From: Thomas Gleixner <tglx@linutronix.de>
To: Xianghua Xiao <xiaoxianghua@gmail.com>
Cc: linux-kernel@vger.kernel.org, linux-rt-users@vger.kernel.org
Subject: Re: PREEMPT_RT (2.6.33-rt17) disabled printk-to-console after console_init
Date: Tue, 18 May 2010 21:47:23 +0200 (CEST) [thread overview]
Message-ID: <alpine.LFD.2.00.1005182143100.3368@localhost.localdomain> (raw)
In-Reply-To: <AANLkTinClrTDoXH4NPP2-SgSYH24ZTnqsop88aocdg4R@mail.gmail.com>
On Tue, 18 May 2010, Xianghua Xiao wrote:
> I could not get dmesg output to console/serial and
> klogd(/var/log/messages) anymore with 2.6.33-rt17 _after_ the kernel
> boot is done(on non-RT kernel it works fine). I made below changes it
> starts to work again, however I'm unsure how safe the change is.
> Please advise.
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.
Short story: It's introducing nasty latencies.
Use "earlyprintk=serial,ttyS0,115200,keep" if you care, but do not
complain about the resulting latencies.
Thanks,
tglx
next prev parent reply other threads:[~2010-05-18 19:47 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 [this message]
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
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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