path: root/OpenSim/Region/ScriptEngine/XMREngine/XMRInstRun.cs

/*
 * Copyright (c) Contributors, http://opensimulator.org/
 * See CONTRIBUTORS.TXT for a full list of copyright holders.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *     * Neither the name of the OpenSimulator Project nor the
 *       names of its contributors may be used to endorse or promote products
 *       derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE CONTRIBUTORS BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

using System;
using System.Threading;
using System.Collections.Generic;
using System.Text;
using OpenMetaverse;
using OpenSim.Framework;
using OpenSim.Region.Framework.Interfaces;
using OpenSim.Region.ScriptEngine.Interfaces;
using OpenSim.Region.ScriptEngine.Shared;
using OpenSim.Region.ScriptEngine.Shared.Api;
using OpenSim.Region.ScriptEngine.Shared.ScriptBase;
using OpenSim.Region.ScriptEngine.XMREngine;
using OpenSim.Region.Framework.Scenes;
using log4net;

using LSL_Float = OpenSim.Region.ScriptEngine.Shared.LSL_Types.LSLFloat;
using LSL_Integer = OpenSim.Region.ScriptEngine.Shared.LSL_Types.LSLInteger;
using LSL_Key = OpenSim.Region.ScriptEngine.Shared.LSL_Types.LSLString;
using LSL_List = OpenSim.Region.ScriptEngine.Shared.LSL_Types.list;
using LSL_Rotation = OpenSim.Region.ScriptEngine.Shared.LSL_Types.Quaternion;
using LSL_String = OpenSim.Region.ScriptEngine.Shared.LSL_Types.LSLString;
using LSL_Vector = OpenSim.Region.ScriptEngine.Shared.LSL_Types.Vector3;

namespace OpenSim.Region.ScriptEngine.XMREngine
{
    public partial class XMRInstance
    {
        /************************************************************************************\
         * This module contains these externally useful methods:                            *
         *   PostEvent() - queues an event to script and wakes script thread to process it  *
         *   RunOne() - runs script for a time slice or until it volunteers to give up cpu  *
         *   CallSEH() - runs in the microthread to call the event handler                  *
        \************************************************************************************/

        /**
         * @brief This can be called in any thread (including the script thread itself)
         *        to queue event to script for processing.
         */
        public void PostEvent(EventParams evt)
        {
            ScriptEventCode evc = (ScriptEventCode)Enum.Parse (typeof (ScriptEventCode), 
                                                                 evt.EventName);

            /*
             * Put event on end of event queue.
             */
            bool startIt = false;
            bool wakeIt  = false;
            lock (m_QueueLock)
            {
                bool construct = (m_IState == XMRInstState.CONSTRUCT);

                /*
                 * Ignore event if we don't even have such an handler in any state.
                 * We can't be state-specific here because state might be different
                 * by the time this event is dequeued and delivered to the script.
                 */
                if (!construct &&                      // make sure m_HaveEventHandlers is filled in 
                    ((uint)evc < (uint)m_HaveEventHandlers.Length) &&
                    !m_HaveEventHandlers[(int)evc]) {  // don't bother if we don't have such a handler in any state
                    return;
                }

                /*
                 * Not running means we ignore any incoming events.
                 * But queue if still constructing because m_Running is not yet valid.
                 */
                if (!m_Running && !construct) {
                    return;
                }

                /*
                 * Only so many of each event type allowed to queue.
                 */
                if ((uint)evc < (uint)m_EventCounts.Length) {
                    int maxAllowed = MAXEVENTQUEUE;
                    if (evc == ScriptEventCode.timer) maxAllowed = 1;
                    if (m_EventCounts[(int)evc] >= maxAllowed)
                    {
                        return;
                    }
                    m_EventCounts[(int)evc] ++;
                }

                /*
                 * Put event on end of instance's event queue.
                 */
                LinkedListNode<EventParams> lln = new LinkedListNode<EventParams>(evt);
                switch (evc) {

                    /*
                     * These need to go first.  The only time we manually
                     * queue them is for the default state_entry() and we
                     * need to make sure they go before any attach() events
                     * so the heapLimit value gets properly initialized.
                     */
                    case ScriptEventCode.state_entry: {
                        m_EventQueue.AddFirst(lln);
                        break;
                    }

                    /*
                     * The attach event sneaks to the front of the queue.
                     * This is needed for quantum limiting to work because
                     * we want the attach(NULL_KEY) event to come in front
                     * of all others so the m_DetachQuantum won't run out
                     * before attach(NULL_KEY) is executed.
                     */
                    case ScriptEventCode.attach:
                    {
                        if (evt.Params[0].ToString() == UUID.Zero.ToString())
                        {
                            LinkedListNode<EventParams> lln2 = null;
                            for (lln2 = m_EventQueue.First; lln2 != null; lln2 = lln2.Next)
                            {
                                EventParams evt2 = lln2.Value;
                                ScriptEventCode evc2 = (ScriptEventCode)Enum.Parse (typeof (ScriptEventCode), 
                                                                         evt2.EventName);
                                if ((evc2 != ScriptEventCode.state_entry) &&
                                    (evc2 != ScriptEventCode.attach)) break;
                            }
                            if (lln2 == null)
                                m_EventQueue.AddLast(lln);
                            else
                                m_EventQueue.AddBefore(lln2, lln);
                            /* If we're detaching, limit the qantum. This will also
                             * cause the script to self-suspend after running this
                             * event
                             */

                            m_DetachReady.Reset();
                            m_DetachQuantum = 100;
                        }
                        else
                            m_EventQueue.AddLast(lln);
                        break;
                    }

                    /*
                     * All others just go on end in the order queued.
                     */
                    default:
                    {
                        m_EventQueue.AddLast(lln);
                        break;
                    }
                }

                /*
                 * If instance is idle (ie, not running or waiting to run),
                 * flag it to be on m_StartQueue as we are about to do so.
                 * Flag it now before unlocking so another thread won't try
                 * to do the same thing right now.
                 * Dont' flag it if it's still suspended!
                 */
                if ((m_IState == XMRInstState.IDLE) && !m_Suspended)
                {
                    m_IState = XMRInstState.ONSTARTQ;
                    startIt = true;
                }

                /*
                 * If instance is sleeping (ie, possibly in xmrEventDequeue),
                 * wake it up if event is in the mask.
                 */
                if ((m_SleepUntil > DateTime.UtcNow) && !m_Suspended)
                {
                    int evc1 = (int)evc;
                    int evc2 = evc1 - 32;
                    if ((((uint)evc1 < (uint)32) && (((m_SleepEventMask1 >> evc1) & 1) != 0)) ||
                        (((uint)evc2 < (uint)32) && (((m_SleepEventMask2 >> evc2) & 1) != 0)))
                    {
                        wakeIt = true;
                    }
                }
            }

            /*
             * If transitioned from IDLE->ONSTARTQ, actually go insert it
             * on m_StartQueue and give the RunScriptThread() a wake-up.
             */
            if (startIt)
                m_Engine.QueueToStart(this);

            /*
             * Likewise, if the event mask triggered a wake, wake it up.
             */
            if (wakeIt)
            {
                m_SleepUntil = DateTime.MinValue;
                m_Engine.WakeFromSleep(this);
            }
        }

        /*
         * This is called in the script thread to step script until it calls
         * CheckRun().  It returns what the instance's next state should be,
         * ONSLEEPQ, ONYIELDQ, SUSPENDED or FINISHED.
         */
        public XMRInstState RunOne()
        {
            DateTime now = DateTime.UtcNow;
            m_SliceStart = Util.GetTimeStampMS();

            /*
             * If script has called llSleep(), don't do any more until time is
             * up.
             */
            m_RunOnePhase = "check m_SleepUntil";
            if (m_SleepUntil > now)
            {
                m_RunOnePhase = "return is sleeping";
                return XMRInstState.ONSLEEPQ;
            }

            /*
             * Also, someone may have called Suspend().
             */
            m_RunOnePhase = "check m_SuspendCount";
            if (m_SuspendCount > 0)
            {
                m_RunOnePhase = "return is suspended";
                return XMRInstState.SUSPENDED;
            }

            /*
             * Make sure we aren't being migrated in or out and prevent that 
             * whilst we are in here.  If migration has it locked, don't call
             * back right away, delay a bit so we don't get in infinite loop.
             */
            m_RunOnePhase = "lock m_RunLock";
            if (!Monitor.TryEnter (m_RunLock))
            {
                m_SleepUntil = now.AddMilliseconds(3);
                m_RunOnePhase = "return was locked";
                return XMRInstState.ONSLEEPQ;
            }
            try
            {
                m_RunOnePhase = "check entry invariants";
                CheckRunLockInvariants(true);
                Exception e = null;

                /*
                 * Maybe we have been disposed.
                 */
                m_RunOnePhase = "check disposed";
                if (microthread == null)
                {
                    m_RunOnePhase = "return disposed";
                    return XMRInstState.DISPOSED;
                }

                /*
                 * Do some more of the last event if it didn't finish.
                 */
                else if (eventCode != ScriptEventCode.None)
                {
                    lock (m_QueueLock)
                    {
                        if (m_DetachQuantum > 0 && --m_DetachQuantum == 0)
                        {
                            m_Suspended = true;
                            m_DetachReady.Set();
                            m_RunOnePhase = "detach quantum went zero";
                            CheckRunLockInvariants(true);
                            return XMRInstState.FINISHED;
                        }
                    }

                    m_RunOnePhase = "resume old event handler";
                    m_LastRanAt   = now;
                    m_InstEHSlice ++;
                    callMode = CallMode_NORMAL;
                    e = microthread.ResumeEx ();
                }

                /*
                 * Otherwise, maybe we can dequeue a new event and start 
                 * processing it.
                 */
                else
                {
                    m_RunOnePhase = "lock event queue";
                    EventParams evt = null;
                    ScriptEventCode evc = ScriptEventCode.None;

                    lock (m_QueueLock)
                    {

                        /* We can't get here unless the script has been resumed
                         * after creation, then suspended again, and then had
                         * an event posted to it. We just pretend there is no
                         * event int he queue and let the normal mechanics
                         * carry out the suspension. A Resume will handle the
                         * restarting gracefully. This is taking the easy way
                         * out and may be improved in the future.
                         */

                        if (m_Suspended)
                        {
                            m_RunOnePhase = "m_Suspended is set";
                            CheckRunLockInvariants(true);
                            return XMRInstState.FINISHED;
                        }

                        m_RunOnePhase = "dequeue event";
                        if (m_EventQueue.First != null)
                        {
                            evt = m_EventQueue.First.Value;
                            evc = (ScriptEventCode)Enum.Parse (typeof (ScriptEventCode), 
                                                               evt.EventName);
                            if (m_DetachQuantum > 0)
                            {
                                if (evc != ScriptEventCode.attach)
                                {
                                    /*
                                     * This is the case where the attach event
                                     * has completed and another event is queued
                                     * Stop it from running and suspend
                                     */
                                    m_Suspended = true;
                                    m_DetachReady.Set();
                                    m_DetachQuantum = 0;
                                    m_RunOnePhase = "nothing to do #3";
                                    CheckRunLockInvariants(true);
                                    return XMRInstState.FINISHED;
                                }
                            }
                            m_EventQueue.RemoveFirst();
                            if (evc >= 0)
                                m_EventCounts[(int)evc] --;
                        }

                        /*
                         * If there is no event to dequeue, don't run this script
                         * until another event gets queued.
                         */
                        if (evt == null)
                        {
                            if (m_DetachQuantum > 0)
                            {
                                /*
                                 * This will happen if the attach event has run
                                 * and exited with time slice left.
                                 */
                                m_Suspended = true;
                                m_DetachReady.Set();
                                m_DetachQuantum = 0;
                            }
                            m_RunOnePhase = "nothing to do #4";
                            CheckRunLockInvariants(true);
                            return XMRInstState.FINISHED;
                        }
                    }

                    /*
                     * Dequeued an event, so start it going until it either 
                     * finishes or it calls CheckRun().
                     */
                    m_RunOnePhase  = "start event handler";
                    m_DetectParams = evt.DetectParams;
                    m_LastRanAt    = now;
                    m_InstEHEvent ++;
                    e = StartEventHandler (evc, evt.Params);
                }
                m_RunOnePhase = "done running";
                m_CPUTime    += DateTime.UtcNow.Subtract(now).TotalMilliseconds;

                /*
                 * Maybe it puqued.
                 */
                if (e != null)
                {
                    m_RunOnePhase = "handling exception " + e.Message;
                    HandleScriptException(e);
                    m_RunOnePhase = "return had exception " + e.Message;
                    CheckRunLockInvariants(true);
                    return XMRInstState.FINISHED;
                }

                /*
                 * If event handler completed, get rid of detect params.
                 */
                if (this.eventCode == ScriptEventCode.None)
                {
                    m_DetectParams = null;
                }
            }
            finally
            {
                m_RunOnePhase += "; checking exit invariants and unlocking";
                CheckRunLockInvariants(false);
                Monitor.Exit(m_RunLock);
            }

            /*
             * Cycle script through the yield queue and call it back asap.
             */
            m_RunOnePhase = "last return";
            return XMRInstState.ONYIELDQ;
        }

        /**
         * @brief Immediately after taking m_RunLock or just before releasing it, check invariants.
         */
        private ScriptEventCode lastEventCode = ScriptEventCode.None;
        private int             lastActive    = 0;
        private string          lastRunPhase  = "";

        public void CheckRunLockInvariants(bool throwIt)
        {
            /*
             * If not executing any event handler, active should be 0 indicating the microthread stack is not in use.
             * If executing an event handler, active should be -1 indicating stack is in use but suspended.
             */
            IScriptUThread uth = microthread;
            if (uth != null) {
                int active = uth.Active ();
                ScriptEventCode ec = this.eventCode;
                if (((ec == ScriptEventCode.None) && (active != 0)) ||
                    ((ec != ScriptEventCode.None) && (active >= 0))) {
                    Console.WriteLine("CheckRunLockInvariants: script=" + m_DescName);
                    Console.WriteLine("CheckRunLockInvariants: eventcode=" + ec.ToString() + ", active=" + active.ToString());
                    Console.WriteLine("CheckRunLockInvariants: m_RunOnePhase=" + m_RunOnePhase);
                    Console.WriteLine("CheckRunLockInvariants: lastec=" + lastEventCode + ", lastAct=" + lastActive + ", lastPhase=" + lastRunPhase);
                    if (throwIt) {
                        throw new Exception("CheckRunLockInvariants: eventcode=" + ec.ToString() + ", active=" + active.ToString());
                    }
                }
                lastEventCode = ec;
                lastActive    = active;
                lastRunPhase  = m_RunOnePhase;
            }
        }

        /*
         * Start event handler.
         *
         * Input:
         *  eventCode = code of event to be processed
         *  ehArgs    = arguments for the event handler
         *
         * Caution:
         *  It is up to the caller to make sure ehArgs[] is correct for
         *  the particular event handler being called.  The first thing
         *  a script event handler method does is to unmarshall the args
         *  from ehArgs[] and will throw an array bounds or cast exception 
         *  if it can't.
         */
        private Exception StartEventHandler (ScriptEventCode eventCode, object[] ehArgs)
        {
            /*
             * We use this.eventCode == ScriptEventCode.None to indicate we are idle.
             * So trying to execute ScriptEventCode.None might make a mess.
             */
            if (eventCode == ScriptEventCode.None)
                return new Exception ("Can't process ScriptEventCode.None");

            /*
             * Silly to even try if there is no handler defined for this event.
             */
            if ((eventCode >= 0) && (m_ObjCode.scriptEventHandlerTable[this.stateCode,(int)eventCode] == null))
                return null;

            /*
             * The microthread shouldn't be processing any event code.
             * These are assert checks so we throw them directly as exceptions.
             */
            if (this.eventCode != ScriptEventCode.None)
                throw new Exception ("still processing event " + this.eventCode.ToString ());

            int active = microthread.Active ();
            if (active != 0)
                throw new Exception ("microthread is active " + active.ToString ());

            /*
             * Save eventCode so we know what event handler to run in the microthread.
             * And it also marks us busy so we can't be started again and this event lost.
             */
            this.eventCode = eventCode;
            this.ehArgs    = ehArgs;

            /*
             * This calls ScriptUThread.Main() directly, and returns when Main() [indirectly]
             * calls Suspend() or when Main() returns, whichever occurs first.
             * Setting stackFrames = null means run the event handler from the beginning
             * without doing any stack frame restores first.
             */
            this.stackFrames = null;
            Exception e;
            e = microthread.StartEx ();
            return e;
        }


        /**
         * @brief There was an exception whilst starting/running a script event handler.
         *        Maybe we handle it directly or just print an error message.
         */
        private void HandleScriptException(Exception e)
        {
            /*
             * The script threw some kind of exception that was not caught at
             * script level, so the script is no longer running an event handler.
             */
            eventCode = ScriptEventCode.None;

            if (e is ScriptDeleteException)
            {
                /*
                 * Script did something like llRemoveInventory(llGetScriptName());
                 * ... to delete itself from the object.
                 */
                m_SleepUntil = DateTime.MaxValue;
                Verbose ("[XMREngine]: script self-delete {0}", m_ItemID);
                m_Part.Inventory.RemoveInventoryItem(m_ItemID);
            }
            else if (e is ScriptDieException)
            {
                /*
                 * Script did an llDie()
                 */
                m_RunOnePhase = "dying...";
                m_SleepUntil = DateTime.MaxValue;
                m_Engine.World.DeleteSceneObject(m_Part.ParentGroup, false);
            }
            else if (e is ScriptResetException)
            {
                /*
                 * Script did an llResetScript().
                 */
                m_RunOnePhase = "resetting...";
                ResetLocked("HandleScriptResetException");
            }
            else
            {
                /*
                 * Some general script error.
                 */
                SendErrorMessage(e);
            }
            return;
        }

        /**
         * @brief There was an exception running script event handler.
         *        Display error message and disable script (in a way
         *        that the script can be reset to be restarted).
         */
        private void SendErrorMessage(Exception e)
        {
            StringBuilder msg = new StringBuilder();

            msg.Append ("[XMREngine]: Exception while running ");
            msg.Append (m_ItemID);
            msg.Append ('\n');

            /*
             * Add exception message.
             */
            string des = e.Message;
            des = (des == null) ? "" : (": " + des);
            msg.Append (e.GetType ().Name + des + "\n");

            /*
             * Tell script owner what to do.
             */
            msg.Append ("Prim: <");
            msg.Append (m_Part.Name);
            msg.Append (">, Script: <");
            msg.Append (m_Item.Name);
            msg.Append (">, Location: ");
            msg.Append (m_Engine.World.RegionInfo.RegionName);
            msg.Append (" <");
            Vector3 pos = m_Part.AbsolutePosition;
            msg.Append ((int) Math.Floor (pos.X));
            msg.Append (',');
            msg.Append ((int) Math.Floor (pos.Y));
            msg.Append (',');
            msg.Append ((int) Math.Floor (pos.Z));
            msg.Append (">\nScript must be Reset to re-enable.\n");

            /*
             * Display full exception message in log.
             */
            m_log.Info (msg.ToString() + XMRExceptionStackString (e), e);

            /*
             * Give script owner the stack dump.
             */
            msg.Append (XMRExceptionStackString (e));

            /*
             * Send error message to owner.
             * Suppress internal code stack trace lines.
             */
            string msgst = msg.ToString();
            if (!msgst.EndsWith ("\n")) msgst += '\n';
            int j = 0;
            StringBuilder imstr = new StringBuilder ();
            for (int i = 0; (i = msgst.IndexOf ('\n', i)) >= 0; j = ++ i) {
                string line = msgst.Substring (j, i - j);
                if (line.StartsWith ("at ")) {
                    if (line.StartsWith ("at (wrapper")) continue;  // at (wrapper ...
                    int k = line.LastIndexOf (".cs:");  // ... .cs:linenumber
                    if (Int32.TryParse (line.Substring (k + 4), out k)) continue;
                }
                this.llOwnerSay (line);
                imstr.Append (line);
                imstr.Append ('\n');
            }

            /*
             * Send as instant message in case user not online.
             * Code modelled from llInstantMessage().
             */
            IMessageTransferModule transferModule = m_Engine.World.RequestModuleInterface<IMessageTransferModule>();
            if (transferModule != null) {
                UUID friendTransactionID = UUID.Random();
                GridInstantMessage gim = new GridInstantMessage();
                gim.fromAgentID = new Guid (m_Part.UUID.ToString());
                gim.toAgentID = new Guid (m_Part.OwnerID.ToString ());
                gim.imSessionID = new Guid(friendTransactionID.ToString());
                gim.timestamp = (uint)Util.UnixTimeSinceEpoch();
                gim.message = imstr.ToString ();
                gim.dialog = (byte)19; // messgage from script
                gim.fromGroup = false;
                gim.offline = (byte)0;
                gim.ParentEstateID = 0;
                gim.Position = pos;
                gim.RegionID = m_Engine.World.RegionInfo.RegionID.Guid;
                gim.binaryBucket = Util.StringToBytes256(
                    "{0}/{1}/{2}/{3}",
                    m_Engine.World.RegionInfo.RegionName,
                    (int)Math.Floor(pos.X),
                    (int)Math.Floor(pos.Y),
                    (int)Math.Floor(pos.Z));
                transferModule.SendInstantMessage(gim, delegate(bool success) {});
            }

            /*
             * Say script is sleeping for a very long time.
             * Reset() is able to cancel this sleeping.
             */
            m_SleepUntil = DateTime.MaxValue;
        }

        /**
         * @brief The user clicked the Reset Script button.
         *        We want to reset the script to a never-has-ever-run-before state.
         */
        public void Reset()
        {
        checkstate:
            XMRInstState iState = m_IState;
            switch (iState) {

                /*
                 * If it's really being constructed now, that's about as reset as we get.
                 */
                case XMRInstState.CONSTRUCT: {
                    return;
                }

                /*
                 * If it's idle, that means it is ready to receive a new event.
                 * So we lock the event queue to prevent another thread from taking
                 * it out of idle, verify that it is still in idle then transition
                 * it to resetting so no other thread will touch it.
                 */
                case XMRInstState.IDLE: {
                    lock (m_QueueLock) {
                        if (m_IState == XMRInstState.IDLE) {
                            m_IState = XMRInstState.RESETTING;
                            break;
                        }
                    }
                    goto checkstate;
                }

                /*
                 * If it's on the start queue, that means it is about to dequeue an
                 * event and start processing it.  So we lock the start queue so it
                 * can't be started and transition it to resetting so no other thread
                 * will touch it.
                 */
                case XMRInstState.ONSTARTQ: {
                    lock (m_Engine.m_StartQueue) {
                        if (m_IState == XMRInstState.ONSTARTQ) {
                            m_Engine.m_StartQueue.Remove(this);
                            m_IState = XMRInstState.RESETTING;
                            break;
                        }
                    }
                    goto checkstate;
                }

                /*
                 * If it's running, tell CheckRun() to suspend the thread then go back
                 * to see what it got transitioned to.
                 */
                case XMRInstState.RUNNING: {
                    suspendOnCheckRunHold = true;
                    lock (m_QueueLock) { }
                    goto checkstate;
                }

                /*
                 * If it's sleeping, remove it from sleep queue and transition it to
                 * resetting so no other thread will touch it.
                 */
                case XMRInstState.ONSLEEPQ: {
                    lock (m_Engine.m_SleepQueue) {
                        if (m_IState == XMRInstState.ONSLEEPQ) {
                            m_Engine.m_SleepQueue.Remove(this);
                            m_IState = XMRInstState.RESETTING;
                            break;
                        }
                    }
                    goto checkstate;
                }

                /*
                 * It was just removed from the sleep queue and is about to be put
                 * on the yield queue (ie, is being woken up).
                 * Let that thread complete transition and try again.
                 */
                case XMRInstState.REMDFROMSLPQ: {
                    Sleep (10);
                    goto checkstate;
                }

                /*
                 * If it's yielding, remove it from yield queue and transition it to
                 * resetting so no other thread will touch it.
                 */
                case XMRInstState.ONYIELDQ: {
                    lock (m_Engine.m_YieldQueue) {
                        if (m_IState == XMRInstState.ONYIELDQ) {
                            m_Engine.m_YieldQueue.Remove(this);
                            m_IState = XMRInstState.RESETTING;
                            break;
                        }
                    }
                    goto checkstate;
                }

                /*
                 * If it just finished running something, let that thread transition it
                 * to its next state then check again.
                 */
                case XMRInstState.FINISHED: {
                    Sleep (10);
                    goto checkstate;
                }

                /*
                 * If it's disposed, that's about as reset as it gets.
                 */
                case XMRInstState.DISPOSED: {
                    return;
                }

                /*
                 * Some other thread is already resetting it, let it finish.
                 */
                case XMRInstState.RESETTING: {
                    return;
                }

                default: throw new Exception("bad state");
            }

            /*
             * This thread transitioned the instance to RESETTING so reset it.
             */
            lock (m_RunLock) {
                CheckRunLockInvariants(true);

                /*
                 * No other thread should have transitioned it from RESETTING.
                 */
                if (m_IState != XMRInstState.RESETTING) throw new Exception("bad state");

                /*
                 * If the microthread is active, that means it has call frame
                 * context that we don't want.  Throw it out and get a fresh one.
                 */
                if (microthread.Active () < 0) {
                    microthread.Dispose ();
                    microthread = (IScriptUThread)m_Engine.uThreadCtor.Invoke (new object[] { this });
                }

                /*
                 * Mark it idle now so it can get queued to process new stuff.
                 */
                m_IState = XMRInstState.IDLE;

                /*
                 * Reset everything and queue up default's start_entry() event.
                 */
                ClearQueue();
                ResetLocked("external Reset");

                CheckRunLockInvariants(true);
            }
        }

        private void ClearQueueExceptLinkMessages()
        {
            lock (m_QueueLock) {
                EventParams[] linkMessages = new EventParams[m_EventQueue.Count];
                int n = 0;
                foreach (EventParams evt2 in m_EventQueue) {
                    if (evt2.EventName == "link_message") {
                        linkMessages[n++] = evt2;
                    }
                }

                m_EventQueue.Clear();
                for (int i = m_EventCounts.Length; -- i >= 0;) m_EventCounts[i] = 0;

                for (int i = 0; i < n; i ++) {
                    m_EventQueue.AddLast(linkMessages[i]);
                }

                m_EventCounts[(int)ScriptEventCode.link_message] = n;
            }
        }

        private void ClearQueue()
        {
            lock (m_QueueLock)
            {
                m_EventQueue.Clear();               // no events queued
                for (int i = m_EventCounts.Length; -- i >= 0;) m_EventCounts[i] = 0;
            }
        }

        /**
         * @brief The script called llResetScript() while it was running and
         *        has suspended.  We want to reset the script to a never-has-
         *        ever-run-before state.
         *
         *        Caller must have m_RunLock locked so we know script isn't
         *        running.
         */
        private void ResetLocked(string from)
        {
            m_RunOnePhase = "ResetLocked: releasing controls";
            ReleaseControls();

            m_RunOnePhase = "ResetLocked: removing script";
            m_Part.Inventory.GetInventoryItem(m_ItemID).PermsMask = 0;
            m_Part.Inventory.GetInventoryItem(m_ItemID).PermsGranter = UUID.Zero;
            IUrlModule urlModule = m_Engine.World.RequestModuleInterface<IUrlModule>();
            if (urlModule != null)
                urlModule.ScriptRemoved(m_ItemID);

            AsyncCommandManager.RemoveScript(m_Engine, m_LocalID, m_ItemID);

            m_RunOnePhase = "ResetLocked: clearing current event";
            this.eventCode = ScriptEventCode.None;  // not processing an event
            m_DetectParams = null;                  // not processing an event
            m_SleepUntil   = DateTime.MinValue;     // not doing llSleep()
            m_ResetCount ++;                        // has been reset once more

            /*
             * Tell next call to 'default state_entry()' to reset all global
             * vars to their initial values.
             */
            doGblInit = true;

            /*
             * Set script to 'default' state and queue call to its 
             * 'state_entry()' event handler.
             */
            m_RunOnePhase = "ResetLocked: posting default:state_entry() event";
            stateCode = 0;
            m_Part.SetScriptEvents(m_ItemID, GetStateEventFlags(0));
            PostEvent(new EventParams("state_entry", 
                                      zeroObjectArray, 
                                      zeroDetectParams));

            /*
             * Tell CheckRun() to let script run.
             */
            suspendOnCheckRunHold = false;
            suspendOnCheckRunTemp = false;
            m_RunOnePhase = "ResetLocked: reset complete";
        }

        private void ReleaseControls()
        {
            if (m_Part != null)
            {
                bool found;
                int permsMask;
                UUID permsGranter;

                try {
                    permsGranter = m_Part.TaskInventory[m_ItemID].PermsGranter;
                    permsMask = m_Part.TaskInventory[m_ItemID].PermsMask;
                    found = true;
                } catch {
                    permsGranter = UUID.Zero;
                    permsMask = 0;
                    found = false;
                }

                if (found && ((permsMask & ScriptBaseClass.PERMISSION_TAKE_CONTROLS) != 0)) {
                    ScenePresence presence = m_Engine.World.GetScenePresence(permsGranter);
                    if (presence != null) {
                        presence.UnRegisterControlEventsToScript(m_LocalID, m_ItemID);
                    }
                }
            }
        }

        /**
         * @brief The script code should call this routine whenever it is
         *        convenient to perform a migation or switch microthreads.
         */
        public override void CheckRunWork ()
        {
            if(!suspendOnCheckRunHold && ! suspendOnCheckRunTemp)
            {
                if(Util.GetTimeStampMS() - m_SliceStart < 60.0)
                    return;
                suspendOnCheckRunTemp = true;
            }

            m_CheckRunPhase = "entered";

            /*
             * Stay stuck in this loop as long as something wants us suspended.
             */
            while (suspendOnCheckRunHold || suspendOnCheckRunTemp)
            {
                m_CheckRunPhase = "top of while";

                /*
                 * See if MigrateOutEventHandler() has been called.
                 * If so, dump our stack to stackFrames and unwind.
                 */
                if (this.captureStackFrames)
                {

                    /*
                     * Puque our stack to the output stream.
                     * But otherwise, our state remains intact.
                     */
                    m_CheckRunPhase = "saving";
                    this.callMode = CallMode_SAVE;
                    this.stackFrames = null;
                    throw new StackCaptureException ();
                }

                /*
                 * We get here when the script state has been read in by MigrateInEventHandler().
                 * Since the stack is completely restored at this point, any subsequent calls
                 * within the functions should do their normal processing instead of trying to 
                 * restore their state.
                 */
                if (this.callMode == CallMode_RESTORE)
                {
                    stackFramesRestored = true;
                    this.callMode = CallMode_NORMAL;
                }

                /*
                 * Now we are ready to suspend the microthread.
                 * This is like a longjmp() to the most recent StartEx() or ResumeEx()
                 * with a simultaneous setjmp() so ResumeEx() can longjmp() back here.
                 */
                m_CheckRunPhase = "suspending";
                suspendOnCheckRunTemp = false;
                microthread.Hiber ();
                m_CheckRunPhase = "resumed";
            }

            m_CheckRunPhase = "returning";

            /*
             * Upon return from CheckRun() it should always be the case that the script is
             * going to process calls normally, neither saving nor restoring stack frame state.
             */
            if (callMode != CallMode_NORMAL) throw new Exception ("bad callMode " + callMode);
        }

        /**
         * @brief Allow script to dequeue events.
         */
        public void ResumeIt()
        {
            lock (m_QueueLock)
            {
                m_Suspended = false;
                if ((m_EventQueue != null) &&
                    (m_EventQueue.First != null) &&
                    (m_IState == XMRInstState.IDLE)) {
                    m_IState = XMRInstState.ONSTARTQ;
                    m_Engine.QueueToStart(this);
                }
                m_HasRun = true;
            }
        }

        /**
         * @brief Block script from dequeuing events.
         */
        public void SuspendIt()
        {
            lock (m_QueueLock)
            {
                m_Suspended = true;
            }
        }
    }

    /**
     * @brief Thrown by CheckRun() to unwind the script stack, capturing frames to
     *        instance.stackFrames as it unwinds.  We don't want scripts to be able
     *        to intercept this exception as it would block the stack capture
     *        functionality.
     */
    public class StackCaptureException : Exception, IXMRUncatchable { }
}