netdev - Re: [PATCH V8 02/13] ntp: add ADJ

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Date:	Mon, 10 Jan 2011 08:49:05 -0800
From:	john stultz <johnstul@...ibm.com>
To:	"Kuwahara,T." <6vvetjsrt26xsrzlh1z0zn4d2grdah@...il.com>
Cc:	Richard Cochran <richardcochran@...il.com>,
	linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
	netdev@...r.kernel.org, Alan Cox <alan@...rguk.ukuu.org.uk>,
	Arnd Bergmann <arnd@...db.de>,
	Christoph Lameter <cl@...ux.com>,
	David Miller <davem@...emloft.net>,
	Krzysztof Halasa <khc@...waw.pl>,
	Peter Zijlstra <peterz@...radead.org>,
	Rodolfo Giometti <giometti@...ux.it>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH V8 02/13] ntp: add ADJ_SETOFFSET mode bit

On Mon, 2011-01-10 at 06:07 +0900, Kuwahara,T. wrote:
> On Sun, Jan 9, 2011 at 2:50 AM, Richard Cochran
> <richardcochran@...il.com> wrote:
> > we want to be able to jump the clock arbitrarily.
> 
> Another problem remains:  How do you deal with leap seconds?  I mean,
> given that 1 minute is not always 60 seconds, then what time was it
> XXXXX seconds ago?   Maybe some kind of lookup table is necessary, but
> in such case, isn't it a better choice just to use the
> clock_settime/settimeofday syscall?

Leapsecond processing is done via an absolute hrtimer. Thus when the
time offset is set, the hrtimers that should have expired will fire
(just like with settimeofday) and the adjustment will then be made.

thanks
-john







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