[v2,05/11] Use clock_gettime to implement time.

  Use clock_gettime to implement time.

Changes from previous version:

  - Do not remove Linux arch-specific implementations.

  - Use CLOCK_REALTIME_COARSE for Linux.

--

Change the default implementation of time to call clock_gettime,
to align with new Linux ports that are expected to only implement
__NR_clock_gettime.  Arch-specific implementation that either call
the time vDSO or route to gettimeofday vDSO are not removed.

Also for Linux, CLOCK_REALTIME_COARSE is used instead of generic
CLOCK_REALTIME clockid.  This takes less CPU time and its behavior
better matches what the current glibc does.

Checked on x86_64-linux-gnu, i686-linux-gnu, powerpc64le-linux-gnu,
powerpc64-linux-gnu, powerpc-linux-gnu, and aarch64-linux-gnu.

Co-authored-by: Zack Weinberg <zackw@panix.com>
---
 sysdeps/unix/sysv/linux/powerpc/time.c        |  2 +-
 .../sysv/linux/{time.c => time-internal.h}    | 31 ++++---------------
 sysdeps/posix/time.c => time/time-internal.h  | 28 +++--------------
 time/time.c                                   | 13 ++++----
 4 files changed, 17 insertions(+), 57 deletions(-)
 rename sysdeps/unix/sysv/linux/{time.c => time-internal.h} (64%)
 rename sysdeps/posix/time.c => time/time-internal.h (57%)
  

On Fri, 25 Oct 2019 09:08:26 -0300
Adhemerval Zanella <adhemerval.zanella@linaro.org> wrote:

> Use clock_gettime to implement time.
> 
> Changes from previous version:
> 
>   - Do not remove Linux arch-specific implementations.
> 
>   - Use CLOCK_REALTIME_COARSE for Linux.
> 
> --
> 
> Change the default implementation of time to call clock_gettime,
> to align with new Linux ports that are expected to only implement
> __NR_clock_gettime.  Arch-specific implementation that either call
> the time vDSO or route to gettimeofday vDSO are not removed.
> 
> Also for Linux, CLOCK_REALTIME_COARSE is used instead of generic
> CLOCK_REALTIME clockid.  This takes less CPU time and its behavior
> better matches what the current glibc does.
> 
> Checked on x86_64-linux-gnu, i686-linux-gnu, powerpc64le-linux-gnu,
> powerpc64-linux-gnu, powerpc-linux-gnu, and aarch64-linux-gnu.
> 
> Co-authored-by: Zack Weinberg <zackw@panix.com>
> ---
>  sysdeps/unix/sysv/linux/powerpc/time.c        |  2 +-
>  .../sysv/linux/{time.c => time-internal.h}    | 31
> ++++--------------- sysdeps/posix/time.c => time/time-internal.h  |
> 28 +++-------------- time/time.c                                   |
> 13 ++++---- 4 files changed, 17 insertions(+), 57 deletions(-)
>  rename sysdeps/unix/sysv/linux/{time.c => time-internal.h} (64%)
>  rename sysdeps/posix/time.c => time/time-internal.h (57%)
> 
> diff --git a/sysdeps/unix/sysv/linux/powerpc/time.c
> b/sysdeps/unix/sysv/linux/powerpc/time.c index c35b80fad1..e957b81751
> 100644 --- a/sysdeps/unix/sysv/linux/powerpc/time.c
> +++ b/sysdeps/unix/sysv/linux/powerpc/time.c
> @@ -78,6 +78,6 @@ libc_hidden_def (time)
>  
>  #else
>  
> -#include <sysdeps/posix/time.c>
> +#include <time/time.c>
>  
>  #endif /* !SHARED */
> diff --git a/sysdeps/unix/sysv/linux/time.c
> b/sysdeps/unix/sysv/linux/time-internal.h similarity index 64%
> rename from sysdeps/unix/sysv/linux/time.c
> rename to sysdeps/unix/sysv/linux/time-internal.h
> index f461733678..c4c5f6b643 100644
> --- a/sysdeps/unix/sysv/linux/time.c
> +++ b/sysdeps/unix/sysv/linux/time-internal.h
> @@ -1,4 +1,5 @@
> -/* Copyright (C) 2005-2019 Free Software Foundation, Inc.
> +/* Internals of time and related functions.  Linux version.
> +   Copyright 2019 Free Software Foundation, Inc.
>     This file is part of the GNU C Library.
>  
>     The GNU C Library is free software; you can redistribute it and/or
> @@ -15,27 +16,7 @@
>     License along with the GNU C Library; if not, see
>     <https://www.gnu.org/licenses/>.  */
>  
> -#include <stddef.h>
> -#include <time.h>
> -
> -#include <sysdep.h>
> -
> -#ifdef __NR_time
> -
> -time_t
> -time (time_t *t)
> -{
> -  INTERNAL_SYSCALL_DECL (err);
> -  time_t res = INTERNAL_SYSCALL (time, err, 1, NULL);
> -  /* There cannot be any error.  */
> -  if (t != NULL)
> -    *t = res;
> -  return res;
> -}
> -libc_hidden_def (time)
> -
> -#else
> -
> -# include <sysdeps/posix/time.c>
> -
> -#endif
> +/* Timer used on clock_gettime for time implementation.  For Linux
> +   it uses the coarse version which returns the time at the last tick
> +   and mimic what time as syscall should return.  */
> +#define TIME_CLOCK_GETTIME_CLOCKID CLOCK_REALTIME_COARSE
> diff --git a/sysdeps/posix/time.c b/time/time-internal.h
> similarity index 57%
> rename from sysdeps/posix/time.c
> rename to time/time-internal.h
> index 0ab31bd7b6..f448f64191 100644
> --- a/sysdeps/posix/time.c
> +++ b/time/time-internal.h
> @@ -1,4 +1,5 @@
> -/* Copyright (C) 1991-2019 Free Software Foundation, Inc.
> +/* Internals of time and related functions.
> +   Copyright 2019 Free Software Foundation, Inc.
>     This file is part of the GNU C Library.
>  
>     The GNU C Library is free software; you can redistribute it and/or
> @@ -15,26 +16,5 @@
>     License along with the GNU C Library; if not, see
>     <https://www.gnu.org/licenses/>.  */
>  
> -#include <stddef.h>		/* For NULL.  */
> -#include <time.h>
> -#include <sys/time.h>
> -
> -
> -/* Return the current time as a `time_t' and also put it in *T if T
> is
> -   not NULL.  Time is represented as seconds from Jan 1 00:00:00
> 1970.  */ -time_t
> -time (time_t *t)
> -{
> -  struct timeval tv;
> -  time_t result;
> -
> -  if (__gettimeofday (&tv, (struct timezone *) NULL))
> -    result = (time_t) -1;
> -  else
> -    result = (time_t) tv.tv_sec;
> -
> -  if (t != NULL)
> -    *t = result;
> -  return result;
> -}
> -libc_hidden_def (time)
> +/* Timer used on clock_gettime for time implementation.  */
> +#define TIME_CLOCK_GETTIME_CLOCKID CLOCK_REALTIME
> diff --git a/time/time.c b/time/time.c
> index b53a06e29c..09a2b4fc88 100644
> --- a/time/time.c
> +++ b/time/time.c
> @@ -15,19 +15,18 @@
>     License along with the GNU C Library; if not, see
>     <https://www.gnu.org/licenses/>.  */
>  
> -#include <errno.h>
>  #include <time.h>
> +#include <time-internal.h>
>  
>  /* Return the time now, and store it in *TIMER if not NULL.  */
>  time_t
>  time (time_t *timer)
>  {
> -  __set_errno (ENOSYS);
> +  struct timespec ts;
> +  __clock_gettime (TIME_CLOCK_GETTIME_CLOCKID, &ts);
>  
> -  if (timer != NULL)
> -    *timer = (time_t) -1;
> -  return (time_t) -1;
> +  if (timer)
> +    *timer = ts.tv_sec;
> +  return ts.tv_sec;
>  }
>  libc_hidden_def (time)
> -
> -stub_warning (time)

Reviewed-by: Lukasz Majewski <lukma@denx.de>


Best regards,

Lukasz Majewski

--

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