linux-kernel - Re: Printk mulitple line message support

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Date:	Mon, 14 Nov 2011 18:30:17 -0800
From:	Joe Perches <joe@...ches.com>
To:	Huang Ying <ying.huang@...el.com>
Cc:	William Douglas <william.r.douglas@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: Printk mulitple line message support

On Tue, 2011-11-15 at 09:52 +0800, Huang Ying wrote:
> On Tue, 2011-11-15 at 09:18 +0800, Joe Perches wrote:
> > I believe you are not solving any real problem
> > with pr_<level>_ml.
> > Most all interleaved complete line uses have some
> > pr_fmt prefix that distinguishes between the sources.
> Except dev_<level> and netdev_<level>, it appears that many general
> pr_<level> do not have the prefix.

I'm working on that.
There are a lot of them and it's a slog.

> > A perhaps larger problem is interleaved partial
> > lines with pr_cont.
> In an interleaved situation, how to determine <level> for pr_cont?

pr_cont has its own KERN_CONT level, it's "<c>", which
is stripped from output by printk.  It's used to continue
the previous printks output on a single line.
 
> > I believe that an initiator/terminator is necessary
> > for reassembly.  Something that could be used
> > with pr_<level>, dev_<level>, netdev_<level>, et al.
> > 
> > mp_start(&cookie)
> > pr_<level>(fmt, ...);
> 
> Do not need cookie here?

Ideally not.

> > pr_mp_cont(&cookie, fmt, ...);
> > pr_mp_cont(&cookie, fmt "\n", ...);
> > mp_end(&cookie);
> 
> With initiator/terminator the kernel log will be more structural, but
> that will make kernel log a little harder to read too.

Initiator/terminator would not be part of printk output
but could exist simply to set/track the atomic/cookie #
and have printk output the appropriate cookie id when
more than 1 cookie is active.


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