STM32F407 FreeRTOS 中断中发送信号量切换上下文差别

/**
  * @brief  This function handles CAN1 TX request.
  * @param  None
  * @retval None
  */
void CAN1_TX_IRQHandler(void)
{
    static portBASE_TYPE xHigherPriorityTaskWoken;
    xHigherPriorityTaskWoken = pdFALSE;

    if (CAN_GetITStatus(CAN1, CAN_IT_TME))
    {
        // 给CAN发送任务发送信号量
        xSemaphoreGiveFromISR(CAN_TxSemaphore, &xHigherPriorityTaskWoken);
        portYIELD_FROM_ISR(xHigherPriorityTaskWoken);   // 切换上下文，否者实时性变差
        
        // 清除中断标志
        CAN_ClearITPendingBit(CAN1, CAN_IT_TME);
    }
}