QEMU中CLOCK的初始化

1. QEMUTimerList的結構體 

struct QEMUTimerList {
    QEMUClock *clock;           //timer的鏈表會對應一個qemuclock
    QemuMutex active_timers_lock;
    QEMUTimer *active_timers;
    QLIST_ENTRY(QEMUTimerList) list;
    QEMUTimerListNotifyCB *notify_cb;//cb函數
    void *notify_opaque;

    /* lightweight method to mark the end of timerlist's running */
    QemuEvent timers_done_ev;
};

2.qemu_init_main_loop 函數分析

int qemu_init_main_loop(Error **errp)
{
    int ret;
    GSource *src;
    Error *local_error = NULL;

    init_clocks(qemu_timer_notify_cb);

    ret = qemu_signal_init();
    if (ret) {
        return ret;
    }

    qemu_aio_context = aio_context_new(&local_error);
    if (!qemu_aio_context) {
        error_propagate(errp, local_error);
        return -EMFILE;
    }
    qemu_notify_bh = qemu_bh_new(notify_event_cb, NULL);
    gpollfds = g_array_new(FALSE, FALSE, sizeof(GPollFD));
    src = aio_get_g_source(qemu_aio_context);
    g_source_set_name(src, "aio-context");
    g_source_attach(src, NULL);
    g_source_unref(src);
    src = iohandler_get_g_source();
    g_source_set_name(src, "io-handler");
    g_source_attach(src, NULL);
    g_source_unref(src);
    return 0;
}

2.1 初始化時鐘 init_clocks

void init_clocks(QEMUTimerListNotifyCB *notify_cb)
{
    QEMUClockType type;
    for (type = 0; type < QEMU_CLOCK_MAX; type++) {
        qemu_clock_init(type, notify_cb);
    }
}

2.1.1 qemu_clock_init創建每一種類型的CLOCK進行初始化

static void qemu_clock_init(QEMUClockType type, QEMUTimerListNotifyCB *notify_cb)
{
    QEMUClock *clock = qemu_clock_ptr(type);
    /*確保這個類型的clock沒有被初始化，若被初始化了，則直接報錯退出*/
    /* Assert that the clock of type TYPE has not been initialized yet. */
    assert(main_loop_tlg.tl[type] == NULL);
    /*對QEMUClock中的成員變量初始化*/
    clock->type = type;                 
    clock->enabled = (type == QEMU_CLOCK_VIRTUAL ? false : true);
    clock->last = INT64_MIN;
    /*初始化這個類型的clock的timerlist鏈表*/
    QLIST_INIT(&clock->timerlists);
    /*初始化notifier的鏈表*/
    notifier_list_init(&clock->reset_notifiers);
    main_loop_tlg.tl[type] = timerlist_new(type, notify_cb, NULL);
}

 2.1.2創建每一個類型的CLOCK的qemutimerlist鏈表，並完成元素的初始化

QEMUTimerList *timerlist_new(QEMUClockType type,
                             QEMUTimerListNotifyCB *cb,
                             void *opaque)
{
    QEMUTimerList *timer_list;
    QEMUClock *clock = qemu_clock_ptr(type);

    timer_list = g_malloc0(sizeof(QEMUTimerList));
    qemu_event_init(&timer_list->timers_done_ev, true);
    timer_list->clock = clock;
    timer_list->notify_cb = cb;
    timer_list->notify_opaque = opaque;
    qemu_mutex_init(&timer_list->active_timers_lock);
    QLIST_INSERT_HEAD(&clock->timerlists, timer_list, list);
    return timer_list;
}

 2.1.3使用windowsAPI爲qemutimerlist創建無名事件對象

/**初始化事件/
void qemu_event_init(QemuEvent *ev, bool init)
{
    /* Manual reset.  */
    /*初始狀態爲有信號狀態*/
    ev->event = CreateEvent(NULL, TRUE, TRUE, NULL);
    ev->value = (init ? EV_SET : EV_FREE);
    ev->initialized = true;
}

3. 總體結構關係圖