Re: [Xenomai-help] RT-Socket-CAN bus error handling (was CAN errors and real-time behaviour (IRQ raise forever and may lock system))

[Wolfgang Grandegger <wg@domain.hid>]

Sebastian Smolorz wrote:
> Sebastian Smolorz wrote:
>> Hi Jan,
>>
>> Jan Kiszka wrote:
>>> Wolfgang Grandegger wrote:
>>>> you know, on the SJA1000 the bus error interrupt can result in high
>>>> error interrupt rates and even hang the system on slow processors. Just
>>>> unplugging the CAN cable can cause such interrupt flooding. This
>>>> problem
>>>>
>>>> popped up again recently and Sebastian proposed:
>>>>> Last summer we had a discussion about the BEI issue on the
>>>>> socketcan-ML. Two additional handling policies popped up:
>>>>> 1. The interface could restart itself after an amount of BEIs, thus
>>>>>    taking responsibility from the user application.
>>>>> 2. The BEI could be completely disabled if no one is interested in
>>>>>    this ype of error frame.
>>>> As 2. is also my preferred solution, I have implemented it. The only
>>>> downside is that you do not see the error counter increasing when
>>>> /proc/rtcan/devices is inspected. We also discussed 1., but
>>>> RT-Socket-CAN does not restart the CAN controller by purpose and just
>>>> stoppping it requires user intervention.
>>> And if there is someone listening, how is the flooding issue on cable
>>> unplug etc. solved by option 2?
>> Hm, maybe we could implement 1 additionally (but without automatical
>> restart)?
> 
> A more precise suggestion: What about letting BEIs appear until passive mode 
> is reached and if the TX error counter doesn't count up any more (indication 
> of start-up situation discovered by the SJA1000) the driver ceases to read 
> out ECC any further (thanks Stephane for the hint). The controller would be 
> still operating but not reporting BEIs any more. There has to be some 
> mechanism to let BEIs through after the situation has normalized. Maybe the 
> driver could check inside the interrupt handler if active mode was reached 
> again after the above situation occured.

Well, this is rather sophisticated and needs some more careful 
evaluation. We might also reach the passive level slowly without 
flooding. Furthermore, the method should also be applicable for other 
controllers.

Let's implement 1. and downscaled printk and wait for the users reaction 
, see also my other mail. Then we should bring up this discussion again 
on the Socket-CAN-ML to negotiate a common solution.

OK?

Wolfgang.

>