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Message-ID: <1323855797.28489.22.camel@twins>
Subject: Re: printk() vs tty_io
From: Peter Zijlstra <peterz@infradead.org>
To: Ingo Molnar <mingo@elte.hu>
Cc: Greg KH <greg@kroah.com>, "Theodore Ts'o" <tytso@mit.edu>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Alan Cox <alan@lxorguk.ukuu.org.uk>,
        linux-kernel <linux-kernel@vger.kernel.org>
Date: Wed, 14 Dec 2011 10:43:17 +0100
In-Reply-To: <20111214065910.GA25775@elte.hu>
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	 <20111214065910.GA25775@elte.hu>
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On Wed, 2011-12-14 at 07:59 +0100, Ingo Molnar wrote:

> btw., would be nice to also somehow realeasify those debug hacks 
> to preserve them for eternity - doing all lockdep output as 
> earlyprintk while keeping printks working is a great way to 
> debug printk() itself.
> 
> Those printk lockups also took a *lot* of time for me to bisect.

Yeah, they're horrible.. took me long enough to reproduce, and even now
I know how its not easy.

Anyway, I just posted the two patches that make lockdep do
early_printk(), they're not too horrid. I still need to look at making
dump_stack() play nice as well, but so far I've managed to grok bits
from the held lock output only.