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

/*
 * SPDX-License-Identifier: LGPL-2.1-only
 *
 * Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
 *
 * LTTng UST vtid context.
 */

#define _LGPL_SOURCE
#include <limits.h>
#include <stddef.h>
#include <sys/types.h>
#include <unistd.h>
#include <lttng/ust-events.h>
#include <lttng/ust-tracer.h>
#include <lttng/ringbuffer-context.h>
#include <ust-tid.h>
#include <urcu/tls-compat.h>

#include "context-internal.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)
{
	CMM_STORE_SHARED(URCU_TLS(cached_vtid), 0);
}

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

	size += lttng_ust_lib_ring_buffer_align(offset, lttng_ust_rb_alignof(pid_t));
	size += sizeof(pid_t);
	return size;
}

static inline
pid_t wrapper_getvtid(void)
{
	pid_t vtid;

	vtid = CMM_LOAD_SHARED(URCU_TLS(cached_vtid));
	if (caa_unlikely(!vtid)) {
		vtid = lttng_gettid();
		CMM_STORE_SHARED(URCU_TLS(cached_vtid), vtid);
	}
	return vtid;
}

static
void vtid_record(struct lttng_ust_ctx_field *field,
		 struct lttng_ust_lib_ring_buffer_ctx *ctx,
		 struct lttng_ust_channel_buffer *chan)
{
	pid_t vtid = wrapper_getvtid();

	chan->ops->event_write(ctx, &vtid, sizeof(vtid), lttng_ust_rb_alignof(vtid));
}

static
void vtid_get_value(struct lttng_ust_ctx_field *field,
		struct lttng_ust_ctx_value *value)
{
	value->u.s64 = wrapper_getvtid();
}

int lttng_add_vtid_to_ctx(struct lttng_ust_ctx **ctx)
{
	struct lttng_ust_ctx_field *field;
	struct lttng_ust_type_common *type;
	int ret;

	type = lttng_ust_create_type_integer(sizeof(pid_t) * CHAR_BIT,
			lttng_ust_rb_alignof(pid_t) * CHAR_BIT,
			lttng_ust_is_signed_type(pid_t),
			BYTE_ORDER, 10);
	if (!type)
		return -ENOMEM;
	field = lttng_append_context(ctx);
	if (!field) {
		ret = -ENOMEM;
		goto error_context;
	}
	if (lttng_find_context(*ctx, "vtid")) {
		ret = -EEXIST;
		goto error_find_context;
	}
	field->event_field->name = strdup("vtid");
	if (!field->event_field->name) {
		ret = -ENOMEM;
		goto error_name;
	}
	field->event_field->type = type;
	field->get_size = vtid_get_size;
	field->record = vtid_record;
	field->get_value = vtid_get_value;
	lttng_context_update(*ctx);
	return 0;

error_name:
error_find_context:
	lttng_remove_context_field(ctx, field);
error_context:
	lttng_ust_destroy_type(type);
	return ret;
}

/*
 * 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	* SPDX-License-Identifier: LGPL-2.1-only
	3	*
	4	* Copyright (C) 2009-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
	5	*
	6	* LTTng UST vtid context.
	7	*/
	8
	9	#define _LGPL_SOURCE
	10	#include <limits.h>
	11	#include <stddef.h>
	12	#include <sys/types.h>
	13	#include <unistd.h>
	14	#include <lttng/ust-events.h>
	15	#include <lttng/ust-tracer.h>
	16	#include <lttng/ringbuffer-context.h>
	17	#include <ust-tid.h>
	18	#include <urcu/tls-compat.h>
	19
	20	#include "context-internal.h"
	21	#include "lttng-tracer-core.h"
	22
	23	/*
	24	* We cache the result to ensure we don't trigger a system call for
	25	* each event.
	26	*/
	27	static DEFINE_URCU_TLS(pid_t, cached_vtid);
	28
	29	/*
	30	* Upon fork or clone, the TID assigned to our thread is not the same as
	31	* we kept in cache. Luckily, we are the only thread surviving in the
	32	* child process, so we can simply clear our cached version.
	33	*/
	34	void lttng_context_vtid_reset(void)
	35	{
	36	CMM_STORE_SHARED(URCU_TLS(cached_vtid), 0);
	37	}
	38
	39	static
	40	size_t vtid_get_size(struct lttng_ust_ctx_field *field, size_t offset)
	41	{
	42	size_t size = 0;
	43
	44	size += lttng_ust_lib_ring_buffer_align(offset, lttng_ust_rb_alignof(pid_t));
	45	size += sizeof(pid_t);
	46	return size;
	47	}
	48
	49	static inline
	50	pid_t wrapper_getvtid(void)
	51	{
	52	pid_t vtid;
	53
	54	vtid = CMM_LOAD_SHARED(URCU_TLS(cached_vtid));
	55	if (caa_unlikely(!vtid)) {
	56	vtid = lttng_gettid();
	57	CMM_STORE_SHARED(URCU_TLS(cached_vtid), vtid);
	58	}
	59	return vtid;
	60	}
	61
	62	static
	63	void vtid_record(struct lttng_ust_ctx_field *field,
	64	struct lttng_ust_lib_ring_buffer_ctx *ctx,
	65	struct lttng_ust_channel_buffer *chan)
	66	{
	67	pid_t vtid = wrapper_getvtid();
	68
	69	chan->ops->event_write(ctx, &vtid, sizeof(vtid), lttng_ust_rb_alignof(vtid));
	70	}
	71
	72	static
	73	void vtid_get_value(struct lttng_ust_ctx_field *field,
	74	struct lttng_ust_ctx_value *value)
	75	{
	76	value->u.s64 = wrapper_getvtid();
	77	}
	78
	79	int lttng_add_vtid_to_ctx(struct lttng_ust_ctx **ctx)
	80	{
	81	struct lttng_ust_ctx_field *field;
	82	struct lttng_ust_type_common *type;
	83	int ret;
	84
	85	type = lttng_ust_create_type_integer(sizeof(pid_t) * CHAR_BIT,
	86	lttng_ust_rb_alignof(pid_t) * CHAR_BIT,
	87	lttng_ust_is_signed_type(pid_t),
	88	BYTE_ORDER, 10);
	89	if (!type)
	90	return -ENOMEM;
	91	field = lttng_append_context(ctx);
	92	if (!field) {
	93	ret = -ENOMEM;
	94	goto error_context;
	95	}
	96	if (lttng_find_context(*ctx, "vtid")) {
	97	ret = -EEXIST;
	98	goto error_find_context;
	99	}
	100	field->event_field->name = strdup("vtid");
	101	if (!field->event_field->name) {
	102	ret = -ENOMEM;
	103	goto error_name;
	104	}
	105	field->event_field->type = type;
	106	field->get_size = vtid_get_size;
	107	field->record = vtid_record;
	108	field->get_value = vtid_get_value;
	109	lttng_context_update(*ctx);
	110	return 0;
	111
	112	error_name:
	113	error_find_context:
	114	lttng_remove_context_field(ctx, field);
	115	error_context:
	116	lttng_ust_destroy_type(type);
	117	return ret;
	118	}
	119
	120	/*
	121	* Force a read (imply TLS fixup for dlopen) of TLS variables.
	122	*/
	123	void lttng_fixup_vtid_tls(void)
	124	{
	125	asm volatile ("" : : "m" (URCU_TLS(cached_vtid)));
	126	}