WaitHandle.WaitAny()和WaitHandle.WaitAll()使用问题

Question

我的应用程序没有正确退出。我只是尝试打印连接的总数，然后等待所有上传操作完成，然后优雅地退出。

下面是代码..。

using System;
using System.Net;
using System.Threading;
using System.IO;
using System.Text;

namespace ServicePointDemo
{
    class Program
    {
        struct UploadState
        {
            public string Filename;
            public AutoResetEvent are;
        }

        static void Main(string[] args)
        {
            AutoResetEvent are = new AutoResetEvent(false);
            ServicePoint sp = ServicePointManager.FindServicePoint(new Uri("ftp://xxx.xxx.xxx.xxx/public"));

            UploadState us1 = new UploadState();
            us1.are = new AutoResetEvent(false);
            us1.Filename = @"C:\inventory.xls";

            UploadState us2 = new UploadState();
            us2.are = new AutoResetEvent(false);
            us2.Filename = @"C:\somefile.txt";

            Thread t1, t2;
            t1 = new Thread(new ParameterizedThreadStart(DoUpload));
            t2 = new Thread(new ParameterizedThreadStart(DoUpload));

            t1.Start(us1);            
            t2.Start(us2);

            Console.WriteLine("Waiting for something to trigger up");
            WaitHandle.WaitAny(new WaitHandle[] { us1.are, us2.are });            

            Console.WriteLine("CurrentConnections = {0}", sp.CurrentConnections);
            Console.WriteLine("Waiting for all operations to complete...");            
            WaitHandle.WaitAll(new WaitHandle[] { us1.are, us2.are });

            Console.WriteLine("Press enter to quit");
            Console.ReadLine();
        }

        static void DoUpload(object state)
        {
            string filename = ((UploadState)state).Filename;
            FtpWebRequest ftpRequest = (FtpWebRequest)WebRequest.Create("ftp://172.16.130.22/public/" + Path.GetFileName(filename));
            Console.WriteLine("Upload URI = {0}", ftpRequest.RequestUri.AbsoluteUri);
            ftpRequest.Method = WebRequestMethods.Ftp.UploadFile;
            ftpRequest.Credentials = new NetworkCredential("anonymous", "guest@");
            ftpRequest.Proxy = new WebProxy();
            Stream stream = null;
            FileStream file = new FileStream(filename, FileMode.Open);
            Console.WriteLine("Total file size of {0} = {1}", filename, file.Length);
            StreamReader rdr = new StreamReader(file);
            Console.WriteLine("Getting bytes of {0}", filename);
            byte[] fileBytes = Encoding.ASCII.GetBytes(rdr.ReadToEnd());
            rdr.Close();
            Console.WriteLine("Acquiring connection of {0} upload...", filename);
            try
            {
                stream = ftpRequest.GetRequestStream();
                Console.WriteLine("Upload of {0} has acquired a connection", filename);
                ((UploadState)state).are.Set();
                stream.Write(fileBytes, 0, fileBytes.Length);
                Console.WriteLine("Uploading {0} complete", filename);
            }
            catch (Exception ex)
            {
                Console.WriteLine("Exception has occurred: {0}", ex.Message);                
            }
            finally
            {
                Console.WriteLine("Ending uploading {0}", filename);
                stream.Close();
                ((UploadState)state).are.Set();                
            }
            Console.WriteLine("Quit DoUpload() for {0}", filename);//...is not executed(?)
        }
    }
}

Answer 1

您的AutoResetEvents上似乎存在竞争条件

如果线程运行得很快，它们可以在主线程到达第一个WaitAny()之前对自动重置事件调用Set()两次。这将允许它传递第一个WaitAny()，但会在WaitAll()上阻塞，因为两个线程都不再调用Set()。(您可以通过在启动两个后台线程后立即在主线程中放置一个长Thread.Sleep()来模拟此过程)

我建议您使用两个单独的AutoResetEvents (或者只是普通的EventWaitHandles)，一个是在获取连接时设置的，另一个是在连接完成时设置的，所以您不需要依赖线程的时间。

Answer 2

将WaitAll()调用替换为对每个线程的Join()调用。

顺便说一下，您不需要在AutoResetEvent ()中使用第一个Main are，因为它并没有被使用。