这是一个正确的互锁同步设计吗？

Question

我有一个采样的系统.我在应用程序中有多个对这些示例感兴趣的客户端线程,但是获取Sample的实际过程只能在一个上下文中进行.它足够快,它可以阻止调用过程直到采样完成,但足够慢,我不希望多个线程堆积请求.我想出了这个设计(剥离到最小的细节):

public class Sample
{
    private static Sample _lastSample;
    private static int _isSampling;

    public static Sample TakeSample(AutomationManager automation)
    {
        //Only start sampling if not already sampling in some other context
        if (Interlocked.CompareExchange(ref _isSampling, 0, 1) == 0)
        {
            try
            {
                Sample sample = new Sample();
                sample.PerformSampling(automation);
                _lastSample = sample;
            }
            finally
            {
                //We're done sampling
                _isSampling = 0;
            }
        }

        return _lastSample;
    }

    private void PerformSampling(AutomationManager automation)
    {
        //Lots of stuff going on that shouldn't be run in more than one context at the same time
    }
}

这在我描述的场景中是否安全？

Answer 1

是的,它看起来很安全,因为int这里是原子类型.但我仍然建议更换

private static int _isSampling;

同

private static object _samplingLock = new object();

并使用:

lock(_samplingLock)
{
    Sample sample = new Sample();
    sample.PerformSampling(automation);
   _lastSample = sample;
}

只是因为它是推荐的模式,并且还确保正确处理对_lastSample的所有访问.

注意:我希望速度可比,lock使用内部使用Interlocked的托管Monitor类.

编辑:

我错过了后退方面,这是另一个版本:

   if (System.Threading.Monitor.TryEnter(_samplingLock))
   {
     try
     {
         .... // sample stuff
     }
     finally
     {
          System.Threading.Monitor.Exit(_samplingLock);
     }
   }