[poky] RT-patch for Yocto-kernel

[Keskinarkaus, Teemu]

Sorry for top post.

I did some test. I compiled our project with linux-yocto-rt and linux-yocto - kernels.  Then checked from menuconfig that both of those kernels same options in:
Processor type and features ->  Preemption Model.
-> No Forced Preemption
-> Voluntary Kernel Preemption
-> Preemptible kernel

When added rt-patch from: https://www.kernel.org/pub/linux/kernel/projects/rt/3.8/ I got two more options:

-> Preemtible Kernel (Basic RT)
-> Fully Preememptible Kernel (RT)

The fact that the rt-patch applied just fine to linux-yocto-rt - kernel sources got me thinking that the linux-yocto-rt does NOT contain the kernel.org rt-patch I mentioned earlier.  If that's the case then what's the point on whole rt-kernel branch? Or how do I get the rt-patched version of the kernel? When I compile the kernel I see that it uses linux-yocto-rt-3.8.13+gitAUTOINC+2a6d36e75c_47aed0c17c-r4.1 so it's not using the normal version of the kernel.

Teemu Keskinarkaus

-----Original Message-----
From: Bruce Ashfield [mailto:bruce.ashfield at gmail.com]
Sent: 4. marraskuuta 2013 15:17
To: Keskinarkaus, Teemu
Cc: poky at yoctoproject.org
Subject: Re: [poky] RT-patch for Yocto-kernel

On Mon, Nov 4, 2013 at 2:31 AM, Keskinarkaus, Teemu <Teemu.Keskinarkaus at maximatecc.com> wrote:
> Hi,
>
>
>
> In our system we want to use Full RT - kernel configuration. I learned
> that Yocto/Poky Preempt - rt is actually just low latency
> configuration and not the real Full RT as the name falsely suggests.
> Anyway, that's not the problem after I found it.
>

Hmm. No. The standard/preempt-rt/* branches in the Yocto kernel are the full -rt patch.

>
>
> There is a patch in the kernel.org that adds the Full RT support for
> the kernel. Unfortunately it doesn't work right away in Yocto kernel.
> We use emenlow variant of the kernel.
>
>
>
> So I compiled the system and then fixed the patch by applying it to
> kernel sources in build-directory. Then added the  patch to kernel
> .bbappend file so that it would be applied during compilation time.  Or so I thought.
>
>
>
> Now when I try to compile the system do_patch - state for
> linux-yocto-rt - fails.
>
>
>
> Log data follows:
>
> | DEBUG: Executing shell function do_patch
>
> | Deleted branch meta-temp (was 37fdb0c).
>
> | [INFO] validating against known patches  (emenlow-preempt-rt-meta)
>
> Context reduced to (2/2) to apply fragment at 385    ] (\)(88 %))
>
> error: patch failed: drivers/net/ethernet/ti/cpsw.c:374(/)(92 %)%)
>
> | error: drivers/net/ethernet/ti/cpsw.c: patch does not apply
>
> | Context reduced to (1/1) to apply fragment at 1050
>
> | error: patch failed: include/linux/preempt.h:107
>
> | error: include/linux/preempt.h: patch does not apply
>
> | error: patch failed: kernel/sched/core.c:1477
>
> | error: kernel/sched/core.c: patch does not apply
>
> | ERROR. could not update git tree
>
> | ERROR. Could not apply patches for emenlow.
>
> |        Patch failures can be resolved in the devshell (bitbake -c
> | devshell
> linux-yocto-rt)
>
>
>
> If I'm understanding that right it actually applied my patch before
> the emenlow-patch and that's why it fails.
>
>
>
> What's the proper way to make kernel patch that big or is there
> already Full RT - patch for emenlow kernel for yocto? We have smaller
> patches that don't collide with emmenlow patches and they work just fine.

You simply need to make the emenlow BSP compatible with linux-yocto-rt and use KBRANCH="standard/preempt-rt/base"

And you have the full -rt patch available.

Cheers,

Bruce

>
>
>
> Teemu Keskinarkaus
>
>
>
>
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________________________________

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