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

[Anton Zinoviev]

On Thu, Mar 23, 2017 at 02:12:44PM -0300, Felipe Sateler wrote:
> 
> As mentioned by Michael, this is not done by udev or systemd.

I think systemd runs getty which opens a console.  Then the kernel 
creates virtual consoles on demand.

> > From my tests it seems that the font used
> > for this initialization is the same as the font used on the current
> > console.  Isn't it possible that sometimes this font is set only _after_
> > udev has started the script cached_setup_font.sh by the following rule
> >
> > ACTION=="add", SUBSYSTEM=="vtconsole", KERNEL=="vtcon*", RUN+="/etc/console-setup/cached_setup_font.sh"
> >
> > however the font of the current console is read _before_ the script
> > cached_setup_font.sh has had a chance to configure the font?
> 
> I don't know of any component that does that.

The kernel?

> However, I see the following in cached_setup_font:
> 
> setfont '/etc/console-setup/cached_Lat15-Fixed16.psf.gz'
> 
> if ls /dev/fb* >/dev/null 2>/dev/null; then
>     for i in /dev/vcs[0-9]*; do
>         { :
>             setfont '/etc/console-setup/cached_Lat15-Fixed16.psf.gz'
>         } < /dev/tty${i#/dev/vcs} > /dev/tty${i#/dev/vcs}
>     done
> fi
> 
> Might it be that /dev/fb* do not exist during boot, and thus the font
> is not loaded in all ttys?


If /dev/fb* doesn't exist then the graphics card is in hardware text 
mode in which case there is one font on all ttys (due to hardware 
limitation).  If /dev/fb* is created afterwards, then udev will run 
cached_setup_font again.

I don't know what is going to happen if:

1. udev runs cached_setup_font while there is no framebuffer

2. the script tests that there is no /dev/fb*

3. before the script completes its work /dev/fb* is created

In this case the rule of udev will trigger for a second time.  However 
since the script hasn't finished yet will then udev run a second copy of 
it?  If not, then this too, might create problems.  On the other hand, 
if udev always runs cached_setup_font again, do both copies run in 
parallel (this shoudn't be a problem for cached_setup_font but it is 
good to know if such possibility exists)?

Anton Zinoviev