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Re: [Ntp] Antw: [EXT] Re: CLOCK_TAI (was NTPv5: big picture)

Warner Losh <imp@bsdimp.com> Fri, 08 January 2021 15:30 UTC

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From: Warner Losh <imp@bsdimp.com>
Date: Fri, 08 Jan 2021 08:30:43 -0700
Message-ID: <CANCZdfrgouDSOyzjwWZS+gHNhYJt-i-O7QO902hXGWbSzx+Pgg@mail.gmail.com>
To: Martin Burnicki <martin.burnicki=40meinberg.de@dmarc.ietf.org>
Cc: Doug Arnold <doug.arnold@meinberg-usa.com>, Ulrich Windl <Ulrich.Windl@rz.uni-regensburg.de>, "mlichvar@redhat.com" <mlichvar@redhat.com>, "emmanuel.fuste@thalesgroup.com" <emmanuel.fuste@thalesgroup.com>, "ntp@ietf.org" <ntp@ietf.org>, "magnus@rubidium.se" <magnus@rubidium.se>
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Subject: Re: [Ntp] Antw: [EXT] Re: CLOCK_TAI (was NTPv5: big picture)
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On Fri, Jan 8, 2021, 8:22 AM Martin Burnicki <martin.burnicki=
40meinberg.de@dmarc.ietf.org> wrote:

> Doug Arnold wrote:
> > I think that the point of a leap smear is that no special handling of
> leap seconds is needed by the client.  It is introduced gradually over a
> number of polling periods.
>
> That's exactly the point. You want to hide the leap second from the
> client to avoid that *applications* run into problems when the kernel
> just steps the time back by 1 second.
>

My fundamental position on leap seconds hasn't changed in 20 years: they
are evil and must die. Earth clocks and atomic clocks need a different way
to synchronize. Leap seconds generate dozens of edge cases, operational
difficulties and data dependencies that complicate time for everyone and
all that added complication has a cost that far exceeds the benefit.

Smearing is the latest way to paper over all this and keep applications
naive. I'm not sure if I view it as a brilliant hack to protect the
applications from a rushed standard we are stuck with, or a deeply worrying
"enabling" of bad behavior by applications, libraries and operating
systems.

Warner

Martin
> --
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>
> Senior Software Engineer
>
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