libringbuffer/smp.c

   1 /*
   2  * libust/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 "ust/core.h"
  11 #include "usterr.h"
  12 #include <pthread.h>
  13 #include "smp.h"
  14
  15 int __num_possible_cpus;
  16
  17 void _get_num_possible_cpus(void)
  18 {
  19         int result;
  20
  21         /* On Linux, when some processors are offline
  22          * _SC_NPROCESSORS_CONF counts the offline
  23          * processors, whereas _SC_NPROCESSORS_ONLN
  24          * does not. If we used _SC_NPROCESSORS_ONLN,
  25          * getcpu() could return a value greater than
  26          * this sysconf, in which case the arrays
  27          * indexed by processor would overflow.
  28          */
  29         result = sysconf(_SC_NPROCESSORS_CONF);
  30         if (result == -1)
  31                 return;
  32         __num_possible_cpus = result;
  33 }