[ntp:questions] Spike detection and clock runaway

Dave Hart hart at ntp.org
Thu Feb 23 22:34:07 UTC 2012

On Thu, Feb 23, 2012 at 21:14, A C <agcarver+ntp at acarver.net> wrote:
> I had ntpd running ok for the past six days with what appeared to be no more
> problems.  The libc issues were not present (ntpq was polling regularly with
> no lockups of ntpd), PPS seemed to be working with kernel discipline enabled
> (though I have an outstanding question about PPS and the PPM adjustments).
>  It was giving me offsets of only +/-5 ms or less.
> However, very suddenly it went off track and I don't understand exactly what
> happened.  The log file is available at http://acarver.net/ntpd/

Please take a look at the graphs attached to http://bugs.ntp.org/2143
and see if it looks like the same sort of problem.  Hal Murray
identified a regression in refclock_nmea.c 4.2.7p204 affecting GPSes
reporting poor signal/lost reception.  Juergen Perlinger fixed this in

It may be a different issue, but in your shoes I'd still want p258 to
avoid confusion from fixed bugs.

Dave Hart

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