STM32 AWU RTC alarm wakes up CPU from stop mode

void RTC_EXTI_INITIAL(FunctionalState interrupt_en_or_dis)
{
 NVIC_InitTypeDef NVIC_InitStructure;
   EXTI_InitTypeDef EXTI_InitStructure; 

//-----------EXTI configuration -------------------    
   EXTI_InitStructure.EXTI_Line = EXTI_Line17;
   EXTI_InitStructure.EXTI_Mode = EXTI_Mode_Interrupt;
   EXTI_InitStructure.EXTI_Trigger = EXTI_Trigger_Rising;
   EXTI_InitStructure.EXTI_LineCmd = interrupt_en_or_dis;
   EXTI_Init(&EXTI_InitStructure); 
//------------ set up interrupt------------------- 
   NVIC_InitStructure.NVIC_IRQChannel = RTCAlarm_IRQn;//防拆
   NVIC_InitStructure.NVIC_IRQChannelPreemptionPrio rity = 0;
   NVIC_InitStructure.NVIC_IRQChannelSubPriority = 0;
   NVIC_InitStructure.NVIC_IRQChannelCmd = interrupt_en_or_dis;
   NVIC_Init(&NVIC_InitStructure);      
//------------------------------------------ 
}

void RTC_SET_ALARM(u32 sec)
{
//DEBUG_COM_STREAM("-Alarm-",NULL);
RTC_SetAlarm(RTC_GetCounter()+sec);
//DEBUG_COM_STREAM("-Alarm1-",NULL);
RTC_WaitForLastTask();
//DEBUG_COM_STREAM("-Alarm2-",NULL);
RTC_ITConfig(RTC_FLAG_ALR,ENABLE);
}
void RTC_AWU_SET(void)
{
//Enable PWR and BKP clocks (from APB1)
RCC_APB1PeriphClockCmd(RCC_APB1Periph_PWR | RCC_APB1Periph_BKP, ENABLE);
//Unlock backup domain
PWR_BackupAccessCmd(ENABLE);
RTC_ITConfig(RTC_IT_SEC, DISABLE);
RTC_SET_ALARM(5);
//PWR_BackupAccessCmd(DISABLE);
RTC_EXTI_INITIAL(ENABLE);
}

void RTCAlarm_IRQHandler(void)
{
 EXTI_ClearITPendingBit(EXTI_Line17);
//SYS.wake_id|=1<<17;
}

void RTC_IRQHandler(void)
{
  if (RTC_GetITStatus(RTC_IT_SEC) != RESET)
  {
   
    RTC_ClearITPendingBit(RTC_IT_SEC);
 
   
    RTC_WaitForLastTask();
 //TIME_COUNT=RTC_GetCounter();
 //RTC_WaitForLastTask();
  }
  if (RTC_GetITStatus(RTC_FLAG_ALR) != RESET) 
   {RTC_ClearITPendingBit(RTC_FLAG_ALR);
   RTC_WaitForLastTask();
  //SYS.wake_id|=1<<1;
   }
 
}