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

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Message-ID: <355d1700-4d33-4604-4187-27fd994bf473@i-love.sakura.ne.jp>
Date:   Wed, 13 May 2020 23:03:19 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Michal Hocko <mhocko@...nel.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 22:46, Steven Rostedt wrote:
> On Wed, 13 May 2020 20:03:53 +0900
> Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp> wrote:
> 
>> I think that basically only oops (e.g. WARN()/BUG()/panic()) messages worth
>> printing to consoles and the rest messages do not worth printing to consoles.
>> Existing KERN_$LOGLEVEL is too rough-grained.
> 
> And this statement is exactly why I believe you are wrong.
> 
> Because *I* think messages to the console is more important than messages
> to the logs. Several of my servers are only monitored by the console. I
> seldom look at the logs on those machines.

As a technical staff at a support center, I can never monitor the consoles of
customer's servers. I can examine only syslog messages saved as /var/log/messages .

> 
> This is a policy decision, and must be made by user space. Your use case is
> not applicable to everyone else's use case. And should not be set in stone
> by the kernel.

My proposal does not set in stone by the kernel.
My proposal is gives users a chance to control whether to print to consoles.

On 2020/05/13 22:55, Steven Rostedt wrote:
> On Wed, 13 May 2020 20:03:53 +0900
> Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp> wrote:
> 
>> I think that basically only oops (e.g. WARN()/BUG()/panic()) messages worth
>> printing to consoles and the rest messages do not worth printing to consoles.
>> Existing KERN_$LOGLEVEL is too rough-grained.
> 
> Why don't you look into having a "noconsole" command line option that will
> not print anything to the consoles but oops messages.

I can't force customers to use "noconsole" command line option. That's a
too rough-grained boolean.

> 
> Sounds more like what you would like, and something that perhaps would be
> acceptable by the larger community.