nptl/sysdeps/unix/sysv/linux/i386/smp.h

   1 /* Determine whether the host has multiple processors.  Linux version.
   2    Copyright (C) 1996-2014 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Library General Public License as
   7    published by the Free Software Foundation; either version 2 of the
   8    License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Library General Public License for more details.
  14
  15    You should have received a copy of the GNU Library General Public
  16    License along with the GNU C Library; see the file COPYING.LIB.  If
  17    not, see <http://www.gnu.org/licenses/>.  */
  18
  19 #include <errno.h>
  20 #include <fcntl.h>
  21 #include <string.h>
  22 #include <sys/utsname.h>
  23 #include <not-cancel.h>
  24
  25 /* Test whether the machine has more than one processor.  This is not the
  26    best test but good enough.  More complicated tests would require `malloc'
  27    which is not available at that time.  */
  28 static inline int
  29 is_smp_system (void)
  30 {
  31   union
  32   {
  33     struct utsname uts;
  34     char buf[512];
  35   } u;
  36   char *cp;
  37
  38   /* Try reading the number using `sysctl' first.  */
  39   if (uname (&u.uts) == 0)
  40     cp = u.uts.version;
  41   else
  42     {
  43       /* This was not successful.  Now try reading the /proc filesystem.  */
  44       int fd = open_not_cancel_2 ("/proc/sys/kernel/version", O_RDONLY);
  45       if (__builtin_expect (fd, 0) == -1
  46           || read_not_cancel (fd, u.buf, sizeof (u.buf)) <= 0)
  47         /* This also didn't work.  We give up and say it's a UP machine.  */
  48         u.buf[0] = '\0';
  49
  50       close_not_cancel_no_status (fd);
  51       cp = u.buf;
  52     }
  53
  54   return strstr (cp, "SMP") != NULL;
  55 }