C#マルチスレッドの反発

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading;

namespace MutexTest
{
    class MutexTest
    {
        static object m_lock = new object();
        static void Main(string[] args)
        {
            Mutex m = new Mutex();
            Thread t1 = new Thread(new ParameterizedThreadStart(Thread1));
            t1.IsBackground = true;
            t1.Start(m);
            Thread t2 = new Thread(new ParameterizedThreadStart(Thread2));
            t2.IsBackground = true;
            t2.Start(m);
            Console.ReadLine();            
        }

        static void Thread1(object obj)
        {
            Mutex m = obj as Mutex;
            while (true)
            {
                m.WaitOne();
                WriteLine("In Thread-1");
                m.ReleaseMutex();
                Thread.Sleep(100);
            }
        }

        static void Thread2(object obj)
        {
            Mutex m = obj as Mutex;
            while (true)
            {
                m.WaitOne();
                WriteLine("In Thread-----------2");
                m.ReleaseMutex();
                Thread.Sleep(1000);
            }
        }

        static void WriteLine(string msg)
        {
            lock (m_lock)
            {
                Console.WriteLine(msg);
            }
        }
    }
}