[systemd-devel] [PATCH 10/10] logind: implement generic multi-session

[Tom Gundersen]

Hi David,

On Sun, Aug 25, 2013 at 8:46 PM, David Herrmann <dh.herrmann at gmail.com> wrote:
> One important note is that delayed session-switching is meant for
> backwards compatibility. New compositors or other sessions should really
> try to deal correctly with forced session switches! They only need to
> handle EACCES/EPERM from syscalls and treat them as "PauseDevice" signal.
>
> Following logind patches will add a timeout to session-switches which
> forces the switch if the active session does not react in a timely
> fashion. Moreover, explicit ForceActivate() calls might also be supported.
> Hence, sessions must not crash if their devices get paused.

I don't quite get the backwards compatibility argument. In order to
make use of this, compositors would anyway have to be ported to the
logind interface, so why not just require these compositors to handle
EACCESS/EPERM as you describe and avoid the backwards compatibility
stuff? Do you have reason to believe that handling EACCESS would be
significantly harder than just porting to the PauseDevice interface?
Or is there something else I'm missing?

Cheers,

Tom