Comment # 7 on bug 1047716 from P. Otato

(In reply to Fabian Vogt from comment #6)
> (In reply to P. Otato from comment #5)
> > Thanks for the tip Fabian. Uninstalling drm-kmp-default seems to be a valid
> > workaround. Marking this as RESOLVED:WORKSFORME since this seems to be a
> > regression that has been backported from Linux Kernel 4.9.
> 
> IMO it still needs to be looked into by the kernel team, it's installed by
> default.

Thanks for caring. 

Some additional information:
I've experienced this bug also in Manjaro KDE with Linux Kernel 4.9 but NOT in
Debian Stretch (also Linux Kernel 4.9). So maybe somebody already wrote a
patch.

Maybe this could be relevant although the hang up reason is different:
https://lists.debian.org/debian-kernel/2017/02/msg00111.html