[lttng-ust.git] / libringbuffer / smp.c

/*
 * libringbuffer/smp.c
 *
 * Copyright 2011 (c) - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
 *
 * Dual LGPL v2.1/GPL v2 license.
 */

#include <unistd.h>
#include "usterr.h"
#include <pthread.h>
#include "smp.h"

int __num_possible_cpus;

void _get_num_possible_cpus(void)
{
	int result;

	/* On Linux, when some processors are offline
	 * _SC_NPROCESSORS_CONF counts the offline
	 * processors, whereas _SC_NPROCESSORS_ONLN
	 * does not. If we used _SC_NPROCESSORS_ONLN,
	 * getcpu() could return a value greater than
	 * this sysconf, in which case the arrays
	 * indexed by processor would overflow.
	 */
	result = sysconf(_SC_NPROCESSORS_CONF);
	if (result == -1)
		return;
	__num_possible_cpus = result;
}
Commit	Line	Data
a6352fd4	1	/*
4318ae1b	2	* libringbuffer/smp.c
a6352fd4 MD	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>
a6352fd4 MD	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	}