting that event.
+        /// <param name="clearEventQueue">If true then the event queue is also cleared</param>
         /// <returns>true if the script was successfully stopped, false otherwise</returns>
-        bool Stop(int timeout);
+        bool Stop(int timeout, bool clearEventQueue = false);
 
         void SetState(string state);
 

OpenSim/Region/ScriptEngine/Shared/Instance/ScriptInstance.cs

@@ -564,7 +564,7 @@ namespace OpenSim.Region.ScriptEngine.Shared.Instance
             }
         }
 
-        public bool Stop(int timeout)
+        public bool Stop(int timeout, bool clearEventQueue = false)
         {
             if (DebugLevel >= 1)
                 m_log.DebugFormat(
@@ -575,6 +575,9 @@ namespace OpenSim.Region.ScriptEngine.Shared.Instance
 
             lock (EventQueue)
             {
+                if (clearEventQueue)
+                    ClearQueue();
+
                 if (!Running)
                     return true;
 
@@ -1065,6 +1068,12 @@ namespace OpenSim.Region.ScriptEngine.Shared.Instance
 
         public void SaveState()
         {
+            // We need to lock here to avoid any race with a thread that is removing this script.
+            lock (EventQueue)
+            {
+                if (!Running)
+                    return;
+
                 // If we're currently in an event, just tell it to save upon return
                 //
                 if (m_InEvent)
@@ -1073,9 +1082,9 @@ namespace OpenSim.Region.ScriptEngine.Shared.Instance
                     return;
                 }
 
-//            m_log.DebugFormat(
+    //            m_log.DebugFormat(
-//                "[SCRIPT INSTANCE]: Saving state for script {0} (id {1}) in part {2} (id {3}) in object {4} in {5}",
+    //                "[SCRIPT INSTANCE]: Saving state for script {0} (id {1}) in part {2} (id {3}) in object {4} in {5}",
-//                ScriptTask.Name, ScriptTask.ItemID, Part.Name, Part.UUID, Part.ParentGroup.Name, Engine.World.Name);
+    //                ScriptTask.Name, ScriptTask.ItemID, Part.Name, Part.UUID, Part.ParentGroup.Name, Engine.World.Name);
 
                 PluginData = AsyncCommandManager.GetSerializationData(Engine, ItemID);
 
@@ -1106,6 +1115,7 @@ namespace OpenSim.Region.ScriptEngine.Shared.Instance
                     m_CurrentStateHash = hash;
                 }
             }
+        }
 
         public IScriptApi GetApi(string name)
         {

OpenSim/Region/ScriptEngine/XEngine/XEngine.cs

@@ -732,8 +732,7 @@ namespace OpenSim.Region.ScriptEngine.XEngine
 
                     // Clear the event queue and abort the instance thread
                     //
-                    instance.ClearQueue();
+                    instance.Stop(0, true);
-                    instance.Stop(0);
 
                     // Release events, timer, etc
                     //
@@ -859,8 +858,6 @@ namespace OpenSim.Region.ScriptEngine.XEngine
                 }
             }
 
-            instances.Clear();
-
             if (saveTime > 0)
                 m_ThreadPool.QueueWorkItem(new WorkItemCallback(this.DoBackup),
                                            new Object[] { saveTime });
@@ -1443,6 +1440,7 @@ namespace OpenSim.Region.ScriptEngine.XEngine
                 m_Scripts.Remove(itemID);
             }
 
+
             instance.ClearQueue();
 
             instance.Stop(m_WaitForEventCompletionOnScriptStop);