使用Cube库，FreeRTOS，CAN中断接收
Cube Can 中断服务函数如下：

1. static HAL_StatusTypeDef CAN_Receive_IT(CAN_HandleTypeDef* hcan, uint8_t FIFONumber)
   
2. {
   
3.   /* Get the Id */
   
4.   hcan->pRxMsg->IDE = (uint8_t)0x04 & hcan->Instance->sFIFOMailBox[FIFONumber].RIR;
   
5.   if (hcan->pRxMsg->IDE == CAN_ID_STD)
   
6.   {
   
7.     hcan->pRxMsg->StdId = 0x000007FFU & (hcan->Instance->sFIFOMailBox[FIFONumber].RIR >> 21U);
   
8.   }
   
9.   else
   
10.   {
    
11.     hcan->pRxMsg->ExtId = 0x1FFFFFFFU & (hcan->Instance->sFIFOMailBox[FIFONumber].RIR >> 3U);
    
12.   }
    
13.   
    
14.   hcan->pRxMsg->RTR = (uint8_t)0x02 & hcan->Instance->sFIFOMailBox[FIFONumber].RIR;
    
15.   /* Get the DLC */
    
16.   hcan->pRxMsg->DLC = (uint8_t)0x0F & hcan->Instance->sFIFOMailBox[FIFONumber].RDTR;
    
17.   /* Get the FIFONumber */
    
18.   hcan->pRxMsg->FIFONumber = FIFONumber;
    
19.   /* Get the FMI */
    
20.   hcan->pRxMsg->FMI = (uint8_t)0xFF & (hcan->Instance->sFIFOMailBox[FIFONumber].RDTR >> 8U);
    
21.   /* Get the data field */
    
22.   hcan->pRxMsg->Data[0U] = (uint8_t)0xFF & hcan->Instance->sFIFOMailBox[FIFONumber].RDLR;
    
23.   hcan->pRxMsg->Data[1U] = (uint8_t)0xFF & (hcan->Instance->sFIFOMailBox[FIFONumber].RDLR >> 8U);
    
24.   hcan->pRxMsg->Data[2U] = (uint8_t)0xFF & (hcan->Instance->sFIFOMailBox[FIFONumber].RDLR >> 16U);
    
25.   hcan->pRxMsg->Data[3U] = (uint8_t)0xFF & (hcan->Instance->sFIFOMailBox[FIFONumber].RDLR >> 24U);
    
26.   hcan->pRxMsg->Data[4U] = (uint8_t)0xFF & hcan->Instance->sFIFOMailBox[FIFONumber].RDHR;
    
27.   hcan->pRxMsg->Data[5U] = (uint8_t)0xFF & (hcan->Instance->sFIFOMailBox[FIFONumber].RDHR >> 8U);
    
28.   hcan->pRxMsg->Data[6U] = (uint8_t)0xFF & (hcan->Instance->sFIFOMailBox[FIFONumber].RDHR >> 16U);
    
29.   hcan->pRxMsg->Data[7U] = (uint8_t)0xFF & (hcan->Instance->sFIFOMailBox[FIFONumber].RDHR >> 24U);
    
30.   /* Release the FIFO */
    
31.   /* Release FIFO0 */
    
32.   if (FIFONumber == CAN_FIFO0)
    
33.   {
    
34.     __HAL_CAN_FIFO_RELEASE(hcan, CAN_FIFO0);
    
35.    
    
36.     /* Disable FIFO 0 message pending Interrupt */
    
37.     __HAL_CAN_DISABLE_IT(hcan, CAN_IT_FMP0);
    
38.   }
    
39.   /* Release FIFO1 */
    
40.   else /* FIFONumber == CAN_FIFO1 */
    
41.   {
    
42.     __HAL_CAN_FIFO_RELEASE(hcan, CAN_FIFO1);
    
43.    
    
44.     /* Disable FIFO 1 message pending Interrupt */
    
45.     __HAL_CAN_DISABLE_IT(hcan, CAN_IT_FMP1);
    
46.   }
    
47.   
    
48.   if(hcan->State == HAL_CAN_STATE_BUSY_RX)
    
49.   {   
    
50.     /* Disable Error warning, Error passive, Bus-off, Last error code
    
51.        and Error Interrupts */
    
52.     __HAL_CAN_DISABLE_IT(hcan, CAN_IT_EWG |
    
53.                                CAN_IT_EPV |
    
54.                                CAN_IT_BOF |
    
55.                                CAN_IT_LEC |
    
56.                                CAN_IT_ERR);
    
57.   }
    
58.   
    
59.   if(hcan->State == HAL_CAN_STATE_BUSY_TX_RX)
    
60.   {
    
61.     /* Disable CAN state */
    
62.     hcan->State = HAL_CAN_STATE_BUSY_TX;
    
63.   }
    
64.   else
    
65.   {
    
66.     /* Change CAN state */
    
67.     hcan->State = HAL_CAN_STATE_READY;
    
68.   }
    
69. 
    
70.   /* Receive complete callback */
    
71.   HAL_CAN_RxCpltCallback(hcan);
    
72. 
    
73.   /* Return function status */
    
74.   return HAL_OK;
    
75. }

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我的应用代码：

1. static uint8_t can_rec_ack(uint32_t millisec)
   
2. {
   
3.     if(osSemaphoreWait(can_xSemaphore, millisec) == osOK)
   
4.         return 1;
   
5.     else
   
6.         return 0;
   
7. }
   
8. 
   
9. uint8_t can_call(uint8_t dt, uint8_t slot)
   
10. {
    
11.     CAN_EXID_UN can_id;
    
12.     can_id.id.d_id = 0x0;
    
13.     can_id.id.dir = CAN_ID_M2S;
    
14.     can_id.id.fun = CF_CALL;
    
15.     can_id.id.type = dt;
    
16.     can_id.id.slot = slot;
    
17. 
    
18.     hcan1.pTxMsg->DLC = 1;
    
19.     hcan1.pTxMsg->Data[0] = 0xAA;
    
20.     hcan1.pTxMsg->ExtId = can_id.value;
    
21.     HAL_CAN_Receive_IT(&hcan1, CAN_FIFO0);
    
22.     if(HAL_OK == HAL_CAN_Transmit(&hcan1, 10))
    
23.     {
    
24.         if(can_rec_ack(100))
    
25.         {
    
26.             osDelay(2);
    
27.             log_printf(LOG_INFO, "CAN_RX:0x%X-0x%X,Ack:0x%X;soft_ver:%d;hw_ver:%d;build:%d\r\n",hcan1.Instance->sFIFOMailBox[0].RDLR,
    
28.             hcan1.Instance->sFIFOMailBox[0].RDHR, hcan1.pRxMsg->Data[0], hcan1.pRxMsg->Data[1], hcan1.pRxMsg->Data[2], *(uint32_t *)&hcan1.pRxMsg->Data[4]);
    
29.             return 1;
    
30.         }
    
31.         else
    
32.         {
    
33.             log_printf(LOG_ERR, "%s call dev:%d slot:%d timeout\r\n", __func__, dt, slot);
    
34.             return 0;
    
35.         }
    
36.     }
    
37.     else
    
38.     {
    
39.         log_printf(LOG_ERR, "%s send sta 0x%X\r\n", __func__, hcan1.State);
    
40.         return 0;
    
41.     }
    
42. }

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主设备呼叫从设备，从设备回复8个字节。主设备先启动接收中断，然后发出呼叫帧，马上从设备回复，HAL_CAN_RxCpltCallback函数发信号量，此时去读hcan1.pRxMsg->Data中的8个字节，发现全0，但是直接通过寄存器访问的方式去读，数据都已经收到了。加延时的话也可以从hcan1.pRxMsg->Data中读取正确的值。是哪里有cache吗？还是其他的什么原因？

我在中断服务函数的第71行代码执行之后去读hcan1.pRxMsg->Data，数据不对，那说明中断服务函数的22-29行还没生效？

问题出在信号量上了CMSIS-RTOS的osSemaphoreCreate(osSemaphore(CAN_SEM) , 1 )，创建了一个信号量，并初始化成有效，所以第一次就没收到CAN数据就进去读了