linux-kernel - Re: [PATCH] printk: Add loglevel for "do not print to consoles".

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Message-ID: <a75d6560-ad99-5b02-3648-247c27c3a398@i-love.sakura.ne.jp>
Date:   Wed, 13 May 2020 16:58:48 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
To:     Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Cc:     Michal Hocko <mhocko@...nel.org>, Petr Mladek <pmladek@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        linux-kernel@...r.kernel.org, Dmitry Safonov <dima@...sta.com>,
        Yafang Shao <laoar.shao@...il.com>
Subject: Re: [PATCH] printk: Add loglevel for "do not print to consoles".

On 2020/05/13 15:26, Sergey Senozhatsky wrote:
> Yes, but this looks like it's the consumer of the messages who
> decides what to filter and what not to. rsyslog, dmesg, etc.
> will have different filtering policies. It's not like the kernel
> decides what to hide and what to show. If would compare this to
> NO_CONSOLES, then NO_CONSOLES does a different thing after all.

I just showed an example that changing dump_tasks() messages from
KERN_INFO to KERN_DEBUG is not an option. If dump_tasks() were using
KERN_DEBUG, the consumer of the messages will have to receive all
KERN_DEBUG messages, which needlessly contains uninterested messages.
If dump_tasks() allows use of NO_CONSOLES (via e.g. sysctl switch),
the consumer does not need to receive KERN_DEBUG messages.

What is wrong with adding NO_CONSOLES ?