Re: [cip-dev] BUG: using smp_processor_id() in preemptible [00000000] code: TCPTSK/1809

Jan Kiszka
2021-06-07T08:34:08Z

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Hi Rainer,

On 07.06.21 07:23, Rainer Kloud wrote:
> Hello Pavel,
>
>> I notice you are using -rt kernel. Do you actually need realtime
>> features?
>
> Yes, I actually need the realtime feature. I have one task which
> needs to run periodically in realtime (triggered every 10ms by an
> external IRQ).
>

Please don't forget to share your kernel config with us so that we can
make sure your use case is covered subsystem-wise in CIP. From Siemens
side, we still have room for improvements in this regard, even more on -rt.

> Jun 1 09:11:46 sicam kernel: [46802.944299] [<c062f854>] (dump_stack) from [<c03a57ec>] (check_preemption_disabled+0x110/0x114)
> Jun 1 09:11:46 sicam kernel: [46802.944316] [<c03a57ec>] (check_preemption_disabled) from [<c014163c>] (migrate_enable+0x40/0x488)
> Jun 1 09:11:46 sicam kernel: [46802.944338] [<c014163c>] (migrate_enable) from [<c053ff0c>] (ip_finish_output2+0x21c/0x460)

Migration should be on across migration-disabled sections, that's their
whole purpose. But maybe the check that preemption needs to be off when
using smp_processor_id needs relaxing to at least migration must be off.

Jan

--
Siemens AG, T RDA IOT
Corporate Competence Center Embedded Linux

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