Hi Scott,
I have the occasional bug report observing that plymouth doesn't start
when shutting down a live CD session booted with the "Install Ubuntu"
option. I haven't actually been able to reproduce this myself, so I
assume that it's racy. However, I've been trying to decipher the
plymouth job graph, bearing in mind
https://bugs.launchpad.net/upstart/+bug/447654 ("init: using 'and'
operators can cause hangs"), and was wondering if you could sanity-check
my conclusions.
Here are the relevant jobs:
plymouth-stop:
start on (starting gdm
or starting kdm
or starting xdm
or starting lxdm
or starting ubiquity
or starting oem-config
or stopped rc RUNLEVEL=[2345]
or starting rcS
or starting mountall-shell)
stop on stopped plymouth
plymouth:
start on (starting mountall
or (runlevel [016]
and (stopped gdm
or stopped kdm
or stopped xdm
or stopped lxdm)))
ubiquity:
start on (starting gdm
or starting kdm
or starting xdm
or starting uxlaunch)
stop on runlevel [06]
gdm:
start on (filesystem
and started dbus
and (graphics-device-added fb0 PRIMARY_DEVICE_FOR_DISPLAY=1
or drm-device-added card0 PRIMARY_DEVICE_FOR_DISPLAY=1
or stopped udevtrigger))
stop on runlevel [016]
Proving any of this is a right pain because of course all the debugging
information vanishes at reboot, but what I think happens is:
runlevel 6 emitted
-> starting plymouth (blocked)
-> stopping gdm
-> stopping ubiquity
'stopping gdm' and 'stopping ubiquity' race because there's no
relationship between them. If 'stopping ubiquity' wins, then:
stopped ubiquity
-> (completes, shutting down X)
stopped gdm
-> starting plymouth
If 'stopping gdm' wins, however:
stopped gdm
-> starting plymouth
ubiquity is still stopping, so X may still be running, which means
that plymouth is going to race with X, and will probably dismiss the
splash screen as soon as X stops and switches back to tty1, or
something along those lines, leaving the user with a plain text
console on tty1. Badness.
My proposal for fixing this is to change ubiquity's stop event to:
stop on (stopping gdm
or stopping kdm
or stopping xdm
or stopping uxlaunch)
This doesn't particularly change the conditions under which ubiquity is
stopped, except for adding runlevel 1, which is OK; but it means that
gdm etc. can't finish stopping until ubiquity has stopped, which means
that plymouth will definitely not start until both ubiquity and gdm have
stopped, which is what we want.
Does this look right to you?
Thanks,
--
Colin Watson [cjwat...@ubuntu.com]
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