[lttng-ust.git] / src / lib / lttng-ust / 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 <lttng/ust-getcpu.h>


/*
 * Initialize the getcpu plugin if it's present.
 */
void lttng_ust_getcpu_plugin_init(void)
	__attribute__((visibility("hidden")));

/*
 * Function pointer to the user provided getcpu callback, can be set at library
 * initialization by a dlopened plugin or at runtime by a user by calling
 * lttng_ust_getcpu_override() from the public API.
 */
extern int (*lttng_ust_get_cpu_sym)(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 (*lttng_ust_get_cpu_current)(void) = CMM_LOAD_SHARED(lttng_ust_get_cpu_sym);

	/*
	 * Fallback to the internal getcpu implementation if no override was
	 * provided the user.
	 */
	if (caa_likely(!lttng_ust_get_cpu_current)) {
		return lttng_ust_get_cpu_internal();
	} else {
		return lttng_ust_get_cpu_current();
	}
}

#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 <lttng/ust-getcpu.h>
	15
	16
	17	/*
	18	* Initialize the getcpu plugin if it's present.
	19	*/
	20	void lttng_ust_getcpu_plugin_init(void)
	21	__attribute__((visibility("hidden")));
	22
	23	/*
	24	* Function pointer to the user provided getcpu callback, can be set at library
	25	* initialization by a dlopened plugin or at runtime by a user by calling
	26	* lttng_ust_getcpu_override() from the public API.
	27	*/
	28	extern int (*lttng_ust_get_cpu_sym)(void)
	29	__attribute__((visibility("hidden")));
	30
	31	#ifdef LTTNG_UST_DEBUG_VALGRIND
	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
	39	int lttng_ust_get_cpu_internal(void)
	40	{
	41	return 0;
	42	}
	43
	44	#else
	45
	46	/*
	47	* sched_getcpu.
	48	*/
	49	#ifdef __linux__
	50
	51	#if !HAVE_SCHED_GETCPU
	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
	58	int lttng_ust_get_cpu_internal(void)
	59	{
	60	int cpu, ret;
	61
	62	ret = __getcpu(&cpu, NULL, NULL);
	63	if (caa_unlikely(ret < 0))
	64	return 0;
	65	return cpu;
	66	}
	67	#else /* HAVE_SCHED_GETCPU */
	68	#include <sched.h>
	69
	70	/*
	71	* If getcpu is not implemented in the kernel, use cpu 0 as fallback.
	72	*/
	73	static inline
	74	int lttng_ust_get_cpu_internal(void)
	75	{
	76	int cpu;
	77
	78	cpu = sched_getcpu();
	79	if (caa_unlikely(cpu < 0))
	80	return 0;
	81	return cpu;
	82	}
	83	#endif /* HAVE_SCHED_GETCPU */
	84
	85	#elif (defined(__FreeBSD__) \|\| defined(__CYGWIN__))
	86
	87	/*
	88	* FreeBSD and Cygwin do not allow query of CPU ID. Always use CPU
	89	* number 0, with the assocated performance degradation on SMP.
	90	*/
	91	static inline
	92	int lttng_ust_get_cpu_internal(void)
	93	{
	94	return 0;
	95	}
	96
	97	#else
	98	#error "Please add support for your OS into liblttng-ust/compat.h."
	99	#endif
	100
	101	#endif
	102
	103	static inline
	104	int lttng_ust_get_cpu(void)
	105	{
	106	int (*lttng_ust_get_cpu_current)(void) = CMM_LOAD_SHARED(lttng_ust_get_cpu_sym);
	107
	108	/*
	109	* Fallback to the internal getcpu implementation if no override was
	110	* provided the user.
	111	*/
	112	if (caa_likely(!lttng_ust_get_cpu_current)) {
	113	return lttng_ust_get_cpu_internal();
	114	} else {
	115	return lttng_ust_get_cpu_current();
	116	}
	117	}
	118
	119	#endif /* _LTTNG_GETCPU_H */