[LM3S CORTEX-M3] how do i set irq handler with keil rtx

I have problem in using isr_evt_set
interrup handler sent event to task with isr_evt_set
but task did not receive event or consumed much time

LM3S Luminary chip has NVIC
and I didnt enable interrupt in user mode

at NVIC How do I set irq-handler with keil rtx
is it reserved sections for nvic handler?
does it need irq stack?

at startup code

export __Vectors
__Vectors
    ...
    dcd irq1handler
    dcd irq2handler
    ...

at task

void irq2handler(void) __irq {
  isr_evt_set(INT_SIGNAL, handler_task);
}

__task void handler_task(void) {
  while(1) {
    os_evt_wait_or (INT_SIGNAL, 0xffff);
    do_start_handler();
  }
}

irq2handler work with privilege mode but
do_start_handler is not working

help me..