The Server launches with DRI3 disabled only upon initial system startup

[Luc Ma]

Hi! recently I came across a weird issue on my ubuntu 22.04.5.

After desktop startup, `xdpyinfo` shows that DRI3 extension is absent, but if I restart vncserver@:2 service manually, and then reconnect the vncserver, `xdpyinfo` shows

DRI3 is back this time. I tried several times, and it is readily reproducible. Not sure if this is a bug.

My machine info

OS: Ubuntu 22.04.5

Kernel: 6.8.0-40-generic

dGPU: AMD Radeon RX 7600 (in use)

VNC Server:  TigerVNC 1.15.0 built Feb 16 2025 (downloaded from Sourceforge)

Server start: systemctl enable vncserver@:2.service

                       systemctl restart vncserver@:2

[Pierre Ossman]

I would guess some permission issue that resolves itself either once
boot is completed, or when you've logged in manually.

Could you compare the logs for the VNC server between when it works and
when it doesn't?

Regards,
--
Pierre Ossman Software Development
Cendio AB https://cendio.com
Teknikringen 8 https://twitter.com/ThinLinc
583 30 Linköping https://facebook.com/ThinLinc
Phone: +46-13-214600

A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?

[Luc Ma]

Hi, Pierre

On Tue, 24 Jun 2025 at 17:09, Pierre Ossman <oss...@cendio.se> wrote:
>
> On 24/06/2025 06:16, Luc Ma wrote:
> > Hi! recently I came across a weird issue on my ubuntu 22.04.5.
> >
> > After desktop startup, `xdpyinfo` shows that DRI3 extension is absent, but
> > if I restart vncserver@:2 service manually, and then reconnect the
> > vncserver, `xdpyinfo` shows
> > DRI3 is back this time. I tried several times, and it is readily
> > reproducible. Not sure if this is a bug.
> >
> > My machine info
> > OS: Ubuntu 22.04.5
> > Kernel: 6.8.0-40-generic
> > dGPU: AMD Radeon RX 7600 (in use)
> > VNC Server: TigerVNC 1.15.0 built Feb 16 2025 (downloaded from Sourceforge)
> > Server start: systemctl enable vncserver@:2.service
> > systemctl restart vncserver@:2
> >
> >
>
> I would guess some permission issue that resolves itself either once
> boot is completed, or when you've logged in manually.
>
> Could you compare the logs for the VNC server between when it works and
> when it doesn't?

After having a look at /var/log/syslog, it looks like "systemd[1]:
Started Remote desktop service (VNC). " appears
before "[drm] Initialized amdgpu 3.57.0 20150101 for 0000:03:00.0 on
minor 1" when it doesn't work, vice versa when
it does.

I guess systemd starting VNC and GPU init could occur in parallel,
maybe the server launches with DRI3 enabled requires
GPU device initialization to get done firstly.

>
> Regards,
> --
> Pierre Ossman Software Development
> Cendio AB https://cendio.com
> Teknikringen 8 https://twitter.com/ThinLinc
> 583 30 Linköping https://facebook.com/ThinLinc
> Phone: +46-13-214600
>
> A: Because it messes up the order in which people normally read text.
> Q: Why is top-posting such a bad thing?

Regards,
--
Luc

[Pierre Ossman]

On 24/06/2025 13:55, Luc Ma wrote:
>
> After having a look at /var/log/syslog, it looks like "systemd[1]:
> Started Remote desktop service (VNC). " appears
> before "[drm] Initialized amdgpu 3.57.0 20150101 for 0000:03:00.0 on
> minor 1" when it doesn't work, vice versa when
> it does.
>
> I guess systemd starting VNC and GPU init could occur in parallel,
> maybe the server launches with DRI3 enabled requires
> GPU device initialization to get done firstly.
>

Indeed. The drivers need to be loaded first. Which normally happens very
early in the system, so I'm not sure what's broken here. :/