linux-kernel - Re: [PATCH v7 06/13] printk: Support toggling per-console loglevel via syslog() and cmdline

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Message-ID: <aR7n7-7c9vi8vjuS@pathway.suse.cz>
Date: Thu, 20 Nov 2025 11:05:35 +0100
From: Petr Mladek <pmladek@...e.com>
To: Chris Down <chris@...isdown.name>
Cc: linux-kernel@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Sergey Senozhatsky <senozhatsky@...omium.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	John Ogness <john.ogness@...utronix.de>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Tony Lindgren <tony.lindgren@...ux.intel.com>, kernel-team@...com
Subject: Re: [PATCH v7 06/13] printk: Support toggling per-console loglevel
 via syslog() and cmdline

On Wed 2025-11-19 03:07:22, Chris Down wrote:
> A new module parameter (ignore_per_console_loglevel) is added, which can
> be set via the kernel command line or at runtime through
> /sys/module/printk/parameters/ignore_per_console_loglevel. When set, the
> per-console loglevels are ignored, and the global console loglevel
> (console_loglevel) is used for all consoles.
> 
> During sysrq, we temporarily disable per-console loglevels to ensure all
> requisite messages are printed to the console. This is necessary because
> sysrq is often used in dire circumstances where access to
> /sys/class/console may not be trivially possible.
> 
> Additionally, the syslog actions SYSLOG_ACTION_CONSOLE_ON and
> SYSLOG_ACTION_CONSOLE_OFF are augmented to save and restore the state of
> ignore_per_console_loglevel. This allows administrators to enable or
> disable per-console loglevels dynamically using the syslog() system
> call, as supported in userspace by things like dmesg.
> 
> This is useful when debugging issues with message emission, or when
> needing to quickly break glass and revert to global loglevel only.
> 
> Signed-off-by: Chris Down <chris@...isdown.name>

Looks good to me:

Reviewed-by: Petr Mladek <pmladek@...e.com>

Best Regards,
Petr