Implement consumer ring buffer position sampling
[lttng-tools.git] / src / bin / lttng-sessiond / trace-ust.c
index 0a90cac0ec13aa1d71049d9053217ab0fde0fffe..55ca4fb3c9bfe5fc6b142cc9a5aa51dda4e117c3 100644 (file)
 /*
  * Copyright (C) 2011 - David Goulet <david.goulet@polymtl.ca>
+ * Copyright (C) 2016 - Jérémie Galarneau <jeremie.galarneau@efficios.com>
  *
- * This program is free software; you can redistribute it and/or modify it
- * under the terms of the GNU General Public License as published by the Free
- * Software Foundation; only version 2 of the License.
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License, version 2 only,
+ * as published by the Free Software Foundation.
  *
- * This program is distributed in the hope that it will be useful, but WITHOUT
- * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
- * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
- * more details.
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
  *
- * You should have received a copy of the GNU General Public License along with
- * this program; if not, write to the Free Software Foundation, Inc., 59 Temple
- * Place - Suite 330, Boston, MA  02111-1307, USA.
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 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"
 
 /*
- * Find the channel in the hashtable.
+ * Match function for the events hash table lookup.
+ *
+ * Matches by name only. Used by the disable command.
+ */
+int trace_ust_ht_match_event_by_name(struct cds_lfht_node *node,
+               const void *_key)
+{
+       struct ltt_ust_event *event;
+       const char *name;
+
+       assert(node);
+       assert(_key);
+
+       event = caa_container_of(node, struct ltt_ust_event, node.node);
+       name = _key;
+
+       /* Event name */
+       if (strncmp(event->attr.name, name, sizeof(event->attr.name)) != 0) {
+               goto no_match;
+       }
+
+       /* Match */
+       return 1;
+
+no_match:
+       return 0;
+}
+
+/*
+ * Match function for the hash table lookup.
+ *
+ * It matches an ust event based on three attributes which are the event name,
+ * the filter bytecode and the loglevel.
+ */
+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 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 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. */
+       if ((key->filter && !event->filter) || (!key->filter && event->filter)) {
+               goto no_match;
+       }
+
+       if (key->filter && event->filter) {
+               /* Both filters exists, check length followed by the bytecode. */
+               if (event->filter->len != key->filter->len ||
+                               memcmp(event->filter->data, key->filter->data,
+                                       event->filter->len) != 0) {
+                       goto no_match;
+               }
+       }
+
+       /* 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;
+
+no_match:
+       return 0;
+}
+
+/*
+ * Find the channel in the hashtable and return channel pointer. RCU read side
+ * lock MUST be acquired before calling this.
  */
 struct ltt_ust_channel *trace_ust_find_channel_by_name(struct lttng_ht *ht,
                char *name)
@@ -35,14 +175,18 @@ 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;
 
-       rcu_read_lock();
+       /*
+        * 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) {
-               rcu_read_unlock();
                goto error;
        }
-       rcu_read_unlock();
 
        DBG2("Trace UST channel %s found by name", name);
 
@@ -54,41 +198,82 @@ error:
 }
 
 /*
- * Find the event in the hashtable.
+ * Find the event in the hashtable and return event pointer. RCU read side lock
+ * MUST be acquired before calling this.
  */
-struct ltt_ust_event *trace_ust_find_event_by_name(struct lttng_ht *ht,
-               char *name)
+struct ltt_ust_event *trace_ust_find_event(struct lttng_ht *ht,
+               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;
+       struct ltt_ust_ht_key key;
 
-       rcu_read_lock();
-       lttng_ht_lookup(ht, (void *) name, &iter);
+       assert(name);
+       assert(ht);
+
+       key.name = name;
+       key.filter = filter;
+       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);
        node = lttng_ht_iter_get_node_str(&iter);
        if (node == NULL) {
-               rcu_read_unlock();
                goto error;
        }
-       rcu_read_unlock();
 
-       DBG2("Trace UST event found by name %s", name);
+       DBG2("Trace UST event %s found", key.name);
 
        return caa_container_of(node, struct ltt_ust_event, node);
 
 error:
-       DBG2("Trace UST event NOT found by name %s", name);
+       DBG2("Trace UST event %s NOT found", key.name);
        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(char *path, int session_id,
-               struct lttng_domain *domain)
+struct ltt_ust_session *trace_ust_create_session(uint64_t session_id)
 {
-       int ret;
        struct ltt_ust_session *lus;
 
        /* Allocate a new ltt ust session */
@@ -100,27 +285,45 @@ struct ltt_ust_session *trace_ust_create_session(char *path, int session_id,
 
        /* Init data structure */
        lus->id = session_id;
-       lus->start_trace = 0;
-
-       /* Alloc UST domain hash tables */
-       lus->domain_pid = lttng_ht_new(0, LTTNG_HT_TYPE_ULONG);
-       lus->domain_exec = lttng_ht_new(0, LTTNG_HT_TYPE_ULONG);
+       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
+        * requesting a different type. Note that this can only be changed once
+        * 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_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. */
+       CDS_INIT_LIST_HEAD(&lus->buffer_reg_uid_list);
 
        /* 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);
 
-       /* Set session path */
-       ret = snprintf(lus->pathname, PATH_MAX, "%s/ust", path);
-       if (ret < 0) {
-               PERROR("snprintf kernel traces path");
-               goto error_free_session;
+       lus->consumer = consumer_create_output(CONSUMER_DST_LOCAL);
+       if (lus->consumer == NULL) {
+               goto error_consumer;
        }
 
        DBG2("UST trace session create successful");
 
        return lus;
 
-error_free_session:
+error_consumer:
+       ht_cleanup_push(lus->domain_global.channels);
+       ht_cleanup_push(lus->agents);
        free(lus);
 error:
        return NULL;
@@ -132,24 +335,29 @@ error:
  * Return pointer to structure or NULL.
  */
 struct ltt_ust_channel *trace_ust_create_channel(struct lttng_channel *chan,
-               char *path)
+               enum lttng_domain_type domain)
 {
-       int ret;
        struct ltt_ust_channel *luc;
 
+       assert(chan);
+
        luc = zmalloc(sizeof(struct ltt_ust_channel));
        if (luc == NULL) {
-               perror("ltt_ust_channel zmalloc");
+               PERROR("ltt_ust_channel zmalloc");
                goto error;
        }
 
+       luc->domain = domain;
+
        /* Copy UST channel attributes */
        luc->attr.overwrite = chan->attr.overwrite;
        luc->attr.subbuf_size = chan->attr.subbuf_size;
        luc->attr.num_subbuf = chan->attr.num_subbuf;
        luc->attr.switch_timer_interval = chan->attr.switch_timer_interval;
        luc->attr.read_timer_interval = chan->attr.read_timer_interval;
-       luc->attr.output = chan->attr.output;
+       luc->attr.output = (enum lttng_ust_output) chan->attr.output;
+       luc->monitor_timer_interval =
+                       ((struct lttng_channel_extended *) chan->attr.extended.ptr)->monitor_timer_interval;
 
        /* Translate to UST output enum */
        switch (luc->attr.output) {
@@ -158,48 +366,97 @@ 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);
 
-       /* Set trace output path */
-       ret = snprintf(luc->pathname, PATH_MAX, "%s", path);
-       if (ret < 0) {
-               perror("asprintf ust create channel");
-               goto error_free_channel;
-       }
+       /* On-disk circular buffer parameters */
+       luc->tracefile_size = chan->attr.tracefile_size;
+       luc->tracefile_count = chan->attr.tracefile_count;
 
        DBG2("Trace UST channel %s created", luc->name);
 
+error:
        return luc;
+}
 
-error_free_channel:
-       free(luc);
-error:
-       return NULL;
+/*
+ * 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 ltt_ust_event *trace_ust_create_event(struct lttng_event *ev,
+               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;
@@ -223,74 +480,131 @@ struct ltt_ust_event *trace_ust_create_event(struct lttng_event *ev)
        lue->attr.name[LTTNG_UST_SYM_NAME_LEN - 1] = '\0';
 
        switch (ev->loglevel_type) {
-       case LTTNG_EVENT_LOGLEVEL:
-               lue->attr.loglevel_type = LTTNG_UST_LOGLEVEL;
+       case LTTNG_EVENT_LOGLEVEL_ALL:
+               lue->attr.loglevel_type = LTTNG_UST_LOGLEVEL_ALL;
+               lue->attr.loglevel = -1;        /* Force to -1 */
                break;
-       case LTTNG_EVENT_LOGLEVEL_ONLY:
-               lue->attr.loglevel_type = LTTNG_UST_LOGLEVEL_ONLY;
+       case LTTNG_EVENT_LOGLEVEL_RANGE:
+               lue->attr.loglevel_type = LTTNG_UST_LOGLEVEL_RANGE;
+               lue->attr.loglevel = ev->loglevel;
+               break;
+       case LTTNG_EVENT_LOGLEVEL_SINGLE:
+               lue->attr.loglevel_type = LTTNG_UST_LOGLEVEL_SINGLE;
+               lue->attr.loglevel = ev->loglevel;
                break;
        default:
-               ERR("Unknown ust loglevel type (%d)", ev->type);
+               ERR("Unknown ust loglevel type (%d)", ev->loglevel_type);
                goto error_free_event;
        }
 
-       /* Copy loglevel name */
-       strncpy(lue->attr.loglevel, ev->loglevel, LTTNG_UST_SYM_NAME_LEN);
-       lue->attr.loglevel[LTTNG_UST_SYM_NAME_LEN - 1] = '\0';
+       /* Same layout. */
+       lue->filter_expression = filter_expression;
+       lue->filter = filter;
+       lue->exclusion = exclusion;
 
        /* Init node */
        lttng_ht_node_init_str(&lue->node, lue->attr.name);
-       /* Alloc context hash tables */
-       lue->ctx = lttng_ht_new(0, LTTNG_HT_TYPE_ULONG);
 
-       DBG2("Trace UST event %s created", lue->attr.name);
+       DBG2("Trace UST event %s, loglevel (%d,%d) created",
+               lue->attr.name, lue->attr.loglevel_type,
+               lue->attr.loglevel);
 
        return lue;
 
 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;
 
-       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;
+       case LTTNG_EVENT_CONTEXT_APP_CONTEXT:
+               utype = LTTNG_UST_CONTEXT_APP_CONTEXT;
+               break;
+       default:
+               utype = -1;
+               break;
        }
+       return utype;
+}
 
-       /* Set default attributes */
-       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 = 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/metadata", 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;
+       case LTTNG_UST_CONTEXT_APP_CONTEXT:
+               assert(uctx->ctx.u.app_ctx.provider_name);
+               assert(uctx->ctx.u.app_ctx.ctx_name);
+               if (strcmp(uctx->ctx.u.app_ctx.provider_name,
+                               ctx->u.app_ctx.provider_name) ||
+                               strcmp(uctx->ctx.u.app_ctx.ctx_name,
+                               ctx->u.app_ctx.ctx_name)) {
+                       return 0;
+               }
+       default:
+               break;
 
-       return lum;
-
-error_free_metadata:
-       free(lum);
-error:
-       return NULL;
+       }
+       return 1;
 }
 
 /*
@@ -301,42 +615,345 @@ error:
 struct ltt_ust_context *trace_ust_create_context(
                struct lttng_event_context *ctx)
 {
-       struct ltt_ust_context *uctx;
-       enum lttng_ust_context_type utype;
+       struct ltt_ust_context *uctx = NULL;
+       int utype;
 
-       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:
+       assert(ctx);
+
+       utype = trace_ust_context_type_event_to_ust(ctx->ctx);
+       if (utype < 0) {
                ERR("Invalid UST context");
-               return NULL;
+               goto end;
        }
 
        uctx = zmalloc(sizeof(struct ltt_ust_context));
-       if (uctx == NULL) {
+       if (!uctx) {
                PERROR("zmalloc ltt_ust_context");
-               goto error;
+               goto end;
        }
 
-       uctx->ctx.ctx = utype;
-       lttng_ht_node_init_ulong(&uctx->node, (unsigned long) uctx->ctx.ctx);
+       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;
+       case LTTNG_UST_CONTEXT_APP_CONTEXT:
+       {
+               char *provider_name = NULL, *ctx_name = NULL;
 
-       return uctx;
+               provider_name = strdup(ctx->u.app_ctx.provider_name);
+               if (!provider_name) {
+                       goto error;
+               }
+               uctx->ctx.u.app_ctx.provider_name = provider_name;
 
+               ctx_name = strdup(ctx->u.app_ctx.ctx_name);
+               if (!ctx_name) {
+                       goto error;
+               }
+               uctx->ctx.u.app_ctx.ctx_name = ctx_name;
+               break;
+       }
+       default:
+               break;
+       }
+       lttng_ht_node_init_ulong(&uctx->node, (unsigned long) uctx->ctx.ctx);
+end:
+       return uctx;
 error:
+       trace_ust_destroy_context(uctx);
        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.
  */
@@ -347,7 +964,7 @@ static void destroy_context_rcu(struct rcu_head *head)
        struct ltt_ust_context *ctx =
                caa_container_of(node, struct ltt_ust_context, node);
 
-       free(ctx);
+       trace_ust_destroy_context(ctx);
 }
 
 /*
@@ -358,15 +975,24 @@ 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);
                }
        }
+       rcu_read_unlock();
 
-       lttng_ht_destroy(ht);
+       ht_cleanup_push(ht);
 }
 
 /*
@@ -374,12 +1000,29 @@ static void destroy_contexts(struct lttng_ht *ht)
  */
 void trace_ust_destroy_event(struct ltt_ust_event *event)
 {
-       DBG2("Trace destroy UST event %s", event->attr.name);
-       destroy_contexts(event->ctx);
+       assert(event);
 
+       DBG2("Trace destroy UST event %s", event->attr.name);
+       free(event->filter_expression);
+       free(event->filter);
+       free(event->exclusion);
        free(event);
 }
 
+/*
+ * Cleanup ust context structure.
+ */
+void trace_ust_destroy_context(struct ltt_ust_context *ctx)
+{
+       assert(ctx);
+
+       if (ctx->ctx.ctx == LTTNG_UST_CONTEXT_APP_CONTEXT) {
+               free(ctx->ctx.u.app_ctx.provider_name);
+               free(ctx->ctx.u.app_ctx.ctx_name);
+       }
+       free(ctx);
+}
+
 /*
  * URCU intermediate call to complete destroy event.
  */
@@ -402,32 +1045,31 @@ static void destroy_events(struct lttng_ht *events)
        struct lttng_ht_node_str *node;
        struct lttng_ht_iter iter;
 
+       assert(events);
+
+       rcu_read_lock();
        cds_lfht_for_each_entry(events->ht, &iter.iter, node, node) {
                ret = lttng_ht_del(events, &iter);
                assert(!ret);
                call_rcu(&node->head, destroy_event_rcu);
        }
+       rcu_read_unlock();
 
-       lttng_ht_destroy(events);
+       ht_cleanup_push(events);
 }
 
 /*
  * Cleanup ust channel structure.
+ *
+ * Should _NOT_ be called with RCU read lock held.
  */
-void trace_ust_destroy_channel(struct ltt_ust_channel *channel)
+static void _trace_ust_destroy_channel(struct ltt_ust_channel *channel)
 {
-       DBG2("Trace destroy UST channel %s", channel->name);
-
-       rcu_read_lock();
+       assert(channel);
 
-       /* Destroying all events of the channel */
-       destroy_events(channel->events);
-       /* Destroying all context of the channel */
-       destroy_contexts(channel->ctx);
+       DBG2("Trace destroy UST channel %s", channel->name);
 
        free(channel);
-
-       rcu_read_unlock();
 }
 
 /*
@@ -440,75 +1082,57 @@ static void destroy_channel_rcu(struct rcu_head *head)
        struct ltt_ust_channel *channel =
                caa_container_of(node, struct ltt_ust_channel, node);
 
-       trace_ust_destroy_channel(channel);
+       _trace_ust_destroy_channel(channel);
 }
 
-/*
- * Cleanup ust metadata structure.
- */
-void trace_ust_destroy_metadata(struct ltt_ust_metadata *metadata)
+void trace_ust_destroy_channel(struct ltt_ust_channel *channel)
 {
-       DBG2("Trace UST destroy metadata %d", metadata->handle);
+       /* Destroying all events of the channel */
+       destroy_events(channel->events);
+       /* Destroying all context of the channel */
+       destroy_contexts(channel->ctx);
 
-       free(metadata);
+       call_rcu(&channel->node.head, destroy_channel_rcu);
 }
 
 /*
- * Iterate over a hash table containing channels and cleanup safely.
+ * Remove an UST channel from a channel HT.
  */
-static void destroy_channels(struct lttng_ht *channels)
+void trace_ust_delete_channel(struct lttng_ht *ht,
+               struct ltt_ust_channel *channel)
 {
        int ret;
-       struct lttng_ht_node_str *node;
        struct lttng_ht_iter iter;
 
-       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);
-       }
-
-       lttng_ht_destroy(channels);
+       assert(ht);
+       assert(channel);
 
-       rcu_read_unlock();
+       iter.iter.node = &channel->node.node;
+       ret = lttng_ht_del(ht, &iter);
+       assert(!ret);
 }
 
 /*
- * Cleanup UST pid domain.
+ * Iterate over a hash table containing channels and cleanup safely.
  */
-static void destroy_domain_pid(struct lttng_ht *ht)
+static void destroy_channels(struct lttng_ht *channels)
 {
-       int ret;
+       struct lttng_ht_node_str *node;
        struct lttng_ht_iter iter;
-       struct ltt_ust_domain_pid *dpid;
 
-       cds_lfht_for_each_entry(ht->ht, &iter.iter, dpid, node.node) {
-               ret = lttng_ht_del(ht , &iter);
-               assert(!ret);
-               destroy_channels(dpid->channels);
-       }
+       assert(channels);
 
-       lttng_ht_destroy(ht);
-}
-
-/*
- * Cleanup UST exec name domain.
- */
-static void destroy_domain_exec(struct lttng_ht *ht)
-{
-       int ret;
-       struct lttng_ht_iter iter;
-       struct ltt_ust_domain_exec *dexec;
+       rcu_read_lock();
+       cds_lfht_for_each_entry(channels->ht, &iter.iter, node, node) {
+               struct ltt_ust_channel *chan =
+                       caa_container_of(node, struct ltt_ust_channel, node);
 
-       cds_lfht_for_each_entry(ht->ht, &iter.iter, dexec, node.node) {
-               ret = lttng_ht_del(ht , &iter);
-               assert(!ret);
-               destroy_channels(dexec->channels);
+               trace_ust_delete_channel(channels, chan);
+               trace_ust_destroy_channel(chan);
        }
+       rcu_read_unlock();
 
-       lttng_ht_destroy(ht);
+       ht_cleanup_push(channels);
 }
 
 /*
@@ -516,29 +1140,51 @@ static void destroy_domain_exec(struct lttng_ht *ht)
  */
 static void destroy_domain_global(struct ltt_ust_domain_global *dom)
 {
+       assert(dom);
+
        destroy_channels(dom->channels);
 }
 
 /*
  * Cleanup ust session structure
+ *
+ * Should *NOT* be called with RCU read-side lock held.
  */
 void trace_ust_destroy_session(struct ltt_ust_session *session)
 {
-       /* Extra protection */
-       if (session == NULL) {
-               return;
-       }
+       struct agent *agt;
+       struct buffer_reg_uid *reg, *sreg;
+       struct lttng_ht_iter iter;
 
-       rcu_read_lock();
+       assert(session);
 
-       DBG2("Trace UST destroy session %d", session->id);
+       DBG2("Trace UST destroy session %" PRIu64, session->id);
 
        /* Cleaning up UST domain */
        destroy_domain_global(&session->domain_global);
-       destroy_domain_pid(session->domain_pid);
-       destroy_domain_exec(session->domain_exec);
 
-       free(session);
+       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) {
+               cds_list_del(&reg->lnode);
+               buffer_reg_uid_remove(reg);
+               buffer_reg_uid_destroy(reg, session->consumer);
+       }
+
+       consumer_output_put(session->consumer);
+
+       fini_pid_tracker(&session->pid_tracker);
+
+       free(session);
 }
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