【Darwin学习笔记】之TaskThread

标签：darwin

【转载请注明出处】：http://blog.csdn.net/longlong530

学习TaskThread主要有三个类要关注：

TaskTreadPool： 任务线程池

TaskThread：任务线程

Task: 任务

1. TaskThreadPool
Darwin运行着一个或者多个任务（Task）线程，并将他们统一在线程池TaskThreadPool中管理。任务线程从事件线程中接收RTSP和RTP请求，然后把请求传递到恰当的服务器模块进行处理，把数据包发送给客户端。
缺省情况下，核心服务器为每一个处理器创建一个任务线程。（numProcessors = OS::GetNumProcessors();）     

TaskThreadPool::SetNumShortTaskThreads(numShortTaskThreads);        
TaskThreadPool::SetNumBlockingTaskThreads(numBlockingThreads);        
TaskThreadPool::AddThreads(numThreads);		
sServer->InitNumThreads(numThreads);

void TaskThread::Entry()
{
    Task* theTask = NULL;
    
    while (true) 
    {
		//不停的从内部的队列中取到Task才返回;,此时的Task既不在堆中，也不在队列中;
        theTask = this->WaitForTask();
        /*此处省略，主要是对调用task的Run方法的返回值做不同的分支处理，详细分析在Task章节介绍*/
     }

我们还是仔细分析下WaitForTask方法吧：

Task* TaskThread::WaitForTask()
{
    while (true)
    {
        SInt64 theCurrentTime = OS::Milliseconds();
        /*如果堆中有任务，且任务已经到执行时间，返回该任务。
		PeekMin函数见OSHeap.h，窃听堆中第一个元素（但不取出）*/
        if ((fHeap.PeekMin() != NULL) && (fHeap.PeekMin()->GetValue() <= theCurrentTime))
        {    
            if (TASK_DEBUG) qtss_printf("TaskThread::WaitForTask found timer-task=%s thread %p fHeap.CurrentHeapSize(%"_U32BITARG_") taskElem = %p enclose=%p\n",((Task*)fHeap.PeekMin()->GetEnclosingObject())->fTaskName, (void *) this, fHeap.CurrentHeapSize(), (void *) fHeap.PeekMin(), (void *) fHeap.PeekMin()->GetEnclosingObject());
            return (Task*)fHeap.ExtractMin()->GetEnclosingObject();//从堆中取出第一个任务返回
        }
		//如果堆中有任务，但是尚未到执行时间，计算需要等待的时间
        //if there is an element waiting for a timeout, figure out how long we should wait.
        SInt64 theTimeout = 0;
        if (fHeap.PeekMin() != NULL)
            theTimeout = fHeap.PeekMin()->GetValue() - theCurrentTime;
        Assert(theTimeout >= 0);
        
        //
        // Make sure we can't go to sleep for some ridiculously short
        // period of time
        // Do not allow a timeout below 10 ms without first verifying reliable udp 1-2mbit live streams. 
        // Test with streamingserver.xml pref reliablUDP printfs enabled and look for packet loss and check client for  buffer ahead recovery.
	    if (theTimeout < 10) 
           theTimeout = 10;
            
        //wait...
		//如果任务队列为空，就等待theTimeout时间后从堆中取出任务返回;
		//如果任务队列不为空，就不等待，直接取队列中的任务;
        OSQueueElem* theElem = fTaskQueue.DeQueueBlocking(this, (SInt32) theTimeout);
        if (theElem != NULL)
        {    
            if (TASK_DEBUG) qtss_printf("TaskThread::WaitForTask found signal-task=%s thread %p fTaskQueue.GetLength(%"_U32BITARG_") taskElem = %p enclose=%p\n", ((Task*)theElem->GetEnclosingObject())->fTaskName,  (void *) this, fTaskQueue.GetQueue()->GetLength(), (void *)  theElem,  (void *)theElem->GetEnclosingObject() );
            return (Task*)theElem->GetEnclosingObject();
        }

        //
        // If we are supposed to stop, return NULL, which signals the caller to stop
        if (OSThread::GetCurrent()->IsStopRequested())
            return NULL;
    }   
}

3.1 Run()

virtual SInt64 Run() = 0;

3.2 Signal()

 void  Signal(EventFlags eventFlags);

【Darwin学习笔记】之TaskThread

标签：darwin

原文地址：http://blog.csdn.net/longlong530/article/details/43226999