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

From: Geert Uytterhoeven <geert@linux-m68k.org>
To: John Ogness <john.ogness@linutronix.de>
Cc: "Petr Mladek" <pmladek@suse.com>,
	"Sergey Senozhatsky" <senozhatsky@chromium.org>,
	"Steven Rostedt" <rostedt@goodmis.org>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
	"Michael Ellerman" <mpe@ellerman.id.au>,
	"Benjamin Herrenschmidt" <benh@kernel.crashing.org>,
	"Paul Mackerras" <paulus@samba.org>,
	"Eric Biederman" <ebiederm@xmission.com>,
	"Nicholas Piggin" <npiggin@gmail.com>,
	"Christophe Leroy" <christophe.leroy@csgroup.eu>,
	"Cédric Le Goater" <clg@kaod.org>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Kees Cook" <keescook@chromium.org>,
	"Tiezhu Yang" <yangtiezhu@loongson.cn>,
	"Alexey Kardashevskiy" <aik@ozlabs.ru>,
	"Yue Hu" <huyue2@yulong.com>,
	"Paul E. McKenney" <paulmck@kernel.org>,
	linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
	kexec@lists.infradead.org
Subject: Re: [PATCH printk v4 3/6] printk: remove safe buffers
Date: Thu, 2 Sep 2021 18:48:04 +0200	[thread overview]
Message-ID: <CAMuHMdXa-ahzQX2FMb-YZ9Yc4Z=72JpaN8Z9bC5htmyvEDSh+w@mail.gmail.com> (raw)
In-Reply-To: <20210715193359.25946-4-john.ogness@linutronix.de>

Hi John,

On Thu, Jul 15, 2021 at 9:53 PM John Ogness <john.ogness@linutronix.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@linutronix.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@linux-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