Bug#960355: Invalid serial console blocks system boot

From	Jonas Zeiger <jonas.zeiger@talpidae.net>
Newsgroups	linux.debian.bugs.dist, linux.debian.kernel
Subject	Bug#960355: Invalid serial console blocks system boot
Date	2020-05-12 01:30 +0200
Message-ID	<A5q1X-1BL-5@gated-at.bofh.it> (permalink)
Organization	talpidae.net

Cross-posted to 2 groups.

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Package: initramfs-tools-core
Version: 0.137

Putting a serial console on a non-existent/broken serial port
via the last "console=" argument of the kernel command line
causes the initrd to hang without completing the boot process.

If the problematic serial console argument comes first in the kernel
command line, the system boots without issues.


***To reproduce:***

1. Check for a non-connected/disabled serial port.

	On the problematic system running

	[$] stty -a -F /dev/ttyS1
	stty: /dev/ttyS1: Input/output error

	The serial ports are registered by the "serial8250" driver but are 
probably not wired to anything.


2. Boot with a kernel command line that puts serial console on a 
non-existent/broken serial port via last "console=" argument:

	console=tty0 console=ttyS1,115200n8


3. Check if system boots successfully


I am using Debian GNU/Linux 11 (bullseye/testing), vanilla kernel 
5.7-rc5.


This issue was initially reported multiple times for Debian and Ubuntu
to the systemd maintainers as:

https://github.com/systemd/systemd/issues/15656  (for Ubuntu)
https://github.com/systemd/systemd/issues/15783  (for Debian, duplicate)


I am not sure if the _exact_ cause of both issues is the same,
because I observed the problem on a very minimal system without
console-setup or kbd.

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Bug#960355: Invalid serial console blocks system boot Jonas Zeiger <jonas.zeiger@talpidae.net> - 2020-05-12 01:30 +0200
  Bug#960355: marked as done (Invalid serial console blocks system  boot) "Debian Bug Tracking System" <owner@bugs.debian.org> - 2020-05-16 01:00 +0200
  Bug#960355: marked as done (Invalid serial console blocks system  boot) "Debian Bug Tracking System" <owner@bugs.debian.org> - 2020-09-11 22:40 +0200

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