linux-kernel - Re: TSC calibration sometimes not correct with RT patch.

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Message-ID: <20070725073949.GB595@elte.hu>
Date:	Wed, 25 Jul 2007 09:39:49 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Henri Hunnekens <henrihunnekens@...il.com>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: TSC calibration sometimes not correct with RT patch.


* Henri Hunnekens <henrihunnekens@...il.com> wrote:

> I've seen that the calbration of the TSC timer was not always done 
> correctly, which resulted in incorrect timers.
> 
> I found out that local_irq_disable is used before the calibration is 
> started. However with the RT patch applied this does not mean that the 
> interrupts are disabled and therefore the calibration may fails when 
> it's interrupted by an interrupt. Correct me if I'm wrong.

local_irq_disable() still disables interrupts, even in PREEMPT_RT. So 
the problem should be elsewhere. Can you see similar problems on .22-rt 
too? The hrt code saw a number of updates there.

	Ingo
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