SSIS hang with unhandle exception

 bool isreuse = false;
        List<Thread> _listworkthreads = new List<Thread>();
        object internalsyncobj = new object();
        /// <summary>
        /// This method is called when this script task executes in the control flow.
        /// Before returning from this method, set the value of Dts.TaskResult to indicate success or failure.
        /// To open Help, press F1.
        /// </summary>
        public void Main()
        {
            // TODO: Add your code here
            AppDomain.CurrentDomain.UnhandledException += HandleException;
           
            Dts.TaskResult = (int)ScriptResults.Success;

            string mymsg = "thread :" + System.Threading.Thread.CurrentThread.ManagedThreadId.ToString()
                             + " domainid:"
                             + System.Threading.Thread.GetDomainID().ToString()
                         ;
            Dts.Events.FireInformation(0, "showmsg", mymsg, "", 0, ref isreuse);

            int times = 0;
            bool isused = false;
            while (times < 300)
            {
                times++;
                Dts.Events.FireInformation(0, "showmsg", times.ToString(), "", 0, ref isreuse);
                if (times == 9 && !isused)
                {
                    Dts.Events.FireInformation(0, "showmsg", "update var_threadcount to 2", "", 0, ref isreuse);
                    Dts.Variables["var_threadcount"].Value = 2;
                    //try { Dts.VariableDispenser.Reset(); }catch { }
                    isused = true;
                }
            }

            runNewThread("test");

            Thread th = new Thread(
            obj =>
            {
                throw new Exception("hello exception in thread");
            });
            lock (internalsyncobj) { _listworkthreads.Add(th); }
            th.Start();
                 
            System.Threading.Thread.Sleep(6 * 1000);
        }

        void runNewThread(string msg)
        {
            Thread th = new Thread(
                 obj =>
                 {
                     Dts.Events.FireInformation(0, "showmsg", msg, "", 0, ref isreuse);
                     string mymsg = "thread :" + System.Threading.Thread.CurrentThread.ManagedThreadId.ToString()
                         + " domainid:"
                         + System.Threading.Thread.GetDomainID().ToString()
                     ;
                     Dts.Events.FireInformation(0, "showmsg", mymsg, "", 0, ref isreuse);

                     Thread t = new Thread(() =>
                       {
                           throw new Exception("hello exception in child thread!");
                       });
                     lock (internalsyncobj) { _listworkthreads.Add(t); }
                     t.Start();
                 }
                 );
            lock (internalsyncobj) { _listworkthreads.Add(th); }
            th.Start(msg);
        
        }
        
        void HandleException(object sender, UnhandledExceptionEventArgs e)
        {
            Dts.Events.FireInformation(0, "UnhandleException", 
                "sender:" + sender.ToString() +
                "message:" + ((Exception)e.ExceptionObject).Message
                , "", 0, ref isreuse);

            //handle child thread
          lock (internalsyncobj)
            {
                Dts.Events.FireInformation(0,"AppdomainUnhandleException", "thread count:" + _listworkthreads.Count.ToString()
                    + " start to kill all child thread at time:" + DateTime.Now.ToString()
                , "", 0, ref isreuse);
                foreach (Thread th in _listworkthreads)
                {
                    Dts.Events.FireInformation(0, "ThreadState", "thread state:" + th.ThreadState.ToString()
                     + DateTime.Now.ToString()
                , "", 0, ref isreuse);

                    try {
                        th.Abort(); }
                    catch (Exception ex) { }
                }
            }
       

        }