I am referring to the book Mastering STM32 by Carmine Noviello. I came across an example code which talks about Interrupt priorities. He showed an example which is given below where he makes a low priority IRQ by EXTI15_10 which puts the ISR in a forever loop. But he also states that, if a higher priority interrupt occurs during this forever loop, the current interrupt will be suspended to serve the higher priority one. However, on trying several times with different pins, I am not able to achieve the same result, the higher priority EXTI, which is EXTI4 is not preempting EXTI15_10. I am new to STM32 and my development board is NUCLEO-F446RE.

The code :

static void MX_GPIO_Init(void)
{
  GPIO_InitTypeDef GPIO_InitStruct = {0};
/* USER CODE BEGIN MX_GPIO_Init_1 */
/* USER CODE END MX_GPIO_Init_1 */

  /* GPIO Ports Clock Enable */
  __HAL_RCC_GPIOC_CLK_ENABLE();
  __HAL_RCC_GPIOH_CLK_ENABLE();
  __HAL_RCC_GPIOA_CLK_ENABLE();
  __HAL_RCC_GPIOB_CLK_ENABLE();

  /*Configure GPIO pin Output Level */
  HAL_GPIO_WritePin(LD2_GPIO_Port, LD2_Pin, GPIO_PIN_RESET);

  /*Configure GPIO pin : B1_Pin */
  GPIO_InitStruct.Pin = GPIO_PIN_13;
  GPIO_InitStruct.Mode = GPIO_MODE_IT_RISING;
  GPIO_InitStruct.Pull = GPIO_PULLDOWN;
  HAL_GPIO_Init(GPIOC, &GPIO_InitStruct);

  GPIO_InitStruct.Pin = GPIO_PIN_4;
  GPIO_InitStruct.Mode = GPIO_MODE_IT_RISING;
  GPIO_InitStruct.Pull = GPIO_PULLDOWN;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  HAL_GPIO_Init(GPIOC,&GPIO_InitStruct);

  GPIO_InitStruct.Pin = GPIO_PIN_8;
  GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
  HAL_GPIO_Init(GPIOC, &GPIO_InitStruct);

  HAL_NVIC_SetPriority(EXTI15_10_IRQn,1,0);
  HAL_NVIC_EnableIRQ(EXTI15_10_IRQn);

  HAL_NVIC_SetPriority(EXTI4_IRQn,0,0);
  HAL_NVIC_EnableIRQ(EXTI4_IRQn);
/* USER CODE BEGIN MX_GPIO_Init_2 */
/* USER CODE END MX_GPIO_Init_2 */
}

void EXTI15_10_IRQHandler(void){
    HAL_GPIO_EXTI_IRQHandler(GPIO_PIN_13);
}

void EXTI4_IRQHandler(void){
    HAL_GPIO_EXTI_IRQHandler(GPIO_PIN_4);
}
/* USER CODE BEGIN 4 */

void HAL_GPIO_EXTI_Callback(uint16_t GPIO_Pin) {
    if (GPIO_Pin == GPIO_PIN_13) {
        blink = 1;
        while (blink) {
            HAL_GPIO_TogglePin(GPIOC, GPIO_PIN_8);
            for (volatile int i = 0; i < 100000; i++);  // Delay
        }
    }
    else{
        blink=0;
    }
}