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

/*
 * SPDX-License-Identifier: LGPL-2.1-only
 *
 * Copyright (C) 2011 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
 */

#ifndef _LTTNG_GETCPU_H
#define _LTTNG_GETCPU_H

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

#include "ust-helper.h"

LTTNG_HIDDEN
void lttng_ust_getcpu_init(void);

LTTNG_HIDDEN
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
	1	/*
	2	* SPDX-License-Identifier: LGPL-2.1-only
	3	*
	4	* Copyright (C) 2011 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
	5	*/
	6
	7	#ifndef _LTTNG_GETCPU_H
	8	#define _LTTNG_GETCPU_H
	9
	10	#include <urcu/compiler.h>
	11	#include <urcu/system.h>
	12	#include <urcu/arch.h>
	13
	14	#include "ust-helper.h"
	15
	16	LTTNG_HIDDEN
	17	void lttng_ust_getcpu_init(void);
	18
	19	LTTNG_HIDDEN
	20	extern int (*lttng_get_cpu)(void);
	21
	22	#ifdef LTTNG_UST_DEBUG_VALGRIND
	23
	24	/*
	25	* Fallback on cpu 0 if liblttng-ust is build with Valgrind support.
	26	* get_cpu() returns the current CPU number. It may change due to
	27	* migration, so it is only statistically accurate.
	28	*/
	29	static inline
	30	int lttng_ust_get_cpu_internal(void)
	31	{
	32	return 0;
	33	}
	34
	35	#else
	36
	37	/*
	38	* sched_getcpu.
	39	*/
	40	#ifdef __linux__
	41
	42	#if !HAVE_SCHED_GETCPU
	43	#include <sys/syscall.h>
	44	#define __getcpu(cpu, node, cache) syscall(__NR_getcpu, cpu, node, cache)
	45	/*
	46	* If getcpu is not implemented in the kernel, use cpu 0 as fallback.
	47	*/
	48	static inline
	49	int lttng_ust_get_cpu_internal(void)
	50	{
	51	int cpu, ret;
	52
	53	ret = __getcpu(&cpu, NULL, NULL);
	54	if (caa_unlikely(ret < 0))
	55	return 0;
	56	return cpu;
	57	}
	58	#else /* HAVE_SCHED_GETCPU */
	59	#include <sched.h>
	60
	61	/*
	62	* If getcpu is not implemented in the kernel, use cpu 0 as fallback.
	63	*/
	64	static inline
	65	int lttng_ust_get_cpu_internal(void)
	66	{
	67	int cpu;
	68
	69	cpu = sched_getcpu();
	70	if (caa_unlikely(cpu < 0))
	71	return 0;
	72	return cpu;
	73	}
	74	#endif /* HAVE_SCHED_GETCPU */
	75
	76	#elif (defined(__FreeBSD__) \|\| defined(__CYGWIN__))
	77
	78	/*
	79	* FreeBSD and Cygwin do not allow query of CPU ID. Always use CPU
	80	* number 0, with the assocated performance degradation on SMP.
	81	*/
	82	static inline
	83	int lttng_ust_get_cpu_internal(void)
	84	{
	85	return 0;
	86	}
	87
	88	#else
	89	#error "Please add support for your OS into liblttng-ust/compat.h."
	90	#endif
	91
	92	#endif
	93
	94	static inline
	95	int lttng_ust_get_cpu(void)
	96	{
	97	int (*getcpu)(void) = CMM_LOAD_SHARED(lttng_get_cpu);
	98
	99	if (caa_likely(!getcpu)) {
	100	return lttng_ust_get_cpu_internal();
	101	} else {
	102	return getcpu();
	103	}
	104	}
	105
	106	#endif /* _LTTNG_GETCPU_H */