From: David Goulet <david.goulet@polymtl.ca>
Date: Wed, 30 Nov 2011 21:34:47 +0000 (-0500)
Subject: Support for UST context
X-Git-Tag: v2.0-pre15~52
X-Git-Url: https://git.lttng.org/?p=lttng-tools.git;a=commitdiff_plain;h=55cc08a60ad1b188d59161842e630402e738e62e

Support for UST context

Adds the support to add context on channel and/or events for UST global
domain.

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

diff --git a/lttng-sessiond/context.c b/lttng-sessiond/context.c
index c7c902197..d6f4d2f75 100644
--- a/lttng-sessiond/context.c
+++ b/lttng-sessiond/context.c
@@ -28,6 +28,7 @@
 #include "context.h"
 #include "hashtable.h"
 #include "kernel.h"
+#include "ust-app.h"
 
 /*
  * Add kernel context to an event of a specific channel.
@@ -194,192 +195,124 @@ error:
 }
 
 /*
- * UST support.
- */
-
-/*
- * Add UST context to an event of a specific channel.
- */
-#ifdef DISABLE
-static int add_ustctx_to_event(struct ltt_ust_session *ustsession,
-		struct lttng_ust_context *ustctx,
-		struct ltt_ust_channel *ustchan, char *event_name)
-{
-	int ret, found = 0;
-	struct ltt_ust_event *ustevent;
-	struct object_data *context_data;	/* FIXME: currently a memleak */
-
-	DBG("Add UST context to event %s", event_name);
-
-	ustevent = trace_ust_find_event_by_name(ustchan->events, event_name);
-	if (ustevent != NULL) {
-		ret = ustctl_add_context(ustsession->sock, ustctx,
-			ustevent->obj, &context_data);
-		if (ret < 0) {
-			goto error;
-		}
-		found = 1;
-	}
-
-	ret = found;
-
-error:
-	return ret;
-}
-#endif
-
-/*
- * Add UST context to all channel.
- *
- * If event_name is specified, add context to event instead.
+ * Add UST context to tracer.
  */
-static int add_ustctx_all_channels(struct ltt_ust_session *ustsession,
-		struct lttng_ust_context *ustctx, char *event_name,
-		struct cds_lfht *channels)
+int context_ust_add(struct ltt_ust_session *usess, int domain,
+		struct lttng_event_context *ctx, char *event_name,
+		char *channel_name)
 {
-#ifdef DISABLE
-	int ret, no_event = 0, found = 0;
-	struct ltt_ust_channel *ustchan;
-	struct object_data *context_data;	/* FIXME: currently a memleak */
+	int ret = LTTCOMM_OK, have_event = 0;
+	struct cds_lfht_iter iter, uiter;
+	struct cds_lfht *chan_ht;
+	struct ltt_ust_channel *uchan = NULL;
+	struct ltt_ust_event *uevent = NULL;
+	struct ltt_ust_context *uctx;
 
-	if (strlen(event_name) == 0) {
-		no_event = 1;
-	}
-
-	DBG("Adding ust context to all channels (event: %s)", event_name);
-
-	struct cds_lfht_node *node;
-	struct cds_lfht_iter iter;
-
-	rcu_read_lock();
-	hashtable_get_first(channels, &iter);
-	while ((node = hashtable_iter_get_node(&iter)) != NULL) {
-		ustchan = caa_container_of(node, struct ltt_ust_channel, node);
-		if (no_event) {
-			//ret = ustctl_add_context(ustsession->sock,
-			//		ustctx, ustchan->obj, &context_data);
-			if (ret < 0) {
-				ret = LTTCOMM_UST_CONTEXT_FAIL;
-				goto error;
-			}
-		} else {
-			ret = add_ustctx_to_event(ustsession, ustctx, ustchan, event_name);
-			if (ret < 0) {
-				ret = LTTCOMM_UST_CONTEXT_FAIL;
-				goto error;
-			} else if (ret == 1) {
-				/* Event found and context added */
-				found = 1;
-				break;
-			}
-		}
-		hashtable_get_next(channels, &iter);
-	}
-	if (!found && !no_event) {
-		ret = LTTCOMM_NO_EVENT;
+	switch (domain) {
+	case LTTNG_DOMAIN_UST:
+		chan_ht = usess->domain_global.channels;
+		break;
+	case LTTNG_DOMAIN_UST_EXEC_NAME:
+	case LTTNG_DOMAIN_UST_PID:
+	case LTTNG_DOMAIN_UST_PID_FOLLOW_CHILDREN:
+	default:
+		ret = LTTCOMM_NOT_IMPLEMENTED;
 		goto error;
 	}
-	ret = LTTCOMM_OK;
-error:
-	rcu_read_unlock();
-	return ret;
-#endif
-	return 0;
-}
-
-/*
- * Add UST context to a specific channel.
- *
- * If event_name is specified, add context to that event.
- */
-static int add_ustctx_to_channel(struct ltt_ust_session *ustsession,
-		struct lttng_ust_context *ustctx,
-		struct ltt_ust_channel *ustchan, char *event_name)
-{
-#ifdef DISABLE
-	int ret, no_event = 0, found = 0;
-	struct object_data *context_data;	/* FIXME: currently a memleak */
 
-	if (strlen(event_name) == 0) {
-		no_event = 1;
+	if (strlen(event_name) != 0) {
+		have_event = 1;
 	}
 
-	DBG("Add UST context to channel '%s', event '%s'",
-			ustchan->name, event_name);
-
-	if (no_event) {
-		//ret = ustctl_add_context(ustsession->sock, ustctx,
-		//	ustchan->obj, &context_data);
-		if (ret < 0) {
-			ret = LTTCOMM_UST_CONTEXT_FAIL;
+	/* Get UST channel if defined */
+	if (strlen(channel_name) != 0) {
+		uchan = trace_ust_find_channel_by_name(chan_ht, channel_name);
+		if (uchan == NULL) {
+			ret = LTTCOMM_UST_CHAN_NOT_FOUND;
 			goto error;
 		}
-	} else {
-		ret = add_ustctx_to_event(ustsession, ustctx, ustchan, event_name);
-		if (ret < 0) {
-			ret = LTTCOMM_UST_CONTEXT_FAIL;
+	}
+
+	/* If UST channel specified and event name, get UST event ref */
+	if (uchan && have_event) {
+		uevent = trace_ust_find_event_by_name(uchan->events, event_name);
+		if (uevent == NULL) {
+			ret = LTTCOMM_UST_EVENT_NOT_FOUND;
 			goto error;
-		} else if (ret == 1) {
-			/* Event found and context added */
-			found = 1;
 		}
 	}
 
-	if (!found && !no_event) {
-		ret = LTTCOMM_NO_EVENT;
+	/* Create ltt UST context */
+	uctx = trace_ust_create_context(ctx);
+	if (uctx == NULL) {
+		ret = LTTCOMM_FATAL;
 		goto error;
 	}
 
-	ret = LTTCOMM_OK;
-
-error:
-	return ret;
-#endif
-	return 0;
-}
-
-/*
- * Add UST context to tracer.
- */
-int context_ust_add(struct ltt_ust_session *ustsession,
-		struct lttng_event_context *ctx, char *event_name,
-		char *channel_name, int domain)
-{
-	int ret;
-	struct cds_lfht *chan_ht = NULL;
-	struct ltt_ust_channel *ustchan;
-	struct lttng_ust_context ustctx;
-
-	/* Setup UST context structure */
-	ustctx.ctx = ctx->ctx;
-
-	switch (domain) {
-		case LTTNG_DOMAIN_UST:
-			chan_ht = ustsession->domain_global.channels;
-			break;
-	}
-
-	if (strlen(channel_name) == 0) {
-		ret = add_ustctx_all_channels(ustsession, &ustctx, event_name, chan_ht);
-		if (ret != LTTCOMM_OK) {
-			goto error;
+	/* At this point, we have 4 possibilities */
+
+	if (uchan && uevent) {			/* Add ctx to event in channel */
+		ret = ust_app_add_ctx_event_glb(usess, uchan, uevent, uctx);
+	} else if (uchan && !have_event) {	/* Add ctx to channel */
+		ret = ust_app_add_ctx_channel_glb(usess, uchan, uctx);
+	} else if (!uchan && have_event) {	/* Add ctx to event */
+		cds_lfht_for_each_entry(chan_ht, &iter, uchan, node) {
+			uevent = trace_ust_find_event_by_name(uchan->events, event_name);
+			if (uevent != NULL) {
+				ret = ust_app_add_ctx_event_glb(usess, uchan, uevent, uctx);
+				/*
+				 * LTTng UST does not allowed the same event to be registered
+				 * multiple time in different or the same channel. So, if we
+				 * found our event in the first place, no need to continue.
+				 */
+				goto end;
+			}
 		}
-	} else {
-		/* Get UST channel */
-		ustchan = trace_ust_find_channel_by_name(chan_ht, channel_name);
-		if (ustchan == NULL) {
-			ret = LTTCOMM_UST_CHAN_NOT_FOUND;
-			goto error;
+		ret = LTTCOMM_UST_EVENT_NOT_FOUND;
+		goto error_free_ctx;
+	} else if (!uchan && !have_event) {	/* Add ctx to all events, all channels */
+		cds_lfht_for_each_entry(chan_ht, &iter, uchan, node) {
+			ret = ust_app_add_ctx_channel_glb(usess, uchan, uctx);
+			if (ret < 0) {
+				/* Add failed so uctx was not added. We can keep it. */
+				continue;
+			}
+			cds_lfht_for_each_entry(uchan->events, &uiter, uevent, node) {
+				ret = ust_app_add_ctx_event_glb(usess, uchan, uevent, uctx);
+				if (ret < 0) {
+					/* Add failed so uctx was not added. We can keep it. */
+					continue;
+				}
+				/* Create ltt UST context */
+				uctx = trace_ust_create_context(ctx);
+				if (uctx == NULL) {
+					ret = LTTCOMM_FATAL;
+					goto error;
+				}
+			}
+			/* Create ltt UST context */
+			uctx = trace_ust_create_context(ctx);
+			if (uctx == NULL) {
+				ret = LTTCOMM_FATAL;
+				goto error;
+			}
 		}
+	}
 
-		ret = add_ustctx_to_channel(ustsession, &ustctx, ustchan, event_name);
-		if (ret != LTTCOMM_OK) {
-			goto error;
-		}
+end:
+	switch (ret) {
+	case -EEXIST:
+		ret = LTTCOMM_UST_CONTEXT_EXIST;
+		goto error_free_ctx;
+	case -ENOMEM:
+		ret = LTTCOMM_FATAL;
+		goto error_free_ctx;
 	}
 
-	ret = LTTCOMM_OK;
+	return LTTCOMM_OK;
 
+error_free_ctx:
+	free(uctx);
 error:
 	return ret;
 }
diff --git a/lttng-sessiond/context.h b/lttng-sessiond/context.h
index 589b1e16e..4383f9abc 100644
--- a/lttng-sessiond/context.h
+++ b/lttng-sessiond/context.h
@@ -26,8 +26,8 @@
 
 int context_kernel_add(struct ltt_kernel_session *ksession,
 		struct lttng_event_context *ctx, char *event_name, char *channel_name);
-int context_ust_add(struct ltt_ust_session *ustsession,
+int context_ust_add(struct ltt_ust_session *usess, int domain,
 		struct lttng_event_context *ctx, char *event_name,
-		char *channel_name, int domain);
+		char *channel_name);
 
 #endif /* _LTT_CONTEXT_H */
diff --git a/lttng-sessiond/main.c b/lttng-sessiond/main.c
index ff096e1b9..56a12518e 100644
--- a/lttng-sessiond/main.c
+++ b/lttng-sessiond/main.c
@@ -2519,21 +2519,18 @@ static int cmd_add_context(struct ltt_session *session, int domain,
 		break;
 	case LTTNG_DOMAIN_UST:
 	{
-		/*
-		struct ltt_ust_session *usess;
+		struct ltt_ust_session *usess = session->ust_session;
 
-		cds_list_for_each_entry(usess, &session->ust_session_list.head, list) {
-			ret = context_ust_add(usess, ctx,
-					event_name, channel_name, domain);
-			if (ret != LTTCOMM_OK) {
-				goto error;
-			}
+		ret = context_ust_add(usess, domain, ctx, event_name, channel_name);
+		if (ret != LTTCOMM_OK) {
+			goto error;
 		}
 		break;
-		*/
 	}
+	case LTTNG_DOMAIN_UST_EXEC_NAME:
+	case LTTNG_DOMAIN_UST_PID:
+	case LTTNG_DOMAIN_UST_PID_FOLLOW_CHILDREN:
 	default:
-		/* TODO: UST other domains */
 		ret = LTTCOMM_NOT_IMPLEMENTED;
 		goto error;
 	}
diff --git a/lttng-sessiond/trace-ust.c b/lttng-sessiond/trace-ust.c
index 20e3dc5f1..1a1304ac1 100644
--- a/lttng-sessiond/trace-ust.c
+++ b/lttng-sessiond/trace-ust.c
@@ -165,7 +165,7 @@ struct ltt_ust_channel *trace_ust_create_channel(struct lttng_channel *chan,
 	hashtable_node_init(&luc->node, (void *) luc->name, strlen(luc->name));
 	/* Alloc hash tables */
 	luc->events = hashtable_new_str(0);
-	luc->ctx = hashtable_new_str(0);
+	luc->ctx = hashtable_new(0);
 
 	/* Set trace output path */
 	ret = snprintf(luc->pathname, PATH_MAX, "%s", path);
@@ -225,7 +225,7 @@ struct ltt_ust_event *trace_ust_create_event(struct lttng_event *ev)
 	hashtable_node_init(&lue->node, (void *) lue->attr.name,
 			strlen(lue->attr.name));
 	/* Alloc context hash tables */
-	lue->ctx = hashtable_new_str(0);
+	lue->ctx = hashtable_new(0);
 
 	DBG2("Trace UST event %s created", lue->attr.name);
 
@@ -277,6 +277,32 @@ error:
 	return NULL;
 }
 
+/*
+ * Allocate and initialize an UST context.
+ *
+ * Return pointer to structure or NULL.
+ */
+struct ltt_ust_context *trace_ust_create_context(
+		struct lttng_event_context *ctx)
+{
+	struct ltt_ust_context *uctx;
+
+	uctx = zmalloc(sizeof(struct ltt_ust_context));
+	if (uctx == NULL) {
+		PERROR("zmalloc ltt_ust_context");
+		goto error;
+	}
+
+	uctx->ctx.ctx = ctx->ctx;
+	hashtable_node_init(&uctx->node, (void *)((unsigned long) uctx->ctx.ctx),
+				sizeof(void *));
+
+	return uctx;
+
+error:
+	return NULL;
+}
+
 /*
  * RCU safe free context structure.
  */
diff --git a/lttng-sessiond/trace-ust.h b/lttng-sessiond/trace-ust.h
index f0b639cba..18d3b5fc7 100644
--- a/lttng-sessiond/trace-ust.h
+++ b/lttng-sessiond/trace-ust.h
@@ -131,6 +131,8 @@ 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);
+struct ltt_ust_context *trace_ust_create_context(
+		struct lttng_event_context *ctx);
 
 /*
  * Destroy functions free() the data structure and remove from linked list if
diff --git a/lttng-sessiond/ust-app.c b/lttng-sessiond/ust-app.c
index 1afb6d199..37dbfcb91 100644
--- a/lttng-sessiond/ust-app.c
+++ b/lttng-sessiond/ust-app.c
@@ -35,17 +35,37 @@
 #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)
 {
-	/* TODO : remove context */
-	//struct ust_app_ctx *ltctx;
-	//cds_lfht_for_each_entry(lte->ctx, &iter, ltctx, node) {
-	//	delete_ust_app_ctx(sock, ltctx);
-	//}
+	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);
@@ -74,41 +94,38 @@ 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) {
-	//	ret = hashtable_del(ltc->ctx, &iter);
-	//	assert(!ret);
-	//	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) {
 		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);
 	}
 	free(ua_chan);
-
-error:
-	return;
 }
 
 /*
@@ -253,6 +270,52 @@ 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.
  */
@@ -570,19 +633,54 @@ 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;
+}
+
 /*
  * Copy data between an UST app event and a LTT event.
  */
 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);
+	}
 }
 
 /*
@@ -594,7 +692,9 @@ 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);
 
@@ -603,7 +703,15 @@ 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) {
@@ -774,6 +882,90 @@ 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.
  */
@@ -1953,3 +2145,99 @@ 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;
+}
diff --git a/lttng-sessiond/ust-app.h b/lttng-sessiond/ust-app.h
index 8a0130f07..1dc0e8ba2 100644
--- a/lttng-sessiond/ust-app.h
+++ b/lttng-sessiond/ust-app.h
@@ -55,6 +55,13 @@ struct ust_app_key {
 	struct cds_lfht_node node;
 };
 
+struct ust_app_ctx {
+	int handle;
+	struct lttng_ust_context ctx;
+	struct lttng_ust_object_data *obj;
+	struct cds_lfht_node node;
+};
+
 struct ust_app_event {
 	int enabled;
 	int handle;
@@ -134,6 +141,11 @@ int ust_app_enable_all_event_glb(struct ltt_ust_session *usess,
 		struct ltt_ust_channel *uchan);
 int ust_app_disable_event_glb(struct ltt_ust_session *usess,
 		struct ltt_ust_channel *uchan, struct ltt_ust_event *uevent);
+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 ust_app_add_ctx_channel_glb(struct ltt_ust_session *usess,
+		struct ltt_ust_channel *uchan, struct ltt_ust_context *uctx);
 void ust_app_global_update(struct ltt_ust_session *usess, int sock);
 
 void ust_app_clean_list(void);
@@ -263,6 +275,19 @@ int ust_app_enable_event_glb(struct ltt_ust_session *usess,
 {
 	return 0;
 }
+static inline
+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)
+{
+	return 0;
+}
+static inline
+int ust_app_add_ctx_channel_glb(struct ltt_ust_session *usess,
+		struct ltt_ust_channel *uchan, struct ltt_ust_context *uctx)
+{
+	return 0;
+}
 
 #endif /* HAVE_LIBLTTNG_UST_CTL */
 
diff --git a/lttng/commands/add_context.c b/lttng/commands/add_context.c
index 44c4d4815..5986195b4 100644
--- a/lttng/commands/add_context.c
+++ b/lttng/commands/add_context.c
@@ -37,7 +37,7 @@
 static char *opt_event_name;
 static char *opt_channel_name;
 static char *opt_session_name;
-static int *opt_kernel;
+static int opt_kernel;
 static int opt_pid_all;
 static int opt_userspace;
 static char *opt_cmd_name;
@@ -141,7 +141,7 @@ static struct poptOption long_options[] = {
 	{"channel",        'c', POPT_ARG_STRING, &opt_channel_name, 0, 0, 0},
 	{"event",          'e', POPT_ARG_STRING, &opt_event_name, 0, 0, 0},
 	{"kernel",         'k', POPT_ARG_VAL, &opt_kernel, 1, 0, 0},
-	{"userspace",      'u', POPT_ARG_STRING | POPT_ARGFLAG_OPTIONAL, 0, OPT_USERSPACE, 0, 0},
+	{"userspace",      'u', POPT_ARG_STRING | POPT_ARGFLAG_OPTIONAL, &opt_cmd_name, OPT_USERSPACE, 0, 0},
 	{"all",            0,   POPT_ARG_VAL, &opt_pid_all, 1, 0, 0},
 	{"pid",            'p', POPT_ARG_INT, &opt_pid, 0, 0, 0},
 	{"type",           't', POPT_ARG_STRING, &opt_type, OPT_TYPE, 0, 0},
@@ -297,10 +297,9 @@ static void usage(FILE *ofp)
 {
 	fprintf(ofp, "usage: lttng add-context -t TYPE\n");
 	fprintf(ofp, "\n");
-	fprintf(ofp, "If no event name is given (-e), the context will be added to\n");
-	fprintf(ofp, "all events in the channel.\n");
+	fprintf(ofp, "If no event name is given (-e), the context will be added to the channel\n");
 	fprintf(ofp, "If no channel and no event is given (-c/-e), the context\n");
-	fprintf(ofp, "will be added to all events in all channels.\n");
+	fprintf(ofp, "will be added to all events and all channels.\n");
 	fprintf(ofp, "\n");
 	fprintf(ofp, "Options:\n");
 	fprintf(ofp, "  -h, --help               Show this help\n");
@@ -308,7 +307,7 @@ static void usage(FILE *ofp)
 	fprintf(ofp, "  -c, --channel NAME       Apply on channel\n");
 	fprintf(ofp, "  -e, --event NAME         Apply on event\n");
 	fprintf(ofp, "  -k, --kernel             Apply for the kernel tracer\n");
-	fprintf(ofp, "  -u, --userspace          Apply for the user-space tracer\n");
+	fprintf(ofp, "  -u, --userspace [CMD]    Apply for the user-space tracer\n");
 	fprintf(ofp, "      --all                If -u, apply on all traceable apps\n");
 	fprintf(ofp, "  -p, --pid PID            If -u, apply on a specific PID\n");
 	fprintf(ofp, "  -t, --type TYPE          Context type. You can repeat that option on\n");
@@ -356,6 +355,19 @@ static int add_context(char *session_name)
 
 	if (opt_kernel) {
 		dom.type = LTTNG_DOMAIN_KERNEL;
+	} else if (opt_pid != 0) {
+		dom.type = LTTNG_DOMAIN_UST_PID;
+		dom.attr.pid = opt_pid;
+		DBG("PID %d set to lttng handle", opt_pid);
+	} else if (opt_userspace && opt_cmd_name == NULL) {
+		dom.type = LTTNG_DOMAIN_UST;
+	} else if (opt_userspace && opt_cmd_name != NULL) {
+		dom.type = LTTNG_DOMAIN_UST_EXEC_NAME;
+		strncpy(dom.attr.exec_name, opt_cmd_name, NAME_MAX);
+	} else {
+		ERR("Please specify a tracer (--kernel or --userspace)");
+		ret = CMD_NOT_IMPLEMENTED;
+		goto error;
 	}
 
 	handle = lttng_create_handle(session_name, &dom);
@@ -366,7 +378,6 @@ static int add_context(char *session_name)
 
 	/* Iterate over all context type given */
 	cds_list_for_each_entry(type, &ctx_type_list.head, list) {
-
 		context.ctx = type->opt->ctx_type;
 		if (context.ctx == LTTNG_EVENT_CONTEXT_PERF_COUNTER) {
 			context.u.perf_counter.type = type->opt->u.perf.type;
@@ -380,28 +391,18 @@ static int add_context(char *session_name)
 				*ptr = '_';
 			}
 		}
-		if (opt_kernel) {
-			DBG("Adding kernel context");
-			ret = lttng_add_context(handle, &context, opt_event_name,
-					opt_channel_name);
-			if (ret < 0) {
-				fprintf(stderr, "%s: ", type->opt->symbol);
-				continue;
-			} else {
-				MSG("Kernel context %s added", type->opt->symbol);
-			}
-		} else if (opt_userspace) {		/* User-space tracer action */
-			/*
-			 * TODO: Waiting on lttng UST 2.0
-			 */
-			if (opt_pid_all) {
-			} else if (opt_pid != 0) {
-			}
-			ret = CMD_NOT_IMPLEMENTED;
-			goto error;
+		DBG("Adding context...");
+
+		ret = lttng_add_context(handle, &context, opt_event_name,
+				opt_channel_name);
+		if (ret < 0) {
+			fprintf(stderr, "%s: ", type->opt->symbol);
+			continue;
 		} else {
-			ERR("Please specify a tracer (--kernel or --userspace)");
-			goto error;
+			MSG("%s context %s added to %s event in %s",
+					opt_kernel ? "kernel" : "UST", type->opt->symbol,
+					opt_event_name ? opt_event_name : "all",
+					opt_channel_name ? opt_channel_name : "all channels");
 		}
 	}