Re: Update kernel-features.h files for Linux 5.1

[Arnd Bergmann <arnd@arndb.de>]

On Thu, May 16, 2019 at 2:28 PM Adhemerval Zanella
<adhemerval.zanella@linaro.org> wrote:
> On 16/05/2019 08:34, Arnd Bergmann wrote:
> > On Thu, May 16, 2019 at 1:15 PM Adhemerval Zanella
> > <adhemerval.zanella@linaro.org> wrote:
> >> On 16/05/2019 05:08, Arnd Bergmann wrote:
> >>> On Fri, May 10, 2019 at 5:07 PM Adhemerval Zanella
> >>> How so? I did not expect to see any libc change here at all, unless
> >>> you mean after you stop using sys_ipc().
> >>
> >> The idea is if user configure a minimum kernel version of v5.1,
> >> sysvipc would use wire-up syscalls.  So for sys_ipc the affected
> >> architectures calls with required IPC_64, and for wire-up syscalls
> >> IPC_64 is redefined accordingly.
> >
> > Ah, I see. Is there any real advantage in doing this now though?
> > It seems to save a few cycles for each of those syscalls when building
> > for linux-5.1+, but the cost is a significant increase in source code
> > complexity.
>
> Not really, however it gave me opportunity to clean up the sysvipc code a bit
> more. I changed the __IPC_64 default value to 0x0, which simplifies a bit
> new ports additions (no need to override the value); consolidates some
> implementation a bit more (s390 is an outlier regarding semtimedop); and
> we spot an compat issues on alpha.

Ok, fair enough. Too bad this didn't come up during the review of
the kernel patches, I could probably have kept the IPC_64 flag
for the separate calls on mips/alpha/arm/microblaze/xtensa to make
it easier for you.

      Arnd