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From: Thomas Gleixner <tglx@linutronix.de>
To: Sujit K M <sjt.kar@gmail.com>
Cc: "Nikita V. Youshchenko" <yoush@cs.msu.su>,
	linux-rt-users@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: PREEMPT_RT (2.6.33-rt17) disabled printk-to-console after console_init
Date: Thu, 20 May 2010 11:47:32 +0200 (CEST)	[thread overview]
Message-ID: <alpine.LFD.2.00.1005201142360.3368@localhost.localdomain> (raw)
In-Reply-To: <AANLkTil18TnOR9D-dSFsSFA74Q4UFnldrGLhG1H4jwhf@mail.gmail.com>

Please stop top posting !

On Thu, 20 May 2010, Sujit K M wrote:

> >>> Well, obviously it's unsafe if you remove safety checks. And if you
> >>> care to look at the changelog of kernel/printk.c you'll find out why.
> >>
> >> Hmm... did a quick look and could not find anything related there.
> >> Could you please give a pointer?

Gah, yes. The changelog of the commit is not really helpful. Let me
explain:

The console drivers might take locks, which are converted to "sleeping
locks" in preempt-rt. As a result we cannot call into those drivers
from atomic contexts. And that's what the checks in the printk code
prevent.

Hope that helps.

Thanks,

	tglx




  reply	other threads:[~2010-05-20  9:55 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-05-18 13:13 Xianghua Xiao
2010-05-18 19:28 ` Xianghua Xiao
2010-05-18 19:47   ` Thomas Gleixner
2010-05-18 20:49     ` Xianghua Xiao
2010-05-20  8:33     ` Nikita V. Youshchenko
2010-05-20  9:25       ` Sujit K M
2010-05-20  9:32         ` Sujit K M
2010-05-20  9:47           ` Thomas Gleixner [this message]
2010-05-20 10:23             ` Nikita V. Youshchenko
2010-05-20 10:52               ` Thomas Gleixner
2010-05-20 11:12                 ` Nikita V. Youshchenko
2010-05-20 11:23                   ` Thomas Gleixner
2010-05-20 11:40                     ` Nikita V. Youshchenko

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