Question

我只是试验Mutex并编写了以下代码。

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

namespace Mutex_WaitOnewithTimeouts
{
    class Program
    {
        private static Mutex mut = new Mutex();
        private static int numOfThreads = 5;
        private static int numOfIterations = 3;
        private static Random rand = new Random();

        static void Main(string[] args)
        {
            Thread[] threads = new Thread[5];
            for (int num = 0; num < numOfThreads; num++)
            {
                threads[num] = new Thread(new ThreadStart(MyThreadProc));
                threads[num].Name = String.Format("Thread{0}", num);
                threads[num].Start();
            }
            Console.Read();
        }

        private static void MyThreadProc()
        {
            for (int iteration = 0; iteration < numOfIterations; iteration++)
            {
                UseResource();
            }
        }

        private static void UseResource()
        {
            Console.WriteLine("{0} accessing ", Thread.CurrentThread.Name);
            int time = (int)(rand.NextDouble() * 100);
            try
            {
                if (mut.WaitOne(time))
                {
                    Console.WriteLine("Yippie got mutex for {0}", Thread.CurrentThread.Name);
                    Thread.Sleep((int)rand.NextDouble() * 5000);
                }
                else
                {
                    Console.WriteLine("Nopee.... Timeout occured for {0}", Thread.CurrentThread.Name);
                }
            }
            catch (AbandonedMutexException ex)
            {
                Console.WriteLine(" Exception is caught");
            }
            finally 
            {
                Console.WriteLine("Releasing mutex for {0}", Thread.CurrentThread.Name);
               mut.ReleaseMutex();

            }

        }
    }
}

但我有时会收到ApplicationException ..如果我的代码有任何问题，有人可以帮助我吗？请解释这个异常何时触发。

从非同步代码块调用对象同步方法。在尝试释放互斥锁时，我在finally块中得到了这个。

Answer 1

即使您的WaitOne失败，您也会释放互斥锁。在您知道已获得互斥锁的if语句中移动ReleaseMutex调用。

Answer 2

@ John的回答是正确的但是对于后人来说，我认为更好的模式是在if中将布尔值设置为true，然后仍然在release中执行finally阻止，但这次只有在布尔值为真时才这样做。问题是，如果任何if子句抛出，则互斥锁将不会被释放。我假设您将在if子句中添加更多内容，而不仅仅是写入和休眠。

如果可以，您总是希望使用try { ... } finally模式，但只是防止waitOne()调用返回false。如下所示：

bool release = false;
try {
    if (mut.waitOne(time)) {
        release = true;
        ...
    } else {
        ...
    }
} catch (AbandonedMutexException ex) {
    ...
} finally {
    ...
    if (release) {
        mut.ReleaseMutex();
    }
}

为什么抛出ApplicationException？

2 个答案: