Already logged in as xxx, when I use OAuth and Service

I have 2 website, 'connector' and 'provider'. I want to use connector get the 'user index' resource. So I opened the 'login', 'logout', 'index', create an alias "userinfo" for 'user' resource, and tested, it works well.
Then I choose 'Required authentication' : 'Consumer Key'; 'Required authorization':'Default' for 'login', 'logout', 'index'. Now I get an error: Already logged in as drupal_connector.

//...
function myservice_user(){
    //..some code here
    $service    = new MySimpleService($connector, $token, 'myservice_change_cookie_header');
    $account = array('username' => 'admin', 'password' => 'admin');
    $session_info  = $service->excute('http://provider-test.localhost/oauthlogin/api/userinfo/login',  'post', $account);
    dsm($session_info);
    $callback   = $service->excute('http://provider-test.localhost/oauthlogin/api/userinfo', 'get', $session_info);
    dsm($callback);
    $logoutinfo    = $service->excute('http://provider-test.localhost/oauthlogin/api/userinfo/logout', 'post', $account,$session_info);
    dsm($logoutinfo);
    return serialize($callback);
}

I debug the project and I found these code in the end:
service_oauth.inc line 82, user was set to consumer account

    else if ($cred == 'consumer') {
      if ($consumer->uid) {
        // This authenticates as the user who owns 'key';  It is for 2-stage 
        // OAuth and is vastly inferior to 3-stage OAuth
        global $user;
        $user = user_load($consumer->uid);
      }
    }

service.module line 352, if the callback is login, user will not set to $original_user

  //For every callback that has nothing to do with login we need to
  //set it to the original user so that they are no longer anonymous
  
  if (strpos($arg[1]['callback'], 'login') === FALSE) {
    // The account should be restored to the session's user.
    $user = $original_user;
  }

Does anyone can help me on this question? how can I get the user info by 2-legged authentication? Thanks a lot!!!