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

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()).

-- 
Philippe.