Bug#789118: No issues with clean upgrade

[Josh Triplett]

On Sun, Jun 21, 2015 at 07:52:10PM +0200, Michael Biebl wrote:
> Am 20.06.2015 um 08:54 schrieb Michel Dänzer:
> > On Thu, 18 Jun 2015 21:19:20 +0400 George Hertz <georgedot at gmail.com> wrote:
> >> I've just upgraded to 3.16 on unstable, but restarted the system right 
> >> after the update finished.
> >>
> >> No problems unlocking.
> > 
> > Yeah, the problem only occurs with a gnome-shell which is already
> > running during the upgrade.
> > 
> > However, the problem also occurs when only locking the session after the
> > upgrade has completed.
> > 
> > One possible workaround after the upgrade is
> > 
> > 	killall -HUP gnome-shell gnome-settings-daemon

I didn't know you could HUP gnome-shell to unlock the session; that's
useful to know.

> > Sending SIGHUP to gnome-shell only is enough to be able to unlock the
> > session, but gnome-settings-daemon also needs to be restarted, or some
> > things such as keyboard shortcuts don't work properly in the new
> > gnome-shell.
> 
> Unfortuantely we don't have a proper mechanism to restart programs in
> the desktop session. Using killall in postinst is something I'd be wary
> about.

It's also not OK to unexpectedly unlock someone's session due to a
concurrent upgrade; "can't unlock my session" is bad, but "unlocked my
screen during upgrade" is a critical security bug.

> Unless someone finds a way to make gnome-shell (and g-s-d) compatible
> with the older versions, I guess the best we can do is to show a NEWS
> entry. But that is typically only read by the admin.

GNOME has typically required a high degree of inter-version
compatibility in many areas, such as in configuration, due to the
possibility of shared home directories.  I think it's reasonable to
require that gnome-shell work with an older version long enough to
unlock the session, even if it has degraded functionality in other ways.
(And ideally, since gnome-shell and several other GNOME components can
restart without breaking the entire session, GNOME itself should
recognize that it needs to restart them safely.

> update-notifier would be another option, but I'm unsure about it's
> current state in jessie and if it actually still works.
> 
> And last, it wouldn't work for Josh's case either, who locked the screen
> midway through the upgrade.

Right.

- Josh Triplett