X-Git-Url: https://git.lttng.org/?p=lttng-tools.git;a=blobdiff_plain;f=src%2Fbin%2Flttng-sessiond%2Fust-app.c;h=aa188931d7688769bfd81fbf0677a75b031a6092;hp=dd8d103fd1d9c2773fe9f032d1389cedd09f32d3;hb=ffe600149a7608221985751e1bf293234bf2545c;hpb=c617c0c651432f9d5ae7adf4c5c1a5fd92ad828e

diff --git a/src/bin/lttng-sessiond/ust-app.c b/src/bin/lttng-sessiond/ust-app.c
index dd8d103fd..aa188931d 100644
--- a/src/bin/lttng-sessiond/ust-app.c
+++ b/src/bin/lttng-sessiond/ust-app.c
@@ -36,6 +36,48 @@
 #include "ust-consumer.h"
 #include "ust-ctl.h"
 
+/* Next available channel key. */
+static unsigned long next_channel_key;
+
+/*
+ * Return the atomically incremented value of next_channel_key.
+ */
+static inline unsigned long get_next_channel_key(void)
+{
+	return uatomic_add_return(&next_channel_key, 1);
+}
+
+/*
+ * Return the consumer socket from the given consumer output with the right
+ * bitness. On error, returns NULL.
+ *
+ * The caller MUST acquire a rcu read side lock and keep it until the socket
+ * object reference is not needed anymore.
+ */
+static struct consumer_socket *find_consumer_socket_by_bitness(int bits,
+		struct consumer_output *consumer)
+{
+	int consumer_fd;
+	struct consumer_socket *socket = NULL;
+
+	switch (bits) {
+	case 64:
+		consumer_fd = uatomic_read(&ust_consumerd64_fd);
+		break;
+	case 32:
+		consumer_fd = uatomic_read(&ust_consumerd32_fd);
+		break;
+	default:
+		assert(0);
+		goto end;
+	}
+
+	socket = consumer_find_socket(consumer_fd, consumer);
+
+end:
+	return socket;
+}
+
 /*
  * Match function for the hash table lookup.
  *
@@ -127,8 +169,16 @@ static void add_unique_ust_app_event(struct lttng_ht *ht,
 static
 void delete_ust_app_ctx(int sock, struct ust_app_ctx *ua_ctx)
 {
+	int ret;
+
+	assert(ua_ctx);
+
 	if (ua_ctx->obj) {
-		ustctl_release_object(sock, ua_ctx->obj);
+		ret = ustctl_release_object(sock, ua_ctx->obj);
+		if (ret != -EPIPE && ret != -LTTNG_UST_ERR_EXITING) {
+			ERR("UST app sock %d release context obj failed with ret %d",
+					sock, ret);
+		}
 		free(ua_ctx->obj);
 	}
 	free(ua_ctx);
@@ -141,10 +191,18 @@ void delete_ust_app_ctx(int sock, struct ust_app_ctx *ua_ctx)
 static
 void delete_ust_app_event(int sock, struct ust_app_event *ua_event)
 {
+	int ret;
+
+	assert(ua_event);
+
 	free(ua_event->filter);
 
 	if (ua_event->obj != NULL) {
-		ustctl_release_object(sock, ua_event->obj);
+		ret = ustctl_release_object(sock, ua_event->obj);
+		if (ret < 0 && ret != -EPIPE && ret != -LTTNG_UST_ERR_EXITING) {
+			ERR("UST app sock %d release event obj failed with ret %d",
+					sock, ret);
+		}
 		free(ua_event->obj);
 	}
 	free(ua_event);
@@ -155,10 +213,18 @@ void delete_ust_app_event(int sock, struct ust_app_event *ua_event)
  * this function.
  */
 static
-void delete_ust_app_stream(int sock, struct ltt_ust_stream *stream)
+void delete_ust_app_stream(int sock, struct ust_app_stream *stream)
 {
+	int ret;
+
+	assert(stream);
+
 	if (stream->obj) {
-		ustctl_release_object(sock, stream->obj);
+		ret = ustctl_release_object(sock, stream->obj);
+		if (ret < 0 && ret != -EPIPE && ret != -LTTNG_UST_ERR_EXITING) {
+			ERR("UST app sock %d release stream obj failed with ret %d",
+					sock, ret);
+		}
 		lttng_fd_put(LTTNG_FD_APPS, 2);
 		free(stream->obj);
 	}
@@ -176,7 +242,11 @@ void delete_ust_app_channel(int sock, struct ust_app_channel *ua_chan)
 	struct lttng_ht_iter iter;
 	struct ust_app_event *ua_event;
 	struct ust_app_ctx *ua_ctx;
-	struct ltt_ust_stream *stream, *stmp;
+	struct ust_app_stream *stream, *stmp;
+
+	assert(ua_chan);
+
+	DBG3("UST app deleting channel %s", ua_chan->name);
 
 	/* Wipe stream */
 	cds_list_for_each_entry_safe(stream, stmp, &ua_chan->streams.head, list) {
@@ -202,7 +272,11 @@ void delete_ust_app_channel(int sock, struct ust_app_channel *ua_chan)
 	lttng_ht_destroy(ua_chan->events);
 
 	if (ua_chan->obj != NULL) {
-		ustctl_release_object(sock, ua_chan->obj);
+		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",
+					sock, ret);
+		}
 		lttng_fd_put(LTTNG_FD_APPS, 2);
 		free(ua_chan->obj);
 	}
@@ -221,17 +295,7 @@ void delete_ust_app_session(int sock, struct ust_app_session *ua_sess)
 	struct ust_app_channel *ua_chan;
 
 	if (ua_sess->metadata) {
-		if (ua_sess->metadata->stream_obj) {
-			ustctl_release_object(sock, ua_sess->metadata->stream_obj);
-			lttng_fd_put(LTTNG_FD_APPS, 2);
-			free(ua_sess->metadata->stream_obj);
-		}
-		if (ua_sess->metadata->obj) {
-			ustctl_release_object(sock, ua_sess->metadata->obj);
-			lttng_fd_put(LTTNG_FD_APPS, 2);
-			free(ua_sess->metadata->obj);
-		}
-		trace_ust_destroy_metadata(ua_sess->metadata);
+		delete_ust_app_channel(sock, ua_sess->metadata);
 	}
 
 	cds_lfht_for_each_entry(ua_sess->channels->ht, &iter.iter, ua_chan,
@@ -243,7 +307,11 @@ void delete_ust_app_session(int sock, struct ust_app_session *ua_sess)
 	lttng_ht_destroy(ua_sess->channels);
 
 	if (ua_sess->handle != -1) {
-		ustctl_release_handle(sock, ua_sess->handle);
+		ret = ustctl_release_handle(sock, ua_sess->handle);
+		if (ret < 0 && ret != -EPIPE && ret != -LTTNG_UST_ERR_EXITING) {
+			ERR("UST app sock %d release session handle failed with ret %d",
+					sock, ret);
+		}
 	}
 	free(ua_sess);
 }
@@ -313,6 +381,33 @@ void delete_ust_app_rcu(struct rcu_head *head)
 	delete_ust_app(app);
 }
 
+/*
+ * Delete the session from the application ht and delete the data structure by
+ * freeing every object inside and releasing them.
+ */
+static void destroy_session(struct ust_app *app,
+		struct ust_app_session *ua_sess)
+{
+	int ret;
+	struct lttng_ht_iter iter;
+
+	assert(app);
+	assert(ua_sess);
+
+	iter.iter.node = &ua_sess->node.node;
+	ret = lttng_ht_del(app->sessions, &iter);
+	if (ret) {
+		/* Already scheduled for teardown. */
+		goto end;
+	}
+
+	/* Once deleted, free the data structure. */
+	delete_ust_app_session(app->sock, ua_sess);
+
+end:
+	return;
+}
+
 /*
  * Alloc new UST app session.
  */
@@ -325,15 +420,22 @@ struct ust_app_session *alloc_ust_app_session(void)
 	ua_sess = zmalloc(sizeof(struct ust_app_session));
 	if (ua_sess == NULL) {
 		PERROR("malloc");
-		goto error;
+		goto error_free;
 	}
 
 	ua_sess->handle = -1;
 	ua_sess->channels = lttng_ht_new(0, LTTNG_HT_TYPE_STRING);
 
+	if ((lttng_uuid_generate(ua_sess->uuid))) {
+		ERR("Failed to generate UST uuid");
+		goto error;
+	}
+
 	return ua_sess;
 
 error:
+	free(ua_sess);
+error_free:
 	return NULL;
 }
 
@@ -342,7 +444,7 @@ error:
  */
 static
 struct ust_app_channel *alloc_ust_app_channel(char *name,
-		struct lttng_ust_channel *attr)
+		struct lttng_ust_channel_attr *attr)
 {
 	struct ust_app_channel *ua_chan;
 
@@ -359,6 +461,7 @@ struct ust_app_channel *alloc_ust_app_channel(char *name,
 
 	ua_chan->enabled = 1;
 	ua_chan->handle = -1;
+	ua_chan->key = get_next_channel_key();
 	ua_chan->ctx = lttng_ht_new(0, LTTNG_HT_TYPE_ULONG);
 	ua_chan->events = lttng_ht_new(0, LTTNG_HT_TYPE_STRING);
 	lttng_ht_node_init_str(&ua_chan->node, ua_chan->name);
@@ -367,8 +470,16 @@ struct ust_app_channel *alloc_ust_app_channel(char *name,
 
 	/* Copy attributes */
 	if (attr) {
-		memcpy(&ua_chan->attr, attr, sizeof(ua_chan->attr));
+		/* Translate from lttng_ust_channel to ustctl_consumer_channel_attr. */
+		ua_chan->attr.subbuf_size = attr->subbuf_size;
+		ua_chan->attr.num_subbuf = attr->num_subbuf;
+		ua_chan->attr.overwrite = attr->overwrite;
+		ua_chan->attr.switch_timer_interval = attr->switch_timer_interval;
+		ua_chan->attr.read_timer_interval = attr->read_timer_interval;
+		ua_chan->attr.output = attr->output;
 	}
+	/* By default, the channel is a per cpu channel. */
+	ua_chan->attr.type = LTTNG_UST_CHAN_PER_CPU;
 
 	DBG3("UST app channel %s allocated", ua_chan->name);
 
@@ -378,6 +489,28 @@ error:
 	return NULL;
 }
 
+/*
+ * Allocate and initialize a UST app stream.
+ *
+ * Return newly allocated stream pointer or NULL on error.
+ */
+struct ust_app_stream *ust_app_alloc_stream(void)
+{
+	struct ust_app_stream *stream = NULL;
+
+	stream = zmalloc(sizeof(*stream));
+	if (stream == NULL) {
+		PERROR("zmalloc ust app stream");
+		goto error;
+	}
+
+	/* Zero could be a valid value for a handle so flag it to -1. */
+	stream->handle = -1;
+
+error:
+	return stream;
+}
+
 /*
  * Alloc new UST app event.
  */
@@ -526,11 +659,17 @@ int create_ust_channel_context(struct ust_app_channel *ua_chan,
 {
 	int ret;
 
-	health_code_update(&health_thread_cmd);
+	health_code_update();
 
 	ret = ustctl_add_context(app->sock, &ua_ctx->ctx,
 			ua_chan->obj, &ua_ctx->obj);
 	if (ret < 0) {
+		if (ret != -EPIPE && ret != -LTTNG_UST_ERR_EXITING) {
+			ERR("UST app create channel context failed for app (pid: %d) "
+					"with ret %d", app->pid, ret);
+		} else {
+			DBG3("UST app disable event failed. Application is dead.");
+		}
 		goto error;
 	}
 
@@ -539,7 +678,7 @@ int create_ust_channel_context(struct ust_app_channel *ua_chan,
 	DBG2("UST app context created successfully for channel %s", ua_chan->name);
 
 error:
-	health_code_update(&health_thread_cmd);
+	health_code_update();
 	return ret;
 }
 
@@ -552,7 +691,7 @@ int set_ust_event_filter(struct ust_app_event *ua_event,
 {
 	int ret;
 
-	health_code_update(&health_thread_cmd);
+	health_code_update();
 
 	if (!ua_event->filter) {
 		ret = 0;
@@ -562,13 +701,19 @@ int set_ust_event_filter(struct ust_app_event *ua_event,
 	ret = ustctl_set_filter(app->sock, ua_event->filter,
 			ua_event->obj);
 	if (ret < 0) {
+		if (ret != -EPIPE && ret != -LTTNG_UST_ERR_EXITING) {
+			ERR("UST app event %s filter failed for app (pid: %d) "
+					"with ret %d", ua_event->attr.name, app->pid, ret);
+		} else {
+			DBG3("UST app filter event failed. Application is dead.");
+		}
 		goto error;
 	}
 
 	DBG2("UST filter set successfully for event %s", ua_event->name);
 
 error:
-	health_code_update(&health_thread_cmd);
+	health_code_update();
 	return ret;
 }
 
@@ -580,13 +725,17 @@ static int disable_ust_event(struct ust_app *app,
 {
 	int ret;
 
-	health_code_update(&health_thread_cmd);
+	health_code_update();
 
 	ret = ustctl_disable(app->sock, ua_event->obj);
 	if (ret < 0) {
-		ERR("UST app event %s disable failed for app (pid: %d) "
-				"and session handle %d with ret %d",
-				ua_event->attr.name, app->pid, ua_sess->handle, ret);
+		if (ret != -EPIPE && ret != -LTTNG_UST_ERR_EXITING) {
+			ERR("UST app event %s disable failed for app (pid: %d) "
+					"and session handle %d with ret %d",
+					ua_event->attr.name, app->pid, ua_sess->handle, ret);
+		} else {
+			DBG3("UST app disable event failed. Application is dead.");
+		}
 		goto error;
 	}
 
@@ -594,7 +743,7 @@ static int disable_ust_event(struct ust_app *app,
 			ua_event->attr.name, app->pid);
 
 error:
-	health_code_update(&health_thread_cmd);
+	health_code_update();
 	return ret;
 }
 
@@ -606,13 +755,17 @@ static int disable_ust_channel(struct ust_app *app,
 {
 	int ret;
 
-	health_code_update(&health_thread_cmd);
+	health_code_update();
 
 	ret = ustctl_disable(app->sock, ua_chan->obj);
 	if (ret < 0) {
-		ERR("UST app channel %s disable failed for app (pid: %d) "
-				"and session handle %d with ret %d",
-				ua_chan->name, app->pid, ua_sess->handle, ret);
+		if (ret != -EPIPE && ret != -LTTNG_UST_ERR_EXITING) {
+			ERR("UST app channel %s disable failed for app (pid: %d) "
+					"and session handle %d with ret %d",
+					ua_chan->name, app->pid, ua_sess->handle, ret);
+		} else {
+			DBG3("UST app disable channel failed. Application is dead.");
+		}
 		goto error;
 	}
 
@@ -620,7 +773,7 @@ static int disable_ust_channel(struct ust_app *app,
 			ua_chan->name, app->pid);
 
 error:
-	health_code_update(&health_thread_cmd);
+	health_code_update();
 	return ret;
 }
 
@@ -632,13 +785,17 @@ static int enable_ust_channel(struct ust_app *app,
 {
 	int ret;
 
-	health_code_update(&health_thread_cmd);
+	health_code_update();
 
 	ret = ustctl_enable(app->sock, ua_chan->obj);
 	if (ret < 0) {
-		ERR("UST app channel %s enable failed for app (pid: %d) "
-				"and session handle %d with ret %d",
-				ua_chan->name, app->pid, ua_sess->handle, ret);
+		if (ret != -EPIPE && ret != -LTTNG_UST_ERR_EXITING) {
+			ERR("UST app channel %s enable failed for app (pid: %d) "
+					"and session handle %d with ret %d",
+					ua_chan->name, app->pid, ua_sess->handle, ret);
+		} else {
+			DBG3("UST app enable channel failed. Application is dead.");
+		}
 		goto error;
 	}
 
@@ -648,7 +805,7 @@ static int enable_ust_channel(struct ust_app *app,
 			ua_chan->name, app->pid);
 
 error:
-	health_code_update(&health_thread_cmd);
+	health_code_update();
 	return ret;
 }
 
@@ -660,13 +817,17 @@ static int enable_ust_event(struct ust_app *app,
 {
 	int ret;
 
-	health_code_update(&health_thread_cmd);
+	health_code_update();
 
 	ret = ustctl_enable(app->sock, ua_event->obj);
 	if (ret < 0) {
-		ERR("UST app event %s enable failed for app (pid: %d) "
-				"and session handle %d with ret %d",
-				ua_event->attr.name, app->pid, ua_sess->handle, ret);
+		if (ret != -EPIPE && ret != -LTTNG_UST_ERR_EXITING) {
+			ERR("UST app event %s enable failed for app (pid: %d) "
+					"and session handle %d with ret %d",
+					ua_event->attr.name, app->pid, ua_sess->handle, ret);
+		} else {
+			DBG3("UST app enable event failed. Application is dead.");
+		}
 		goto error;
 	}
 
@@ -674,118 +835,94 @@ static int enable_ust_event(struct ust_app *app,
 			ua_event->attr.name, app->pid);
 
 error:
-	health_code_update(&health_thread_cmd);
+	health_code_update();
 	return ret;
 }
 
 /*
- * Open metadata onto the UST tracer for a UST session.
+ * Create the specified channel onto the UST tracer for a UST session.
+ *
+ * Return 0 on success. On error, a negative value is returned.
  */
-static int open_ust_metadata(struct ust_app *app,
-		struct ust_app_session *ua_sess)
+static int create_ust_channel(struct ust_app *app,
+		struct ust_app_session *ua_sess, struct ust_app_channel *ua_chan,
+		struct consumer_output *consumer)
 {
 	int ret;
-	struct lttng_ust_channel_attr uattr;
+	unsigned int nb_fd = 0;
+	struct consumer_socket *socket;
+	struct ust_app_stream *stream, *stmp;
 
-	health_code_update(&health_thread_cmd);
+	assert(app);
+	assert(ua_sess);
+	assert(ua_chan);
+	assert(consumer);
 
-	uattr.overwrite = ua_sess->metadata->attr.overwrite;
-	uattr.subbuf_size = ua_sess->metadata->attr.subbuf_size;
-	uattr.num_subbuf = ua_sess->metadata->attr.num_subbuf;
-	uattr.switch_timer_interval =
-		ua_sess->metadata->attr.switch_timer_interval;
-	uattr.read_timer_interval =
-		ua_sess->metadata->attr.read_timer_interval;
-	uattr.output = ua_sess->metadata->attr.output;
+	health_code_update();
 
-	/* We are going to receive 2 fds, we need to reserve them. */
-	ret = lttng_fd_get(LTTNG_FD_APPS, 2);
-	if (ret < 0) {
-		ERR("Exhausted number of available FD upon metadata open");
-		goto error;
-	}
-	/* UST tracer metadata creation */
-	ret = ustctl_open_metadata(app->sock, ua_sess->handle, &uattr,
-			&ua_sess->metadata->obj);
-	if (ret < 0) {
-		ERR("UST app open metadata failed for app pid:%d with ret %d",
-				app->pid, ret);
+	/* Get the right consumer socket for the application. */
+	socket = find_consumer_socket_by_bitness(app->bits_per_long, consumer);
+	if (!socket) {
+		ret = -1;
 		goto error;
 	}
 
-	ua_sess->metadata->handle = ua_sess->metadata->obj->handle;
-
-error:
-	health_code_update(&health_thread_cmd);
-	return ret;
-}
-
-/*
- * Create stream onto the UST tracer for a UST session.
- */
-static int create_ust_stream(struct ust_app *app,
-		struct ust_app_session *ua_sess)
-{
-	int ret;
-
-	health_code_update(&health_thread_cmd);
+	health_code_update();
 
-	/* We are going to receive 2 fds, we need to reserve them. */
-	ret = lttng_fd_get(LTTNG_FD_APPS, 2);
-	if (ret < 0) {
-		ERR("Exhausted number of available FD upon metadata stream create");
-		goto error;
-	}
-	ret = ustctl_create_stream(app->sock, ua_sess->metadata->obj,
-			&ua_sess->metadata->stream_obj);
+	/*
+	 * Ask consumer to create channel. The consumer will return the number of
+	 * stream we have to expect.
+	 */
+	ret = ust_consumer_ask_channel(ua_sess, ua_chan, consumer, socket);
 	if (ret < 0) {
-		ERR("UST create metadata stream failed");
 		goto error;
 	}
 
-error:
-	health_code_update(&health_thread_cmd);
-	return ret;
-}
-
-/*
- * Create the specified channel onto the UST tracer for a UST session.
- */
-static int create_ust_channel(struct ust_app *app,
-		struct ust_app_session *ua_sess, struct ust_app_channel *ua_chan)
-{
-	int ret;
-
-	health_code_update(&health_thread_cmd);
-
-	/* TODO: remove cast and use lttng-ust-abi.h */
+	/*
+	 * Compute the number of fd needed before receiving them. It must be 2 per
+	 * stream.
+	 */
+	nb_fd = DEFAULT_UST_STREAM_FD_NUM * ua_chan->expected_stream_count;
 
-	/* We are going to receive 2 fds, we need to reserve them. */
-	ret = lttng_fd_get(LTTNG_FD_APPS, 2);
+	/* Reserve the amount of file descriptor we need. */
+	ret = lttng_fd_get(LTTNG_FD_APPS, nb_fd);
 	if (ret < 0) {
 		ERR("Exhausted number of available FD upon create channel");
-		goto error;
+		goto error_fd_get;
 	}
 
-	health_code_update(&health_thread_cmd);
+	health_code_update();
 
-	ret = ustctl_create_channel(app->sock, ua_sess->handle,
-			(struct lttng_ust_channel_attr *)&ua_chan->attr, &ua_chan->obj);
+	/*
+	 * Now get the channel from the consumer. This call wil populate the stream
+	 * list of that channel and set the ust object.
+	 */
+	ret = ust_consumer_get_channel(socket, ua_chan);
+	if (ret < 0) {
+		goto error_destroy;
+	}
+
+	/* Send channel to the application. */
+	ret = ust_consumer_send_channel_to_ust(app, ua_sess, ua_chan);
 	if (ret < 0) {
-		ERR("Creating channel %s for app (pid: %d, sock: %d) "
-				"and session handle %d with ret %d",
-				ua_chan->name, app->pid, app->sock,
-				ua_sess->handle, ret);
-		lttng_fd_put(LTTNG_FD_APPS, 2);
 		goto error;
 	}
 
-	ua_chan->handle = ua_chan->obj->handle;
+	/* Send all streams to application. */
+	cds_list_for_each_entry_safe(stream, stmp, &ua_chan->streams.head, list) {
+		ret = ust_consumer_send_stream_to_ust(app, ua_chan, stream);
+		if (ret < 0) {
+			goto error;
+		}
+		/* We don't need the stream anymore once sent to the tracer. */
+		cds_list_del(&stream->list);
+		delete_ust_app_stream(-1, stream);
+	}
 
-	DBG2("UST app channel %s created successfully for pid:%d and sock:%d",
-			ua_chan->name, app->pid, app->sock);
+	/* Flag the channel that it is sent to the application. */
+	ua_chan->is_sent = 1;
 
-	health_code_update(&health_thread_cmd);
+	health_code_update();
 
 	/* If channel is not enabled, disable it on the tracer */
 	if (!ua_chan->enabled) {
@@ -795,8 +932,20 @@ static int create_ust_channel(struct ust_app *app,
 		}
 	}
 
+	return 0;
+
+error_destroy:
+	lttng_fd_put(LTTNG_FD_APPS, nb_fd);
+error_fd_get:
+	/*
+	 * Initiate a destroy channel on the consumer since we had an error
+	 * handling it on our side. The return value is of no importance since we
+	 * already have a ret value set by the previous error that we need to
+	 * return.
+	 */
+	(void) ust_consumer_destroy_channel(socket, ua_chan);
 error:
-	health_code_update(&health_thread_cmd);
+	health_code_update();
 	return ret;
 }
 
@@ -809,14 +958,18 @@ int create_ust_event(struct ust_app *app, struct ust_app_session *ua_sess,
 {
 	int ret = 0;
 
-	health_code_update(&health_thread_cmd);
+	health_code_update();
 
 	/* Create UST event on tracer */
 	ret = ustctl_create_event(app->sock, &ua_event->attr, ua_chan->obj,
 			&ua_event->obj);
 	if (ret < 0) {
-		ERR("Error ustctl create event %s for app pid: %d with ret %d",
-				ua_event->attr.name, app->pid, ret);
+		if (ret != -EPIPE && ret != -LTTNG_UST_ERR_EXITING) {
+			ERR("Error ustctl create event %s for app pid: %d with ret %d",
+					ua_event->attr.name, app->pid, ret);
+		} else {
+			DBG3("UST app create event failed. Application is dead.");
+		}
 		goto error;
 	}
 
@@ -825,7 +978,7 @@ int create_ust_event(struct ust_app *app, struct ust_app_session *ua_sess,
 	DBG2("UST app event %s created successfully for pid:%d",
 			ua_event->attr.name, app->pid);
 
-	health_code_update(&health_thread_cmd);
+	health_code_update();
 
 	/* Set filter if one is present. */
 	if (ua_event->filter) {
@@ -860,7 +1013,7 @@ int create_ust_event(struct ust_app *app, struct ust_app_session *ua_sess,
 	}
 
 error:
-	health_code_update(&health_thread_cmd);
+	health_code_update();
 	return ret;
 }
 
@@ -901,8 +1054,18 @@ static void shadow_copy_channel(struct ust_app_channel *ua_chan,
 
 	strncpy(ua_chan->name, uchan->name, sizeof(ua_chan->name));
 	ua_chan->name[sizeof(ua_chan->name) - 1] = '\0';
-	/* Copy event attributes */
-	memcpy(&ua_chan->attr, &uchan->attr, sizeof(ua_chan->attr));
+
+	/* Copy event attributes since the layout is different. */
+	ua_chan->attr.subbuf_size = uchan->attr.subbuf_size;
+	ua_chan->attr.num_subbuf = uchan->attr.num_subbuf;
+	ua_chan->attr.overwrite = uchan->attr.overwrite;
+	ua_chan->attr.switch_timer_interval = uchan->attr.switch_timer_interval;
+	ua_chan->attr.read_timer_interval = uchan->attr.read_timer_interval;
+	ua_chan->attr.output = uchan->attr.output;
+	/*
+	 * Note that the attribute channel type is not set since the channel on the
+	 * tracing registry side does not have this information.
+	 */
 
 	ua_chan->enabled = uchan->enabled;
 
@@ -990,8 +1153,14 @@ static void shadow_copy_session(struct ust_app_session *ua_sess,
 			/* malloc failed FIXME: Might want to do handle ENOMEM .. */
 			continue;
 		}
-
 		shadow_copy_channel(ua_chan, uchan);
+		/*
+		 * The concept of metadata channel does not exist on the tracing
+		 * registry side of the session daemon so this can only be a per CPU
+		 * channel and not metadata.
+		 */
+		ua_chan->attr.type = LTTNG_UST_CHAN_PER_CPU;
+
 		lttng_ht_add_unique_str(ua_sess->channels, &ua_chan->node);
 	}
 }
@@ -1030,17 +1199,28 @@ error:
 }
 
 /*
- * Create a UST session onto the tracer of app and add it the session
- * hashtable.
+ * Create a session on the tracer side for the given app.
  *
- * Return ust app session or NULL on error.
+ * On success, ua_sess_ptr is populated with the session pointer or else left
+ * untouched. If the session was created, is_created is set to 1. On error,
+ * it's left untouched. Note that ua_sess_ptr is mandatory but is_created can
+ * be NULL.
+ *
+ * Returns 0 on success or else a negative code which is either -ENOMEM or
+ * -ENOTCONN which is the default code if the ustctl_create_session fails.
  */
-static struct ust_app_session *create_ust_app_session(
-		struct ltt_ust_session *usess, struct ust_app *app)
+static int create_ust_app_session(struct ltt_ust_session *usess,
+		struct ust_app *app, struct ust_app_session **ua_sess_ptr,
+		int *is_created)
 {
+	int ret, created = 0;
 	struct ust_app_session *ua_sess;
 
-	health_code_update(&health_thread_cmd);
+	assert(usess);
+	assert(app);
+	assert(ua_sess_ptr);
+
+	health_code_update();
 
 	ua_sess = lookup_session_by_app(usess, app);
 	if (ua_sess == NULL) {
@@ -1049,23 +1229,33 @@ static struct ust_app_session *create_ust_app_session(
 		ua_sess = alloc_ust_app_session();
 		if (ua_sess == NULL) {
 			/* Only malloc can failed so something is really wrong */
-			goto end;
+			ret = -ENOMEM;
+			goto error;
 		}
 		shadow_copy_session(ua_sess, usess, app);
+		created = 1;
 	}
 
-	health_code_update(&health_thread_cmd);
+	health_code_update();
 
 	if (ua_sess->handle == -1) {
-		int ret;
-
 		ret = ustctl_create_session(app->sock);
 		if (ret < 0) {
-			ERR("Creating session for app pid %d", app->pid);
+			if (ret != -EPIPE && ret != -LTTNG_UST_ERR_EXITING) {
+				ERR("Creating session for app pid %d with ret %d",
+						app->pid, ret);
+			} else {
+				DBG("UST app creating session failed. Application is dead");
+			}
 			delete_ust_app_session(-1, ua_sess);
-			/* This means that the tracer is gone... */
-			ua_sess = (void*) -1UL;
-			goto end;
+			if (ret != -ENOMEM) {
+				/*
+				 * Tracer is probably gone or got an internal error so let's
+				 * behave like it will soon unregister or not usable.
+				 */
+				ret = -ENOTCONN;
+			}
+			goto error;
 		}
 
 		ua_sess->handle = ret;
@@ -1077,9 +1267,16 @@ static struct ust_app_session *create_ust_app_session(
 		DBG2("UST app session created successfully with handle %d", ret);
 	}
 
-end:
-	health_code_update(&health_thread_cmd);
-	return ua_sess;
+	*ua_sess_ptr = ua_sess;
+	if (is_created) {
+		*is_created = created;
+	}
+	/* Everything went well. */
+	ret = 0;
+
+error:
+	health_code_update();
+	return ret;
 }
 
 /*
@@ -1218,6 +1415,7 @@ error:
  */
 static int create_ust_app_channel(struct ust_app_session *ua_sess,
 		struct ltt_ust_channel *uchan, struct ust_app *app,
+		struct consumer_output *consumer, enum lttng_ust_chan_type type,
 		struct ust_app_channel **ua_chanp)
 {
 	int ret = 0;
@@ -1241,10 +1439,11 @@ static int create_ust_app_channel(struct ust_app_session *ua_sess,
 	}
 	shadow_copy_channel(ua_chan, uchan);
 
-	ret = create_ust_channel(app, ua_sess, ua_chan);
+	/* Set channel type. */
+	ua_chan->attr.type = type;
+
+	ret = create_ust_channel(app, ua_sess, ua_chan, consumer);
 	if (ret < 0) {
-		/* Not found previously means that it does not exist on the tracer */
-		assert(ret != -LTTNG_UST_ERR_EXIST);
 		goto error;
 	}
 
@@ -1263,7 +1462,7 @@ end:
 	return 0;
 
 error:
-	delete_ust_app_channel(-1, ua_chan);
+	delete_ust_app_channel(ua_chan->is_sent ? app->sock : -1, ua_chan);
 	return ret;
 }
 
@@ -1321,60 +1520,51 @@ error:
  * Create UST metadata and open it on the tracer side.
  */
 static int create_ust_app_metadata(struct ust_app_session *ua_sess,
-		char *pathname, struct ust_app *app)
+		struct ust_app *app, struct consumer_output *consumer)
 {
 	int ret = 0;
+	struct ust_app_channel *metadata;
 
-	if (ua_sess->metadata == NULL) {
-		/* Allocate UST metadata */
-		ua_sess->metadata = trace_ust_create_metadata(pathname);
-		if (ua_sess->metadata == NULL) {
-			/* malloc() failed */
-			goto error;
-		}
-
-		ret = open_ust_metadata(app, ua_sess);
-		if (ret < 0) {
-			DBG3("Opening metadata failed. Cleaning up memory");
-
-			/* Cleanup failed metadata struct */
-			free(ua_sess->metadata);
-			/*
-			 * This is very important because delete_ust_app_session check if
-			 * the pointer is null or not in order to delete the metadata.
-			 */
-			ua_sess->metadata = NULL;
-			goto error;
-		}
+	assert(ua_sess);
+	assert(app);
 
-		DBG2("UST metadata opened for app pid %d", app->pid);
+	if (ua_sess->metadata) {
+		/* Already exist. Return success. */
+		goto end;
 	}
 
-	/* Open UST metadata stream */
-	if (ua_sess->metadata->stream_obj == NULL) {
-		ret = create_ust_stream(app, ua_sess);
-		if (ret < 0) {
-			goto error;
-		}
+	/* Allocate UST metadata */
+	metadata = alloc_ust_app_channel(DEFAULT_METADATA_NAME, NULL);
+	if (!metadata) {
+		/* malloc() failed */
+		ret = -ENOMEM;
+		goto error;
+	}
 
-		ret = snprintf(ua_sess->metadata->pathname, PATH_MAX,
-				"%s/metadata", ua_sess->path);
-		if (ret < 0) {
-			PERROR("asprintf UST create stream");
-			goto error;
-		}
+	/* Set default attributes for metadata. */
+	metadata->attr.overwrite = DEFAULT_CHANNEL_OVERWRITE;
+	metadata->attr.subbuf_size = default_get_metadata_subbuf_size();
+	metadata->attr.num_subbuf = DEFAULT_METADATA_SUBBUF_NUM;
+	metadata->attr.switch_timer_interval = DEFAULT_CHANNEL_SWITCH_TIMER;
+	metadata->attr.read_timer_interval = DEFAULT_CHANNEL_READ_TIMER;
+	metadata->attr.output = LTTNG_UST_MMAP;
+	metadata->attr.type = LTTNG_UST_CHAN_METADATA;
 
-		DBG2("UST metadata stream object created for app pid %d",
-				app->pid);
-	} else {
-		ERR("Attempting to create stream without metadata opened");
-		goto error;
+	ret = create_ust_channel(app, ua_sess, metadata, consumer);
+	if (ret < 0) {
+		goto error_create;
 	}
 
-	return 0;
+	ua_sess->metadata = metadata;
 
+	DBG2("UST metadata opened for app pid %d", app->pid);
+
+end:
+	return 0;
+error_create:
+	delete_ust_app_channel(metadata->is_sent ? app->sock : -1, metadata);
 error:
-	return -1;
+	return ret;
 }
 
 /*
@@ -1604,7 +1794,7 @@ int ust_app_list_events(struct lttng_event **events)
 	cds_lfht_for_each_entry(ust_app_ht->ht, &iter.iter, app, pid_n.node) {
 		struct lttng_ust_tracepoint_iter uiter;
 
-		health_code_update(&health_thread_cmd);
+		health_code_update();
 
 		if (!app->compatible) {
 			/*
@@ -1615,14 +1805,28 @@ int ust_app_list_events(struct lttng_event **events)
 		}
 		handle = ustctl_tracepoint_list(app->sock);
 		if (handle < 0) {
-			ERR("UST app list events getting handle failed for app pid %d",
-					app->pid);
+			if (handle != -EPIPE && handle != -LTTNG_UST_ERR_EXITING) {
+				ERR("UST app list events getting handle failed for app pid %d",
+						app->pid);
+			}
 			continue;
 		}
 
 		while ((ret = ustctl_tracepoint_list_get(app->sock, handle,
 					&uiter)) != -LTTNG_UST_ERR_NOENT) {
-			health_code_update(&health_thread_cmd);
+			/* Handle ustctl error. */
+			if (ret < 0) {
+				free(tmp_event);
+				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");
+				}
+				goto rcu_error;
+			}
+
+			health_code_update();
 			if (count >= nbmem) {
 				/* In case the realloc fails, we free the memory */
 				void *ptr;
@@ -1656,7 +1860,7 @@ int ust_app_list_events(struct lttng_event **events)
 rcu_error:
 	rcu_read_unlock();
 error:
-	health_code_update(&health_thread_cmd);
+	health_code_update();
 	return ret;
 }
 
@@ -1684,7 +1888,7 @@ int ust_app_list_event_fields(struct lttng_event_field **fields)
 	cds_lfht_for_each_entry(ust_app_ht->ht, &iter.iter, app, pid_n.node) {
 		struct lttng_ust_field_iter uiter;
 
-		health_code_update(&health_thread_cmd);
+		health_code_update();
 
 		if (!app->compatible) {
 			/*
@@ -1695,14 +1899,28 @@ int ust_app_list_event_fields(struct lttng_event_field **fields)
 		}
 		handle = ustctl_tracepoint_field_list(app->sock);
 		if (handle < 0) {
-			ERR("UST app list event fields getting handle failed for app pid %d",
-					app->pid);
+			if (handle != -EPIPE && handle != -LTTNG_UST_ERR_EXITING) {
+				ERR("UST app list field getting handle failed for app pid %d",
+						app->pid);
+			}
 			continue;
 		}
 
 		while ((ret = ustctl_tracepoint_field_list_get(app->sock, handle,
 					&uiter)) != -LTTNG_UST_ERR_NOENT) {
-			health_code_update(&health_thread_cmd);
+			/* Handle ustctl error. */
+			if (ret < 0) {
+				free(tmp_event);
+				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");
+				}
+				goto rcu_error;
+			}
+
+			health_code_update();
 			if (count >= nbmem) {
 				/* In case the realloc fails, we free the memory */
 				void *ptr;
@@ -1741,7 +1959,7 @@ int ust_app_list_event_fields(struct lttng_event_field **fields)
 rcu_error:
 	rcu_read_unlock();
 error:
-	health_code_update(&health_thread_cmd);
+	health_code_update();
 	return ret;
 }
 
@@ -2030,10 +2248,10 @@ int ust_app_disable_all_event_glb(struct ltt_ust_session *usess,
 int ust_app_create_channel_glb(struct ltt_ust_session *usess,
 		struct ltt_ust_channel *uchan)
 {
-	int ret = 0;
+	int ret = 0, created;
 	struct lttng_ht_iter iter;
 	struct ust_app *app;
-	struct ust_app_session *ua_sess;
+	struct ust_app_session *ua_sess = NULL;
 
 	/* Very wrong code flow */
 	assert(usess);
@@ -2058,25 +2276,35 @@ int ust_app_create_channel_glb(struct ltt_ust_session *usess,
 		 * that if session exist, it will simply return a pointer to the ust
 		 * app session.
 		 */
-		ua_sess = create_ust_app_session(usess, app);
-		if (ua_sess == NULL) {
-			/* The malloc() failed. */
-			ret = -ENOMEM;
-			goto error_rcu_unlock;
-		} else if (ua_sess == (void *) -1UL) {
-			/*
-			 * The application's socket is not valid. Either a bad socket or a
-			 * timeout on it. We can't inform yet the caller that for a
-			 * specific app, the session failed so we continue here.
-			 */
-			continue;
+		ret = create_ust_app_session(usess, app, &ua_sess, &created);
+		if (ret < 0) {
+			switch (ret) {
+			case -ENOTCONN:
+				/*
+				 * The application's socket is not valid. Either a bad socket
+				 * or a timeout on it. We can't inform the caller that for a
+				 * specific app, the session failed so lets continue here.
+				 */
+				continue;
+			case -ENOMEM:
+			default:
+				goto error_rcu_unlock;
+			}
 		}
+		assert(ua_sess);
 
 		/* Create channel onto application. We don't need the chan ref. */
-		ret = create_ust_app_channel(ua_sess, uchan, app, NULL);
-		if (ret < 0 && ret == -ENOMEM) {
-			/* No more memory is a fatal error. Stop right now. */
-			goto error_rcu_unlock;
+		ret = create_ust_app_channel(ua_sess, uchan, app, usess->consumer,
+				LTTNG_UST_CHAN_PER_CPU, NULL);
+		if (ret < 0) {
+			if (ret == -ENOMEM) {
+				/* No more memory is a fatal error. Stop right now. */
+				goto error_rcu_unlock;
+			}
+			/* Cleanup the created session if it's the case. */
+			if (created) {
+				destroy_session(app, ua_sess);
+			}
 		}
 	}
 
@@ -2218,11 +2446,7 @@ int ust_app_create_event_glb(struct ltt_ust_session *usess,
 int ust_app_start_trace(struct ltt_ust_session *usess, struct ust_app *app)
 {
 	int ret = 0;
-	struct lttng_ht_iter iter;
 	struct ust_app_session *ua_sess;
-	struct ust_app_channel *ua_chan;
-	struct ltt_ust_stream *ustream;
-	struct consumer_socket *socket;
 
 	DBG("Starting tracing for ust app pid %d", app->pid);
 
@@ -2251,125 +2475,52 @@ int ust_app_start_trace(struct ltt_ust_session *usess, struct ust_app *app)
 		if (ret < 0) {
 			if (ret != -EEXIST) {
 				ERR("Trace directory creation error");
-				ret = -1;
 				goto error_rcu_unlock;
 			}
 		}
 	}
 
-	ret = create_ust_app_metadata(ua_sess, usess->pathname, app);
+	/* Create the metadata for the application. */
+	ret = create_ust_app_metadata(ua_sess, app, usess->consumer);
 	if (ret < 0) {
-		ret = LTTNG_ERR_UST_META_FAIL;
 		goto error_rcu_unlock;
 	}
 
-	/* For each channel */
-	cds_lfht_for_each_entry(ua_sess->channels->ht, &iter.iter, ua_chan,
-			node.node) {
-		/* Create all streams */
-		while (1) {
-			/* Create UST stream */
-			ustream = zmalloc(sizeof(*ustream));
-			if (ustream == NULL) {
-				PERROR("zmalloc ust stream");
-				goto error_rcu_unlock;
-			}
-
-			/* We are going to receive 2 fds, we need to reserve them. */
-			ret = lttng_fd_get(LTTNG_FD_APPS, 2);
-			if (ret < 0) {
-				ERR("Exhausted number of available FD upon stream create");
-				free(ustream);
-				goto error_rcu_unlock;
-			}
-
-			health_code_update(&health_thread_cmd);
-
-			ret = ustctl_create_stream(app->sock, ua_chan->obj,
-					&ustream->obj);
-			if (ret < 0) {
-				/* Got all streams */
-				lttng_fd_put(LTTNG_FD_APPS, 2);
-				free(ustream);
-				ret = LTTNG_ERR_UST_STREAM_FAIL;
-				break;
-			}
-			ustream->handle = ustream->obj->handle;
-
-			health_code_update(&health_thread_cmd);
-
-			/* Order is important */
-			cds_list_add_tail(&ustream->list, &ua_chan->streams.head);
-			ret = snprintf(ustream->name, sizeof(ustream->name), "%s_%u",
-					ua_chan->name, ua_chan->streams.count);
-			ua_chan->streams.count++;
-			if (ret < 0) {
-				PERROR("asprintf UST create stream");
-				/*
-				 * XXX what should we do here with the
-				 * stream ?
-				 */
-				continue;
-			}
-			DBG2("UST stream %d ready (handle: %d)", ua_chan->streams.count,
-					ustream->handle);
-		}
-
-		health_code_update(&health_thread_cmd);
-	}
-
-	switch (app->bits_per_long) {
-	case 64:
-		socket = consumer_find_socket(uatomic_read(&ust_consumerd64_fd),
-				usess->consumer);
-		if (socket == NULL) {
-			goto skip_setup;
-		}
-		break;
-	case 32:
-		socket = consumer_find_socket(uatomic_read(&ust_consumerd32_fd),
-				usess->consumer);
-		if (socket == NULL) {
-			goto skip_setup;
-		}
-		break;
-	default:
-		ret = -EINVAL;
-		goto error_rcu_unlock;
-	}
-
-	/* Setup UST consumer socket and send fds to it */
-	ret = ust_consumer_send_session(ua_sess, usess->consumer, socket);
-	if (ret < 0) {
-		goto error_rcu_unlock;
-	}
-
-	health_code_update(&health_thread_cmd);
+	health_code_update();
 
 skip_setup:
 	/* This start the UST tracing */
 	ret = ustctl_start_session(app->sock, ua_sess->handle);
 	if (ret < 0) {
-		ERR("Error starting tracing for app pid: %d", app->pid);
+		if (ret != -EPIPE && ret != -LTTNG_UST_ERR_EXITING) {
+			ERR("Error starting tracing for app pid: %d (ret: %d)",
+					app->pid, ret);
+		} else {
+			DBG("UST app start session failed. Application is dead.");
+		}
 		goto error_rcu_unlock;
 	}
 
 	/* Indicate that the session has been started once */
 	ua_sess->started = 1;
 
-	health_code_update(&health_thread_cmd);
+	health_code_update();
 
 	/* Quiescent wait after starting trace */
-	ustctl_wait_quiescent(app->sock);
+	ret = ustctl_wait_quiescent(app->sock);
+	if (ret < 0 && ret != -EPIPE && ret != -LTTNG_UST_ERR_EXITING) {
+		ERR("UST app wait quiescent failed for app pid %d ret %d",
+				app->pid, ret);
+	}
 
 end:
 	rcu_read_unlock();
-	health_code_update(&health_thread_cmd);
+	health_code_update();
 	return 0;
 
 error_rcu_unlock:
 	rcu_read_unlock();
-	health_code_update(&health_thread_cmd);
+	health_code_update();
 	return -1;
 }
 
@@ -2402,56 +2553,79 @@ int ust_app_stop_trace(struct ltt_ust_session *usess, struct ust_app *app)
 	 * from either the application manager thread or the command thread. Simply
 	 * indicate that this is a stop error.
 	 */
-	if (ua_sess->started == 1) {
+	if (!ua_sess->started) {
 		goto error_rcu_unlock;
 	}
 
-	health_code_update(&health_thread_cmd);
+	health_code_update();
 
 	/* This inhibits UST tracing */
 	ret = ustctl_stop_session(app->sock, ua_sess->handle);
 	if (ret < 0) {
-		ERR("Error stopping tracing for app pid: %d", app->pid);
+		if (ret != -EPIPE && ret != -LTTNG_UST_ERR_EXITING) {
+			ERR("Error stopping tracing for app pid: %d (ret: %d)",
+					app->pid, ret);
+		} else {
+			DBG("UST app stop session failed. Application is dead.");
+		}
 		goto error_rcu_unlock;
 	}
 
-	health_code_update(&health_thread_cmd);
+	health_code_update();
 
 	/* Quiescent wait after stopping trace */
-	ustctl_wait_quiescent(app->sock);
+	ret = ustctl_wait_quiescent(app->sock);
+	if (ret < 0 && ret != -EPIPE && ret != -LTTNG_UST_ERR_EXITING) {
+		ERR("UST app wait quiescent failed for app pid %d ret %d",
+				app->pid, ret);
+	}
 
-	health_code_update(&health_thread_cmd);
+	health_code_update();
 
 	/* Flushing buffers */
 	cds_lfht_for_each_entry(ua_sess->channels->ht, &iter.iter, ua_chan,
 			node.node) {
-		health_code_update(&health_thread_cmd);
+		health_code_update();
+		assert(ua_chan->is_sent);
 		ret = ustctl_sock_flush_buffer(app->sock, ua_chan->obj);
 		if (ret < 0) {
-			ERR("UST app PID %d channel %s flush failed with ret %d",
-					app->pid, ua_chan->name, ret);
+			if (ret != -EPIPE && ret != -LTTNG_UST_ERR_EXITING) {
+				ERR("UST app PID %d channel %s flush failed with ret %d",
+						app->pid, ua_chan->name, ret);
+			} else {
+				DBG3("UST app failed to flush %s. Application is dead.",
+						ua_chan->name);
+				/* No need to continue. */
+				goto end;
+			}
 			/* Continuing flushing all buffers */
 			continue;
 		}
 	}
 
-	health_code_update(&health_thread_cmd);
+	health_code_update();
 
+	assert(ua_sess->metadata->is_sent);
 	/* Flush all buffers before stopping */
 	ret = ustctl_sock_flush_buffer(app->sock, ua_sess->metadata->obj);
 	if (ret < 0) {
-		ERR("UST app PID %d metadata flush failed with ret %d", app->pid,
-				ret);
+		if (ret != -EPIPE && ret != -LTTNG_UST_ERR_EXITING) {
+			ERR("UST app PID %d metadata flush failed with ret %d", app->pid,
+					ret);
+			goto error_rcu_unlock;
+		} else {
+			DBG3("UST app failed to flush metadata. Application is dead.");
+		}
 	}
 
 end:
 	rcu_read_unlock();
-	health_code_update(&health_thread_cmd);
+	health_code_update();
 	return 0;
 
 error_rcu_unlock:
 	rcu_read_unlock();
-	health_code_update(&health_thread_cmd);
+	health_code_update();
 	return -1;
 }
 
@@ -2460,11 +2634,10 @@ error_rcu_unlock:
  */
 static int destroy_trace(struct ltt_ust_session *usess, struct ust_app *app)
 {
+	int ret;
 	struct ust_app_session *ua_sess;
-	struct lttng_ust_object_data obj;
 	struct lttng_ht_iter iter;
 	struct lttng_ht_node_ulong *node;
-	int ret;
 
 	DBG("Destroy tracing for ust app pid %d", app->pid);
 
@@ -2481,28 +2654,22 @@ static int destroy_trace(struct ltt_ust_session *usess, struct ust_app *app)
 		goto end;
 	}
 	ua_sess = caa_container_of(node, struct ust_app_session, node);
-	ret = lttng_ht_del(app->sessions, &iter);
-	if (ret) {
-		/* Already scheduled for teardown. */
-		goto end;
-	}
 
-	obj.handle = ua_sess->handle;
-	obj.shm_fd = -1;
-	obj.wait_fd = -1;
-	obj.memory_map_size = 0;
-	health_code_update(&health_thread_cmd);
-	ustctl_release_object(app->sock, &obj);
+	health_code_update();
+	destroy_session(app, ua_sess);
 
-	health_code_update(&health_thread_cmd);
-	delete_ust_app_session(app->sock, ua_sess);
+	health_code_update();
 
 	/* Quiescent wait after stopping trace */
-	ustctl_wait_quiescent(app->sock);
+	ret = ustctl_wait_quiescent(app->sock);
+	if (ret < 0 && ret != -EPIPE && ret != -LTTNG_UST_ERR_EXITING) {
+		ERR("UST app wait quiescent failed for app pid %d ret %d",
+				app->pid, ret);
+	}
 
 end:
 	rcu_read_unlock();
-	health_code_update(&health_thread_cmd);
+	health_code_update();
 	return 0;
 }
 
@@ -2592,12 +2759,13 @@ void ust_app_global_update(struct ltt_ust_session *usess, int sock)
 	int ret = 0;
 	struct lttng_ht_iter iter, uiter, iter_ctx;
 	struct ust_app *app;
-	struct ust_app_session *ua_sess;
+	struct ust_app_session *ua_sess = NULL;
 	struct ust_app_channel *ua_chan;
 	struct ust_app_event *ua_event;
 	struct ust_app_ctx *ua_ctx;
 
 	assert(usess);
+	assert(sock >= 0);
 
 	DBG2("UST app global update for app sock %d for session id %d", sock,
 			usess->id);
@@ -2606,7 +2774,7 @@ void ust_app_global_update(struct ltt_ust_session *usess, int sock)
 
 	app = find_app_by_sock(sock);
 	if (app == NULL) {
-		ERR("Failed to update app sock %d", sock);
+		ERR("Failed to find app sock %d", sock);
 		goto error;
 	}
 
@@ -2614,11 +2782,12 @@ void ust_app_global_update(struct ltt_ust_session *usess, int sock)
 		goto error;
 	}
 
-	ua_sess = create_ust_app_session(usess, app);
-	if (ua_sess == NULL || ua_sess == (void *) -1UL) {
-		/* Tracer is gone for this session and has been freed */
+	ret = create_ust_app_session(usess, app, &ua_sess, NULL);
+	if (ret < 0) {
+		/* Tracer is probably gone or ENOMEM. */
 		goto error;
 	}
+	assert(ua_sess);
 
 	/*
 	 * We can iterate safely here over all UST app session sicne the create ust
@@ -2627,18 +2796,21 @@ void ust_app_global_update(struct ltt_ust_session *usess, int sock)
 	 */
 	cds_lfht_for_each_entry(ua_sess->channels->ht, &iter.iter, ua_chan,
 			node.node) {
-		ret = create_ust_channel(app, ua_sess, ua_chan);
+		ret = create_ust_channel(app, ua_sess, ua_chan, usess->consumer);
 		if (ret < 0) {
-			/* FIXME: Should we quit here or continue... */
-			continue;
+			/*
+			 * Stop everything. On error, the application failed, no more file
+			 * descriptor are available or ENOMEM so stopping here is the only
+			 * thing we can do for now.
+			 */
+			goto error;
 		}
 
 		cds_lfht_for_each_entry(ua_chan->ctx->ht, &iter_ctx.iter, ua_ctx,
 				node.node) {
 			ret = create_ust_channel_context(ua_chan, ua_ctx, app);
 			if (ret < 0) {
-				/* FIXME: Should we quit here or continue... */
-				continue;
+				goto error;
 			}
 		}
 
@@ -2648,14 +2820,7 @@ void ust_app_global_update(struct ltt_ust_session *usess, int sock)
 				node.node) {
 			ret = create_ust_event(app, ua_sess, ua_chan, ua_event);
 			if (ret < 0) {
-				/* FIXME: Should we quit here or continue... */
-				continue;
-			}
-
-			ret = set_ust_event_filter(ua_event, app);
-			if (ret < 0) {
-				/* FIXME: Should we quit here or continue... */
-				continue;
+				goto error;
 			}
 		}
 	}
@@ -2669,7 +2834,14 @@ void ust_app_global_update(struct ltt_ust_session *usess, int sock)
 		DBG2("UST trace started for app pid %d", app->pid);
 	}
 
+	/* Everything went well at this point. */
+	rcu_read_unlock();
+	return;
+
 error:
+	if (ua_sess) {
+		destroy_session(app, ua_sess);
+	}
 	rcu_read_unlock();
 	return;
 }
@@ -2860,10 +3032,13 @@ int ust_app_validate_version(int sock)
 	app = find_app_by_sock(sock);
 	assert(app);
 
-	health_code_update(&health_thread_cmd);
+	health_code_update();
 
 	ret = ustctl_tracer_version(sock, &app->version);
 	if (ret < 0) {
+		if (ret != -EPIPE && ret != -LTTNG_UST_ERR_EXITING) {
+			ERR("UST app tracer version failed for app pid %d", app->pid);
+		}
 		goto error;
 	}
 
@@ -2877,7 +3052,7 @@ int ust_app_validate_version(int sock)
 			UST_APP_MAJOR_VERSION);
 	app->compatible = 1;
 	rcu_read_unlock();
-	health_code_update(&health_thread_cmd);
+	health_code_update();
 	return 0;
 
 error:
@@ -2886,7 +3061,7 @@ error:
 			UST_APP_MAJOR_VERSION);
 	app->compatible = 0;
 	rcu_read_unlock();
-	health_code_update(&health_thread_cmd);
+	health_code_update();
 	return -1;
 }
 
@@ -2910,7 +3085,7 @@ int ust_app_calibrate_glb(struct lttng_ust_calibrate *calibrate)
 			continue;
 		}
 
-		health_code_update(&health_thread_cmd);
+		health_code_update();
 
 		ret = ustctl_calibrate(app->sock, calibrate);
 		if (ret < 0) {
@@ -2920,7 +3095,6 @@ int ust_app_calibrate_glb(struct lttng_ust_calibrate *calibrate)
 				ret = 0;
 				break;
 			default:
-				/* TODO: Report error to user */
 				DBG2("Calibrate app PID %d returned with error %d",
 						app->pid, ret);
 				break;
@@ -2932,7 +3106,7 @@ int ust_app_calibrate_glb(struct lttng_ust_calibrate *calibrate)
 
 	rcu_read_unlock();
 
-	health_code_update(&health_thread_cmd);
+	health_code_update();
 
 	return ret;
 }