Re: Controlling cpu for interrupts

[Per Oberg <pero@wolfram.com>]

----- Den 10 jun 2025, på kl 16:09, Jan Kiszka jan.kiszka@siemens.com skrev:

>> Hi
>> I have a setup with
>> - Xenomai 3.1
>> - Linux 4.14 ish
> Ouch - dead horse (kernel) warning!

Thanks, yes, I know. I am currently debugging an older setup.


>> - RT Net e1000e + igb
>> - Peak PCAN
> Standard Linux driver for CAN, right? This is at least my interpretation
> based on the irq names below.

No, actually not. I should have said. It's the Peak PCAN xenomai driver

>> When I look closely on the rt-threads I can see that the IRQ from the CAN seems
>> to be coming in on certain cores, but now always the same.
>>
>> Here is an example of my ../xenomai/irq file:
>>
>>   IRQ         CPU0        CPU1        CPU2        CPU3
>>    18:           0           0           0   130419960         pcan pcan pcan pcan
>>    pcan pcan
>>    19:    88638780           0           0           0         pcan pcan pcan pcan
>>   127:        3215           0           0           0         rteth0-TxRx-0

>> Thus, for this case it seems like IRQ19 is handled by CPU0 while IRQ18 is
>> handled on CPU3
>>
>> What is the heuristics, if any, used for decing this ?
>>
> /proc/irq/*/smp_affinity apply here, at least for standard IRQs. If the
> mask is containing more than one core, it's up to the IRQ controllers
> and CPUs who will take an event first.

Thanks, what would be the corresponding place to look for the RTDM stuff ? 

> Jan

Thanks
Per Öberg

> --
> Siemens AG, Foundational Technologies
> Linux Expert Center