linux-kernel - Re: [PATCH v7 03/13] printk: console: Implement core per-console loglevel infrastructure

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Message-ID: <aR31JoSpbap1S3xJ@pathway.suse.cz>
Date: Wed, 19 Nov 2025 17:49:42 +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 03/13] printk: console: Implement core per-console
 loglevel infrastructure

On Wed 2025-11-19 03:07:06, Chris Down wrote:
> This commit adds the internal infrastructure to support per-console
> log levels, which will be configurable through sysfs and the kernel
> command line in future commits.
> 
> --- a/include/linux/console.h
> +++ b/include/linux/console.h
> @@ -518,11 +521,6 @@ extern struct hlist_head console_list;
>  static inline short console_srcu_read_flags(const struct console *con)
>  {
>  	WARN_ON_ONCE(!console_srcu_read_lock_is_held());
> -
> -	/*
> -	 * The READ_ONCE() matches the WRITE_ONCE() when @flags are modified
> -	 * for registered consoles with console_srcu_write_flags().
> -	 */
>  	return data_race(READ_ONCE(con->flags));
>  }

As you have already pointed out, the above change looks unintentional.

> --- a/kernel/printk/printk.c
> +++ b/kernel/printk/printk.c
> @@ -3835,8 +3967,12 @@ static int try_enable_preferred_console(struct console *newcon,
>  	 * without matching. Accept the pre-enabled consoles only when match()
>  	 * and setup() had a chance to be called.
>  	 */
> -	if (newcon->flags & CON_ENABLED && c->user_specified ==	user_specified)
> +	if (newcon->flags & CON_ENABLED && c->user_specified ==	user_specified) {
> +		/* Ensure level is initialized for pre-enabled consoles */
> +		if (newcon->level == 0)
> +			newcon->level = LOGLEVEL_DEFAULT;

This change does not harm. But it seems to be redundant after all.
The same check/set is done also in register_console(), see below.



>  		return 0;
> +	}
>  
>  	return -ENOENT;
>  }
> @@ -4039,6 +4175,14 @@ void register_console(struct console *newcon)
>  	}
>  
>  	newcon->dropped = 0;
> +
> +	/*
> +	 * Don't unconditionally overwrite, it may have been set on the command
> +	 * line already.
> +	 */
> +	if (newcon->level == 0)
> +		newcon->level = LOGLEVEL_DEFAULT;
> +
>  	init_seq = get_init_console_seq(newcon, bootcon_registered);
>  
>  	if (newcon->flags & CON_NBCON) {

Otherwise, it looks good to me. With two hunks removed, feel free to
use:

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

Best Regards,
Petr