| Re: [chrony-dev] Leap second handling |
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On Tue, Jul 10, 2012 at 01:46:33PM +0200, Frank Muzzulini wrote:
> Hello,
>
> sadly I was not able to observe the leap second in June and I also
> found that the online documentation gives little information about
> how chrony handles a leap second. I guess it forwards the
> information to the kernel, doesn't it?
It does, I saw the looping bug on some machines running chrony.
> You may have heard about the the problems some linux systems had and
> the solution implemented by Google. (If you haven't, look at http://www.h-online.com/open/news/item/Leap-second-Linux-can-freeze-1629805.html).
> I wonder if chrony could add something like that as an option, too.
The leap smear can be used only if you don't care much about clock
accuracy as the error will be up to 1 second. Chrony could implement
something like that, but it couldn't be enabled by default.
>
> Alternatively I can also imagine a simpler way: Pass the leap second
> announcement to clients as usual and locally adapt the time as if it
> were an error of one second, encountered at 0:00 UTC. If clients use
> the same setting, it will work neatly for all anyway.
Yes, that would be an option.
I think there are these options:
- let the kernel handle the leap second
- step the clock manually (settimeofday() or adjtimex(ADJ_SETOFFSET))
- smear both local time and served time, drop the leap announcement
- smear only local time, keep the announcement and always serve UTC
I really hope leap seconds will be abolished before the next one
happens. :)
--
Miroslav Lichvar
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