Re: [PATCH] Allow changing CPU affinity of RT kernel tasks

[Richard Weinberger <richard@sigma-star.at>]

On Montag, 26. Jänner 2026 15:28 'Jan Kiszka' via upstream wrote:
> This is one issue with setting the affinity "from outside",
> asynchronously. The other is that it will always imply a migration of
> the kernel task, thus a phase of non-RT. If someone forgets about this
> and sets the affinity at the wrong time, it can ruin RT workloads.

I assumed this is known and expected since changing the CPU affinity of userspace
tasks as the same implications.

> This tuning gap for RTDM task is rather old. I was already considering
> to add an explicit affinity API to RTDM to set this from the driver.
> That would allow to set the affinity early, right after task creation
> and before the driver signals it is ready. Risk of such an interface is
> that people start to hard-code the affinity into the drivers, rather
> than making it configurable to userspace.

Well, the goal of my patch is improving the situation to match userspace
semantics.
People expect that sched_setaffinity() kinda works.

Thanks,
//richard

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