mina里的死锁检测

 private void checkDeadLock() {
        // Only read / write / connect / write future can cause dead lock. 
        if (!(this instanceof CloseFuture || this instanceof WriteFuture ||
              this instanceof ReadFuture || this instanceof ConnectFuture)) {
            return;
        }
        
        // Get the current thread stackTrace. 
        // Using Thread.currentThread().getStackTrace() is the best solution,
        // even if slightly less efficient than doing a new Exception().getStackTrace(),
        // as internally, it does exactly the same thing. The advantage of using
        // this solution is that we may benefit some improvement with some
        // future versions of Java.
        StackTraceElement[] stackTrace = Thread.currentThread().getStackTrace();

        // Simple and quick check.
        for (StackTraceElement s: stackTrace) {
            if (AbstractPollingIoProcessor.class.getName().equals(s.getClassName())) {
                IllegalStateException e = new IllegalStateException( "t" );
                e.getStackTrace();
                throw new IllegalStateException(
                    "DEAD LOCK: " + IoFuture.class.getSimpleName() +
                    ".await() was invoked from an I/O processor thread.  " +
                    "Please use " + IoFutureListener.class.getSimpleName() +
                    " or configure a proper thread model alternatively.");
            }
        }

        // And then more precisely.
        for (StackTraceElement s: stackTrace) {
            try {
                Class<?> cls = DefaultIoFuture.class.getClassLoader().loadClass(s.getClassName());
                if (IoProcessor.class.isAssignableFrom(cls)) {
                    throw new IllegalStateException(
                        "DEAD LOCK: " + IoFuture.class.getSimpleName() +
                        ".await() was invoked from an I/O processor thread.  " +
                        "Please use " + IoFutureListener.class.getSimpleName() +
                        " or configure a proper thread model alternatively.");
                }
            } catch (Exception cnfe) {
                // Ignore
            }
        }
    }

  这个死锁检测算法位于DefaultIoFuture中，策略是分两步进行，首先是用一个简单而快速的方法检测，然后再用一个更精确地方法来检测。 第一个方法通过getStackTrace获得当前的线程的整个堆栈的元素数组，然后遍历这个数组，看是否有某一层的调用的class是AbstractPollingIoProcessor，如果有，就是存在循环调用，出现死锁。这是因为AbstractPollingIoProcessor是实现IoProcessor的抽象类，包含一个Executor，创建线程处理任务，