linux: Assume clock_getres CLOCK_{PROCESS,THREAD}_CPUTIME_ID

The Linux 3.2 clock_getres kernel code (kernel/posix-cpu-timers.c)
issued for clock_getres CLOCK_PROCESS_CPUTIME_ID (process_cpu_clock_getres)
and CLOCK_THREAD_CPUTIME_ID (thread_cpu_clock_getres) call
posix_cpu_clock_getres. And it fails on check_clock only if an invalid
clock is used (not the case) or if we pass an invalid the pid/tid in
29 msb of clock_id (not the case either).

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 neither to issue
the syscall to certify the clock_id is supported bt the kernel.  This
allows simplify the sysconf support to always use the syscall.

it also removes ia64 itc drift check and assume kernel handles it correctly.

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.
	(__sysconf): Assume kernel support for _SC_MONOTONIC_CLOCK,
	_SC_CPUTIME, and _SC_THREAD_CPUTIME.

ChangeLog

@@ -1,5 +1,11 @@
 2019-03-22  Adhemerval Zanella  <adhemerval.zanella@linaro.org>
 
+	* 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.
+	(__sysconf): Assume kernel support for _SC_MONOTONIC_CLOCK,
+	_SC_CPUTIME, and _SC_THREAD_CPUTIME.
+
 	* nptl/Makefile (libpthread-routines): Remove pthread_clock_gettime and
 	pthread_clock_settime.
 	* nptl/pthreadP.h (__find_thread_by_id): Remove prototype.

sysdeps/unix/sysv/linux/ia64/has_cpuclock.c

@@ -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;
-}

sysdeps/unix/sysv/linux/ia64/sysconf.c

@@ -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>

sysdeps/unix/sysv/linux/sysconf.c

@@ -35,34 +35,6 @@
 static long int posix_sysconf (int name);
 
 
-#ifndef HAS_CPUCLOCK
-static long int
-has_cpuclock (int name)
-{
-# 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);
-  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
 __sysconf (int name)
@@ -71,29 +43,20 @@ __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
-
     case _SC_CPUTIME:
     case _SC_THREAD_CPUTIME:
-      return HAS_CPUCLOCK (name);
+      return _POSIX_VERSION;
 
     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;
+      }
 
     case _SC_NGROUPS_MAX:
       /* Try to read the information from the /proc/sys/kernel/ngroups_max
@@ -102,11 +65,14 @@ __sysconf (int name)
       break;
 
     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;
 
     default: