如何重新初始化stm32f30x计时器？

Question

当我尝试重新初始化stm32f303VB的定时器4时，不再调用中断例程。

static uint32_t delay_val;
uint8_t InitCounter(uint32_t period, uint16_t perscl, void(*inter_handler)(void)) {

      TIM_TimeBaseInitTypeDef TIM_TimeBaseInitStruct;
        NVIC_InitTypeDef NVIC_InitStructure;

        //check if the timer is occupied
      if(TIMx->CR1&TIM_CR1_CEN) {
            return 1;
        }
        //enable clock for apb1
      gint_handler = inter_handler;
        RCC_APB1PeriphClockCmd(RCC_xPeriph_TIMx,ENABLE);
        //interrupt enable
        NVIC_InitStructure.NVIC_IRQChannel = TIMx_IRQn;
        NVIC_InitStructure.NVIC_IRQChannelPreemptionPriority = 7;
        NVIC_InitStructure.NVIC_IRQChannelSubPriority = 7;
        NVIC_InitStructure.NVIC_IRQChannelCmd = ENABLE;
        NVIC_Init(&NVIC_InitStructure); 

        //deinitialize timer
        TIM_DeInit(TIMx);
        //initialize, clock frequency 72 MHz
      TIM_TimeBaseStructInit(&TIM_TimeBaseInitStruct);
      TIM_TimeBaseInitStruct.TIM_ClockDivision = 0;
        TIM_TimeBaseInitStruct.TIM_CounterMode = TIM_CounterMode_Down;
        TIM_TimeBaseInitStruct.TIM_Period = period;
        TIM_TimeBaseInitStruct.TIM_Prescaler = perscl; 
        TIM_TimeBaseInitStruct.TIM_RepetitionCounter = 0; //this parameter is only for TIM1 and TIM8
        TIM_TimeBaseInit(TIMx,&TIM_TimeBaseInitStruct);
        return 0;

}
static void Delay_decrement(void) {
    if(delay_val) {
        delay_val--;
    }
}
static void initGreenLED(void) {
    //LED3 red on PE9
    GPIO_InitTypeDef GPIO_InitStructure;
    RCC_AHBPeriphClockCmd(RCC_AHBPeriph_GPIOE,ENABLE);
    GPIO_InitStructure.GPIO_Mode    = GPIO_Mode_OUT;
    GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
    GPIO_InitStructure.GPIO_Pin     = GPIO_Pin_11;
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;   
    GPIO_Init(GPIOE, &GPIO_InitStructure);
}

void UnitTestDelay(void) {
    initGreenLED();
    Delay(1000000);
    GPIOE->ODR ^=  GPIO_Pin_11;
    Delay(1000000);

}
void StartUSCounter(void(*inter_handler)(void)) {
    InitCounter(1,72,inter_handler); 
    StartCounter();
}
void Delay(uint32_t us) {
    delay_val=us;
    StartUSCounter(Delay_decrement);
    while(delay_val);
    StopCounter();

}

void TIM4_IRQHandler(void)
{
//   UINT16 temp;
  if (TIM_GetITStatus(TIM4, TIM_IT_Update) != RESET)
  {
        TIM4->CR1 &= ~TIM_CR1_CEN;
        TIM_ClearITPendingBit(TIM4, TIM_IT_Update);
        if(gint_handler)  {
            (*gint_handler)();
        }
        TIM4->CR1 |= TIM_CR1_CEN;
  }

}
int main(void)
{
    while(1) {
        UnitTestDelay();
    }
}

UnitTestDelay的第一次调用正确地减少delay_val，在Timer被禁用后，下一次初始化不成功，TIM4_IRQHandler永远不再被调用。为什么以及如何正确地重新初始化计时器？