linux-kernel - Re: [PATCH v4 0/2] Add support to dump printk buffer to console via sysrq

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Date: Wed, 7 Feb 2024 15:12:09 +0100
From: Petr Mladek <pmladek@...e.com>
To: Sreenath Vijayan <sreenath.vijayan@...y.com>
Cc: john.ogness@...utronix.de, corbet@....net, gregkh@...uxfoundation.org,
	jirislaby@...nel.org, rdunlap@...radead.org, rostedt@...dmis.org,
	senozhatsky@...omium.org, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org,
	taichi.shimoyashiki@...y.com, daniel.palmer@...y.com,
	anandakumar.balasubramaniam@...y.com
Subject: Re: [PATCH v4 0/2] Add support to dump printk buffer to console via
 sysrq

Hi,

first, I am sorry for joining the game so late. I was sick
and have had a lot of pending tasks after Christmas's holidays
and the sickness.

On Thu 2024-02-01 13:12:39, Sreenath Vijayan wrote:
> Hi,
> 
> This patch series enables one to dump the messages in printk ring
> buffer unless all CPUs are locked up. This is useful to view the
> kernel messages when terminal is unresponsive to enter commands
> like dmesg and syslog services are also disabled, especially on
> embedded targets.

What is the exact scenario for this feature, please?

IMHO, rewinding the entire log on an unresponsive terminal
has a questionable value. Most messages would scroll down
quickly and only the last messages would stay visible.

Also this code would rewind all consoles, including
(slow) serial ones. I wonder if rewind on these consoles
would be useful as well.

That said, I am not completely against this feature.
I just want to be sure that it does what you expect.

Best Regards,
Petr