linux-kernel - Re: Printk mulitple line message support

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Date:	Tue, 15 Nov 2011 16:54:46 -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 Wed, 2011-11-16 at 08:45 +0800, Huang Ying wrote:
> On Tue, 2011-11-15 at 10:30 +0800, Joe Perches wrote:
> > 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.
> What's your solution here?

Coalesce the multiple printks to a single printk
without KERN_CONT use at all.

For example: commit 94f05b0f60de32

> Fix multiline pr_<level> one by one with
> various prefix?

Yes, though I believe multiline_pr_<level>
isn't particularly valuable.

> How about lines with same prefix comes from different
> CPU?

Generally, emitting complete lines even from the same
module via multiple threads from a single or multiple
cpus can be intelligibly interleaved without issue.

I believe it's the printks that use KERN_CONT and the
printks without terminating newlines that are the
problems that need to be resolved somehow.

cheers, Joe

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