$this->form_validation->run() is working but validation_errors() return empty string

i know there are many question regarding this problem, but this case is little different ,

i have a main contoller name Hs_controller that run through out the application and i have 2 more controller Frontend_Controller , and Admin_Controller inheriting the Hs_Controller

class Hs_Controller extends CI_Controller {

    public $data = array();

    function __construct() {

        parent::__construct();
        $this->data["errors"] = array();

        $this->data["site_name"] = config_item("site_name");
        $this->data["meta_title"] = config_item("site_name");

        $this->load->helper("form");

        $this->load->library("session");
        $this->load->library('form_validation');


    }
}

the app im creating require login on frontend section too, so i import session and form_validation library in the Hs_Controller so i could use them throughout the application,

now the login Action looks like

public function login() {

        $validation_rules = $this->user_r->rules;
        $this->form_validation->set_rules( $validation_rules );


        echo " form controllers  : <br/>";
        echo " validation :";
        var_dump($this->form_validation->run());
        echo "<br/>";

        echo " errors :";
        var_dump(validation_errors());
        echo "<br/>";

        echo " post :";
        var_dump($_POST);
        echo "<hr/>";

        if ( $this->form_validation->run() == TRUE ) {
            // we can login the user 
        }



        $this->data["subview"] =  "user/login";
        $this->load->view("_layout_modal" , $this->data );


    } 

and the respective view is like

<?php

        echo " form view  : <br/>";
        // echo " validation :";
        // var_dump($this->form_validation->run());
        // echo "<br/>";

        echo " errors :";
        var_dump(validation_errors());
        echo "<br/>";

        echo " post :";
        var_dump($_POST);
        echo "<hr/>";


?><div class="model-header">
        <h3>Login</h3>
        <p> hi user</p>
</div>

<div class="model-body"><?php 
    echo validation_errors();
    echo form_open();

        ?><ul><?php
            ?><li><label>email</label><?php echo form_input("email"); ?></li><?php
            ?><li><label>password</label><?php echo form_password("password"); ?></li><?php
            ?><li><?php echo form_submit("submit" , "log in" , 'class="btn "'); ?></li><?php

        ?></ul><?php 

    echo form_close(); 

?></div>

the $this->form_validation->run() is working perfectly, and i can also see the $_POST form the view and controller but the validation_errors() alwasy return empty string ..

what i already tested

1. validation rules are working perfectly,

2. .htaccess solution on this link also didn't work

3. $_POST is not empty, i can be access from the controller and view as describe in this link

   4. $this->form_validation->run() is also validation and working