linux-kernel - Re: [PATCH printk v5 38/40] tty: serial: kgdboc: use console_list

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Message-ID: <CAD=FV=VouG3ihFCg4gC3dNFs7TqzpDgowHd38y8fR8qiTfRw_A@mail.gmail.com>
Date:   Wed, 16 Nov 2022 16:56:14 -0800
From:   Doug Anderson <dianders@...omium.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>,
        Daniel Thompson <daniel.thompson@...aro.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 v5 38/40] tty: serial: kgdboc: use
 console_list_lock to trap exit

Hi,

On Wed, Nov 16, 2022 at 8:22 AM John Ogness <john.ogness@...utronix.de> 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>
> Reviewed-by: Daniel Thompson <daniel.thompson@...aro.org>
> Reviewed-by: Petr Mladek <pmladek@...e.com>
> ---
>  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)) &&

Officially don't we need both the list lock and normal lock here since
we're reaching into the consoles?

-Doug