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. 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. > 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. > 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/ slanga...@ubuntu.com vor...@debian.org
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