X-Git-Url: http://git.efficios.com/?p=lttng-tools.git;a=blobdiff_plain;f=src%2Fbin%2Flttng-sessiond%2Fust-app.c;h=d1fa0d09cb2b04d75b3419cd6fa969a602253eb0;hp=12ea705bbe0e4f631cef81a45f2ceaae6af8a2d7;hb=98f595d4c5972c980b6e5882ca199b4cc6c84abc;hpb=f45e313daba4dc617f3036ca0ce0e6de305a4ba5

diff --git a/src/bin/lttng-sessiond/ust-app.c b/src/bin/lttng-sessiond/ust-app.c
index 12ea705bb..d1fa0d09c 100644
--- a/src/bin/lttng-sessiond/ust-app.c
+++ b/src/bin/lttng-sessiond/ust-app.c
@@ -34,30 +34,44 @@
 
 #include "buffer-registry.h"
 #include "fd-limit.h"
-#include "health.h"
+#include "health-sessiond.h"
 #include "ust-app.h"
 #include "ust-consumer.h"
 #include "ust-ctl.h"
 #include "utils.h"
 
-/* Next available channel key. */
-static unsigned long next_channel_key;
-static unsigned long next_session_id;
+/* Next available channel key. Access under next_channel_key_lock. */
+static uint64_t _next_channel_key;
+static pthread_mutex_t next_channel_key_lock = PTHREAD_MUTEX_INITIALIZER;
+
+/* Next available session ID. Access under next_session_id_lock. */
+static uint64_t _next_session_id;
+static pthread_mutex_t next_session_id_lock = PTHREAD_MUTEX_INITIALIZER;
 
 /*
- * Return the atomically incremented value of next_channel_key.
+ * Return the incremented value of next_channel_key.
  */
-static inline unsigned long get_next_channel_key(void)
+static uint64_t get_next_channel_key(void)
 {
-	return uatomic_add_return(&next_channel_key, 1);
+	uint64_t ret;
+
+	pthread_mutex_lock(&next_channel_key_lock);
+	ret = ++_next_channel_key;
+	pthread_mutex_unlock(&next_channel_key_lock);
+	return ret;
 }
 
 /*
  * Return the atomically incremented value of next_session_id.
  */
-static inline unsigned long get_next_session_id(void)
+static uint64_t get_next_session_id(void)
 {
-	return uatomic_add_return(&next_session_id, 1);
+	uint64_t ret;
+
+	pthread_mutex_lock(&next_session_id_lock);
+	ret = ++_next_session_id;
+	pthread_mutex_unlock(&next_session_id_lock);
+	return ret;
 }
 
 static void copy_channel_attr_to_ustctl(
@@ -90,7 +104,7 @@ static int ht_match_ust_app_event(struct cds_lfht_node *node, const void *_key)
 	event = caa_container_of(node, struct ust_app_event, node.node);
 	key = _key;
 
-	/* Match the 3 elements of the key: name, filter and loglevel. */
+	/* Match the 4 elements of the key: name, filter, loglevel, exclusions */
 
 	/* Event name */
 	if (strncmp(event->attr.name, key->name, sizeof(event->attr.name)) != 0) {
@@ -126,6 +140,21 @@ static int ht_match_ust_app_event(struct cds_lfht_node *node, const void *_key)
 		}
 	}
 
+	/* One of the exclusions is NULL, fail. */
+	if ((key->exclusion && !event->exclusion) || (!key->exclusion && event->exclusion)) {
+		goto no_match;
+	}
+
+	if (key->exclusion && event->exclusion) {
+		/* Both exclusions exists, check count followed by the names. */
+		if (event->exclusion->count != key->exclusion->count ||
+				memcmp(event->exclusion->names, key->exclusion->names,
+					event->exclusion->count * LTTNG_UST_SYM_NAME_LEN) != 0) {
+			goto no_match;
+		}
+	}
+
+
 	/* Match. */
 	return 1;
 
@@ -152,6 +181,7 @@ static void add_unique_ust_app_event(struct ust_app_channel *ua_chan,
 	key.name = event->attr.name;
 	key.filter = event->filter;
 	key.loglevel = event->attr.loglevel;
+	key.exclusion = event->exclusion;
 
 	node_ptr = cds_lfht_add_unique(ht->ht,
 			ht->hash_fct(event->node.key, lttng_ht_seed),
@@ -257,7 +287,8 @@ void delete_ust_app_event(int sock, struct ust_app_event *ua_event)
 	assert(ua_event);
 
 	free(ua_event->filter);
-
+	if (ua_event->exclusion != NULL)
+		free(ua_event->exclusion);
 	if (ua_event->obj != NULL) {
 		ret = ustctl_release_object(sock, ua_event->obj);
 		if (ret < 0 && ret != -EPIPE && ret != -LTTNG_UST_ERR_EXITING) {
@@ -350,6 +381,7 @@ void delete_ust_app_channel(int sock, struct ust_app_channel *ua_chan,
 
 	/* Wipe context */
 	cds_lfht_for_each_entry(ua_chan->ctx->ht, &iter.iter, ua_ctx, node.node) {
+		cds_list_del(&ua_ctx->list);
 		ret = lttng_ht_del(ua_chan->ctx, &iter);
 		assert(!ret);
 		delete_ust_app_ctx(sock, ua_ctx);
@@ -363,16 +395,19 @@ void delete_ust_app_channel(int sock, struct ust_app_channel *ua_chan,
 		delete_ust_app_event(sock, ua_event);
 	}
 
-	/* Wipe and free registry from session registry. */
-	registry = get_session_registry(ua_chan->session);
-	if (registry) {
-		ust_registry_channel_del_free(registry, ua_chan->key);
+	if (ua_chan->session->buffer_type == LTTNG_BUFFER_PER_PID) {
+		/* Wipe and free registry from session registry. */
+		registry = get_session_registry(ua_chan->session);
+		if (registry) {
+			ust_registry_channel_del_free(registry, ua_chan->key);
+		}
 	}
 
 	if (ua_chan->obj != NULL) {
 		/* Remove channel from application UST object descriptor. */
 		iter.iter.node = &ua_chan->ust_objd_node.node;
-		lttng_ht_del(app->ust_objd, &iter);
+		ret = lttng_ht_del(app->ust_objd, &iter);
+		assert(!ret);
 		ret = ustctl_release_object(sock, ua_chan->obj);
 		if (ret < 0 && ret != -EPIPE && ret != -LTTNG_UST_ERR_EXITING) {
 			ERR("UST app sock %d release channel obj failed with ret %d",
@@ -447,6 +482,25 @@ push_data:
 	ret = consumer_push_metadata(socket, registry->metadata_key,
 			metadata_str, len, offset);
 	if (ret < 0) {
+		/*
+		 * There is an acceptable race here between the registry metadata key
+		 * assignment and the creation on the consumer. The session daemon can
+		 * concurrently push metadata for this registry while being created on
+		 * the consumer since the metadata key of the registry is assigned
+		 * *before* it is setup to avoid the consumer to ask for metadata that
+		 * could possibly be not found in the session daemon.
+		 *
+		 * The metadata will get pushed either by the session being stopped or
+		 * the consumer requesting metadata if that race is triggered.
+		 */
+		if (ret == -LTTCOMM_CONSUMERD_CHANNEL_FAIL) {
+			ret = 0;
+		}
+
+		/* Update back the actual metadata len sent since it failed here. */
+		pthread_mutex_lock(&registry->lock);
+		registry->metadata_len_sent -= len;
+		pthread_mutex_unlock(&registry->lock);
 		ret_val = ret;
 		goto error_push;
 	}
@@ -809,6 +863,7 @@ struct ust_app_channel *alloc_ust_app_channel(char *name,
 	lttng_ht_node_init_str(&ua_chan->node, ua_chan->name);
 
 	CDS_INIT_LIST_HEAD(&ua_chan->streams.head);
+	CDS_INIT_LIST_HEAD(&ua_chan->ctx_list);
 
 	/* Copy attributes */
 	if (attr) {
@@ -900,6 +955,8 @@ struct ust_app_ctx *alloc_ust_app_ctx(struct lttng_ust_context *uctx)
 		goto error;
 	}
 
+	CDS_INIT_LIST_HEAD(&ua_ctx->list);
+
 	if (uctx) {
 		memcpy(&ua_ctx->ctx, uctx, sizeof(ua_ctx->ctx));
 	}
@@ -937,8 +994,7 @@ error:
  * Find an ust_app using the sock and return it. RCU read side lock must be
  * held before calling this helper function.
  */
-static
-struct ust_app *find_app_by_sock(int sock)
+struct ust_app *ust_app_find_by_sock(int sock)
 {
 	struct lttng_ht_node_ulong *node;
 	struct lttng_ht_iter iter;
@@ -986,7 +1042,8 @@ error:
  * Return an ust_app_event object or NULL on error.
  */
 static struct ust_app_event *find_ust_app_event(struct lttng_ht *ht,
-		char *name, struct lttng_ust_filter_bytecode *filter, int loglevel)
+		char *name, struct lttng_ust_filter_bytecode *filter, int loglevel,
+		const struct lttng_event_exclusion *exclusion)
 {
 	struct lttng_ht_iter iter;
 	struct lttng_ht_node_str *node;
@@ -1000,6 +1057,8 @@ static struct ust_app_event *find_ust_app_event(struct lttng_ht *ht,
 	key.name = name;
 	key.filter = filter;
 	key.loglevel = loglevel;
+	/* lttng_event_exclusion and lttng_ust_event_exclusion structures are similar */
+	key.exclusion = (struct lttng_ust_event_exclusion *)exclusion;
 
 	/* Lookup using the event name as hash and a custom match fct. */
 	cds_lfht_lookup(ht->ht, ht->hash_fct((void *) name, lttng_ht_seed),
@@ -1035,6 +1094,12 @@ int create_ust_channel_context(struct ust_app_channel *ua_chan,
 			ERR("UST app create channel context failed for app (pid: %d) "
 					"with ret %d", app->pid, ret);
 		} else {
+			/*
+			 * This is normal behavior, an application can die during the
+			 * creation process. Don't report an error so the execution can
+			 * continue normally.
+			 */
+			ret = 0;
 			DBG3("UST app disable event failed. Application is dead.");
 		}
 		goto error;
@@ -1073,6 +1138,12 @@ int set_ust_event_filter(struct ust_app_event *ua_event,
 			ERR("UST app event %s filter failed for app (pid: %d) "
 					"with ret %d", ua_event->attr.name, app->pid, ret);
 		} else {
+			/*
+			 * This is normal behavior, an application can die during the
+			 * creation process. Don't report an error so the execution can
+			 * continue normally.
+			 */
+			ret = 0;
 			DBG3("UST app filter event failed. Application is dead.");
 		}
 		goto error;
@@ -1085,6 +1156,47 @@ error:
 	return ret;
 }
 
+/*
+ * Set event exclusions on the tracer.
+ */
+static
+int set_ust_event_exclusion(struct ust_app_event *ua_event,
+		struct ust_app *app)
+{
+	int ret;
+
+	health_code_update();
+
+	if (!ua_event->exclusion || !ua_event->exclusion->count) {
+		ret = 0;
+		goto error;
+	}
+
+	ret = ustctl_set_exclusion(app->sock, ua_event->exclusion,
+			ua_event->obj);
+	if (ret < 0) {
+		if (ret != -EPIPE && ret != -LTTNG_UST_ERR_EXITING) {
+			ERR("UST app event %s exclusions failed for app (pid: %d) "
+					"with ret %d", ua_event->attr.name, app->pid, ret);
+		} else {
+			/*
+			 * This is normal behavior, an application can die during the
+			 * creation process. Don't report an error so the execution can
+			 * continue normally.
+			 */
+			ret = 0;
+			DBG3("UST app event exclusion failed. Application is dead.");
+		}
+		goto error;
+	}
+
+	DBG2("UST exclusion set successfully for event %s", ua_event->name);
+
+error:
+	health_code_update();
+	return ret;
+}
+
 /*
  * Disable the specified event on to UST tracer for the UST session.
  */
@@ -1102,6 +1214,12 @@ static int disable_ust_event(struct ust_app *app,
 					"and session handle %d with ret %d",
 					ua_event->attr.name, app->pid, ua_sess->handle, ret);
 		} else {
+			/*
+			 * This is normal behavior, an application can die during the
+			 * creation process. Don't report an error so the execution can
+			 * continue normally.
+			 */
+			ret = 0;
 			DBG3("UST app disable event failed. Application is dead.");
 		}
 		goto error;
@@ -1132,6 +1250,12 @@ static int disable_ust_channel(struct ust_app *app,
 					"and session handle %d with ret %d",
 					ua_chan->name, app->pid, ua_sess->handle, ret);
 		} else {
+			/*
+			 * This is normal behavior, an application can die during the
+			 * creation process. Don't report an error so the execution can
+			 * continue normally.
+			 */
+			ret = 0;
 			DBG3("UST app disable channel failed. Application is dead.");
 		}
 		goto error;
@@ -1162,6 +1286,12 @@ static int enable_ust_channel(struct ust_app *app,
 					"and session handle %d with ret %d",
 					ua_chan->name, app->pid, ua_sess->handle, ret);
 		} else {
+			/*
+			 * This is normal behavior, an application can die during the
+			 * creation process. Don't report an error so the execution can
+			 * continue normally.
+			 */
+			ret = 0;
 			DBG3("UST app enable channel failed. Application is dead.");
 		}
 		goto error;
@@ -1194,6 +1324,12 @@ static int enable_ust_event(struct ust_app *app,
 					"and session handle %d with ret %d",
 					ua_event->attr.name, app->pid, ua_sess->handle, ret);
 		} else {
+			/*
+			 * This is normal behavior, an application can die during the
+			 * creation process. Don't report an error so the execution can
+			 * continue normally.
+			 */
+			ret = 0;
 			DBG3("UST app enable event failed. Application is dead.");
 		}
 		goto error;
@@ -1274,6 +1410,12 @@ int create_ust_event(struct ust_app *app, struct ust_app_session *ua_sess,
 			ERR("Error ustctl create event %s for app pid: %d with ret %d",
 					ua_event->attr.name, app->pid, ret);
 		} else {
+			/*
+			 * This is normal behavior, an application can die during the
+			 * creation process. Don't report an error so the execution can
+			 * continue normally.
+			 */
+			ret = 0;
 			DBG3("UST app create event failed. Application is dead.");
 		}
 		goto error;
@@ -1294,6 +1436,14 @@ int create_ust_event(struct ust_app *app, struct ust_app_session *ua_sess,
 		}
 	}
 
+	/* Set exclusions for the event */
+	if (ua_event->exclusion) {
+		ret = set_ust_event_exclusion(ua_event, app);
+		if (ret < 0) {
+			goto error;
+		}
+	}
+
 	/* If event not enabled, disable it on the tracer */
 	if (ua_event->enabled == 0) {
 		ret = disable_ust_event(app, ua_sess, ua_event);
@@ -1329,6 +1479,8 @@ error:
 static void shadow_copy_event(struct ust_app_event *ua_event,
 		struct ltt_ust_event *uevent)
 {
+	size_t exclusion_alloc_size;
+
 	strncpy(ua_event->name, uevent->attr.name, sizeof(ua_event->name));
 	ua_event->name[sizeof(ua_event->name) - 1] = '\0';
 
@@ -1342,6 +1494,19 @@ static void shadow_copy_event(struct ust_app_event *ua_event,
 		ua_event->filter = alloc_copy_ust_app_filter(uevent->filter);
 		/* Filter might be NULL here in case of ENONEM. */
 	}
+
+	/* Copy exclusion data */
+	if (uevent->exclusion) {
+		exclusion_alloc_size = sizeof(struct lttng_ust_event_exclusion) +
+				LTTNG_UST_SYM_NAME_LEN * uevent->exclusion->count;
+		ua_event->exclusion = zmalloc(exclusion_alloc_size);
+		if (ua_event->exclusion == NULL) {
+			PERROR("malloc");
+		} else {
+			memcpy(ua_event->exclusion, uevent->exclusion,
+					exclusion_alloc_size);
+		}
+	}
 }
 
 /*
@@ -1379,7 +1544,7 @@ static void shadow_copy_channel(struct ust_app_channel *ua_chan,
 	ua_chan->enabled = uchan->enabled;
 	ua_chan->tracing_channel_id = uchan->id;
 
-	cds_lfht_for_each_entry(uchan->ctx->ht, &iter.iter, uctx, node.node) {
+	cds_list_for_each_entry(uctx, &uchan->ctx_list, list) {
 		ua_ctx = alloc_ust_app_ctx(&uctx->ctx);
 		if (ua_ctx == NULL) {
 			continue;
@@ -1387,12 +1552,13 @@ static void shadow_copy_channel(struct ust_app_channel *ua_chan,
 		lttng_ht_node_init_ulong(&ua_ctx->node,
 				(unsigned long) ua_ctx->ctx.ctx);
 		lttng_ht_add_unique_ulong(ua_chan->ctx, &ua_ctx->node);
+		cds_list_add_tail(&ua_ctx->list, &ua_chan->ctx_list);
 	}
 
 	/* Copy all events from ltt ust channel to ust app channel */
 	cds_lfht_for_each_entry(uchan->events->ht, &iter.iter, uevent, node.node) {
 		ua_event = find_ust_app_event(ua_chan->events, uevent->attr.name,
-				uevent->filter, uevent->attr.loglevel);
+				uevent->filter, uevent->attr.loglevel, uevent->exclusion);
 		if (ua_event == NULL) {
 			DBG2("UST event %s not found on shadow copy channel",
 					uevent->attr.name);
@@ -1440,6 +1606,8 @@ static void shadow_copy_session(struct ust_app_session *ua_sess,
 	ua_sess->bits_per_long = app->bits_per_long;
 	/* There is only one consumer object per session possible. */
 	ua_sess->consumer = usess->consumer;
+	ua_sess->output_traces = usess->output_traces;
+	ua_sess->live_timer_interval = usess->live_timer_interval;
 
 	switch (ua_sess->buffer_type) {
 	case LTTNG_BUFFER_PER_PID:
@@ -1503,7 +1671,7 @@ void __lookup_session_by_app(struct ltt_ust_session *usess,
 			struct ust_app *app, struct lttng_ht_iter *iter)
 {
 	/* Get right UST app session from app */
-	lttng_ht_lookup(app->sessions, (void *)((unsigned long) usess->id), iter);
+	lttng_ht_lookup(app->sessions, &usess->id, iter);
 }
 
 /*
@@ -1514,10 +1682,10 @@ static struct ust_app_session *lookup_session_by_app(
 		struct ltt_ust_session *usess, struct ust_app *app)
 {
 	struct lttng_ht_iter iter;
-	struct lttng_ht_node_ulong *node;
+	struct lttng_ht_node_u64 *node;
 
 	__lookup_session_by_app(usess, app, &iter);
-	node = lttng_ht_iter_get_node_ulong(&iter);
+	node = lttng_ht_iter_get_node_u64(&iter);
 	if (node == NULL) {
 		goto error;
 	}
@@ -1667,7 +1835,7 @@ static int create_ust_app_session(struct ltt_ust_session *usess,
 
 	ua_sess = lookup_session_by_app(usess, app);
 	if (ua_sess == NULL) {
-		DBG2("UST app pid: %d session id %d not found, creating it",
+		DBG2("UST app pid: %d session id %" PRIu64 " not found, creating it",
 				app->pid, usess->id);
 		ua_sess = alloc_ust_app_session(app);
 		if (ua_sess == NULL) {
@@ -1710,6 +1878,13 @@ static int create_ust_app_session(struct ltt_ust_session *usess,
 						app->pid, ret);
 			} else {
 				DBG("UST app creating session failed. Application is dead");
+				/*
+				 * This is normal behavior, an application can die during the
+				 * creation process. Don't report an error so the execution can
+				 * continue normally. This will get flagged ENOTCONN and the
+				 * caller will handle it.
+				 */
+				ret = 0;
 			}
 			delete_ust_app_session(-1, ua_sess, app);
 			if (ret != -ENOMEM) {
@@ -1725,9 +1900,9 @@ static int create_ust_app_session(struct ltt_ust_session *usess,
 		ua_sess->handle = ret;
 
 		/* Add ust app session to app's HT */
-		lttng_ht_node_init_ulong(&ua_sess->node,
-				(unsigned long) ua_sess->tracing_id);
-		lttng_ht_add_unique_ulong(app->sessions, &ua_sess->node);
+		lttng_ht_node_init_u64(&ua_sess->node,
+				ua_sess->tracing_id);
+		lttng_ht_add_unique_u64(app->sessions, &ua_sess->node);
 
 		DBG2("UST app session created successfully with handle %d", ret);
 	}
@@ -1778,6 +1953,7 @@ int create_ust_app_channel_context(struct ust_app_session *ua_sess,
 
 	lttng_ht_node_init_ulong(&ua_ctx->node, (unsigned long) ua_ctx->ctx.ctx);
 	lttng_ht_add_unique_ulong(ua_chan->ctx, &ua_ctx->node);
+	cds_list_add_tail(&ua_ctx->list, &ua_chan->ctx_list);
 
 	ret = create_ust_channel_context(ua_chan, ua_ctx, app);
 	if (ret < 0) {
@@ -1864,7 +2040,7 @@ static int enable_ust_app_channel(struct ust_app_session *ua_sess,
 	lttng_ht_lookup(ua_sess->channels, (void *)uchan->name, &iter);
 	ua_chan_node = lttng_ht_iter_get_node_str(&iter);
 	if (ua_chan_node == NULL) {
-		DBG2("Unable to find channel %s in ust session id %u",
+		DBG2("Unable to find channel %s in ust session id %" PRIu64,
 				uchan->name, ua_sess->tracing_id);
 		goto error;
 	}
@@ -1946,9 +2122,11 @@ static int do_consumer_create_channel(struct ltt_ust_session *usess,
 	 * Now get the channel from the consumer. This call wil populate the stream
 	 * list of that channel and set the ust objects.
 	 */
-	ret = ust_consumer_get_channel(socket, ua_chan);
-	if (ret < 0) {
-		goto error_destroy;
+	if (usess->consumer->enabled) {
+		ret = ust_consumer_get_channel(socket, ua_chan);
+		if (ret < 0) {
+			goto error_destroy;
+		}
 	}
 
 	rcu_read_unlock();
@@ -2115,6 +2293,7 @@ static int create_buffer_reg_channel(struct buffer_reg_session *reg_sess,
 	}
 	assert(reg_chan);
 	reg_chan->consumer_key = ua_chan->key;
+	reg_chan->subbuf_size = ua_chan->attr.subbuf_size;
 
 	/* Create and add a channel registry to session. */
 	ret = ust_registry_channel_add(reg_sess->reg.ust,
@@ -2492,7 +2671,7 @@ int create_ust_app_event(struct ust_app_session *ua_sess,
 
 	/* Get event node */
 	ua_event = find_ust_app_event(ua_chan->events, uevent->attr.name,
-			uevent->filter, uevent->attr.loglevel);
+			uevent->filter, uevent->attr.loglevel, uevent->exclusion);
 	if (ua_event != NULL) {
 		ret = -EEXIST;
 		goto end;
@@ -2610,10 +2789,8 @@ static int create_ust_app_metadata(struct ust_app_session *ua_sess,
 	ret = ust_consumer_ask_channel(ua_sess, metadata, consumer, socket,
 			registry);
 	if (ret < 0) {
-		/*
-		 * Safe because the metadata obj pointer is not set so the delete below
-		 * will not put a FD back again.
-		 */
+		/* Nullify the metadata key so we don't try to close it later on. */
+		registry->metadata_key = 0;
 		goto error_consumer;
 	}
 
@@ -2625,10 +2802,8 @@ static int create_ust_app_metadata(struct ust_app_session *ua_sess,
 	 */
 	ret = consumer_setup_metadata(socket, metadata->key);
 	if (ret < 0) {
-		/*
-		 * Safe because the metadata obj pointer is not set so the delete below
-		 * will not put a FD back again.
-		 */
+		/* Nullify the metadata key so we don't try to close it later on. */
+		registry->metadata_key = 0;
 		goto error_consumer;
 	}
 
@@ -2642,14 +2817,6 @@ error:
 	return ret;
 }
 
-/*
- * Return pointer to traceable apps list.
- */
-struct lttng_ht *ust_app_get_ht(void)
-{
-	return ust_app_ht;
-}
-
 /*
  * Return ust app pointer or NULL if not found. RCU read side lock MUST be
  * acquired before calling this function.
@@ -2721,7 +2888,7 @@ struct ust_app *ust_app_create(struct ust_register_msg *msg, int sock)
 
 	lta->v_major = msg->major;
 	lta->v_minor = msg->minor;
-	lta->sessions = lttng_ht_new(0, LTTNG_HT_TYPE_ULONG);
+	lta->sessions = lttng_ht_new(0, LTTNG_HT_TYPE_U64);
 	lta->ust_objd = lttng_ht_new(0, LTTNG_HT_TYPE_ULONG);
 	lta->notify_sock = -1;
 
@@ -2912,20 +3079,6 @@ void ust_app_unregister(int sock)
 	return;
 }
 
-/*
- * Return traceable_app_count
- */
-unsigned long ust_app_list_count(void)
-{
-	unsigned long count;
-
-	rcu_read_lock();
-	count = lttng_ht_get_count(ust_app_ht);
-	rcu_read_unlock();
-
-	return count;
-}
-
 /*
  * Fill events array with all events name of all registered apps.
  */
@@ -2972,13 +3125,19 @@ int ust_app_list_events(struct lttng_event **events)
 					&uiter)) != -LTTNG_UST_ERR_NOENT) {
 			/* Handle ustctl error. */
 			if (ret < 0) {
-				free(tmp_event);
-				if (ret != -LTTNG_UST_ERR_EXITING || ret != -EPIPE) {
+				if (ret != -LTTNG_UST_ERR_EXITING && ret != -EPIPE) {
 					ERR("UST app tp list get failed for app %d with ret %d",
 							app->sock, ret);
 				} else {
 					DBG3("UST app tp list get failed. Application is dead");
+					/*
+					 * This is normal behavior, an application can die during the
+					 * creation process. Don't report an error so the execution can
+					 * continue normally. Continue normal execution.
+					 */
+					break;
 				}
+				free(tmp_event);
 				goto rcu_error;
 			}
 
@@ -3066,13 +3225,19 @@ int ust_app_list_event_fields(struct lttng_event_field **fields)
 					&uiter)) != -LTTNG_UST_ERR_NOENT) {
 			/* Handle ustctl error. */
 			if (ret < 0) {
-				free(tmp_event);
-				if (ret != -LTTNG_UST_ERR_EXITING || ret != -EPIPE) {
+				if (ret != -LTTNG_UST_ERR_EXITING && ret != -EPIPE) {
 					ERR("UST app tp list field failed for app %d with ret %d",
 							app->sock, ret);
 				} else {
 					DBG3("UST app tp list field failed. Application is dead");
+					/*
+					 * This is normal behavior, an application can die during the
+					 * creation process. Don't report an error so the execution can
+					 * continue normally. Reset list and count for next app.
+					 */
+					break;
 				}
+				free(tmp_event);
 				goto rcu_error;
 			}
 
@@ -3095,12 +3260,13 @@ int ust_app_list_event_fields(struct lttng_event_field **fields)
 			}
 
 			memcpy(tmp_event[count].field_name, uiter.field_name, LTTNG_UST_SYM_NAME_LEN);
-			tmp_event[count].type = uiter.type;
+			/* Mapping between these enums matches 1 to 1. */
+			tmp_event[count].type = (enum lttng_event_field_type) uiter.type;
 			tmp_event[count].nowrite = uiter.nowrite;
 
 			memcpy(tmp_event[count].event.name, uiter.event_name, LTTNG_UST_SYM_NAME_LEN);
 			tmp_event[count].event.loglevel = uiter.loglevel;
-			tmp_event[count].event.type = LTTNG_UST_TRACEPOINT;
+			tmp_event[count].event.type = LTTNG_EVENT_TRACEPOINT;
 			tmp_event[count].event.pid = app->pid;
 			tmp_event[count].event.enabled = -1;
 			count++;
@@ -3190,7 +3356,7 @@ int ust_app_disable_channel_glb(struct ltt_ust_session *usess,
 		goto error;
 	}
 
-	DBG2("UST app disabling channel %s from global domain for session id %d",
+	DBG2("UST app disabling channel %s from global domain for session id %" PRIu64,
 			uchan->name, usess->id);
 
 	rcu_read_lock();
@@ -3251,7 +3417,7 @@ int ust_app_enable_channel_glb(struct ltt_ust_session *usess,
 		goto error;
 	}
 
-	DBG2("UST app enabling channel %s to global domain for session id %d",
+	DBG2("UST app enabling channel %s to global domain for session id %" PRIu64,
 			uchan->name, usess->id);
 
 	rcu_read_lock();
@@ -3299,7 +3465,8 @@ int ust_app_disable_event_glb(struct ltt_ust_session *usess,
 	struct ust_app_event *ua_event;
 
 	DBG("UST app disabling event %s for all apps in channel "
-			"%s for session id %d", uevent->attr.name, uchan->name, usess->id);
+			"%s for session id %" PRIu64,
+			uevent->attr.name, uchan->name, usess->id);
 
 	rcu_read_lock();
 
@@ -3322,7 +3489,7 @@ int ust_app_disable_event_glb(struct ltt_ust_session *usess,
 		lttng_ht_lookup(ua_sess->channels, (void *)uchan->name, &uiter);
 		ua_chan_node = lttng_ht_iter_get_node_str(&uiter);
 		if (ua_chan_node == NULL) {
-			DBG2("Channel %s not found in session id %d for app pid %d."
+			DBG2("Channel %s not found in session id %" PRIu64 " for app pid %d."
 					"Skipping", uchan->name, usess->id, app->pid);
 			continue;
 		}
@@ -3349,65 +3516,6 @@ int ust_app_disable_event_glb(struct ltt_ust_session *usess,
 	return ret;
 }
 
-/*
- * For a specific UST session and UST channel, the event for all
- * registered apps.
- */
-int ust_app_disable_all_event_glb(struct ltt_ust_session *usess,
-		struct ltt_ust_channel *uchan)
-{
-	int ret = 0;
-	struct lttng_ht_iter iter, uiter;
-	struct lttng_ht_node_str *ua_chan_node;
-	struct ust_app *app;
-	struct ust_app_session *ua_sess;
-	struct ust_app_channel *ua_chan;
-	struct ust_app_event *ua_event;
-
-	DBG("UST app disabling all event for all apps in channel "
-			"%s for session id %d", uchan->name, usess->id);
-
-	rcu_read_lock();
-
-	/* For all registered applications */
-	cds_lfht_for_each_entry(ust_app_ht->ht, &iter.iter, app, pid_n.node) {
-		if (!app->compatible) {
-			/*
-			 * TODO: In time, we should notice the caller of this error by
-			 * telling him that this is a version error.
-			 */
-			continue;
-		}
-		ua_sess = lookup_session_by_app(usess, app);
-		if (!ua_sess) {
-			/* The application has problem or is probably dead. */
-			continue;
-		}
-
-		/* Lookup channel in the ust app session */
-		lttng_ht_lookup(ua_sess->channels, (void *)uchan->name, &uiter);
-		ua_chan_node = lttng_ht_iter_get_node_str(&uiter);
-		/* If the channel is not found, there is a code flow error */
-		assert(ua_chan_node);
-
-		ua_chan = caa_container_of(ua_chan_node, struct ust_app_channel, node);
-
-		/* Disable each events of channel */
-		cds_lfht_for_each_entry(ua_chan->events->ht, &uiter.iter, ua_event,
-				node.node) {
-			ret = disable_ust_app_event(ua_sess, ua_event, app);
-			if (ret < 0) {
-				/* XXX: Report error someday... */
-				continue;
-			}
-		}
-	}
-
-	rcu_read_unlock();
-
-	return ret;
-}
-
 /*
  * For a specific UST session, create the channel for all registered apps.
  */
@@ -3423,7 +3531,7 @@ int ust_app_create_channel_glb(struct ltt_ust_session *usess,
 	assert(usess);
 	assert(uchan);
 
-	DBG2("UST app adding channel %s to UST domain for session id %d",
+	DBG2("UST app adding channel %s to UST domain for session id %" PRIu64,
 			uchan->name, usess->id);
 
 	rcu_read_lock();
@@ -3503,7 +3611,7 @@ int ust_app_enable_event_glb(struct ltt_ust_session *usess,
 	struct ust_app_channel *ua_chan;
 	struct ust_app_event *ua_event;
 
-	DBG("UST app enabling event %s for all apps for session id %d",
+	DBG("UST app enabling event %s for all apps for session id %" PRIu64,
 			uevent->attr.name, usess->id);
 
 	/*
@@ -3541,7 +3649,7 @@ int ust_app_enable_event_glb(struct ltt_ust_session *usess,
 
 		/* Get event node */
 		ua_event = find_ust_app_event(ua_chan->events, uevent->attr.name,
-				uevent->filter, uevent->attr.loglevel);
+				uevent->filter, uevent->attr.loglevel, uevent->exclusion);
 		if (ua_event == NULL) {
 			DBG3("UST app enable event %s not found for app PID %d."
 					"Skipping app", uevent->attr.name, app->pid);
@@ -3576,7 +3684,7 @@ int ust_app_create_event_glb(struct ltt_ust_session *usess,
 	struct ust_app_session *ua_sess;
 	struct ust_app_channel *ua_chan;
 
-	DBG("UST app creating event %s for all apps for session id %d",
+	DBG("UST app creating event %s for all apps for session id %" PRIu64,
 			uevent->attr.name, usess->id);
 
 	rcu_read_lock();
@@ -3686,6 +3794,13 @@ skip_setup:
 					app->pid, ret);
 		} else {
 			DBG("UST app start session failed. Application is dead.");
+			/*
+			 * This is normal behavior, an application can die during the
+			 * creation process. Don't report an error so the execution can
+			 * continue normally.
+			 */
+			pthread_mutex_unlock(&ua_sess->lock);
+			goto end;
 		}
 		goto error_unlock;
 	}
@@ -3761,6 +3876,12 @@ int ust_app_stop_trace(struct ltt_ust_session *usess, struct ust_app *app)
 					app->pid, ret);
 		} else {
 			DBG("UST app stop session failed. Application is dead.");
+			/*
+			 * This is normal behavior, an application can die during the
+			 * creation process. Don't report an error so the execution can
+			 * continue normally.
+			 */
+			goto end_unlock;
 		}
 		goto error_rcu_unlock;
 	}
@@ -3784,6 +3905,7 @@ int ust_app_stop_trace(struct ltt_ust_session *usess, struct ust_app *app)
 		(void) push_metadata(registry, ua_sess->consumer);
 	}
 
+end_unlock:
 	pthread_mutex_unlock(&ua_sess->lock);
 end_no_session:
 	rcu_read_unlock();
@@ -3838,8 +3960,11 @@ int ust_app_flush_trace(struct ltt_ust_session *usess, struct ust_app *app)
 			} else {
 				DBG3("UST app failed to flush %s. Application is dead.",
 						ua_chan->name);
-				/* No need to continue. */
-				break;
+				/*
+				 * This is normal behavior, an application can die during the
+				 * creation process. Don't report an error so the execution can
+				 * continue normally.
+				 */
 			}
 			/* Continuing flushing all buffers */
 			continue;
@@ -3863,7 +3988,7 @@ static int destroy_trace(struct ltt_ust_session *usess, struct ust_app *app)
 	int ret;
 	struct ust_app_session *ua_sess;
 	struct lttng_ht_iter iter;
-	struct lttng_ht_node_ulong *node;
+	struct lttng_ht_node_u64 *node;
 
 	DBG("Destroy tracing for ust app pid %d", app->pid);
 
@@ -3874,7 +3999,7 @@ static int destroy_trace(struct ltt_ust_session *usess, struct ust_app *app)
 	}
 
 	__lookup_session_by_app(usess, app, &iter);
-	node = lttng_ht_iter_get_node_ulong(&iter);
+	node = lttng_ht_iter_get_node_u64(&iter);
 	if (node == NULL) {
 		/* Session is being or is deleted. */
 		goto end;
@@ -3945,7 +4070,7 @@ int ust_app_stop_trace_all(struct ltt_ust_session *usess)
 		}
 	}
 
-	/* Flush buffers */
+	/* Flush buffers and push metadata (for UID buffers). */
 	switch (usess->buffer_type) {
 	case LTTNG_BUFFER_PER_UID:
 	{
@@ -3953,6 +4078,7 @@ int ust_app_stop_trace_all(struct ltt_ust_session *usess)
 
 		/* Flush all per UID buffers associated to that session. */
 		cds_list_for_each_entry(reg, &usess->buffer_reg_uid_list, lnode) {
+			struct ust_registry_session *ust_session_reg;
 			struct buffer_reg_channel *reg_chan;
 			struct consumer_socket *socket;
 
@@ -3973,7 +4099,14 @@ int ust_app_stop_trace_all(struct ltt_ust_session *usess)
 				 */
 				(void) consumer_flush_channel(socket, reg_chan->consumer_key);
 			}
+
+			ust_session_reg = reg->registry->reg.ust;
+			if (!ust_session_reg->metadata_closed) {
+				/* Push metadata. */
+				(void) push_metadata(ust_session_reg, usess->consumer);
+			}
 		}
+
 		break;
 	}
 	case LTTNG_BUFFER_PER_PID:
@@ -4027,7 +4160,7 @@ int ust_app_destroy_trace_all(struct ltt_ust_session *usess)
 void ust_app_global_update(struct ltt_ust_session *usess, int sock)
 {
 	int ret = 0;
-	struct lttng_ht_iter iter, uiter, iter_ctx;
+	struct lttng_ht_iter iter, uiter;
 	struct ust_app *app;
 	struct ust_app_session *ua_sess = NULL;
 	struct ust_app_channel *ua_chan;
@@ -4037,12 +4170,12 @@ void ust_app_global_update(struct ltt_ust_session *usess, int sock)
 	assert(usess);
 	assert(sock >= 0);
 
-	DBG2("UST app global update for app sock %d for session id %d", sock,
+	DBG2("UST app global update for app sock %d for session id %" PRIu64, sock,
 			usess->id);
 
 	rcu_read_lock();
 
-	app = find_app_by_sock(sock);
+	app = ust_app_find_by_sock(sock);
 	if (app == NULL) {
 		/*
 		 * Application can be unregistered before so this is possible hence
@@ -4099,8 +4232,11 @@ void ust_app_global_update(struct ltt_ust_session *usess, int sock)
 			}
 		}
 
-		cds_lfht_for_each_entry(ua_chan->ctx->ht, &iter_ctx.iter, ua_ctx,
-				node.node) {
+		/*
+		 * Add context using the list so they are enabled in the same order the
+		 * user added them.
+		 */
+		cds_list_for_each_entry(ua_ctx, &ua_chan->ctx_list, list) {
 			ret = create_ust_channel_context(ua_chan, ua_ctx, app);
 			if (ret < 0) {
 				goto error_unlock;
@@ -4239,7 +4375,7 @@ int ust_app_enable_event_pid(struct ltt_ust_session *usess,
 	ua_chan = caa_container_of(ua_chan_node, struct ust_app_channel, node);
 
 	ua_event = find_ust_app_event(ua_chan->events, uevent->attr.name,
-			uevent->filter, uevent->attr.loglevel);
+			uevent->filter, uevent->attr.loglevel, uevent->exclusion);
 	if (ua_event == NULL) {
 		ret = create_ust_app_event(ua_sess, ua_chan, uevent, app);
 		if (ret < 0) {
@@ -4259,69 +4395,6 @@ end:
 	return ret;
 }
 
-/*
- * Disable event for a channel from a UST session for a specific PID.
- */
-int ust_app_disable_event_pid(struct ltt_ust_session *usess,
-		struct ltt_ust_channel *uchan, struct ltt_ust_event *uevent, pid_t pid)
-{
-	int ret = 0;
-	struct lttng_ht_iter iter;
-	struct lttng_ht_node_str *ua_chan_node, *ua_event_node;
-	struct ust_app *app;
-	struct ust_app_session *ua_sess;
-	struct ust_app_channel *ua_chan;
-	struct ust_app_event *ua_event;
-
-	DBG("UST app disabling event %s for PID %d", uevent->attr.name, pid);
-
-	rcu_read_lock();
-
-	app = ust_app_find_by_pid(pid);
-	if (app == NULL) {
-		ERR("UST app disable event per PID %d not found", pid);
-		ret = -1;
-		goto error;
-	}
-
-	if (!app->compatible) {
-		ret = 0;
-		goto error;
-	}
-
-	ua_sess = lookup_session_by_app(usess, app);
-	if (!ua_sess) {
-		/* The application has problem or is probably dead. */
-		goto error;
-	}
-
-	/* Lookup channel in the ust app session */
-	lttng_ht_lookup(ua_sess->channels, (void *)uchan->name, &iter);
-	ua_chan_node = lttng_ht_iter_get_node_str(&iter);
-	if (ua_chan_node == NULL) {
-		/* Channel does not exist, skip disabling */
-		goto error;
-	}
-	ua_chan = caa_container_of(ua_chan_node, struct ust_app_channel, node);
-
-	lttng_ht_lookup(ua_chan->events, (void *)uevent->attr.name, &iter);
-	ua_event_node = lttng_ht_iter_get_node_str(&iter);
-	if (ua_event_node == NULL) {
-		/* Event does not exist, skip disabling */
-		goto error;
-	}
-	ua_event = caa_container_of(ua_event_node, struct ust_app_event, node);
-
-	ret = disable_ust_app_event(ua_sess, ua_event, app);
-	if (ret < 0) {
-		goto error;
-	}
-
-error:
-	rcu_read_unlock();
-	return ret;
-}
-
 /*
  * Calibrate registered applications.
  */
@@ -4473,6 +4546,7 @@ static int reply_ust_register_channel(int sock, int sobjd, int cobjd,
 		DBG("Application socket %d is being teardown. Abort event notify",
 				sock);
 		ret = 0;
+		free(fields);
 		goto error_rcu_unlock;
 	}
 
@@ -4481,6 +4555,7 @@ static int reply_ust_register_channel(int sock, int sobjd, int cobjd,
 	if (!ua_chan) {
 		DBG("Application channel is being teardown. Abort event notify");
 		ret = 0;
+		free(fields);
 		goto error_rcu_unlock;
 	}
 
@@ -4517,6 +4592,9 @@ static int reply_ust_register_channel(int sock, int sobjd, int cobjd,
 	} else {
 		/* Get current already assigned values. */
 		type = chan_reg->header_type;
+		free(fields);
+		/* Set to NULL so the error path does not do a double free. */
+		fields = NULL;
 	}
 	/* Channel id is set during the object creation. */
 	chan_id = chan_reg->chan_id;
@@ -4552,6 +4630,9 @@ error:
 	pthread_mutex_unlock(&registry->lock);
 error_rcu_unlock:
 	rcu_read_unlock();
+	if (ret) {
+		free(fields);
+	}
 	return ret;
 }
 
@@ -4584,6 +4665,9 @@ static int add_event_ust_registry(int sock, int sobjd, int cobjd, char *name,
 		DBG("Application socket %d is being teardown. Abort event notify",
 				sock);
 		ret = 0;
+		free(sig);
+		free(fields);
+		free(model_emf_uri);
 		goto error_rcu_unlock;
 	}
 
@@ -4592,6 +4676,9 @@ static int add_event_ust_registry(int sock, int sobjd, int cobjd, char *name,
 	if (!ua_chan) {
 		DBG("Application channel is being teardown. Abort event notify");
 		ret = 0;
+		free(sig);
+		free(fields);
+		free(model_emf_uri);
 		goto error_rcu_unlock;
 	}
 
@@ -4609,9 +4696,15 @@ static int add_event_ust_registry(int sock, int sobjd, int cobjd, char *name,
 
 	pthread_mutex_lock(&registry->lock);
 
+	/*
+	 * From this point on, this call acquires the ownership of the sig, fields
+	 * and model_emf_uri meaning any free are done inside it if needed. These
+	 * three variables MUST NOT be read/write after this.
+	 */
 	ret_code = ust_registry_create_event(registry, chan_reg_key,
 			sobjd, cobjd, name, sig, nr_fields, fields, loglevel,
-			model_emf_uri, ua_sess->buffer_type, &event_id);
+			model_emf_uri, ua_sess->buffer_type, &event_id,
+			app);
 
 	/*
 	 * The return value is returned to ustctl so in case of an error, the
@@ -4685,7 +4778,12 @@ int ust_app_recv_notify(int sock)
 			goto error;
 		}
 
-		/* Add event to the UST registry coming from the notify socket. */
+		/*
+		 * Add event to the UST registry coming from the notify socket. This
+		 * call will free if needed the sig, fields and model_emf_uri. This
+		 * code path loses the ownsership of these variables and transfer them
+		 * to the this function.
+		 */
 		ret = add_event_ust_registry(sock, sobjd, cobjd, name, sig, nr_fields,
 				fields, loglevel, model_emf_uri);
 		if (ret < 0) {
@@ -4713,6 +4811,11 @@ int ust_app_recv_notify(int sock)
 			goto error;
 		}
 
+		/*
+		 * The fields ownership are transfered to this function call meaning
+		 * that if needed it will be freed. After this, it's invalid to access
+		 * fields or clean it up.
+		 */
 		ret = reply_ust_register_channel(sock, sobjd, cobjd, nr_fields,
 				fields);
 		if (ret < 0) {
@@ -4818,3 +4921,223 @@ void ust_app_destroy(struct ust_app *app)
 
 	call_rcu(&app->pid_n.head, delete_ust_app_rcu);
 }
+
+/*
+ * Take a snapshot for a given UST session. The snapshot is sent to the given
+ * output.
+ *
+ * Return 0 on success or else a negative value.
+ */
+int ust_app_snapshot_record(struct ltt_ust_session *usess,
+		struct snapshot_output *output, int wait, unsigned int nb_streams)
+{
+	int ret = 0;
+	struct lttng_ht_iter iter;
+	struct ust_app *app;
+	char pathname[PATH_MAX];
+	uint64_t max_stream_size = 0;
+
+	assert(usess);
+	assert(output);
+
+	rcu_read_lock();
+
+	/*
+	 * Compute the maximum size of a single stream if a max size is asked by
+	 * the caller.
+	 */
+	if (output->max_size > 0 && nb_streams > 0) {
+		max_stream_size = output->max_size / nb_streams;
+	}
+
+	switch (usess->buffer_type) {
+	case LTTNG_BUFFER_PER_UID:
+	{
+		struct buffer_reg_uid *reg;
+
+		cds_list_for_each_entry(reg, &usess->buffer_reg_uid_list, lnode) {
+			struct buffer_reg_channel *reg_chan;
+			struct consumer_socket *socket;
+
+			/* Get consumer socket to use to push the metadata.*/
+			socket = consumer_find_socket_by_bitness(reg->bits_per_long,
+					usess->consumer);
+			if (!socket) {
+				ret = -EINVAL;
+				goto error;
+			}
+
+			memset(pathname, 0, sizeof(pathname));
+			ret = snprintf(pathname, sizeof(pathname),
+					DEFAULT_UST_TRACE_DIR "/" DEFAULT_UST_TRACE_UID_PATH,
+					reg->uid, reg->bits_per_long);
+			if (ret < 0) {
+				PERROR("snprintf snapshot path");
+				goto error;
+			}
+
+			/* Add the UST default trace dir to path. */
+			cds_lfht_for_each_entry(reg->registry->channels->ht, &iter.iter,
+					reg_chan, node.node) {
+
+				/*
+				 * Make sure the maximum stream size is not lower than the
+				 * subbuffer size or else it's an error since we won't be able to
+				 * snapshot anything.
+				 */
+				if (max_stream_size &&
+						reg_chan->subbuf_size > max_stream_size) {
+					ret = -EINVAL;
+					DBG3("UST app snapshot record maximum stream size %" PRIu64
+							" is smaller than subbuffer size of %zu",
+							max_stream_size, reg_chan->subbuf_size);
+					goto error;
+				}
+				ret = consumer_snapshot_channel(socket, reg_chan->consumer_key, output, 0,
+						usess->uid, usess->gid, pathname, wait,
+						max_stream_size);
+				if (ret < 0) {
+					goto error;
+				}
+			}
+			ret = consumer_snapshot_channel(socket, reg->registry->reg.ust->metadata_key, output,
+					1, usess->uid, usess->gid, pathname, wait,
+					max_stream_size);
+			if (ret < 0) {
+				goto error;
+			}
+		}
+		break;
+	}
+	case LTTNG_BUFFER_PER_PID:
+	{
+		cds_lfht_for_each_entry(ust_app_ht->ht, &iter.iter, app, pid_n.node) {
+			struct consumer_socket *socket;
+			struct lttng_ht_iter chan_iter;
+			struct ust_app_channel *ua_chan;
+			struct ust_app_session *ua_sess;
+			struct ust_registry_session *registry;
+
+			ua_sess = lookup_session_by_app(usess, app);
+			if (!ua_sess) {
+				/* Session not associated with this app. */
+				continue;
+			}
+
+			/* Get the right consumer socket for the application. */
+			socket = consumer_find_socket_by_bitness(app->bits_per_long,
+					output->consumer);
+			if (!socket) {
+				ret = -EINVAL;
+				goto error;
+			}
+
+			/* Add the UST default trace dir to path. */
+			memset(pathname, 0, sizeof(pathname));
+			ret = snprintf(pathname, sizeof(pathname), DEFAULT_UST_TRACE_DIR "/%s",
+					ua_sess->path);
+			if (ret < 0) {
+				PERROR("snprintf snapshot path");
+				goto error;
+			}
+
+			cds_lfht_for_each_entry(ua_sess->channels->ht, &chan_iter.iter,
+					ua_chan, node.node) {
+				/*
+				 * Make sure the maximum stream size is not lower than the
+				 * subbuffer size or else it's an error since we won't be able to
+				 * snapshot anything.
+				 */
+				if (max_stream_size &&
+						ua_chan->attr.subbuf_size > max_stream_size) {
+					ret = -EINVAL;
+					DBG3("UST app snapshot record maximum stream size %" PRIu64
+							" is smaller than subbuffer size of %" PRIu64,
+							max_stream_size, ua_chan->attr.subbuf_size);
+					goto error;
+				}
+
+				ret = consumer_snapshot_channel(socket, ua_chan->key, output, 0,
+						ua_sess->euid, ua_sess->egid, pathname, wait,
+						max_stream_size);
+				if (ret < 0) {
+					goto error;
+				}
+			}
+
+			registry = get_session_registry(ua_sess);
+			assert(registry);
+			ret = consumer_snapshot_channel(socket, registry->metadata_key, output,
+					1, ua_sess->euid, ua_sess->egid, pathname, wait,
+					max_stream_size);
+			if (ret < 0) {
+				goto error;
+			}
+		}
+		break;
+	}
+	default:
+		assert(0);
+		break;
+	}
+
+error:
+	rcu_read_unlock();
+	return ret;
+}
+
+/*
+ * Return the number of streams for a UST session.
+ */
+unsigned int ust_app_get_nb_stream(struct ltt_ust_session *usess)
+{
+	unsigned int ret = 0;
+	struct ust_app *app;
+	struct lttng_ht_iter iter;
+
+	assert(usess);
+
+	switch (usess->buffer_type) {
+	case LTTNG_BUFFER_PER_UID:
+	{
+		struct buffer_reg_uid *reg;
+
+		cds_list_for_each_entry(reg, &usess->buffer_reg_uid_list, lnode) {
+			struct buffer_reg_channel *reg_chan;
+
+			cds_lfht_for_each_entry(reg->registry->channels->ht, &iter.iter,
+					reg_chan, node.node) {
+				ret += reg_chan->stream_count;
+			}
+		}
+		break;
+	}
+	case LTTNG_BUFFER_PER_PID:
+	{
+		rcu_read_lock();
+		cds_lfht_for_each_entry(ust_app_ht->ht, &iter.iter, app, pid_n.node) {
+			struct ust_app_channel *ua_chan;
+			struct ust_app_session *ua_sess;
+			struct lttng_ht_iter chan_iter;
+
+			ua_sess = lookup_session_by_app(usess, app);
+			if (!ua_sess) {
+				/* Session not associated with this app. */
+				continue;
+			}
+
+			cds_lfht_for_each_entry(ua_sess->channels->ht, &chan_iter.iter,
+					ua_chan, node.node) {
+				ret += ua_chan->streams.count;
+			}
+		}
+		rcu_read_unlock();
+		break;
+	}
+	default:
+		assert(0);
+		break;
+	}
+
+	return ret;
+}