X-Git-Url: https://git.lttng.org/?p=lttng-tools.git;a=blobdiff_plain;f=ltt-sessiond%2Fust-app.c;h=489bd8b2fe59f8bf8b53f5262e6805cdeaa3f3a3;hp=ea062557e56cf60ee471f62921bcdd1082a2e1ee;hb=1316184615e422526ef4fae68f980443414969c1;hpb=56fff0907d3a752030f384e6037d16ea7978de71

diff --git a/ltt-sessiond/ust-app.c b/ltt-sessiond/ust-app.c
index ea062557e..489bd8b2f 100644
--- a/ltt-sessiond/ust-app.c
+++ b/ltt-sessiond/ust-app.c
@@ -25,103 +25,144 @@
 #include <unistd.h>
 
 #include <lttngerr.h>
+#include <lttng-share.h>
 
+#include "hashtable.h"
 #include "ust-app.h"
-
-/* Init ust traceable application's list */
-static struct ust_app_list ust_app_list = {
-	.head = CDS_LIST_HEAD_INIT(ust_app_list.head),
-	.lock = PTHREAD_MUTEX_INITIALIZER,
-	.count = 0,
-};
-
-/*
- * Add a traceable application structure to the global list.
- */
-static void add_app_to_list(struct ust_app *lta)
-{
-	cds_list_add(&lta->list, &ust_app_list.head);
-	ust_app_list.count++;
-}
+#include "../hashtable/hash.h"
+#include "ust-ctl.h"
+#include "ust-consumer.h"
 
 /*
  * Delete a traceable application structure from the global list.
  */
-static void del_app_from_list(struct ust_app *lta)
+static void delete_ust_app(struct ust_app *lta)
 {
-	struct ltt_ust_channel *chan;
+	int ret;
+	struct cds_lfht_node *node;
+	struct cds_lfht_iter iter;
 
-	cds_list_del(&lta->list);
-	/* Sanity check */
-	if (ust_app_list.count > 0) {
-		ust_app_list.count--;
-	}
+	rcu_read_lock();
 
-	cds_list_for_each_entry(chan, &lta->channels.head, list) {
-		trace_ust_destroy_channel(chan);
-	}
-}
+	free(lta->sessions);
+	close(lta->key.sock);
 
-/*
- * Iterate over the traceable apps list and return a pointer or NULL if not
- * found.
- */
-static struct ust_app *find_app_by_sock(int sock)
-{
-	struct ust_app *iter;
+	/* Remove from apps hash table */
+	node = hashtable_lookup(ust_app_ht,
+			(void *) ((unsigned long) lta->key.pid), sizeof(void *), &iter);
+	if (node == NULL) {
+		ERR("UST app pid %d not found in hash table", lta->key.pid);
+	} else {
+		ret = hashtable_del(ust_app_ht, &iter);
+		if (ret) {
+			ERR("UST app unable to delete app %d from hash table",
+					lta->key.pid);
+		} else {
+			DBG2("UST app pid %d deleted", lta->key.pid);
+		}
+	}
 
-	cds_list_for_each_entry(iter, &ust_app_list.head, list) {
-		if (iter->sock == sock) {
-			/* Found */
-			return iter;
+	/* Remove from key hash table */
+	node = hashtable_lookup(ust_app_sock_key_map,
+			(void *) ((unsigned long) lta->key.sock), sizeof(void *), &iter);
+	if (node == NULL) {
+		ERR("UST app key %d not found in key hash table", lta->key.sock);
+	} else {
+		ret = hashtable_del(ust_app_sock_key_map, &iter);
+		if (ret) {
+			ERR("UST app unable to delete app sock %d from key hash table",
+					lta->key.sock);
+		} else {
+			DBG2("UST app pair sock %d key %d deleted",
+					lta->key.sock, lta->key.pid);
 		}
 	}
 
-	return NULL;
+	free(lta);
+
+	rcu_read_unlock();
 }
 
 /*
- * Return pointer to traceable apps list.
+ * URCU intermediate call to delete an UST app.
  */
-struct ust_app_list *ust_app_get_list(void)
+static void delete_ust_app_rcu(struct rcu_head *head)
 {
-	return &ust_app_list;
+	struct cds_lfht_node *node =
+		caa_container_of(head, struct cds_lfht_node, head);
+	struct ust_app *app =
+		caa_container_of(node, struct ust_app, node);
+
+	delete_ust_app(app);
 }
 
 /*
- * Acquire traceable apps list lock.
+ * Find an ust_app using the sock and return it.
  */
-void ust_app_lock_list(void)
+static struct ust_app *find_app_by_sock(int sock)
 {
-	pthread_mutex_lock(&ust_app_list.lock);
+	struct cds_lfht_node *node;
+	struct ust_app_key *key;
+	struct cds_lfht_iter iter;
+
+	rcu_read_lock();
+
+	node = hashtable_lookup(ust_app_sock_key_map,
+			(void *)((unsigned long) sock), sizeof(void *), &iter);
+	if (node == NULL) {
+		DBG2("UST app find by sock %d key not found", sock);
+		rcu_read_unlock();
+		goto error;
+	}
+
+	key = caa_container_of(node, struct ust_app_key, node);
+
+	node = hashtable_lookup(ust_app_ht,
+			(void *)((unsigned long) key->pid), sizeof(void *), &iter);
+	if (node == NULL) {
+		DBG2("UST app find by sock %d not found", sock);
+		rcu_read_unlock();
+		goto error;
+	}
+	rcu_read_unlock();
+
+	return caa_container_of(node, struct ust_app, node);
+
+error:
+	return NULL;
 }
 
 /*
- * Release traceable apps list lock.
+ * Return pointer to traceable apps list.
  */
-void ust_app_unlock_list(void)
+struct cds_lfht *ust_app_get_ht(void)
 {
-	pthread_mutex_unlock(&ust_app_list.lock);
+	return ust_app_ht;
 }
 
 /*
- * Iterate over the traceable apps list and return a pointer or NULL if not
- * found.
+ * Return ust app pointer or NULL if not found.
  */
-struct ust_app *ust_app_get_by_pid(pid_t pid)
+struct ust_app *ust_app_find_by_pid(pid_t pid)
 {
-	struct ust_app *iter;
+	struct cds_lfht_node *node;
+	struct cds_lfht_iter iter;
 
-	cds_list_for_each_entry(iter, &ust_app_list.head, list) {
-		if (iter->pid == pid) {
-			/* Found */
-			DBG2("Found traceable app by pid %d", pid);
-			return iter;
-		}
+	rcu_read_lock();
+	node = hashtable_lookup(ust_app_ht,
+			(void *)((unsigned long) pid), sizeof(void *), &iter);
+	if (node == NULL) {
+		rcu_read_unlock();
+		DBG2("UST app no found with pid %d", pid);
+		goto error;
 	}
+	rcu_read_unlock();
+
+	DBG2("Found UST app by pid %d", pid);
 
-	DBG2("Traceable app with pid %d not found", pid);
+	return caa_container_of(node, struct ust_app, node);
 
+error:
 	return NULL;
 }
 
@@ -137,28 +178,37 @@ int ust_app_register(struct ust_register_msg *msg, int sock)
 
 	lta = malloc(sizeof(struct ust_app));
 	if (lta == NULL) {
-		perror("malloc");
+		PERROR("malloc");
 		return -ENOMEM;
 	}
 
 	lta->uid = msg->uid;
 	lta->gid = msg->gid;
-	lta->pid = msg->pid;
+	lta->key.pid = msg->pid;
 	lta->ppid = msg->ppid;
 	lta->v_major = msg->major;
 	lta->v_minor = msg->minor;
-	lta->sock = sock;
+	lta->key.sock = sock;
 	strncpy(lta->name, msg->name, sizeof(lta->name));
 	lta->name[16] = '\0';
-	CDS_INIT_LIST_HEAD(&lta->channels.head);
+	hashtable_node_init(&lta->node, (void *)((unsigned long)lta->key.pid),
+			sizeof(void *));
+
+	/* Session hashtable */
+	lta->sessions = hashtable_new(0);
 
-	ust_app_lock_list();
-	add_app_to_list(lta);
-	ust_app_unlock_list();
+	/* Set sock key map */
+	hashtable_node_init(&lta->key.node, (void *)((unsigned long)lta->key.sock),
+			sizeof(void *));
+
+	rcu_read_lock();
+	hashtable_add_unique(ust_app_ht, &lta->node);
+	hashtable_add_unique(ust_app_sock_key_map, &lta->key.node);
+	rcu_read_unlock();
 
 	DBG("App registered with pid:%d ppid:%d uid:%d gid:%d sock:%d name:%s"
-			" (version %d.%d)", lta->pid, lta->ppid, lta->uid, lta->gid,
-			lta->sock, lta->name, lta->v_major, lta->v_minor);
+			" (version %d.%d)", lta->key.pid, lta->ppid, lta->uid, lta->gid,
+			lta->key.sock, lta->name, lta->v_major, lta->v_minor);
 
 	return 0;
 }
@@ -173,27 +223,26 @@ void ust_app_unregister(int sock)
 {
 	struct ust_app *lta;
 
-	ust_app_lock_list();
+	DBG2("UST app unregistering sock %d", sock);
+
 	lta = find_app_by_sock(sock);
 	if (lta) {
-		DBG("PID %d unregistered with sock %d", lta->pid, sock);
-		del_app_from_list(lta);
-		close(lta->sock);
-		free(lta);
+		DBG("PID %d unregistering with sock %d", lta->key.pid, sock);
+		/* FIXME: Better use a call_rcu here ? */
+		delete_ust_app(lta);
 	}
-	ust_app_unlock_list();
 }
 
 /*
  * Return traceable_app_count
  */
-unsigned int ust_app_list_count(void)
+unsigned long ust_app_list_count(void)
 {
-	unsigned int count;
+	unsigned long count;
 
-	ust_app_lock_list();
-	count = ust_app_list.count;
-	ust_app_unlock_list();
+	rcu_read_lock();
+	count = hashtable_get_count(ust_app_ht);
+	rcu_read_unlock();
 
 	return count;
 }
@@ -203,15 +252,580 @@ unsigned int ust_app_list_count(void)
  */
 void ust_app_clean_list(void)
 {
-	struct ust_app *iter, *tmp;
+	int ret;
+	struct cds_lfht_node *node;
+	struct cds_lfht_iter iter;
+
+	DBG2("UST app clean hash table");
+
+	rcu_read_lock();
+
+	hashtable_get_first(ust_app_ht, &iter);
+	while ((node = hashtable_iter_get_node(&iter)) != NULL) {
+		ret = hashtable_del(ust_app_ht, &iter);
+		if (!ret) {
+			call_rcu(&node->head, delete_ust_app_rcu);
+		}
+		hashtable_get_next(ust_app_ht, &iter);
+	}
+
+	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);
+}
+
+/*
+ * Alloc new UST app session.
+ */
+static struct ust_app_session *alloc_app_session(void)
+{
+	struct ust_app_session *ua_sess;
+
+	ua_sess = zmalloc(sizeof(struct ust_app_session));
+	if (ua_sess == NULL) {
+		PERROR("malloc");
+		goto error;
+	}
+
+	ua_sess->enabled = 0;
+	ua_sess->handle = -1;
+	ua_sess->channels = hashtable_new_str(0);
+	ua_sess->metadata = NULL;
+	ua_sess->obj = NULL;
+
+	return ua_sess;
+
+error:
+	return NULL;
+}
+
+static struct ust_app_channel *alloc_app_channel(char *name)
+{
+	struct ust_app_channel *ua_chan;
+
+	ua_chan = zmalloc(sizeof(struct ust_app_channel));
+	if (ua_chan == NULL) {
+		PERROR("malloc");
+		goto error;
+	}
+
+	strncpy(ua_chan->name, name, sizeof(ua_chan->name));
+	ua_chan->name[sizeof(ua_chan->name) - 1] = '\0';
+	ua_chan->enabled = 0;
+	ua_chan->handle = -1;
+	ua_chan->obj = NULL;
+	ua_chan->ctx = hashtable_new(0);
+	ua_chan->streams = hashtable_new(0);
+	ua_chan->events = hashtable_new_str(0);
+	hashtable_node_init(&ua_chan->node, (void *) ua_chan->name,
+			strlen(ua_chan->name));
+
+	DBG3("UST app channel %s allocated", ua_chan->name);
+
+	return ua_chan;
+
+error:
+	return NULL;
+}
+
+static struct ust_app_event *alloc_app_event(char *name)
+{
+	struct ust_app_event *ua_event;
+
+	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));
+
+	DBG3("UST app event %s allocated", ua_event->name);
+
+	return ua_event;
+
+error:
+	return NULL;
+}
+
+static void shallow_copy_event(struct ust_app_event *ua_event,
+		struct ltt_ust_event *uevent)
+{
+	strncpy(ua_event->name, uevent->attr.name, sizeof(ua_event->name));
+	ua_event->name[sizeof(ua_event->name) - 1] = '\0';
+
+	/* TODO: support copy context */
+}
+
+static void shallow_copy_channel(struct ust_app_channel *ua_chan,
+		struct ltt_ust_channel *uchan)
+{
+	struct cds_lfht_iter iter;
+	struct cds_lfht_node *node, *ua_event_node;
+	struct ltt_ust_event *uevent;
+	struct ust_app_event *ua_event;
+
+	DBG2("Shallow copy of UST app channel %s", ua_chan->name);
+
+	strncpy(ua_chan->name, uchan->name, sizeof(ua_chan->name));
+	ua_chan->name[sizeof(ua_chan->name) - 1] = '\0';
+
+	/* TODO: support copy context */
+
+	hashtable_get_first(uchan->events, &iter);
+	while ((node = hashtable_iter_get_node(&iter)) != NULL) {
+		uevent = caa_container_of(node, struct ltt_ust_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 event %s not found on shallow copy channel",
+					uevent->attr.name);
+			ua_event = alloc_app_event(uevent->attr.name);
+			if (ua_event == NULL) {
+				continue;
+			}
+			hashtable_add_unique(ua_chan->events, &ua_event->node);
+		} else {
+			ua_event = caa_container_of(node, struct ust_app_event, node);
+		}
+
+		shallow_copy_event(ua_event, uevent);
+
+		/* Get next UST events */
+		hashtable_get_next(uchan->events, &iter);
+	}
+
+	DBG3("Shallow copy channel done");
+}
+
+static void shallow_copy_session(struct ust_app_session *ua_sess,
+		struct ltt_ust_session *usess)
+{
+	struct cds_lfht_node *node, *ua_chan_node;
+	struct cds_lfht_iter iter;
+	struct ltt_ust_channel *uchan;
+	struct ust_app_channel *ua_chan;
+
+	DBG2("Shallow copy of session handle");
+
+	ua_sess->uid = usess->uid;
+
+	/* TODO: support all UST domain */
+
+	/* Iterate over all channels in global domain. */
+	hashtable_get_first(usess->domain_global.channels, &iter);
+	while ((node = hashtable_iter_get_node(&iter)) != NULL) {
+		uchan = caa_container_of(node, struct ltt_ust_channel, node);
+
+		ua_chan_node = hashtable_lookup(ua_sess->channels,
+				(void *) uchan->name, strlen(uchan->name), &iter);
+		if (ua_chan_node == NULL) {
+			DBG2("Channel %s not found on shallow session copy, creating it",
+					uchan->name);
+			ua_chan = alloc_app_channel(uchan->name);
+			if (ua_chan == NULL) {
+				/* malloc failed... continuing */
+				continue;
+			}
+			hashtable_add_unique(ua_sess->channels, &ua_chan->node);
+		} else {
+			ua_chan = caa_container_of(node, struct ust_app_channel, node);
+		}
+
+		shallow_copy_channel(ua_chan, uchan);
+
+		/* Next item in hash table */
+		hashtable_get_next(usess->domain_global.channels, &iter);
+	}
+}
+
+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;
+
+	/* Get right UST app session from app */
+	node = hashtable_lookup(app->sessions,
+			(void *) ((unsigned long) usess->uid),
+			sizeof(void *), &iter);
+	if (node == NULL) {
+		goto error;
+	}
+
+	return caa_container_of(node, struct ust_app_session, node);
+
+error:
+	return NULL;
+}
+
+int ust_app_add_channel(struct ltt_ust_session *usess,
+		struct ltt_ust_channel *uchan)
+{
+	int ret = 0;
+	struct cds_lfht_iter iter;
+	struct cds_lfht_node *node, *ua_chan_node;
+	struct ust_app *app;
+	struct ust_app_session *ua_sess;
+	struct ust_app_channel *ua_chan;
+
+	DBG2("UST app adding channel %s to global domain for session uid %d",
+			uchan->name, usess->uid);
+
+	rcu_read_lock();
+	hashtable_get_first(ust_app_ht, &iter);
+	while ((node = hashtable_iter_get_node(&iter)) != NULL) {
+		app = caa_container_of(node, struct ust_app, node);
+
+		ua_sess = lookup_session_by_app(usess, app);
+		if (ua_sess == NULL) {
+			DBG2("UST app pid: %d session uid %d not found, creating one",
+					app->key.pid, usess->uid);
+			ua_sess = alloc_app_session();
+			if (ua_sess == NULL) {
+				/* Only malloc can failed so something is really wrong */
+				goto next;
+			}
+			shallow_copy_session(ua_sess, usess);
+		}
+
+		if (ua_sess->handle == -1) {
+			ret = ustctl_create_session(app->key.sock);
+			if (ret < 0) {
+				DBG("Error creating session for app pid %d, sock %d",
+						app->key.pid, app->key.sock);
+				/* TODO: free() ua_sess */
+				goto next;
+			}
+
+			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);
+		}
+
+		/* Lookup channel in the ust app session */
+		ua_chan_node = hashtable_lookup(ua_sess->channels,
+				(void *) uchan->name, strlen(uchan->name), &iter);
+		if (ua_chan_node == NULL) {
+			ERR("Channel suppose to be present with the above shallow "
+					"session copy. Continuing...");
+			goto next;
+		}
+
+		ua_chan = caa_container_of(ua_chan_node, struct ust_app_channel, node);
+
+		/* TODO: remove cast and use lttng-ust-abi.h */
+		ret = ustctl_create_channel(app->key.sock, ua_sess->handle,
+				(struct lttng_ust_channel_attr *)&uchan->attr, &ua_chan->obj);
+		if (ret < 0) {
+			DBG("Error creating channel %s for app (pid: %d, sock: %d) "
+					"and session handle %d with ret %d",
+					uchan->name, app->key.pid, app->key.sock,
+					ua_sess->handle, ret);
+			goto next;
+		}
+
+		ua_chan->handle = ua_chan->obj->handle;
+		ua_chan->attr.shm_fd = ua_chan->obj->shm_fd;
+		ua_chan->attr.wait_fd = ua_chan->obj->wait_fd;
+		ua_chan->attr.memory_map_size = ua_chan->obj->memory_map_size;
+
+		DBG2("Channel %s UST create successfully for pid:%d and sock:%d",
+				uchan->name, app->key.pid, app->key.sock);
+
+next:
+		/* Next applications */
+		hashtable_get_next(ust_app_ht, &iter);
+	}
+	rcu_read_unlock();
+
+	return ret;
+}
+
+int ust_app_add_event(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 *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;
+	struct lttng_ust_event ltt_uevent;
+	struct lttng_ust_object_data *obj_event;
+
+	DBG2("UST app adding event %s to global domain for session uid %d",
+			uevent->attr.name, usess->uid);
+
+	rcu_read_lock();
+	hashtable_get_first(ust_app_ht, &iter);
+	while ((node = hashtable_iter_get_node(&iter)) != NULL) {
+		app = caa_container_of(node, struct ust_app, node);
+
+		ua_sess = lookup_session_by_app(usess, app);
+		if (ua_sess == NULL) {
+			DBG2("UST app (pid: %d, sock: %d) session not found, creating one",
+					app->key.pid, app->key.sock);
+			ua_sess = alloc_app_session();
+			if (ua_sess == NULL) {
+				/* Only malloc can failed so something is really wrong */
+				goto next;
+			}
+			shallow_copy_session(ua_sess, usess);
+		}
+
+		if (ua_sess->handle == -1) {
+			ret = ustctl_create_session(app->key.sock);
+			if (ret < 0) {
+				DBG("Error creating session for app pid %d, sock %d",
+						app->key.pid, app->key.sock);
+				/* TODO: free() ua_sess */
+				goto next;
+			}
+
+			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);
+		}
+
+		/* Lookup channel in the ust app session */
+		ua_chan_node = hashtable_lookup(ua_sess->channels,
+				(void *) uchan->name, strlen(uchan->name), &iter);
+		if (ua_chan_node == NULL) {
+			ERR("Channel suppose to be present with the above shallow "
+					"session copy. Continuing...");
+			goto next;
+		}
+
+		ua_chan = caa_container_of(ua_chan_node, struct ust_app_channel, node);
+
+		/* Prepare lttng ust event */
+		strncpy(ltt_uevent.name, uevent->attr.name, sizeof(ltt_uevent.name));
+		ltt_uevent.name[sizeof(ltt_uevent.name) - 1] = '\0';
+		/* TODO: adjust to other instrumentation types */
+		ltt_uevent.instrumentation = LTTNG_UST_TRACEPOINT;
+
+		/* 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 one", uevent->attr.name);
+			/* Does not exist so create one */
+			ua_event = alloc_app_event(uevent->attr.name);
+			if (ua_event == NULL) {
+				/* Only malloc can failed so something is really wrong */
+				goto next;
+			}
+
+			shallow_copy_event(ua_event, uevent);
+
+			/* Create UST event on tracer */
+			ret = ustctl_create_event(app->key.sock, &ltt_uevent, ua_chan->obj,
+					&obj_event);
+			if (ret < 0) {
+				ERR("Error ustctl create event %s for app pid: %d with ret %d",
+						uevent->attr.name, app->key.pid, ret);
+				/* TODO: free() ua_event and obj_event */
+				goto next;
+			}
+			ua_event->obj = obj_event;
+			ua_event->handle = obj_event->handle;
+			ua_event->enabled = 1;
+		} else {
+			ua_event = caa_container_of(ua_event_node,
+					struct ust_app_event, node);
+
+			if (ua_event->enabled == 0) {
+				ret = ustctl_enable(app->key.sock, ua_event->obj);
+				if (ret < 0) {
+					ERR("Error ustctl enable event %s for app "
+							"pid: %d with ret %d", uevent->attr.name,
+							app->key.pid, ret);
+					goto next;
+				}
+				ua_event->enabled = 1;
+			}
+		}
+
+		hashtable_add_unique(ua_chan->events, &ua_event->node);
+
+		DBG2("Event %s UST create successfully for pid:%d", uevent->attr.name,
+				app->key.pid);
+
+next:
+		/* Next applications */
+		hashtable_get_next(ust_app_ht, &iter);
+	}
+	rcu_read_unlock();
+
+	return ret;
+}
+
+int ust_app_start_trace(struct ltt_ust_session *usess)
+{
+	int ret = 0;
+	struct cds_lfht_iter iter;
+	struct cds_lfht_node *node, *ua_chan_node;
+	struct ust_app *app;
+	struct ust_app_session *ua_sess;
+	struct ust_app_channel *ua_chan;
+	struct lttng_ust_channel_attr uattr;
+	struct ltt_ust_channel *uchan;
+
+	rcu_read_lock();
+	hashtable_get_first(ust_app_ht, &iter);
+	while ((node = hashtable_iter_get_node(&iter)) != NULL) {
+		app = caa_container_of(node, struct ust_app, node);
+
+		ua_sess = lookup_session_by_app(usess, app);
+		if (ua_sess == NULL) {
+			/* Only malloc can failed so something is really wrong */
+			goto next;
+		}
+
+		if (ua_sess->metadata == NULL) {
+			/* Allocate UST metadata */
+			ua_sess->metadata = trace_ust_create_metadata(usess->pathname);
+			if (ua_sess->metadata == NULL) {
+				ERR("UST app session %d creating metadata failed",
+						ua_sess->handle);
+				goto next;
+			}
+
+			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;
+
+			/* UST tracer metadata creation */
+			ret = ustctl_open_metadata(app->key.sock, ua_sess->handle, &uattr,
+					&ua_sess->metadata->obj);
+			if (ret < 0) {
+				ERR("UST app open metadata failed for app pid:%d",
+						app->key.pid);
+				goto next;
+			}
 
-	/*
-	 * Don't acquire list lock here. This function should be called from
-	 * cleanup() functions meaning that the program will exit.
-	 */
-	cds_list_for_each_entry_safe(iter, tmp, &ust_app_list.head, list) {
-		del_app_from_list(iter);
-		close(iter->sock);
-		free(iter);
+			DBG2("UST metadata opened for app pid %d", app->key.pid);
+		}
+
+		/* Open UST metadata stream */
+		if (ua_sess->metadata->stream_obj == NULL) {
+			ret = ustctl_create_stream(app->key.sock, ua_sess->metadata->obj,
+					&ua_sess->metadata->stream_obj);
+			if (ret < 0) {
+				ERR("UST create metadata stream failed");
+				goto next;
+			}
+
+			ret = snprintf(ua_sess->metadata->pathname, PATH_MAX, "%s/%s",
+					usess->pathname, "metadata");
+			if (ret < 0) {
+				PERROR("asprintf UST create stream");
+				goto next;
+			}
+
+			DBG2("UST metadata stream object created for app pid %d",
+					app->key.pid);
+		}
+
+		/* For each channel */
+		hashtable_get_first(usess->domain_global.channels, &iter);
+		while ((node = hashtable_iter_get_node(&iter)) != NULL) {
+			uchan = caa_container_of(node, struct ltt_ust_channel, node);
+
+			/* Lookup channel in the ust app session */
+			ua_chan_node = hashtable_lookup(ua_sess->channels,
+					(void *) uchan->name, strlen(uchan->name), &iter);
+			if (ua_chan_node == NULL) {
+				ERR("Channel suppose to be present with the above shallow "
+						"session copy. Continuing...");
+				goto next;
+			}
+
+			ua_chan = caa_container_of(ua_chan_node,
+					struct ust_app_channel, node);
+
+			struct ltt_ust_stream *ustream;
+
+			ustream = malloc(sizeof(*ustream));
+			if (ustream == NULL) {
+				goto next_chan;
+			}
+
+			memset(ustream, 0, sizeof(struct ltt_ust_stream));
+
+			ret = ustctl_create_stream(app->key.sock, ua_chan->obj,
+					&ustream->obj);
+			if (ret < 0) {
+				ERR("Creating channel stream failed");
+				goto next_chan;
+			}
+
+			ustream->handle = ustream->obj->handle;
+
+			hashtable_node_init(&ustream->node,
+				(void *)((unsigned long) ustream->handle), sizeof(void *));
+			hashtable_add_unique(ua_chan->streams, &ustream->node);
+
+			ret = snprintf(ustream->pathname, PATH_MAX, "%s/%s_%lu",
+					uchan->pathname, uchan->name,
+					hashtable_get_count(ua_chan->streams));
+			if (ret < 0) {
+				PERROR("asprintf UST create stream");
+				goto next_chan;
+			}
+
+next_chan:
+			/* Next applications */
+			hashtable_get_next(ua_sess->channels, &iter);
+		}
+
+		/* Setup UST consumer socket and send fds to it */
+		printf("WTF HERE: sock: %d\n", usess->consumer_fd);
+		ret = ust_consumer_send_session(usess->consumer_fd, ua_sess);
+		if (ret < 0) {
+			goto next;
+		}
+
+		/* This start the UST tracing */
+		ret = ustctl_start_session(app->key.sock, ua_sess->handle);
+		if (ret < 0) {
+			ERR("Error starting tracing for app pid: %d", app->key.pid);
+			goto next;
+		}
+
+		/* Quiescent wait after starting trace */
+		ustctl_wait_quiescent(app->key.sock);
+next:
+		/* Next applications */
+		hashtable_get_next(ust_app_ht, &iter);
 	}
+	rcu_read_unlock();
+
+	return 0;
 }