[Development] What to do if tests hang on the CI and I can't reproduce that locally?

[Ilya Fedin]

On Thu, 16 May 2024 17:14:26 -0700
Thiago Macieira <thiago.macieira at intel.com> wrote:

> On Thursday 16 May 2024 09:55:39 GMT-7 Ilya Fedin wrote:
> > Dimitris seem to have a problem writing to the list right now but
> > what he found is that running the tests under gdb makes them not
> > hang. Perhaps this means that it's not X server who haven't replied
> > but Xlib (or libc/kernel?) who fails to notice the reply?  
> 
> Yes, it could be a race condition inside libX11.
> 
> I know libxcb is designed to not have globals, but I am not so sure
> about libX11. libxcb's .data + .bss is a mere 0xa8 bytes, while
> libX11's is 0x38e8. That's a lot of global data.
> 
> So it's entirely possible that GDK isn't getting the reply it needs
> because that reply was sent to our Display and connection and thus
> handled by our thread.
> 

I reproduced it, it was the lack of QXcbXSettings contructor being
called. idk how and why the lack of it being called leads to the
problem but the moment I reproduced it, entire GUI has frozen. I had to
switch to tty and kill the test to unfreeze the X session.