第九步：tracker_service_init函数分析（part 2)

main
    |-----......
    |-----socketServer
    |-----tcpsetserveropt
    |-----daemon_init
    |-----tracker_service_init
    |-----.....

g_thread_data = (struct tracker_thread_data *)malloc(sizeof( \
                struct tracker_thread_data) * g_work_threads)

为全局g_thread_data分配空间，g_thread_data指向的也是一段连续内存，连续内存按照tracker_thread_data对象的个数进行划分

g_tracker_thread_count = 0;
    pDataEnd = g_thread_data + g_work_threads;
    for (pThreadData=g_thread_data; pThreadData<pDataEnd; pThreadData++)
    {
        pThreadData->ev_base = event_base_new();//创建eventbase
        if (pThreadData->ev_base == NULL)
        {
            result = errno != 0 ? errno : ENOMEM;
            logError("file: "__FILE__", line: %d, " \
                "event_base_new fail.", __LINE__);
            return result;
        }

        if (pipe(pThreadData->pipe_fds) != 0)//创建管道
        {
            result = errno != 0 ? errno : EPERM;
            logError("file: "__FILE__", line: %d, " \
                "call pipe fail, " \
                "errno: %d, error info: %s", \
                __LINE__, result, STRERROR(result));
            break;
        }

        if ((result=set_nonblock(pThreadData->pipe_fds[0])) != 0)//设置非阻塞
        {
            break;
        }

        if ((result=pthread_create(&tid, &thread_attr, \//创建工作线程
            work_thread_entrance, pThreadData)) != 0)
        {
            logError("file: "__FILE__", line: %d, " \
                "create thread failed, startup threads: %d, " \
                "errno: %d, error info: %s", \
                __LINE__, g_tracker_thread_count, \
                result, STRERROR(result));
            break;
        }
        else //创建线程成功
        {
            if ((result=pthread_mutex_lock(&tracker_thread_lock)) != 0)//加锁
            {
                logError("file: "__FILE__", line: %d, " \
                    "call pthread_mutex_lock fail, " \
                    "errno: %d, error info: %s", \
                    __LINE__, result, STRERROR(result));
            }
            g_tracker_thread_count++; //修改全局线程数目，这里加锁是为了防止该变量在其他线程中被修改
            if ((result=pthread_mutex_unlock(&tracker_thread_lock)) != 0)
            {
                logError("file: "__FILE__", line: %d, " \
                    "call pthread_mutex_lock fail, " \
                    "errno: %d, error info: %s", \
                    __LINE__, result, STRERROR(result));
            }
        }
    }

该段代码在tracke_service_init函数中初始化了全局g_thread_data对象，包括为每个tracker_thread_data对象中的eventbase初始化，为每个tracker_thread_data对象中的pipe初始化，为每个tracker_thread_data对象创建一个工作线程，修改全局g_tracker_thread_count工作线程记录数变量

下面介绍work_thread_entrance函数，该函数是工作线程的入口函数

static void *work_thread_entrance(void* arg)
{
    int result;
    struct tracker_thread_data *pThreadData;
    struct event ev_notify;//创建一个event

    pThreadData = (struct tracker_thread_data *)arg;
    do
    {
        event_set(&ev_notify, pThreadData->pipe_fds[0], \  //设定event监听管道pipe_fds[0]
            EV_READ | EV_PERSIST, recv_notify_read, NULL);
        if ((result=event_base_set(pThreadData->ev_base, &ev_notify)) != 0)//邦定event到event_base
        {
            logCrit("file: "__FILE__", line: %d, " \
                "event_base_set fail.", __LINE__);
            break;
        }
        if ((result=event_add(&ev_notify, NULL)) != 0)
        {
            logCrit("file: "__FILE__", line: %d, " \
                "event_add fail.", __LINE__);
            break;
        }

        while (g_continue_flag)
        {
            event_base_loop(pThreadData->ev_base, 0);
        }
    } while (0);

    event_base_free(pThreadData->ev_base);

    if ((result=pthread_mutex_lock(&tracker_thread_lock)) != 0)
    {
        logError("file: "__FILE__", line: %d, " \
            "call pthread_mutex_lock fail, " \
            "errno: %d, error info: %s", \
            __LINE__, result, STRERROR(result));
    }
    g_tracker_thread_count--;
    if ((result=pthread_mutex_unlock(&tracker_thread_lock)) != 0)
    {
        logError("file: "__FILE__", line: %d, " \
            "call pthread_mutex_lock fail, " \
            "errno: %d, error info: %s", \
            __LINE__, result, STRERROR(result));
    }

    return NULL;
}

在该函数中，要完成以下工作
（1） 执行event_set关联event到pipe_fds[0]，监听EV_READ与EV_PERSIST事件
（2） 执行event_add,把event绑定到eventbase上
（3） 执行event_add函数
（4） 执行event_base_loop函数，开始event循环

这样，线程开始监听pipe_fds[0]上的EV_READ与EV_PERSIST事件，当事件被触发后，调用事件处理函数recv_notify_read，该函数将在下一节进行分析