libringbuffer/smp.c

   1 /*
   2  * libringbuffer/smp.c
   3  *
   4  * Copyright (C) 2011-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   5  *
   6  * This library is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU Lesser General Public
   8  * License as published by the Free Software Foundation; only
   9  * version 2.1 of the License.
  10  *
  11  * This library is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  14  * Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General Public
  17  * License along with this library; if not, write to the Free Software
  18  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  19  */
  20
  21 #define _GNU_SOURCE
  22 #include <unistd.h>
  23 #include "usterr.h"
  24 #include <pthread.h>
  25 #include "smp.h"
  26
  27 int __num_possible_cpus;
  28
  29 void _get_num_possible_cpus(void)
  30 {
  31         int result;
  32
  33         /* On Linux, when some processors are offline
  34          * _SC_NPROCESSORS_CONF counts the offline
  35          * processors, whereas _SC_NPROCESSORS_ONLN
  36          * does not. If we used _SC_NPROCESSORS_ONLN,
  37          * getcpu() could return a value greater than
  38          * this sysconf, in which case the arrays
  39          * indexed by processor would overflow.
  40          */
  41         result = sysconf(_SC_NPROCESSORS_CONF);
  42         if (result == -1)
  43                 return;
  44         __num_possible_cpus = result;
  45 }