[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 <stddef.h>
#include <sys/types.h>
#include <unistd.h>
#include <lttng/ust-events.h>
#include <lttng/ust-tracer.h>
#include <lttng/ringbuffer-config.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 += lib_ring_buffer_align(offset, lttng_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_channel *chan)
{
	pid_t vtid = wrapper_getvtid();

	lib_ring_buffer_align_ctx(ctx, lttng_alignof(vtid));
	chan->ops->event_write(ctx, &vtid, sizeof(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;

	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.integer.size = sizeof(pid_t) * CHAR_BIT;
	field->event_field->type.u.integer.alignment = lttng_alignof(pid_t) * CHAR_BIT;
	field->event_field->type.u.integer.signedness = lttng_is_signed_type(pid_t);
	field->event_field->type.u.integer.reverse_byte_order = 0;
	field->event_field->type.u.integer.base = 10;
	field->event_field->type.u.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	* 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 <stddef.h>
	11	#include <sys/types.h>
	12	#include <unistd.h>
	13	#include <lttng/ust-events.h>
	14	#include <lttng/ust-tracer.h>
	15	#include <lttng/ringbuffer-config.h>
	16	#include <ust-tid.h>
	17	#include <urcu/tls-compat.h>
	18
	19	#include "context-internal.h"
	20	#include "lttng-tracer-core.h"
	21
	22	/*
	23	* We cache the result to ensure we don't trigger a system call for
	24	* each event.
	25	*/
	26	static DEFINE_URCU_TLS(pid_t, cached_vtid);
	27
	28	/*
	29	* Upon fork or clone, the TID assigned to our thread is not the same as
	30	* we kept in cache. Luckily, we are the only thread surviving in the
	31	* child process, so we can simply clear our cached version.
	32	*/
	33	void lttng_context_vtid_reset(void)
	34	{
	35	CMM_STORE_SHARED(URCU_TLS(cached_vtid), 0);
	36	}
	37
	38	static
	39	size_t vtid_get_size(struct lttng_ust_ctx_field *field, size_t offset)
	40	{
	41	size_t size = 0;
	42
	43	size += lib_ring_buffer_align(offset, lttng_alignof(pid_t));
	44	size += sizeof(pid_t);
	45	return size;
	46	}
	47
	48	static inline
	49	pid_t wrapper_getvtid(void)
	50	{
	51	pid_t vtid;
	52
	53	vtid = CMM_LOAD_SHARED(URCU_TLS(cached_vtid));
	54	if (caa_unlikely(!vtid)) {
	55	vtid = lttng_gettid();
	56	CMM_STORE_SHARED(URCU_TLS(cached_vtid), vtid);
	57	}
	58	return vtid;
	59	}
	60
	61	static
	62	void vtid_record(struct lttng_ust_ctx_field *field,
	63	struct lttng_ust_lib_ring_buffer_ctx *ctx,
	64	struct lttng_channel *chan)
	65	{
	66	pid_t vtid = wrapper_getvtid();
	67
	68	lib_ring_buffer_align_ctx(ctx, lttng_alignof(vtid));
	69	chan->ops->event_write(ctx, &vtid, sizeof(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
	83	field = lttng_append_context(ctx);
	84	if (!field)
	85	return -ENOMEM;
	86	if (lttng_find_context(*ctx, "vtid")) {
	87	lttng_remove_context_field(ctx, field);
	88	return -EEXIST;
	89	}
	90	field->event_field->name = "vtid";
	91	field->event_field->type.atype = atype_integer;
	92	field->event_field->type.u.integer.size = sizeof(pid_t) * CHAR_BIT;
	93	field->event_field->type.u.integer.alignment = lttng_alignof(pid_t) * CHAR_BIT;
	94	field->event_field->type.u.integer.signedness = lttng_is_signed_type(pid_t);
	95	field->event_field->type.u.integer.reverse_byte_order = 0;
	96	field->event_field->type.u.integer.base = 10;
	97	field->event_field->type.u.integer.encoding = lttng_encode_none;
	98	field->get_size = vtid_get_size;
	99	field->record = vtid_record;
	100	field->get_value = vtid_get_value;
	101	lttng_context_update(*ctx);
	102	return 0;
	103	}
	104
	105	/*
	106	* Force a read (imply TLS fixup for dlopen) of TLS variables.
	107	*/
	108	void lttng_fixup_vtid_tls(void)
	109	{
	110	asm volatile ("" : : "m" (URCU_TLS(cached_vtid)));
	111	}