linux-kernel - Re: [PATCH printk v2 38/38] printk, xen: fbfront: create/use safe function for forcing preferred

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Message-ID: <Y1qVWOyJuALz0vXf@alley>
Date:   Thu, 27 Oct 2022 16:27:36 +0200
From:   Petr Mladek <pmladek@...e.com>
To:     John Ogness <john.ogness@...utronix.de>
Cc:     Sergey Senozhatsky <senozhatsky@...omium.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...r.kernel.org, Helge Deller <deller@....de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Javier Martinez Canillas <javierm@...hat.com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Juergen Gross <jgross@...e.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Tom Rix <trix@...hat.com>, linux-fbdev@...r.kernel.org,
        dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH printk v2 38/38] printk, xen: fbfront: create/use safe
 function for forcing preferred

On Thu 2022-10-27 15:41:23, John Ogness wrote:
> On 2022-10-27, Petr Mladek <pmladek@...e.com> wrote:
> >> -	if (c) {
> >> -		unregister_console(c);
> >> -		c->flags |= CON_CONSDEV;
> >> -		c->flags &= ~CON_PRINTBUFFER; /* don't print again */
> >> -		register_console(c);
> >> -	}
> >> +	if (c)
> >> +		console_force_preferred(c);
> >
> > I would prefer to fix this a clean way.
> >
> > [...]
> >
> > I would suggest to implement:
> >
> > [...]
> >
> > It is a more code. But it is race-free. Also it is much more clear
> > what is going on.
> >
> > How does this sound, please?
> 
> I wasn't sure if any of the other preferred-console magic in
> register_console() was needed, which is why I kept a full
> register_console() call. But if it really is just about forcing it the
> head and setting a new CON_CONSDEV, then your suggestion is much
> simpler. Thanks.

I believe that it is just this. I have spent a lot of time
investigating these hacks when thinking about refactoring
of register_console().

Best Regards,
Petr