On Wed, 22 Jun 2016, Arnd Bergmann wrote:
Regarding the "Support for non-Y2038-safe kernels" section, I'm not sure if that can work at all: A kernel that does not have the appropriate system calls will also not have the handlers for a lot of the ioctl commands and possibly other interfaces that rely on a specific structure layout. If we can instead enforce that __USE_TIME_BITS64
Maybe it's hard for ioctls, but I see no reason it shouldn't work for applications using normal non-ioctl glibc interfaces, with runtime fallbacks in glibc such as have been used for plenty of previous kernel features.
Of course eventually we remove support for the older kernels - when they are no longer on the list at https://www.kernel.org/category/releases.html unless something comes up like the issue with people expecting to use new glibc on old virtualization solutions only supporting 2.6.32 kernels - but it would be good for people and distributions to be using / testing _TIME_BITS=64 before they reach the point of ceasing to support any older kernels.