linux-kernel - Re: [PATCH printk v3 38/40] tty: serial: kgdboc: use console_list

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Date:   Thu, 10 Nov 2022 15:18:07 +0000
From:   Daniel Thompson <daniel.thompson@...aro.org>
To:     John Ogness <john.ogness@...utronix.de>
Cc:     Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <senozhatsky@...omium.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...r.kernel.org,
        Jason Wessel <jason.wessel@...driver.com>,
        Douglas Anderson <dianders@...omium.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        kgdb-bugreport@...ts.sourceforge.net, linux-serial@...r.kernel.org
Subject: Re: [PATCH printk v3 38/40] tty: serial: kgdboc: use
 console_list_lock to trap exit

On Mon, Nov 07, 2022 at 03:22:36PM +0106, John Ogness wrote:
> kgdboc_earlycon_init() uses the console_lock to ensure that no consoles
> are unregistered until the kgdboc_earlycon is setup. The console_list_lock
> should be used instead because list synchronization responsibility will
> be removed from the console_lock in a later change.
> 
> Signed-off-by: John Ogness <john.ogness@...utronix.de>

I've not looked at the other patches in the series to understand the
future tense here (e.g. why we need intermediate patches like this one).

However I've no objections to the change so:
Reviewed-by: Daniel Thompson <daniel.thompson@...aro.org>


Daniel.


> ---
>  drivers/tty/serial/kgdboc.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/tty/serial/kgdboc.c b/drivers/tty/serial/kgdboc.c
> index 8c2b7ccdfebf..a3ed9b34e2ab 100644
> --- a/drivers/tty/serial/kgdboc.c
> +++ b/drivers/tty/serial/kgdboc.c
> @@ -558,13 +558,13 @@ static int __init kgdboc_earlycon_init(char *opt)
>  	 */
>  
>  	/*
> -	 * Hold the console_lock to guarantee that no consoles are
> +	 * Hold the console_list_lock to guarantee that no consoles are
>  	 * unregistered until the kgdboc_earlycon setup is complete.
>  	 * Trapping the exit() callback relies on exit() not being
>  	 * called until the trap is setup. This also allows safe
>  	 * traversal of the console list and race-free reading of @flags.
>  	 */
> -	console_lock();
> +	console_list_lock();
>  	for_each_console(con) {
>  		if (con->write && con->read &&
>  		    (con->flags & (CON_BOOT | CON_ENABLED)) &&
> @@ -606,7 +606,7 @@ static int __init kgdboc_earlycon_init(char *opt)
>  	}
>  
>  unlock:
> -	console_unlock();
> +	console_list_unlock();
>  
>  	/* Non-zero means malformed option so we always return zero */
>  	return 0;
> -- 
> 2.30.2
>