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

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Date:   Wed, 06 May 2020 22:30:17 -0700
From:   Joe Perches <joe@...ches.com>
To:     Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Cc:     Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Petr Mladek <pmladek@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        linux-kernel@...r.kernel.org, Dmitry Safonov <dima@...sta.com>,
        Michal Hocko <mhocko@...e.com>,
        Yafang Shao <laoar.shao@...il.com>
Subject: Re: [PATCH] printk: Add loglevel for "do not print to consoles".

On Thu, 2020-05-07 at 14:13 +0900, Tetsuo Handa wrote:
> On 2020/05/07 10:02, Joe Perches wrote:
> > > > printk_get_level / printk_skip_level and the various
> > > > uses of %pV using printk_get_level
> > > > 
> > > 
> > > Excuse me, but what do you mean?
> > > 
> > > I wish printk() accepts "loglevel" argument detached from "fmt" argument (e.g.
> > 
> > I think that's a bad idea as it would expand
> > _every_ use of printk with another argument
> > and overall code size would increase for very
> > little value.
> 
> I'm not saying that we should add loglevel argument to all printk() callers.
> I'm saying that we could add a variant of printk() which accepts loglevel
> argument (say, e.g. printkl() and vprintkl()).
> 
> I think that some of printk_get_level() users are using printk_get_level() only
> for detaching loglevel argument from fmt argument.

I believe wrote all of those.

> I don't know how the lockless logbuf will replace printk_safe_flush_buffer(). But I guess
> it is possible to avoid printk_safe_flush_buffer() and printk_skip_level() as demonstrated
> by https://lkml.kernel.org/r/5e192ca2-3b24-0b45-fc13-51feec43c216@i-love.sakura.ne.jp .
> 
> Then, printk_skip_headers() will be the only user of printk_skip_level(). I don't know how
> vkdb_printf() works, but vkdb_printf() is currently using printk_skip_level() in order to
> remove loglevel argument. We can avoid printk_skip_level() if loglevel argument is detached
>  from fmt argument.

a vprintk_emit variant would probably do.

I proposed awhile back making functions for pr_<level>
https://lore.kernel.org/lkml/1466739971-30399-1-git-send-email-joe@perches.com/

Maybe it's time for that and something appropriate
like it for your next use too.