libringbuffer/smp.c

   1 /*
   2  * libringbuffer/smp.c
   3  *
   4  * Copyright 2011 (c) - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   5  *
   6  * Dual LGPL v2.1/GPL v2 license.
   7  */
   8
   9 #include <unistd.h>
  10 #include "usterr.h"
  11 #include <pthread.h>
  12 #include "smp.h"
  13
  14 int __num_possible_cpus;
  15
  16 void _get_num_possible_cpus(void)
  17 {
  18         int result;
  19
  20         /* On Linux, when some processors are offline
  21          * _SC_NPROCESSORS_CONF counts the offline
  22          * processors, whereas _SC_NPROCESSORS_ONLN
  23          * does not. If we used _SC_NPROCESSORS_ONLN,
  24          * getcpu() could return a value greater than
  25          * this sysconf, in which case the arrays
  26          * indexed by processor would overflow.
  27          */
  28         result = sysconf(_SC_NPROCESSORS_CONF);
  29         if (result == -1)
  30                 return;
  31         __num_possible_cpus = result;
  32 }