I didn't think the -F option was correct but it didn't seem to work without
it either.  I was just hunting and pecking.  My gps does not (directly)
provide PPS.  It's a ublox 6 so I could probably wire it in but to be
honest, I don't need that much precision.  For my needs NTP is accurate
enough but it's not always available which is why I want time from GPS.  As
for the dependencies and starting order, that's easy to fix.  Right now
gpsd is starting from init.d and chrony is starting from systemd.  I can
just remove the rc#.d links and write a new .service file for gpsd with
"After = chrony.service" and "Wanted by = default.target".  Then verify the
chrony service file jives with the one for gpsd.

The last gps strace I posted was with the -D 8 option specified.   I did
not, however, specify -f to strace so it is not following after it forks.

As soon as I get some play time today I'll run some new traces.  Is
attaching the best way to send the files or is there a bit bucket somewhere
I should use?

On Aug 8, 2016 4:24 AM, "Miroslav Lichvar" <mlich...@redhat.com> wrote:

> On Sun, Aug 07, 2016 at 10:27:02PM -0400, Chris Greenman wrote:
> > I've attached the strace files.   The commands I used were:
> >
> > root@IrishMistII:/tmp# strace -o /tmp/chrony.strace.out chronyd
> > root@IrishMistII:/tmp# strace -o /tmp/gpsd.strace.out gpsd -D 8 -F
> > /var/run/chrony.ttyACM0.sock /dev/ttyACM0
>
> The -F option of gpsd is for its control socket. It's not related to
> the chrony socket. Also, I think gpsd uses the chrony socket only for
> samples based on PPS signal, so if you don't have working PPS, you'll
> probably need to stick with SHM.
>
> The problem is most likely one of the following:
> 1) gpsd is not writing to SHM
> 2) chronyd is not reading from SMH
> 3) chronyd is ignoring SHM samples (e.g. when the receive timestamp is
>    from future)
>
> Output from "gpsd -D 8" should confirm it's not 1). For 2) and 3) it
> would be best to see "chronyd -d -d" output, but this will work only
> if chronyd was compiled with debugging support (configure has
> --enable-debug option since chrony-1.30).
>
> Recent gpsd releases include a ntpshmmon tool, which can print changes
> in the SHM segment and could be useful to reject 1) and 2).
>
> --
> Miroslav Lichvar
>
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