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glibc  2.9
smp.h
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00001 /* Determine whether the host has multiple processors.  Linux version.
00002    Copyright (C) 1996, 2002, 2004, 2006 Free Software Foundation, Inc.
00003    This file is part of the GNU C Library.
00004 
00005    The GNU C Library is free software; you can redistribute it and/or
00006    modify it under the terms of the GNU Library General Public License as
00007    published by the Free Software Foundation; either version 2 of the
00008    License, or (at your option) any later version.
00009 
00010    The GNU C Library is distributed in the hope that it will be useful,
00011    but WITHOUT ANY WARRANTY; without even the implied warranty of
00012    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00013    Library General Public License for more details.
00014 
00015    You should have received a copy of the GNU Library General Public
00016    License along with the GNU C Library; see the file COPYING.LIB.  If not,
00017    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
00018    Boston, MA 02111-1307, USA.  */
00019 
00020 #include <errno.h>
00021 #include <fcntl.h>
00022 #include <string.h>
00023 #include <sys/utsname.h>
00024 #include <not-cancel.h>
00025 
00026 /* Test whether the machine has more than one processor.  This is not the
00027    best test but good enough.  More complicated tests would require `malloc'
00028    which is not available at that time.  */
00029 static inline int
00030 is_smp_system (void)
00031 {
00032   union
00033   {
00034     struct utsname uts;
00035     char buf[512];
00036   } u;
00037   char *cp;
00038 
00039   /* Try reading the number using `sysctl' first.  */
00040   if (uname (&u.uts) == 0)
00041     cp = u.uts.version;
00042   else
00043     {
00044       /* This was not successful.  Now try reading the /proc filesystem.  */
00045       int fd = open_not_cancel_2 ("/proc/sys/kernel/version", O_RDONLY);
00046       if (__builtin_expect (fd, 0) == -1
00047          || read_not_cancel (fd, u.buf, sizeof (u.buf)) <= 0)
00048        /* This also didn't work.  We give up and say it's a UP machine.  */
00049        u.buf[0] = '\0';
00050 
00051       close_not_cancel_no_status (fd);
00052       cp = u.buf;
00053     }
00054 
00055   return strstr (cp, "SMP") != NULL;
00056 }