Re: [OE-core] Strange behavior in sstate-diff-machines.sh

[Richard Purdie <richard.purdie@linuxfoundation.org>]

On Mon, 2025-02-03 at 21:34 +0000, Chris Laplante via lists.openembedded.org wrote:
> We are on Scarthgap, and I am seeing an issue with sstate-diff-
> machines.sh wherein the script claims to see task signature
> differences, but then doesn't report any. For example, I get:
> 
> ERROR: base-files different signature for task
> do_package_write_rpm.sigdata between my-machine-1 and my-machine-2
> NOTE: Starting bitbake server...
> 
> There should be output from bitbake-diffsigs after the 'Note:' lines.
> 
> I did some poking around in tmp/sstate-diff. The 'list.M' file for
> my-machine-1 has:
> 
> MACHINEpoky-linux/base-
> files/3.0.14.do_package_write_rpm.sigdata.af0c3fb3b1b8494fcd7a31ba513
> 495df384fdf25a8eced584e7c71d722b26683
> 
> But the list.M for my-machine-2 has:
> 
> my-machine-1-poky-linux/base-
> files/3.0.14.do_package_write_rpm.sigdata.af0c3fb3b1b8494fcd7a31ba513
> 495df384fdf25a8eced584e7c71d722b26683 
> 
> So interestingly, the hash is the same
> (af0c3fb3b1b8494fcd7a31ba513495df384fdf25a8eced584e7c71d722b26683),
> but in the case of 'base-files' for my-machine-2, it ended up using
> the sstate (I guess?) from my-machine-1. Maybe this has something to
> do with hash equiv? (I have BB_HASHSERVE set to 'auto')
> 
> Can anyone please help explain?

I've never liked that script and personally, I've always wanted to make
bitbake's owm signature "diff" as helpful as we can. There are ton of
different things that conspire against us in doing that and whilst
we've improved, it still isn't ideal.

I'd note that the script predates hash equivalence and that can be a
big factor in things things like this. We've struggled to reconcile
some of the tools with changes like hash equivalence :(

So yes, I can imagine do_package matching between the two machines,
then hashequiv would reuse the later tasks like do_package_write_rpm
from sstate.

Cheers,

Richard