linux-kernel - Re: [RFC] printk/sysrq: Don't play with console

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Message-ID: <4a9c1b20-777d-079a-33f5-ddf0a39ff788@i-love.sakura.ne.jp>
Date:   Tue, 28 May 2019 12:21:47 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
To:     Dmitry Safonov <dima@...sta.com>, linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>, Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [RFC] printk/sysrq: Don't play with console_loglevel

On 2019/05/28 9:24, Dmitry Safonov wrote:
> Provide KERN_UNSUPPRESSED printk() annotation for such legacy places.
> Make sysrq print the headers unsuppressed instead of changing
> console_loglevel.

I think that kdb also wants to use KERN_UNSUPPRESSED for making sure
that messages are printed. But that user calls dump function which is
indirectly calling printk() many times. Thus, I think that we need a
way to explicitly pass "how the message should be treated" as a
function argument.

What I suggested in my proposal ("printk: Introduce "store now but print later" prefix." at
https://lore.kernel.org/lkml/1550896930-12324-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp/T/#u )
is "whether the caller wants to defer printing to consoles regarding
this printk() call". And your suggestion is "whether the caller wants
to apply ignore_loglevel regarding this printk() call".