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    SubjectRe: [PATCH 1/1] ntp: advertise correct TAI offset during leap second
    On 04/27/2012 11:17 PM, Richard Cochran wrote:
    > On Fri, Apr 27, 2012 at 03:23:17PM -0700, John Stultz wrote:
    >> On 04/26/2012 05:11 AM, Richard Cochran wrote:
    >>> When repeating a UTC time value during a leap second (when the UTC
    >>> time should be 23:59:60), the TAI timescale should not stop. The kernel
    >>> NTP code increments the TAI offset one second too late. This patch fixes
    >>> the issue by incrementing the offset during the leap second itself.
    >>>
    >>> Signed-off-by: Richard Cochran<richardcochran@gmail.com>
    >> This looks good to me. Although, have you actually tested against an
    >> ntp client that sets the tai offset to make sure you're not
    >> duplicating any ADJ_TAI adjustment it might make?
    > No, I cooked up my own test program that uses the adjtimex interface
    > directly. I really am not very familiar with the ntp.org software.
    >
    > Wait a minute. If user space manages this variable, then shouldn't the
    > kernel leave it alone?

    Right. That's why I'm asking. I actually haven't spent much time looking
    at how the tai value provided via adjtimex is handled, and I want to
    make sure its ok if we modify it from the kernel.


    > This David Mills paper [1] gives a leap second example that does it
    > the "other" way from Linux (see Figure 4), repeating the new epoch
    > rather than the leap second. It may well be that ntp.org servers do
    > behave that way. However, the NIST file claims that this way is
    > unusual.
    >
    > So, you have a good question. But, if ntp.org uses the NIST second
    > method, shouldn't Linux do the same?
    >
    Not sure I'm following here. In Linux 23:59:60 is represented as
    23:59:59 + TIME_OOP. Could you expand on what in particular is
    inconsistent here?

    thanks
    -john



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