[ntp:questions] quirky adjtimex behaviour [SOLVED]

Dean S. Messing deanm at sharplabs.com
Tue Jan 22 01:08:00 UTC 2008

hal-usenet wrote:
> Dean Messing wrote:
> >I am seeing strange behaviour on my _x86_64 Fedora 7 desktop
> >workstation with regard to the "system-cmos" time that `adjtimex'
> >reports.
> >It seems that leaves two other possibilities: a bug in adjtimex or a
> >bug in the kernel.  That's where I am right now.
> My guess is that the system/kernel is working correctly and that
> the adjtimex utility is printing out misleading stuff.
> The CMOS/hardware clock only returns the time to the nearest second.
> I think that would cause quirks like this if the code has a loop that
> does a bit of work and sleeps for N seconds and the "bit of work"
> takes 0.1 second the time when the CMOS clock is read will drift
> by 0.1 second each time around the loop.
> If you want to play and you can find the source, try changing
> the code that reads the CMOS clock to spin in a loop reading
> it until it changes.  That will give you the time early in the
> second.

Your guess is right, Hal.

It's been nearly three weeks since I've had a few minutes to further
pursue this.  I just replaced version 1.23 of adjtimex with an old
version 1.20 and the quirky behaviour disappeared.  I first noticed it
on my new Fedora 7 with version 1.21.

When I looked on the adjtimex site I saw it was up to 1.23 so I
thought that surely this problem has been detected and fixed.  When it
didn't go away in 1.23 I looked elsewhere: 64 bit machine, new kernel,

I'll write the author and report the bug.  I'm really surprised nobody
has reported it already.


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