Re: Changing external kernel module results in rebuild of whole kernel

[Mike Looijmans <mike.looijmans@topic.nl>]

On 06-05-15 14:35, Richard Purdie wrote:
> On Wed, 2015-05-06 at 08:35 +0200, Mike Looijmans wrote:
>> Something in recent OE-core triggered a weird dependency "backfire".
>>
>> If I change a recipe for a kernel module (a bb recipe that does "inherit
>> module") this will trigger a rebuild of the whole kernel.
>>
>> This turns the 5-second job of just updating a single module into a several
>> minute workout for the build machine, and then causes boards to re-write the
>> kernel into flash needlessly when upgrading.
>>
>> I now see this on all projects using OE-core master. I can't really pin what
>> caused it though. Anyone else seen this?
>
> I have a suspicion this may be as a result of the changed kernel build
> process in 1.8.
>
> The idea there is that the modules depend on the kernel source and
> rather than taring up and then extracting a large (GB) sized sstate
> object, we just extract the original kernel source.
>
> So is the kernel really rebuilding, or, is it just extracting source for
> the kernel to build against? I noticed rm_work in your other post and
> this may also be some bad interaction between rm_work and the kernel
> build process changes.

It is really completely rebuilding the kernel (patch, configure, compile, 
install, etc). And as a result, it also recompiles each and every other kernel 
module, because these depend on the kernel as well. It will rebuild the kernel 
only once per run though, even if you change more than one module.

M.


Kind regards,

Mike Looijmans
System Expert

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