Lock锁机制在线程中的应用

（一）锁的概念

public static class ThreadExt
{
    public static void WriteLine(this Thread t, string remark, params Thread[] threads)
    {
        DateTime dt = DateTime.Now;
        System.Diagnostics.StackFrame stf = new System.Diagnostics.StackTrace(true).GetFrame(1);
        StringBuilder sb = new StringBuilder();
        foreach (Thread item in threads)
        {
            sb.AppendFormat("[线程名:{0,-5} ID:{1} 状态:{2,-12}]	", item.Name, item.ManagedThreadId, item.ThreadState);
        }
        Console.WriteLine("{0:HH:mm:ss.fff} L:{6,-4}{1,-12}	当前线程名:{2,-5} ID:{3} 状态:{4,-13} {5}",
            dt, remark, t.Name, t.ManagedThreadId, t.ThreadState, sb.ToString(), stf.GetFileLineNumber());
    }
}
class MonitorSample
{
    private static readonly object _syncObj = new Object();

    static void P(object mainObj)
    {
        Thread main = mainObj as Thread;
        Thread.CurrentThread.WriteLine("P:lock()前 ", main);
        lock (_syncObj)
        {
            Thread.CurrentThread.WriteLine("P:进入Lock ", main);
            Thread.Sleep(5000);
            Thread.CurrentThread.WriteLine("P:退出Lock ", main);
        }
        Thread.CurrentThread.WriteLine("P:结束    ", main);
    }

    static void Main(string[] args)
    {
        Thread t = new Thread(new ParameterizedThreadStart(P));
        t.Name = "P";
        Thread.CurrentThread.Name = "Main";
        t.Start(Thread.CurrentThread);
        Thread.CurrentThread.WriteLine("Main:lock()前   ", t);
        lock (_syncObj)
        {
            Thread.CurrentThread.WriteLine("Main:进入Lock   ", t);
            Thread.Sleep(5000);
            Thread.CurrentThread.WriteLine("Main:退出Lock   ", t);
        }
        Thread.CurrentThread.WriteLine("Main:结束   ", t);
    }
}

代码分析如下：

（二）死锁

public static class ThreadExt
{
    public static void WriteLine(this Thread t, string remark, params Thread[] threads)
    {
        DateTime dt = DateTime.Now;
        System.Diagnostics.StackFrame stf = new System.Diagnostics.StackTrace(true).GetFrame(1);
        StringBuilder sb = new StringBuilder();
        foreach (Thread item in threads)
        {
            sb.AppendFormat("[线程名:{0,-5} ID:{1} 状态:{2,-12}]	", item.Name, item.ManagedThreadId, item.ThreadState);
        }
        Console.WriteLine("{0:HH:mm:ss.fff} L:{6,-4}{1,-12}	当前线程名:{2,-5} ID:{3} 状态:{4,-13} {5}",
            dt, remark, t.Name, t.ManagedThreadId, t.ThreadState, sb.ToString(), stf.GetFileLineNumber());
    }
}
class MonitorSample
{
    private static readonly object _syncObj1 = new Object();
    private static readonly object _syncObj2 = new Object();

    static void P(object mainObj)
    {
        Thread main = mainObj as Thread;
        Thread.CurrentThread.WriteLine("P:lock()前 ", main);
        lock (_syncObj2)
        {
            Thread.CurrentThread.WriteLine("P:进入Lock2 ", main);
            Thread.Sleep(1000);
            Thread.CurrentThread.WriteLine("P:进入Sleep ", main);
            lock (_syncObj1)
            {
                Thread.CurrentThread.WriteLine("P:进入Lock1 ", main);
                Thread.Sleep(5000);
                Thread.CurrentThread.WriteLine("P:退出Lock1 ", main);
            }
        }
        Thread.CurrentThread.WriteLine("P:结束    ", main);
    }

    static void Main(string[] args)
    {
        Thread t = new Thread(new ParameterizedThreadStart(P));
        t.Name = "P";
        Thread.CurrentThread.Name = "Main";
        t.Start(Thread.CurrentThread);
        Thread.CurrentThread.WriteLine("Main:lock()前   ", t);
        lock (_syncObj1)
        {
            Thread.CurrentThread.WriteLine("Main:进入Lock1   ", t);
            Thread.Sleep(1000);
            lock (_syncObj2)
            {
                Thread.CurrentThread.WriteLine("Main:进入Lock2   ", t);
                Thread.Sleep(5000);
                Thread.CurrentThread.WriteLine("Main:退出Lock2   ", t);
            }
        }
        Thread.CurrentThread.WriteLine("Main:结束   ", t);
    }
}

（二）lock关键词在C#语言中的用法

class Program
{
    private static readonly object _syncRoot = new Object();
    static Thread t1 = new Thread(new ParameterizedThreadStart(P));
    static Thread t2 = new Thread(new ParameterizedThreadStart(P));
    static Thread t3 = new Thread(new ParameterizedThreadStart(P));
    static void Main(string[] args)
    {
        t1.Name = "A";
        t2.Name = "B";
        t3.Name = "C";

        t1.Start(t1);
        t2.Start(t2);
        t3.Start(t3);
        //t1.Join();
        //t2.Join();
        //t3.Join();
        //Console.WriteLine("------------");
        //Console.ReadKey();
    }

    static void P(object name)
    {
        Thread t = name as Thread;
        Console.WriteLine("线程名:{0}-1 占用资源	时间:{5:HH:mm:ss.fff}  当前线程:{1,-18} A:{2,-18} B:{3,-18} C:{4}",
            t.Name, t.ThreadState.ToString() + " ID:" + t.ManagedThreadId, t1.ThreadState.ToString() + " ID:" + t1.ManagedThreadId,
            t2.ThreadState.ToString() + " ID:" + t2.ManagedThreadId, t3.ThreadState.ToString() + " ID:" + t3.ManagedThreadId,
            DateTime.Now);
        lock (_syncRoot)
        {
            Console.WriteLine("线程名:{0}-2 Sleep前	时间:{5:HH:mm:ss.fff}  当前线程:{1,-18} A:{2,-18} B:{3,-18} C:{4}",
                t.Name, t.ThreadState.ToString() + " ID:" + t.ManagedThreadId, t1.ThreadState.ToString() + " ID:" + t1.ManagedThreadId,
                t2.ThreadState.ToString() + " ID:" + t2.ManagedThreadId, t3.ThreadState.ToString() + " ID:" + t3.ManagedThreadId,
                DateTime.Now);
            Thread.Sleep(5000);
            Console.WriteLine("线程名:{0}-3 Sleep后	时间:{5:HH:mm:ss.fff}  当前线程:{1,-18} A:{2,-18} B:{3,-18} C:{4}",
                t.Name, t.ThreadState.ToString() + " ID:" + t.ManagedThreadId, t1.ThreadState.ToString() + " ID:" + t1.ManagedThreadId,
                t2.ThreadState.ToString() + " ID:" + t2.ManagedThreadId, t3.ThreadState.ToString() + " ID:" + t3.ManagedThreadId,
                DateTime.Now);
        }
        Console.WriteLine("线程名:{0}-4 释放资源	时间:{5:HH:mm:ss.fff}  当前线程:{1,-18} A:{2,-18} B:{3,-18} C:{4}",
            t.Name, t.ThreadState.ToString() + " ID:" + t.ManagedThreadId, t1.ThreadState.ToString() + " ID:" + t1.ManagedThreadId,
            t2.ThreadState.ToString() + " ID:" + t2.ManagedThreadId, t3.ThreadState.ToString() + " ID:" + t3.ManagedThreadId,
            DateTime.Now);
    }
}

执行分析如下：下图列出了代码四次执行输出的结果。