linux-kernel - Re: [PATCH] Re: x86_32 tsc/pit and hrtimers

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Message-ID: <alpine.LFD.2.00.0810090910510.3237@apollo>
Date:	Thu, 9 Oct 2008 09:14:34 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Jeff Hansen <x@...fhansen.com>
cc:	Chris Snook <csnook@...hat.com>, torvalds@...ux-foundation.org,
	linux-kernel@...r.kernel.org, mingo@...e.hu
Subject: Re: [PATCH] Re: x86_32 tsc/pit and hrtimers

On Wed, 8 Oct 2008, Jeff Hansen wrote:

> [HRTIMER]: Add highres=noverify option to bypass clocksource verification
> 
> This disregards the CLOCK_SOURCE_MUST_VERIFY flag on all clocksources.
> This is particularly useful on legacy x86_32 systems that have no ACPI,
> LAPIC, or HPET timers, where only TSC and PIT are available.

While I agree in principle, adding this to highres is the wrong thing
to do. This is a property of clocksources and not of high resolution
timer support.

The affected clocksource is TSC and it should go there as a command
line option e.g. tsc=stable, which in turn clears the
CLOCK_SOURCE_MUST_VERIFY flag in the tsc clocksource.

Thanks,

	tglx


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