[Buildroot] Please help me on kernel configuration with rt-patch applied

Andreas Ziegler br015 at umbiko.net
Mon Oct 25 09:11:28 UTC 2021


Hi Matteo,

On 2021-10-25 07:22, Pampolini Matteo wrote:
> Hello Andreas,
> 
> many thanks for your answer and sorry for the delay of mine, during
> the weekend I did not have the chance to work on this issue.
> 
> Anyway, I checked BR2_LINUX_KERNEL_CONFIG_FRAGMENT_FILES variable in
> my Buildroot configuration file and is empty, my approach
> for kernel patching always worked in other cases, what am I doing wrong 
> now?

Sorry, my mistake, you get the 'merged configuration' message also on 
builds without configuration fragment file.

I use PREEMPT_RT myself, usually in BR2_LINUX_KERNEL_PATCH, and seldom 
had issues.

Could you check if you can configure PREEMPT_RT features manually after 
initial creation of the kernel directory?

$ rm -fr output/build/linux-5.4.78
$ make linux-nconfig

On the off chance, which architecture are you building for? These 
architectures are supported by PREEMPT_RT:

$ cd build/linux-5.4.155
$ fg ARCH_SUPPORTS_RT
./arch/arm/Kconfig:     select ARCH_SUPPORTS_RT
./arch/arm64/Kconfig:   select ARCH_SUPPORTS_RT
./arch/powerpc/Kconfig: select ARCH_SUPPORTS_RT
./arch/x86/Kconfig:     select ARCH_SUPPORTS_RT

Also, CONFIG_EXPERT must be selected to be able to configure a fully 
preemptable kernel.

Kind regards,
Andreas

> Regards, Matteo
> 
> 
> Company General Use
> 
> 
> Il presente messaggio e-mail e ogni suo allegato devono intendersi
> indirizzati esclusivamente al destinatario indicato e considerarsi dal
> contenuto strettamente riservato e confidenziale. Se non siete
> l'effettivo destinatario o avete ricevuto il messaggio e-mail per
> errore, siete pregati di avvertire immediatamente il mittente e di
> cancellare il suddetto messaggio e ogni suo allegato dal vostro
> sistema informatico. Qualsiasi utilizzo, diffusione, copia o
> archiviazione del presente messaggio da parte di chi non ne è il
> destinatario è strettamente proibito e può dar luogo a responsabilità
> di carattere civile e penale punibili ai sensi di legge.
> Questa e-mail ha valore legale solo se firmata digitalmente ai sensi
> della normativa vigente.
> 
> The contents of this email message and any attachments are intended
> solely for the addressee(s) and contain confidential and/or privileged
> information.
> If you are not the intended recipient of this message, or if this
> message has been addressed to you in error, please immediately notify
> the sender and then delete this message and any attachments from your
> system. If you are not the intended recipient, you are hereby notified
> that any use, dissemination, copying, or storage of this message or
> its attachments is strictly prohibited. Unauthorized disclosure and/or
> use of information contained in this email message may result in civil
> and criminal liability. “
> This e-mail has legal value according to the applicable laws only if
> it is digitally signed by the sender
> -----Messaggio originale-----
> Da: Andreas Ziegler [mailto:br015 at umbiko.net]
> Inviato: venerdì 22 ottobre 2021 18:27
> A: Pampolini Matteo <matteo.pampolini at leonardocompany.com>
> Oggetto: Re: Please help me on kernel configuration with rt-patch 
> applied
> 
> Ciao Matteo,
> 
>> Hello,
>> 
>> 
>> I'm facing a strange issue on kernel configuration with rt-patch
>> applied.
>> 
>> 
>> I'm using buildroot-2020.02.8 with kernel 5.4.78 and rt-patch
>> 5.4.78-rt44, patch is applied through BR2_GLOBAL_PATCH_DIR variable
>> and custom kernel configuration that takes it into account is passed
>> through BR2_LINUX_KERNEL_CUSTOM_CONFIG_FILE variable.
>> 
>> 
>> Patch is correctly applied and above configuration file is copied into
>> kernel build directory. However after this the following message is
>> displayed:
>> 
>> 
>> Using /home/user/buildroot-2020.02.8/output/build/linux-5.4.78/.config
>> as base
>> #
>> # merged configuration written to
>> /home/user/buildroot-2020.02.8/output/build/linux-5.4.78/.config
>> (needs make)
>> #
>> scripts/kconfig/conf  --olddefconfig Kconfig #
> 
> It looks as if you have a configuration fragment file configured which
> is big enough to overwrite everything. Check
> BR2_LINUX_KERNEL_CONFIG_FRAGMENT_FILES directly below the kernel
> configuration file and the content of the file.
> 
>> And then my custom configuration is overwritten and rt-patch config
>> variables are not present anymore in actual kernel .config file.
>> 
>> I also tried with BR2_LINUX_KERNEL_PATCH variable, but the result is
>> the same.
> 
> I do not think this is patch related; you still should be able to
> configure RT settings when you execute 'make nconfig'.
> 
>> May you please help me? I've used BR2_GLOBAL_PATCH_DIR variable to
>> apply other kernel patches since now without any problems.
> 
> Kind regards,
> Andreas
> 
>> Thanks, Matteo


More information about the buildroot mailing list