<steve.langasek@ubuntu.com> wrote:
>
> Hi Christian,
>
> On Mon, May 18, 2020 at 03:57:39PM +0200, Christian Ehrhardt wrote:
> > Hi,
> > I was revisiting one of the packages the server team usually looks
> > after: `rdma-core`.
> > Late in the focal release cycle I was asked to mark the `pandoc`
> > build-dependency with !i386 as it doesn't exist there and was causing
> > problems [1]. I was revisiting this now to resolve it in a better way
> > to be able to make the package a sync again.
>
> > I had a discussion with Debian and started to wonder why this is a
> > problem for Ubuntu at all. That made me identify a weak spot in my
> > understanding of partial i386 [3][4].
> > The odd thing to me is that `rdma-core` isn't part of the i386
> > whitelist [5], so why would it be a problem that the d/control lists
> > pandoc as build-dep - I'd have expected it to not build at all.
> > Then I realized that germinate still pulls it in [6], but failed to
> > see why. Is it that we actually have i386 builds on the whitelist and
> > in addition all-of-its-build-deps ?
>
> The relevant germinate output is
> https://people.canonical.com/~ubuntu-archive/germinate-output/i386.groovy/i386+build-depends
>
> This shows the source packages that are in the set, as well as why they're
> pulled in.
>
> rdma-core is there as a dependency of openmpi, which is a dependency of
> mpi-defaults, which is a build-dependency of boost.
Thank you for this link on top of the ones I have checked.
> There are a lot more packages that need to be built on i386 than those that
> are directly in the whitelist, because we need a closure over
> build-dependencies in order to be able to build the packages that are in the
> whitelist.
I was seeing that it was more, thanks for confirming that it is due to
the dependencies.
I have added this to the wiki page [4] so that fewer people have to
ask again :-)
> > Furthermore that might explain why the only dependency left is openmpi
> > which also isn't part of the whitelist [5] but shown in germinate [6].
>
> > $ reverse-depends --release=groovy --arch=i386 src:rdma-core
> > Reverse-Depends
> > * libopenmpi-dev (for libibverbs-dev)
>
> > I now wonder if a much easier fix might be to remove the build
> > dependency to rdma-core on src:openmpi (for i386 only) which would
> > finally make rdma-core really not building on i386. Is that a better
> > solution? Openmpi in turn has a much longer list of things depending
> > on it, doing the cut at openmpi->rdma-core seems to be the cleanest.
>
> I have no preference on whether we do the cut above or below rdma. If you
> find that having openmpi not depend on rdma-core on i386, and keeping
> rdma-core in sync, is easier for maintenance, then that's fine.
Looking at openmpi more in detail it seems someone called "Steve"
already gave this a shot :-)
The current Delta we have there is:
* Also disable the direct build-dependency on libibverbs-dev (from
rdma-core) on i386.
* Disable libfabric support on i386 to avoid pulling in rdma-core.
So since we already have delta on openmpi due to i386 let us try to
reduce it to just openmpi.
It seems the build deps are correct, but there is a hard dependency
statement in d/control:
libibverbs-dev (>= 1.1.7) [!kfreebsd-i386 !kfreebsd-amd64 !hurd-i386]
That just needs the same !i386 treatment as the build-deps you have
already done.
Hopefully rdma-core will no more be pulled then.
I'll do the openmpi change and re-check the i386 germinate a day later
if rdma-core really was let go on i386.
> > But then I have realized that while there are not more runtime
> > dependencies, build dependencies in i386 seem to be quite a lot still
> > (reverse-depends --release=groovy --arch=i386 --build-dep
> > src:rdma-core shows 41).
>
> As far as I know these are all false-positives; I don't know that
> reverse-depends --build-dep --arch=foo ever does anything useful.
> Spot-checking the output, I see that most of these packages only have arch:
> all packages published on i386.
>
> > With this mail I'd look for:
> > a) general guidance on `is the effective i386 build = whitelist + build-deps`
> > b) feedback on the suggestion to remove the rdma-core build dep on
> > openmpi; or would all 41 build-deps have to go away?
> > c) other alternatives
>
> > The answers to (a) we could add to the wiki [4].
> > The answers to (b)+(c) will hopefully help me to go on with this, it
> > might eventually come down to keeping the current Delta (trivial) in
> > rdma-core, but along the way understanding the inner workings better
> > would be great.
> >
> > [1]: https://launchpad.net/ubuntu/+source/rdma-core/28.0-1ubuntu1
> > [2]: https://github.com/linux-rdma/rdma-core/pull/756#issuecomment-630138899
> > [3]: https://discourse.ubuntu.com/t/community-process-for-32-bit-compatibility/12598
> > [4]: https://wiki.ubuntu.com/i386
> > [5]: https://git.launchpad.net/~ubuntu-core-dev/ubuntu-seeds/+git/i386/tree/i386
> > [6]: https://people.canonical.com/~ubuntu-archive/germinate-output/i386.focal/i386+build-depends.sources
>
> --
> Steve Langasek Give me a lever long enough and a Free OS
> Debian Developer to set it on, and I can move the world.
> Ubuntu Developer https://www.debian.org/
> slangasek@ubuntu.com vorlon@debian.org
--
Christian Ehrhardt
Staff Engineer, Ubuntu Server
Canonical Ltd
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