linux-kernel - Re: [PATCH printk v4 3/6] printk: remove safe buffers

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Date:   Thu, 2 Sep 2021 18:48:04 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.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 Mailing List <linux-kernel@...r.kernel.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Eric Biederman <ebiederm@...ssion.com>,
        Nicholas Piggin <npiggin@...il.com>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Cédric Le Goater <clg@...d.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Kees Cook <keescook@...omium.org>,
        Tiezhu Yang <yangtiezhu@...ngson.cn>,
        Alexey Kardashevskiy <aik@...abs.ru>,
        Yue Hu <huyue2@...ong.com>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        kexec@...ts.infradead.org
Subject: Re: [PATCH printk v4 3/6] printk: remove safe buffers

Hi John,

On Thu, Jul 15, 2021 at 9:53 PM John Ogness <john.ogness@...utronix.de> wrote:
> With @logbuf_lock removed, the high level printk functions for
> storing messages are lockless. Messages can be stored from any
> context, so there is no need for the NMI and safe buffers anymore.
> Remove the NMI and safe buffers.
>
> Although the safe buffers are removed, the NMI and safe context
> tracking is still in place. In these contexts, store the message
> immediately but still use irq_work to defer the console printing.
>
> Since printk recursion tracking is in place, safe context tracking
> for most of printk is not needed. Remove it. Only safe context
> tracking relating to the console and console_owner locks is left
> in place. This is because the console and console_owner locks are
> needed for the actual printing.
>
> Signed-off-by: John Ogness <john.ogness@...utronix.de>

Thank you very much for reducing kernel size by ca. 8 KiB!

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds