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Date: Fri, 17 Jun 2005 13:08:51 +0200
From: Ingo Molnar <mingo@elte.hu>
To: "K.R. Foley" <kr@cybsft.com>
Cc: linux-kernel@vger.kernel.org, "Eugeny S. Mints" <emints@ru.mvista.com>,
       Daniel Walker <dwalker@mvista.com>
Subject: Re: [patch] Real-Time Preemption, -RT-2.6.12-rc6-V0.7.48-00
Message-ID: <20050617110851.GA26500@elte.hu>
References: <20050608112801.GA31084@elte.hu> <42B0F72D.5040405@cybsft.com> <20050616072935.GB19772@elte.hu> <42B160F5.9060208@cybsft.com> <20050616173247.GA32552@elte.hu> <42B1BDF7.1000700@cybsft.com> <42B1E316.2040406@cybsft.com>
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* K.R. Foley <kr@cybsft.com> wrote:

> Just had an opportunity to check this. Everything does indeed seem to 
> be working OK with this disabled. No lock up messages, no perceived 
> problems.

btw., you have this enabled in your config:

   CONFIG_DEBUG_RT_LOCKING_MODE=y

this causes old-style spinlocking to be activated by default. I.e. you 
dont get most of the benefits of PREEMPT_RT. You can reactivate it via:

	echo 1 > /proc/sys/kernel/preempt_locks

but obviously this runtime flag involves some runtime overhead in the 
locking code. This .config option is mainly meant to enable the 
measurement of the locking overhead of PREEMPT_RT, and to debug boot 
problems that might be related to PREEMPT_RT locking.  So you'd almost 
always want to run with DEBUG_RT_LOCKING_MODE turned off.

	Ingo