Re: [PATCH v2 1/3] cobalt: Prepare for new signature of __request_percpu_irq() in 6.19

On 25.02.26 17:43, Philippe Gerum wrote:
> Jan Kiszka <[email protected]> writes:
> 
>> On 24.02.26 22:11, Jan Kiszka wrote:
>>> On 20.02.26 12:27, Florian Bezdeka wrote:
>>>> The signature of __request_percpu_irq() got one additional affinity
>>>> parameter in 6.19 and 7.0 will remove the function entirely.
>>>>
>>>> Dovetail 6.19 will introduce a new dovetail specific service called
>>>> request_percpu_irq_affinity_flags() that allows us to set flags and
>>>> affinity at the same time.
>>>>
>>>> It might happen that older Dovetail versions get the new API via
>>>> backports, so the re-#definement for older kernels might get
>>>> obsolete earlier than dropping support for Dovetail < 6.19.
>>>>
>>>> Signed-off-by: Florian Bezdeka <[email protected]>
>>>> ---
>>>>  include/cobalt/kernel/dovetail/pipeline/irq.h      | 6 ++++++
>>>>  include/cobalt/kernel/dovetail/pipeline/pipeline.h | 9 ++++-----
>>>>  include/cobalt/kernel/dovetail/pipeline/sirq.h     | 9 ++++-----
>>>>  kernel/cobalt/dovetail/tick.c                      | 8 ++++----
>>>>  4 files changed, 18 insertions(+), 14 deletions(-)
>>>>
>>>> diff --git a/include/cobalt/kernel/dovetail/pipeline/irq.h b/include/cobalt/kernel/dovetail/pipeline/irq.h
>>>> index 55d9b8ff17cd08e5e8c09aec393a1e23736c1b76..df0b8ceb05c25d655a331d238e7ef8ac8a6afeea 100644
>>>> --- a/include/cobalt/kernel/dovetail/pipeline/irq.h
>>>> +++ b/include/cobalt/kernel/dovetail/pipeline/irq.h
>>>> @@ -5,6 +5,12 @@
>>>>  #ifndef _COBALT_KERNEL_DOVETAIL_IRQ_H
>>>>  #define _COBALT_KERNEL_DOVETAIL_IRQ_H
>>>>  
>>>> +#if LINUX_VERSION_CODE < KERNEL_VERSION(6, 19, 0)
>>>> +#define request_percpu_irq_affinity_flags(irq, handler, flags, devname,        \
>>>> +					  affinity, dev_id)                    \
>>>> +	__request_percpu_irq(irq, handler, flags, devname, dev_id)
>>>
>>> BTW, this effectively invalidates the affinity parameter. Before we
>>> could make use of it, we would have to backport the dovetail function to
>>> older kernels as well (6.1 right now).
>>>
>>
>> For the time being, I would like to have a WARN_ON_ONCE(affinity !=
>> NULL) in the wrapper so that we have a chance to detect future overuse
>> of the new API.
>>
>>> At the same time, we seem to be forced to create all the OOB interrupts
>>> on all the cores anyway, even when supported_cpus is set to a smaller
>>> set. I do not recall why that is the case, I just vaguely remember
>>> having asked this before. And as long as it is required, the new
>>> affinity parameter will remain NULL.
>>
>> Would still be interesting to recap this aspect, both for classic cobalt
>> (supported_cpus) but also the evl core (oobcpus). Even if the lock
>> contention in the absence of a global nklock is not there anymore, I
>> guess there would be value in not having to proxy the timer on cores
>> that do not host RT workload. But evl is currently requesting the proxy
>> for all cpus as well, isn't it?
> 
> Only on the evl_oob_cpus set (tick_install_proxy()).
> 

But per-cpu interrupts are requested for all cores, no?

Jan


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