[question] possible cause for vector XL_ERR_INVALID_HANDLE

[danielhrisca]

Describe the bug

I setup several buses on a VX1135 device

Each bus is being handled in a dedicated Python process.
I am able to start the buses and acquire CAN data, but when I want to shutdown the buses I often get this error:

Traceback (most recent call last):
  File "d:\daxil\xil\devices\can_device.py", line 1727, in _acquire
  File "d:\Tools\_venv\pyvenv_daxil2_Python310_x64\lib\site-packages\can\interfaces\vector\canlib.py", line 629, in shutdown
  File "d:\Tools\_venv\pyvenv_daxil2_Python310_x64\lib\site-packages\can\interfaces\vector\xldriver.py", line 37, in check_status_operation
can.interfaces.vector.exceptions.VectorOperationError: xlDeactivateChannel failed (XL_ERR_INVALID_HANDLE) [Error Code 155]

Do you know what can cause this?

[zariiii9003]

I think usually XL_ERR_INVALID_HANDLE occurs, when the vector device is disconnected physically.
Is the bus instantiated and shut down in the same process?
Does is really only occur during shutdown? If so, 4.2.0 suppresses VectorError during shutdown.

[danielhrisca]

Yes, the bus is completely handled in the dedicated process and the problem occurs on the shutdown call.
The VX is not disconnected, I also have a XCP connection with the VX that is running in parallel with no issues.

[zariiii9003]

Did you try 4.2? If so, did it help?

[Prindl]

I'm thinking the reason for your error during the shutdown might be that you are trying to close an already closed channel. Are you really using separate processes or are you using threads? I remember getting an error from the XL Driver Library when a thread tried to deactivate an already deactivated channel. Unless you provide more of your source it is almost impossible to tell what the cause of your issue is...

Wouldn't a possible solution be to check for an invalid port handle before calling the xlDeactivateChannel in canlib.py.

[danielhrisca]

I'm using multiprocessing.Process not threading.Thread. In the same function the bus is created, then the code runs a while loop gathering messages from the bus until a stop variable is set, and finally the bus is shut down .

I've gotten more logs from users and now I see additionally this error:

[Prindl]

So the function that you are passing to the multiprocessing.Process object creates the instance of the VectorBus? In that case I don't see why it should not work... However, when you check the documentation of the xlDriverLibrary it says the following:

XL_ERR_PORT_IS_OFFLINE: The user called a port function whose execution must be online, but the port is offline.
XL_ERR_INVALID_HANDLE: The user passed an invalid handle.

That means somewhere in your code you try to access the bus after the port was closed(xlClosePort is called in shutdown). Additionally, you seem to be trying to deactivate the channel after the port was closed and hence you get the XL_ERR_INVALID_HANDLE. All this leads me to believe, that you share a bus instance(or in terms of the xl driver library a port) between multiple threads/processes. Again, without any code it's hard to pinpoint the error...