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Re: [gpsd-dev] ntpd/gpsd tangle
From: |
Eric S. Raymond |
Subject: |
Re: [gpsd-dev] ntpd/gpsd tangle |
Date: |
Tue, 27 Jan 2015 17:01:44 -0500 |
User-agent: |
Mutt/1.5.23 (2014-03-12) |
Hal Murray <address@hidden>:
>
> address@hidden said:
> > OK, I want to be sure I know what's going on here. You were restarting ntpd
> > *while gpsd was running*?
>
> Sure. I've been doing that for years. It works with SHM.
>
> I assume I can start/stop/restart them in any order.
If you're using the SHM driver restarting them in any order will work.
In that case the shared-memory segment defines a fixed rendezvous; gpsd
doesn't actually care whether an ntpd instance is reading it, but just
dumps updates there. After an ntpd restart ntpd can just go back to
the rendezvous.
The socket-export case is different. For that to work, ntpd has to behave
as a GPSD client - start a session on port 2947 and issue a WATCH. It's
OK for ntpd to do this multiple times, but only if it does a new session
start and issues a new watch for each connect.
Which, now that I think about it, it certainly ought to be doing. Hmmm.
> Restarting ntpd is the same as control-Cing a random program JSONing to gpsd.
> (or having a program crash) I expect gpsd to recover from that.
You're right. I'm going to run some smoke tests and get back to you.
--
<a href="http://www.catb.org/~esr/">Eric S. Raymond</a>