[ntp:questions] do_clock_gettime resulting in Linux crash?

Ulrich Windl Ulrich.Windl at RZ.Uni-Regensburg.DE
Mon Feb 2 14:55:08 UTC 2004


John Ackermann N8UR <jra at febo.com> writes:

> --On Sunday, January 18, 2004 11:57:23 -0500 John Ackermann N8UR
> <jra at febo.com> wrote:
> 
> > 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.

Oops! ;-)


> >
> > 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

It might be something like an overflow.

> >
> > followed by:
> >
> > unable to handle kernel paging request at virtual address 0004600C

Can you apply "ksymoops" (found in kernel source tree if nowhere else)
to the kernel output? The address alone will hardly help?


> >
> > 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.
> 
> Well, after rebooting without the "flag3 1" fudge setting under the
> PPS server, it crashed in exactly the same way, and in less than 30
> minutes of run-time.  There's something dangerously wrong here.

I will fix the problem if I can isolate it.

> 
> John

Regards,
Ulrich
P.S. I have been terribly busy recently.



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