Future directions

Gary E. Miller gem at rellim.com
Tue Sep 17 03:21:44 UTC 2019

Yo Hal!

Let me make a quick retraction below:

> On Mon, 16 Sep 2019 14:09:45 -0700
> Hal Murray <hmurray at megapathdsl.net> wrote:
> > I think we should put the current stuff on the back burner and make
> > a new SHM interface where the clients are read only.  
> ntpshmmon, from gpsd, is already read-only on the SHMs.

Double checking the gpsd/ntpshmread.c file, in ntp_read(), I
see that the code support read only and read-write.

     * An update consumer such as ntpd should zero the valid flag at this point.
     * A program snooping the updates to collect statistics should not, lest
     * it make the data unavailable for consumers.
    if (consume)
        shm->valid = 0;

In gpsd only ntpshmmon uses ntp_read() and it dhas consume == false.

So you are correct that some clients may use the SHM protocol in 
rw mode.  Can't imagine why...

Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
	gem at rellim.com  Tel:+1 541 382 8588

	    Veritas liberabit vos. -- Quid est veritas?
    "If you can't measure it, you can't improve it." - Lord Kelvin
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