linux-kernel - Re: Regression in 2.6.27 caused by commit bfc0f59

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Date:	Mon, 01 Sep 2008 15:23:22 -0500
From:	Larry Finger <Larry.Finger@...inger.net>
To:	Thomas Gleixner <tglx@...utronix.de>
CC:	LKML <linux-kernel@...r.kernel.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Alok Kataria <akataria@...are.com>,
	Michael Buesch <mb@...sch.de>
Subject: Re: Regression in 2.6.27 caused by commit bfc0f59

Thomas Gleixner wrote:
> On Mon, 1 Sep 2008, Larry Finger wrote:
>> The timed sleep is as accurate as I can measure.
>>
>> I put in some test prints. The value of pm2 is zero when the else branch of
>> the "if (hpet)" is entered; however, pm1 is 15768471. When we reach the
>> do_div(tsc2, tsc1) statement, tsc2 is zero, which I think means that the two
>> calls to tsc_read_refs() are returning the same junk value.
> 
> Ok, so the pmtimer is probably detected later as unusable and disabled.
> Please check your logs for: 
> "PM-Timer had inconsistent results:"

Booting 2.6.26, the dmesg output has a line that says:

PM-Timer running at invalid rate: 200% of normal - aborting.

Amazing that it should be exactly 200%. Why is the CPU running at half 
speed when the PM-Timer rate is measured?

Larry
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