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Date: Fri, 18 Dec 2015 15:03:20 -0800
From: Andrew Morton <akpm@linux-foundation.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Daniel Thompson <daniel.thompson@linaro.org>, Jiri Kosina
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Subject: Re: [PATCH v3 4/4] printk/nmi: Increase the size of NMI buffer and
 make it configurable
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On Fri, 18 Dec 2015 13:11:41 +0100 Peter Zijlstra <peterz@infradead.org> wrote:

> On Fri, Dec 18, 2015 at 12:29:02PM +0100, Peter Zijlstra wrote:
> > On Fri, Dec 18, 2015 at 10:18:08AM +0000, Daniel Thompson wrote:
> > > I'm not entirely sure that this is an improvement.
> > 
> > What I do these days is delete everything in vprintk_emit() and simply
> > call early_printk().
> 
> On that, whoever made the device model use vprintk_emit() broke the
> debugger (KGDB/KDB) printk intercept, and the whole vprintk_func
> redirection scheme.

crap, we have a whole set of interfaces which are broken this way. 
printk_emit(), vprintk(), vprintk_emit().


commit 7ff9554bb578ba02166071d2d487b7fc7d860d62
Author:     Kay Sievers <kay@vrfy.org>
AuthorDate: Thu May 3 02:29:13 2012 +0200
Commit:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>
CommitDate: Mon May 7 16:53:02 2012 -0700

    printk: convert byte-buffer to variable-length record buffer