[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>

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__

/* old uClibc versions didn't have sched_getcpu */
#if defined(__UCLIBC__) && __UCLIBC_MAJOR__ == 0 && \
	(__UCLIBC_MINOR__ < 9 || \
	 (__UCLIBC_MINOR__ == 9 && __UCLIBC_SUBLEVEL__ <= 32))
#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 c;
}
#else /* __UCLIBC__ */
#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	/* __UCLIBC__ */

#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
	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
	22	#include <urcu/compiler.h>
	23	#include <urcu/system.h>
	24	#include <urcu/arch.h>
	25
	26	void lttng_ust_getcpu_init(void);
	27
	28	extern int (*lttng_get_cpu)(void);
	29
	30	#ifdef LTTNG_UST_DEBUG_VALGRIND
	31
	32	/*
	33	* Fallback on cpu 0 if liblttng-ust is build with Valgrind support.
	34	* get_cpu() returns the current CPU number. It may change due to
	35	* migration, so it is only statistically accurate.
	36	*/
	37	static inline
	38	int lttng_ust_get_cpu_internal(void)
	39	{
	40	return 0;
	41	}
	42
	43	#else
	44
	45	/*
	46	* sched_getcpu.
	47	*/
	48	#ifdef __linux__
	49
	50	/* old uClibc versions didn't have sched_getcpu */
	51	#if defined(__UCLIBC__) && __UCLIBC_MAJOR__ == 0 && \
	52	(__UCLIBC_MINOR__ < 9 \|\| \
	53	(__UCLIBC_MINOR__ == 9 && __UCLIBC_SUBLEVEL__ <= 32))
	54	#include <sys/syscall.h>
	55	#define __getcpu(cpu, node, cache) syscall(__NR_getcpu, cpu, node, cache)
	56	/*
	57	* If getcpu is not implemented in the kernel, use cpu 0 as fallback.
	58	*/
	59	static inline
	60	int lttng_ust_get_cpu_internal(void)
	61	{
	62	int cpu, ret;
	63
	64	ret = __getcpu(&cpu, NULL, NULL);
	65	if (caa_unlikely(ret < 0))
	66	return 0;
	67	return c;
	68	}
	69	#else /* __UCLIBC__ */
	70	#include <sched.h>
	71
	72	/*
	73	* If getcpu is not implemented in the kernel, use cpu 0 as fallback.
	74	*/
	75	static inline
	76	int lttng_ust_get_cpu_internal(void)
	77	{
	78	int cpu;
	79
	80	cpu = sched_getcpu();
	81	if (caa_unlikely(cpu < 0))
	82	return 0;
	83	return cpu;
	84	}
	85	#endif /* __UCLIBC__ */
	86
	87	#elif (defined(__FreeBSD__) \|\| defined(__CYGWIN__))
	88
	89	/*
	90	* FreeBSD and Cygwin do not allow query of CPU ID. Always use CPU
	91	* number 0, with the assocated performance degradation on SMP.
	92	*/
	93	static inline
	94	int lttng_ust_get_cpu_internal(void)
	95	{
	96	return 0;
	97	}
	98
	99	#else
	100	#error "Please add support for your OS into liblttng-ust/compat.h."
	101	#endif
	102
	103	#endif
	104
	105	static inline
	106	int lttng_ust_get_cpu(void)
	107	{
	108	int (*getcpu)(void) = CMM_LOAD_SHARED(lttng_get_cpu);
	109
	110	if (caa_likely(!getcpu)) {
	111	return lttng_ust_get_cpu_internal();
	112	} else {
	113	return getcpu();
	114	}
	115	}
	116
	117	#endif /* _LTTNG_GETCPU_H */