linux-kernel - Re: printk: what is going on with additional newlines?

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Message-ID: <1504250613.2361.5.camel@perches.com>
Date:   Fri, 01 Sep 2017 00:23:33 -0700
From:   Joe Perches <joe@...ches.com>
To:     Pavel Machek <pavel@....cz>
Cc:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Petr Mladek <pmladek@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>, Jan Kara <jack@...e.cz>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jiri Slaby <jslaby@...e.com>, Andreas Mohr <andi@...as.de>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: printk: what is going on with additional newlines?

On Fri, 2017-09-01 at 08:59 +0200, Pavel Machek wrote:
> On Thu 2017-08-31 19:04:24, Joe Perches wrote:
> > On Fri, 2017-09-01 at 10:40 +0900, Sergey Senozhatsky wrote:
> > > On (08/29/17 22:24), Pavel Machek wrote:
> > > > > > In 4.13-rc, printk("foo"); printk("bar"); seems to produce
> > > > > > foo\nbar. That's... quite surprising/unwelcome. What is going on
> > > > > > there? Are timestamps responsible?
> > []
> > > > You are welcome not add checkpatch rules to prevent such code from being
> > > > merged...
> > 
> > Pavel, what does this mean?
> That should have been "welcome to".

Right.

Good luck with a checkpatch implementation.

> IMO pr_foo() is bad interface for debugging.

Why?

> I just want to see the data... and difference
> from userspace debugging actually hurts there.

How so?  What data is not available?

Making functions of the various pr_<level> uses
makes it easier to insert things like singletons
for any pr_fmt prefix which could save a few KB
and as well allow for centralized mechanisms to
emit logging messages with
	%ps, __builtin_return_address(0)
instead of using
	"%s <fmt>", __func__, args...
to save even more space.