linux-kernel - Re: linux.git: printk() problem

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Message-ID: <CAMuHMdWnL82zsDSJUW08LrKjAdeB4b100VybFr3Dgcs7Tpg49A@mail.gmail.com>
Date:   Mon, 24 Oct 2016 13:15:51 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Joe Perches <joe@...ches.com>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Petr Mladek <pmladek@...e.cz>
Subject: Re: linux.git: printk() problem

Hi Linus,

On Sun, Oct 23, 2016 at 9:46 PM, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
> On Sun, Oct 23, 2016 at 12:32 PM, Linus Torvalds
> <torvalds@...ux-foundation.org> wrote:
>>
>> No, the real complexity comes from that interaction with the console
>> output, which is done outside the core log locks, and which currently
>> has the added thing where we have a "has this line fragment been
>> flushed or not".
>
> Ok, so here's the stupid patch that removes all the partial line flushing.
>
> NOTE! It still leaves all the games with LOG_NEWLINE and LOG_NOCONS
> that are pretty much pointless with it. So there's room for more
> simplification here.
>
> In particular, the games with LOG_NEWLINE is what Geert's "console and
> dmesg output looks different" at least partially comes from. What
> happens is that "dmesg" always shows the records as one line (so it
> effectively ignores LOG_NEWLINE), but the console output (in
> msg_print_text() still has that LOG_NEWLINE logic.
>
> In particular, msg_print_text() looks at the *previous* logged line to
> decide whether it should do newlines etc, which is why Geert gets that
> odd "two continuations per line" pattern on the console, but "one
> continuation per line" in dmesg. That comes from the interaction with
> flushing to the console and LOG_NEWLINE and just general complexity.

Thanks, Linux kernel output is again in sync with dmesg output.

Tested-by: Geert Uytterhoeven <geert@...ux-m68k.org>

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