QNX (was: Re: Raspberry Pi NTP config with fudge factors

[Gary E. Miller]

Yo Eric!

On Fri, 6 May 2016 15:53:15 -0400
"Eric S. Raymond" <esr at thyrsus.com> wrote:

> Gary E. Miller <gem at rellim.com>:
> > > We *will* assume POSIX-compliant shared memory on our target
> > > systems.  
> > 
> > QNX has POSIX compliant shared memory, just the new one, not the
> > old one.  
> 
> Are we presently using the old one?  Where is documentation for the
> new one?

ntpd, chronyd and gpsd use shmctl(2), the old SYSVr4 interface.

The 'new' as of 2001 interface is shm_open(3).

Both are in POSIX 2001 and POSIX 2008.

man shm_overview has this to say:

       "System  V  shared  memory (shmget(2), shmop(2), etc.) is an older
       shared memory API.  POSIX shared memory provides a  simpler,  and
       better  designed interface; on the other hand POSIX shared memory
       is somewhat less widely available (especially on  older  systems)
       than System V shared memory."

In any case, they are not trivially interchangeable at the binary level.
So a refclock based on shm_open() would be a new refclock.  IMHO it would
be slightly better than shmctl(), but I'd prefer to go all the way and fix
#48, skipping these intermediate steps.


> > What about Windows?  
> 
> It too is not our problem yet.  At the rate Microsoft is now busily
> Unixizing Windows, it might not be a problem at all by the time we get
> there.  If we get there

That got a big laugh at a Penguicon panel.  I'm happy to ignore
windows.

> Besides, while there's a case for supporting NTP client mode on
> Windows, anybody who tries to use it as a primary time server is too
> stupid to live.

Never underestiate the power of large numbers of stupid people.

> > For example, TAI to UTC offset is in the JSON stream (currently
> > unused). Adding TAI offset to SHM would be a major incompatible
> > change.  
> 
> OK, so deprecate #20 and fix #48. That's still clearer direction than
> we had.

Clear?  Probably.  Universally accepted?  Not a chance.

As Obama said, if the ignorant want to cling to their guns we can't stop
them.  :-)

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