qemu iohandler

io线程和main线程的区别在于，io线程进行了初始化封装，比如设置关心的文件描述符事件

void qemu_set_fd_handler(int fd,
                         IOHandler *fd_read,
                         IOHandler *fd_write,
                         void *opaque)
{
    iohandler_init();
    aio_set_fd_handler(iohandler_ctx, fd, false,
                       fd_read, fd_write, NULL, opaque);
}

static void iohandler_init(void)
{
    if (!iohandler_ctx) {
        iohandler_ctx = aio_context_new(&error_abort);
    }
}

qemu_set_fd_handler函数是给io线程设置文件描述符事件观察，只是对aio_set_fd_handler做了简单的封装。

iothread的启动

static void *iothread_run(void *opaque)
{
    IOThread *iothread = opaque;

    rcu_register_thread();

    my_iothread = iothread;
    qemu_mutex_lock(&iothread->init_done_lock);
    iothread->thread_id = qemu_get_thread_id();
    qemu_cond_signal(&iothread->init_done_cond);
    qemu_mutex_unlock(&iothread->init_done_lock);

    while (iothread->running) {
        aio_poll(iothread->ctx, true);

        if (atomic_read(&iothread->worker_context)) {
            GMainLoop *loop;

            g_main_context_push_thread_default(iothread->worker_context);
            iothread->main_loop =
                g_main_loop_new(iothread->worker_context, TRUE);
            loop = iothread->main_loop;

            g_main_loop_run(iothread->main_loop);
            iothread->main_loop = NULL;
            g_main_loop_unref(loop);

            g_main_context_pop_thread_default(iothread->worker_context);
        }
    }

    rcu_unregister_thread();
    return NULL;
}