Re: Hooking up gnome-session with dbus/kdbus/systemd

[Sriram Ramkrishna <sri ramkrishna me>]

On Tue, Jan 21, 2014 at 10:08 AM, Lennart Poettering
<mztabzr 0pointer de> wrote:
> Heya,
>
> I am typing this from a GNOME session that actually uses a kdbus user
> bus instead of a dbus-daemon session bus (and also a kdbus system
> bus). With this mail I'd like to start discussion of the changes I'd
> like to propose for GNOME to make this work a bit more smoothly.

This is great!

> As you might now, the kdbus userspace we have been working on involves
> using systemd for setting it up. The system systemd instance will set up
> the system bus, and the user systemd instance will set up the user
> bus. Besides actually opening up kdbus for usage in the session bus, I'd
> also like to see GNOME adopt systemd for its process (application)
> management needs. This would have a number of benefits, like for example
> exposing GNOME apps (and other components) as cgroups, so that we can do
> all kinds of modern stuff like suspending apps that our outside of view,
> or fiddling with the CPU scheduling prio for foreground apps, and things
> like that. Also, we'd gain a trustable, kernel-level way how to
> distuingish apps, for polkit stuff and more.

Dreams do come true.

> c) gnome-session currently has some special .desktop file support that
>    it uses to set up the session and run it (parsing stuff from
>    /etc/xdg/autostart). For that it forks off all
>    processes on its own, and will wait for SIGCHLD to bind the lifecycle
>    of the session to the lifecycle of gnome-settings-daemon +
>    gnome-shell. It also uses that to implement "phases". I'd like to see
>    this minimally changed to watch for the
>    existance of the respective bus names instead, and use normal bus
>    activation to start everything. The phase logic can stay in
>    gnome-session even if gnome-session doesn't fork anything of
>    anymore but uses bus activation for every>

So this seems like we are going to continue to use gnome-session in
order to maintain support for non-systemd operating system.  My
question is, why not at least move everything to systemd --user for
systemd sessions instead of maintaining gnome-session?  That way we
get the benefits of things like bootchart and have more direct control
of how GNOME starts?

I've heard some unsubstantiated claims that KDE is moving to this
model and is replacing startkde with systemd --user session.  I'm not
sure what they are planning to do with non-systemd OS, but apparently
they seem to be calling them "legacy" systems.  Maybe not an
appropriate label IMHO.  But it seems that there is room to at least
consider moving wholesale to systemd --user instead of maintaining a
frontend and then changing everything behind the scenes.

sri