linux-kernel - Re: [PATCH printk v3 4/7] printk: nbcon: Add ownership state functions

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Message-ID: <8734zox0m7.fsf@jogness.linutronix.de>
Date:   Fri, 08 Sep 2023 15:26:32 +0206
From:   John Ogness <john.ogness@...utronix.de>
To:     Petr Mladek <pmladek@...e.com>
Cc:     Sergey Senozhatsky <senozhatsky@...omium.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH printk v3 4/7] printk: nbcon: Add ownership state functions

On 2023-09-06, Petr Mladek <pmladek@...e.com> wrote:
>> +static bool nbcon_context_can_proceed(struct nbcon_context *ctxt, struct nbcon_state *cur)
>> +{

[...]

>> +	/*
>> +	 * It is not known whether the handover succeeded. The outermost
>
> It was not immediately clear to me what exactly "handover succeeded" did mean.
> I would write:
>
> 	* It is not clear whether the waiter really took the lock
> 	* and re-printed the record. The outermost calsite...

It is not just about printing. A console is locked by drivers for other
purposes as well. And that is the situation that this comment is mostly
targetting. For v4 I change it to:

        /*
         * It is not clear whether the waiter really took over ownership. The
         * outermost callsite must make the final decision whether console
         * ownership is needed for it to proceed. If yes, it must reacquire
         * ownership (possibly hostile) before carefully proceeding.
         *
         * The calling context no longer owns the console so go back all the
         * way instead of trying to implement reacquire heuristics in tons of
         * places.
         */

John Ogness