linux-kernel - Re: printk() vs tty

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Message-ID: <20111214065910.GA25775@elte.hu>
Date:	Wed, 14 Dec 2011 07:59:10 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Greg KH <greg@...ah.com>, Theodore Ts'o <tytso@....edu>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: printk() vs tty_io

* Peter Zijlstra <peterz@...radead.org> wrote:

> Hi tty folks,
> 
> I've been poking at reducing the constraints on printk(), like make it
> work under rq->lock etc..
> 
> Aside from a fwd port of the patch that abuses the 
> console_sem.lock: https://lkml.org/lkml/2011/6/9/298 and a few 
> other not so very pretty patches, I ran into the following 
> lockdep splat (using a not so very pretty lockdep 
> early_printk() patch):

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.

Thanks,

	Ingo
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