linux-kernel - Re: [PATCH RESEND 1/3] printk: convert byte-buffer to variable-length record buffer

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Date:	Thu, 10 May 2012 23:01:21 +0200
From:	Kay Sievers <kay@...y.org>
To:	Joe Perches <joe@...ches.com>
Cc:	"Ted Ts'o" <tytso@....edu>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...nel.org>,
	Jonathan Corbet <corbet@....net>,
	Sasha Levin <levinsasha928@...il.com>,
	Greg Kroah-Hartmann <greg@...ah.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH RESEND 1/3] printk: convert byte-buffer to variable-length
 record buffer

On Thu, May 10, 2012 at 10:46 PM, Joe Perches <joe@...ches.com> wrote:
> On Thu, 2012-05-10 at 22:39 +0200, Kay Sievers wrote:

>> Nah, we can't do that. We need it to tell "here is your non-prefix to
>> parse, leave the data behind alone".
>
> That's where I think you're still a bit
> uncertain how the _current_ printk system
> works.
> Your _new_ printk system should
> have identical behavior.

We must be at least as good as we are, sure.

But the aim is to be *better* not to be *identical*, especially when
things go wrong, and they do go wrong far too often in the current
code. What we have today is really not good enough. We have a lot of
context during logging (like the thread), and we should use it to make
the best out of it _before_ we log the stuff away.

>  Though if you
> manage to use the call tree and current to
> coalesce complete messages more correctly,
> that'd be great.

That's what we try. We just need to get all the details out of the
peoples heads, which are nowhere written down, to make it happen. It's
a bit of a painful process sometimes. :)

The conversion from the "put all bytes in a bag and let's find out
later what happened"-buffer to a real separated record buffer imposed
some changes to the logic, and we need to restore/adapt some useful
rules now, which could't be preserved 1:1. But I'm confident that we
manage to get a better overall picture in the end.

Kay
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