Re: [PATCH v2 2/6] linux: Assume clock_getres CLOCK_{PROCESS,THREAD}_CPUTIME_ID

[Adhemerval Zanella <adhemerval.zanella@linaro.org>]

Ping.

On 18/02/2019 18:11, Adhemerval Zanella wrote:
> Changes from previous version:
> 
>   - Remove ia64 itc drift check and assume kernel handles it correctly.
> 
> ---
> 
> This patch assumes that clock_getres syscall always support
> CLOCK_PROCESS_CPUTIME_ID and CLOCK_THREAD_CPUTIME_ID, so there is no need
> to fallback to hp-timing support for _SC_MONOTONIC_CLOCK.  This allows
> simplify the sysconf support to always use the syscall.
> 
> The ia64 implementation is also simplified and consolidate in one file.
> 
> Checked on aarch64-linux-gnu, x86_64-linux-gnu, and i686-linux-gnu.
> 
> 	* sysdeps/unix/sysv/linux/ia64/has_cpuclock.c: Remove file.
> 	* sysdeps/unix/sysv/linux/ia64/sysconf.c: Likewise.
> 	* sysdeps/unix/sysv/linux/sysconf.c (has_cpuclock): Remove function.
> 	(check_clock_getres): New function.
> 	(__sysconf): Use check_clock_getres instead of has_cpuclock.
> ---
>  sysdeps/unix/sysv/linux/ia64/has_cpuclock.c | 51 ---------------------
>  sysdeps/unix/sysv/linux/ia64/sysconf.c      | 30 ------------
>  sysdeps/unix/sysv/linux/sysconf.c           | 48 ++++++-------------
>  3 files changed, 13 insertions(+), 116 deletions(-)
>  delete mode 100644 sysdeps/unix/sysv/linux/ia64/has_cpuclock.c
>  delete mode 100644 sysdeps/unix/sysv/linux/ia64/sysconf.c
> 
> diff --git a/sysdeps/unix/sysv/linux/ia64/has_cpuclock.c b/sysdeps/unix/sysv/linux/ia64/has_cpuclock.c
> deleted file mode 100644
> index b3afb37f8b..0000000000
> --- a/sysdeps/unix/sysv/linux/ia64/has_cpuclock.c
> +++ /dev/null
> @@ -1,51 +0,0 @@
> -/* Copyright (C) 2000-2019 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
> -   modify it under the terms of the GNU Lesser General Public
> -   License as published by the Free Software Foundation; either
> -   version 2.1 of the License, or (at your option) any later version.
> -
> -   The GNU C Library is distributed in the hope that it will be useful,
> -   but WITHOUT ANY WARRANTY; without even the implied warranty of
> -   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> -   Lesser General Public License for more details.
> -
> -   You should have received a copy of the GNU Lesser General Public
> -   License along with the GNU C Library; if not, see
> -   <http://www.gnu.org/licenses/>.  */
> -
> -#include <errno.h>
> -#include <fcntl.h>
> -#include <unistd.h>
> -#include <sys/stat.h>
> -#include <sys/types.h>
> -#include <not-cancel.h>
> -
> -static int itc_usable;
> -
> -static int
> -has_cpuclock (void)
> -{
> -  if (__builtin_expect (itc_usable == 0, 0))
> -    {
> -      int newval = 1;
> -      int fd = __open_nocancel ("/proc/sal/itc_drift", O_RDONLY);
> -      if (__builtin_expect (fd != -1, 1))
> -	{
> -	  char buf[16];
> -	  /* We expect the file to contain a single digit followed by
> -	     a newline.  If the format changes we better not rely on
> -	     the file content.  */
> -	  if (__read_nocancel (fd, buf, sizeof buf) != 2
> -	      || buf[0] != '0' || buf[1] != '\n')
> -	    newval = -1;
> -
> -	  __close_nocancel_nostatus (fd);
> -	}
> -
> -      itc_usable = newval;
> -    }
> -
> -  return itc_usable;
> -}
> diff --git a/sysdeps/unix/sysv/linux/ia64/sysconf.c b/sysdeps/unix/sysv/linux/ia64/sysconf.c
> deleted file mode 100644
> index ef75322f1f..0000000000
> --- a/sysdeps/unix/sysv/linux/ia64/sysconf.c
> +++ /dev/null
> @@ -1,30 +0,0 @@
> -/* Get file-specific information about a file.  Linux/ia64 version.
> -   Copyright (C) 2003-2019 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
> -   modify it under the terms of the GNU Lesser General Public
> -   License as published by the Free Software Foundation; either
> -   version 2.1 of the License, or (at your option) any later version.
> -
> -   The GNU C Library is distributed in the hope that it will be useful,
> -   but WITHOUT ANY WARRANTY; without even the implied warranty of
> -   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
> -   Lesser General Public License for more details.
> -
> -   You should have received a copy of the GNU Lesser General Public
> -   License along with the GNU C Library; if not, see
> -   <http://www.gnu.org/licenses/>.  */
> -
> -#include <assert.h>
> -#include <stdbool.h>
> -#include <stdlib.h>
> -#include <unistd.h>
> -
> -
> -#include "has_cpuclock.c"
> -#define HAS_CPUCLOCK(name) (has_cpuclock () ? _POSIX_VERSION : -1)
> -
> -
> -/* Now the generic Linux version.  */
> -#include <sysdeps/unix/sysv/linux/sysconf.c>
> diff --git a/sysdeps/unix/sysv/linux/sysconf.c b/sysdeps/unix/sysv/linux/sysconf.c
> index 4b297ba35f..2027444488 100644
> --- a/sysdeps/unix/sysv/linux/sysconf.c
> +++ b/sysdeps/unix/sysv/linux/sysconf.c
> @@ -35,33 +35,18 @@
>  static long int posix_sysconf (int name);
>  
>  
> -#ifndef HAS_CPUCLOCK
>  static long int
> -has_cpuclock (int name)
> +check_clock_getres (clockid_t clk_id)
>  {
> -# if defined __NR_clock_getres || HP_TIMING_AVAIL
> -  /* If we have HP_TIMING, we will fall back on that if the system
> -     call does not work, so we support it either way.  */
> -#  if !HP_TIMING_AVAIL
> -  /* Check using the clock_getres system call.  */
>    struct timespec ts;
>    INTERNAL_SYSCALL_DECL (err);
> -  int r = INTERNAL_SYSCALL (clock_getres, err, 2,
> -			    (name == _SC_CPUTIME
> -			     ? CLOCK_PROCESS_CPUTIME_ID
> -			     : CLOCK_THREAD_CPUTIME_ID),
> -			    &ts);
> +  /* Avoid setting errno to we can check whether the kernel supports
> +     the CLK_ID.  */
> +  int r = INTERNAL_SYSCALL_CALL (clock_getres, err, clk_id, &ts);
>    if (INTERNAL_SYSCALL_ERROR_P (r, err))
>      return -1;
> -#  endif
>    return _POSIX_VERSION;
> -# else
> -  return -1;
> -# endif
>  }
> -# define HAS_CPUCLOCK(name) has_cpuclock (name)
> -#endif
> -
>  
>  /* Get the value of the system variable NAME.  */
>  long int
> @@ -71,29 +56,21 @@ __sysconf (int name)
>  
>    switch (name)
>      {
> -      struct rlimit rlimit;
> -#ifdef __NR_clock_getres
>      case _SC_MONOTONIC_CLOCK:
> -      /* Check using the clock_getres system call.  */
> -      {
> -	struct timespec ts;
> -	INTERNAL_SYSCALL_DECL (err);
> -	int r;
> -	r = INTERNAL_SYSCALL (clock_getres, err, 2, CLOCK_MONOTONIC, &ts);
> -	return INTERNAL_SYSCALL_ERROR_P (r, err) ? -1 : _POSIX_VERSION;
> -      }
> -#endif
> -
> +      return check_clock_getres (CLOCK_MONOTONIC);
>      case _SC_CPUTIME:
> +      return check_clock_getres (CLOCK_PROCESS_CPUTIME_ID);
>      case _SC_THREAD_CPUTIME:
> -      return HAS_CPUCLOCK (name);
> +      return check_clock_getres (CLOCK_THREAD_CPUTIME_ID);
>  
> -    case _SC_ARG_MAX:
> +    case _SC_ARG_MAX: {
> +      struct rlimit rlimit;
>        /* Use getrlimit to get the stack limit.  */
>        if (__getrlimit (RLIMIT_STACK, &rlimit) == 0)
>  	return MAX (legacy_ARG_MAX, rlimit.rlim_cur / 4);
>  
>        return legacy_ARG_MAX;
> +    } break;
>  
>      case _SC_NGROUPS_MAX:
>        /* Try to read the information from the /proc/sys/kernel/ngroups_max
> @@ -101,13 +78,14 @@ __sysconf (int name)
>        procfname = "/proc/sys/kernel/ngroups_max";
>        break;
>  
> -    case _SC_SIGQUEUE_MAX:
> +    case _SC_SIGQUEUE_MAX: {
> +      struct rlimit rlimit;
>        if (__getrlimit (RLIMIT_SIGPENDING, &rlimit) == 0)
>  	return rlimit.rlim_cur;
>  
>        /* The /proc/sys/kernel/rtsig-max file contains the answer.  */
>        procfname = "/proc/sys/kernel/rtsig-max";
> -      break;
> +    } break;
>  
>      default:
>        break;
>