Guy, The "kernel clock" is an atomic variable that increments once each second. A leap is implemented following the increment at second 23:59 at which time the kernel clock is decremented, with the net effect the second remains the same as during second 23:59. That's how the kernel works, and I apologize for whatever confusion has been caused.
The issue about stepping backware is more subtle. Sometimes the clock discipline needs to correct the clock backwards a smidgin. In the code that leaves here the clock is stopped if the backward correction is less than one second and stepped if more than that. In this context a step would only occur if a backwards step more than one second was made by the Unix settimeofday() was called. Dave Guy Macon wrote: > David L. Mills wrote: > > >>Guy Macon wrote: >> >>The kernel clock reading routine... >> >> >>>The NTP clock... > > > Just to make sure I am not confused, do the clock kept by the > kernal and the clock transmitted by the NTP protocol track > each other (ignoring small errors/offsets) as they traverse > the leap second? I need to study the references given further, > but the descriptions of NTP seem to describe a clock that jumps > back a second while the descriptions of the kernel seem to > describe a clock that is monotonic and never jumps backward. > > That's how I read the figure at > [ http://www.eecis.udel.edu/~mills/leap.html ]. > > Could it be that I read a post about "the clock" stopping and > assumed from it being posted in comp.protocols.time.ntp that > it refferred to the NTP clock, followed by my posting about > "the clock" and getting a reply that assumed from the fact that > the post I replied to was about the kernel clock that I was > also referring to the kernel clock? Of course I, being a hardware > engineer and in no way an expert in this area, may be totally > misunderstanding things. If so, please forgive my ignorance. > _______________________________________________ questions mailing list [email protected] https://lists.ntp.isc.org/mailman/listinfo/questions
