[bitbake-devel] Forcing the rebuild of dependent tasks across recipes

[Mark Hatle]

On 11/22/19 9:09 AM, Matthias Schiffer wrote:
> Hi all,
> 
> is there a robust way to enforce the automatic rebuild of dependent
> tasks across recipes? I'm having the following issue:
> 
> - Recipe my-core-image has an output file that is copied to the deploy
> dir. The output file is not fully reproducible, so cleaning the recipe
> and rebuilding it will yield a different file even through the sstate
> signature of the recipe is unchanged (the file I'm interested is
> DMVerity hash data that I generate as an additional filesystem type)
> 
> - Task do_compile of recipe my-initramfs-scripts depends on my-core-
> image:do_image_complete. I need to enforce rebuilding of this task
> whenever the deployed files of my-core-image have changed (the recipe
> uses the "root hash" generated by DMVerity as input, so that the
> filesystem can be verified on mount) - and of course also of all
> dependent tasks like the initramfs image and FIT kernel image
> 
> I've experimented with things like file-checksums and BB_DONT_CACHE,
> but everything I've tried fails when the rebuilds of my-core-image and
> my-initramfs-scripts are supposed to happen in the same run of Bitbake:
> 
> - file-checksums only seems to be taken into account at initial recipe
> parse time, not when the task I'm interested in is actually executed? I
> need to run bitbake twice to get the correct results.
> - When I use an anonymous Python function to put the root hash I'm
> interested in into a variable, Bitbake complains about nondeterministic
> metadata.

There is a way of doing this, I've had to do it in the past.

The anonymous python function needs to product the same output on each and every
run.  If it doesn't this will cause the non-deterministic behavior.  (It can't
rely on another items to finish building for instance.)

So you end up having to have a recipe (with a file-checksum and/or anon python)
that sets up variables that will keep the hash up-to-date for THAT recipe.. then
your image (or other) recipes need to depend on that one.

Unfortunately I no longer have access to the example where I had to do this in
the past, or I could try to give you something more concrete to look at.

--Mark

> 
> Using nostamp would be an option, but obviously an ugly one.
> 
> I'm currently on Yocto Thud / Bitbake 1.40.
> 
> 
> Thanks in advance,
> 
> Matthias
>