linux-kernel - Re: [PATCH printk v1 13/13] console: introduce CON_MIGHT

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Message-ID: <YhZ9lHQjq7urH120@kroah.com>
Date:   Wed, 23 Feb 2022 19:31:48 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Petr Mladek <pmladek@...e.com>
Cc:     John Ogness <john.ogness@...utronix.de>,
        Sergey Senozhatsky <senozhatsky@...omium.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-kernel@...r.kernel.org, Jiri Slaby <jirislaby@...nel.org>,
        Max Filippov <jcmvbkbc@...il.com>,
        David Sterba <dsterba@...e.com>,
        Samuel Iglesias Gonsálvez 
        <siglesias@...lia.com>, Bhaskar Chowdhury <unixbhaskar@...il.com>,
        Igor Matheus Andrade Torrente <igormtorrente@...il.com>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        nick black <dankamongmen@...il.com>
Subject: Re: [PATCH printk v1 13/13] console: introduce CON_MIGHT_SLEEP for vt

On Wed, Feb 23, 2022 at 02:37:55PM +0100, Petr Mladek wrote:
> On Mon 2022-02-07 20:49:23, John Ogness wrote:
> > Deadlocks and the framebuffer console have been a recurring issue
> > that is getting worse. Daniel Vetter suggested [0] that
> > fbcon->write() should no longer be called from an atomic context.
> 
> We should make it clear that people will not longer see kernel
> messages on ttyX during early boot, panic, and in some other
> situations when printk kthreads are not available.
> 
> Or do I miss something?
> 
> Do we really want this?
> 
> Do the tty maintainers really want to give up on supporting
> modes when processes/kthreads do not work?

I would love that, but:

> Maybe, it is inevitable. Maybe, people are not using tty
> for debugging too much.

People are using tty consoles for debugging all the time.  We can not
break that.

thanks,

greg k-h