Bug#857132: console-setup: additional info needed ?

[Anton Zinoviev]

[I am sending a CC to pkg-systemd-maintainers at lists.alioth.debian.org]

On Thu, Mar 23, 2017 at 11:07:14AM +0100, Sven Joachim wrote:
> 
> There might be a third possibility which seems to happen on one of my
> systems: the cached_setup_font.sh script does not work correctly when
> run during boot by udev.  Because this is what I am observing here, I
> even added some debug messages to it to see if it is run at all (as
> intended by /lib/udev/rules.d/90-console-setup.rules), and indeed it
> does run but the font still remains unchanged.
> 
> Manually running /etc/console-setup/cached_setup_font.sh (or
> setupcon -f, for that matter) works fine, so I'm a bit at a loss here.

Since systemd makes some configuration of the console, maybe the 
following scenario might explain what we observe:

1. systemd/udev creates a new console.

2. systemd begins the initialization of this console.

3. udev runs /etc/console-setup/cached_setup_font.sh by the following 
rule:

ACTION=="add", SUBSYSTEM=="vtconsole", KERNEL=="vtcon*", RUN+="/etc/console-setup/cached_setup_font.sh"

4. Now cached_setup_font.sh and systemd execute in parallel.  If 
cached_setup_font.sh wins, it will configure the console font first and 
then systemd will load another font.

My tests of how systemd works show that it does the following:

1. It reads the curent font of the current console.

2. Then it does some things to the console(s) (configuration).

3. When a new console is created it loads on it the font read in 1.

Therefore, it seems to me that if cached_setup_font.sh completes its job 
before 1. then everything should be ok.  And if systemd completes its 
configuration before cached_setup_font.sh starts its work, then again 
everything will be ok.  However if both work simultaneously things can 
go wrong.

So, if this scenario is possible, a natural question is what can be done 
in order to make sure the scripts of console-setup do not execute in 
parallel with systemd while configuring the console.

Anton Zinoviev