.Net ReaderWriterLockSlim 锁

• .Net ReaderWriterLockSlim 锁
  • 场景一
  • 场景二

读写锁的概念很简单，允许多个线程同时获取读锁，但同一时间只允许一个线程获得写锁，因此也称作共享-独占锁。

public class ReadWriteLockDemo
{
    public static ReaderWriterLockSlim readerwritelock = new ReaderWriterLockSlim();
    public static long i =0;
    public void Read(long value)
    {
        readerwritelock.EnterReadLock();
        Thread.Sleep(5000);
        Debug.WriteLine($"Thread ID :{Thread.CurrentThread.ManagedThreadId} Read Lock Value：{i} Time：{DateTime.Now}");
        readerwritelock.ExitReadLock();
    }
    public void Write(long value)
    {
        readerwritelock.EnterWriteLock();
        Thread.Sleep(5000);
        i = value;
        Debug.WriteLine($"Thread ID :{Thread.CurrentThread.ManagedThreadId} Write Lock Value：{i} Time：{DateTime.Now}");
        readerwritelock.ExitWriteLock();
    }
    public void Read(long value,int millisecondsTimeout)
    {
        //三秒内没执行将会自动释放
        bool islock = readerwritelock.TryEnterReadLock(millisecondsTimeout);
        if (islock)
        {
            Thread.Sleep(5000);
            Debug.WriteLine($"Thread ID :{Thread.CurrentThread.ManagedThreadId} Read Lock Value：{i} Time：{DateTime.Now} IsLock:{islock}");
            readerwritelock.ExitReadLock();
        }
    }
    public void Write(long value, int millisecondsTimeout)
    {
        bool islock = readerwritelock.TryEnterWriteLock(millisecondsTimeout);
        if (islock)
        {
            Thread.Sleep(5000);
            i = value;
            Debug.WriteLine($"Thread ID :{Thread.CurrentThread.ManagedThreadId} Write Lock Value：{i} Time：{DateTime.Now} IsLock:{islock}");
            readerwritelock.ExitWriteLock();
        }
    }
}

场景一

只要前面那个写入线程没有释放，每次写都需要阻塞（排队等）。(10个读写线程，每次处理需要花5秒)

[Test]
public void TestReadWriteLock()
{
    ReadWriteLockDemo readWriteLockDemo = new ReadWriteLockDemo();
    List<Task> list = new List<Task>();
    for (int i = 0; i < 10; i++)
    {
        int a = i;
        Task task = new Task(() => {
            readWriteLockDemo.Write(a);
            readWriteLockDemo.Read(a);
        });
        task.Start();
        list.Add(task);
    }
    Task.WaitAll(list.ToArray());
}

场景二

只要前面那个写入线程没有释放，它叫我和其他线程等它3秒钟，3秒等完了还是没处理完我们走了，3秒内处理完了轮到我了我就上，或者轮到其他线程那个线程上，我们走了。

[Test]
public void TestReadWriteLockTimeOut()
{
    ReadWriteLockDemo readWriteLockDemo = new ReadWriteLockDemo();
    List<Task> list = new List<Task>();
    for (int i = 0; i < 10; i++)
    {
        int a = i;
        Task task = new Task(() => {
            readWriteLockDemo.Write(a,3000);
            readWriteLockDemo.Read(a, 3000);
        });
        task.Start();
        list.Add(task);
    }
    Task.WaitAll(list.ToArray());
}

我们这里改改，我们不急可以等100秒.这样我们就都可以等到处理完成。

readWriteLockDemo.Write(a,100000);