Re: [RESEND PATCH 2/7] time: Change posix clocks ops interfaces to use timespec64

[Arnd Bergmann]

On Mon, Mar 20, 2017 at 9:40 PM, Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:
> On Mon, 20 Mar 2017, Deepa Dinamani wrote:
>> >> -static int ptp_clock_getres(struct posix_clock *pc, struct timespec *tp)
>> >> +static int ptp_clock_getres(struct posix_clock *pc, struct timespec64 *tp)
>> >
>> > That's a pretty pointless exercise. getres() returns the resolution of the
>> > clock which obviously can never be affected by Y2038.
>>
>> True, tv_sec does not need to be more than 32 bits here.
>> We plan to limit the use of struct timespec to existing user interfaces only.
>
> This is an existing user space interface and there is no need to change it
> at all.

I think we should change it in the kernel, otherwise every libc implementation
has to include a copy of this, to convert between the user space 16-byte
timespec and the 8-byte kernel timespec. If we do it in the kernel, we only
need one copy and the interface is consistent between 32-bit and 64-bit
user space.

The other point that Deepa made is important for verification purposes:
If we can eliminate timespec/time_t/timeval from all in-kernel code, we have
a much better chance at showing that we have no y2038 problems.
I did a private patch series to try this out a while ago, and managed to
actually get the kernel to build fine with no 32-bit time_t code left in
it (lots of minor drivers being marked in Kconfig as depending on old time_t)

       Arnd