Question

我在一个名为 Loadeable 的类中有一个锁定对象：

private readonly object _lock;

lock(_lock){ /*...*/ }语句仅在可加载类中使用，以防止死锁。 （注意：_lock对象的访问者是私有的）

由于我仍想从外部运行锁定代码，我将以下方法添加到可加载类：

public void RunLockedProcedure(Action Procedure) {
   lock(_lock) {
      Procedure();
   }
}

可加载还包含一个名为IsLoaded的属性和一个名为Load(int)的方法，但我没有展示它们，因为它是很多代码而且并不重要。但请务必注意IsLoaded和Load(int)访问线程安全数据。

现在想象一下名为Item and Creation 的 Loadable的子类。
整数_creationId和以下方法是项：

的成员
public Creation LazyGetCreation() { int creationIdCopy = 0; //The following lambda provides thread-safety inside this instance. RunLockedProcedure(() => { if(!IsLoaded) { throw new InvalidOperationException("A component cannot be loaded if the instance is not loaded"); } else { if(_creationId < 1) throw new InvalidOperationException("The loaded Id of the creation component (" + _creationId + ") is less than 1."); creationIdCopy = _creationId; if(Creation == null) Creation = new Creation(); } }); //We are not in a thread-safe block and thus Creation might already be null again (I had to use the elvis operator) Creation?.RunLockedProcedure(() => { if(!Creation.IsLoaded) Creation.Load(creationIdCopy); //This is a heavy operation and takes a bit time... }); }

让我现在解决问题：
elvis运算符很棒，但是对Creation(?).RunLockedProcedure(() => { /*...*/ })的调用应该真正在上面的线程安全块中执行（它需要加载 Item ）。
但后来我遇到的问题是，非常重的Creation.Load(creationIdCopy)也会在锁定的块中执行，从而锁定项一段时间。我正在寻找的是一种安全调用Creation.RunLockedProcedure(/*...*/)但在非锁定范围内执行() => { /*...*/ }的方法。（必须锁定到Creation实例，但不能锁定到Item实例）

也许有一个我还不知道的功能，但找到解决方案会很糟糕。
非常感谢你。

Answer 1

线程安全保证应该在Load本身处理，而不是在外部处理。否则，您需要在每个调用load的地方使用它。这样的事可能适合你：

private object _lock = new object();
public void Load(int someID)
{
    if (IsLoaded) //No-locked check, early exit.
        return;

    lock (_lock) //We think it's not loaded, lock to prevent issues and double check
        if (IsLoaded)
            return;
        else
            IsLoaded = true; //Immediately set IsLoaded = true

    try 
    {
        //Do loading stuff
    } catch (Exception ex) {
        lock(_lock)
            IsLoaded = false; //We failed to load, set back to false again

        throw;
    }
}

然后你这样称呼它：

public Creation LazyGetCreation() {
   int creationIdCopy = 0;

   //The following lambda provides thread-safety inside this instance.
   RunLockedProcedure(() => {
      if(!IsLoaded) {
         throw new InvalidOperationException("A component cannot be loaded if the instance is not loaded");
      } else {
         if(_creationId < 1)
            throw new InvalidOperationException("The loaded Id of the creation component (" + _creationId + ") is less than 1.");

         creationIdCopy = _creationId;
         if(Creation == null)
            Creation = new Creation();
      }
   });

   Creation.Load(creationIdCopy);
}

如果您不想立即设置IsLoaded，则可以在创建对象之前引入IsLoading并检查两者是否为false，并立即将IsLoading设置为true。 / p>

C＃如何锁定对非高性能代码的调用

1 个答案: