Fatal error: Call to undefined function cache_users()

I just updated this morning.. everything seems fine..

But when I clicked on the users in admin panel.

Fatal error: Call to undefined function cache_users() in /*****/html/wp-includes/user.php on line 562

I got such fatal error.. what I do now?? please help!

———-
this is part of the script near line 562.. By the way, I didn’t edit any script at all.

if ( ‘all_with_meta’ == $this->query_vars[‘fields’] ) {
cache_users( $this->results );

$r = array();
foreach ( $this->results as $userid )
$r[ $userid ] = new WP_User( $userid, ”, $this->query_vars[‘blog_id’] );

$this->results = $r;
}
}