rt_can_write内_can_int_tx死循环是怎么回事？

环境：STM32f407 时钟频率168M CAN波特率1M
can配置如下：

•     drv_can->CanHandle.Init.timeTriggeredMode = DISABLE;
  
•     drv_can->CanHandle.Init.AutoBusOff = ENABLE;
  
•     drv_can->CanHandle.Init.AutoWakeUp = DISABLE;
  
•     drv_can->CanHandle.Init.AutoRetransmission = DISABLE;
  
•     drv_can->CanHandle.Init.ReceiveFifoLocked = DISABLE;
  
•     drv_can->CanHandle.Init.TransmitFifoPriority = ENABLE;
  

问题：
接了can设备时，使用正常
开发板拔掉can总线线后，或can设备不通电时，一直在这个函数内死循环。

• rt_inline int _can_int_tx(struct rt_can_device *can, const struct rt_can_msg *data, int msgs)
  
• {
  
•     int size;
  
•     struct rt_can_tx_fifo *tx_fifo;
  
• 
  
•     RT_ASSERT(can != RT_NULL);
  
• 
  
•     size = msgs;
  
•     tx_fifo = (struct rt_can_tx_fifo *) can->can_tx;
  
•     RT_ASSERT(tx_fifo != RT_NULL);
  
• 
  
•     while (msgs)
  
•     {
  
•         rt_base_t level;
  
•         rt_uint32_t no;
  
•         rt_uint32_t result;
  
•         struct rt_can_sndbxinx_list *tx_tosnd = RT_NULL;
  
• 
  
•         rt_sem_take(&(tx_fifo->sem), RT_WAITING_FOREVER);
  
•         level = rt_hw_interrupt_disable();
  
•         tx_tosnd = rt_list_entry(tx_fifo->freelist.next, struct rt_can_sndbxinx_list, list);
  
•         RT_ASSERT(tx_tosnd != RT_NULL);
  
•         rt_list_remove(&tx_tosnd->list);
  
•         rt_hw_interrupt_enable(level);
  
• 
  
•         no = ((rt_uint32_t)tx_tosnd - (rt_uint32_t)tx_fifo->buffer) / sizeof(struct rt_can_sndbxinx_list);
  
•         tx_tosnd->result = RT_CAN_SND_RESULT_WAIT;
  
•         if (can->ops->sendmsg(can, data, no) != RT_EOK)
  
•         {//一直进入此条件内
  
• 
  
•             /* send failed. */
  
•             level = rt_hw_interrupt_disable();
  
•             rt_list_insert_after(&tx_fifo->freelist, &tx_tosnd->list);
  
•             rt_hw_interrupt_enable(level);
  
•             rt_sem_release(&(tx_fifo->sem));
  
• 
  
•             continue;
  
•         }
  
• 
  
•         can->status.sndchange = 1;
  
•         rt_completion_wait(&(tx_tosnd->completion), RT_WAITING_FOREVER);
  
• 
  
•         level = rt_hw_interrupt_disable();
  
•         result = tx_tosnd->result;
  
•         if (!rt_list_isempty(&tx_tosnd->list))
  
•         {
  
•             rt_list_remove(&tx_tosnd->list);
  
•         }
  
•         rt_list_insert_before(&tx_fifo->freelist, &tx_tosnd->list);
  
•         rt_hw_interrupt_enable(level);
  
•         rt_sem_release(&(tx_fifo->sem));
  
• 
  
•         if (result == RT_CAN_SND_RESULT_OK)
  
•         {
  
•             level = rt_hw_interrupt_disable();
  
•             can->status.sndpkg++;
  
•             rt_hw_interrupt_enable(level);
  
• 
  
•             data ++;
  
•             msgs -= sizeof(struct rt_can_msg);
  
•             if (!msgs) break;
  
•         }
  
•         else
  
•         {
  
•             level = rt_hw_interrupt_disable();
  
•             can->status.dropedsndpkg++;
  
•             rt_hw_interrupt_enable(level);
  
•             break;
  
•         }
  
•     }
  
• 
  
•     return (size - msgs);
  
• }