X-Git-Url: https://git.lttng.org/?p=lttng-tools.git;a=blobdiff_plain;f=src%2Fbin%2Flttng-sessiond%2Ftrace-ust.c;h=4d39e213326b6ce903e459b6bb243d807051696a;hp=8fb685c8d2ab62d4123997fef2be46510e448ebf;hb=1cf992b8ff3eb5bf79e0c209f5e50f16b8d220d9;hpb=0a9c649428b2ea8d4e743aebc12585eeb58fcf64

diff --git a/src/bin/lttng-sessiond/trace-ust.c b/src/bin/lttng-sessiond/trace-ust.c
index 8fb685c8d..4d39e2133 100644
--- a/src/bin/lttng-sessiond/trace-ust.c
+++ b/src/bin/lttng-sessiond/trace-ust.c
@@ -15,17 +15,21 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#define _GNU_SOURCE
+#define _LGPL_SOURCE
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
+#include <inttypes.h>
 
 #include <common/common.h>
 #include <common/defaults.h>
 
 #include "buffer-registry.h"
 #include "trace-ust.h"
+#include "utils.h"
+#include "ust-app.h"
+#include "agent.h"
 
 /*
  * Match function for the events hash table lookup.
@@ -66,33 +70,30 @@ int trace_ust_ht_match_event(struct cds_lfht_node *node, const void *_key)
 {
 	struct ltt_ust_event *event;
 	const struct ltt_ust_ht_key *key;
+	int ev_loglevel_value;
+	int ll_match;
 
 	assert(node);
 	assert(_key);
 
 	event = caa_container_of(node, struct ltt_ust_event, node.node);
 	key = _key;
+	ev_loglevel_value = event->attr.loglevel;
 
-	/* Match the 3 elements of the key: name, filter and loglevel. */
+	/* Match the 4 elements of the key: name, filter, loglevel, exclusions. */
 
 	/* Event name */
 	if (strncmp(event->attr.name, key->name, sizeof(event->attr.name)) != 0) {
 		goto no_match;
 	}
 
-	/* Event loglevel. */
-	if (event->attr.loglevel != key->loglevel) {
-		if (event->attr.loglevel_type == LTTNG_UST_LOGLEVEL_ALL
-				&& key->loglevel == 0 && event->attr.loglevel == -1) {
-			/*
-			 * Match is accepted. This is because on event creation, the
-			 * loglevel is set to -1 if the event loglevel type is ALL so 0 and
-			 * -1 are accepted for this loglevel type since 0 is the one set by
-			 * the API when receiving an enable event.
-			 */
-		} else {
-			goto no_match;
-		}
+	/* Event loglevel value and type. */
+	ll_match = loglevels_match(event->attr.loglevel_type,
+		ev_loglevel_value, key->loglevel_type,
+		key->loglevel_value, LTTNG_UST_LOGLEVEL_ALL);
+
+	if (!ll_match) {
+		goto no_match;
 	}
 
 	/* Only one of the filters is NULL, fail. */
@@ -109,6 +110,53 @@ int trace_ust_ht_match_event(struct cds_lfht_node *node, const void *_key)
 		}
 	}
 
+	/* If only one of the exclusions is NULL, fail. */
+	if ((key->exclusion && !event->exclusion) || (!key->exclusion && event->exclusion)) {
+		goto no_match;
+	}
+
+	if (key->exclusion && event->exclusion) {
+		size_t i;
+
+		/* Check exclusion counts first. */
+		if (event->exclusion->count != key->exclusion->count) {
+			goto no_match;
+		}
+
+		/* Compare names individually. */
+		for (i = 0; i < event->exclusion->count; ++i) {
+			size_t j;
+		        bool found = false;
+			const char *name_ev =
+				LTTNG_EVENT_EXCLUSION_NAME_AT(
+					event->exclusion, i);
+
+			/*
+			 * Compare this exclusion name to all the key's
+			 * exclusion names.
+			 */
+			for (j = 0; j < key->exclusion->count; ++j) {
+				const char *name_key =
+					LTTNG_EVENT_EXCLUSION_NAME_AT(
+						key->exclusion, j);
+
+				if (!strncmp(name_ev, name_key,
+						LTTNG_SYMBOL_NAME_LEN)) {
+					/* Names match! */
+					found = true;
+					break;
+				}
+			}
+
+			/*
+			 * If the current exclusion name was not found amongst
+			 * the key's exclusion names, then there's no match.
+			 */
+			if (!found) {
+				goto no_match;
+			}
+		}
+	}
 	/* Match. */
 	return 1;
 
@@ -126,6 +174,13 @@ struct ltt_ust_channel *trace_ust_find_channel_by_name(struct lttng_ht *ht,
 	struct lttng_ht_node_str *node;
 	struct lttng_ht_iter iter;
 
+	/*
+	 * If we receive an empty string for channel name, it means the
+	 * default channel name is requested.
+	 */
+	if (name[0] == '\0')
+		name = DEFAULT_CHANNEL_NAME;
+
 	lttng_ht_lookup(ht, (void *)name, &iter);
 	node = lttng_ht_iter_get_node_str(&iter);
 	if (node == NULL) {
@@ -146,7 +201,9 @@ error:
  * MUST be acquired before calling this.
  */
 struct ltt_ust_event *trace_ust_find_event(struct lttng_ht *ht,
-		char *name, struct lttng_filter_bytecode *filter, int loglevel)
+		char *name, struct lttng_filter_bytecode *filter,
+		enum lttng_ust_loglevel_type loglevel_type, int loglevel_value,
+		struct lttng_event_exclusion *exclusion)
 {
 	struct lttng_ht_node_str *node;
 	struct lttng_ht_iter iter;
@@ -157,7 +214,9 @@ struct ltt_ust_event *trace_ust_find_event(struct lttng_ht *ht,
 
 	key.name = name;
 	key.filter = filter;
-	key.loglevel = loglevel;
+	key.loglevel_type = loglevel_type;
+	key.loglevel_value = loglevel_value;
+	key.exclusion = exclusion;
 
 	cds_lfht_lookup(ht->ht, ht->hash_fct((void *) name, lttng_ht_seed),
 			trace_ust_ht_match_event, &key, &iter.iter);
@@ -175,12 +234,44 @@ error:
 	return NULL;
 }
 
+/*
+ * Lookup an agent in the session agents hash table by domain type and return
+ * the object if found else NULL.
+ *
+ * RCU read side lock must be acquired before calling and only released
+ * once the agent is no longer in scope or being used.
+ */
+struct agent *trace_ust_find_agent(struct ltt_ust_session *session,
+		enum lttng_domain_type domain_type)
+{
+	struct agent *agt = NULL;
+	struct lttng_ht_node_u64 *node;
+	struct lttng_ht_iter iter;
+	uint64_t key;
+
+	assert(session);
+
+	DBG3("Trace ust agent lookup for domain %d", domain_type);
+
+	key = domain_type;
+
+	lttng_ht_lookup(session->agents, &key, &iter);
+	node = lttng_ht_iter_get_node_u64(&iter);
+	if (!node) {
+		goto end;
+	}
+	agt = caa_container_of(node, struct agent, node);
+
+end:
+	return agt;
+}
+
 /*
  * Allocate and initialize a ust session data structure.
  *
  * Return pointer to structure or NULL.
  */
-struct ltt_ust_session *trace_ust_create_session(unsigned int session_id)
+struct ltt_ust_session *trace_ust_create_session(uint64_t session_id)
 {
 	struct ltt_ust_session *lus;
 
@@ -193,7 +284,15 @@ struct ltt_ust_session *trace_ust_create_session(unsigned int session_id)
 
 	/* Init data structure */
 	lus->id = session_id;
-	lus->start_trace = 0;
+	lus->active = 0;
+
+	/* Set default metadata channel attribute. */
+	lus->metadata_attr.overwrite = DEFAULT_CHANNEL_OVERWRITE;
+	lus->metadata_attr.subbuf_size = default_get_metadata_subbuf_size();
+	lus->metadata_attr.num_subbuf = DEFAULT_METADATA_SUBBUF_NUM;
+	lus->metadata_attr.switch_timer_interval = DEFAULT_METADATA_SWITCH_TIMER;
+	lus->metadata_attr.read_timer_interval = DEFAULT_METADATA_READ_TIMER;
+	lus->metadata_attr.output = LTTNG_UST_MMAP;
 
 	/*
 	 * Default buffer type. This can be changed through an enable channel
@@ -201,7 +300,7 @@ struct ltt_ust_session *trace_ust_create_session(unsigned int session_id)
 	 * during the session lifetime which is at the first enable channel and
 	 * only before start. The flag buffer_type_changed indicates the status.
 	 */
-	lus->buffer_type = LTTNG_BUFFER_PER_PID;
+	lus->buffer_type = LTTNG_BUFFER_PER_UID;
 	/* Once set to 1, the buffer_type is immutable for the session. */
 	lus->buffer_type_changed = 0;
 	/* Init it in case it get used after allocation. */
@@ -209,26 +308,21 @@ struct ltt_ust_session *trace_ust_create_session(unsigned int session_id)
 
 	/* Alloc UST global domain channels' HT */
 	lus->domain_global.channels = lttng_ht_new(0, LTTNG_HT_TYPE_STRING);
+	/* Alloc agent hash table. */
+	lus->agents = lttng_ht_new(0, LTTNG_HT_TYPE_U64);
 
 	lus->consumer = consumer_create_output(CONSUMER_DST_LOCAL);
 	if (lus->consumer == NULL) {
 		goto error_consumer;
 	}
 
-	/*
-	 * The tmp_consumer stays NULL until a set_consumer_uri command is
-	 * executed. At this point, the consumer should be nullify until an
-	 * enable_consumer command. This assignment is symbolic since we've zmalloc
-	 * the struct.
-	 */
-	lus->tmp_consumer = NULL;
-
 	DBG2("UST trace session create successful");
 
 	return lus;
 
 error_consumer:
-	lttng_ht_destroy(lus->domain_global.channels);
+	ht_cleanup_push(lus->domain_global.channels);
+	ht_cleanup_push(lus->agents);
 	free(lus);
 error:
 	return NULL;
@@ -239,7 +333,8 @@ error:
  *
  * Return pointer to structure or NULL.
  */
-struct ltt_ust_channel *trace_ust_create_channel(struct lttng_channel *chan)
+struct ltt_ust_channel *trace_ust_create_channel(struct lttng_channel *chan,
+		enum lttng_domain_type domain)
 {
 	struct ltt_ust_channel *luc;
 
@@ -251,6 +346,8 @@ struct ltt_ust_channel *trace_ust_create_channel(struct lttng_channel *chan)
 		goto error;
 	}
 
+	luc->domain = domain;
+
 	/* Copy UST channel attributes */
 	luc->attr.overwrite = chan->attr.overwrite;
 	luc->attr.subbuf_size = chan->attr.subbuf_size;
@@ -266,12 +363,22 @@ struct ltt_ust_channel *trace_ust_create_channel(struct lttng_channel *chan)
 		break;
 	}
 
-	/* Copy channel name */
-	strncpy(luc->name, chan->name, sizeof(luc->name));
+	/*
+	 * If we receive an empty string for channel name, it means the
+	 * default channel name is requested.
+	 */
+	if (chan->name[0] == '\0') {
+		strncpy(luc->name, DEFAULT_CHANNEL_NAME, sizeof(luc->name));
+	} else {
+		/* Copy channel name */
+		strncpy(luc->name, chan->name, sizeof(luc->name));
+	}
 	luc->name[LTTNG_UST_SYM_NAME_LEN - 1] = '\0';
 
 	/* Init node */
 	lttng_ht_node_init_str(&luc->node, luc->name);
+	CDS_INIT_LIST_HEAD(&luc->ctx_list);
+
 	/* Alloc hash tables */
 	luc->events = lttng_ht_new(0, LTTNG_HT_TYPE_STRING);
 	luc->ctx = lttng_ht_new(0, LTTNG_HT_TYPE_ULONG);
@@ -286,24 +393,67 @@ error:
 	return luc;
 }
 
+/*
+ * Validates an exclusion list.
+ *
+ * Returns 0 if valid, negative value if invalid.
+ */
+static int validate_exclusion(struct lttng_event_exclusion *exclusion)
+{
+	size_t i;
+	int ret = 0;
+
+	assert(exclusion);
+
+	for (i = 0; i < exclusion->count; ++i) {
+		size_t j;
+		const char *name_a =
+			LTTNG_EVENT_EXCLUSION_NAME_AT(exclusion, i);
+
+		for (j = 0; j < i; ++j) {
+			const char *name_b =
+				LTTNG_EVENT_EXCLUSION_NAME_AT(exclusion, j);
+
+			if (!strncmp(name_a, name_b, LTTNG_SYMBOL_NAME_LEN)) {
+				/* Match! */
+				ret = -1;
+				goto end;
+			}
+		}
+	}
+
+end:
+	return ret;
+}
+
 /*
  * Allocate and initialize a ust event. Set name and event type.
+ * We own filter_expression, filter, and exclusion.
  *
  * Return pointer to structure or NULL.
  */
 struct ltt_ust_event *trace_ust_create_event(struct lttng_event *ev,
-		struct lttng_filter_bytecode *filter)
+		char *filter_expression,
+		struct lttng_filter_bytecode *filter,
+		struct lttng_event_exclusion *exclusion,
+		bool internal_event)
 {
 	struct ltt_ust_event *lue;
 
 	assert(ev);
 
+	if (exclusion && validate_exclusion(exclusion)) {
+		goto error;
+	}
+
 	lue = zmalloc(sizeof(struct ltt_ust_event));
 	if (lue == NULL) {
 		PERROR("ust event zmalloc");
 		goto error;
 	}
 
+	lue->internal = internal_event;
+
 	switch (ev->type) {
 	case LTTNG_EVENT_PROBE:
 		lue->attr.instrumentation = LTTNG_UST_PROBE;
@@ -345,7 +495,9 @@ struct ltt_ust_event *trace_ust_create_event(struct lttng_event *ev,
 	}
 
 	/* Same layout. */
-	lue->filter = (struct lttng_ust_filter_bytecode *) filter;
+	lue->filter_expression = filter_expression;
+	lue->filter = filter;
+	lue->exclusion = exclusion;
 
 	/* Init node */
 	lttng_ht_node_init_str(&lue->node, lue->attr.name);
@@ -359,49 +511,84 @@ struct ltt_ust_event *trace_ust_create_event(struct lttng_event *ev,
 error_free_event:
 	free(lue);
 error:
+	free(filter_expression);
+	free(filter);
+	free(exclusion);
 	return NULL;
 }
 
-/*
- * Allocate and initialize a ust metadata.
- *
- * Return pointer to structure or NULL.
- */
-struct ltt_ust_metadata *trace_ust_create_metadata(char *path)
+static
+int trace_ust_context_type_event_to_ust(enum lttng_event_context_type type)
 {
-	int ret;
-	struct ltt_ust_metadata *lum;
+	int utype;
 
-	assert(path);
-
-	lum = zmalloc(sizeof(struct ltt_ust_metadata));
-	if (lum == NULL) {
-		PERROR("ust metadata zmalloc");
-		goto error;
+	switch (type) {
+	case LTTNG_EVENT_CONTEXT_VTID:
+		utype = LTTNG_UST_CONTEXT_VTID;
+		break;
+	case LTTNG_EVENT_CONTEXT_VPID:
+		utype = LTTNG_UST_CONTEXT_VPID;
+		break;
+	case LTTNG_EVENT_CONTEXT_PTHREAD_ID:
+		utype = LTTNG_UST_CONTEXT_PTHREAD_ID;
+		break;
+	case LTTNG_EVENT_CONTEXT_PROCNAME:
+		utype = LTTNG_UST_CONTEXT_PROCNAME;
+		break;
+	case LTTNG_EVENT_CONTEXT_IP:
+		utype = LTTNG_UST_CONTEXT_IP;
+		break;
+	case LTTNG_EVENT_CONTEXT_PERF_THREAD_COUNTER:
+		if (!ustctl_has_perf_counters()) {
+			utype = -1;
+			WARN("Perf counters not implemented in UST");
+		} else {
+			utype = LTTNG_UST_CONTEXT_PERF_THREAD_COUNTER;
+		}
+		break;
+	default:
+		utype = -1;
+		break;
 	}
+	return utype;
+}
 
-	/* Set default attributes */
-	lum->attr.overwrite = DEFAULT_CHANNEL_OVERWRITE;
-	lum->attr.subbuf_size = default_get_metadata_subbuf_size();
-	lum->attr.num_subbuf = DEFAULT_METADATA_SUBBUF_NUM;
-	lum->attr.switch_timer_interval = DEFAULT_METADATA_SWITCH_TIMER;
-	lum->attr.read_timer_interval = DEFAULT_METADATA_READ_TIMER;
-	lum->attr.output = LTTNG_UST_MMAP;
+/*
+ * Return 1 if contexts match, 0 otherwise.
+ */
+int trace_ust_match_context(struct ltt_ust_context *uctx,
+		struct lttng_event_context *ctx)
+{
+	int utype;
 
-	lum->handle = -1;
-	/* Set metadata trace path */
-	ret = snprintf(lum->pathname, PATH_MAX, "%s/" DEFAULT_METADATA_NAME, path);
-	if (ret < 0) {
-		PERROR("asprintf ust metadata");
-		goto error_free_metadata;
+	utype = trace_ust_context_type_event_to_ust(ctx->ctx);
+	if (utype < 0) {
+		return 0;
 	}
+	if (uctx->ctx.ctx != utype) {
+		return 0;
+	}
+	switch (utype) {
+	case LTTNG_UST_CONTEXT_PERF_THREAD_COUNTER:
+		if (uctx->ctx.u.perf_counter.type
+				!= ctx->u.perf_counter.type) {
+			return 0;
+		}
+		if (uctx->ctx.u.perf_counter.config
+				!= ctx->u.perf_counter.config) {
+			return 0;
+		}
+		if (strncmp(uctx->ctx.u.perf_counter.name,
+				ctx->u.perf_counter.name,
+				LTTNG_UST_SYM_NAME_LEN)) {
+			return 0;
+		}
+		break;
+	default:
+		break;
 
-	return lum;
-
-error_free_metadata:
-	free(lum);
-error:
-	return NULL;
+	}
+	return 1;
 }
 
 /*
@@ -413,24 +600,12 @@ struct ltt_ust_context *trace_ust_create_context(
 		struct lttng_event_context *ctx)
 {
 	struct ltt_ust_context *uctx;
-	enum lttng_ust_context_type utype;
+	int utype;
 
 	assert(ctx);
 
-	switch (ctx->ctx) {
-	case LTTNG_EVENT_CONTEXT_VTID:
-		utype = LTTNG_UST_CONTEXT_VTID;
-		break;
-	case LTTNG_EVENT_CONTEXT_VPID:
-		utype = LTTNG_UST_CONTEXT_VPID;
-		break;
-	case LTTNG_EVENT_CONTEXT_PTHREAD_ID:
-		utype = LTTNG_UST_CONTEXT_PTHREAD_ID;
-		break;
-	case LTTNG_EVENT_CONTEXT_PROCNAME:
-		utype = LTTNG_UST_CONTEXT_PROCNAME;
-		break;
-	default:
+	utype = trace_ust_context_type_event_to_ust(ctx->ctx);
+	if (utype < 0) {
 		ERR("Invalid UST context");
 		return NULL;
 	}
@@ -441,7 +616,18 @@ struct ltt_ust_context *trace_ust_create_context(
 		goto error;
 	}
 
-	uctx->ctx.ctx = utype;
+	uctx->ctx.ctx = (enum lttng_ust_context_type) utype;
+	switch (utype) {
+	case LTTNG_UST_CONTEXT_PERF_THREAD_COUNTER:
+		uctx->ctx.u.perf_counter.type = ctx->u.perf_counter.type;
+		uctx->ctx.u.perf_counter.config = ctx->u.perf_counter.config;
+		strncpy(uctx->ctx.u.perf_counter.name, ctx->u.perf_counter.name,
+				LTTNG_UST_SYM_NAME_LEN);
+		uctx->ctx.u.perf_counter.name[LTTNG_UST_SYM_NAME_LEN - 1] = '\0';
+		break;
+	default:
+		break;
+	}
 	lttng_ht_node_init_ulong(&uctx->node, (unsigned long) uctx->ctx.ctx);
 
 	return uctx;
@@ -450,6 +636,291 @@ error:
 	return NULL;
 }
 
+static
+void destroy_pid_tracker_node_rcu(struct rcu_head *head)
+{
+	struct ust_pid_tracker_node *tracker_node =
+		caa_container_of(head, struct ust_pid_tracker_node, node.head);
+	free(tracker_node);
+}
+
+static
+void destroy_pid_tracker_node(struct ust_pid_tracker_node *tracker_node)
+{
+
+	call_rcu(&tracker_node->node.head, destroy_pid_tracker_node_rcu);
+}
+
+static
+int init_pid_tracker(struct ust_pid_tracker *pid_tracker)
+{
+	int ret = 0;
+
+	pid_tracker->ht = lttng_ht_new(0, LTTNG_HT_TYPE_ULONG);
+	if (!pid_tracker->ht) {
+		ret = -1;
+		goto end;
+	}
+
+end:
+	return ret;
+}
+
+/*
+ * Teardown pid tracker content, but don't free pid_tracker object.
+ */
+static
+void fini_pid_tracker(struct ust_pid_tracker *pid_tracker)
+{
+	struct ust_pid_tracker_node *tracker_node;
+	struct lttng_ht_iter iter;
+
+	if (!pid_tracker->ht) {
+		return;
+	}
+	rcu_read_lock();
+	cds_lfht_for_each_entry(pid_tracker->ht->ht,
+			&iter.iter, tracker_node, node.node) {
+		int ret = lttng_ht_del(pid_tracker->ht, &iter);
+
+		assert(!ret);
+		destroy_pid_tracker_node(tracker_node);
+	}
+	rcu_read_unlock();
+	ht_cleanup_push(pid_tracker->ht);
+	pid_tracker->ht = NULL;
+}
+
+static
+struct ust_pid_tracker_node *pid_tracker_lookup(
+		struct ust_pid_tracker *pid_tracker, int pid,
+		struct lttng_ht_iter *iter)
+{
+	unsigned long _pid = (unsigned long) pid;
+	struct lttng_ht_node_ulong *node;
+
+	lttng_ht_lookup(pid_tracker->ht, (void *) _pid, iter);
+	node = lttng_ht_iter_get_node_ulong(iter);
+	if (node) {
+		return caa_container_of(node, struct ust_pid_tracker_node,
+			node);
+	} else {
+		return NULL;
+	}
+}
+
+static
+int pid_tracker_add_pid(struct ust_pid_tracker *pid_tracker, int pid)
+{
+	int retval = LTTNG_OK;
+	struct ust_pid_tracker_node *tracker_node;
+	struct lttng_ht_iter iter;
+
+	if (pid < 0) {
+		retval = LTTNG_ERR_INVALID;
+		goto end;
+	}
+	tracker_node = pid_tracker_lookup(pid_tracker, pid, &iter);
+	if (tracker_node) {
+		/* Already exists. */
+		retval = LTTNG_ERR_PID_TRACKED;
+		goto end;
+	}
+	tracker_node = zmalloc(sizeof(*tracker_node));
+	if (!tracker_node) {
+		retval = LTTNG_ERR_NOMEM;
+		goto end;
+	}
+	lttng_ht_node_init_ulong(&tracker_node->node, (unsigned long) pid);
+	lttng_ht_add_unique_ulong(pid_tracker->ht, &tracker_node->node);
+end:
+	return retval;
+}
+
+static
+int pid_tracker_del_pid(struct ust_pid_tracker *pid_tracker, int pid)
+{
+	int retval = LTTNG_OK, ret;
+	struct ust_pid_tracker_node *tracker_node;
+	struct lttng_ht_iter iter;
+
+	if (pid < 0) {
+		retval = LTTNG_ERR_INVALID;
+		goto end;
+	}
+	tracker_node = pid_tracker_lookup(pid_tracker, pid, &iter);
+	if (!tracker_node) {
+		/* Not found */
+		retval = LTTNG_ERR_PID_NOT_TRACKED;
+		goto end;
+	}
+	ret = lttng_ht_del(pid_tracker->ht, &iter);
+	assert(!ret);
+
+	destroy_pid_tracker_node(tracker_node);
+end:
+	return retval;
+}
+
+/*
+ * The session lock is held when calling this function.
+ */
+int trace_ust_pid_tracker_lookup(struct ltt_ust_session *session, int pid)
+{
+	struct lttng_ht_iter iter;
+
+	if (!session->pid_tracker.ht) {
+		return 1;
+	}
+	if (pid_tracker_lookup(&session->pid_tracker, pid, &iter)) {
+		return 1;
+	}
+	return 0;
+}
+
+/*
+ * Called with the session lock held.
+ */
+int trace_ust_track_pid(struct ltt_ust_session *session, int pid)
+{
+	int retval = LTTNG_OK;
+
+	if (pid == -1) {
+		/* Track all pids: destroy tracker if exists. */
+		if (session->pid_tracker.ht) {
+			fini_pid_tracker(&session->pid_tracker);
+			/* Ensure all apps have session. */
+			ust_app_global_update_all(session);
+		}
+	} else {
+		int ret;
+
+		if (!session->pid_tracker.ht) {
+			/* Create tracker. */
+			if (init_pid_tracker(&session->pid_tracker)) {
+				ERR("Error initializing PID tracker");
+				retval = LTTNG_ERR_NOMEM;
+				goto end;
+			}
+			ret = pid_tracker_add_pid(&session->pid_tracker, pid);
+			if (ret != LTTNG_OK) {
+				retval = ret;
+				fini_pid_tracker(&session->pid_tracker);
+				goto end;
+			}
+			/* Remove all apps from session except pid. */
+			ust_app_global_update_all(session);
+		} else {
+			struct ust_app *app;
+
+			ret = pid_tracker_add_pid(&session->pid_tracker, pid);
+			if (ret != LTTNG_OK) {
+				retval = ret;
+				goto end;
+			}
+			/* Add session to application */
+			app = ust_app_find_by_pid(pid);
+			if (app) {
+				ust_app_global_update(session, app);
+			}
+		}
+	}
+end:
+	return retval;
+}
+
+/*
+ * Called with the session lock held.
+ */
+int trace_ust_untrack_pid(struct ltt_ust_session *session, int pid)
+{
+	int retval = LTTNG_OK;
+
+	if (pid == -1) {
+		/* Create empty tracker, replace old tracker. */
+		struct ust_pid_tracker tmp_tracker;
+
+		tmp_tracker = session->pid_tracker;
+		if (init_pid_tracker(&session->pid_tracker)) {
+			ERR("Error initializing PID tracker");
+			retval = LTTNG_ERR_NOMEM;
+			/* Rollback operation. */
+			session->pid_tracker = tmp_tracker;
+			goto end;
+		}
+		fini_pid_tracker(&tmp_tracker);
+
+		/* Remove session from all applications */
+		ust_app_global_update_all(session);
+	} else {
+		int ret;
+		struct ust_app *app;
+
+		if (!session->pid_tracker.ht) {
+			/* No PID being tracked. */
+			retval = LTTNG_ERR_PID_NOT_TRACKED;
+			goto end;
+		}
+		/* Remove PID from tracker */
+		ret = pid_tracker_del_pid(&session->pid_tracker, pid);
+		if (ret != LTTNG_OK) {
+			retval = ret;
+			goto end;
+		}
+		/* Remove session from application. */
+		app = ust_app_find_by_pid(pid);
+		if (app) {
+			ust_app_global_update(session, app);
+		}
+	}
+end:
+	return retval;
+}
+
+/*
+ * Called with session lock held.
+ */
+ssize_t trace_ust_list_tracker_pids(struct ltt_ust_session *session,
+		int32_t **_pids)
+{
+	struct ust_pid_tracker_node *tracker_node;
+	struct lttng_ht_iter iter;
+	unsigned long count, i = 0;
+	long approx[2];
+	int32_t *pids;
+	int ret = 0;
+
+	if (!session->pid_tracker.ht) {
+		/* Tracker disabled. Set first entry to -1. */
+		pids = zmalloc(sizeof(*pids));
+		if (!pids) {
+			ret = -1;
+			goto end;
+		}
+		pids[0] = -1;
+		*_pids = pids;
+		return 1;
+	}
+
+	rcu_read_lock();
+	cds_lfht_count_nodes(session->pid_tracker.ht->ht,
+		&approx[0], &count, &approx[1]);
+	pids = zmalloc(sizeof(*pids) * count);
+	if (!pids) {
+		ret = -1;
+		goto end;
+	}
+	cds_lfht_for_each_entry(session->pid_tracker.ht->ht,
+			&iter.iter, tracker_node, node.node) {
+		pids[i++] = tracker_node->node.key;
+	}
+	*_pids = pids;
+	ret = count;
+end:
+	rcu_read_unlock();
+	return ret;
+}
+
 /*
  * RCU safe free context structure.
  */
@@ -471,11 +942,16 @@ static void destroy_contexts(struct lttng_ht *ht)
 	int ret;
 	struct lttng_ht_node_ulong *node;
 	struct lttng_ht_iter iter;
+	struct ltt_ust_context *ctx;
 
 	assert(ht);
 
 	rcu_read_lock();
 	cds_lfht_for_each_entry(ht->ht, &iter.iter, node, node) {
+		/* Remove from ordered list. */
+		ctx = caa_container_of(node, struct ltt_ust_context, node);
+		cds_list_del(&ctx->list);
+		/* Remove from channel's hash table. */
 		ret = lttng_ht_del(ht, &iter);
 		if (!ret) {
 			call_rcu(&node->head, destroy_context_rcu);
@@ -483,7 +959,7 @@ static void destroy_contexts(struct lttng_ht *ht)
 	}
 	rcu_read_unlock();
 
-	lttng_ht_destroy(ht);
+	ht_cleanup_push(ht);
 }
 
 /*
@@ -494,7 +970,9 @@ void trace_ust_destroy_event(struct ltt_ust_event *event)
 	assert(event);
 
 	DBG2("Trace destroy UST event %s", event->attr.name);
+	free(event->filter_expression);
 	free(event->filter);
+	free(event->exclusion);
 	free(event);
 }
 
@@ -530,7 +1008,7 @@ static void destroy_events(struct lttng_ht *events)
 	}
 	rcu_read_unlock();
 
-	lttng_ht_destroy(events);
+	ht_cleanup_push(events);
 }
 
 /*
@@ -544,11 +1022,6 @@ static void _trace_ust_destroy_channel(struct ltt_ust_channel *channel)
 
 	DBG2("Trace destroy UST channel %s", channel->name);
 
-	/* Destroying all events of the channel */
-	destroy_events(channel->events);
-	/* Destroying all context of the channel */
-	destroy_contexts(channel->ctx);
-
 	free(channel);
 }
 
@@ -567,21 +1040,29 @@ static void destroy_channel_rcu(struct rcu_head *head)
 
 void trace_ust_destroy_channel(struct ltt_ust_channel *channel)
 {
+	/* Destroying all events of the channel */
+	destroy_events(channel->events);
+	/* Destroying all context of the channel */
+	destroy_contexts(channel->ctx);
+
 	call_rcu(&channel->node.head, destroy_channel_rcu);
 }
 
 /*
- * Cleanup ust metadata structure.
+ * Remove an UST channel from a channel HT.
  */
-void trace_ust_destroy_metadata(struct ltt_ust_metadata *metadata)
+void trace_ust_delete_channel(struct lttng_ht *ht,
+		struct ltt_ust_channel *channel)
 {
-	assert(metadata);
+	int ret;
+	struct lttng_ht_iter iter;
 
-	if (!metadata->handle) {
-		return;
-	}
-	DBG2("Trace UST destroy metadata %d", metadata->handle);
-	free(metadata);
+	assert(ht);
+	assert(channel);
+
+	iter.iter.node = &channel->node.node;
+	ret = lttng_ht_del(ht, &iter);
+	assert(!ret);
 }
 
 /*
@@ -589,22 +1070,22 @@ void trace_ust_destroy_metadata(struct ltt_ust_metadata *metadata)
  */
 static void destroy_channels(struct lttng_ht *channels)
 {
-	int ret;
 	struct lttng_ht_node_str *node;
 	struct lttng_ht_iter iter;
 
 	assert(channels);
 
 	rcu_read_lock();
-
 	cds_lfht_for_each_entry(channels->ht, &iter.iter, node, node) {
-		ret = lttng_ht_del(channels, &iter);
-		assert(!ret);
-		call_rcu(&node->head, destroy_channel_rcu);
+		struct ltt_ust_channel *chan =
+			caa_container_of(node, struct ltt_ust_channel, node);
+
+		trace_ust_delete_channel(channels, chan);
+		trace_ust_destroy_channel(chan);
 	}
 	rcu_read_unlock();
 
-	lttng_ht_destroy(channels);
+	ht_cleanup_push(channels);
 }
 
 /*
@@ -624,15 +1105,28 @@ static void destroy_domain_global(struct ltt_ust_domain_global *dom)
  */
 void trace_ust_destroy_session(struct ltt_ust_session *session)
 {
+	struct agent *agt;
 	struct buffer_reg_uid *reg, *sreg;
+	struct lttng_ht_iter iter;
 
 	assert(session);
 
-	DBG2("Trace UST destroy session %u", session->id);
+	DBG2("Trace UST destroy session %" PRIu64, session->id);
 
 	/* Cleaning up UST domain */
 	destroy_domain_global(&session->domain_global);
 
+	rcu_read_lock();
+	cds_lfht_for_each_entry(session->agents->ht, &iter.iter, agt, node.node) {
+		int ret = lttng_ht_del(session->agents, &iter);
+
+		assert(!ret);
+		agent_destroy(agt);
+	}
+	rcu_read_unlock();
+
+	ht_cleanup_push(session->agents);
+
 	/* Cleanup UID buffer registry object(s). */
 	cds_list_for_each_entry_safe(reg, sreg, &session->buffer_reg_uid_list,
 			lnode) {
@@ -641,8 +1135,9 @@ void trace_ust_destroy_session(struct ltt_ust_session *session)
 		buffer_reg_uid_destroy(reg, session->consumer);
 	}
 
-	consumer_destroy_output(session->consumer);
-	consumer_destroy_output(session->tmp_consumer);
+	consumer_output_put(session->consumer);
+
+	fini_pid_tracker(&session->pid_tracker);
 
 	free(session);
 }