0

这是代码：

class program
{
    static ReaderWriterLockSlim rwLock = new ReaderWriterLockSlim();
    static void Main(string[] args)
    {
        for (int i = 0; i < 2; i++)
        {
            Task.Factory.StartNew(Read);
        }
        for (int i = 0; i < 1; i++)
        {
            Task.Factory.StartNew(Write);
        }
        Console.Read();
    }

    static void Read()
    {
        while (true)
        {
            rwLock.EnterReadLock();;
            Thread.Sleep(100);
            Console.WriteLine($"{Thread.CurrentThread.ManagedThreadId}  reading");
            rwLock.ExitReadLock();
        }
    }
    static void Write()
    {
        while (true)
        {
            rwLock.EnterWriteLock();
            Thread.Sleep(3000);
            Console.WriteLine($"{Thread.CurrentThread.ManagedThreadId} writing");
            rwLock.ExitWriteLock();
        }
    }
}

我想测试ReaderWriterLockSlim，我期望的结果是在控制台中交替读取和写入，但最后只能在控制台中写入。

结果如下：

5 reading 2020/2/17 18:24:36
4 reading 2020/2/17 18:24:36
3 reading 2020/2/17 18:24:36
6 writing 2020/2/17 18:24:39
6 writing 2020/2/17 18:24:42
6 writing 2020/2/17 18:24:45
6 writing 2020/2/17 18:24:48
6 writing 2020/2/17 18:24:51
6 writing 2020/2/17 18:24:54
6 writing 2020/2/17 18:24:57
6 writing 2020/2/17 18:25:00
6 writing 2020/2/17 18:25:03
6 writing 2020/2/17 18:25:06

但是当使用 ReaderWriterLock 时，它的替代显示。结果如下：

4 reading 2020/2/17 18:30:22
3 reading 2020/2/17 18:30:22
5 reading 2020/2/17 18:30:22
6 writing 2020/2/17 18:30:25
4 reading 2020/2/17 18:30:25
3 reading 2020/2/17 18:30:25
5 reading 2020/2/17 18:30:25
6 writing 2020/2/17 18:30:28
4 reading 2020/2/17 18:30:29
5 reading 2020/2/17 18:30:29
3 reading 2020/2/17 18:30:29
6 writing 2020/2/17 18:30:32
4 reading 2020/2/17 18:30:32
5 reading 2020/2/17 18:30:32
3 reading 2020/2/17 18:30:32
6 writing 2020/2/17 18:30:35
5 reading 2020/2/17 18:30:35
3 reading 2020/2/17 18:30:35
4 reading 2020/2/17 18:30:35
6 writing 2020/2/17 18:30:38
5 reading 2020/2/17 18:30:45
3 reading 2020/2/17 18:30:45
4 reading 2020/2/17 18:30:45

为什么会出现这种情况，有人告诉我这种现象的原因吗？希望回答

4

1 回答 1

0

这里的问题是 thread.Sleep() 在关键部分内被调用。这会导致编写器线程每次持有锁 3 秒，并在很短的时间内释放它，在此期间编写器线程重新获取锁，因为在这种情况下，ReaderWriterLockSlim 显然为编写器提供了更好的优先级。

我在释放锁后尝试调用 Thread.Sleep() 并且一切都按预期工作。

class LockProgram
{
    static ReaderWriterLockSlim rwLock = new ReaderWriterLockSlim();
    static void Main(string[] args)
    {
        for (int i = 0; i < 2; i++)
        {
            Task.Factory.StartNew(Read);
        }
        for (int i = 0; i < 1; i++)
        {
            Task.Factory.StartNew(Write);
        }
        Console.Read();
    }

    static void Read()
    {
        while (true)
        {
            rwLock.EnterReadLock(); ;                
            Console.WriteLine($"{Thread.CurrentThread.ManagedThreadId}  reading");
            rwLock.ExitReadLock();
            Thread.Sleep(100);
        }
    }
    static void Write()
    {
        while (true)
        {
            rwLock.EnterWriteLock();                
            Console.WriteLine($"{Thread.CurrentThread.ManagedThreadId} writing");
            rwLock.ExitWriteLock();
            Thread.Sleep(3000);
        }
    }
}

值得查看ReaderWriterLockSlim和ReaderWriterLock的 .Net 参考源

于 2020-02-17T13:44:28.757 回答