the cached data are referenced by their ids -> $rcache->data[$table][$id], $rcache->data[$table] is an associative array.
but some php native functions used to manage array data return indexed arrays. This is the case of the array_shift function.

the new rcache_set function has corrupted some cached data of our moodle making the script to enter in an infinite loop in the lib/accesslib.php - get_parent_cats function.

the problem is coming from this lines :

function rcache_set($table, $id, $rec) {
    global $CFG, $MCACHE, $rcache;

    if ($CFG->cachetype === 'internal') {
        if (!isset($rcache->data[$table])) {
            $rcache->data[$table] = array();
        }
        if (!isset($rcache->data[$table][$id]) and count($rcache->data[$table]) > $CFG->intcachemax) {
            array_shift($rcache->data[$table]);
        }
        $rcache->data[$table][$id] = clone($rec);

to resolve the problem we have to make our own array_shift function or replace the array_shift($rcache->data[$table]); line by something like :

$keys = array_keys($rcache->data[$table]);
$firstkey = $keys[0];
unset($rcache->data[$table][$firstkey]);

hope that's help