linux-kernel - Re: [PATCH printk 11/18] printk: Convert console

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Message-ID: <Yy7hxxJVzY6GYHkG@google.com>
Date:   Sat, 24 Sep 2022 19:53:59 +0900
From:   Sergey Senozhatsky <senozhatsky@...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,
        "James E.J. Bottomley" <James.Bottomley@...senpartnership.com>,
        Helge Deller <deller@....de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-parisc@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH printk 11/18] printk: Convert console_drivers list to
 hlist

On (22/09/24 02:10), John Ogness wrote:
[..]
>  static int console_unregister_locked(struct console *console)
>  {
> -	struct console *con;
>  	int res;
>  
>  	con_printk(KERN_INFO, console, "disabled\n");
> @@ -3274,32 +3287,28 @@ static int console_unregister_locked(struct console *console)
>  	if (res > 0)
>  		return 0;
>  
> -	res = -ENODEV;
>  	console_lock();
> -	if (console_drivers == console) {
> -		console_drivers=console->next;
> -		res = 0;
> -	} else {
> -		for_each_console(con) {
> -			if (con->next == console) {
> -				con->next = console->next;
> -				res = 0;
> -				break;
> -			}
> -		}
> -	}
>  
> -	if (res)
> -		goto out_disable_unlock;
> +	/* Disable it unconditionally */
> +	console->flags &= ~CON_ENABLED;
> +
> +	if (hlist_unhashed(&console->node))
> +		goto out_unlock;

Shouldn't this set `ret` to -ENODEV before goto? Otherwise it will always
return 0 (which is set by _braille_unregister_console()).

> +
> +	hlist_del_init(&console->node);
>  
>  	/*
> +	 * <HISTORICAL>
>  	 * If this isn't the last console and it has CON_CONSDEV set, we
>  	 * need to set it on the next preferred console.
> +	 * </HISTORICAL>
> +	 *
> +	 * The above makes no sense as there is no guarantee that the next
> +	 * console has any device attached. Oh well....
>  	 */

It's complicated...