linux-kernel - CMOS time jumps when ntpd ist running

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Message-Id: <200908111000.01316.jbe@pengutronix.de>
Date:	Tue, 11 Aug 2009 10:00:00 +0200
From:	Juergen Beisert <jbe@...gutronix.de>
To:	linux-kernel@...r.kernel.org
Subject: CMOS time jumps when ntpd ist running

Hi list,

anybody here who saw such CMOS clock behaviour when ntpd is running?
I synced system and CMOS time and after that I ran a simple
  'watch -t -n 300 "date; hwclock -u" > /logfile'
(note: When the ntpd daemon is not running, the CMOS clock does not show this 
behaviour):

[...]
    Mon Aug 10 03:53:20 CEST 2009              <-- system time
    Mon Aug 10 03:53:20 2009  0.000000 seconds <-- CMOS time

    Mon Aug 10 03:58:20 CEST 2009
    Mon Aug 10 03:58:20 2009  0.000000 seconds

    Mon Aug 10 04:03:20 CEST 2009
    Sun Aug  9 22:03:20 2009  0.000000 seconds <----- BANG !!!!!!111!1!!

    Mon Aug 10 04:08:20 CEST 2009
    Sun Aug  9 22:08:20 2009  0.000000 seconds
[...]

It seems its always -6 hours the CMOS clock jumps. And sometimes -(6h + n * 
24h) with n from 1 to 3 I saw.

Is my CMOS clock broken? (BTW: x86 arch, 32 bit, Linux kernel 2.6.28.10 and 
there is no SMM code in the system, it runs coreboot)

Regards
Juergen
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