[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)
	__attribute__((visibility("hidden")));

extern int (*lttng_get_cpu)(void)
	__attribute__((visibility("hidden")));

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