Status changed to 'Confirmed' because the bug affects multiple users.
** Changed in: lightdm (Ubuntu)
Status: New => Confirmed
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https://bugs.launchpad.net/bugs/1111537
Title:
lightdm's post-stop sometimes fails
Status in “lightdm” package in Ubuntu:
Confirmed
Bug description:
In our somewhat complicated environment, I've managed to trigger a
race condition in which shutting down or rebooting the machine from a
(custom) lightdm greeter results in the machine popping up the "low
graphics mode" warning, and never shutting down. The greeter is using
the Python GIR bindings to call LightDM.shutdown() and
LightDM.restart(), respectively, so I'm fairly certain it's not the
greeter's fault.
I finally tracked this down to the post-stop script in lightdm's
upstart job, namely that "initctl emit desktop-shutdown" is sometimes
returning non-zero. Because all Upstart jobs are run with "set -e",
lightdm fails, and Upstart then decides that X isn't working and pops
up the low-graphics mode warning.
Adding the usual "|| :" idiom fixes this, e.g.
post-stop script
if [ "$UPSTART_STOP_EVENTS" = runlevel ]; then
initctl emit desktop-shutdown || :
fi
end script
I think this is the right thing to do anyway, because if lightdm is
being stopped, and for whatever reason, the desktop-shutdown signal is
not emitted, there's not a good way to recover from that anyway, so it
shouldn't be a fatal failure. This is hard to reproduce (indeed, my
steps to reproduce include "Try this about 30 times until it fails".
While on a single machine, this is not a big deal, distributed over
400 heavily used public machines, it's becoming a real problem), but
the fix is easy and a no-op, so I would hope it would be considered
anyway.
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