[lttng-ust.git] / liblttng-ust / lttng-context-vtid.c

/*
 * lttng-context-vtid.c
 *
 * LTTng UST vtid context.
 *
 * Copyright (C) 2009-2012 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
 */

#define _LGPL_SOURCE
#include <sys/types.h>
#include <unistd.h>
#include <lttng/ust-events.h>
#include <lttng/ust-tracer.h>
#include <lttng/ringbuffer-config.h>
#include <lttng/ust-tid.h>
#include <urcu/tls-compat.h>
#include "lttng-tracer-core.h"

/*
 * We cache the result to ensure we don't trigger a system call for
 * each event.
 */
static DEFINE_URCU_TLS(pid_t, cached_vtid);

/*
 * Upon fork or clone, the TID assigned to our thread is not the same as
 * we kept in cache. Luckily, we are the only thread surviving in the
 * child process, so we can simply clear our cached version.
 */
void lttng_context_vtid_reset(void)
{
	URCU_TLS(cached_vtid) = 0;
}

static
size_t vtid_get_size(struct lttng_ctx_field *field, size_t offset)
{
	size_t size = 0;

	size += lib_ring_buffer_align(offset, lttng_alignof(pid_t));
	size += sizeof(pid_t);
	return size;
}

static
void vtid_record(struct lttng_ctx_field *field,
		 struct lttng_ust_lib_ring_buffer_ctx *ctx,
		 struct lttng_channel *chan)
{
	if (caa_unlikely(!URCU_TLS(cached_vtid)))
		URCU_TLS(cached_vtid) = gettid();
	lib_ring_buffer_align_ctx(ctx, lttng_alignof(URCU_TLS(cached_vtid)));
	chan->ops->event_write(ctx, &URCU_TLS(cached_vtid),
		sizeof(URCU_TLS(cached_vtid)));
}

static
void vtid_get_value(struct lttng_ctx_field *field,
		struct lttng_ctx_value *value)
{
	if (caa_unlikely(!URCU_TLS(cached_vtid)))
		URCU_TLS(cached_vtid) = gettid();
	value->u.s64 = URCU_TLS(cached_vtid);
}

int lttng_add_vtid_to_ctx(struct lttng_ctx **ctx)
{
	struct lttng_ctx_field *field;

	field = lttng_append_context(ctx);
	if (!field)
		return -ENOMEM;
	if (lttng_find_context(*ctx, "vtid")) {
		lttng_remove_context_field(ctx, field);
		return -EEXIST;
	}
	field->event_field.name = "vtid";
	field->event_field.type.atype = atype_integer;
	field->event_field.type.u.basic.integer.size = sizeof(pid_t) * CHAR_BIT;
	field->event_field.type.u.basic.integer.alignment = lttng_alignof(pid_t) * CHAR_BIT;
	field->event_field.type.u.basic.integer.signedness = lttng_is_signed_type(pid_t);
	field->event_field.type.u.basic.integer.reverse_byte_order = 0;
	field->event_field.type.u.basic.integer.base = 10;
	field->event_field.type.u.basic.integer.encoding = lttng_encode_none;
	field->get_size = vtid_get_size;
	field->record = vtid_record;
	field->get_value = vtid_get_value;
	lttng_context_update(*ctx);
	return 0;
}

/*
 * Force a read (imply TLS fixup for dlopen) of TLS variables.
 */
void lttng_fixup_vtid_tls(void)
{
	asm volatile ("" : : "m" (URCU_TLS(cached_vtid)));
}
Commit	Line	Data
	1	/*
	2	* lttng-context-vtid.c
	3	*
	4	* LTTng UST vtid context.
	5	*
	6	* Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
	7	*
	8	* This library is free software; you can redistribute it and/or
	9	* modify it under the terms of the GNU Lesser General Public
	10	* License as published by the Free Software Foundation; only
	11	* version 2.1 of the License.
	12	*
	13	* This library is distributed in the hope that it will be useful,
	14	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	15	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	16	* Lesser General Public License for more details.
	17	*
	18	* You should have received a copy of the GNU Lesser General Public
	19	* License along with this library; if not, write to the Free Software
	20	* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
	21	*/
	22
	23	#define _LGPL_SOURCE
	24	#include <sys/types.h>
	25	#include <unistd.h>
	26	#include <lttng/ust-events.h>
	27	#include <lttng/ust-tracer.h>
	28	#include <lttng/ringbuffer-config.h>
	29	#include <lttng/ust-tid.h>
	30	#include <urcu/tls-compat.h>
	31	#include "lttng-tracer-core.h"
	32
	33	/*
	34	* We cache the result to ensure we don't trigger a system call for
	35	* each event.
	36	*/
	37	static DEFINE_URCU_TLS(pid_t, cached_vtid);
	38
	39	/*
	40	* Upon fork or clone, the TID assigned to our thread is not the same as
	41	* we kept in cache. Luckily, we are the only thread surviving in the
	42	* child process, so we can simply clear our cached version.
	43	*/
	44	void lttng_context_vtid_reset(void)
	45	{
	46	URCU_TLS(cached_vtid) = 0;
	47	}
	48
	49	static
	50	size_t vtid_get_size(struct lttng_ctx_field *field, size_t offset)
	51	{
	52	size_t size = 0;
	53
	54	size += lib_ring_buffer_align(offset, lttng_alignof(pid_t));
	55	size += sizeof(pid_t);
	56	return size;
	57	}
	58
	59	static
	60	void vtid_record(struct lttng_ctx_field *field,
	61	struct lttng_ust_lib_ring_buffer_ctx *ctx,
	62	struct lttng_channel *chan)
	63	{
	64	if (caa_unlikely(!URCU_TLS(cached_vtid)))
	65	URCU_TLS(cached_vtid) = gettid();
	66	lib_ring_buffer_align_ctx(ctx, lttng_alignof(URCU_TLS(cached_vtid)));
	67	chan->ops->event_write(ctx, &URCU_TLS(cached_vtid),
	68	sizeof(URCU_TLS(cached_vtid)));
	69	}
	70
	71	static
	72	void vtid_get_value(struct lttng_ctx_field *field,
	73	struct lttng_ctx_value *value)
	74	{
	75	if (caa_unlikely(!URCU_TLS(cached_vtid)))
	76	URCU_TLS(cached_vtid) = gettid();
	77	value->u.s64 = URCU_TLS(cached_vtid);
	78	}
	79
	80	int lttng_add_vtid_to_ctx(struct lttng_ctx **ctx)
	81	{
	82	struct lttng_ctx_field *field;
	83
	84	field = lttng_append_context(ctx);
	85	if (!field)
	86	return -ENOMEM;
	87	if (lttng_find_context(*ctx, "vtid")) {
	88	lttng_remove_context_field(ctx, field);
	89	return -EEXIST;
	90	}
	91	field->event_field.name = "vtid";
	92	field->event_field.type.atype = atype_integer;
	93	field->event_field.type.u.basic.integer.size = sizeof(pid_t) * CHAR_BIT;
	94	field->event_field.type.u.basic.integer.alignment = lttng_alignof(pid_t) * CHAR_BIT;
	95	field->event_field.type.u.basic.integer.signedness = lttng_is_signed_type(pid_t);
	96	field->event_field.type.u.basic.integer.reverse_byte_order = 0;
	97	field->event_field.type.u.basic.integer.base = 10;
	98	field->event_field.type.u.basic.integer.encoding = lttng_encode_none;
	99	field->get_size = vtid_get_size;
	100	field->record = vtid_record;
	101	field->get_value = vtid_get_value;
	102	lttng_context_update(*ctx);
	103	return 0;
	104	}
	105
	106	/*
	107	* Force a read (imply TLS fixup for dlopen) of TLS variables.
	108	*/
	109	void lttng_fixup_vtid_tls(void)
	110	{
	111	asm volatile ("" : : "m" (URCU_TLS(cached_vtid)));
	112	}