linux-kernel - Re: [PATCH printk v2 12/38] tty: serial: kgdboc: use console_is

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Message-ID: <87bkpm7kp8.fsf@jogness.linutronix.de>
Date:   Fri, 04 Nov 2022 17:29:15 +0106
From:   John Ogness <john.ogness@...utronix.de>
To:     Doug Anderson <dianders@...omium.org>
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 v2 12/38] tty: serial: kgdboc: use
 console_is_enabled()

On 2022-10-24, Doug Anderson <dianders@...omium.org> wrote:
> It actually only holds console_list_lock() even at the end of the
> series. Still, it seems weird that we're declaring the `data_race` on
> CON_ENABLED but not CON_BOOT ?

For my upcoming v3 I decided to drop this patch and will keep the
existing direct reading of @flags. Instead of this patch, for v3 the
comment will additionally mention why @flags is allowed to be directly
read:

/*
 * Hold the console_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.
 */

John Ogness