Re: [RFC PATCH] sysfs: Add /sys/kernel/realtime entry

On Tue, Jul 14, 2026 at 01:07:18PM +0200, Sebastian Andrzej Siewior wrote:
> On 2026-07-10 18:01:20 [+0200], Florian Bezdeka wrote:
> > Depends on what you consider a valid update scenario. Updating from 6.1-
> > rt with sysfs available to something like 6.18 (no sysfs anymore) will
> > still break - as long as you do not (force) update userspace in
> > lockstep.
> 
> v6.1-RT to v6-18 no-rt will not provide the file. Also will not provide
> ARM, PowerPC or 8250-nbcon support. So it is not just that single thing
> that you "lose" if you don't apply the RT patch. It is just what you
> notice because you don't use the other things.
> 
> > I learned meanwhile that our detection moved to uname meanwhile, so this
> > is not a problem for us anymore.
> 
> Okay. So you yelled loudly that you need it, now not anymore.
> 
> So can we state that this it does not provide anything of value, is not
> considered needed and can be dropped?
> 
> Clark, what is the status on your end?
> 

I still carry it in v6.1-rt and v6.6-rt and don't really see a reason
not to. I don't believe it's a security risk since a write to
/sys/kernel/realtime gets ignored; it's just there to say that this is a
PREEMPT_RT kernel. 

So, I'm ambivalent on the keep or drop question. I'll go ahead and clean
up what I'm carrying in v6.1-rt and v6.6-rt and if we decide to keep it
I'll send you the updated changes. 

Clark

-- 
The United States Coast Guard
Ruining Natural Selection since 1790