#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>

#include <config.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 */