From 7410924de0b3adf3f93e0e661d99f4ab033680b9 Mon Sep 17 00:00:00 2001
From: Justin Clark-Casey (justincc)
Date: Thu, 12 Mar 2015 00:07:01 +0000
Subject: Lock around EventQueue manipulation in ScriptInstance.SetState() as
 queues are not thread-safe structures.

This should also make it less likely that an event will be erroneously posted during a state change by precluding a race condition with a thread calling ScriptInstance.PostEvent()
---
 .../ScriptEngine/Shared/Instance/ScriptInstance.cs | 41 +++++++++++++---------
 1 file changed, 24 insertions(+), 17 deletions(-)

(limited to 'OpenSim/Region/ScriptEngine/Shared/Instance')

diff --git a/OpenSim/Region/ScriptEngine/Shared/Instance/ScriptInstance.cs b/OpenSim/Region/ScriptEngine/Shared/Instance/ScriptInstance.cs
index 7c7b831..fe711d9 100644
--- a/OpenSim/Region/ScriptEngine/Shared/Instance/ScriptInstance.cs
+++ b/OpenSim/Region/ScriptEngine/Shared/Instance/ScriptInstance.cs
@@ -618,26 +618,33 @@ namespace OpenSim.Region.ScriptEngine.Shared.Instance
         {
             if (state == State)
                 return;
-            
-            // Remove all queued events, remembering the last timer event
+
             EventParams lastTimerEv = null;
-            while (EventQueue.Count > 0)
+
+            lock (EventQueue)
             {
-                EventParams tempv = (EventParams)EventQueue.Dequeue();
-                if (tempv.EventName == "timer") lastTimerEv = tempv;
+                // Remove all queued events, remembering the last timer event
+                while (EventQueue.Count > 0)
+                {
+                    EventParams tempv = (EventParams)EventQueue.Dequeue();
+                    if (tempv.EventName == "timer") lastTimerEv = tempv;
+                }
+
+                // Post events
+                PostEvent(new EventParams("state_exit", new Object[0],
+                                           new DetectParams[0]));
+                PostEvent(new EventParams("state", new Object[] { state },
+                                           new DetectParams[0]));
+                PostEvent(new EventParams("state_entry", new Object[0],
+                                           new DetectParams[0]));
+
+                // Requeue the timer event after the state changing events
+                if (lastTimerEv != null) EventQueue.Enqueue(lastTimerEv);
+
+                // This will stop events from being queued and processed
+                // until the new state is started
+                m_StateChangeInProgress = true;
             }
-            // Post events
-            PostEvent(new EventParams("state_exit", new Object[0],
-                                       new DetectParams[0]));
-            PostEvent(new EventParams("state", new Object[] { state },
-                                       new DetectParams[0]));
-            PostEvent(new EventParams("state_entry", new Object[0],
-                                       new DetectParams[0]));
-            // Requeue the timer event after the state changing events
-            if (lastTimerEv != null) EventQueue.Enqueue(lastTimerEv);
-            // This will stop events from being queued and processed
-            // until the new state is started
-            m_StateChangeInProgress = true;
 
             throw new EventAbortException();
         }
-- 
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