浅析dbus系统loop循环中new_connection消息派发

浅析dbus系统loop循环中new_connection消息派发




main
==>_dbus_loop_run
==>_dbus_loop_iterate
==>_dbus_loop_dispatch
==>dbus_connection_dispatch // 会遍历执行&connection->filter_list链表上的所有注册函数filter->function

++>(* filter->function) (connection, message, filter->user_data);

// 暂时先看看filter->function函数什么时候注册

main
**> bus_context_new
**> process_config_first_time_only
**> setup_server
**> dbus_server_set_new_connection_function (server, // 设置回调函数

                                           new_connection_callback,
                                           context, NULL);
最后server->new_connection_function = new_connection_callback;
****> main
****> _dbus_loop_run (bus_context_get_loop (context)) // 执行context->loop为上下文的循环

****> _dbus_loop_iterate
dbus_bool_t
_dbus_loop_iterate (DBusLoop *loop,
                    dbus_bool_t block)
{
#define N_STACK_DESCRIPTORS 64
    ......
  if (loop->callbacks == NULL)
    goto next_iteration;

    if (loop->watch_count > N_STACK_DESCRIPTORS) {
      fds = dbus_new0 (DBusPollFD, loop->watch_count);
      
      while (fds == NULL)
        {
          _dbus_wait_for_memory ();
          fds = dbus_new0 (DBusPollFD, loop->watch_count);
        }
      
      watches_for_fds = dbus_new (WatchCallback*, loop->watch_count);
      while (watches_for_fds == NULL)
        {
          _dbus_wait_for_memory ();
          watches_for_fds = dbus_new (WatchCallback*, loop->watch_count);
        }
    } else {
      fds = stack_fds;
      watches_for_fds = stack_watches_for_fds;
    }
  /* fill our array of fds and watches */
  n_fds = 0;
  link = _dbus_list_get_first_link (&loop->callbacks);
  while (link != NULL)
    {
        ......
              fds[n_fds].fd = dbus_watch_get_socket (wcb->watch);
              fds[n_fds].revents = 0;
              fds[n_fds].events = 0;
              if (flags & DBUS_WATCH_READABLE)
                fds[n_fds].events |= _DBUS_POLLIN;
              if (flags & DBUS_WATCH_WRITABLE)
                fds[n_fds].events |= _DBUS_POLLOUT;
        ......
        n_ready = _dbus_poll (fds, n_fds, timeout);
        // 执行poll,监控_dbus_loop_add_watch函数登记到context->loop->callbacks上的所有watch单元对应的fd.

        // add_server_watch 或者 add_connection_watch 或者 add_babysitter_watch都将调用

        // _dbus_loop_add_watch向context->loop->callbacks追加watch单元.

    }
}
****> server_watch_callback
****> dbus_watch_handle
****> 首先请参考《浅析dbus系统watch函数是如何注册登记的》
****> socket_handle_watch // 感知client链接

****> handle_new_client_fd_and_unlock (server, client_fd)
****> (*server->new_connection_function)(server, connection, new_connection_data)
**> new_connection_callback
**> bus_connections_setup_connection
**> bus_dispatch_add_connection
dbus_bool_t
bus_dispatch_add_connection (DBusConnection *connection)
{
  if (!dbus_connection_add_filter (connection,
                                   bus_dispatch_message_filter,
                                   NULL, NULL)) // 调用_dbus_list_append (&connection->filter_list, filter)

    return FALSE;
  
  return TRUE;
}

那什么时候引用connection->filter_list链表中登记注册的数据们呢,下面让我们来看看:
main
==>_dbus_loop_run
==>_dbus_loop_iterate
+++++++++++++++++++++++++++++++++++++++++++++
==>bus_connections_setup_connection // 建立新的connection链接

==>_dbus_loop_queue_dispatch // 执行connection->filter_list链表上挂接的所有等待截获新建connection链接的信息的callback们.

dbus_bool_t
_dbus_loop_queue_dispatch (DBusLoop *loop,
                           DBusConnection *connection)
{
  if (_dbus_list_append (&loop->need_dispatch, connection))
    {
      dbus_connection_ref (connection);
      return TRUE;
    }
  else
    return FALSE;
}
==>_dbus_loop_dispatch (loop)
dbus_bool_t
_dbus_loop_dispatch (DBusLoop *loop)
{
    ......
  while (loop->need_dispatch != NULL)
    {
      DBusConnection *connection = _dbus_list_pop_first (&loop->need_dispatch); // 弹出第一个有效待处理connection.

      
      while (TRUE)
        {
          DBusDispatchStatus status;
          
          status = dbus_connection_dispatch (connection); // 执行处理

        ....
        }
    ....
    }
    ......
}
==>_dbus_loop_dispatch
==>status = dbus_connection_dispatch (connection);
==>dbus_connection_dispatch
==>filter->function = bus_dispatch_message_filter
==>bus_dispatch_message_filter
==>bus_dispatch
==>bus_driver_handle_message
static struct
{
  const char *name;
  const char *in_args;
  const char *out_args;
  dbus_bool_t (* handler) (DBusConnection *connection,
                           BusTransaction *transaction,
                           DBusMessage *message,
                           DBusError *error);
} message_handlers[] = {
  { "Hello",
    "",
    DBUS_TYPE_STRING_AS_STRING,
    bus_driver_handle_hello },
    ......
 };
==>bus_driver_handle_hello
==>bus_connection_complete
==>d->policy = bus_context_create_client_policy (d->connections->context,
                                                connection,
                                                error);
==>bus_context_create_client_policy
==>bus_policy_create_client_policy(context->policy, connection, error)
==>add_list_to_client (&policy->default_rules, client)
==>add_list_to_client (&policy->at_console_true_rules, client)
==>add_list_to_client (&policy->mandatory_rules, client)