X-Git-Url: https://git.lttng.org/?p=lttng-tools.git;a=blobdiff_plain;f=lttng-sessiond%2Fust-app.c;h=69164126beafbe15e276a7f694bc5dc2045cd7b9;hp=cd5829cb6342bcc8f19676d1698c4193b9a9564d;hb=ac3bd9c0d406b3230680d06ab189bcb95337b9cc;hpb=aea829b3086fb53d411eb79a5abe0e706d4d9cf3

diff --git a/lttng-sessiond/ust-app.c b/lttng-sessiond/ust-app.c
index cd5829cb6..69164126b 100644
--- a/lttng-sessiond/ust-app.c
+++ b/lttng-sessiond/ust-app.c
@@ -35,20 +35,43 @@
 #include "ust-consumer.h"
 #include "ust-ctl.h"
 
+/*
+ * Delete ust context safely. RCU read lock must be held before calling
+ * this function.
+ */
+static
+void delete_ust_app_ctx(int sock, struct ust_app_ctx *ua_ctx)
+{
+	if (ua_ctx->obj) {
+		ustctl_release_object(sock, ua_ctx->obj);
+		free(ua_ctx->obj);
+	}
+	free(ua_ctx);
+}
+
 /*
  * Delete ust app event safely. RCU read lock must be held before calling
  * this function.
  */
-static void delete_ust_app_event(int sock, struct ust_app_event *ua_event)
+static
+void delete_ust_app_event(int sock, struct ust_app_event *ua_event)
 {
-	/* TODO : remove context */
-	//struct ust_app_ctx *ltctx;
-	//cds_lfht_for_each_entry(lte->ctx, &iter, ltctx, node) {
-	//	delete_ust_app_ctx(sock, ltctx);
-	//}
-
-	ustctl_release_object(sock, ua_event->obj);
-	free(ua_event->obj);
+	int ret;
+	struct cds_lfht_iter iter;
+	struct ust_app_ctx *ua_ctx;
+
+	cds_lfht_for_each_entry(ua_event->ctx, &iter, ua_ctx, node) {
+		ret = hashtable_del(ua_event->ctx, &iter);
+		assert(!ret);
+		delete_ust_app_ctx(sock, ua_ctx);
+	}
+	ret = hashtable_destroy(ua_event->ctx);
+	assert(!ret);
+
+	if (ua_event->obj != NULL) {
+		ustctl_release_object(sock, ua_event->obj);
+		free(ua_event->obj);
+	}
 	free(ua_event);
 }
 
@@ -56,10 +79,13 @@ static void delete_ust_app_event(int sock, struct ust_app_event *ua_event)
  * Delete ust app stream safely. RCU read lock must be held before calling
  * this function.
  */
-static void delete_ust_app_stream(int sock, struct ltt_ust_stream *stream)
+static
+void delete_ust_app_stream(int sock, struct ltt_ust_stream *stream)
 {
-	ustctl_release_object(sock, stream->obj);
-	free(stream->obj);
+	if (stream->obj) {
+		ustctl_release_object(sock, stream->obj);
+		free(stream->obj);
+	}
 	free(stream);
 }
 
@@ -67,87 +93,90 @@ static void delete_ust_app_stream(int sock, struct ltt_ust_stream *stream)
  * Delete ust app channel safely. RCU read lock must be held before calling
  * this function.
  */
-static void delete_ust_app_channel(int sock, struct ust_app_channel *ua_chan)
+static
+void delete_ust_app_channel(int sock, struct ust_app_channel *ua_chan)
 {
 	int ret;
 	struct cds_lfht_iter iter;
 	struct ust_app_event *ua_event;
+	struct ust_app_ctx *ua_ctx;
 	struct ltt_ust_stream *stream, *stmp;
 
+	/* Wipe stream */
 	cds_list_for_each_entry_safe(stream, stmp, &ua_chan->streams.head, list) {
 		cds_list_del(&stream->list);
 		delete_ust_app_stream(sock, stream);
 	}
 
-	/* TODO : remove channel context */
-	//cds_lfht_for_each_entry(ltc->ctx, &iter, ltctx, node) {
-	//	hashtable_del(ltc->ctx, &iter);
-	//	delete_ust_app_ctx(sock, ltctx);
-	//}
-	//ret = hashtable_destroy(ltc->ctx);
+	/* Wipe context */
+	cds_lfht_for_each_entry(ua_chan->ctx, &iter, ua_ctx, node) {
+		ret = hashtable_del(ua_chan->ctx, &iter);
+		assert(!ret);
+		delete_ust_app_ctx(sock, ua_ctx);
+	}
+	ret = hashtable_destroy(ua_chan->ctx);
+	assert(!ret);
 
+	/* Wipe events */
 	cds_lfht_for_each_entry(ua_chan->events, &iter, ua_event, node) {
-		hashtable_del(ua_chan->events, &iter);
+		ret = hashtable_del(ua_chan->events, &iter);
+		assert(!ret);
 		delete_ust_app_event(sock, ua_event);
 	}
-
 	ret = hashtable_destroy(ua_chan->events);
-	if (ret < 0) {
-		ERR("UST app destroy session hashtable failed");
-		goto error;
+	assert(!ret);
+
+	if (ua_chan->obj != NULL) {
+		ustctl_release_object(sock, ua_chan->obj);
+		free(ua_chan->obj);
 	}
-	ustctl_release_object(sock, ua_chan->obj);
-	free(ua_chan->obj);
 	free(ua_chan);
-
-error:
-	return;
 }
 
 /*
  * Delete ust app session safely. RCU read lock must be held before calling
  * this function.
  */
-static void delete_ust_app_session(int sock,
-		struct ust_app_session *ua_sess)
+static
+void delete_ust_app_session(int sock, struct ust_app_session *ua_sess)
 {
 	int ret;
 	struct cds_lfht_iter iter;
 	struct ust_app_channel *ua_chan;
 
 	if (ua_sess->metadata) {
-		ustctl_release_object(sock, ua_sess->metadata->stream_obj);
-		free(ua_sess->metadata->stream_obj);
-		ustctl_release_object(sock, ua_sess->metadata->obj);
-		free(ua_sess->metadata->obj);
+		if (ua_sess->metadata->stream_obj) {
+			ustctl_release_object(sock, ua_sess->metadata->stream_obj);
+			free(ua_sess->metadata->stream_obj);
+		}
+		if (ua_sess->metadata->obj) {
+			ustctl_release_object(sock, ua_sess->metadata->obj);
+			free(ua_sess->metadata->obj);
+		}
 	}
 
 	cds_lfht_for_each_entry(ua_sess->channels, &iter, ua_chan, node) {
-		hashtable_del(ua_sess->channels, &iter);
+		ret = hashtable_del(ua_sess->channels, &iter);
+		assert(!ret);
 		delete_ust_app_channel(sock, ua_chan);
 	}
-
 	ret = hashtable_destroy(ua_sess->channels);
-	if (ret < 0) {
-		ERR("UST app destroy session hashtable failed");
-		goto error;
-	}
+	assert(!ret);
 
-error:
-	return;
+	free(ua_sess);
 }
 
 /*
  * Delete a traceable application structure from the global list. Never call
  * this function outside of a call_rcu call.
  */
-static void delete_ust_app(struct ust_app *app)
+static
+void delete_ust_app(struct ust_app *app)
 {
-	int ret;
+	int ret, sock;
 	struct cds_lfht_node *node;
 	struct cds_lfht_iter iter;
 	struct ust_app_session *ua_sess;
-	int sock;
 
 	rcu_read_lock();
 
@@ -175,16 +204,14 @@ static void delete_ust_app(struct ust_app *app)
 	sock = app->key.sock;
 	app->key.sock = -1;
 
+	/* Wipe sessions */
 	cds_lfht_for_each_entry(app->sessions, &iter, ua_sess, node) {
-		hashtable_del(app->sessions, &iter);
+		ret = hashtable_del(app->sessions, &iter);
+		assert(!ret);
 		delete_ust_app_session(app->key.sock, ua_sess);
 	}
-
 	ret = hashtable_destroy(app->sessions);
-	if (ret < 0) {
-		ERR("UST app destroy session hashtable failed");
-		goto end;
-	}
+	assert(!ret);
 
 	/*
 	 * Wait until we have removed the key from the sock hash table
@@ -203,7 +230,8 @@ end:
 /*
  * URCU intermediate call to delete an UST app.
  */
-static void delete_ust_app_rcu(struct rcu_head *head)
+static
+void delete_ust_app_rcu(struct rcu_head *head)
 {
 	struct cds_lfht_node *node =
 		caa_container_of(head, struct cds_lfht_node, head);
@@ -213,11 +241,137 @@ static void delete_ust_app_rcu(struct rcu_head *head)
 	delete_ust_app(app);
 }
 
+/*
+ * Alloc new UST app session.
+ */
+static
+struct ust_app_session *alloc_ust_app_session(void)
+{
+	struct ust_app_session *ua_sess;
+
+	/* Init most of the default value by allocating and zeroing */
+	ua_sess = zmalloc(sizeof(struct ust_app_session));
+	if (ua_sess == NULL) {
+		PERROR("malloc");
+		goto error;
+	}
+
+	ua_sess->handle = -1;
+	ua_sess->channels = hashtable_new_str(0);
+
+	return ua_sess;
+
+error:
+	return NULL;
+}
+
+/*
+ * Alloc new UST app channel.
+ */
+static
+struct ust_app_channel *alloc_ust_app_channel(char *name,
+		struct lttng_ust_channel *attr)
+{
+	struct ust_app_channel *ua_chan;
+
+	/* Init most of the default value by allocating and zeroing */
+	ua_chan = zmalloc(sizeof(struct ust_app_channel));
+	if (ua_chan == NULL) {
+		PERROR("malloc");
+		goto error;
+	}
+
+	/* Setup channel name */
+	strncpy(ua_chan->name, name, sizeof(ua_chan->name));
+	ua_chan->name[sizeof(ua_chan->name) - 1] = '\0';
+
+	ua_chan->enabled = 1;
+	ua_chan->handle = -1;
+	ua_chan->ctx = hashtable_new(0);
+	ua_chan->events = hashtable_new_str(0);
+	hashtable_node_init(&ua_chan->node, (void *) ua_chan->name,
+			strlen(ua_chan->name));
+
+	CDS_INIT_LIST_HEAD(&ua_chan->streams.head);
+
+	/* Copy attributes */
+	if (attr) {
+		memcpy(&ua_chan->attr, attr, sizeof(ua_chan->attr));
+	}
+
+	DBG3("UST app channel %s allocated", ua_chan->name);
+
+	return ua_chan;
+
+error:
+	return NULL;
+}
+
+/*
+ * Alloc new UST app event.
+ */
+static
+struct ust_app_event *alloc_ust_app_event(char *name,
+		struct lttng_ust_event *attr)
+{
+	struct ust_app_event *ua_event;
+
+	/* Init most of the default value by allocating and zeroing */
+	ua_event = zmalloc(sizeof(struct ust_app_event));
+	if (ua_event == NULL) {
+		PERROR("malloc");
+		goto error;
+	}
+
+	ua_event->enabled = 1;
+	strncpy(ua_event->name, name, sizeof(ua_event->name));
+	ua_event->name[sizeof(ua_event->name) - 1] = '\0';
+	ua_event->ctx = hashtable_new(0);
+	hashtable_node_init(&ua_event->node, (void *) ua_event->name,
+			strlen(ua_event->name));
+
+	/* Copy attributes */
+	if (attr) {
+		memcpy(&ua_event->attr, attr, sizeof(ua_event->attr));
+	}
+
+	DBG3("UST app event %s allocated", ua_event->name);
+
+	return ua_event;
+
+error:
+	return NULL;
+}
+
+/*
+ * Alloc new UST app context.
+ */
+static
+struct ust_app_ctx *alloc_ust_app_ctx(struct lttng_ust_context *uctx)
+{
+	struct ust_app_ctx *ua_ctx;
+
+	ua_ctx = zmalloc(sizeof(struct ust_app_ctx));
+	if (ua_ctx == NULL) {
+		goto error;
+	}
+
+	if (uctx) {
+		memcpy(&ua_ctx->ctx, uctx, sizeof(ua_ctx->ctx));
+	}
+
+	DBG3("UST app context %d allocated", ua_ctx->ctx.ctx);
+
+error:
+	return ua_ctx;
+}
+
 /*
  * 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)
+static
+struct ust_app *find_app_by_sock(int sock)
 {
 	struct cds_lfht_node *node;
 	struct ust_app_key *key;
@@ -244,6 +398,146 @@ error:
 	return NULL;
 }
 
+/*
+ * Create the channel context on the tracer.
+ */
+static
+int create_ust_channel_context(struct ust_app_channel *ua_chan,
+		struct ust_app_ctx *ua_ctx, struct ust_app *app)
+{
+	int ret;
+
+	ret = ustctl_add_context(app->key.sock, &ua_ctx->ctx,
+			ua_chan->obj, &ua_ctx->obj);
+	if (ret < 0) {
+		goto error;
+	}
+
+	ua_ctx->handle = ua_ctx->obj->handle;
+
+	DBG2("UST app context added to channel %s successfully", ua_chan->name);
+
+error:
+	return ret;
+}
+
+/*
+ * Create the event context on the tracer.
+ */
+static
+int create_ust_event_context(struct ust_app_event *ua_event,
+		struct ust_app_ctx *ua_ctx, struct ust_app *app)
+{
+	int ret;
+
+	ret = ustctl_add_context(app->key.sock, &ua_ctx->ctx,
+			ua_event->obj, &ua_ctx->obj);
+	if (ret < 0) {
+		goto error;
+	}
+
+	ua_ctx->handle = ua_ctx->obj->handle;
+
+	DBG2("UST app context added to event %s successfully", ua_event->name);
+
+error:
+	return ret;
+}
+
+/*
+ * Disable the specified event on to UST tracer for the UST session.
+ */
+static int disable_ust_event(struct ust_app *app,
+		struct ust_app_session *ua_sess, struct ust_app_event *ua_event)
+{
+	int ret;
+
+	ret = ustctl_disable(app->key.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->key.pid, ua_sess->handle, ret);
+		goto error;
+	}
+
+	DBG2("UST app event %s disabled successfully for app (pid: %d)",
+			ua_event->attr.name, app->key.pid);
+
+error:
+	return ret;
+}
+
+/*
+ * Disable the specified channel on to UST tracer for the UST session.
+ */
+static int disable_ust_channel(struct ust_app *app,
+		struct ust_app_session *ua_sess, struct ust_app_channel *ua_chan)
+{
+	int ret;
+
+	ret = ustctl_disable(app->key.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->key.pid, ua_sess->handle, ret);
+		goto error;
+	}
+
+	DBG2("UST app channel %s disabled successfully for app (pid: %d)",
+			ua_chan->name, app->key.pid);
+
+error:
+	return ret;
+}
+
+/*
+ * Enable the specified channel on to UST tracer for the UST session.
+ */
+static int enable_ust_channel(struct ust_app *app,
+		struct ust_app_session *ua_sess, struct ust_app_channel *ua_chan)
+{
+	int ret;
+
+	ret = ustctl_enable(app->key.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->key.pid, ua_sess->handle, ret);
+		goto error;
+	}
+
+	ua_chan->enabled = 1;
+
+	DBG2("UST app channel %s enabled successfully for app (pid: %d)",
+			ua_chan->name, app->key.pid);
+
+error:
+	return ret;
+}
+
+/*
+ * Enable the specified event on to UST tracer for the UST session.
+ */
+static int enable_ust_event(struct ust_app *app,
+		struct ust_app_session *ua_sess, struct ust_app_event *ua_event)
+{
+	int ret;
+
+	ret = ustctl_enable(app->key.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->key.pid, ua_sess->handle, ret);
+		goto error;
+	}
+
+	DBG2("UST app event %s enabled successfully for app (pid: %d)",
+			ua_event->attr.name, app->key.pid);
+
+error:
+	return ret;
+}
+
 /*
  * Open metadata onto the UST tracer for a UST session.
  */
@@ -321,6 +615,14 @@ static int create_ust_channel(struct ust_app *app,
 	DBG2("UST app channel %s created successfully for pid:%d and sock:%d",
 			ua_chan->name, app->key.pid, app->key.sock);
 
+	/* If channel is not enabled, disable it on the tracer */
+	if (!ua_chan->enabled) {
+		ret = disable_ust_channel(app, ua_sess, ua_chan);
+		if (ret < 0) {
+			goto error;
+		}
+	}
+
 error:
 	return ret;
 }
@@ -328,9 +630,9 @@ error:
 /*
  * Create the specified event onto the UST tracer for a UST session.
  */
-static int create_ust_event(struct ust_app *app,
-		struct ust_app_session *ua_sess, struct ust_app_channel *ua_chan,
-		struct ust_app_event *ua_event)
+static
+int create_ust_event(struct ust_app *app, struct ust_app_session *ua_sess,
+		struct ust_app_channel *ua_chan, struct ust_app_event *ua_event)
 {
 	int ret = 0;
 
@@ -344,110 +646,20 @@ static int create_ust_event(struct ust_app *app,
 	}
 
 	ua_event->handle = ua_event->obj->handle;
-	ua_event->enabled = 1;
 
 	DBG2("UST app event %s created successfully for pid:%d",
 			ua_event->attr.name, app->key.pid);
 
-error:
-	return ret;
-}
-
-/*
- * Alloc new UST app session.
- */
-static struct ust_app_session *alloc_ust_app_session(void)
-{
-	struct ust_app_session *ua_sess;
-
-	/* Init most of the default value by allocating and zeroing */
-	ua_sess = zmalloc(sizeof(struct ust_app_session));
-	if (ua_sess == NULL) {
-		PERROR("malloc");
-		goto error;
-	}
-
-	ua_sess->handle = -1;
-	ua_sess->channels = hashtable_new_str(0);
-
-	return ua_sess;
-
-error:
-	return NULL;
-}
-
-/*
- * Alloc new UST app channel.
- */
-static struct ust_app_channel *alloc_ust_app_channel(char *name,
-		struct lttng_ust_channel *attr)
-{
-	struct ust_app_channel *ua_chan;
-
-	/* Init most of the default value by allocating and zeroing */
-	ua_chan = zmalloc(sizeof(struct ust_app_channel));
-	if (ua_chan == NULL) {
-		PERROR("malloc");
-		goto error;
-	}
-
-	/* Setup channel name */
-	strncpy(ua_chan->name, name, sizeof(ua_chan->name));
-	ua_chan->name[sizeof(ua_chan->name) - 1] = '\0';
-
-	ua_chan->handle = -1;
-	ua_chan->ctx = hashtable_new(0);
-	ua_chan->events = hashtable_new_str(0);
-	hashtable_node_init(&ua_chan->node, (void *) ua_chan->name,
-			strlen(ua_chan->name));
-
-	CDS_INIT_LIST_HEAD(&ua_chan->streams.head);
-
-	/* Copy attributes */
-	if (attr) {
-		memcpy(&ua_chan->attr, attr, sizeof(ua_chan->attr));
-	}
-
-	DBG3("UST app channel %s allocated", ua_chan->name);
-
-	return ua_chan;
-
-error:
-	return NULL;
-}
-
-/*
- * Alloc new UST app event.
- */
-static struct ust_app_event *alloc_ust_app_event(char *name,
-		struct lttng_ust_event *attr)
-{
-	struct ust_app_event *ua_event;
-
-	/* Init most of the default value by allocating and zeroing */
-	ua_event = zmalloc(sizeof(struct ust_app_event));
-	if (ua_event == NULL) {
-		PERROR("malloc");
-		goto error;
-	}
-
-	strncpy(ua_event->name, name, sizeof(ua_event->name));
-	ua_event->name[sizeof(ua_event->name) - 1] = '\0';
-	ua_event->ctx = hashtable_new(0);
-	hashtable_node_init(&ua_event->node, (void *) ua_event->name,
-			strlen(ua_event->name));
-
-	/* Copy attributes */
-	if (attr) {
-		memcpy(&ua_event->attr, attr, sizeof(ua_event->attr));
+	/* If event not enabled, disable it on the tracer */
+	if (!ua_event->enabled) {
+		ret = disable_ust_event(app, ua_sess, ua_event);
+		if (ret < 0) {
+			goto error;
+		}
 	}
 
-	DBG3("UST app event %s allocated", ua_event->name);
-
-	return ua_event;
-
 error:
-	return NULL;
+	return ret;
 }
 
 /*
@@ -456,13 +668,25 @@ error:
 static void shadow_copy_event(struct ust_app_event *ua_event,
 		struct ltt_ust_event *uevent)
 {
+	struct cds_lfht_iter iter;
+	struct ltt_ust_context *uctx;
+	struct ust_app_ctx *ua_ctx;
+
 	strncpy(ua_event->name, uevent->attr.name, sizeof(ua_event->name));
 	ua_event->name[sizeof(ua_event->name) - 1] = '\0';
 
 	/* Copy event attributes */
 	memcpy(&ua_event->attr, &uevent->attr, sizeof(ua_event->attr));
 
-	/* TODO: support copy context */
+	cds_lfht_for_each_entry(uevent->ctx, &iter, uctx, node) {
+		ua_ctx = alloc_ust_app_ctx(&uctx->ctx);
+		if (ua_ctx == NULL) {
+			continue;
+		}
+		hashtable_node_init(&ua_ctx->node,
+				(void *)((unsigned long) ua_ctx->ctx.ctx), sizeof(void *));
+		hashtable_add_unique(ua_event->ctx, &ua_ctx->node);
+	}
 }
 
 /*
@@ -474,7 +698,9 @@ static void shadow_copy_channel(struct ust_app_channel *ua_chan,
 	struct cds_lfht_iter iter;
 	struct cds_lfht_node *ua_event_node;
 	struct ltt_ust_event *uevent;
+	struct ltt_ust_context *uctx;
 	struct ust_app_event *ua_event;
+	struct ust_app_ctx *ua_ctx;
 
 	DBG2("Shadow copy of UST app channel %s", ua_chan->name);
 
@@ -483,7 +709,15 @@ static void shadow_copy_channel(struct ust_app_channel *ua_chan,
 	/* Copy event attributes */
 	memcpy(&ua_chan->attr, &uchan->attr, sizeof(ua_chan->attr));
 
-	/* TODO: support copy context */
+	cds_lfht_for_each_entry(uchan->ctx, &iter, uctx, node) {
+		ua_ctx = alloc_ust_app_ctx(&uctx->ctx);
+		if (ua_ctx == NULL) {
+			continue;
+		}
+		hashtable_node_init(&ua_ctx->node,
+				(void *)((unsigned long) ua_ctx->ctx.ctx), sizeof(void *));
+		hashtable_add_unique(ua_chan->ctx, &ua_ctx->node);
+	}
 
 	/* Copy all events from ltt ust channel to ust app channel */
 	cds_lfht_for_each_entry(uchan->events, &iter, uevent, node) {
@@ -564,91 +798,268 @@ static void shadow_copy_session(struct ust_app_session *ua_sess,
 			continue;
 		}
 
-		shadow_copy_channel(ua_chan, uchan);
-		hashtable_add_unique(ua_sess->channels, &ua_chan->node);
+		shadow_copy_channel(ua_chan, uchan);
+		hashtable_add_unique(ua_sess->channels, &ua_chan->node);
+	}
+}
+
+/*
+ * Lookup sesison wrapper.
+ */
+static
+void __lookup_session_by_app(struct ltt_ust_session *usess,
+			struct ust_app *app, struct cds_lfht_iter *iter)
+{
+	/* Get right UST app session from app */
+	(void) hashtable_lookup(app->sessions,
+			(void *) ((unsigned long) usess->uid), sizeof(void *),
+			iter);
+}
+
+/*
+ * Return ust app session from the app session hashtable using the UST session
+ * uid.
+ */
+static struct ust_app_session *lookup_session_by_app(
+		struct ltt_ust_session *usess, struct ust_app *app)
+{
+	struct cds_lfht_iter iter;
+	struct cds_lfht_node *node;
+
+	__lookup_session_by_app(usess, app, &iter);
+	node = hashtable_iter_get_node(&iter);
+	if (node == NULL) {
+		goto error;
+	}
+
+	return caa_container_of(node, struct ust_app_session, node);
+
+error:
+	return NULL;
+}
+
+/*
+ * Create a UST session onto the tracer of app and add it the session
+ * hashtable.
+ *
+ * Return ust app session or NULL on error.
+ */
+static struct ust_app_session *create_ust_app_session(
+		struct ltt_ust_session *usess, struct ust_app *app)
+{
+	int ret;
+	struct ust_app_session *ua_sess;
+
+	ua_sess = lookup_session_by_app(usess, app);
+	if (ua_sess == NULL) {
+		DBG2("UST app pid: %d session uid %d not found, creating it",
+				app->key.pid, usess->uid);
+		ua_sess = alloc_ust_app_session();
+		if (ua_sess == NULL) {
+			/* Only malloc can failed so something is really wrong */
+			goto error;
+		}
+		shadow_copy_session(ua_sess, usess, app);
+	}
+
+	if (ua_sess->handle == -1) {
+		ret = ustctl_create_session(app->key.sock);
+		if (ret < 0) {
+			ERR("Error creating session for app pid %d, sock %d",
+					app->key.pid, app->key.sock);
+			/* TODO: free() ua_sess */
+			goto error;
+		}
+
+		DBG2("UST app ustctl create session handle %d", ret);
+		ua_sess->handle = ret;
+
+		/* Add ust app session to app's HT */
+		hashtable_node_init(&ua_sess->node,
+				(void *)((unsigned long) ua_sess->uid), sizeof(void *));
+		hashtable_add_unique(app->sessions, &ua_sess->node);
+
+		DBG2("UST app session created successfully with handle %d", ret);
+	}
+
+	return ua_sess;
+
+error:
+	return NULL;
+}
+
+/*
+ * Create a context for the channel on the tracer.
+ */
+static
+int create_ust_app_channel_context(struct ust_app_session *ua_sess,
+		struct ust_app_channel *ua_chan, struct lttng_ust_context *uctx,
+		struct ust_app *app)
+{
+	int ret = 0;
+	struct cds_lfht_iter iter;
+	struct cds_lfht_node *node;
+	struct ust_app_ctx *ua_ctx;
+
+	DBG2("UST app adding context to channel %s", ua_chan->name);
+
+	node = hashtable_lookup(ua_chan->ctx, (void *)((unsigned long)uctx->ctx),
+			sizeof(void *), &iter);
+	if (node != NULL) {
+		ret = -EEXIST;
+		goto error;
+	}
+
+	ua_ctx = alloc_ust_app_ctx(uctx);
+	if (ua_ctx == NULL) {
+		/* malloc failed */
+		ret = -1;
+		goto error;
+	}
+
+	hashtable_node_init(&ua_ctx->node,
+			(void *)((unsigned long) ua_ctx->ctx.ctx), sizeof(void *));
+	hashtable_add_unique(ua_chan->ctx, &ua_ctx->node);
+
+	ret = create_ust_channel_context(ua_chan, ua_ctx, app);
+	if (ret < 0) {
+		goto error;
+	}
+
+error:
+	return ret;
+}
+
+/*
+ * Create an UST context and enable it for the event on the tracer.
+ */
+static
+int create_ust_app_event_context(struct ust_app_session *ua_sess,
+		struct ust_app_event *ua_event, struct lttng_ust_context *uctx,
+		struct ust_app *app)
+{
+	int ret = 0;
+	struct cds_lfht_iter iter;
+	struct cds_lfht_node *node;
+	struct ust_app_ctx *ua_ctx;
+
+	DBG2("UST app adding context to event %s", ua_event->name);
+
+	node = hashtable_lookup(ua_event->ctx, (void *)((unsigned long)uctx->ctx),
+			sizeof(void *), &iter);
+	if (node != NULL) {
+		ret = -EEXIST;
+		goto error;
+	}
+
+	ua_ctx = alloc_ust_app_ctx(uctx);
+	if (ua_ctx == NULL) {
+		/* malloc failed */
+		ret = -1;
+		goto error;
+	}
+
+	hashtable_node_init(&ua_ctx->node,
+			(void *)((unsigned long) ua_ctx->ctx.ctx), sizeof(void *));
+	hashtable_add_unique(ua_event->ctx, &ua_ctx->node);
+
+	ret = create_ust_event_context(ua_event, ua_ctx, app);
+	if (ret < 0) {
+		goto error;
 	}
+
+error:
+	return ret;
 }
 
+/*
+ * Enable on the tracer side a ust app event for the session and channel.
+ */
 static
-void __lookup_session_by_app(struct ltt_ust_session *usess,
-			struct ust_app *app, struct cds_lfht_iter *iter)
+int enable_ust_app_event(struct ust_app_session *ua_sess,
+		struct ust_app_event *ua_event, struct ust_app *app)
 {
-	/* Get right UST app session from app */
-	(void) hashtable_lookup(app->sessions,
-			(void *) ((unsigned long) usess->uid), sizeof(void *),
-			iter);
+	int ret;
+
+	ret = enable_ust_event(app, ua_sess, ua_event);
+	if (ret < 0) {
+		goto error;
+	}
+
+	ua_event->enabled = 1;
+
+error:
+	return ret;
 }
 
 /*
- * Return ust app session from the app session hashtable using the UST session
- * uid.
+ * Disable on the tracer side a ust app event for the session and channel.
  */
-static struct ust_app_session *lookup_session_by_app(
-		struct ltt_ust_session *usess, struct ust_app *app)
+static int disable_ust_app_event(struct ust_app_session *ua_sess,
+		struct ust_app_channel *ua_chan, struct ust_app_event *ua_event,
+		struct ust_app *app)
 {
-	struct cds_lfht_iter iter;
-	struct cds_lfht_node *node;
+	int ret;
 
-	__lookup_session_by_app(usess, app, &iter);
-	node = hashtable_iter_get_node(&iter);
-	if (node == NULL) {
+	ret = disable_ust_event(app, ua_sess, ua_event);
+	if (ret < 0) {
 		goto error;
 	}
 
-	return caa_container_of(node, struct ust_app_session, node);
+	ua_event->enabled = 0;
 
 error:
-	return NULL;
+	return ret;
 }
 
 /*
- * Create a UST session onto the tracer of app and add it the session
- * hashtable.
- *
- * Return ust app session or NULL on error.
+ * Lookup ust app channel for session and disable it on the tracer side.
  */
-static struct ust_app_session *create_ust_app_session(
-		struct ltt_ust_session *usess, struct ust_app *app)
+static
+int disable_ust_app_channel(struct ust_app_session *ua_sess,
+		struct ust_app_channel *ua_chan, struct ust_app *app)
 {
 	int ret;
-	struct ust_app_session *ua_sess;
 
-	ua_sess = lookup_session_by_app(usess, app);
-	if (ua_sess == NULL) {
-		DBG2("UST app pid: %d session uid %d not found, creating it",
-				app->key.pid, usess->uid);
-		ua_sess = alloc_ust_app_session();
-		if (ua_sess == NULL) {
-			/* Only malloc can failed so something is really wrong */
-			goto error;
-		}
-		shadow_copy_session(ua_sess, usess, app);
+	ret = disable_ust_channel(app, ua_sess, ua_chan);
+	if (ret < 0) {
+		goto error;
 	}
 
-	if (ua_sess->handle == -1) {
-		ret = ustctl_create_session(app->key.sock);
-		if (ret < 0) {
-			ERR("Error creating session for app pid %d, sock %d",
-					app->key.pid, app->key.sock);
-			/* TODO: free() ua_sess */
-			goto error;
-		}
+	ua_chan->enabled = 0;
 
-		DBG2("UST app ustctl create session handle %d", ret);
-		ua_sess->handle = ret;
+error:
+	return ret;
+}
 
-		/* Add ust app session to app's HT */
-		hashtable_node_init(&ua_sess->node,
-				(void *)((unsigned long) ua_sess->uid), sizeof(void *));
-		hashtable_add_unique(app->sessions, &ua_sess->node);
+/*
+ * Lookup ust app channel for session and enable it on the tracer side.
+ */
+static int enable_ust_app_channel(struct ust_app_session *ua_sess,
+		struct ltt_ust_channel *uchan, struct ust_app *app)
+{
+	int ret = 0;
+	struct cds_lfht_iter iter;
+	struct cds_lfht_node *ua_chan_node;
+	struct ust_app_channel *ua_chan;
 
-		DBG2("UST app session created successfully with handle %d", ret);
+	ua_chan_node = hashtable_lookup(ua_sess->channels,
+			(void *)uchan->name, strlen(uchan->name), &iter);
+	if (ua_chan_node == NULL) {
+		DBG2("Unable to find channel %s in ust session uid %u",
+				uchan->name, ua_sess->uid);
+		goto error;
 	}
 
-	return ua_sess;
+	ua_chan = caa_container_of(ua_chan_node, struct ust_app_channel, node);
+
+	ret = enable_ust_channel(app, ua_sess, ua_chan);
+	if (ret < 0) {
+		goto error;
+	}
 
 error:
-	return NULL;
+	return ret;
 }
 
 /*
@@ -694,11 +1105,12 @@ error:
 /*
  * Create UST app event and create it on the tracer side.
  */
-static struct ust_app_event *create_ust_app_event(
-		struct ust_app_session *ua_sess, struct ust_app_channel *ua_chan,
-		struct ltt_ust_event *uevent, struct ust_app *app)
+static
+int create_ust_app_event(struct ust_app_session *ua_sess,
+		struct ust_app_channel *ua_chan, struct ltt_ust_event *uevent,
+		struct ust_app *app)
 {
-	int ret;
+	int ret = 0;
 	struct cds_lfht_iter iter;
 	struct cds_lfht_node *ua_event_node;
 	struct ust_app_event *ua_event;
@@ -706,30 +1118,37 @@ static struct ust_app_event *create_ust_app_event(
 	/* Get event node */
 	ua_event_node = hashtable_lookup(ua_chan->events,
 			(void *)uevent->attr.name, strlen(uevent->attr.name), &iter);
-	if (ua_event_node == NULL) {
-		DBG2("UST app event %s not found, creating it", uevent->attr.name);
-		/* Does not exist so create one */
-		ua_event = alloc_ust_app_event(uevent->attr.name, &uevent->attr);
-		if (ua_event == NULL) {
-			/* Only malloc can failed so something is really wrong */
-			goto error;
-		}
-		shadow_copy_event(ua_event, uevent);
+	if (ua_event_node != NULL) {
+		ERR("UST app event %s already exist. Stopping creation.",
+				uevent->attr.name);
+		goto end;
+	}
 
-		hashtable_add_unique(ua_chan->events, &ua_event->node);
-	} else {
-		ua_event = caa_container_of(ua_event_node, struct ust_app_event, node);
+	/* Does not exist so create one */
+	ua_event = alloc_ust_app_event(uevent->attr.name, &uevent->attr);
+	if (ua_event == NULL) {
+		/* Only malloc can failed so something is really wrong */
+		ret = -ENOMEM;
+		goto error;
 	}
+	shadow_copy_event(ua_event, uevent);
 
+	/* Create it on the tracer side */
 	ret = create_ust_event(app, ua_sess, ua_chan, ua_event);
 	if (ret < 0) {
+		rcu_read_lock();
+		delete_ust_app_event(app->key.sock, ua_event);
+		rcu_read_unlock();
 		goto error;
 	}
 
-	return ua_event;
+	ua_event->enabled = 1;
+
+	hashtable_add_unique(ua_chan->events, &ua_event->node);
 
+end:
 error:
-	return NULL;
+	return ret;
 }
 
 /*
@@ -890,6 +1309,7 @@ void ust_app_unregister(int sock)
 	struct ust_app *lta;
 	struct cds_lfht_node *node;
 	struct cds_lfht_iter iter;
+	int ret;
 
 	rcu_read_lock();
 	lta = find_app_by_sock(sock);
@@ -908,130 +1328,336 @@ void ust_app_unregister(int sock)
 		goto error;
 	}
 
-	hashtable_del(ust_app_ht, &iter);
+	ret = hashtable_del(ust_app_ht, &iter);
+	assert(!ret);
 	call_rcu(&node->head, delete_ust_app_rcu);
 error:
 	rcu_read_unlock();
 	return;
 }
 
-/*
- * Return traceable_app_count
- */
-unsigned long ust_app_list_count(void)
-{
-	unsigned long count;
+/*
+ * Return traceable_app_count
+ */
+unsigned long ust_app_list_count(void)
+{
+	unsigned long count;
+
+	rcu_read_lock();
+	count = hashtable_get_count(ust_app_ht);
+	rcu_read_unlock();
+
+	return count;
+}
+
+/*
+ * Fill events array with all events name of all registered apps.
+ */
+int ust_app_list_events(struct lttng_event **events)
+{
+	int ret, handle;
+	size_t nbmem, count = 0;
+	struct cds_lfht_iter iter;
+	struct ust_app *app;
+	struct lttng_event *tmp;
+
+	nbmem = UST_APP_EVENT_LIST_SIZE;
+	tmp = zmalloc(nbmem * sizeof(struct lttng_event));
+	if (tmp == NULL) {
+		PERROR("zmalloc ust app events");
+		ret = -ENOMEM;
+		goto error;
+	}
+
+	rcu_read_lock();
+
+	cds_lfht_for_each_entry(ust_app_ht, &iter, app, node) {
+		struct lttng_ust_tracepoint_iter iter;
+
+		handle = ustctl_tracepoint_list(app->key.sock);
+		if (handle < 0) {
+			ERR("UST app list events getting handle failed for app pid %d",
+					app->key.pid);
+			continue;
+		}
+
+		while ((ret = ustctl_tracepoint_list_get(app->key.sock, handle,
+						&iter)) != -ENOENT) {
+			memcpy(tmp[count].name, iter.name, LTTNG_UST_SYM_NAME_LEN);
+			/* TODO : get loglevel too */
+			if (count > nbmem) {
+				DBG2("Reallocating event list from %zu to %zu bytes", nbmem,
+						nbmem + UST_APP_EVENT_LIST_SIZE);
+				nbmem += UST_APP_EVENT_LIST_SIZE;
+				tmp = realloc(tmp, nbmem * sizeof(struct lttng_event));
+				if (tmp == NULL) {
+					PERROR("realloc ust app events");
+					ret = -ENOMEM;
+					goto rcu_error;
+				}
+			}
+
+			tmp[count].type = LTTNG_UST_TRACEPOINT;
+			tmp[count].pid = app->key.pid;
+			tmp[count].enabled = -1;
+			count++;
+		}
+	}
+
+	ret = count;
+	*events = tmp;
+
+	DBG2("UST app list events done (%zu events)", count);
+
+rcu_error:
+	rcu_read_unlock();
+error:
+	return ret;
+}
+
+/*
+ * Free and clean all traceable apps of the global list.
+ */
+void ust_app_clean_list(void)
+{
+	int ret;
+	struct cds_lfht_iter iter;
+	struct ust_app *app;
+
+	DBG2("UST app cleaning registered apps hash table");
+
+	rcu_read_lock();
+
+	cds_lfht_for_each_entry(ust_app_ht, &iter, app, node) {
+		ret = hashtable_del(ust_app_ht, &iter);
+		assert(!ret);
+		call_rcu(&iter.node->head, delete_ust_app_rcu);
+	}
+
+	hashtable_destroy(ust_app_ht);
+	hashtable_destroy(ust_app_sock_key_map);
+
+	rcu_read_unlock();
+}
+
+/*
+ * Init UST app hash table.
+ */
+void ust_app_ht_alloc(void)
+{
+	ust_app_ht = hashtable_new(0);
+	ust_app_sock_key_map = hashtable_new(0);
+}
+
+/*
+ * For a specific UST session, disable the channel for all registered apps.
+ */
+int ust_app_disable_channel_glb(struct ltt_ust_session *usess,
+		struct ltt_ust_channel *uchan)
+{
+	int ret = 0;
+	struct cds_lfht_iter iter;
+	struct cds_lfht_node *ua_chan_node;
+	struct ust_app *app;
+	struct ust_app_session *ua_sess;
+	struct ust_app_channel *ua_chan;
+
+	if (usess == NULL || uchan == NULL) {
+		ERR("Disabling UST global channel with NULL values");
+		ret = -1;
+		goto error;
+	}
+
+	DBG2("UST app disabling channel %s from global domain for session uid %d",
+			uchan->name, usess->uid);
+
+	rcu_read_lock();
+
+	/* For every registered applications */
+	cds_lfht_for_each_entry(ust_app_ht, &iter, app, node) {
+		ua_sess = lookup_session_by_app(usess, app);
+		if (ua_sess == NULL) {
+			continue;
+		}
+
+		/* Get channel */
+		ua_chan_node = hashtable_lookup(ua_sess->channels,
+				(void *)uchan->name, strlen(uchan->name), &iter);
+		/* If the session if found for the app, the channel must be there */
+		assert(ua_chan_node);
+
+		ua_chan = caa_container_of(ua_chan_node, struct ust_app_channel, node);
+		/* The channel must not be already disabled */
+		assert(ua_chan->enabled == 1);
+
+		/* Disable channel onto application */
+		ret = disable_ust_app_channel(ua_sess, ua_chan, app);
+		if (ret < 0) {
+			/* XXX: We might want to report this error at some point... */
+			continue;
+		}
+	}
 
-	rcu_read_lock();
-	count = hashtable_get_count(ust_app_ht);
 	rcu_read_unlock();
 
-	return count;
+error:
+	return ret;
 }
 
 /*
- * Fill events array with all events name of all registered apps.
+ * For a specific UST session, enable the channel for all registered apps.
  */
-int ust_app_list_events(struct lttng_event **events)
+int ust_app_enable_channel_glb(struct ltt_ust_session *usess,
+		struct ltt_ust_channel *uchan)
 {
-	int ret, handle;
-	size_t nbmem, count = 0;
+	int ret = 0;
 	struct cds_lfht_iter iter;
 	struct ust_app *app;
-	struct lttng_event *tmp;
+	struct ust_app_session *ua_sess;
 
-	nbmem = UST_APP_EVENT_LIST_SIZE;
-	tmp = zmalloc(nbmem * sizeof(struct lttng_event));
-	if (tmp == NULL) {
-		PERROR("zmalloc ust app events");
-		ret = -ENOMEM;
+	if (usess == NULL || uchan == NULL) {
+		ERR("Adding UST global channel to NULL values");
+		ret = -1;
 		goto error;
 	}
 
+	DBG2("UST app enabling channel %s to global domain for session uid %d",
+			uchan->name, usess->uid);
+
 	rcu_read_lock();
 
+	/* For every registered applications */
 	cds_lfht_for_each_entry(ust_app_ht, &iter, app, node) {
-		handle = ustctl_tracepoint_list(app->key.sock);
-		if (handle < 0) {
-			ERR("UST app list events getting handle failed for app pid %d",
-					app->key.pid);
+		ua_sess = lookup_session_by_app(usess, app);
+		if (ua_sess == NULL) {
 			continue;
 		}
 
-		while ((ret = ustctl_tracepoint_list_get(app->key.sock, handle,
-						tmp[count].name)) != -ENOENT) {
-			if (count > nbmem) {
-				DBG2("Reallocating event list from %zu to %zu bytes", nbmem,
-						nbmem + UST_APP_EVENT_LIST_SIZE);
-				nbmem += UST_APP_EVENT_LIST_SIZE;
-				tmp = realloc(tmp, nbmem);
-				if (tmp == NULL) {
-					PERROR("realloc ust app events");
-					ret = -ENOMEM;
-					goto rcu_error;
-				}
-			}
-
-			tmp[count].type = LTTNG_UST_TRACEPOINT;
-			tmp[count].pid = app->key.pid;
-			tmp[count].enabled = -1;
-			count++;
+		/* Enable channel onto application */
+		ret = enable_ust_app_channel(ua_sess, uchan, app);
+		if (ret < 0) {
+			/* XXX: We might want to report this error at some point... */
+			continue;
 		}
 	}
 
-	ret = count;
-	*events = tmp;
-
-	DBG2("UST app list events done (%zu events)", count);
-
-rcu_error:
 	rcu_read_unlock();
+
 error:
 	return ret;
 }
 
 /*
- * Free and clean all traceable apps of the global list.
+ * Disable an event in a channel and for a specific session.
  */
-void ust_app_clean_list(void)
+int ust_app_disable_event_glb(struct ltt_ust_session *usess,
+		struct ltt_ust_channel *uchan, struct ltt_ust_event *uevent)
 {
-	int ret;
-	struct cds_lfht_node *node;
-	struct cds_lfht_iter iter;
+	int ret = 0;
+	struct cds_lfht_iter iter, uiter;
+	struct cds_lfht_node *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;
 
-	DBG2("UST app cleaning registered apps hash table");
+	DBG("UST app disabling event %s for all apps in channel "
+			"%s for session uid %d", uevent->attr.name, uchan->name, usess->uid);
 
 	rcu_read_lock();
 
-	cds_lfht_for_each(ust_app_ht, &iter, node) {
-		app = caa_container_of(node, struct ust_app, node);
+	/* For all registered applications */
+	cds_lfht_for_each_entry(ust_app_ht, &iter, app, node) {
+		ua_sess = lookup_session_by_app(usess, app);
+		if (ua_sess == NULL) {
+			/* Next app */
+			continue;
+		}
+
+		/* Lookup channel in the ust app session */
+		ua_chan_node = hashtable_lookup(ua_sess->channels,
+				(void *)uchan->name, strlen(uchan->name), &uiter);
+		if (ua_chan_node == NULL) {
+			DBG2("Channel %s not found in session uid %d for app pid %d."
+					"Skipping", uchan->name, usess->uid, app->key.pid);
+			continue;
+		}
+		ua_chan = caa_container_of(ua_chan_node, struct ust_app_channel, node);
 
-		ret = hashtable_del(ust_app_ht, &iter);
-		if (!ret) {
-			call_rcu(&node->head, delete_ust_app_rcu);
+		ua_event_node = hashtable_lookup(ua_chan->events,
+				(void *)uevent->attr.name, strlen(uevent->attr.name), &uiter);
+		if (ua_event_node == NULL) {
+			DBG2("Event %s not found in channel %s for app pid %d."
+					"Skipping", uevent->attr.name, uchan->name, app->key.pid);
+			continue;
 		}
-	}
+		ua_event = caa_container_of(ua_event_node, struct ust_app_event, node);
 
-	hashtable_destroy(ust_app_ht);
-	hashtable_destroy(ust_app_sock_key_map);
+		ret = disable_ust_app_event(ua_sess, ua_chan, ua_event, app);
+		if (ret < 0) {
+			/* XXX: Report error someday... */
+			continue;
+		}
+	}
 
 	rcu_read_unlock();
+
+	return ret;
 }
 
 /*
- * Init UST app hash table.
+ * For a specific UST session and UST channel, the event for all
+ * registered apps.
  */
-void ust_app_ht_alloc(void)
+int ust_app_disable_all_event_glb(struct ltt_ust_session *usess,
+		struct ltt_ust_channel *uchan)
 {
-	ust_app_ht = hashtable_new(0);
-	ust_app_sock_key_map = hashtable_new(0);
+	int ret = 0;
+	struct cds_lfht_iter iter, uiter;
+	struct cds_lfht_node *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 uid %d", uchan->name, usess->uid);
+
+	rcu_read_lock();
+
+	/* For all registered applications */
+	cds_lfht_for_each_entry(ust_app_ht, &iter, app, node) {
+		ua_sess = lookup_session_by_app(usess, app);
+		/* If ua_sess is NULL, there is a code flow error */
+		assert(ua_sess);
+
+		/* Lookup channel in the ust app session */
+		ua_chan_node = hashtable_lookup(ua_sess->channels, (void *)uchan->name,
+				strlen(uchan->name), &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, &uiter, ua_event, node) {
+			ret = disable_ust_app_event(ua_sess, ua_chan, 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.
  */
-int ust_app_create_channel_all(struct ltt_ust_session *usess,
+int ust_app_create_channel_glb(struct ltt_ust_session *usess,
 		struct ltt_ust_channel *uchan)
 {
 	int ret = 0;
@@ -1053,7 +1679,11 @@ int ust_app_create_channel_all(struct ltt_ust_session *usess,
 
 	/* For every registered applications */
 	cds_lfht_for_each_entry(ust_app_ht, &iter, app, node) {
-		/* Create session on the tracer side and add it to app session HT */
+		/*
+		 * Create session on the tracer side and add it to app session HT. Note
+		 * 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) {
 			continue;
@@ -1073,48 +1703,106 @@ error:
 }
 
 /*
- * For a specific UST session and UST channel, create the event for all
- * registered apps.
+ * Enable event for a specific session and channel on the tracer.
  */
-int ust_app_create_event_all(struct ltt_ust_session *usess,
+int ust_app_enable_event_glb(struct ltt_ust_session *usess,
 		struct ltt_ust_channel *uchan, struct ltt_ust_event *uevent)
 {
 	int ret = 0;
-	struct cds_lfht_iter iter;
-	struct cds_lfht_node *ua_chan_node;
+	struct cds_lfht_iter iter, uiter;
+	struct cds_lfht_node *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 creating event %s for all apps for session uid %d",
+	DBG("UST app enabling event %s for all apps for session uid %d",
 			uevent->attr.name, usess->uid);
 
+	/*
+	 * NOTE: At this point, this function is called only if the session and
+	 * channel passed are already created for all apps. and enabled on the
+	 * tracer also.
+	 */
+
 	rcu_read_lock();
 
 	/* For all registered applications */
 	cds_lfht_for_each_entry(ust_app_ht, &iter, app, node) {
-		struct cds_lfht_iter uiter;
+		ua_sess = lookup_session_by_app(usess, app);
+		/* If ua_sess is NULL, there is a code flow error */
+		assert(ua_sess);
 
-		/* Create session on the tracer side and add it to app session HT */
-		ua_sess = create_ust_app_session(usess, app);
-		if (ua_sess == NULL) {
+		/* Lookup channel in the ust app session */
+		ua_chan_node = hashtable_lookup(ua_sess->channels, (void *)uchan->name,
+				strlen(uchan->name), &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);
+
+		ua_event_node = hashtable_lookup(ua_sess->channels,
+				(void*)uevent->attr.name, strlen(uevent->attr.name), &uiter);
+		if (ua_event_node == NULL) {
+			DBG3("UST app enable event %s not found. Skipping app",
+					uevent->attr.name);
 			continue;
 		}
+		ua_event = caa_container_of(ua_event_node, struct ust_app_event, node);
 
-		/* Lookup channel in the ust app session */
-		ua_chan_node = hashtable_lookup(ua_sess->channels,
-				(void *)uchan->name, strlen(uchan->name),
-				&uiter);
-		if (ua_chan_node == NULL) {
-			ERR("Channel %s not found in session uid %d. Skipping",
-					uchan->name, usess->uid);
+		ret = enable_ust_app_event(ua_sess, ua_event, app);
+		if (ret < 0) {
+			/* XXX: Report error someday... */
 			continue;
 		}
+	}
+
+	rcu_read_unlock();
+
+	return ret;
+}
+
+/*
+ * For a specific existing UST session and UST channel, creates the event for
+ * all registered apps.
+ */
+int ust_app_create_event_glb(struct ltt_ust_session *usess,
+		struct ltt_ust_channel *uchan, struct ltt_ust_event *uevent)
+{
+	int ret = 0;
+	struct cds_lfht_iter iter, uiter;
+	struct cds_lfht_node *ua_chan_node;
+	struct ust_app *app;
+	struct ust_app_session *ua_sess;
+	struct ust_app_channel *ua_chan;
+
+	DBG("UST app creating event %s for all apps for session uid %d",
+			uevent->attr.name, usess->uid);
+
+	/*
+	 * NOTE: At this point, this function is called only if the session and
+	 * channel passed are already created for all apps. and enabled on the
+	 * tracer also.
+	 */
+
+	rcu_read_lock();
+
+	/* For all registered applications */
+	cds_lfht_for_each_entry(ust_app_ht, &iter, app, node) {
+		ua_sess = lookup_session_by_app(usess, app);
+		/* If ua_sess is NULL, there is a code flow error */
+		assert(ua_sess);
+
+		/* Lookup channel in the ust app session */
+		ua_chan_node = hashtable_lookup(ua_sess->channels, (void *)uchan->name,
+				strlen(uchan->name), &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);
 
-		ua_event = create_ust_app_event(ua_sess, ua_chan, uevent, app);
-		if (ua_event == NULL) {
+		ret = create_ust_app_event(ua_sess, ua_chan, uevent, app);
+		if (ret < 0) {
 			continue;
 		}
 	}
@@ -1142,7 +1830,6 @@ int ust_app_start_trace(struct ltt_ust_session *usess, struct ust_app *app)
 
 	ua_sess = lookup_session_by_app(usess, app);
 	if (ua_sess == NULL) {
-		/* Only malloc can failed so something is really wrong */
 		goto error_rcu_unlock;
 	}
 
@@ -1290,6 +1977,7 @@ int ust_app_destroy_trace(struct ltt_ust_session *usess, struct ust_app *app)
 	struct lttng_ust_object_data obj;
 	struct cds_lfht_iter iter;
 	struct cds_lfht_node *node;
+	int ret;
 
 	DBG("Destroy tracing for ust app pid %d", app->key.pid);
 
@@ -1302,7 +1990,8 @@ int ust_app_destroy_trace(struct ltt_ust_session *usess, struct ust_app *app)
 		goto error_rcu_unlock;
 	}
 	ua_sess = caa_container_of(node, struct ust_app_session, node);
-	hashtable_del(app->sessions, &iter);
+	ret = hashtable_del(app->sessions, &iter);
+	assert(!ret);
 	delete_ust_app_session(app->key.sock, ua_sess);
 	obj.handle = ua_sess->handle;
 	obj.shm_fd = -1;
@@ -1468,3 +2157,99 @@ error:
 	rcu_read_unlock();
 	return;
 }
+
+/*
+ * Add context to a specific channel for global UST domain.
+ */
+int ust_app_add_ctx_channel_glb(struct ltt_ust_session *usess,
+		struct ltt_ust_channel *uchan, struct ltt_ust_context *uctx)
+{
+	int ret = 0;
+	struct cds_lfht_node *ua_chan_node;
+	struct cds_lfht_iter iter, uiter;
+	struct ust_app_channel *ua_chan = NULL;
+	struct ust_app_session *ua_sess;
+	struct ust_app *app;
+
+	rcu_read_lock();
+
+	cds_lfht_for_each_entry(ust_app_ht, &iter, app, node) {
+		ua_sess = lookup_session_by_app(usess, app);
+		if (ua_sess == NULL) {
+			continue;
+		}
+
+		/* Lookup channel in the ust app session */
+		ua_chan_node = hashtable_lookup(ua_sess->channels,
+				(void *)uchan->name, strlen(uchan->name), &uiter);
+		if (ua_chan_node == NULL) {
+			continue;
+		}
+		ua_chan = caa_container_of(ua_chan_node, struct ust_app_channel,
+				node);
+
+		ret = create_ust_app_channel_context(ua_sess, ua_chan, &uctx->ctx, app);
+		if (ret < 0) {
+			continue;
+		}
+	}
+
+	/* Add ltt UST context node to ltt UST channel */
+	hashtable_add_unique(uchan->ctx, &uctx->node);
+
+	rcu_read_unlock();
+	return ret;
+}
+
+/*
+ * Add context to a specific event in a channel for global UST domain.
+ */
+int ust_app_add_ctx_event_glb(struct ltt_ust_session *usess,
+		struct ltt_ust_channel *uchan, struct ltt_ust_event *uevent,
+		struct ltt_ust_context *uctx)
+{
+	int ret = 0;
+	struct cds_lfht_node *ua_chan_node, *ua_event_node;
+	struct cds_lfht_iter iter, uiter;
+	struct ust_app_session *ua_sess;
+	struct ust_app_event *ua_event;
+	struct ust_app_channel *ua_chan = NULL;
+	struct ust_app *app;
+
+	rcu_read_lock();
+
+	cds_lfht_for_each_entry(ust_app_ht, &iter, app, node) {
+		ua_sess = lookup_session_by_app(usess, app);
+		if (ua_sess == NULL) {
+			continue;
+		}
+
+		/* Lookup channel in the ust app session */
+		ua_chan_node = hashtable_lookup(ua_sess->channels,
+				(void *)uchan->name, strlen(uchan->name), &uiter);
+		if (ua_chan_node == NULL) {
+			continue;
+		}
+		ua_chan = caa_container_of(ua_chan_node, struct ust_app_channel,
+				node);
+
+		ua_event_node = hashtable_lookup(ua_chan->events,
+				(void *)uevent->attr.name, strlen(uevent->attr.name), &uiter);
+		if (ua_event_node == NULL) {
+			continue;
+		}
+		ua_event = caa_container_of(ua_event_node, struct ust_app_event,
+				node);
+
+		ret = create_ust_app_event_context(ua_sess, ua_event, &uctx->ctx, app);
+		if (ret < 0) {
+			continue;
+		}
+	}
+
+	/* Add ltt UST context node to ltt UST event */
+	hashtable_add_unique(uevent->ctx, &uctx->node);
+
+	rcu_read_unlock();
+	return ret;
+}