linux-kernel - Re: VT-less kernels, and /dev/console on x86

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Message-ID: <3250581.5fSG56mABF@nerdopolis2>
Date: Wed, 09 Oct 2024 13:49:33 -0400
From: nerdopolis <bluescreen_avenger@...izon.net>
To: Bernd Petrovitsch <bernd@...prog.at>
Cc: pmladek@...e.com, rostedt@...dmis.org, linux-kernel@...r.kernel.org,
 john.ogness@...utronix.de, gregkh@...uxfoundation.org, tglx@...utronix.de,
 tony@...mide.com, senozhatsky@...omium.org
Subject: Re: VT-less kernels, and /dev/console on x86

On Wednesday, October 9, 2024 5:24:49 AM EDT Bernd Petrovitsch wrote:
> Hi all!
> 
> On 18.08.24 02:09, nerdopolis wrote:
> [...]
> > I originally brought this up on linux-serial, but I think it makes more sense
> > that it's part of how printk console device selection works. Without VTs, while
> > most software is able to handle the situation, some userspace programs expect
> > /dev/console to still be responsive. Namely systemd. It calls isatty() against
> > /dev/console, and since /dev/console on VT-less systems currently defaults to
> > /dev/ttyS0, and when /dev/ttyS0 is disconnected, the ioctl's fail, and it
> > refuses to write log messages to it.
> 
> What's wrong with fixing systemd?
The change was rejected, as they want the isatty() call on /dev/console
despite it returning false due to the i/o error

https://github.com/systemd/systemd/pull/33690
> 
> Kind regards,
> 	Bernd
>