[Pkg-utopia-maintainers] Bug#1082570: libportal: FTBFS with segfault during TestInputCapture, reliably on AWS but rarely elsewhere

[Simon McVittie]

On Mon, 10 Feb 2025 at 15:53:23 +0100, Santiago Vila wrote:
> El 9/2/25 a las 18:48, Simon McVittie escribió:
> > On the VM that Santiago provided, I successfully built libportal from
> > source twice in a row (by entering the sid schroot and building with
> > dpkg-buildpackage), which seems inconsistent with Santiago getting a
> > less than 10% success rate.
> 
> I've just noticed that the machine I gave you was not the type I wanted
> (it was r7a.medium instead of m7a.large as intended).
> 
> Please try the new machine I've prepared for you (details in private email).

On the new 2-vCPU machine (test-4) the crash is indeed more readily
reproducible than on the 1-vCPU machine (test-3), although still not 100%:
I saw 8 failures and 2 successes in 10 runs.

As with previous attempts, I have no idea what it is about these machines
specifically that makes this race condition more likely to be hit. The
reason for the test failure seems to be a race condition in libportal
(a genuine bug, not a flaw in the test suite) which is very rarely
hit on my laptop and (as far as I can tell) has never been hit on the
official buildds, but for whatever reason is much more common on these
cloud machines.

If it's going to fail, `meson test` generally fails in around 10 seconds
on this machine. If it's going to succeed, it generally takes about a minute.

I've sent merge requests upstream to
https://github.com/flatpak/libportal/pull/184,
https://github.com/flatpak/libportal/pull/189,
https://github.com/flatpak/libportal/pull/191 attempting to fix this.
They passed 100 iterations of the test suite on test-3, and I'll queue
them to run a similar number of iterations on test-4 next.

I have spent as much time on this as I can right now, and I have other
work that I need to prioritize, so I will resume when time permits
(hopefully with a code review from upstream).

Santiago, I've powered off test-3 as you asked (sudo init 0) and if you
need to do anything further to clear it up, you can do so now; but I'm
still using test-4.

    smcv