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

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Message-ID: <31b2e5c4-72cf-c9b8-2a0e-2d5800c59aac@arista.com>
Date:   Tue, 28 May 2019 16:58:24 +0100
From:   Dmitry Safonov <dima@...sta.com>
To:     Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        Petr Mladek <pmladek@...e.com>
Cc:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        linux-kernel@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [RFC] printk/sysrq: Don't play with console_loglevel

Hi guys,

I see that the thread is ongoing and you understand printk code much
better than me or probably anybody :)

So, feel free to reuse it. Or I can send v1 with split sysrq/printk
parts if you think it's worth being shaped further.

I think worth to mention three "features" that you might had a chance to
miss from the current code:

1. op_p->handler(key) is not printed under console_loglevel hackery.
   So, under RFC I preserved the behavior. Probably, you don't miss it
   and just looking into ways to change it, but I thought worth
   mentioning.
2. I've found it surprising how pr_info() interacts with pr_cont():
   Basically, pr_cont() without KERN_<LEVEL> prefix will print the
   resulting line with default_message_loglevel AFAIU from cont.level.
   Which might be higher than warning.
   I might miss a part that corrects cont.level to the first
   message's level?
3. CONSOLE_LOGLEVEL_DEFAULT is config-based, so having in mind that it
   can be changed and (2) - it gives me hard time to understand when
   the sysrq message will be printed and when will be suppressed.

Thanks,
          Dmitry