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

   1 /* Copyright (C) 2000, 2001, 2003, 2004, 2005 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, write to the Free
  16    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  17    02111-1307 USA.  */
  18
  19 #include <errno.h>
  20 #include <fcntl.h>
  21 #include <unistd.h>
  22 #include <sys/stat.h>
  23 #include <sys/types.h>
  24 #include <not-cancel.h>
  25
  26 static int itc_usable;
  27
  28 static int
  29 has_cpuclock (void)
  30 {
  31   if (__builtin_expect (itc_usable == 0, 0))
  32     {
  33       int newval = 1;
  34       int fd = open_not_cancel_2 ("/proc/sal/itc_drift", O_RDONLY);
  35       if (__builtin_expect (fd != -1, 1))
  36         {
  37           char buf[16];
  38           /* We expect the file to contain a single digit followed by
  39              a newline.  If the format changes we better not rely on
  40              the file content.  */
  41           if (read_not_cancel (fd, buf, sizeof buf) != 2
  42               || buf[0] != '0' || buf[1] != '\n')
  43             newval = -1;
  44
  45           close_not_cancel_no_status (fd);
  46         }
  47
  48       itc_usable = newval;
  49     }
  50
  51   return itc_usable;
  52 }