From: David Goulet <david.goulet@polymtl.ca>
Date: Mon, 26 Sep 2011 22:33:16 +0000 (-0400)
Subject: Add enable channel support for UST
X-Git-Tag: v2.0-pre14~10
X-Git-Url: https://git.lttng.org/?p=lttng-tools.git;a=commitdiff_plain;h=44d3bd014f6ad217cff7e7c3dfaad76b1927c37b

Add enable channel support for UST

Also improve data structure for UST session control to fit new model
where we will have a list of lttng domain to indentify the ust session.

Signed-off-by: David Goulet <david.goulet@polymtl.ca>
---

diff --git a/ltt-sessiond/channel.c b/ltt-sessiond/channel.c
index ab9bf6c6d..818f6dcfd 100644
--- a/ltt-sessiond/channel.c
+++ b/ltt-sessiond/channel.c
@@ -23,12 +23,13 @@
 
 #include "channel.h"
 #include "kernel-ctl.h"
+#include "ust-ctl.h"
 #include "utils.h"
 
 /*
  * Return allocated channel attributes.
  */
-static struct lttng_channel *init_default_attr(int dom, char *name)
+static struct lttng_channel *init_default_attr(int dom)
 {
 	struct lttng_channel *chan;
 
@@ -38,8 +39,9 @@ static struct lttng_channel *init_default_attr(int dom, char *name)
 		goto error_alloc;
 	}
 
-	if (snprintf(chan->name, sizeof(chan->name), "%s", name) < 0) {
-		perror("snprintf channel name");
+	if (snprintf(chan->name, sizeof(chan->name), "%s",
+				DEFAULT_CHANNEL_NAME) < 0) {
+		perror("snprintf default channel name");
 		goto error;
 	}
 
@@ -53,7 +55,11 @@ static struct lttng_channel *init_default_attr(int dom, char *name)
 			chan->attr.num_subbuf = DEFAULT_KERNEL_CHANNEL_SUBBUF_NUM;
 			chan->attr.output = DEFAULT_KERNEL_CHANNEL_OUTPUT;
 			break;
-			/* TODO: add UST */
+		case LTTNG_DOMAIN_UST_PID:
+			chan->attr.subbuf_size = DEFAULT_UST_CHANNEL_SUBBUF_SIZE;
+			chan->attr.num_subbuf = DEFAULT_UST_CHANNEL_SUBBUF_NUM;
+			chan->attr.output = DEFAULT_UST_CHANNEL_OUTPUT;
+			break;
 		default:
 			goto error;	/* Not implemented */
 	}
@@ -121,14 +127,14 @@ error:
  * Create kernel channel of the kernel session and notify kernel thread.
  */
 int channel_kernel_create(struct ltt_kernel_session *ksession,
-		char *channel_name, struct lttng_channel *chan, int kernel_pipe)
+		struct lttng_channel *chan, int kernel_pipe)
 {
 	int ret;
 	struct lttng_channel *attr = chan;
 
 	/* Creating channel attributes if needed */
 	if (attr == NULL) {
-		attr = init_default_attr(LTTNG_DOMAIN_KERNEL, channel_name);
+		attr = init_default_attr(LTTNG_DOMAIN_KERNEL);
 		if (attr == NULL) {
 			ret = LTTCOMM_FATAL;
 			goto error;
@@ -154,3 +160,77 @@ int channel_kernel_create(struct ltt_kernel_session *ksession,
 error:
 	return ret;
 }
+
+/*
+ * Create UST channel and enable it on the tracer.
+ */
+int channel_ust_create(struct ltt_ust_session *usession,
+		struct lttng_channel *chan, int sock)
+{
+	int ret;
+	struct lttng_channel *attr = chan;
+
+	/* Creating channel attributes if needed */
+	if (attr == NULL) {
+		attr = init_default_attr(LTTNG_DOMAIN_UST_PID);
+		if (attr == NULL) {
+			ret = LTTCOMM_FATAL;
+			goto error;
+		}
+	}
+
+	ret = ustctl_create_channel(sock, usession, attr);
+	if (ret < 0) {
+		ret = LTTCOMM_UST_CHAN_FAIL;
+		goto error;
+	}
+
+	DBG2("Channel %s UST create successfully for sock:%d", attr->name, sock);
+
+	ret = LTTCOMM_OK;
+
+error:
+	return ret;
+}
+
+/*
+ * Enable UST channel on the tracer.
+ */
+int channel_ust_enable(struct ltt_ust_session *usession,
+		struct ltt_ust_channel *uchan, int sock)
+{
+	int ret;
+	ret = LTTCOMM_OK;
+
+	ret = ustctl_enable_channel(sock, usession, uchan);
+	if (ret < 0) {
+		ret = LTTCOMM_UST_CHAN_FAIL;
+		goto error;
+	}
+
+	ret = LTTCOMM_OK;
+
+error:
+	return ret;
+}
+
+/*
+ * Disable UST channel on the tracer.
+ */
+int channel_ust_disable(struct ltt_ust_session *usession,
+		struct ltt_ust_channel *uchan, int sock)
+{
+	int ret;
+	ret = LTTCOMM_OK;
+
+	ret = ustctl_disable_channel(sock, usession, uchan);
+	if (ret < 0) {
+		ret = LTTCOMM_UST_CHAN_FAIL;
+		goto error;
+	}
+
+	ret = LTTCOMM_OK;
+
+error:
+	return ret;
+}
diff --git a/ltt-sessiond/channel.h b/ltt-sessiond/channel.h
index 271721a97..f9a6fbd85 100644
--- a/ltt-sessiond/channel.h
+++ b/ltt-sessiond/channel.h
@@ -21,12 +21,20 @@
 #include <lttng/lttng.h>
 
 #include "trace-kernel.h"
+#include "trace-ust.h"
 
 int channel_kernel_disable(struct ltt_kernel_session *ksession,
 		char *channel_name);
 int channel_kernel_enable(struct ltt_kernel_session *ksession,
 		struct ltt_kernel_channel *kchan);
 int channel_kernel_create(struct ltt_kernel_session *ksession,
-		char *channel_name, struct lttng_channel *chan, int kernel_pipe);
+		struct lttng_channel *chan, int kernel_pipe);
+
+int channel_ust_create(struct ltt_ust_session *usession,
+		struct lttng_channel *chan, int sock);
+int channel_ust_disable(struct ltt_ust_session *usession,
+		struct ltt_ust_channel *uchan, int sock);
+int channel_ust_enable(struct ltt_ust_session *usession,
+		struct ltt_ust_channel *uchan, int sock);
 
 #endif /* _LTT_CHANNEL_H */
diff --git a/ltt-sessiond/main.c b/ltt-sessiond/main.c
index bcb43e19d..825fa4371 100644
--- a/ltt-sessiond/main.c
+++ b/ltt-sessiond/main.c
@@ -1561,15 +1561,30 @@ error:
 /*
  * Create an UST session and add it to the session ust list.
  */
-static int create_ust_session(pid_t pid, struct ltt_session *session)
+static int create_ust_session(struct ltt_session *session,
+		struct lttng_domain *domain)
 {
-	int ret = -1;
+	int ret;
 	struct ltt_ust_session *lus;
+	struct ltt_traceable_app *app;
+
+	switch (domain->type) {
+	case LTTNG_DOMAIN_UST_PID:
+		app = traceable_app_get_by_pid(domain->attr.pid);
+		if (app == NULL) {
+			ret = LTTCOMM_APP_NOT_FOUND;
+			goto error;
+		}
+		break;
+	default:
+		goto error;
+	}
 
 	DBG("Creating UST session");
 
-	lus = trace_ust_create_session(session->path, pid);
+	lus = trace_ust_create_session(session->path, domain->attr.pid, domain);
 	if (lus == NULL) {
+		ret = LTTCOMM_UST_SESS_FAIL;
 		goto error;
 	}
 
@@ -1578,17 +1593,22 @@ static int create_ust_session(pid_t pid, struct ltt_session *session)
 	if (ret < 0) {
 		if (ret != -EEXIST) {
 			ERR("Trace directory creation error");
+			ret = LTTCOMM_UST_SESS_FAIL;
 			goto error;
 		}
 	}
 
 	/* Create session on the UST tracer */
-	ret = ustctl_create_session(lus);
+	ret = ustctl_create_session(app->sock, lus);
 	if (ret < 0) {
+		ret = LTTCOMM_UST_SESS_FAIL;
 		goto error;
 	}
 
-	return 0;
+	cds_list_add(&lus->list, &session->ust_session_list.head);
+	session->ust_session_list.count++;
+
+	return LTTCOMM_OK;
 
 error:
 	free(lus);
@@ -1742,9 +1762,10 @@ static int cmd_disable_channel(struct ltt_session *session,
 
 			kernel_wait_quiescent(kernel_tracer_fd);
 			break;
+		case LTTNG_DOMAIN_UST_PID:
+			break;
 		default:
-			/* TODO: Userspace tracing */
-			ret = LTTCOMM_NOT_IMPLEMENTED;
+			ret = LTTCOMM_UNKNOWN_DOMAIN;
 			goto error;
 	}
 
@@ -1757,33 +1778,106 @@ error:
 /*
  * Command LTTNG_ENABLE_CHANNEL processed by the client thread.
  */
-static int cmd_enable_channel(struct ltt_session *session, int domain,
-		char *channel_name, struct lttng_channel *attr)
+static int cmd_enable_channel(struct ltt_session *session,
+		struct lttng_domain *domain, struct lttng_channel *attr)
 {
 	int ret;
-	struct ltt_kernel_channel *kchan;
 
-	switch (domain) {
-		case LTTNG_DOMAIN_KERNEL:
-			kchan = trace_kernel_get_channel_by_name(channel_name,
-					session->kernel_session);
-			if (kchan == NULL) {
-				ret = channel_kernel_create(session->kernel_session,
-						channel_name, attr, kernel_poll_pipe[1]);
-			} else {
-				ret = channel_kernel_enable(session->kernel_session, kchan);
-			}
+	switch (domain->type) {
+	case LTTNG_DOMAIN_KERNEL:
+	{
+		struct ltt_kernel_channel *kchan;
 
-			if (ret != LTTCOMM_OK) {
+		kchan = trace_kernel_get_channel_by_name(attr->name,
+				session->kernel_session);
+		if (kchan == NULL) {
+			ret = channel_kernel_create(session->kernel_session,
+					attr, kernel_poll_pipe[1]);
+		} else {
+			ret = channel_kernel_enable(session->kernel_session, kchan);
+		}
+
+		if (ret != LTTCOMM_OK) {
+			goto error;
+		}
+
+		kernel_wait_quiescent(kernel_tracer_fd);
+		break;
+	}
+	case LTTNG_DOMAIN_UST_PID:
+	{
+		struct ltt_ust_event *uevent, *new_uevent;
+		struct ltt_ust_session *usess;
+		struct ltt_ust_channel *uchan, *app_chan;
+		struct ltt_traceable_app *app;
+
+		usess = trace_ust_get_session_by_pid(&session->ust_session_list,
+				domain->attr.pid);
+		if (usess == NULL) {
+			ret = LTTCOMM_UST_CHAN_NOT_FOUND;
+			goto error;
+		}
+
+		app = traceable_app_get_by_pid(domain->attr.pid);
+		if (app == NULL) {
+			ret = LTTCOMM_APP_NOT_FOUND;
+			goto error;
+		}
+
+		uchan = trace_ust_get_channel_by_name(attr->name, usess);
+		if (uchan == NULL) {
+			ret = channel_ust_create(usess, attr, app->sock);
+		} else {
+			ret = channel_ust_enable(usess, uchan, app->sock);
+		}
+
+		if (ret != LTTCOMM_OK) {
+			goto error;
+		}
+
+		/*TODO: This should be put in an external function */
+
+		/* Copy UST channel to add to the traceable app */
+		uchan = trace_ust_get_channel_by_name(attr->name, usess);
+		if (uchan == NULL) {
+			ret = LTTCOMM_FATAL;
+			goto error;
+		}
+
+		app_chan = trace_ust_create_channel(attr, session->path);
+		if (app_chan == NULL) {
+			PERROR("malloc ltt_ust_channel");
+			ret = LTTCOMM_FATAL;
+			goto error;
+		}
+
+		memcpy(app_chan, uchan, sizeof(struct ltt_ust_channel));
+		CDS_INIT_LIST_HEAD(&app_chan->events.head);
+
+		cds_list_for_each_entry(uevent, &uchan->events.head, list) {
+			new_uevent = malloc(sizeof(struct ltt_ust_event));
+			if (new_uevent == NULL) {
+				PERROR("malloc ltt_ust_event");
+				ret = LTTCOMM_FATAL;
 				goto error;
 			}
 
-			kernel_wait_quiescent(kernel_tracer_fd);
-			break;
-		default:
-			/* TODO: Userspace tracing */
-			ret = LTTCOMM_NOT_IMPLEMENTED;
-			goto error;
+			memcpy(new_uevent, uevent, sizeof(struct ltt_ust_event));
+			cds_list_add(&new_uevent->list, &app_chan->events.head);
+			app_chan->events.count++;
+		}
+
+		/* Add channel to traceable_app */
+		cds_list_add(&app_chan->list, &app->channels.head);
+		app->channels.count++;
+
+		DBG("UST channel %s created for app sock %d with pid %d",
+				attr->name, app->sock, domain->attr.pid);
+		break;
+	}
+	default:
+		ret = LTTCOMM_UNKNOWN_DOMAIN;
+		goto error;
 	}
 
 	ret = LTTCOMM_OK;
@@ -1911,7 +2005,7 @@ static int cmd_enable_event(struct ltt_session *session, int domain,
 				session->kernel_session);
 		if (kchan == NULL) {
 			/* This call will notify the kernel thread */
-			ret = channel_kernel_create(session->kernel_session, channel_name,
+			ret = channel_kernel_create(session->kernel_session,
 					NULL, kernel_poll_pipe[1]);
 			if (ret != LTTCOMM_OK) {
 				goto error;
@@ -1961,8 +2055,8 @@ static int cmd_enable_event_all(struct ltt_session *session, int domain,
 				session->kernel_session);
 		if (kchan == NULL) {
 			/* This call will notify the kernel thread */
-			ret = channel_kernel_create(session->kernel_session, channel_name,
-					NULL, kernel_poll_pipe[1]);
+			ret = channel_kernel_create(session->kernel_session, NULL,
+					kernel_poll_pipe[1]);
 			if (ret != LTTCOMM_OK) {
 				goto error;
 			}
@@ -2368,13 +2462,13 @@ error:
 static int process_client_msg(struct command_ctx *cmd_ctx)
 {
 	int ret = LTTCOMM_OK;
-	int need_kernel_session = 1;
+	int need_tracing_session = 1;
 
 	DBG("Processing client command %d", cmd_ctx->lsm->cmd_type);
 
 	/*
 	 * Check for command that don't needs to allocate a returned payload. We do
-	 * this here so we don't have to make the call for no payload" at each
+	 * this here so we don't have to make the call for no payload at each
 	 * command.
 	 */
 	switch(cmd_ctx->lsm->cmd_type) {
@@ -2399,7 +2493,7 @@ static int process_client_msg(struct command_ctx *cmd_ctx)
 	case LTTNG_CREATE_SESSION:
 	case LTTNG_LIST_SESSIONS:
 	case LTTNG_LIST_TRACEPOINTS:
-		need_kernel_session = 0;
+		need_tracing_session = 0;
 		break;
 	default:
 		DBG("Getting session %s by name", cmd_ctx->lsm->session.name);
@@ -2435,7 +2529,7 @@ static int process_client_msg(struct command_ctx *cmd_ctx)
 		}
 
 		/* Need a session for kernel command */
-		if (need_kernel_session) {
+		if (need_tracing_session) {
 			if (cmd_ctx->session->kernel_session == NULL) {
 				ret = create_kernel_session(cmd_ctx->session);
 				if (ret < 0) {
@@ -2455,6 +2549,24 @@ static int process_client_msg(struct command_ctx *cmd_ctx)
 			}
 		}
 		break;
+	case LTTNG_DOMAIN_UST_PID:
+	{
+		struct ltt_ust_session *usess;
+
+		if (need_tracing_session) {
+			usess = trace_ust_get_session_by_pid(
+					&cmd_ctx->session->ust_session_list,
+					cmd_ctx->lsm->domain.attr.pid);
+			if (usess == NULL) {
+				ret = create_ust_session(cmd_ctx->session,
+						&cmd_ctx->lsm->domain);
+				if (ret != LTTCOMM_OK) {
+					goto error;
+				}
+			}
+		}
+		break;
+	}
 	default:
 		/* TODO Userspace tracer */
 		break;
@@ -2494,8 +2606,7 @@ static int process_client_msg(struct command_ctx *cmd_ctx)
 	}
 	case LTTNG_ENABLE_CHANNEL:
 	{
-		ret = cmd_enable_channel(cmd_ctx->session, cmd_ctx->lsm->domain.type,
-				cmd_ctx->lsm->u.enable.channel_name,
+		ret = cmd_enable_channel(cmd_ctx->session, &cmd_ctx->lsm->domain,
 				&cmd_ctx->lsm->u.channel.chan);
 		break;
 	}
diff --git a/ltt-sessiond/trace-ust.c b/ltt-sessiond/trace-ust.c
index a9aa1abce..fe007141e 100644
--- a/ltt-sessiond/trace-ust.c
+++ b/ltt-sessiond/trace-ust.c
@@ -23,24 +23,33 @@
 
 #include <lttngerr.h>
 #include <lttng-share.h>
+#include <lttng-ust.h>
 
 #include "trace-ust.h"
 
 /*
- * Return an UST session by traceable app PID.
+ * Using a ust session list, it will return the session corresponding to the
+ * pid. Must be a session of domain LTTNG_DOMAIN_UST_PID.
  */
-struct ltt_ust_session *trace_ust_get_session_by_pid(pid_t pid,
-		struct ltt_ust_session_list *session_list)
+struct ltt_ust_session *trace_ust_get_session_by_pid(
+		struct ltt_ust_session_list *session_list, pid_t pid)
 {
-	struct ltt_ust_session *lus;
+	struct ltt_ust_session *sess;
 
-	cds_list_for_each_entry(lus, &session_list->head, list) {
-		if (lus->app->pid == pid) {
-			DBG("Found UST session by pid %d", pid);
-			return lus;
+	if (session_list == NULL) {
+		ERR("Session list is NULL");
+		goto error;
+	}
+
+	cds_list_for_each_entry(sess, &session_list->head, list) {
+		if (sess->domain.type == LTTNG_DOMAIN_UST_PID &&
+				sess->domain.attr.pid == pid) {
+			DBG2("Trace UST session found by pid %d", pid);
+			return sess;
 		}
 	}
 
+error:
 	return NULL;
 }
 
@@ -59,7 +68,7 @@ struct ltt_ust_channel *trace_ust_get_channel_by_name(
 
 	cds_list_for_each_entry(chan, &session->channels.head, list) {
 		if (strcmp(name, chan->name) == 0) {
-			DBG("Found UST channel by name %s", name);
+			DBG2("Found UST channel by name %s", name);
 			return chan;
 		}
 	}
@@ -82,7 +91,7 @@ struct ltt_ust_event *trace_ust_get_event_by_name(
 	}
 
 	cds_list_for_each_entry(ev, &channel->events.head, list) {
-		if (strcmp(name, ev->event->name) == 0) {
+		if (strcmp(name, ev->attr.name) == 0) {
 			DBG("Found UST event by name %s for channel %s", name,
 					channel->name);
 			return ev;
@@ -98,7 +107,8 @@ error:
  *
  * Return pointer to structure or NULL.
  */
-struct ltt_ust_session *trace_ust_create_session(char *path, pid_t pid)
+struct ltt_ust_session *trace_ust_create_session(char *path, pid_t pid,
+		struct lttng_domain *domain)
 {
 	int ret;
 	struct ltt_ust_session *lus;
@@ -114,19 +124,22 @@ struct ltt_ust_session *trace_ust_create_session(char *path, pid_t pid)
 	lus->handle = -1;
 	lus->enabled = 1;
 	lus->uconsumer_fds_sent = 0;
-	lus->path = NULL;
 	lus->metadata = NULL;
-	lus->app = NULL;	/* TODO: Search app by PID */
 	lus->channels.count = 0;
 	CDS_INIT_LIST_HEAD(&lus->channels.head);
 
+	/* Copy lttng_domain */
+	memcpy(&lus->domain, domain, sizeof(struct lttng_domain));
+
 	/* Set session path */
-	ret = asprintf(&lus->path, "%s/ust_%d", path, pid);
+	ret = snprintf(lus->path, PATH_MAX, "%s/ust_%d", path, pid);
 	if (ret < 0) {
-		perror("asprintf kernel traces path");
+		PERROR("snprintf kernel traces path");
 		goto error;
 	}
 
+	DBG2("UST trace session create successful");
+
 	return lus;
 
 error:
@@ -138,8 +151,8 @@ error:
  *
  * Return pointer to structure or NULL.
  */
-struct ltt_ust_channel *trace_ust_create_channel(char *name, char *path,
-		struct lttng_ust_channel *chan)
+struct ltt_ust_channel *trace_ust_create_channel(struct lttng_channel *chan,
+		char *path)
 {
 	int ret;
 	struct ltt_ust_channel *luc;
@@ -150,25 +163,29 @@ struct ltt_ust_channel *trace_ust_create_channel(char *name, char *path,
 		goto error;
 	}
 
-	luc->attr = malloc(sizeof(struct lttng_ust_channel));
-	if (luc->attr == NULL) {
-		perror("lttng_ust_channel malloc");
-		goto error;
+	/* Copy UST channel attributes */
+	memcpy(&luc->attr, &chan->attr, sizeof(struct lttng_ust_channel));
+
+	/* Translate to UST output enum */
+	switch (luc->attr.output) {
+	default:
+		luc->attr.output = LTTNG_UST_MMAP;
+		break;
 	}
-	memcpy(luc->attr, chan, sizeof(struct lttng_ust_channel));
 
 	luc->handle = -1;
 	luc->enabled = 1;
-	luc->ctx = NULL;
 	luc->events.count = 0;
 	CDS_INIT_LIST_HEAD(&luc->events.head);
 
+	memset(&luc->ctx, 0, sizeof(struct lttng_ust_context));
+
 	/* Copy channel name */
-	strncpy(luc->name, name, LTTNG_UST_SYM_NAME_LEN);
+	strncpy(luc->name, chan->name, sizeof(&luc->name));
 	luc->name[LTTNG_UST_SYM_NAME_LEN - 1] = '\0';
 
 	/* Set trace output path */
-	ret = asprintf(&luc->trace_path, "%s", path);
+	ret = snprintf(luc->trace_path, PATH_MAX, "%s", path);
 	if (ret < 0) {
 		perror("asprintf ust create channel");
 		goto error;
@@ -188,27 +205,25 @@ error:
 struct ltt_ust_event *trace_ust_create_event(struct lttng_event *ev)
 {
 	struct ltt_ust_event *lue;
-	struct lttng_ust_event *event;
 
 	lue = malloc(sizeof(struct ltt_ust_event));
-	event = malloc(sizeof(struct lttng_ust_event));
-	if (lue == NULL || event == NULL) {
-		perror("ust event malloc");
+	if (lue == NULL) {
+		PERROR("ust event malloc");
 		goto error;
 	}
 
 	switch (ev->type) {
 	case LTTNG_EVENT_PROBE:
-		event->instrumentation = LTTNG_UST_PROBE;
+		lue->attr.instrumentation = LTTNG_UST_PROBE;
 		break;
 	case LTTNG_EVENT_FUNCTION:
-		event->instrumentation = LTTNG_UST_FUNCTION;
+		lue->attr.instrumentation = LTTNG_UST_FUNCTION;
 		break;
 	case LTTNG_EVENT_FUNCTION_ENTRY:
-		event->instrumentation = LTTNG_UST_FUNCTION;
+		lue->attr.instrumentation = LTTNG_UST_FUNCTION;
 		break;
 	case LTTNG_EVENT_TRACEPOINT:
-		event->instrumentation = LTTNG_UST_TRACEPOINT;
+		lue->attr.instrumentation = LTTNG_UST_TRACEPOINT;
 		break;
 	default:
 		ERR("Unknown ust instrumentation type (%d)", ev->type);
@@ -216,14 +231,13 @@ struct ltt_ust_event *trace_ust_create_event(struct lttng_event *ev)
 	}
 
 	/* Copy event name */
-	strncpy(event->name, ev->name, LTTNG_UST_SYM_NAME_LEN);
-	event->name[LTTNG_UST_SYM_NAME_LEN - 1] = '\0';
+	strncpy(lue->attr.name, ev->name, LTTNG_UST_SYM_NAME_LEN);
+	lue->attr.name[LTTNG_UST_SYM_NAME_LEN - 1] = '\0';
 
 	/* Setting up a ust event */
 	lue->handle = -1;
-	lue->event = event;
 	lue->enabled = 1;
-	lue->ctx = NULL;
+	memset(&lue->ctx, 0, sizeof(struct lttng_ust_context));
 
 	return lue;
 
@@ -240,24 +254,21 @@ struct ltt_ust_metadata *trace_ust_create_metadata(char *path)
 {
 	int ret;
 	struct ltt_ust_metadata *lum;
-	struct lttng_ust_channel *attr;
 
 	lum = malloc(sizeof(struct ltt_ust_metadata));
-	attr = malloc(sizeof(struct lttng_ust_channel));
-	if (lum == NULL || attr == NULL) {
+	if (lum == NULL) {
 		perror("ust metadata malloc");
 		goto error;
 	}
 
 	/* Set default attributes */
-	attr->overwrite = DEFAULT_CHANNEL_OVERWRITE;
-	attr->subbuf_size = DEFAULT_METADATA_SUBBUF_SIZE;
-	attr->num_subbuf = DEFAULT_METADATA_SUBBUF_NUM;
-	attr->switch_timer_interval = DEFAULT_CHANNEL_SWITCH_TIMER;
-	attr->read_timer_interval = DEFAULT_CHANNEL_READ_TIMER;
-	attr->output = DEFAULT_UST_CHANNEL_OUTPUT;
-
-	lum->attr = attr;
+	lum->attr.overwrite = DEFAULT_CHANNEL_OVERWRITE;
+	lum->attr.subbuf_size = DEFAULT_METADATA_SUBBUF_SIZE;
+	lum->attr.num_subbuf = DEFAULT_METADATA_SUBBUF_NUM;
+	lum->attr.switch_timer_interval = DEFAULT_CHANNEL_SWITCH_TIMER;
+	lum->attr.read_timer_interval = DEFAULT_CHANNEL_READ_TIMER;
+	lum->attr.output = DEFAULT_UST_CHANNEL_OUTPUT;
+
 	lum->handle = -1;
 	/* Set metadata trace path */
 	ret = asprintf(&lum->trace_path, "%s/metadata", path);
@@ -277,11 +288,7 @@ error:
  */
 void trace_ust_destroy_event(struct ltt_ust_event *event)
 {
-	DBG("[trace] Destroy ust event %s", event->event->name);
-
-	/* Free attributes */
-	free(event->event);
-	free(event->ctx);
+	DBG("[trace] Destroy ust event %s", event->attr.name);
 
 	/* Remove from event list */
 	cds_list_del(&event->list);
@@ -297,11 +304,6 @@ void trace_ust_destroy_channel(struct ltt_ust_channel *channel)
 
 	DBG("[trace] Destroy ust channel %d", channel->handle);
 
-	free(channel->trace_path);
-	/* Free attributes structure */
-	free(channel->attr);
-	free(channel->ctx);
-
 	/* For each event in the channel list */
 	cds_list_for_each_entry_safe(event, etmp, &channel->events.head, list) {
 		trace_ust_destroy_event(event);
@@ -320,7 +322,6 @@ void trace_ust_destroy_metadata(struct ltt_ust_metadata *metadata)
 	DBG("[trace] Destroy ust metadata %d", metadata->handle);
 
 	/* Free attributes */
-	free(metadata->attr);
 	free(metadata->trace_path);
 
 	free(metadata);
@@ -348,6 +349,9 @@ void trace_ust_destroy_session(struct ltt_ust_session *session)
 		trace_ust_destroy_channel(channel);
 	}
 
-	free(session->path);
+	if (session->path) {
+		free(session->path);
+	}
+
 	free(session);
 }
diff --git a/ltt-sessiond/trace-ust.h b/ltt-sessiond/trace-ust.h
index 55a452c60..9a2366269 100644
--- a/ltt-sessiond/trace-ust.h
+++ b/ltt-sessiond/trace-ust.h
@@ -25,8 +25,6 @@
 #include <lttng/lttng.h>
 #include <lttng-ust.h>
 
-#include "traceable-app.h"
-
 /*
  * UST session list.
  */
@@ -51,8 +49,8 @@ struct ltt_ust_channel_list {
 struct ltt_ust_event {
 	int handle;
 	int enabled;
-	struct lttng_ust_context *ctx;
-	struct lttng_ust_event *event;
+	struct lttng_ust_context ctx;
+	struct lttng_ust_event attr;
 	struct cds_list_head list;
 };
 
@@ -60,10 +58,10 @@ struct ltt_ust_event {
 struct ltt_ust_channel {
 	int handle;
 	int enabled;
-	char *name;
-	char *trace_path;                   /* Trace file path name */
-	struct lttng_ust_context *ctx;
-	struct lttng_ust_channel *attr;
+	char name[LTTNG_UST_SYM_NAME_LEN];
+	char trace_path[PATH_MAX];    /* Trace file path name */
+	struct lttng_ust_context ctx;
+	struct lttng_ust_channel attr;
 	struct ltt_ust_event_list events;
 	struct cds_list_head list;
 };
@@ -72,7 +70,7 @@ struct ltt_ust_channel {
 struct ltt_ust_metadata {
 	int handle;
 	char *trace_path;             /* Trace file path name */
-	struct lttng_ust_channel *attr;
+	struct lttng_ust_channel attr;
 };
 
 /* UST session */
@@ -80,8 +78,8 @@ struct ltt_ust_session {
 	int handle;
 	int enabled;
 	int uconsumer_fds_sent;
-	char *path;
-	struct ltt_traceable_app *app;
+	char path[PATH_MAX];
+	struct lttng_domain domain;
 	struct ltt_ust_metadata *metadata;
 	struct ltt_ust_channel_list channels;
 	struct cds_list_head list;
@@ -94,15 +92,16 @@ struct ltt_ust_event *trace_ust_get_event_by_name(
 		char *name, struct ltt_ust_channel *channel);
 struct ltt_ust_channel *trace_ust_get_channel_by_name(
 		char *name, struct ltt_ust_session *session);
-struct ltt_ust_session *trace_ust_get_session_by_pid(pid_t pid,
-		struct ltt_ust_session_list *session_list);
+struct ltt_ust_session *trace_ust_get_session_by_pid(
+		struct ltt_ust_session_list *session_list, pid_t pid);
 
 /*
  * Create functions malloc() the data structure.
  */
-struct ltt_ust_session *trace_ust_create_session(char *path, pid_t pid);
-struct ltt_ust_channel *trace_ust_create_channel(char *name, char *path,
-		struct lttng_ust_channel *attr);
+struct ltt_ust_session *trace_ust_create_session(char *path, pid_t pid,
+		struct lttng_domain *domain);
+struct ltt_ust_channel *trace_ust_create_channel(struct lttng_channel *attr,
+		char *path);
 struct ltt_ust_event *trace_ust_create_event(struct lttng_event *ev);
 struct ltt_ust_metadata *trace_ust_create_metadata(char *path);
 
diff --git a/ltt-sessiond/traceable-app.c b/ltt-sessiond/traceable-app.c
index 653d86b3f..41dc51111 100644
--- a/ltt-sessiond/traceable-app.c
+++ b/ltt-sessiond/traceable-app.c
@@ -49,11 +49,17 @@ static void add_traceable_app(struct ltt_traceable_app *lta)
  */
 static void del_traceable_app(struct ltt_traceable_app *lta)
 {
+	struct ltt_ust_channel *chan;
+
 	cds_list_del(&lta->list);
 	/* Sanity check */
 	if (ltt_traceable_app_list.count > 0) {
 		ltt_traceable_app_list.count--;
 	}
+
+	cds_list_for_each_entry(chan, &lta->channels.head, list) {
+		trace_ust_destroy_channel(chan);
+	}
 }
 
 /*
@@ -109,10 +115,13 @@ struct ltt_traceable_app *traceable_app_get_by_pid(pid_t pid)
 	cds_list_for_each_entry(iter, &ltt_traceable_app_list.head, list) {
 		if (iter->pid == pid) {
 			/* Found */
+			DBG2("Found traceable app by pid %d", pid);
 			return iter;
 		}
 	}
 
+	DBG2("Traceable app with pid %d not found", pid);
+
 	return NULL;
 }
 
@@ -141,6 +150,7 @@ int register_traceable_app(struct ust_register_msg *msg, int sock)
 	lta->sock = sock;
 	strncpy(lta->name, msg->name, sizeof(lta->name));
 	lta->name[16] = '\0';
+	CDS_INIT_LIST_HEAD(&lta->channels.head);
 
 	lock_apps_list();
 	add_traceable_app(lta);
@@ -167,8 +177,8 @@ void unregister_traceable_app(int sock)
 	lta = find_app_by_sock(sock);
 	if (lta) {
 		DBG("PID %d unregistered with sock %d", lta->pid, sock);
-		close(lta->sock);
 		del_traceable_app(lta);
+		close(lta->sock);
 		free(lta);
 	}
 	unlock_apps_list();
@@ -200,6 +210,7 @@ void clean_traceable_apps_list(void)
 	 * cleanup() functions meaning that the program will exit.
 	 */
 	cds_list_for_each_entry_safe(iter, tmp, &ltt_traceable_app_list.head, list) {
+		del_traceable_app(iter);
 		close(iter->sock);
 		free(iter);
 	}
diff --git a/ltt-sessiond/traceable-app.h b/ltt-sessiond/traceable-app.h
index 4d5e56a66..39f97f2a2 100644
--- a/ltt-sessiond/traceable-app.h
+++ b/ltt-sessiond/traceable-app.h
@@ -22,6 +22,8 @@
 #include <stdint.h>
 #include <urcu/list.h>
 
+#include "trace-ust.h"
+
 /*
  * Application registration data structure.
  */
@@ -70,6 +72,7 @@ struct ltt_traceable_app {
 	uint32_t v_major;    /* Verion major number */
 	uint32_t v_minor;    /* Verion minor number */
 	char name[17];       /* Process name (short) */
+	struct ltt_ust_channel_list channels;
 	struct cds_list_head list;
 };
 
@@ -82,4 +85,6 @@ void unlock_apps_list(void);
 void clean_traceable_apps_list(void);
 struct ltt_traceable_app_list *get_traceable_apps_list(void);
 
+struct ltt_traceable_app *traceable_app_get_by_pid(pid_t pid);
+
 #endif /* _TRACEABLE_APP_H */
diff --git a/ltt-sessiond/ust-comm.c b/ltt-sessiond/ust-comm.c
index 31c40070e..455d40c0a 100644
--- a/ltt-sessiond/ust-comm.c
+++ b/ltt-sessiond/ust-comm.c
@@ -24,7 +24,7 @@
 
 /*
  * Send msg containing a command to an UST application via sock and wait for
- * the reply.
+ * the reply. Caller must free() the reply structure sent back.
  *
  * Return the replied structure or NULL.
  */
@@ -39,7 +39,7 @@ struct lttcomm_ust_reply *ustcomm_send_command(int sock,
 		goto error;
 	}
 
-	DBG("Sending UST command %d to sock %d", msg->cmd, sock);
+	DBG2("Sending UST command %d to sock %d", msg->cmd, sock);
 
 	/* Send UST msg */
 	len = lttcomm_send_unix_sock(sock, msg, sizeof(*msg));
@@ -53,7 +53,7 @@ struct lttcomm_ust_reply *ustcomm_send_command(int sock,
 		goto error;
 	}
 
-	DBG("Receiving UST reply on sock %d", sock);
+	DBG2("Receiving UST reply on sock %d", sock);
 
 	/* Get UST reply */
 	len = lttcomm_recv_unix_sock(sock, reply, sizeof(*reply));
diff --git a/ltt-sessiond/ust-ctl.c b/ltt-sessiond/ust-ctl.c
index 5f4e8a9fc..2753b6f5a 100644
--- a/ltt-sessiond/ust-ctl.c
+++ b/ltt-sessiond/ust-ctl.c
@@ -60,17 +60,15 @@ error:
 /*
  * Create an UST session on the tracer.
  */
-int ustctl_create_session(struct ltt_ust_session *session)
+int ustctl_create_session(int sock, struct ltt_ust_session *session)
 {
 	struct lttcomm_ust_msg command;
-	struct lttcomm_ust_reply *reply;
-
-	DBG("Creating UST session for app pid:%d", session->app->pid);
+	struct lttcomm_ust_reply *reply = NULL;
 
 	command.cmd = LTTNG_UST_SESSION;
 	command.handle = LTTNG_UST_ROOT_HANDLE;
 
-	reply = ustcomm_send_command(session->app->sock, &command);
+	reply = ustcomm_send_command(sock, &command);
 	if (reply == NULL) {
 		goto error;
 	}
@@ -81,10 +79,140 @@ int ustctl_create_session(struct ltt_ust_session *session)
 	}
 
 	/* Save session handle */
-	session->handle = reply->handle;
+	session->handle = reply->ret_val;
+	free(reply);
+
+	DBG2("ustctl create session command successful");
+	return 0;
+
+error:
+	free(reply);
+	return -1;
+}
+
+/*
+ * Create UST channel to the tracer.
+ */
+int ustctl_create_channel(int sock, struct ltt_ust_session *session,
+		struct lttng_channel *channel)
+{
+	struct lttcomm_ust_msg command;
+	struct lttcomm_ust_reply *reply = NULL;
+	struct ltt_ust_channel *uchan;
+
+	uchan = trace_ust_create_channel(channel, session->path);
+	if (uchan == NULL) {
+		goto error;
+	}
+
+	memset(&command, 0, sizeof(command));
+
+	command.cmd = LTTNG_UST_CHANNEL;
+	command.handle = session->handle;
+
+	/* Copy channel attributes to command */
+	memcpy(&command.u.channel, &uchan->attr, sizeof(command.u.channel));
+
+	reply = ustcomm_send_command(sock, &command);
+	if (reply == NULL) {
+		goto error;
+	}
+
+	if (reply->ret_code != LTTCOMM_OK) {
+		DBG("Return code (%d): %s", reply->ret_code,
+				lttcomm_get_readable_code(reply->ret_code));
+		goto error;
+	}
+
+	uchan->handle = reply->ret_val;
+
+	/* Add channel to session */
+	cds_list_add(&uchan->list, &session->channels.head);
+	session->channels.count++;
+
+	free(reply);
+
+	return 0;
+
+error:
+	free(reply);
+	return -1;
+}
+
+/*
+ * Enable UST channel.
+ */
+int ustctl_enable_channel(int sock, struct ltt_ust_session *session,
+		struct ltt_ust_channel *chan)
+{
+	struct lttcomm_ust_msg command;
+	struct lttcomm_ust_reply *reply = NULL;
+
+	memset(&command, 0, sizeof(command));
+
+	command.cmd = LTTNG_UST_ENABLE;
+	command.handle = chan->handle;
+
+	reply = ustcomm_send_command(sock, &command);
+	if (reply == NULL) {
+		goto error;
+	}
+
+	if (reply->ret_code != LTTCOMM_OK) {
+		DBG("Return code (%d): %s", reply->ret_code,
+				lttcomm_get_readable_code(reply->ret_code));
+		goto error;
+	} else if (reply->handle != chan->handle) {
+		ERR("Receive wrong handle from UST reply on enable channel");
+		goto error;
+	}
+
+	chan->enabled = 1;
+	free(reply);
+
+	DBG2("ustctl enable channel successful for sock %d", sock);
+	return 0;
+
+error:
+	free(reply);
+	return -1;
+}
+
+/*
+ * Disable UST channel.
+ */
+int ustctl_disable_channel(int sock, struct ltt_ust_session *session,
+		struct ltt_ust_channel *chan)
+{
+	struct lttcomm_ust_msg command;
+	struct lttcomm_ust_reply *reply = NULL;
+
+	memset(&command, 0, sizeof(command));
+
+	command.cmd = LTTNG_UST_DISABLE;
+	command.handle = chan->handle;
+
+	reply = ustcomm_send_command(sock, &command);
+	if (reply == NULL) {
+		goto error;
+	}
+
+	if (reply->ret_code != LTTCOMM_OK) {
+		DBG("Return code (%d): %s", reply->ret_code,
+				lttcomm_get_readable_code(reply->ret_code));
+		goto error;
+	} else if (reply->handle != chan->handle) {
+		ERR("Receive wrong handle from UST reply on enable channel");
+		goto error;
+	}
+
+	chan->enabled = 1;
+	free(reply);
 
+	DBG2("ustctl disable channel successful for sock %d", sock);
 	return 0;
 
 error:
+	free(reply);
 	return -1;
 }
diff --git a/ltt-sessiond/ust-ctl.h b/ltt-sessiond/ust-ctl.h
index 8f8bebc99..c4d754eca 100644
--- a/ltt-sessiond/ust-ctl.h
+++ b/ltt-sessiond/ust-ctl.h
@@ -19,10 +19,18 @@
 #ifndef _LTT_UST_CTL_H
 #define _LTT_UST_CTL_H
 
+#include <lttng/lttng.h>
+
 #include "trace-ust.h"
 
 int ustctl_register_done(int sock);
-int ustctl_create_session(struct ltt_ust_session *session);
-int ustctl_destroy_session(struct ltt_ust_session *session);
+int ustctl_create_channel(int sock, struct ltt_ust_session *session,
+		struct lttng_channel *channel);
+int ustctl_create_session(int sock, struct ltt_ust_session *session);
+int ustctl_destroy_session(int sock, struct ltt_ust_session *session);
+int ustctl_disable_channel(int sock, struct ltt_ust_session *session,
+		struct ltt_ust_channel *chan);
+int ustctl_enable_channel(int sock, struct ltt_ust_session *session,
+		struct ltt_ust_channel *chan);
 
 #endif /* _LTT_UST_CTL_H */