From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Wed, 30 Nov 2011 22:55:25 +0000 (-0500)
Subject: Tracepoint loglevel: setup all loglevel information at build time
X-Git-Tag: v1.9.1~44
X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=df854e41ded4203a5b86bac062b8604bb038759a;p=lttng-ust.git

Tracepoint loglevel: setup all loglevel information at build time

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
---

diff --git a/include/lttng/tracepoint.h b/include/lttng/tracepoint.h
index 709fadc1..929a863f 100644
--- a/include/lttng/tracepoint.h
+++ b/include/lttng/tracepoint.h
@@ -37,8 +37,18 @@ extern "C" {
  * fine too).
  * Each tuple is also separated by a comma.
  */
-#define _TP_COMBINE_TOKENS1(_tokena, _tokenb)       _tokena##_tokenb
-#define _TP_COMBINE_TOKENS(_tokena, _tokenb)        _TP_COMBINE_TOKENS1(_tokena, _tokenb)
+#define __TP_COMBINE_TOKENS(_tokena, _tokenb)				\
+		_tokena##_tokenb
+#define _TP_COMBINE_TOKENS(_tokena, _tokenb)				\
+		__TP_COMBINE_TOKENS(_tokena, _tokenb)
+#define __TP_COMBINE_TOKENS3(_tokena, _tokenb, _tokenc)			\
+		_tokena##_tokenb##_tokenc
+#define _TP_COMBINE_TOKENS3(_tokena, _tokenb, _tokenc)			\
+		__TP_COMBINE_TOKENS3(_tokena, _tokenb, _tokenc)
+#define __TP_COMBINE_TOKENS4(_tokena, _tokenb, _tokenc, _tokend)	\
+		_tokena##_tokenb##_tokenc##_tokend
+#define _TP_COMBINE_TOKENS4(_tokena, _tokenb, _tokenc, _tokend)		\
+		__TP_COMBINE_TOKENS4(_tokena, _tokenb, _tokenc, _tokend)
 
 /* _TP_EXVAR* extract the var names. */
 #define _TP_EXVAR0()
diff --git a/include/lttng/ust-abi.h b/include/lttng/ust-abi.h
index 5e4bf49e..ae95af6b 100644
--- a/include/lttng/ust-abi.h
+++ b/include/lttng/ust-abi.h
@@ -26,9 +26,10 @@
 #define LTTNG_UST_COMM_VERSION_MINOR		1
 
 enum lttng_ust_instrumentation {
-	LTTNG_UST_TRACEPOINT	= 0,
-	LTTNG_UST_PROBE		= 1,
-	LTTNG_UST_FUNCTION	= 2,
+	LTTNG_UST_TRACEPOINT		= 0,
+	LTTNG_UST_PROBE			= 1,
+	LTTNG_UST_FUNCTION		= 2,
+	LTTNG_UST_TRACEPOINT_LOGLEVEL	= 3,
 };
 
 enum lttng_ust_output {
@@ -97,6 +98,12 @@ struct lttng_ust_channel_attr {
 	enum lttng_ust_output output;		/* splice, mmap */
 };
 
+struct lttng_ust_loglevel {
+	char provider[LTTNG_UST_SYM_NAME_LEN];
+	char loglevel[LTTNG_UST_SYM_NAME_LEN];
+	int64_t value;
+};
+
 struct lttng_ust_object_data {
 	int handle;
 	int shm_fd;
@@ -120,6 +127,7 @@ struct lttng_ust_object_data {
 #define LTTNG_UST_TRACEPOINT_LIST		_UST_CMD(0x42)
 #define LTTNG_UST_WAIT_QUIESCENT		_UST_CMD(0x43)
 #define LTTNG_UST_REGISTER_DONE			_UST_CMD(0x44)
+#define LTTNG_UST_LOGLEVEL_LIST			_UST_CMD(0x45)
 
 /* Session FD commands */
 #define LTTNG_UST_METADATA			\
@@ -147,6 +155,9 @@ struct lttng_ust_object_data {
 /* Tracepoint list commands */
 #define LTTNG_UST_TRACEPOINT_LIST_GET		_UST_CMD(0x90)
 
+/* Loglevel list commands */
+#define LTTNG_UST_LOGLEVEL_LIST_GET		_UST_CMD(0xA0)
+
 #define LTTNG_UST_ROOT_HANDLE	0
 
 struct lttng_ust_obj;
diff --git a/include/lttng/ust-events.h b/include/lttng/ust-events.h
index 0ccef46a..6b4863fd 100644
--- a/include/lttng/ust-events.h
+++ b/include/lttng/ust-events.h
@@ -183,19 +183,32 @@ struct lttng_ctx {
 	unsigned int allocated_fields;
 };
 
+struct tracepoint_loglevel_entry  {
+	const char *identifier;
+	long value;
+};
+
 struct lttng_event_desc {
 	const char *name;
 	void *probe_callback;
 	const struct lttng_event_ctx *ctx;	/* context */
 	const struct lttng_event_field *fields;	/* event payload */
 	unsigned int nr_fields;
+	const struct tracepoint_loglevel_entry **loglevel;
 };
 
 struct lttng_probe_desc {
-	const struct lttng_event_desc *event_desc;
+	const char *provider;
+	const struct lttng_event_desc **event_desc;
 	unsigned int nr_events;
+	const struct tracepoint_loglevel_entry **loglevels;
+	unsigned int nr_loglevels;
 	struct cds_list_head head;		/* chain registered probes */
-	struct tracepoint_loglevel *loglevels;
+};
+
+struct tp_loglevel_iter {
+	struct lttng_probe_desc *desc;
+	const struct tracepoint_loglevel_entry *loglevel;
 };
 
 struct ust_pending_probe;
@@ -303,17 +316,6 @@ struct ltt_transport {
 	struct ltt_channel_ops ops;
 };
 
-struct tracepoint_loglevel_enum_entry  {
-	const char *identifier;
-	long value;
-};
-
-/* mapping between tracepoint and loglevel */
-struct tracepoint_loglevel {
-	const char *name;
-	const struct tracepoint_loglevel_enum_entry *loglevel;
-};
-
 struct ltt_session *ltt_session_create(void);
 int ltt_session_enable(struct ltt_session *session);
 int ltt_session_disable(struct ltt_session *session);
diff --git a/include/lttng/ust-tracepoint-event.h b/include/lttng/ust-tracepoint-event.h
index 685ef5d1..5066b4b6 100644
--- a/include/lttng/ust-tracepoint-event.h
+++ b/include/lttng/ust-tracepoint-event.h
@@ -215,29 +215,6 @@ static void __event_probe__##_provider##___##_name(_TP_ARGS_DATA_PROTO(_args));
 /*
  * Stage 3 of tracepoint event generation.
  *
- * Create an array of events.
- */
-
-/* Reset all macros within TRACEPOINT_EVENT */
-#include <lttng/ust-tracepoint-event-reset.h>
-
-#undef TRACEPOINT_EVENT_INSTANCE
-#define TRACEPOINT_EVENT_INSTANCE(_provider, _template, _name, _args)	       \
-		{							       \
-			.fields = __event_fields___##_provider##___##_template,\
-			.name = #_provider ":" #_name,			       \
-			.probe_callback = (void *) &__event_probe__##_provider##___##_template,\
-			.nr_fields = _TP_ARRAY_SIZE(__event_fields___##_provider##___##_template), \
-		},
-
-static const struct lttng_event_desc _TP_COMBINE_TOKENS(__event_desc___, TRACEPOINT_PROVIDER)[] = {
-#include TRACEPOINT_INCLUDE
-};
-
-
-/*
- * Stage 4 of tracepoint event generation.
- *
  * Create static inline function that calculates event size.
  */
 
@@ -295,7 +272,7 @@ static inline size_t __event_get_size__##_provider##___##_name(size_t *__dynamic
 #include TRACEPOINT_INCLUDE
 
 /*
- * Stage 5 of tracepoint event generation.
+ * Stage 4 of tracepoint event generation.
  *
  * Create static inline function that calculates event payload alignment.
  */
@@ -344,7 +321,7 @@ size_t __event_get_align__##_provider##___##_name(_TP_ARGS_PROTO(_args))      \
 
 
 /*
- * Stage 6 of tracepoint event generation.
+ * Stage 5 of tracepoint event generation.
  *
  * Create the probe function. This function calls event size calculation
  * and writes event data into the buffer.
@@ -438,7 +415,7 @@ static void __event_probe__##_provider##___##_name(_TP_ARGS_DATA_PROTO(_args))\
 #undef __get_dynamic_len
 
 /*
- * Stage 7.1 of tracepoint event generation.
+ * Stage 6.1 of tracepoint event generation.
  *
  * Tracepoint loglevel enumeration definition generation.
  */
@@ -451,9 +428,8 @@ static void __event_probe__##_provider##___##_name(_TP_ARGS_DATA_PROTO(_args))\
 
 #undef tp_loglevel
 #define tp_loglevel(_identifier, _value)		\
-static const struct tracepoint_loglevel_enum_entry	\
-	_TP_COMBINE_TOKENS(_TP_COMBINE_TOKENS(TRACEPOINT_PROVIDER, __tp_loglevel_enum_entry__), _identifier) =	\
-	{						\
+static const struct tracepoint_loglevel_entry		\
+	_TP_COMBINE_TOKENS4(__tp_loglevel_entry__, TRACEPOINT_PROVIDER, ___, _identifier) = {	\
 		.identifier = #_identifier,		\
 		.value = (_value),			\
 	};
@@ -461,7 +437,7 @@ static const struct tracepoint_loglevel_enum_entry	\
 #include TRACEPOINT_INCLUDE
 
 /*
- * Stage 7.2 of tracepoint event generation.
+ * Stage 6.2 of tracepoint event generation.
  *
  * Tracepoint loglevel enumeration array generation.
  */
@@ -474,33 +450,76 @@ static const struct tracepoint_loglevel_enum_entry	\
 
 #undef tp_loglevel
 #define tp_loglevel(_identifier, _value)		\
-	&_TP_COMBINE_TOKENS(_TP_COMBINE_TOKENS(TRACEPOINT_PROVIDER, __tp_loglevel_enum_entry__), _identifier),
+	&_TP_COMBINE_TOKENS4(__tp_loglevel_entry__, TRACEPOINT_PROVIDER, ___, _identifier),	\
 
-static const struct tracepoint_loglevel_enum_entry *_TP_COMBINE_TOKENS(__tracepoint_loglevel_enum__, TRACEPOINT_PROVIDER)[] __attribute__((unused)) =
-{
+static const struct tracepoint_loglevel_entry *_TP_COMBINE_TOKENS(__tracepoint_loglevel_enum__, TRACEPOINT_PROVIDER)[] = {
 #include TRACEPOINT_INCLUDE
 };
 
 /*
- * Stage 8 of tracepoint event generation.
+ * Stage 7 of tracepoint event generation.
  *
- * Tracepoint loglevel definition generation.
+ * Tracepoint loglevel mapping definition generation. We generate a
+ * symbol for each mapping for a provider/event to ensure at most a 1 to
+ * 1 mapping between events and loglevels. If the symbol is repeated,
+ * the compiler will complain.
  */
 
 /* Reset all macros within TRACEPOINT_EVENT */
 #include <lttng/ust-tracepoint-event-reset.h>
 
 #undef TRACEPOINT_LOGLEVEL
-#define TRACEPOINT_LOGLEVEL(__provider, __name, __loglevel)	\
-{								\
-	.name = #__provider ":" #__name,			\
-	.loglevel = &_TP_COMBINE_TOKENS(_TP_COMBINE_TOKENS(TRACEPOINT_PROVIDER, __tp_loglevel_enum_entry__), __loglevel), \
-},
+#define TRACEPOINT_LOGLEVEL(__provider, __name, __loglevel)		\
+static const struct tracepoint_loglevel_entry *				\
+	_loglevel_mapping___##__provider##___##__name =			\
+		&__tp_loglevel_entry__##__provider##___##__loglevel;
+
+#include TRACEPOINT_INCLUDE
+
+/*
+ * Stage 8.1 of tracepoint event generation.
+ *
+ * Create events description structures. We use a weakref because
+ * loglevels are optional. If not declared, the event will point to the
+ * a loglevel that contains NULL.
+ */
+
+/* Reset all macros within TRACEPOINT_EVENT */
+#include <lttng/ust-tracepoint-event-reset.h>
+
+#undef TRACEPOINT_EVENT_INSTANCE
+#define TRACEPOINT_EVENT_INSTANCE(_provider, _template, _name, _args)	       \
+static const struct tracepoint_loglevel_entry *				       \
+	__ref_loglevel_mapping___##_provider##___##_name		       \
+	__attribute__((weakref ("_loglevel_mapping___" #_provider "___" #_name))); \
+const struct lttng_event_desc __event_desc___##_provider##_##_name = {	       \
+	.fields = __event_fields___##_provider##___##_template,		       \
+	.name = #_provider ":" #_name,					       \
+	.probe_callback = (void *) &__event_probe__##_provider##___##_template,\
+	.nr_fields = _TP_ARRAY_SIZE(__event_fields___##_provider##___##_template), \
+	.loglevel = &__ref_loglevel_mapping___##_provider##___##_name,	       \
+};
+
+#include TRACEPOINT_INCLUDE
 
-static struct tracepoint_loglevel _TP_COMBINE_TOKENS(__tracepoint_loglevels__, TRACEPOINT_PROVIDER)[] = {
+/*
+ * Stage 8.2 of tracepoint event generation.
+ *
+ * Create array of events.
+ */
+
+/* Reset all macros within TRACEPOINT_EVENT */
+#include <lttng/ust-tracepoint-event-reset.h>
+
+#undef TRACEPOINT_EVENT_INSTANCE
+#define TRACEPOINT_EVENT_INSTANCE(_provider, _template, _name, _args)	       \
+	&__event_desc___##_provider##_##_name,
+
+static const struct lttng_event_desc *_TP_COMBINE_TOKENS(__event_desc___, TRACEPOINT_PROVIDER)[] = {
 #include TRACEPOINT_INCLUDE
 };
 
+
 /*
  * Stage 9 of tracepoint event generation.
  *
@@ -509,9 +528,11 @@ static struct tracepoint_loglevel _TP_COMBINE_TOKENS(__tracepoint_loglevels__, T
 
 /* non-const because list head will be modified when registered. */
 static struct lttng_probe_desc _TP_COMBINE_TOKENS(__probe_desc___, TRACEPOINT_PROVIDER) = {
+	.provider = __tp_stringify(TRACEPOINT_PROVIDER),
 	.event_desc = _TP_COMBINE_TOKENS(__event_desc___, TRACEPOINT_PROVIDER),
 	.nr_events = _TP_ARRAY_SIZE(_TP_COMBINE_TOKENS(__event_desc___, TRACEPOINT_PROVIDER)),
-	.loglevels = _TP_COMBINE_TOKENS(__tracepoint_loglevels__, TRACEPOINT_PROVIDER),
+	.loglevels = _TP_COMBINE_TOKENS(__tracepoint_loglevel_enum__, TRACEPOINT_PROVIDER),
+	.nr_loglevels = _TP_ARRAY_SIZE(_TP_COMBINE_TOKENS(__tracepoint_loglevel_enum__, TRACEPOINT_PROVIDER)),
 };
 
 /*
diff --git a/include/ust-comm.h b/include/ust-comm.h
index deb0438b..64d91c98 100644
--- a/include/ust-comm.h
+++ b/include/ust-comm.h
@@ -130,6 +130,7 @@ struct ustcomm_ust_msg {
 		struct lttng_ust_context context;
 		struct lttng_ust_tracer_version version;
 		char tracepoint_list_entry[LTTNG_UST_SYM_NAME_LEN];
+		struct lttng_ust_loglevel loglevel_list_entry;
 	} u;
 };
 
@@ -151,6 +152,7 @@ struct ustcomm_ust_reply {
 		} stream;
 		struct lttng_ust_tracer_version version;
 		char tracepoint_list_entry[LTTNG_UST_SYM_NAME_LEN];
+		struct lttng_ust_loglevel loglevel_list_entry;
 	} u;
 };
 
diff --git a/liblttng-ust/ltt-events.c b/liblttng-ust/ltt-events.c
index b852b313..06d2f897 100644
--- a/liblttng-ust/ltt-events.c
+++ b/liblttng-ust/ltt-events.c
@@ -409,6 +409,13 @@ int ltt_event_create(struct ltt_channel *chan,
 				goto add_pending_error;
 		}
 		break;
+	case LTTNG_UST_TRACEPOINT_LOGLEVEL:
+		/*
+		 * TODO: add tracepoint loglevel to hash table, with
+		 * event info. Enable all events corresponding to
+		 * loglevel.
+		 */
+		break;
 	default:
 		WARN_ON_ONCE(1);
 	}
diff --git a/liblttng-ust/ltt-probes.c b/liblttng-ust/ltt-probes.c
index 9b25900d..5f55bfa8 100644
--- a/liblttng-ust/ltt-probes.c
+++ b/liblttng-ust/ltt-probes.c
@@ -21,6 +21,18 @@
  */
 static CDS_LIST_HEAD(probe_list);
 
+static
+const struct lttng_probe_desc *find_provider(const char *provider)
+{
+	struct lttng_probe_desc *iter;
+
+	cds_list_for_each_entry(iter, &probe_list, head) {
+		if (!strcmp(iter->provider, provider))
+			return iter;
+	}
+	return NULL;
+}
+
 static
 const struct lttng_event_desc *find_event(const char *name)
 {
@@ -29,8 +41,8 @@ const struct lttng_event_desc *find_event(const char *name)
 
 	cds_list_for_each_entry(probe_desc, &probe_list, head) {
 		for (i = 0; i < probe_desc->nr_events; i++) {
-			if (!strcmp(probe_desc->event_desc[i].name, name))
-				return &probe_desc->event_desc[i];
+			if (!strcmp(probe_desc->event_desc[i]->name, name))
+				return probe_desc->event_desc[i];
 		}
 	}
 	return NULL;
@@ -38,27 +50,47 @@ const struct lttng_event_desc *find_event(const char *name)
 
 int ltt_probe_register(struct lttng_probe_desc *desc)
 {
+	struct lttng_probe_desc *iter;
 	int ret = 0;
 	int i;
 
 	ust_lock();
+	if (find_provider(desc->provider)) {
+		ret = -EEXIST;
+		goto end;
+	}
 	/*
 	 * TODO: This is O(N^2). Turn into a hash table when probe registration
 	 * overhead becomes an issue.
 	 */
 	for (i = 0; i < desc->nr_events; i++) {
-		if (find_event(desc->event_desc[i].name)) {
+		if (find_event(desc->event_desc[i]->name)) {
 			ret = -EEXIST;
 			goto end;
 		}
 	}
+
+	/*
+	 * We sort the providers by struct lttng_probe_desc pointer
+	 * address.
+	 */
+	cds_list_for_each_entry_reverse(iter, &probe_list, head) {
+		BUG_ON(iter == desc); /* Should never be in the list twice */
+		if (iter < desc) {
+			/* We belong to the location right after iter. */
+			cds_list_add(&desc->head, &iter->head);
+			goto desc_added;
+		}
+	}
+	/* We should be added at the head of the list */
 	cds_list_add(&desc->head, &probe_list);
+desc_added:
 
 	/*
 	 * fix the events awaiting probe load.
 	 */
 	for (i = 0; i < desc->nr_events; i++) {
-		ret = pending_probe_fix_events(&desc->event_desc[i]);
+		ret = pending_probe_fix_events(desc->event_desc[i]);
 		assert(!ret);
 	}
 end:
@@ -89,81 +121,3 @@ const struct lttng_event_desc *ltt_event_get(const char *name)
 void ltt_event_put(const struct lttng_event_desc *event)
 {
 }
-
-#if 0
-static
-void *tp_list_start(struct seq_file *m, loff_t *pos)
-{
-	struct lttng_probe_desc *probe_desc;
-	int iter = 0, i;
-
-	pthread_mutex_lock(&probe_mutex);
-	cds_list_for_each_entry(probe_desc, &probe_list, head) {
-		for (i = 0; i < probe_desc->nr_events; i++) {
-			if (iter++ >= *pos)
-				return (void *) &probe_desc->event_desc[i];
-		}
-	}
-	/* End of list */
-	return NULL;
-}
-
-static
-void *tp_list_next(struct seq_file *m, void *p, loff_t *ppos)
-{
-	struct lttng_probe_desc *probe_desc;
-	int iter = 0, i;
-
-	(*ppos)++;
-	cds_list_for_each_entry(probe_desc, &probe_list, head) {
-		for (i = 0; i < probe_desc->nr_events; i++) {
-			if (iter++ >= *ppos)
-				return (void *) &probe_desc->event_desc[i];
-		}
-	}
-	/* End of list */
-	return NULL;
-}
-
-static
-void tp_list_stop(struct seq_file *m, void *p)
-{
-	pthread_mutex_unlock(&probe_mutex);
-}
-
-static
-int tp_list_show(struct seq_file *m, void *p)
-{
-	const struct lttng_event_desc *probe_desc = p;
-
-	/*
-	 * Don't export lttng internal events (metadata).
-	 */
-	if (!strncmp(probe_desc->name, "lttng_", sizeof("lttng_") - 1))
-		return 0;
-	seq_printf(m,	"event { name = %s; };\n",
-		   probe_desc->name);
-	return 0;
-}
-
-static
-const struct seq_operations lttng_tracepoint_list_seq_ops = {
-	.start = tp_list_start,
-	.next = tp_list_next,
-	.stop = tp_list_stop,
-	.show = tp_list_show,
-};
-
-static
-int lttng_tracepoint_list_open(struct inode *inode, struct file *file)
-{
-	return seq_open(file, &lttng_tracepoint_list_seq_ops);
-}
-
-const struct file_operations lttng_tracepoint_list_fops = {
-	.open = lttng_tracepoint_list_open,
-	.read = seq_read,
-	.llseek = seq_lseek,
-	.release = seq_release,
-};
-#endif //0
diff --git a/liblttng-ust/lttng-ust-abi.c b/liblttng-ust/lttng-ust-abi.c
index e6ffa41f..6be716be 100644
--- a/liblttng-ust/lttng-ust-abi.c
+++ b/liblttng-ust/lttng-ust-abi.c
@@ -39,11 +39,19 @@ struct ltt_tracepoint_list {
 	int got_first;
 };
 
+struct ltt_loglevel_list {
+	struct loglevel_iter *iter;
+	int got_first;
+};
+
 static int lttng_ust_abi_close_in_progress;
 
 static
 int lttng_abi_tracepoint_list(void);
 
+static
+int lttng_abi_loglevel_list(void);
+
 /*
  * Object descriptor table. Should be protected from concurrent access
  * by the caller.
@@ -210,6 +218,7 @@ static const struct lttng_ust_objd_ops lttng_metadata_ops;
 static const struct lttng_ust_objd_ops lttng_event_ops;
 static const struct lttng_ust_objd_ops lib_ring_buffer_objd_ops;
 static const struct lttng_ust_objd_ops lttng_tracepoint_list_ops;
+static const struct lttng_ust_objd_ops lttng_loglevel_list_ops;
 
 enum channel_type {
 	PER_CPU_CHANNEL,
@@ -294,6 +303,8 @@ long lttng_abi_add_context(int objd,
  *		Returns a file descriptor listing available tracepoints
  *	LTTNG_UST_WAIT_QUIESCENT
  *		Returns after all previously running probes have completed
+ *	LTTNG_UST_LOGLEVEL_LIST
+ *		Returns a file descriptor listing available loglevels
  *
  * The returned session will be deleted when its file descriptor is closed.
  */
@@ -311,6 +322,8 @@ long lttng_cmd(int objd, unsigned int cmd, unsigned long arg)
 	case LTTNG_UST_WAIT_QUIESCENT:
 		synchronize_trace();
 		return 0;
+	case LTTNG_UST_LOGLEVEL_LIST:
+		return lttng_abi_loglevel_list();
 	default:
 		return -EINVAL;
 	}
@@ -598,6 +611,112 @@ static const struct lttng_ust_objd_ops lttng_tracepoint_list_ops = {
 	.cmd = lttng_tracepoint_list_cmd,
 };
 
+/*
+ * beware: we don't keep the mutex over the send, but we must walk the
+ * whole list each time we are called again. So sending one loglevel
+ * entry at a time means this is O(n^2). TODO: do as in the kernel and
+ * send multiple tracepoints for each call to amortize this cost.
+ */
+static
+void ltt_loglevel_list_get(struct ltt_loglevel_list *list,
+		const char *loglevel_provider,
+		const char *loglevel,
+		long *value)
+{
+#if 0
+next:
+	if (!list->got_first) {
+		//tp_loglevel_iter_start(&list->iter);
+		list->got_first = 1;
+		goto copy;
+	}
+	//tp_loglevel_iter_next(&list->iter);
+copy:
+	if (!list->iter->desc.provider) {
+		loglevel_provider[0] = '\0';	/* end of list */
+	} else {
+		memcpy(loglevel_provider, list->iter->desc.provider,
+			LTTNG_UST_SYM_NAME_LEN);
+		memcpy(loglevel, list->iter.loglevel,
+			LTTNG_UST_SYM_NAME_LEN);
+		*value = list->iter.value;
+	}
+#endif
+}
+
+static
+long lttng_loglevel_list_cmd(int objd, unsigned int cmd, unsigned long arg)
+{
+	struct ltt_loglevel_list *list = objd_private(objd);
+	struct lttng_ust_loglevel *loglevel_list_entry =
+		(struct lttng_ust_loglevel *) arg;
+
+	switch (cmd) {
+	case LTTNG_UST_LOGLEVEL_LIST_GET:
+/*
+		ltt_tracepoint_list_get(list,
+			loglevel_list_entry->provider,
+			loglevel_list_entry->loglevel,
+			&loglevel_list_entry->value);
+		if (loglevel_list_entry->provider[0] == '\0')
+			return -ENOENT;
+*/
+		return 0;
+	default:
+		return -EINVAL;
+	}
+}
+
+static
+int lttng_abi_loglevel_list(void)
+{
+	int list_objd, ret;
+	struct ltt_loglevel_list *list;
+
+	list_objd = objd_alloc(NULL, &lttng_loglevel_list_ops);
+	if (list_objd < 0) {
+		ret = list_objd;
+		goto objd_error;
+	}
+	list = zmalloc(sizeof(*list));
+	if (!list) {
+		ret = -ENOMEM;
+		goto alloc_error;
+	}
+	objd_set_private(list_objd, list);
+
+	return list_objd;
+
+alloc_error:
+	{
+		int err;
+
+		err = lttng_ust_objd_unref(list_objd);
+		assert(!err);
+	}
+objd_error:
+	return ret;
+}
+
+static
+int lttng_release_loglevel_list(int objd)
+{
+	struct ltt_loglevel_list *list = objd_private(objd);
+
+	if (list) {
+		//tp_loglevel_iter_stop(&list->iter);
+		free(list);
+		return 0;
+	} else {
+		return -EINVAL;
+	}
+}
+
+static const struct lttng_ust_objd_ops lttng_loglevel_list_ops = {
+	.release = lttng_release_loglevel_list,
+	.cmd = lttng_loglevel_list_cmd,
+};
+
 struct stream_priv_data {
 	struct lttng_ust_lib_ring_buffer *buf;
 	struct ltt_channel *ltt_chan;
diff --git a/tests/demo/ust_tests_demo3.h b/tests/demo/ust_tests_demo3.h
index f8ea618c..71241ec6 100644
--- a/tests/demo/ust_tests_demo3.h
+++ b/tests/demo/ust_tests_demo3.h
@@ -35,7 +35,7 @@ TRACEPOINT_EVENT(ust_tests_demo3, done,
 		ctf_integer(int, value, value)
 	)
 )
-TRACEPOINT_LOGLEVEL(ust_tests_demo, done, test1)
+TRACEPOINT_LOGLEVEL(ust_tests_demo3, done, test1)
 
 #endif /* _TRACEPOINT_UST_TESTS_DEMO3_H */