Hi Cyril,

On 17/12/2018 15:56, Simon McVittie wrote:
> On Thu, 13 Dec 2018 at 17:00:21 +0100, Emilio Pozuelo Monfort wrote:
>> On 13/12/2018 16:58, Emilio Pozuelo Monfort wrote:
>>> task-pkgs-are-installable-faux depends on task-gnome-desktop, which depends 
>>> on
>>> gnome, which is removed from s390x. I'm not comfortable breaking that, you'd
>>> need an ack from Cyril for that. The alternative would be to keep building
>>> gnome from src:meta-gnome3 on s390x but removing the deps that are not 
>>> available,
>>> or to apply the proposed mozjs patches from upstream to restore support on 
>>> s390x
>>> if those are enough.
>> Another option is to restrict the task-gnome-desktop check to !s390x. But 
>> again
>> I'd like an ack from Cyril before doing that in case d-i needs to be updated 
>> to
>> not offer that on s390x.
> For context for those newly Cc'd:
> We have this dependency chain:
> task-gnome-desktop -> gnome-core -> gnome-shell -> gjs -> mozjs{52,60}
> gjs recently switched from mozjs52 to mozjs60, and mozjs60 doesn't work
> on s390x (#909536; about 80% of its tests fail, which means I have no
> confidence that the resulting binaries would be useful or usable if
> we ignored the test failures). As far as I know, the best patches we
> have for that are the ones Julien Cristau tested, which might be part
> of a solution but are not sufficient on their own to make a reasonable
> proportion of the tests pass. (Julien, please correct me if I'm wrong?)
> The GNOME team and the release team both seem to be willing to declare
> that the "full-fat" GNOME desktop will not be available on s390x
> machines, which are very conspicuously not available in a desktop or
> laptop form factor :-) I'm fairly sure that GNOME and Mozilla upstream
> have no interest in supporting s390x mainframes either. As a result we
> have arranged for all the JavaScript-based GNOME packages (most notably
> gnome-shell), and the gnome-core and gnome metapackages, to not be built
> on s390x. However, this leaves us with an important task package that
> isn't installable on a release architecture, causing migration to fail.
> I suspect gnome-shell may have never worked acceptably on s390x in any
> case, since mainframes are not noted for their 3D graphics hardware,
> and s390x is not currently whitelisted to build the llvmpipe software
> renderer in mesa's debian/rules (I believe the Mesa maintainers are
> willing to enable llvmpipe on new architectures after a porter has tested
> it and told them it works, so a s390x porter could usefully try that out).
> The options I can see are:
> * Accept that task-gnome-desktop is not going to be installable on s390x.
>   Change the testing migration scripts to skip installability testing for
>   that package on s390x, or ignore the fact that it fails. Optionally
>   change tasksel to make task-gnome-desktop Architecture: any, and give it
>   some Build-Depends-Arch that are not satisfiable on s390x so that it will
>   not be built there.
>   - s390x d-i users will not be able to install a GNOME desktop. Hopefully
>     the menu item would not appear, and task-desktop would pick up the
>     second-preference desktop instead, which currently seems to be XFCE?
>   - Risk: is it possible to ignore uninstallability of task-gnome-desktop
>     without ignoring uninstallability of other task packages?
> * Require task-gnome-desktop to be installable on s390x, but modify
>   meta-gnome3 so that on s390x, gnome-core installs something that is not
>   the full GNOME 3 desktop used on other architectures, for example
>   the GNOME-2-derived gnome-session-flashback instead of gnome-session and
>   gnome-shell, and lightdm instead of gdm3.
>   - s390x users will not get the same GNOME desktop everyone else does.
>   - Risk: if GNOME Flashback becomes unsupportable in some future release
>     (it's a GNOME 2 derivative a bit like MATE, although without using
>     forks of the apps, and most upstream and downstream GNOME maintainers
>     don't use or maintain it), we're back where we started.
> * Require task-gnome-desktop to be installable on s390x, but modify
>   meta-gnome3 so that on s390x, gnome-core doesn't install a whole desktop
>   enviroment at all, just the GNOME applications.
>   - s390x users will not get a GNOME desktop at all.
>   - Risk: this is not what the user asked for or expected.
> * Require task-gnome-desktop to be installable on s390x, but modify
>   either tasksel or meta-gnome3 so that on s390x, task-gnome-desktop
>   installs some GNOME-derived but non-GNOME desktop environment like MATE.
>   - s390x users will not get the same desktop environment everyone
>     else does.
>   - Risk: this is not what the user asked for or expected.
> I don't think waiting for someone who understands s390x to fix gjs-on-s390x
> is an option, although s390x porters are very welcome to prove me wrong!

Any thoughts on the proposed solutions for this task-gnome-desktop
installability issue on s390x now that mozjs is not working there?


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