Re: [RFC PATCH] Documentation: Add managed interrupts

[John Ogness <john.ogness@linutronix.de>]

On 2026-04-13, Valentin Schneider <vschneid@redhat.com> wrote:
> On 01/04/26 13:02, Sebastian Andrzej Siewior wrote:
>> One more point: Given that isolcpus= is marked deprecated as of commit
>>    b0d40d2b22fe4 ("sched/isolation: Document isolcpus= boot parameter flags, mark it deprecated")
>>
>> and the 'managed_irq' is evaluated at device's probe time it would
>> require additional callbacks to re-evaluate the situation. Probably for
>> 'io_queue', too. Does is make sense or should we simply drop the
>> "deprecation" notice and allowing using it long term?
>
> AIUI the deprecation notice is more for isolcpus=domain, i.e. the scheduler
> part, but it's still relevant for e.g. managed_irq.

If that is the case, then the deprecation notice should explicitly
target the "domain" flag. Also note that "domain" is the default if no
flag is specified, so it is a bit messy. It is odd to deprecate a
(default) component of a feature and not have a plan how that component
will ever be removed.

The documentation of "domain" already strongly advises to use cpusets
instead. Is that not enough? If so, the deprecation should be dropped.

If there is a strong wish to remove the "domain" boot functionality,
then there should be a new boot arg that can be used for "managed_irq"
and "nohz" features, i.e. get users off the deprecated isolcpus so that
isolcpus can log deprecation notices and be removed someday.

John Ogness