alt Hacker NewsYes I would assume that the NTP daemon would handle a leap second arrival with guarantees of (1) gradual application over a longer period and (2) never moving the clock backwards, only slowing it a little.
I wonder if all NTP implementations don't follow those guarantees?
Oh and another app that hates clock jumps used to be sshd; it would just bail out and drop all connections. We found that out while chasing ANOTHER bug in SunOS on a T4: they didn't have it mutexed right so it possible to read its RTC register while it was in the middle of getting updated so the client would read a garbage time. We chased NTP for a week before realizing it was the kernel.
The insanity is that both NTP and unix timestamps need to be wound back during a leap second, as well as computer hardware clocks. If we just had monotonic clocks everwhere and adjusted for leap seconds in presentation then we wouldn't have many of the associated problems.
It's not like we wound back by 24 hours on leap days, that would be insanity. So in addition of leapseconds being a rare problem, it's also handled in a uniquely bad way.