bitbake: bitbake/runqueue: rework 'bitbake -S printdiff' logic

Previously printdiff code would iterate over tasks that were reported as invalid or absent,
trying to follow dependency chains that would reach the most basic invalid items in the tree.

While this works in tightly controlled local builds, it can lead to bizarre reports
against industrial-sized sstate caches, as the code would not consider whether the
overall target can be fulfilled from valid sstate objects, and instead report
missing sstate signature files that perhaps were never even created due to hash
equivalency providing shortcuts in builds.

This commit reworks the logic in two ways:

- start the iteration over final targets rather than missing objects
and try to recursively arrive at the root of the invalid object dependency.

A previous version of this patch relied relies on finding the most 'recent'
signature in stamps or sstate in a different function later, and recursively
comparing that to the current signature, which is unreliable on real world caches.

- if a given object can be fulfilled from sstate, recurse only into
its setscene dependencies; bitbake wouldn't care if dependencies
for the actual task are absent, and neither should printdiff

I wrote a recursive function for following dependencies, as
doing recursive algorithms non-recursively can result in write-only
code, as was the case here.

[YOCTO #15289]

(Bitbake rev: aadeca63da5d96160ce4d6d71da556e2e033f9b7)

Signed-off-by: Alexander Kanavin <alex@linutronix.de>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

0 files changed, 0 insertions, 0 deletions