[ntp:questions] do_clock_gettime resulting in Linux crash?

John Ackermann N8UR jra at febo.com
Sun Jan 18 16:57:23 UTC 2004

Hi --

I don't know if this is a bug, or if it is, where it lives, but my 
ntp-4.2.0/Linux-2.4.21/PPSkit-2.1.2 machine is crashing after three or four 
hours of operation in PPS mode.

I'm using an HP Z3801A clock with the hpgps driver modified only to handle 
the different serial port params (19200, O71).  The system starts normally 
and ntp brings up the GPS and PPS interfaces with kernel discipline 
apparently working just fine.  Then the machine hangs, with a screenfull 
(or more) of:

do_clock_gettime: negative time warp on CPU#0: -467348901ns (0,9787444)   # 
the numbers vary

followed by:

unable to handle kernel paging request at virtual address 0004600C

This has happened twice in the last 12 hours.  A virtually identical 
hardware setup, also running ntp 4.2.0 with the same configuration, but 
using FreeBSD 4.9 instead of Linux, has not suffered from this problem.

Any pointers greatly appreciated... in the meantime I'll just disable the 
kernel discipline and see if that helps.

jra at febo.com

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