C# 语言的多线程编程，完全是本科OS里的知识

 基本知识，无参数Thread和带参数的Thread

Thread类的参数就是参数指针，可以传入一个无参的函数。

如果要传入带参数的函数，先new一个ParameterizedThreadStart委托实例，带参数的函数名作为它的参数。带参数的函数必须且只能有一个object参数。参考下面的

ConterWithParam(object param)

static int iCnt = 0;
        static readonly int N = 10000;

        static void Main(string[] args)
        {
            Thread[] thrs = new Thread[N];
            for (int i = 0; i < N; i++)
            {
                thrs[i] = new Thread(Counter);
                thrs[i].Start();               
            }
            for (int i = 0; i < N; i++)
            {              
                thrs[i].Join();
            }
            Console.WriteLine(iCnt);

            iCnt = 0;

            ParameterizedThreadStart[] thrsp = new ParameterizedThreadStart[N];
            object param = 2;
            for (int i = 0; i < N; i++)
            {
                thrsp[i] = new ParameterizedThreadStart(ConterWithParam);
                thrs[i] = new Thread(thrsp[i]);
                thrs[i].Start(param);
            }
            for (int i = 0; i < N; i++)
            {
                //当NewThread调用Join方法的时候，MainThread就被停止执行，直到NewThread线程执行完毕
                thrs[i].Join();
            }
            Console.WriteLine(iCnt);
        }

        static void Counter()
        {
            Thread.Sleep(100);
            iCnt++;
            //Console.WriteLine("finish iCnt++,now iCnt is " + iCnt);            
        }

        static void ConterWithParam(object param)
        {
            Thread.Sleep(100);
            int i = (int)param;
            iCnt += i;
            //Console.WriteLine("finish iCnt+"+i+",now iCnt is " + iCnt);     
        }

该例子输出结果

2)互斥信号灯mutex

第一节的结果是不是有点奇怪。明明加了10000次，结果却是9550.

带参数的那个例子，一次加2，加10000次，应该是20000才对。结果却是19678.

这是因为对全局变量的访问iCnt出现了冲突。比如两个线程同时取到了iCnt=0时的值，同时执行了i++，那么iCnt的最后状态肯定是1，而不是会2。为了让iCnt得到正确的值。

我们引入互斥信号灯。

static int iCnt = 0;
        static readonly int N = 10000;
        static Mutex mut = new Mutex();

        static void Main(string[] args)
        {
            Thread[] thrs = new Thread[N];
            for (int i = 0; i < N; i++)
            {
                thrs[i] = new Thread(Counter);
                thrs[i].Start();               
            }
            for (int i = 0; i < N; i++)
            {              
                thrs[i].Join();
            }
            Console.WriteLine(iCnt);

            iCnt = 0;

            ParameterizedThreadStart[] thrsp = new ParameterizedThreadStart[N];
            object param = 2;
            for (int i = 0; i < N; i++)
            {
                thrsp[i] = new ParameterizedThreadStart(ConterWithParam);
                thrs[i] = new Thread(thrsp[i]);
                thrs[i].Start(param);
            }
            for (int i = 0; i < N; i++)
            {
                //当NewThread调用Join方法的时候，MainThread就被停止执行，直到NewThread线程执行完毕
                thrs[i].Join();
            }
            Console.WriteLine(iCnt);
        }

        static void Counter()
        {
            Thread.Sleep(10);
            //锁
            mut.WaitOne();            
            iCnt++;
            //释放
            mut.ReleaseMutex();
            //Console.WriteLine("finish iCnt++,now iCnt is " + iCnt);            
        }

        static void ConterWithParam(object param)
        {
            Thread.Sleep(10);
            //锁住
            mut.WaitOne();            
            int i = (int)param;
            iCnt += i;
            //释放
            mut.ReleaseMutex();
            //Console.WriteLine("finish iCnt+"+i+",now iCnt is " + iCnt);     
        }

本次执行结果

3) 同步信号灯Semaphore

用最经典的生产者-消费者来解释。

static Semaphore sem = new Semaphore(0, 1);
        static Semaphore sem2 = new Semaphore(0, 5);

        static void Main(string[] args)
        {
            Console.WriteLine("消费者等生产者生产一个item");
            Thread thConsumer = new Thread(Consume);
            thConsumer.Start();
            Thread thProductor = new Thread(Product);
            thProductor.Start();

            thConsumer.Join();
            thProductor.Join();
            Console.WriteLine(".............................");

            Console.WriteLine("多并发的例子.....");
            for (int i = 0; i < 10; i++)
            {
                Thread t1 = new Thread(Consume2);
                t1.Start();
                Thread t2 = new Thread(Product2);
                t2.Start();
            }//end for
            

        }


        static void Product()
        {
            Thread.Sleep(2000);
            Console.WriteLine("Product an item...");
            sem.Release();
        }

        static void Consume()
        {
            Thread.Sleep(1000);
            Console.WriteLine("Consumer is waiting an item...");
            sem.WaitOne();
            Console.WriteLine("Consumer get an item...");
        }



        static void Product2()
        {
            Thread.Sleep(1000);
            Console.WriteLine("Product an item...");
            sem2.Release();
        }

        static void Consume2()
        {
            Thread.Sleep(1000);
            Console.WriteLine("Consumer is waiting an item...");
            sem2.WaitOne();
            Console.WriteLine("Consumer get an item...");
        }