How to apply RT patches to a kernel not listed in http://cdn.kernel.org/pub/linux/kernel/projects/rt/4.9/older/

How to apply RT patches to a kernel not listed in http://cdn.kernel.org/pub/linux/kernel/projects/rt/4.9/older/

[Patrick Doyle]

I have a choice of 4.9.87 or 4.9.109 in my vendor supplied kernel to
which I would like to apply an RT patch set.  Unfortunately, neither
kernel is listed as a target kernel for the patches archived at
http://cdn.kernel.org/pub/linux/kernel/projects/rt/4.9/older/.  Also
unfortunately, patch sets from nearby versioned kernels (such as
patch-4.9.84 and patch-4.9.98) do not apply cleanly.

What would you (the ever helpful experts that live in the internet,
always willing to offer advice) suggest that I do to address my
dilemma?  Should I take the most recent (probably 4.9.98/rt76) branch,
rebase it on 4.9.109, clean it up as best as I can (basically, get a
kernel that compiles, and hopefully even runs) and submit the rebased
patch set here for your review?

(That's what I'm going to do, unless I hear a better idea).

--wpd

Re: How to apply RT patches to a kernel not listed in http://cdn.kernel.org/pub/linux/kernel/projects/rt/4.9/older/

[Julia Cartwright]

On Mon, Jul 30, 2018 at 03:22:32PM -0400, Patrick Doyle wrote:
> I have a choice of 4.9.87 or 4.9.109 in my vendor supplied kernel to
> which I would like to apply an RT patch set.  Unfortunately, neither
> kernel is listed as a target kernel for the patches archived at
> http://cdn.kernel.org/pub/linux/kernel/projects/rt/4.9/older/.  Also
> unfortunately, patch sets from nearby versioned kernels (such as
> patch-4.9.84 and patch-4.9.98) do not apply cleanly.

Most of the major vendors make available RT variants in their official
repos, have you checked with them?

> What would you (the ever helpful experts that live in the internet,
> always willing to offer advice) suggest that I do to address my
> dilemma?  Should I take the most recent (probably 4.9.98/rt76) branch,
> rebase it on 4.9.109, clean it up as best as I can (basically, get a
> kernel that compiles, and hopefully even runs) and submit the rebased
> patch set here for your review?

I'm in the process of cooking up a version ontop of v4.9.116 this week.
This doesn't directly address your problem, as it still may not apply
ontop of your v4.9.109 vendor kernel, but might get you closer.

   Julia

Re: How to apply RT patches to a kernel not listed in http://cdn.kernel.org/pub/linux/kernel/projects/rt/4.9/older/

[Patrick Doyle]

On Mon, Jul 30, 2018 at 5:00 PM Julia Cartwright <julia@ni.com> wrote:
> Most of the major vendors make available RT variants in their official
> repos, have you checked with them?
>
Thank you Julia.  I do not believe that they have an rt variant
(although I can push on that when my FAE returns from vacation next
week).

> I'm in the process of cooking up a version on top of v4.9.116 this week.
> This doesn't directly address your problem, as it still may not apply
> on top of your v4.9.109 vendor kernel, but might get you closer.
Wow!  That's timely.  I'm rebasing v4.9-rt on top of v4.9.109 now.  If
that blows up in my face, I'll look for your patch and try again.
(That will be plan C.)

It turns out that there is a v4.9.87-rt65 in the linux-rt tree, but it
doesn't apply to the linux-at91 tree because they have a customized
variant of kernel/softirq.c.  (They had to revert an earlier commit on
mainline).  Since I am likely to want a newer kernel in the future
anyway, I figured I would try the rebase effort first, and have the
create-a-patch-to-revert-the-revert approach as a plan B.

--wpd

Re: How to apply RT patches to a kernel not listed in http://cdn.kernel.org/pub/linux/kernel/projects/rt/4.9/older/

[Alexander Dahl]

Hei hei,

Am Montag, 30. Juli 2018, 17:26:15 CEST schrieb Patrick Doyle:
> It turns out that there is a v4.9.87-rt65 in the linux-rt tree, but it
> doesn't apply to the linux-at91 tree because they have a customized
> variant of kernel/softirq.c.  (They had to revert an earlier commit on
> mainline).  Since I am likely to want a newer kernel in the future
> anyway, I figured I would try the rebase effort first, and have the
> create-a-patch-to-revert-the-revert approach as a plan B.

Is there any particular reason to use that tree instead of running vanilla 
which has good at91 support, also in v4.9?

(I am using PREEMPT_RT on top of vanilla v4.9.x with an at91sam9g20.)

Greets
Alex

Re: How to apply RT patches to a kernel not listed in http://cdn.kernel.org/pub/linux/kernel/projects/rt/4.9/older/

[Patrick Doyle]

On Tue, Jul 31, 2018 at 3:42 AM Alexander Dahl <ada@thorsis.com> wrote:
> Hei hei,
>
> Is there any particular reason to use that tree instead of running vanilla
> which has good at91 support, also in v4.9?
>
> (I am using PREEMPT_RT on top of vanilla v4.9.x with an at91sam9g20.)
That's an excellent question!  (As my college instructors used to say
when I asked a question to which they did not know the answer.)

I guess I have always assumed that the linux-at91 tree was more
betterer for the SAMA5 than the vanilla tree.  But I have never asked
what makes it better.  I do admire and applaud Atmel/Microchip's
commitment to getting their changes mainlined.

--wpd

Re: How to apply RT patches to a kernel not listed in http://cdn.kernel.org/pub/linux/kernel/projects/rt/4.9/older/

[Alexander Dahl]

Hello,

Am Dienstag, 31. Juli 2018, 09:49:20 CEST schrieb Patrick Doyle:
> I guess I have always assumed that the linux-at91 tree was more
> betterer for the SAMA5 than the vanilla tree.  But I have never asked
> what makes it better.  I do admire and applaud Atmel/Microchip's
> commitment to getting their changes mainlined.

They do, although also a lot seems to come from the engineers at Bootlin?

If you're aiming at SAMA5: I have a look at linux-arm-kernel every now and 
then and there's still a lot of ongoing development for that target. Maybe LTS 
vanilla v4.14 with the PREEMPT_RT patches is also an option for you?

HTH and Greets
Alex