In article <87llaeobbu.fsf@qrnik.zagroda>,
Marcin 'Qrczak' Kowalczyk
For example there would be new syscalls for TAI time; a new kernel would treat the hardware clock as TAI and compute UTC from this when a process asks for gettimeofday (which is more accurate than the other direction); glibc would nevertheless translate in the other direction when run on an old kernel, so programs would work at all; and there would be a central place to keep the leap second table, with a special program to notify the kernel about updates (which would propagate to running processes); and NTP clients would be enhanced to use the new API when avaiable.
This turns out not at all hard to do in Linux with a kernel module, since they can intercept system calls and provide new ones very easily. Incidentally, I came across an amusing solution to make gettimeofday always tell correct UTC time, from http://lkml.org/lkml/1998/9/9/50:
Actually, I think Ulrich was present when I proposed a similar solution: gettimeofday() will not return during 23:59:60. If a process calls gettimeofday() during a leap second, then the call will sleep until 0:00:00 when it can return the correct result.
This horrified the real-time people. It is, however, strictly speaking, completely correct.
-- Ashley Yakeley, Seattle WA