[ntp:questions] questions] Leapsecond on FreeBSD or Windows - no showstopper bugs, but ...

Dave Hart hart at ntp.org
Wed Jul 4 14:54:38 UTC 2012


On Tue, Jul 3, 2012 at 06:20 UTC, David J Taylor wrote:
> Presumably, Dave, if the leap second /had/ been inserted, the second message
> would not have happened?

The "would have gone backward 1 times" message was triggered by the
intentional backward step, which wouldn't have occurred at the time it
did if the insertion had slewed as designed.  That diagnostic is
supposed to be suppressed when ntpd steps the clock, but the evidence
suggests imperfection.  Clearing an additional variable might be all
that's needed.

>  Personally, I would correct the missing insertion,
> and treat the second message as a warning that /something/ unexpected had
> happened!

I want to preserve the unexpected aspect by not logging that message
when the clock is expected to step back.

>  If the leap second /had/ been inserted, then would ntp have been
> confused in the period before the GPS 18/x started emitting correct seconds?

It would quickly notice a 1s offset for the NMEA, which would most
likely be suppressed initially as a popcorn spike.  Whether the clock
would be stepped to follow depends on the mix and agreement of
sources.

> I also wonder why the 1-second step doesn't appear to have been reported in
> the event log.

I wondered the same thing.  I saw a step logged on Windows ntpd with
GPS 18x LVC:

30 Jun 23:59:59 ntpd[2272]: 0.0.0.0 041b 0b leap_event
 1 Jul 00:00:00 ntpd[2272]: Leap second announcement disarmed
 1 Jul 00:00:15 ntpd[2272]: 0.0.0.0 0413 03 spike_detect -0.999998 s
 1 Jul 00:03:45 ntpd[2272]: 2001:4f8:fff7:1::17 962a 8a sys_peer
 1 Jul 00:12:29 ntpd[2272]: 0.0.0.0 061c 0c clock_step -1.006282 s
(followed by re-initializing interpolation spew normally seen only at startup)

You may need to add "+sysall" or more narrowly "+sysevent" to
logconfig in ntp.conf.

Cheers,
Dave Hart


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