Re: sja1000 interrupt problem

[Oliver Hartkopp <socketcan@hartkopp.net>]

On 13.12.2013 11:07, Marc Kleine-Budde wrote:
> On 12/13/2013 10:38 AM, Oliver Hartkopp wrote:


>> +#if 0
>>  	u16 icr;
>>  
>>  	/* Select and clear in PITA stored interrupt */
>>  	icr = readw(chan->cfg_base + PITA_ICR);
>>  	if (icr & chan->icr_mask)
>>  		writew(chan->icr_mask, chan->cfg_base + PITA_ICR);
>> +#else
>> +	while (readw(chan->cfg_base + PITA_ICR) & chan->icr_mask)
>> +		writew(chan->icr_mask, chan->cfg_base + PITA_ICR);
>> +#endif

>>
>> This should usually not have any effect, right?
>> But what happened was a big crash after a pretty short time:
>>
>> [  760.718091] INFO: rcu_preempt self-detected stall on CPU { 1}  (t=84015 jiffies g=482 c=481 q=2688)
> 
> For me it seems that the new while loop keeps spinning and then the rcu
> subsystem detects some stalls.
> 
> Maybe it's time to get in touch with the hardware engineers at peak.
> 

I personally do not expect this to be a PEAK problem as the usual case with
mainline Linux (non -rt) works fine.

Maybe it's time to look into other implementations than PEAK/mainline ...

If they all do it the same way I would assume it's a plain -rt irq thread issue.

Regards,
Oliver