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    SubjectRe: PROBLEM: Linux updates RTC secretly when clock synchronizes

    > >> Just out of curiosity, what is wrong with the idea of having the
    > >> kernel at iopl(0), any kernel modules at either iopl(1) or iopl(2)
    > >> and apps at iopl(3) ??? There is obviously something, but I've no
    > >> idea what.
    > > It ... just is not that way. Kernel + modules run at ring 0,
    > > userland at ring 3.
    > I know that much. I was just curious whether there was any particular
    > reason why it was that way.
    > Somebody suggested that it was because of "scheduling hooplas" causing a
    > serious loss of performance if modules were moved to ring 1. I've no
    > idea whether such is the case

    Yep, it would be slower that way, and it would be nightmare to implement.

    > >>> No. Aim is to leave /dev/rtc in kernel, but make kernel never write
    > >>> to RTC at its own will.
    > >> I've no problem with that at all, but the bulk of the comments I've
    > >> seen in this thread have been very clear about taking /dev/rtc out
    > >> of the kernel and into a userspace daemon, with the kernel just
    > >> providing access to the relevant ports to the first app to claim
    > >> them.
    > > I do not think so.
    > >
    > > The person who tries to kill /dev/rtc from kernel is going to have
    > > some problems with me.
    > They've been getting problems from me - I just checked, and the main
    > suggestion appears to be to replace /dev/rtc with a sysctl call. I can't
    > see the point in that myself, and /dev/rtc makes far more sense to me.
    > I will add that I personally see no problem with the kernel reading RTC
    > on boot to set the syste clock, although some of the correspondents
    > appear to have problems with that idea as well.

    So we agree with each other. Good.

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