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  • 验证Monitor.PulseAll功效

    PulseAll MSDN:通知所有的等待线程对象状态的更改。

    所以可以理解成所有Wait锁对象的线程都将变成就绪状态。而Pulse顾名思义,只能将排在最前面的Wait就绪。

    非常简单吧,下的示例可以说明PulseAll的功能,线程1启动之后会进入Wait状态,紧接着线程3获得锁对象但也马上Wait,然后线程3获得锁对象就PulseAll了。

    PulseAll的结果就是前面两个Wait得到释放,在执行完2之后,1和3都将得到执行。如果此处用的是Pulse,则3将一直处于Wait状态。

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

    namespace ConsoleApplication1
    {
        class Program
        {
            private static object _lockObject = new object();
            static Thread tr1;
            static Thread tr2;
            static Thread tr3;
            static void Main(string[] args)
            {
                tr1 = new Thread(ThreadProc1);
                tr2 = new Thread(ThreadProc2);
                tr3 = new Thread(ThreadProc3);
                tr1.Start();
                tr3.Start();
                Thread.Sleep(1000);
                tr2.Start();
                tr1.Join();
                tr2.Join();
                tr3.Join();
                Console.ReadKey();
            }

            static void ThreadProc1()
            {
                lock(_lockObject)
                {
                    Monitor.Wait(_lockObject);
                    //Monitor.Wait(_lockObject);
                    for (int i = 0; i < 100; i++)
                    {
                        Console.WriteLine("1");
                    }   
                }
            }

            static void ThreadProc3()
            {

                lock (_lockObject)
                {
                    Monitor.Wait(_lockObject);
                    for (int i = 0; i < 100; i++)
                    {
                        Console.WriteLine("3");
                    }
                }
            }

            static void ThreadProc2()
            {
                lock (_lockObject)
                {
                    Console.WriteLine("2");
                    Monitor.PulseAll(_lockObject);
                }

            }
        }
    }

    那麽2之后1,3究竟是谁先执行呢,这涉及系统的线程调度优先级问题。这里仅做一个简单的实验,将th1的优先级设为最高,tr3的设为最低,我们看到果真1先于3执行;同理反之亦然。

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

    namespace ConsoleApplication1
    {
        class Program
        {
            private static object _lockObject = new object();
            static Thread tr1;
            static Thread tr2;
            static Thread tr3;
            static void Main(string[] args)
            {
                tr1 = new Thread(ThreadProc1);
                tr2 = new Thread(ThreadProc2);
                tr3 = new Thread(ThreadProc3);
                tr1.Priority = ThreadPriority.Highest;
                tr3.Priority = ThreadPriority.Lowest;
                tr1.Start();
                tr3.Start();
                Thread.Sleep(1000);
                tr2.Start();
                tr1.Join();
                tr2.Join();
                tr3.Join();
                Console.ReadKey();
            }

            static void ThreadProc1()
            {
                lock(_lockObject)
                {
                    Monitor.Wait(_lockObject);
                    //Monitor.Wait(_lockObject);
                    for (int i = 0; i < 100; i++)
                    {
                        Console.WriteLine("1");
                    }   
                }
            }

            static void ThreadProc3()
            {

                lock (_lockObject)
                {
                    Monitor.Wait(_lockObject);
                    for (int i = 0; i < 100; i++)
                    {
                        Console.WriteLine("3");
                    }
                }
            }

            static void ThreadProc2()
            {
                lock (_lockObject)
                {
                    Console.WriteLine("2");
                    Monitor.PulseAll(_lockObject);
                }

            }
        }
    }

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  • 原文地址:https://www.cnblogs.com/dancewithautomation/p/2418825.html
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