[ntp:questions] Problem: ntpd will not stop when using Pharos GPS reference clock

Phil Stracchino phils at caerllewys.net
Mon Nov 14 13:27:59 UTC 2011


I am using a Pharos GPS-500 Model X13-51914 GPS sensor from a MS DeLorme
mapping package as a stratum 0 timesource for my local timeserver.  (As
a matter of fact, I bought the sensor for that purpose.)  It is working
beautifully, and reporting zero jitter once I turned the port up to
115200bps.

There's just one problem, which comes up when I need to shut down the
machine, reboot, or otherwise stop ntpd for any reason.  If ntpd has
been running for more than a short period (I'm not sure how long the
"safe" run time is)), it will fail to stop, and will in fact completely
lock up the system.  I can sometimes, not always, get it to stop
properly by sending it a SIGKILL instead of SIGTERM.

The GPS sensor, on its USB-serial converter, shows up on the USB bus
like so:

babylon5:alaric:~:3 $ lsusb
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 003 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 004 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 001 Device 005: ID 058f:6361 Alcor Micro Corp. Multimedia Card Reader
Bus 004 Device 002: ID 03f0:1105 Hewlett-Packard ScanJet 5470c/5490c
Bus 004 Device 003: ID 045e:0040 Microsoft Corp. Wheel Mouse Optical
Bus 004 Device 004: ID 067b:aaa0 Prolific Technology, Inc. Prolific Pharos
Bus 003 Device 002: ID 04d9:1603 Holtek Semiconductor, Inc.

The reference clock is configured as follows in ntp.conf:

server 127.127.20.0 prefer minpoll 4 mode 80
fudge 127.127.20.0 flag3 1 flag2 0 time1 0.0 stratum 0

Kernel modules in use for GPS:

pps_ktimer              1394  0
pps_ldisc               1987  0
pps_core                6394  2 pps_ktimer,pps_ldisc
pl2303                 11242  1
usbserial              31191  3 pl2303


This failure-to-stop occurs ONLY with the GPS sensor in use.

Has anyone encountered a similar problem?  Any suggestions as to
possible cause or workaround?  Do I perhaps need to disconnect the GPS
sensor (or perhaps just unload the applicable kernel modules) before
trying to stop ntpd?


Any tips would be appreciated.


-- 
  Phil Stracchino
  Babylon Communications
  phils at caerllewys.net
  phil at co.ordinate.org
  Landline: 603.293.8485


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