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这是我上一个问题的延续——重构同步块保持执行顺序不变

我在一个我想要取消的功能中有一个同步块，还有其他东西可以减少争用并提高性能。

public CallCompletion startCall()
{
  long currentTime;
  Pending pending = null;
  long lastStartTime = _lastStartTime.get();

  currentTime = _clock.currentTimeMillis();
  synchronized (_lock)
  {
      _lastStartTime = currentTime;
      _tracker.getStatsWithCurrentTime(currentTime);
      _sumOfOutstandingStartTimes += currentTime;

      _callStartCountTotal++;
      _tracker._callStartCount++;
      if (_callStartsInLastSecondTracker != null) _callStartsInLastSecondTracker.addCall();
      _concurrency++;
      if (_concurrency > _tracker._concurrentMax) {
        _tracker._concurrentMax = _concurrency;
      }
      pending = checkForPending();  
  }
  if (pending != null)
  {
    pending.deliver();
  }
  return new CallCompletionImpl(currentTime);
}

我正在尝试用 AtomicLong 替换_lastStartTime：

public CallCompletion startCall()
{
  long currentTime;
  Pending pending = null;
  long lastStartTime = _lastStartTime.get();

  currentTime = _clock.currentTimeMillis();
  //synchronized (_lock)
  //{
    if (_lastStartTime.compareAndSet(lastStartTime, currentTime)) {
      System.out.println("Inside atomic if -->" + Thread.currentThread().getName());
      //_lastStartTime = currentTime;
      _tracker.getStatsWithCurrentTime(currentTime);
      _sumOfOutstandingStartTimes += currentTime;

      _callStartCountTotal++;
      _tracker._callStartCount++;
      if (_callStartsInLastSecondTracker != null) _callStartsInLastSecondTracker.addCall();
      _concurrency++;
      if (_concurrency > _tracker._concurrentMax) {
        _tracker._concurrentMax = _concurrency;
      }
      pending = checkForPending();
      System.out.println("Leaving atomic if -->" + Thread.currentThread().getName());
    }
 // }
  if (pending != null)
  {
    pending.deliver();
  }
  return new CallCompletionImpl(currentTime);
}

compareAndSet然而，尽管大多数线程是按顺序进入和退出块的，但还是有一些线程搞砸了：

Inside atomic if -->pool-1-thread-3
Inside atomic if -->pool-1-thread-2
Leaving atomic if -->pool-1-thread-2
Leaving atomic if -->pool-1-thread-3

不确定我的逻辑是否正确同步执行或我做错了什么。任何帮助将不胜感激。

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