[ntp:questions] change between 4.2.8p6 and 4.2.8p10 release - SHM
Hans Mayer
hans.mayer.08 at gmail.com
Wed Mar 29 12:37:04 UTC 2017
Dear All,
My environment a GPS disciplined NTP server running on armv7l GNU/Linux with kernel 3.4.108+ gpsd version 3.15
This is the relevant part of the configuration
# Enabling PPS/ATOM support
server 127.127.22.0 minpoll 4 maxpoll 4
fudge 127.127.22.0 refid PPS time1 0.000001
fudge 127.127.22.0 flag3 1 flag4 1 # enable kernel PLL/FLL clock discipline and clockstats
# gpsd shared memory clock
server 127.127.28.0 minpoll 4 maxpoll 4 prefer # PPS requires at least one preferred peer
fudge 127.127.28.0 refid GPS
fudge 127.127.28.0 time1 +0.1565 flag4 1 # coarse processing delay offset
Now I tried to update my NTP server from version 4.2.8p6 to version 4.2.8p10.
I watched the daemon log and I can see a lot of entries like this: ( repeating and repeating )
Mar 28 09:11:01 gps0 ntpd[2445]: 0.0.0.0 0168 08 no_sys_peer
Mar 28 09:11:03 gps0 ntpd[2445]: PPS(0) 916a 8a sys_peer
Mar 28 09:11:17 gps0 ntpd[2445]: 0.0.0.0 0178 08 no_sys_peer
Mar 28 09:12:21 gps0 ntpd[2445]: PPS(0) 917a 8a sys_peer
Mar 28 09:13:57 gps0 ntpd[2445]: 0.0.0.0 0188 08 no_sys_peer
Mar 28 09:14:13 gps0 ntpd[2445]: PPS(0) 918a 8a sys_peer
Mar 28 09:15:17 gps0 ntpd[2445]: 0.0.0.0 0198 08 no_sys_peer
Mar 28 09:17:09 gps0 ntpd[2445]: PPS(0) 919a 8a sys_peer
Mar 28 09:21:25 gps0 ntpd[2445]: 0.0.0.0 01a8 08 no_sys_peer
Mar 28 09:21:57 gps0 ntpd[2445]: PPS(0) 91aa 8a sys_peer
Mar 28 09:22:13 gps0 ntpd[2445]: 0.0.0.0 01b8 08 no_sys_peer
Looking with ntpq after a no_sys_peer I see:
# ntpq -pn
remote refid st t when poll reach delay offset jitter
==============================================================================
x127.127.22.0 .PPS. 0 l 7 16 377 0.000 -0.068 0.119
x127.127.28.0 .GPS. 0 l 7 16 377 0.000 -4.665 0.688
But it should be generally
o127.127.22.0 .PPS. 0 l 13 16 377 0.000 -0.005 0.010
*127.127.28.0 .GPS. 0 l 12 16 377 0.000 46.881 1.041
So in more or less regular intervals ntpd goes into state "falsetick" but comes back to status "pps" and so on.
I changed back to version 4.2.8p6 and everything is fine.
In a test environment I figured out the issue exists with version 4.2.8p9 too. So something changed in the last 4 patch level versions.
To locate this issue a little bit I removed driver 127.127.28.0 and I used another ntp server over IP as a "preferred server".
In this case version 4.2.8p10 works fine with 127.127.22.0. So it must have something to do with the shared memory driver 127.127.28.0
Any ideas what I could do to fix this issue ?
Did someone else figure out the same issue ?
Is it worth to open a ticket ?
Kind regards
Hans
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