linux-kernel - Re: [PATCH] printk: Remember the message level for multi-line output

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Date:	Sun, 13 Apr 2008 21:34:53 +1000
From:	Nick Andrew <nick@...k-andrew.net>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Thomas Gleixner <tglx@...utronix.de>, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>, joe@...ches.com,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH] printk: Remember the message level for multi-line	output

On Sun, Apr 13, 2008 at 09:40:07AM +0200, Ingo Molnar wrote:
> > Restructure the logic so the processing of the leading 3 characters of 
> > each input line is in one place, regardless whether printk_time is 
> > enabled.
> 
> hm, i'm not sure about the change itself (printks are often random, so 
> the output to the console would depend on printk ordering), but the 
> combined effect seems to be a nice cleanup that reduces the linecount:

As I understand the code, if a single call to printk() includes multiple
lines of text then those lines will be contiguous in the console output.

So if one thread does printk(KERN_ERR "aaaaa\nbbbbb\n") and another
does printk(KERN_ERR "ccccc\n") then it's not possible for the buffer
to contain "<3>aaaaa\n<3>ccccc\n<3>bbbbb\n".

On the other hand, multiple calls to printk won't necessarily have
contiguous output. This affects code like arch/blackfin/kernel/traps.c
as I described in another thread which behaves like it's the only one
doing printk().

> >  1 files changed, 27 insertions(+), 34 deletions(-)
> 
> so how about splitting it into two, first the code restructuring then a 
> small add-on that does your feature? Does this make sense to you? This 
> way, even if the feature ends up not being applied, we'll have your nice 
> cleanup :-)

Can do.

Nick.
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