linux-kernel - Re: [PATCH printk v3 23/40] serial_core: replace uart_console_enabled() with uart_console

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Date:   Thu, 10 Nov 2022 14:52:20 +0106
From:   John Ogness <john.ogness@...utronix.de>
To:     Petr Mladek <pmladek@...e.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Sergey Senozhatsky <senozhatsky@...omium.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Ilpo Järvinen 
        <ilpo.jarvinen@...ux.intel.com>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Tony Lindgren <tony@...mide.com>,
        Lukas Wunner <lukas@...ner.de>, linux-serial@...r.kernel.org
Subject: Re: [PATCH printk v3 23/40] serial_core: replace
 uart_console_enabled() with uart_console_registered()

On 2022-11-10, Petr Mladek <pmladek@...e.com> wrote:
>>> -static inline bool uart_console_enabled(struct uart_port *port)
>>> +/* Variant of uart_console_registered() when the console_list_lock is held. */
>>> +static inline bool uart_console_registered_locked(struct uart_port *port)
>>>  {
>>> -       return uart_console(port) && (port->cons->flags & CON_ENABLED);
>>> +       return uart_console(port) && console_is_registered_locked(port->cons);
>>> +}
>>> +
>>> +static inline bool uart_console_registered(struct uart_port *port)
>>> +{
>>> +       bool ret;
>>> +
>>> +       console_list_lock();
>>> +       ret = uart_console_registered_locked(port);
>>> +       console_list_unlock();
>>> +       return ret;
>> 
>> Perhaps
>> 
>>     return uart_console(port) && console_is_registered();
>> 
>> to avoid locking the list when the first condition is not true?
>
> I do not have strong opinion on this. It is true that the code
> duplication is trivial but it is a code duplication. Either
> way would work for me.

I will go with Geert's suggestion for v4. It is important that we reduce
lock contention for non-console ports.

> The reset of the code looks good. Feel free to use:
>
> Reviewed-by: Petr Mladek <pmladek@...e.com>

Thanks.

John