Re: cups-browsed/systemd question

[James Feeney <james@nurealm.net>]

On 03/10/2015 04:19 PM, Till Kamppeter wrote:
> If I shut down Avahi while cups-browsed is running on my Ubuntu system
> (Upstart-based) cups-browsed keeps running and also re-connects when I
> start avahi-daemon again.
> 
>    Till

The original problem was with respect to an interaction between cups-browsed and
systemd.  The problem may be related specifically to systemd interaction, and
testing in other contexts may not be illuminating.

Another possibility, looking at the log, is an interaction with D-Bus and cupsd.
 First, there is a complaint from cupsd, as D-Bus is stopped:

topaz cupsd[380]: Unable to communicate with avahi-daemon: An unexpected
D-Bus error occured
systemd[1]: Stopped D-Bus System Message Bus.

We only know that something is amiss with cups-browsed because it fails to exit,
and systemd waits.  The only log message complaining is from cupsd, not at all
from cups-browsed.

It is only then that cups-browsed is found to be still running.  It may be that
the inference about avahi-daemon needing to communicate with cupsd before
cups-browsed stops, or cups-browsed needing to communicate with avahi-daemon, is
completely mistaken.

Could cups-browsed have been waiting on cupsd, while cupsd was waiting on
avahi-daemon?  Or cups-browsed been waiting on cupsd while cupsd had already
exited?  Or could cups-browsed have been waiting on D-Bus, which had already exited?

Presumably there is some race condition during shutdown, since I have only seen
this cups-browsed-hang once.

James