acquireLock example

 else {
                    $this->valid = true;
                }
                if ($this->valid && $_template->caching == Smarty::CACHING_LIFETIME_CURRENT && $_template->cache_lifetime >= 0 && time() > ($this->timestamp + $_template->cache_lifetime)) {
                    // lifetime expired                     $this->valid = false;
                }
                if ($this->valid || !$_template->smarty->cache_locking) {
                    break;
                }
                if (!$this->handler->locked($_template->smarty, $this)) {
                    $this->handler->acquireLock($_template->smarty, $this);
                    break 2;
                }
            }
            if ($this->valid) {
                if (!$_template->smarty->cache_locking || $this->handler->locked($_template->smarty, $this) === null) {
                    // load cache file for the following checks                     if ($smarty->debugging) {
                        Smarty_Internal_Debug::start_cache($_template);
                    }
                    if($handler->process($_template, $this) === false) {
                        $this->valid = false;
                    }