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

[Adhemerval Zanella <adhemerval dot zanella at linaro dot org>]

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;
-- 
2.17.1