Re: [RFC v3 02/23] sysdeps/gettimeofday: Use clock_gettime64 if avaliable

[Alistair Francis <alistair23 at gmail dot com>]

On Wed, Jul 17, 2019 at 5:43 AM Lukasz Majewski <lukma@denx.de> wrote:
>
> Hi Alistair,
>
> > Not all architectures support the obsolete gettimeofday so use the
> > newer clock_gettime64 syscall if it is avaliable. This fixes RV32
> > build issues.
> >
> > Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
> > ---
> >  ChangeLog                              |  1 +
> >  sysdeps/unix/sysv/linux/gettimeofday.c | 28
> > ++++++++++++++++++++++++++ 2 files changed, 29 insertions(+)
> >
> > diff --git a/ChangeLog b/ChangeLog
> > index 477b9b49b3..9ca390a9c3 100644
> > --- a/ChangeLog
> > +++ b/ChangeLog
> > @@ -1028,6 +1028,7 @@
> >       * nptl/thrd_sleep.c: Use clock_nanosleep_time64 instead of
> > nanosleep.
> >       * sysdeps/unix/sysv/linux/nanosleep.c: Likewise.
> >       * sysdeps/unix/sysv/linux/nanosleep_nocancel.c: Likewise.
> > +     * sysdeps/unix/sysv/linux/gettimeofday.c: Use
> > clock_gettime64 syscall for gettimeofday.
> >  2019-06-20  Dmitry V. Levin  <ldv@altlinux.org>
> >           Florian Weimer  <fweimer@redhat.com>
> > diff --git a/sysdeps/unix/sysv/linux/gettimeofday.c
> > b/sysdeps/unix/sysv/linux/gettimeofday.c index a74f03825a..151b1e606c
> > 100644 --- a/sysdeps/unix/sysv/linux/gettimeofday.c
> > +++ b/sysdeps/unix/sysv/linux/gettimeofday.c
> > @@ -32,7 +32,35 @@
> >  int
> >  __gettimeofday (struct timeval *tv, struct timezone *tz)
> >  {
> > +#ifdef __ASSUME_TIME64_SYSCALLS
>
> I'm not the glibc expert but according to [1], the
> __ASSUME_TIME64_SYSCALLS will be defined also for __WORDSIZE = 64 archs.
>
> This means that this code will be executed on x86_64 and return with an
> ENOTSUPP error as those archs shall not define clock_gettime64 and
> will just use the clock_settime.
>
> Please consider re-using pattern from clock_settime conversion [2].

Yep, good point. I have updated this to better match what is being
discussed on the list and your patches.

Alistair

>
> > +  int ret;
> > +  struct __timespec64 now;
> > +
> > +  ret = INLINE_VSYSCALL (clock_gettime64, 2, CLOCK_REALTIME,
> > +                         &now);
> > +
> > +  /* Convert from timespec to timeval */
> > +  tv->tv_sec = now.tv_sec;
> > +  tv->tv_usec = now.tv_nsec / 1000;
> > +
> > +  return ret;
> > +#else
> > +# ifdef __NR_clock_gettime64
> > +  long int ret;
> > +  struct __timespec64 now;
> > +
> > +  ret = INLINE_VSYSCALL (clock_gettime64, 2, CLOCK_REALTIME,
> > +                         &now);
> > +
> > +  /* Convert from timespec to timeval */
> > +  tv->tv_sec = now.tv_sec;
> > +  tv->tv_usec = now.tv_nsec / 1000;
> > +
> > +  if (ret == 0 || errno != ENOSYS)
> > +    return ret;
> > +# endif
> >    return INLINE_VSYSCALL (gettimeofday, 2, tv, tz);
> > +#endif
> >  }
> >  libc_hidden_def (__gettimeofday)
> >  weak_alias (__gettimeofday, gettimeofday)
>
> Note:
>
> [1] -
> https://github.com/lmajewski/y2038_glibc/commit/1fdbc6002101a78a8a6a076bbb642b3082c2225d
>
> [2] -
> https://github.com/lmajewski/y2038_glibc/commit/69f842a8519ca13ed11fab0ff1bcc6fa1a524192
>
> Best regards,
>
> Lukasz Majewski
>
> --
>
> DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
> HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
> Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email: lukma@denx.de