[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>

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