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

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

/*
 * We cache the result to ensure we don't trigger a system call for
 * each event.
 */
static pid_t cached_vpid;

static inline
pid_t wrapper_getvpid(void)
{
	pid_t vpid;

	vpid = CMM_LOAD_SHARED(cached_vpid);
	if (caa_unlikely(!vpid)) {
		vpid = getpid();
		CMM_STORE_SHARED(cached_vpid, vpid);
	}
	return vpid;
}

/*
 * Upon fork or clone, the PID assigned to our thread is not the same as
 * we kept in cache.
 */
void lttng_context_vpid_reset(void)
{
	CMM_STORE_SHARED(cached_vpid, 0);
}

static
size_t vpid_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
void vpid_record(struct lttng_ust_ctx_field *field,
		 struct lttng_ust_lib_ring_buffer_ctx *ctx,
		 struct lttng_ust_channel_buffer *chan)
{
	pid_t vpid = wrapper_getvpid();

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

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

int lttng_add_vpid_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, "vpid")) {
		ret = -EEXIST;
		goto error_find_context;
	}
	field->event_field->name = strdup("vpid");
	if (!field->event_field->name) {
		ret = -ENOMEM;
		goto error_name;
	}
	field->event_field->type = type;
	field->get_size = vpid_get_size;
	field->record = vpid_record;
	field->get_value = vpid_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;
}
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 vpid 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
	18	#include "context-internal.h"
	19
	20	/*
	21	* We cache the result to ensure we don't trigger a system call for
	22	* each event.
	23	*/
	24	static pid_t cached_vpid;
	25
	26	static inline
	27	pid_t wrapper_getvpid(void)
	28	{
	29	pid_t vpid;
	30
	31	vpid = CMM_LOAD_SHARED(cached_vpid);
	32	if (caa_unlikely(!vpid)) {
	33	vpid = getpid();
	34	CMM_STORE_SHARED(cached_vpid, vpid);
	35	}
	36	return vpid;
	37	}
	38
	39	/*
	40	* Upon fork or clone, the PID assigned to our thread is not the same as
	41	* we kept in cache.
	42	*/
	43	void lttng_context_vpid_reset(void)
	44	{
	45	CMM_STORE_SHARED(cached_vpid, 0);
	46	}
	47
	48	static
	49	size_t vpid_get_size(struct lttng_ust_ctx_field *field, size_t offset)
	50	{
	51	size_t size = 0;
	52
	53	size += lttng_ust_lib_ring_buffer_align(offset, lttng_ust_rb_alignof(pid_t));
	54	size += sizeof(pid_t);
	55	return size;
	56	}
	57
	58	static
	59	void vpid_record(struct lttng_ust_ctx_field *field,
	60	struct lttng_ust_lib_ring_buffer_ctx *ctx,
	61	struct lttng_ust_channel_buffer *chan)
	62	{
	63	pid_t vpid = wrapper_getvpid();
	64
	65	chan->ops->event_write(ctx, &vpid, sizeof(vpid), lttng_ust_rb_alignof(vpid));
	66	}
	67
	68	static
	69	void vpid_get_value(struct lttng_ust_ctx_field *field,
	70	struct lttng_ust_ctx_value *value)
	71	{
	72	value->u.s64 = wrapper_getvpid();
	73	}
	74
	75	int lttng_add_vpid_to_ctx(struct lttng_ust_ctx **ctx)
	76	{
	77	struct lttng_ust_ctx_field *field;
	78	struct lttng_ust_type_common *type;
	79	int ret;
	80
	81	type = lttng_ust_create_type_integer(sizeof(pid_t) * CHAR_BIT,
	82	lttng_ust_rb_alignof(pid_t) * CHAR_BIT,
	83	lttng_ust_is_signed_type(pid_t),
	84	BYTE_ORDER, 10);
	85	if (!type)
	86	return -ENOMEM;
	87	field = lttng_append_context(ctx);
	88	if (!field) {
	89	ret = -ENOMEM;
	90	goto error_context;
	91	}
	92	if (lttng_find_context(*ctx, "vpid")) {
	93	ret = -EEXIST;
	94	goto error_find_context;
	95	}
	96	field->event_field->name = strdup("vpid");
	97	if (!field->event_field->name) {
	98	ret = -ENOMEM;
	99	goto error_name;
	100	}
	101	field->event_field->type = type;
	102	field->get_size = vpid_get_size;
	103	field->record = vpid_record;
	104	field->get_value = vpid_get_value;
	105	lttng_context_update(*ctx);
	106	return 0;
	107
	108	error_name:
	109	error_find_context:
	110	lttng_remove_context_field(ctx, field);
	111	error_context:
	112	lttng_ust_destroy_type(type);
	113	return ret;
	114	}