[lttng-ust.git] / libringbuffer / getcpu.h

#ifndef _LTTNG_GETCPU_H
#define _LTTNG_GETCPU_H

/*
 * Copyright (c) 2011 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; only
 * version 2.1 of the License.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include <urcu/compiler.h>
#include <urcu/system.h>
#include <urcu/arch.h>
#include <config.h>

void lttng_ust_getcpu_init(void);

extern int (*lttng_get_cpu)(void);

#ifdef LTTNG_UST_DEBUG_VALGRIND

/*
 * Fallback on cpu 0 if liblttng-ust is build with Valgrind support.
 * get_cpu() returns the current CPU number. It may change due to
 * migration, so it is only statistically accurate.
 */
static inline
int lttng_ust_get_cpu_internal(void)
{
	return 0;
}

#else

/*
 * sched_getcpu.
 */
#ifdef __linux__

#if !HAVE_SCHED_GETCPU
#include <sys/syscall.h>
#define __getcpu(cpu, node, cache)	syscall(__NR_getcpu, cpu, node, cache)
/*
 * If getcpu is not implemented in the kernel, use cpu 0 as fallback.
 */
static inline
int lttng_ust_get_cpu_internal(void)
{
	int cpu, ret;

	ret = __getcpu(&cpu, NULL, NULL);
	if (caa_unlikely(ret < 0))
		return 0;
	return cpu;
}
#else /* HAVE_SCHED_GETCPU */
#include <sched.h>

/*
 * If getcpu is not implemented in the kernel, use cpu 0 as fallback.
 */
static inline
int lttng_ust_get_cpu_internal(void)
{
	int cpu;

	cpu = sched_getcpu();
	if (caa_unlikely(cpu < 0))
		return 0;
	return cpu;
}
#endif	/* HAVE_SCHED_GETCPU */

#elif (defined(__FreeBSD__) || defined(__CYGWIN__))

/*
 * FreeBSD and Cygwin do not allow query of CPU ID. Always use CPU
 * number 0, with the assocated performance degradation on SMP.
 */
static inline
int lttng_ust_get_cpu_internal(void)
{
	return 0;
}

#else
#error "Please add support for your OS into liblttng-ust/compat.h."
#endif

#endif

static inline
int lttng_ust_get_cpu(void)
{
	int (*getcpu)(void) = CMM_LOAD_SHARED(lttng_get_cpu);

	if (caa_likely(!getcpu)) {
		return lttng_ust_get_cpu_internal();
	} else {
		return getcpu();
	}
}

#endif /* _LTTNG_GETCPU_H */
Commit	Line	Data
2b2d6ff7 MD	1	#ifndef _LTTNG_GETCPU_H
	2	#define _LTTNG_GETCPU_H
	3
	4	/*
	5	* Copyright (c) 2011 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
	6	*
	7	* This library is free software; you can redistribute it and/or
	8	* modify it under the terms of the GNU Lesser General Public
	9	* License as published by the Free Software Foundation; only
	10	* version 2.1 of the License.
	11	*
	12	* This library is distributed in the hope that it will be useful,
	13	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	14	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	15	* Lesser General Public License for more details.
	16	*
	17	* You should have received a copy of the GNU Lesser General Public
	18	* License along with this library; if not, write to the Free Software
	19	* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
	20	*/
	21
2b2d6ff7	22	#include <urcu/compiler.h>
5e1b7b8b MD	23	#include <urcu/system.h>
5e1b7b8b MD	24	#include <urcu/arch.h>
787364e8	25	#include <config.h>
5e1b7b8b MD	26
	27	void lttng_ust_getcpu_init(void);
	28
	29	extern int (*lttng_get_cpu)(void);
2b2d6ff7	30
fdb4af10	31	#ifdef LTTNG_UST_DEBUG_VALGRIND
2b2d6ff7 MD	32
	33	/*
	34	* Fallback on cpu 0 if liblttng-ust is build with Valgrind support.
	35	* get_cpu() returns the current CPU number. It may change due to
	36	* migration, so it is only statistically accurate.
	37	*/
	38	static inline
5e1b7b8b	39	int lttng_ust_get_cpu_internal(void)
2b2d6ff7 MD	40	{
	41	return 0;
	42	}
	43
	44	#else
	45
08bf1cc1 MD	46	/*
	47	* sched_getcpu.
	48	*/
	49	#ifdef __linux__
	50
787364e8	51	#if !HAVE_SCHED_GETCPU
08bf1cc1 MD	52	#include <sys/syscall.h>
	53	#define __getcpu(cpu, node, cache) syscall(__NR_getcpu, cpu, node, cache)
	54	/*
	55	* If getcpu is not implemented in the kernel, use cpu 0 as fallback.
	56	*/
	57	static inline
5e1b7b8b	58	int lttng_ust_get_cpu_internal(void)
08bf1cc1 MD	59	{
	60	int cpu, ret;
	61
	62	ret = __getcpu(&cpu, NULL, NULL);
	63	if (caa_unlikely(ret < 0))
	64	return 0;
787364e8	65	return cpu;
08bf1cc1	66	}
787364e8	67	#else /* HAVE_SCHED_GETCPU */
08bf1cc1 MD	68	#include <sched.h>
08bf1cc1 MD	69
2b2d6ff7 MD	70	/*
	71	* If getcpu is not implemented in the kernel, use cpu 0 as fallback.
	72	*/
	73	static inline
5e1b7b8b	74	int lttng_ust_get_cpu_internal(void)
2b2d6ff7 MD	75	{
	76	int cpu;
	77
	78	cpu = sched_getcpu();
	79	if (caa_unlikely(cpu < 0))
	80	return 0;
	81	return cpu;
	82	}
787364e8	83	#endif /* HAVE_SCHED_GETCPU */
08bf1cc1	84
4327cb7d	85	#elif (defined(__FreeBSD__) \|\| defined(__CYGWIN__))
08bf1cc1 MD	86
08bf1cc1 MD	87	/*
4327cb7d MD	88	* FreeBSD and Cygwin do not allow query of CPU ID. Always use CPU
4327cb7d MD	89	* number 0, with the assocated performance degradation on SMP.
08bf1cc1 MD	90	*/
08bf1cc1 MD	91	static inline
5e1b7b8b	92	int lttng_ust_get_cpu_internal(void)
08bf1cc1 MD	93	{
	94	return 0;
	95	}
	96
	97	#else
	98	#error "Please add support for your OS into liblttng-ust/compat.h."
	99	#endif
2b2d6ff7 MD	100
	101	#endif
	102
5e1b7b8b MD	103	static inline
	104	int lttng_ust_get_cpu(void)
	105	{
	106	int (*getcpu)(void) = CMM_LOAD_SHARED(lttng_get_cpu);
	107
	108	if (caa_likely(!getcpu)) {
	109	return lttng_ust_get_cpu_internal();
	110	} else {
	111	return getcpu();
	112	}
	113	}
	114
2b2d6ff7	115	#endif /* _LTTNG_GETCPU_H */