linux-kernel - Re: [PATCH -stable] ntp: Correct TAI offset during leap second

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Date:	Tue, 19 Jun 2012 12:54:48 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	Richard Cochran <richardcochran@...il.com>
Cc:	Jonathan Nieder <jrnieder@...il.com>,
	John Stultz <johnstul@...ibm.com>, stable@...r.kernel.org,
	Sasha Levin <levinsasha928@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Dave Jones <davej@...hat.com>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH -stable]  ntp: Correct TAI offset during leap second

On Mon, 2012-06-18 at 18:28 +0200, Richard Cochran wrote:
> On Mon, Jun 18, 2012 at 02:55:11PM +0100, Ben Hutchings wrote:
> > On Sun, 2012-06-17 at 19:34 +0200, Richard Cochran wrote:
> > > The offset should change upon entering state OOP, so something like
> > > the following (untested) patch should fix it for 3.2.9.
> > [...]
> > 
> > It looks like this patch just changes the offset reported by adjtimex()
> > during an inserted second; is that right?
> 
> Right, nothing really terrible will happen. The worst that I can
> imagine is that ntpd will set the new TAI offset during OOP, and then
> the kernel will add one to it, resulting in the TAI offset being off
> by one.
> 
> But I really doubt any software makes use of this information.
> 
> > Other than that, is 3.2.y likely to be OK?  Is there a good way to test
> > that in advance; does
> > <http://codemonkey.org.uk/2012/06/15/testing-leap-code/> look
> > reasonable?
> 
> Well, if you want to wait all night then that is one way to do it.

I was intending to change the clock too...

> Here is a little test program I have been using:
> 
>    https://github.com/richardcochran/leap

Thanks, that runs without incident but does show the incorrect offset
during OOP.

Ben.

-- 
Ben Hutchings
If more than one person is responsible for a bug, no one is at fault.

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