Major QDBus regression in Qt6 with potential impact on KDE

[Thiago Macieira]

On Thursday, 15 December 2022 18:34:54 -03 Kai Uwe Broulik wrote:
> thanks for bringing that up. Indeed, at least Solid, KDE’s Hardware
> Abstraction Framework, makes use of InterfacesAdded/InterfacesRemoved
> extensively when talking to UDisks for monitoring storage devices.
> 
> That said, I haven’t tried Solid on Qt 6 yet, so I don’t know if it is a
> real-world issue for this scenario.

The issue appears to be a race condition, because strace shows everything 
working as it should and the use of QDBUS_DEBUG=1 will affect timing. That also 
means the issue is likely a Heisenbug and difficult to debug.

It might also be a latent issue in Qt 5 that got exposed by faster 
functionality somewhere in QtCore, because there have been no changes to 
QtDBus to account for this (it has barely received any changes since 5.6).

Someone needs to debug it and I don't have the time.

-- 
Thiago Macieira - thiago (AT) macieira.info - thiago (AT) kde.org
   Software Architect - Intel DCAI Cloud Engineering