Merge branch 'master' of git://opensimulator.org/git/opensim

10 files changed, 188 insertions, 114 deletions

diff --git a/OpenSim/Framework/BlockingQueue.cs b/OpenSim/Framework/BlockingQueue.cs
index aef1192..3e90fac 100644
--- a/OpenSim/Framework/BlockingQueue.cs
+++ b/OpenSim/Framework/BlockingQueue.cs
@@ -76,9 +76,10 @@ namespace OpenSim.Framework
         {
             lock (m_queueSync)
             {
-                if (m_queue.Count < 1 && m_pqueue.Count < 1)
+                bool success = true;
+                while (m_queue.Count < 1 && m_pqueue.Count < 1 && success)
                 {
-                    Monitor.Wait(m_queueSync, msTimeout);
+                    success = Monitor.Wait(m_queueSync, msTimeout);
                 }
 
                 if (m_pqueue.Count > 0)
diff --git a/OpenSim/Framework/Servers/HttpServer/PollServiceEventArgs.cs b/OpenSim/Framework/Servers/HttpServer/PollServiceEventArgs.cs
index 020bfd5..9477100 100644
--- a/OpenSim/Framework/Servers/HttpServer/PollServiceEventArgs.cs
+++ b/OpenSim/Framework/Servers/HttpServer/PollServiceEventArgs.cs
@@ -50,7 +50,7 @@ namespace OpenSim.Framework.Servers.HttpServer
 
         public enum EventType : int
         {
-            Normal = 0,
+            LongPoll = 0,
             LslHttp = 1,
             Inventory = 2
         }
@@ -80,7 +80,7 @@ namespace OpenSim.Framework.Servers.HttpServer
             NoEvents = pNoEvents;
             Id = pId;
             TimeOutms = pTimeOutms;
-            Type = EventType.Normal;
+            Type = EventType.LongPoll;
         }
     }
 }
diff --git a/OpenSim/Framework/Servers/HttpServer/PollServiceRequestManager.cs b/OpenSim/Framework/Servers/HttpServer/PollServiceRequestManager.cs
index 1b9010a..b8f5743 100644
--- a/OpenSim/Framework/Servers/HttpServer/PollServiceRequestManager.cs
+++ b/OpenSim/Framework/Servers/HttpServer/PollServiceRequestManager.cs
@@ -47,12 +47,11 @@ namespace OpenSim.Framework.Servers.HttpServer
         private readonly BaseHttpServer m_server;
 
         private BlockingQueue<PollServiceHttpRequest> m_requests = new BlockingQueue<PollServiceHttpRequest>();
-        private static Queue<PollServiceHttpRequest> m_slowRequests = new Queue<PollServiceHttpRequest>();
-        private static Queue<PollServiceHttpRequest> m_retryRequests = new Queue<PollServiceHttpRequest>();
+        private static Queue<PollServiceHttpRequest> m_longPollRequests = new Queue<PollServiceHttpRequest>();
 
         private uint m_WorkerThreadCount = 0;
         private Thread[] m_workerThreads;
-        private Thread m_retrysThread;
+        private Thread m_longPollThread;
 
         private bool m_running = true;
         private int slowCount = 0;
@@ -84,9 +83,9 @@ namespace OpenSim.Framework.Servers.HttpServer
                         int.MaxValue);
             }
 
-            m_retrysThread = Watchdog.StartThread(
-                this.CheckRetries,
-                string.Format("PollServiceWatcherThread:{0}", m_server.Port),
+            m_longPollThread = Watchdog.StartThread(
+                this.CheckLongPollThreads,
+                string.Format("LongPollServiceWatcherThread:{0}", m_server.Port),
                 ThreadPriority.Normal,
                 false,
                 true,
@@ -97,49 +96,52 @@ namespace OpenSim.Framework.Servers.HttpServer
         private void ReQueueEvent(PollServiceHttpRequest req)
         {
             if (m_running)
-            {
-                lock (m_retryRequests)
-                    m_retryRequests.Enqueue(req);
-            }
+                m_requests.Enqueue(req);
         }
 
         public void Enqueue(PollServiceHttpRequest req)
         {
             if (m_running)
             {
-                if (req.PollServiceArgs.Type != PollServiceEventArgs.EventType.Normal)
+                if (req.PollServiceArgs.Type == PollServiceEventArgs.EventType.LongPoll)
                 {
-                    m_requests.Enqueue(req);
+                    lock (m_longPollRequests)
+                        m_longPollRequests.Enqueue(req);
                 }
                 else
-                {
-                    lock (m_slowRequests)
-                        m_slowRequests.Enqueue(req);
-                }
+                    m_requests.Enqueue(req);
             }
         }
 
-        private void CheckRetries()
+        private void CheckLongPollThreads()
         {
+            // The only purpose of this thread is to check the EQs for events.
+            // If there are events, that thread will be placed in the "ready-to-serve" queue, m_requests.
+            // If there are no events, that thread will be back to its "waiting" queue, m_longPollRequests.
+            // All other types of tasks (Inventory handlers) don't have the long-poll nature,
+            // so if they aren't ready to be served by a worker thread (no events), they are placed 
+            // directly back in the "ready-to-serve" queue by the worker thread.
             while (m_running)
             {
-                Thread.Sleep(100); // let the world move  .. back to faster rate
+                Thread.Sleep(1000); 
                 Watchdog.UpdateThread();
-                lock (m_retryRequests)
-                {
-                    while (m_retryRequests.Count > 0 && m_running)
-                        m_requests.Enqueue(m_retryRequests.Dequeue());
-                }
-                slowCount++;
-                if (slowCount >= 10)
-                {
-                    slowCount = 0;
 
-                    lock (m_slowRequests)
+                List<PollServiceHttpRequest> not_ready = new List<PollServiceHttpRequest>();
+                lock (m_longPollRequests)
+                {
+                    while (m_longPollRequests.Count > 0 && m_running)
                     {
-                        while (m_slowRequests.Count > 0 && m_running)
-                            m_requests.Enqueue(m_slowRequests.Dequeue());
+                        PollServiceHttpRequest req = m_longPollRequests.Dequeue();
+                        if (req.PollServiceArgs.HasEvents(req.RequestID, req.PollServiceArgs.Id) || // there are events in this EQ
+                            (Environment.TickCount - req.RequestTime) > req.PollServiceArgs.TimeOutms) // no events, but timeout
+                            m_requests.Enqueue(req);
+                        else
+                            not_ready.Add(req);
                     }
+
+                    foreach (PollServiceHttpRequest req in not_ready)
+                        m_longPollRequests.Enqueue(req);
+
                 }
             }
         }
@@ -153,24 +155,12 @@ namespace OpenSim.Framework.Servers.HttpServer
             foreach (Thread t in m_workerThreads)
                 Watchdog.AbortThread(t.ManagedThreadId);
 
-            try
-            {
-                foreach (PollServiceHttpRequest req in m_retryRequests)
-                {
-                   req.DoHTTPGruntWork(m_server, req.PollServiceArgs.NoEvents(req.RequestID, req.PollServiceArgs.Id));
-                }
-            }
-            catch
-            {
-            }
-
             PollServiceHttpRequest wreq;
-            m_retryRequests.Clear();
 
-            lock (m_slowRequests)
+            lock (m_longPollRequests)
             {
-                while (m_slowRequests.Count > 0 && m_running)
-                    m_requests.Enqueue(m_slowRequests.Dequeue());
+                while (m_longPollRequests.Count > 0 && m_running)
+                    m_requests.Enqueue(m_longPollRequests.Dequeue());
             }
 
             while (m_requests.Count() > 0)
@@ -195,34 +185,33 @@ namespace OpenSim.Framework.Servers.HttpServer
         {
             while (m_running)
             {
-                PollServiceHttpRequest req = m_requests.Dequeue(5000);
-
                 Watchdog.UpdateThread();
-                if (req != null)
+
+                PollServiceHttpRequest req = null;
+                lock (m_requests)
+                {
+                    if (m_requests.Count() > 0)
+                        req = m_requests.Dequeue();
+                }
+                if (req == null)
+                    Thread.Sleep(100);
+                else
                 {
-                    try
+                    //PollServiceHttpRequest req = m_requests.Dequeue(5000);
+                    //m_log.WarnFormat("[YYY]: Dequeued {0}", (req == null ? "null" : req.PollServiceArgs.Type.ToString()));
+
+                    if (req != null)
                     {
-                        if (req.PollServiceArgs.HasEvents(req.RequestID, req.PollServiceArgs.Id))
+                        try
                         {
-                            Hashtable responsedata = req.PollServiceArgs.GetEvents(req.RequestID, req.PollServiceArgs.Id);
+                            if (req.PollServiceArgs.HasEvents(req.RequestID, req.PollServiceArgs.Id))
+                            {
+                                Hashtable responsedata = req.PollServiceArgs.GetEvents(req.RequestID, req.PollServiceArgs.Id);
 
-                            if (responsedata == null)
-                                continue;
+                                if (responsedata == null)
+                                    continue;
 
-                            if (req.PollServiceArgs.Type == PollServiceEventArgs.EventType.Normal) // This is the event queue
-                            {
-                                try
-                                {
-                                    req.DoHTTPGruntWork(m_server, responsedata);
-                                }
-                                catch (ObjectDisposedException) // Browser aborted before we could read body, server closed the stream
-                                {
-                                    // Ignore it, no need to reply
-                                }
-                            }
-                            else
-                            {
-                                m_threadPool.QueueWorkItem(x =>
+                                if (req.PollServiceArgs.Type == PollServiceEventArgs.EventType.LongPoll) // This is the event queue
                                 {
                                     try
                                     {
@@ -232,27 +221,41 @@ namespace OpenSim.Framework.Servers.HttpServer
                                     {
                                         // Ignore it, no need to reply
                                     }
+                                }
+                                else
+                                {
+                                    m_threadPool.QueueWorkItem(x =>
+                                    {
+                                        try
+                                        {
+                                            req.DoHTTPGruntWork(m_server, responsedata);
+                                        }
+                                        catch (ObjectDisposedException) // Browser aborted before we could read body, server closed the stream
+                                        {
+                                            // Ignore it, no need to reply
+                                        }
 
-                                    return null;
-                                }, null);
-                            }
-                        }
-                        else
-                        {
-                            if ((Environment.TickCount - req.RequestTime) > req.PollServiceArgs.TimeOutms)
-                            {
-                                req.DoHTTPGruntWork(
-                                    m_server, req.PollServiceArgs.NoEvents(req.RequestID, req.PollServiceArgs.Id));
+                                        return null;
+                                    }, null);
+                                }
                             }
                             else
                             {
-                                ReQueueEvent(req);
+                                if ((Environment.TickCount - req.RequestTime) > req.PollServiceArgs.TimeOutms)
+                                {
+                                    req.DoHTTPGruntWork(
+                                        m_server, req.PollServiceArgs.NoEvents(req.RequestID, req.PollServiceArgs.Id));
+                                }
+                                else
+                                {
+                                    ReQueueEvent(req);
+                                }
                             }
                         }
-                    }
-                    catch (Exception e)
-                    {
-                        m_log.ErrorFormat("Exception in poll service thread: " + e.ToString());
+                        catch (Exception e)
+                        {
+                            m_log.ErrorFormat("Exception in poll service thread: " + e.ToString());
+                        }
                     }
                 }
             }
diff --git a/OpenSim/Region/ClientStack/Linden/Caps/EventQueue/EventQueueGetModule.cs b/OpenSim/Region/ClientStack/Linden/Caps/EventQueue/EventQueueGetModule.cs
index 1835a72..f0445ff 100644
--- a/OpenSim/Region/ClientStack/Linden/Caps/EventQueue/EventQueueGetModule.cs
+++ b/OpenSim/Region/ClientStack/Linden/Caps/EventQueue/EventQueueGetModule.cs
@@ -364,8 +364,7 @@ namespace OpenSim.Region.ClientStack.Linden
 
             caps.RegisterPollHandler(
                 "EventQueueGet", 
-                new PollServiceEventArgs(
-                    null, GenerateEqgCapPath(eventQueueGetUUID), HasEvents, GetEvents, NoEvents, agentID, 40000));
+                new PollServiceEventArgs(null, GenerateEqgCapPath(eventQueueGetUUID), HasEvents, GetEvents, NoEvents, agentID, 40000));
 
             Random rnd = new Random(Environment.TickCount);
             lock (m_ids)
@@ -383,7 +382,10 @@ namespace OpenSim.Region.ClientStack.Linden
             Queue<OSD> queue = GetQueue(agentID);
             if (queue != null)
                 lock (queue)
+                {
+                    //m_log.WarnFormat("POLLED FOR EVENTS BY {0} in {1} -- {2}", agentID, m_scene.RegionInfo.RegionName, queue.Count);
                     return queue.Count > 0;
+                }
 
             return false;
         }
@@ -406,7 +408,7 @@ namespace OpenSim.Region.ClientStack.Linden
         public Hashtable GetEvents(UUID requestID, UUID pAgentId)
         {
             if (DebugLevel >= 2)
-                m_log.DebugFormat("POLLED FOR EQ MESSAGES BY {0} in {1}", pAgentId, m_scene.RegionInfo.RegionName);
+                m_log.WarnFormat("POLLED FOR EQ MESSAGES BY {0} in {1}", pAgentId, m_scene.RegionInfo.RegionName);
 
             Queue<OSD> queue = TryGetQueue(pAgentId);
             OSD element;
diff --git a/OpenSim/Region/CoreModules/Framework/ServiceThrottle/ServiceThrottleModule.cs b/OpenSim/Region/CoreModules/Framework/ServiceThrottle/ServiceThrottleModule.cs
index 553e4ca..a70261e 100644
--- a/OpenSim/Region/CoreModules/Framework/ServiceThrottle/ServiceThrottleModule.cs
+++ b/OpenSim/Region/CoreModules/Framework/ServiceThrottle/ServiceThrottleModule.cs
@@ -50,15 +50,16 @@ namespace OpenSim.Region.CoreModules.Framework
         private readonly List<Scene> m_scenes = new List<Scene>();
         private System.Timers.Timer m_timer = new System.Timers.Timer();
 
-        //private OpenSim.Framework.BlockingQueue<GridRegionRequest> m_RequestQueue = new OpenSim.Framework.BlockingQueue<GridRegionRequest>();
-        // private OpenSim.Framework.DoubleQueue<GridRegionRequest> m_RequestQueue = new OpenSim.Framework.DoubleQueue<GridRegionRequest>();
-        //private Queue<GridRegionRequest> m_RequestQueue = new Queue<GridRegionRequest>();
         private Queue<Action> m_RequestQueue = new Queue<Action>();
+        private Dictionary<string, List<string>> m_Pending = new Dictionary<string, List<string>>();
+        private int m_Interval;
 
         #region ISharedRegionModule
 
         public void Initialise(IConfigSource config)
         {
+            m_Interval = Util.GetConfigVarFromSections<int>(config, "Interval", new string[] { "ServiceThrottle" }, 5000);
+
             m_timer = new System.Timers.Timer();
             m_timer.AutoReset = false;
             m_timer.Enabled = true;
@@ -131,7 +132,7 @@ namespace OpenSim.Region.CoreModules.Framework
             {
                 if (!m_timer.Enabled)
                 {
-                    m_timer.Interval = 1000;
+                    m_timer.Interval = m_Interval;
                     m_timer.Enabled = true;
                     m_timer.Start();
                 }
@@ -156,18 +157,36 @@ namespace OpenSim.Region.CoreModules.Framework
                     client.SendRegionHandle(regionID, r.RegionHandle);
             };
 
-            lock (m_RequestQueue)
-                m_RequestQueue.Enqueue(action);
-
+            Enqueue("region", regionID.ToString(), action);
         }
 
         #endregion Events
 
         #region IServiceThrottleModule
 
-        public void Enqueue(Action continuation)
+        public void Enqueue(string category, string itemid, Action continuation)
         {
-            m_RequestQueue.Enqueue(continuation);
+            lock (m_RequestQueue)
+            {
+                if (m_Pending.ContainsKey(category))
+                {
+                    if (m_Pending[category].Contains(itemid))
+                        // Don't enqueue, it's already pending
+                        return;
+                }
+                else
+                    m_Pending.Add(category, new List<string>());
+
+                m_Pending[category].Add(itemid);
+
+                m_RequestQueue.Enqueue(delegate
+                {
+                    lock (m_RequestQueue)
+                        m_Pending[category].Remove(itemid);
+
+                    continuation();
+                });
+            }
         }
 
         #endregion IServiceThrottleModule
diff --git a/OpenSim/Region/CoreModules/Framework/UserManagement/UserManagementModule.cs b/OpenSim/Region/CoreModules/Framework/UserManagement/UserManagementModule.cs
index da28a53..a91adfa 100644
--- a/OpenSim/Region/CoreModules/Framework/UserManagement/UserManagementModule.cs
+++ b/OpenSim/Region/CoreModules/Framework/UserManagement/UserManagementModule.cs
@@ -172,11 +172,11 @@ namespace OpenSim.Region.CoreModules.Framework.UserManagement
                     return;
                 }
 
-                // Not found in cache, get it from services
-                m_ServiceThrottle.Enqueue(delegate
+                // Not found in cache, queue continuation
+                m_ServiceThrottle.Enqueue("name", uuid.ToString(),  delegate
                 {
                     //m_log.DebugFormat("[YYY]: Name request {0}", uuid);
-                    bool foundRealName = TryGetUserNamesFromServices(uuid, names);
+                    bool foundRealName = TryGetUserNames(uuid, names);
 
                     if (names.Length == 2)
                     {
diff --git a/OpenSim/Region/CoreModules/World/WorldMap/WorldMapModule.cs b/OpenSim/Region/CoreModules/World/WorldMap/WorldMapModule.cs
index c50ab64..a26a5f0 100644
--- a/OpenSim/Region/CoreModules/World/WorldMap/WorldMapModule.cs
+++ b/OpenSim/Region/CoreModules/World/WorldMap/WorldMapModule.cs
@@ -81,6 +81,8 @@ namespace OpenSim.Region.CoreModules.World.WorldMap
         private List<UUID> m_rootAgents = new List<UUID>();
         private volatile bool threadrunning = false;
 
+        private IServiceThrottleModule m_ServiceThrottle;
+
         //private int CacheRegionsDistance = 256;
 
         #region INonSharedRegionModule Members
@@ -131,6 +133,10 @@ namespace OpenSim.Region.CoreModules.World.WorldMap
 
         public virtual void RegionLoaded (Scene scene)
         {
+            if (!m_Enabled)
+                return;
+
+            m_ServiceThrottle = scene.RequestModuleInterface<IServiceThrottleModule>();
         }
 
 
@@ -170,13 +176,13 @@ namespace OpenSim.Region.CoreModules.World.WorldMap
             m_scene.EventManager.OnMakeRootAgent += MakeRootAgent;
             m_scene.EventManager.OnRegionUp += OnRegionUp;
 
-            StartThread(new object());
+//            StartThread(new object());
         }
 
         // this has to be called with a lock on m_scene
         protected virtual void RemoveHandlers()
         {
-            StopThread();
+//            StopThread();
 
             m_scene.EventManager.OnRegionUp -= OnRegionUp;
             m_scene.EventManager.OnMakeRootAgent -= MakeRootAgent;
@@ -526,7 +532,7 @@ namespace OpenSim.Region.CoreModules.World.WorldMap
         /// </summary>
         public void process()
         {
-            const int MAX_ASYNC_REQUESTS = 20;
+            //const int MAX_ASYNC_REQUESTS = 20;
             try
             {
                 while (true)
@@ -571,13 +577,44 @@ namespace OpenSim.Region.CoreModules.World.WorldMap
             Watchdog.RemoveThread();
         }
 
+        const int MAX_ASYNC_REQUESTS = 20;
+
         /// <summary>
-        /// Enqueues the map item request into the processing thread
+        /// Enqueues the map item request into the services throttle processing thread
         /// </summary>
         /// <param name="state"></param>
-        public void EnqueueMapItemRequest(MapRequestState state)
+        public void EnqueueMapItemRequest(MapRequestState st)
         {
-            requests.Enqueue(state);
+
+            m_ServiceThrottle.Enqueue("map-item", st.regionhandle.ToString() + st.agentID.ToString(), delegate
+            {
+                if (st.agentID != UUID.Zero)
+                {
+                    bool dorequest = true;
+                    lock (m_rootAgents)
+                    {
+                        if (!m_rootAgents.Contains(st.agentID))
+                            dorequest = false;
+                    }
+
+                    if (dorequest && !m_blacklistedregions.ContainsKey(st.regionhandle))
+                    {
+                        if (nAsyncRequests >= MAX_ASYNC_REQUESTS) // hit the break
+                        {
+                            // AH!!! Recursive !
+                            // Put this request back in the queue and return
+                            EnqueueMapItemRequest(st);
+                            return;
+                        }
+
+                        RequestMapItemsDelegate d = RequestMapItemsAsync;
+                        d.BeginInvoke(st.agentID, st.flags, st.EstateID, st.godlike, st.itemtype, st.regionhandle, RequestMapItemsCompleted, null);
+                        //OSDMap response = RequestMapItemsAsync(st.agentID, st.flags, st.EstateID, st.godlike, st.itemtype, st.regionhandle);
+                        //RequestMapItemsCompleted(response);
+                        Interlocked.Increment(ref nAsyncRequests);
+                    }
+                }
+            });
         }
 
         /// <summary>
diff --git a/OpenSim/Region/Framework/Interfaces/IServiceThrottleModule.cs b/OpenSim/Region/Framework/Interfaces/IServiceThrottleModule.cs
index bb6a8b4..198256f 100644
--- a/OpenSim/Region/Framework/Interfaces/IServiceThrottleModule.cs
+++ b/OpenSim/Region/Framework/Interfaces/IServiceThrottleModule.cs
@@ -5,7 +5,15 @@ namespace OpenSim.Region.Framework.Interfaces
 {
     public interface IServiceThrottleModule
     {
-        void Enqueue(Action continuation);
+        /// <summary>
+        /// Enqueue a continuation meant to get a resource from elsewhere.
+        /// As usual with CPS, caller beware: if that continuation is a never-ending computation,
+        /// the whole thread will be blocked, and no requests are processed
+        /// </summary>
+        /// <param name="category">Category of the resource (e.g. name, region)</param>
+        /// <param name="itemid">The resource identifier</param>
+        /// <param name="continuation">The continuation to be executed</param>
+        void Enqueue(string category, string itemid, Action continuation);
     }
 
 }
diff --git a/OpenSim/Region/Physics/BulletSPlugin/BSPhysObject.cs b/OpenSim/Region/Physics/BulletSPlugin/BSPhysObject.cs
index a41eaf8..fc4545f 100755
--- a/OpenSim/Region/Physics/BulletSPlugin/BSPhysObject.cs
+++ b/OpenSim/Region/Physics/BulletSPlugin/BSPhysObject.cs
@@ -103,9 +103,10 @@ public abstract class BSPhysObject : PhysicsActor
         CollisionsLastTickStep = -1;
 
         SubscribedEventsMs = 0;
-        CollidingStep = 0;
-        CollidingGroundStep = 0;
-        CollisionAccumulation = 0;
+        // Crazy values that will never be true
+        CollidingStep = BSScene.NotASimulationStep;
+        CollidingGroundStep = BSScene.NotASimulationStep;
+        CollisionAccumulation = BSScene.NotASimulationStep;
         ColliderIsMoving = false;
         CollisionScore = 0;
 
@@ -349,7 +350,7 @@ public abstract class BSPhysObject : PhysicsActor
             if (value)
                 CollidingStep = PhysScene.SimulationStep;
             else
-                CollidingStep = 0;
+                CollidingStep = BSScene.NotASimulationStep;
             }
     }
     public override bool CollidingGround {
@@ -359,7 +360,7 @@ public abstract class BSPhysObject : PhysicsActor
             if (value)
                 CollidingGroundStep = PhysScene.SimulationStep;
             else
-                CollidingGroundStep = 0;
+                CollidingGroundStep = BSScene.NotASimulationStep;
         }
     }
     public override bool CollidingObj {
@@ -368,7 +369,7 @@ public abstract class BSPhysObject : PhysicsActor
             if (value)
                 CollidingObjectStep = PhysScene.SimulationStep;
             else
-                CollidingObjectStep = 0;
+                CollidingObjectStep = BSScene.NotASimulationStep;
         }
     }
 
diff --git a/OpenSim/Region/Physics/BulletSPlugin/BSScene.cs b/OpenSim/Region/Physics/BulletSPlugin/BSScene.cs
index 214271b..41aca3b 100644
--- a/OpenSim/Region/Physics/BulletSPlugin/BSScene.cs
+++ b/OpenSim/Region/Physics/BulletSPlugin/BSScene.cs
@@ -97,6 +97,9 @@ public sealed class BSScene : PhysicsScene, IPhysicsParameters
 
     internal long m_simulationStep = 0; // The current simulation step.
     public long SimulationStep { get { return m_simulationStep; } }
+    // A number to use for SimulationStep that is probably not any step value
+    // Used by the collision code (which remembers the step when a collision happens) to remember not any simulation step.
+    public static long NotASimulationStep = -1234;
 
     internal float LastTimeStep { get; private set; }   // The simulation time from the last invocation of Simulate()