linux-kernel - Re: [PATCH] Close small window for vsyscall time inconsistencies

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Date:	Mon, 7 Apr 2008 08:27:55 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Roman Zippel <zippel@...ux-m68k.org>
cc:	john stultz <johnstul@...ibm.com>,
	Paul Mackerras <paulus@...ba.org>,
	Tony Luck <tony.luck@...el.com>, Ingo Molnar <mingo@...e.hu>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Close small window for vsyscall time inconsistencies

On Mon, 7 Apr 2008, Roman Zippel wrote:
> Hi,
> 
> On Friday 4. April 2008, john stultz wrote:
> 
> > So Thomas and Ingo pointed out to me that they were occasionally seeing
> > small 1ns inconsistencies from clock_gettime() (and more rarely, 1us
> > inconsistencies from gettimeofday() when the 1ns inconsistency occurred
> > on a us boundary)
> 
> What does inconsistency mean?

Time is going backwards by 1us/1nsec.
 
> So instead of shooting in the dark, I'd suggest to collect some
>  numbers first,

That's what we did and John's analysis of the problem is pretty
correct.

Thanks,
	tglx
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