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    SubjectRTC clock update - was: Re: Strange messages in log
    On Thu, Jan 13, 2000 at 10:11:45PM +0000, wayne@moneyworld.co.uk wrote:
    > Hi there,
    >
    > Before I start, I am running kernel 2.2.12 on a RedHat 6.0 box.
    >
    > I've just noticed some weird messages in the /var/log/messages on one of
    > my machines... A section of the log is attached... The mesages I am
    > worried about are the ones like
    > Jan 13 22:04:33 he4 kernel: set_rtc_mmss: can't update from 53 to 4
    >
    > Is this a problem and if so, is it known ?
    >
    > ---------------------
    >
    > Jan 13 22:04:33 he4 kernel: set_rtc_mmss: can't update from 53 to 4
    > Jan 13 22:05:34 he4 kernel: set_rtc_mmss: can't update from 53 to 5
    > Jan 13 22:06:35 he4 kernel: set_rtc_mmss: can't update from 53 to 6
    > Jan 13 22:07:36 he4 kernel: set_rtc_mmss: can't update from 53 to 7
    > -------------------------

    This means that you somehow triggered the infamous "11-minute RTC update"
    where the kernel fiddles with RTC every 11 minutes, because it thinks
    the RTC contents is worthless compared to its own superior data.
    Such things happen if you use software that calls adjtimex(), for example xntpd.

    It furthermore means that the kernel reports that its attempt at
    fiddling failed. Since the kernel does not want to know too much
    (it assumes that RTC time and kernel time should differ by an
    integral number of half hours, never mind the people in Nepal)
    it will not touch the hours part of the RTC and if an update would
    require changing the hours part it comes with this printk and waits
    for another opportunity.

    Finally, it means that either your RTC is stopped or is not being read
    correctly. You might experiment a bit with a recent hwclock.
    If the kernel fiddling can cause the RTC to stop, that would be
    one more reason to consider removing this code.

    Since the RTC is not used anywhere, this kernel fiddling is fairly
    useless, and if it fails, the failure is fairly harmless.
    The only thing is that you may have a strange time and/or date
    immediately after the next reboot.

    Andries



    [Note also that there may be a bad interaction between the kernel
    11-minute mode and hwclock --adjust. Hwclock tries to find the drift
    of the RTC, and if it looks at the RTC before and after a kernel adjustment
    it will conclude that the RTC has an enormous drift. Thus, you may find
    that /etc/adjtime contains ridiculous numbers.]

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