Re: [PATCH 0/9] posix_clocks: Prepare syscalls for 64 bit time_t conversion

On Fri, Nov 10, 2017 at 11:42 PM, Deepa Dinamani <[email protected]> wrote:
> The series is a preparation series for individual architectures
> to use 64 bit time_t syscalls in compat and 32 bit emulation modes.
>
> This is a follow up to the series Arnd Bergmann posted:
> https://sourceware.org/ml/libc-alpha/2015-05/msg00070.html
>
> Big picture is as per the lwn article:
> https://lwn.net/Articles/643234/
>
> The series is directed at converting posix clock syscalls:
> clock_gettime, clock_settime, clock_getres and clock_nanosleep
> to use a new data structure __kernel_timespec at syscall boundaries.
> __kernel_timespec maintains 64 bit time_t across all execution modes.
>
> vdso will be handled as part of each architecture when they enable
> support for 64 bit time_t.
>
> The compat syscalls are repurposed to provide backward compatibility
> by using them as native syscalls as well for 32 bit architectures.
> They will continue to use timespec at syscall boundaries.
>
> CONFIG_64_BIT_TIME controls whether the syscalls use __kernel_timespec
> or timespec at syscall boundaries.
>
> The series does the following:
> 1. Enable compat syscalls unconditionally.
> 2. Add a new __kernel_timespec type to be used as the data structure
>    for all the new syscalls.
> 3. Add new config CONFIG_64BIT_TIME(intead of the CONFIG_COMPAT_TIME in
>    [1] and [2] to switch to new definition of __kernel_timespec. It is
>    the same as struct timespec otherwise.
>
> Arnd Bergmann (1):
>   y2038: introduce CONFIG_64BIT_TIME

The series looks good to me overall, and I've added it to my build-testing tree
to see if it shows any regressions in random configurations.

I had on concern about x32, maybe we should check
for "COMPAT_USE_64BIT_TIME" before zeroing out the tv_nsec
bits.

Regarding CONFIG_COMPAT_TIME/CONFIG_64BIT_TIME, would
it help to just leave out that part for now and unconditionally
define '__kernel_timespec' as 'timespec' until we are ready to
convert the architectures?

       Arnd