Re: Dependent task hashes in depsig.*

Richard Purdie

On Wed, 2022-04-27 at 08:26 -0500, Joshua Watt wrote:
On Wed, Apr 27, 2022 at 6:04 AM Richard Purdie
<richard.purdie@...> wrote:

On Wed, 2022-04-27 at 12:39 +0200, Jacob Kroon wrote:
On 4/27/22 12:12, Richard Purdie wrote:
On Wed, 2022-04-27 at 11:06 +0200, Jacob Kroon wrote:
Hi Richard and Joshua,

When using hash equivalency, since commits

scrambling a header in one of the gcc patches causes all target packages
to rebuild.
That is probably unfortunately inevitable. If the output has changed (i.e. the
headers are different), it shouldn't be matching a previous build as we can't
know what has changed.
I don't think I was being clear enough. With "scrambling a header in a
gcc patch" I mean that I change something in the section before the
"---" line in a .patch file, like modifying the "Upstream-Status" line.
To me, hash equivalence should be able to optimize that scenario, since
the output from building gcc-cross is not changed.
That definitely wasn't clear! I now understand better what you mean and yes,
we're supposed to be optimising that scenario.

This is because the depsig.do_populate_sysroot in "libgcc"

[jkroon@fedora work]$ diff -u i686-oe-linux/libgcc/11.3.0-r0/temp/depsig.do_populate_sysroot.1*
--- i686-oe-linux/libgcc/11.3.0-r0/temp/depsig.do_populate_sysroot.1589812 2022-04-27 10:14:22.403251775 +0200
+++ i686-oe-linux/libgcc/11.3.0-r0/temp/depsig.do_populate_sysroot.1674014 2022-04-27 10:26:45.329365448 +0200
@@ -1,7 +1,7 @@
glibc: 8feab297dd38b103daa4f26eeabb5690a74b8b5700d16e4eca7b56e6fd667a5e
-libgcc: dfd38409a4cc5320b781edc14de2af8321180c3f194a58b798870ad7ff6a9226
+libgcc: 195f6a155dac8e450e72a7432ab91959a8e095e057d5b79e3adba41721dc7ea5
linux-libc-headers: 12a5aaf8aec9554ac3c778cdc6c65df4db52fc573e84b7110572d459a15c9d6a
Is it the case that it is the dependent task hashes that are added
above, and that the checksum of patches are included in the those task
hashes ?
The dependent resolved hashes are used, as resolved by hashequiv which is a key
So it is the outhashes that are listed above?
No, they are hash equiv resolved hashes which would have a one to one mapping
with an outhash.

Then I don't understand
the diff above. libgcc depends on itself ? But apparently no files in
the sysroot changed, since the above is the only diff I get.
To be honest, I don't remember/understand offhand either. I'd need to go and
spend time trying to page in all the information.

We have too few people with the knowledge in these areas and I'm rapidly burning
out. I don't like this reply but I just don't have the time to dive into it and
debug it right now and I can't really give much more of a helpful comment/reply
without doing so.

I agree there is some issue here which does need investigation. At least do file
a bug so it doesn't get forgotten but we don't have many people taking on bugs
either. This one would get triaged to me or Joshua.

I'd also add that gcc is pretty horrific in that it bundles up a lot of it's
build tree into the sysroot. It is possible those bundled files are varying
somehow reproducibility wise causing some instability. I've worried about this
kind of issue for a while but I don't scale and there are a load of other issues
going on too :(.
It looks like this could possibly be a bug in the code in
meta/classes/staging.bbclass that injects the dependencies into
do_populate_sysroot & do_package.

It doesn't explicitly filter out ${PN} from BB_TASKDEPDATA, although
it perhaps should? I'm not sure if the bug is that
libgcc:do_populate_sysroot is in BB_TASKDEPDATA to begin with, or that
the code isn't filtering it out. If we do need to filter it out,
that's a pretty easy change to make.
The current task has to be in BB_TASKDEPDATA so I think you're right, we should
filter out "ourselves". I'll send a patch.



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