linux-kernel - Re: [RFC] Fast assurate clock readable from user space and NMI handler

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Message-Id: <1172570383.5517.217.camel@imap.mvista.com>
Date:	Tue, 27 Feb 2007 01:59:43 -0800
From:	Daniel Walker <dwalker@...sta.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>,
	mbligh@...gle.com, linux-kernel@...r.kernel.org,
	johnstul@...ibm.com, Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [RFC] Fast assurate clock readable from user space and NMI
	handler

On Tue, 2007-02-27 at 07:29 +0100, Ingo Molnar wrote:
> * Daniel Walker <dwalker@...sta.com> wrote:
> 
> > The pit clocksource could be dropped pretty easy with my clocksource 
> > update patches, which I'm still working on but you could easily drop 
> > clock sources that aren't atomic like the pit .. Also the pit is 
> > generally undesirable, so it's not going to be missed.
> 
> that's totally unacceptable, and i'm amazed you are even suggesting it - 
> often the PIT ends up being the most reliable hardware clock in a PC. 
> Btw., what's wrong with the spinlock that is protecting PIT access? It 
> expresses the non-atomic property of the PIT just fine.

Just considering the rating is lower than the acpi_pm (and the TSC), and
it's not even considered on SMP systems is enough for me .. It's just a
problematic clock.. 

Again, I'm not suggesting we drop it all the time, just for a special
case when Mathieu needs it dropped.

Daniel

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