lttng.h API update: set filter becomes enable event with filter
[lttng-tools.git] / src / bin / lttng-sessiond / ust-app.c
index 8e6d20e86d8f19dec7d63d1a1a7b2e155ef86153..c81f6e8f5597e1531292cfee2e4f5b5f57faf0dd 100644 (file)
 #include <sys/types.h>
 #include <unistd.h>
 #include <urcu/compiler.h>
+#include <lttng/ust-error.h>
 
 #include <common/common.h>
+#include <common/sessiond-comm/sessiond-comm.h>
 
+#include "fd-limit.h"
+#include "health.h"
 #include "ust-app.h"
 #include "ust-consumer.h"
 #include "ust-ctl.h"
 
+/*
+ * Match function for the hash table lookup.
+ *
+ * It matches an ust app event based on three attributes which are the event
+ * name, the filter bytecode and the loglevel.
+ */
+static int ht_match_ust_app_event(struct cds_lfht_node *node, const void *_key)
+{
+       struct ust_app_event *event;
+       const struct ust_app_ht_key *key;
+
+       assert(node);
+       assert(_key);
+
+       event = caa_container_of(node, struct ust_app_event, node.node);
+       key = _key;
+
+       /* Match the 3 elements of the key: name, filter and loglevel. */
+
+       /* 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;
+               }
+       }
+
+       /* 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;
+               }
+       }
+
+       /* Match. */
+       return 1;
+
+no_match:
+       return 0;
+}
+
+/*
+ * Unique add of an ust app event in the given ht. This uses the custom
+ * ht_match_ust_app_event match function and the event name as hash.
+ */
+static void add_unique_ust_app_event(struct lttng_ht *ht,
+               struct ust_app_event *event)
+{
+       struct cds_lfht_node *node_ptr;
+       struct ust_app_ht_key key;
+
+       assert(ht);
+       assert(ht->ht);
+       assert(event);
+
+       key.name = event->attr.name;
+       key.filter = event->filter;
+       key.loglevel = event->attr.loglevel;
+
+       node_ptr = cds_lfht_add_unique(ht->ht,
+                       ht->hash_fct(event->node.key, lttng_ht_seed),
+                       ht_match_ust_app_event, &key, &event->node.node);
+       assert(node_ptr == &event->node.node);
+}
+
 /*
  * Delete ust context safely. RCU read lock must be held before calling
  * this function.
@@ -53,18 +141,7 @@ void delete_ust_app_ctx(int sock, struct ust_app_ctx *ua_ctx)
 static
 void delete_ust_app_event(int sock, struct ust_app_event *ua_event)
 {
-       int ret;
-       struct lttng_ht_iter iter;
-       struct ust_app_ctx *ua_ctx;
-
-       /* Destroy each context of event */
-       cds_lfht_for_each_entry(ua_event->ctx->ht, &iter.iter, ua_ctx,
-                       node.node) {
-               ret = lttng_ht_del(ua_event->ctx, &iter);
-               assert(!ret);
-               delete_ust_app_ctx(sock, ua_ctx);
-       }
-       lttng_ht_destroy(ua_event->ctx);
+       free(ua_event->filter);
 
        if (ua_event->obj != NULL) {
                ustctl_release_object(sock, ua_event->obj);
@@ -82,6 +159,7 @@ void delete_ust_app_stream(int sock, struct ltt_ust_stream *stream)
 {
        if (stream->obj) {
                ustctl_release_object(sock, stream->obj);
+               lttng_fd_put(LTTNG_FD_APPS, 2);
                free(stream->obj);
        }
        free(stream);
@@ -125,6 +203,7 @@ void delete_ust_app_channel(int sock, struct ust_app_channel *ua_chan)
 
        if (ua_chan->obj != NULL) {
                ustctl_release_object(sock, ua_chan->obj);
+               lttng_fd_put(LTTNG_FD_APPS, 2);
                free(ua_chan->obj);
        }
        free(ua_chan);
@@ -144,12 +223,15 @@ void delete_ust_app_session(int sock, struct ust_app_session *ua_sess)
        if (ua_sess->metadata) {
                if (ua_sess->metadata->stream_obj) {
                        ustctl_release_object(sock, ua_sess->metadata->stream_obj);
+                       lttng_fd_put(LTTNG_FD_APPS, 2);
                        free(ua_sess->metadata->stream_obj);
                }
                if (ua_sess->metadata->obj) {
                        ustctl_release_object(sock, ua_sess->metadata->obj);
+                       lttng_fd_put(LTTNG_FD_APPS, 2);
                        free(ua_sess->metadata->obj);
                }
+               trace_ust_destroy_metadata(ua_sess->metadata);
        }
 
        cds_lfht_for_each_entry(ua_sess->channels->ht, &iter.iter, ua_chan,
@@ -180,29 +262,38 @@ void delete_ust_app(struct ust_app *app)
        rcu_read_lock();
 
        /* Delete ust app sessions info */
-       sock = app->key.sock;
-       app->key.sock = -1;
+       sock = app->sock;
+       app->sock = -1;
 
        /* Wipe sessions */
        cds_lfht_for_each_entry(app->sessions->ht, &iter.iter, ua_sess,
                        node.node) {
                ret = lttng_ht_del(app->sessions, &iter);
                assert(!ret);
-               delete_ust_app_session(app->key.sock, ua_sess);
+               delete_ust_app_session(app->sock, ua_sess);
        }
        lttng_ht_destroy(app->sessions);
 
        /*
-        * Wait until we have removed the key from the sock hash table before
-        * closing this socket, otherwise an application could re-use the socket ID
-        * and race with the teardown, using the same hash table entry.
+        * Wait until we have deleted the application from the sock hash table
+        * before closing this socket, otherwise an application could re-use the
+        * socket ID and race with the teardown, using the same hash table entry.
+        *
+        * It's OK to leave the close in call_rcu. We want it to stay unique for
+        * all RCU readers that could run concurrently with unregister app,
+        * therefore we _need_ to only close that socket after a grace period. So
+        * it should stay in this RCU callback.
+        *
+        * This close() is a very important step of the synchronization model so
+        * every modification to this function must be carefully reviewed.
         */
        ret = close(sock);
        if (ret) {
                PERROR("close");
        }
+       lttng_fd_put(LTTNG_FD_APPS, 1);
 
-       DBG2("UST app pid %d deleted", app->key.pid);
+       DBG2("UST app pid %d deleted", app->pid);
        free(app);
 
        rcu_read_unlock();
@@ -217,9 +308,9 @@ void delete_ust_app_rcu(struct rcu_head *head)
        struct lttng_ht_node_ulong *node =
                caa_container_of(head, struct lttng_ht_node_ulong, head);
        struct ust_app *app =
-               caa_container_of(node, struct ust_app, node);
+               caa_container_of(node, struct ust_app, pid_n);
 
-       DBG3("Call RCU deleting app PID %d", app->key.pid);
+       DBG3("Call RCU deleting app PID %d", app->pid);
        delete_ust_app(app);
 }
 
@@ -307,7 +398,6 @@ struct ust_app_event *alloc_ust_app_event(char *name,
        ua_event->enabled = 1;
        strncpy(ua_event->name, name, sizeof(ua_event->name));
        ua_event->name[sizeof(ua_event->name) - 1] = '\0';
-       ua_event->ctx = lttng_ht_new(0, LTTNG_HT_TYPE_ULONG);
        lttng_ht_node_init_str(&ua_event->node, ua_event->name);
 
        /* Copy attributes */
@@ -346,6 +436,29 @@ error:
        return ua_ctx;
 }
 
+/*
+ * Allocate a filter and copy the given original filter.
+ *
+ * Return allocated filter or NULL on error.
+ */
+static struct lttng_ust_filter_bytecode *alloc_copy_ust_app_filter(
+               struct lttng_ust_filter_bytecode *orig_f)
+{
+       struct lttng_ust_filter_bytecode *filter = NULL;
+
+       /* Copy filter bytecode */
+       filter = zmalloc(sizeof(*filter) + orig_f->len);
+       if (!filter) {
+               PERROR("zmalloc alloc ust app filter");
+               goto error;
+       }
+
+       memcpy(filter, orig_f, sizeof(*filter) + orig_f->len);
+
+error:
+       return filter;
+}
+
 /*
  * Find an ust_app using the sock and return it. RCU read side lock must be
  * held before calling this helper function.
@@ -354,30 +467,57 @@ static
 struct ust_app *find_app_by_sock(int sock)
 {
        struct lttng_ht_node_ulong *node;
-       struct ust_app_key *key;
        struct lttng_ht_iter iter;
 
-       lttng_ht_lookup(ust_app_sock_key_map, (void *)((unsigned long) sock),
-                       &iter);
-       node = lttng_ht_iter_get_node_ulong(&iter);
-       if (node == NULL) {
-               DBG2("UST app find by sock %d key not found", sock);
-               goto error;
-       }
-       key = caa_container_of(node, struct ust_app_key, node);
-
-       lttng_ht_lookup(ust_app_ht, (void *)((unsigned long) key->pid), &iter);
+       lttng_ht_lookup(ust_app_ht_by_sock, (void *)((unsigned long) sock), &iter);
        node = lttng_ht_iter_get_node_ulong(&iter);
        if (node == NULL) {
                DBG2("UST app find by sock %d not found", sock);
                goto error;
        }
-       return caa_container_of(node, struct ust_app, node);
+
+       return caa_container_of(node, struct ust_app, sock_n);
 
 error:
        return NULL;
 }
 
+/*
+ * Lookup for an ust app event based on event name, filter bytecode and the
+ * event loglevel.
+ *
+ * Return an ust_app_event object or NULL on error.
+ */
+static struct ust_app_event *find_ust_app_event(struct lttng_ht *ht,
+               char *name, struct lttng_ust_filter_bytecode *filter, int loglevel)
+{
+       struct lttng_ht_iter iter;
+       struct lttng_ht_node_str *node;
+       struct ust_app_event *event = NULL;
+       struct ust_app_ht_key key;
+
+       assert(name);
+       assert(ht);
+
+       /* Setup key for event lookup. */
+       key.name = name;
+       key.filter = filter;
+       key.loglevel = loglevel;
+
+       /* Lookup using the event name as hash and a custom match fct. */
+       cds_lfht_lookup(ht->ht, ht->hash_fct((void *) name, lttng_ht_seed),
+                       ht_match_ust_app_event, &key, &iter.iter);
+       node = lttng_ht_iter_get_node_str(&iter);
+       if (node == NULL) {
+               goto end;
+       }
+
+       event = caa_container_of(node, struct ust_app_event, node);
+
+end:
+       return event;
+}
+
 /*
  * Create the channel context on the tracer.
  */
@@ -387,7 +527,9 @@ int create_ust_channel_context(struct ust_app_channel *ua_chan,
 {
        int ret;
 
-       ret = ustctl_add_context(app->key.sock, &ua_ctx->ctx,
+       health_code_update(&health_thread_cmd);
+
+       ret = ustctl_add_context(app->sock, &ua_ctx->ctx,
                        ua_chan->obj, &ua_ctx->obj);
        if (ret < 0) {
                goto error;
@@ -398,29 +540,36 @@ int create_ust_channel_context(struct ust_app_channel *ua_chan,
        DBG2("UST app context created successfully for channel %s", ua_chan->name);
 
 error:
+       health_code_update(&health_thread_cmd);
        return ret;
 }
 
 /*
- * Create the event context on the tracer.
+ * Set the filter 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 set_ust_event_filter(struct ust_app_event *ua_event,
+               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) {
+       health_code_update(&health_thread_cmd);
+
+       if (!ua_event->filter) {
+               ret = 0;
                goto error;
        }
 
-       ua_ctx->handle = ua_ctx->obj->handle;
+       ret = ustctl_set_filter(app->sock, ua_event->filter,
+                       ua_event->obj);
+       if (ret < 0) {
+               goto error;
+       }
 
-       DBG2("UST app context created successfully for event %s", ua_event->name);
+       DBG2("UST filter set successfully for event %s", ua_event->name);
 
 error:
+       health_code_update(&health_thread_cmd);
        return ret;
 }
 
@@ -432,18 +581,21 @@ static int disable_ust_event(struct ust_app *app,
 {
        int ret;
 
-       ret = ustctl_disable(app->key.sock, ua_event->obj);
+       health_code_update(&health_thread_cmd);
+
+       ret = ustctl_disable(app->sock, ua_event->obj);
        if (ret < 0) {
                ERR("UST app event %s disable failed for app (pid: %d) "
                                "and session handle %d with ret %d",
-                               ua_event->attr.name, app->key.pid, ua_sess->handle, ret);
+                               ua_event->attr.name, app->pid, ua_sess->handle, ret);
                goto error;
        }
 
        DBG2("UST app event %s disabled successfully for app (pid: %d)",
-                       ua_event->attr.name, app->key.pid);
+                       ua_event->attr.name, app->pid);
 
 error:
+       health_code_update(&health_thread_cmd);
        return ret;
 }
 
@@ -455,18 +607,21 @@ static int disable_ust_channel(struct ust_app *app,
 {
        int ret;
 
-       ret = ustctl_disable(app->key.sock, ua_chan->obj);
+       health_code_update(&health_thread_cmd);
+
+       ret = ustctl_disable(app->sock, ua_chan->obj);
        if (ret < 0) {
                ERR("UST app channel %s disable failed for app (pid: %d) "
                                "and session handle %d with ret %d",
-                               ua_chan->name, app->key.pid, ua_sess->handle, ret);
+                               ua_chan->name, app->pid, ua_sess->handle, ret);
                goto error;
        }
 
        DBG2("UST app channel %s disabled successfully for app (pid: %d)",
-                       ua_chan->name, app->key.pid);
+                       ua_chan->name, app->pid);
 
 error:
+       health_code_update(&health_thread_cmd);
        return ret;
 }
 
@@ -478,20 +633,23 @@ static int enable_ust_channel(struct ust_app *app,
 {
        int ret;
 
-       ret = ustctl_enable(app->key.sock, ua_chan->obj);
+       health_code_update(&health_thread_cmd);
+
+       ret = ustctl_enable(app->sock, ua_chan->obj);
        if (ret < 0) {
                ERR("UST app channel %s enable failed for app (pid: %d) "
                                "and session handle %d with ret %d",
-                               ua_chan->name, app->key.pid, ua_sess->handle, ret);
+                               ua_chan->name, app->pid, ua_sess->handle, ret);
                goto error;
        }
 
        ua_chan->enabled = 1;
 
        DBG2("UST app channel %s enabled successfully for app (pid: %d)",
-                       ua_chan->name, app->key.pid);
+                       ua_chan->name, app->pid);
 
 error:
+       health_code_update(&health_thread_cmd);
        return ret;
 }
 
@@ -503,18 +661,21 @@ static int enable_ust_event(struct ust_app *app,
 {
        int ret;
 
-       ret = ustctl_enable(app->key.sock, ua_event->obj);
+       health_code_update(&health_thread_cmd);
+
+       ret = ustctl_enable(app->sock, ua_event->obj);
        if (ret < 0) {
                ERR("UST app event %s enable failed for app (pid: %d) "
                                "and session handle %d with ret %d",
-                               ua_event->attr.name, app->key.pid, ua_sess->handle, ret);
+                               ua_event->attr.name, app->pid, ua_sess->handle, ret);
                goto error;
        }
 
        DBG2("UST app event %s enabled successfully for app (pid: %d)",
-                       ua_event->attr.name, app->key.pid);
+                       ua_event->attr.name, app->pid);
 
 error:
+       health_code_update(&health_thread_cmd);
        return ret;
 }
 
@@ -527,6 +688,8 @@ static int open_ust_metadata(struct ust_app *app,
        int ret;
        struct lttng_ust_channel_attr uattr;
 
+       health_code_update(&health_thread_cmd);
+
        uattr.overwrite = ua_sess->metadata->attr.overwrite;
        uattr.subbuf_size = ua_sess->metadata->attr.subbuf_size;
        uattr.num_subbuf = ua_sess->metadata->attr.num_subbuf;
@@ -536,18 +699,25 @@ static int open_ust_metadata(struct ust_app *app,
                ua_sess->metadata->attr.read_timer_interval;
        uattr.output = ua_sess->metadata->attr.output;
 
+       /* We are going to receive 2 fds, we need to reserve them. */
+       ret = lttng_fd_get(LTTNG_FD_APPS, 2);
+       if (ret < 0) {
+               ERR("Exhausted number of available FD upon metadata open");
+               goto error;
+       }
        /* UST tracer metadata creation */
-       ret = ustctl_open_metadata(app->key.sock, ua_sess->handle, &uattr,
+       ret = ustctl_open_metadata(app->sock, ua_sess->handle, &uattr,
                        &ua_sess->metadata->obj);
        if (ret < 0) {
                ERR("UST app open metadata failed for app pid:%d with ret %d",
-                               app->key.pid, ret);
+                               app->pid, ret);
                goto error;
        }
 
        ua_sess->metadata->handle = ua_sess->metadata->obj->handle;
 
 error:
+       health_code_update(&health_thread_cmd);
        return ret;
 }
 
@@ -559,7 +729,15 @@ static int create_ust_stream(struct ust_app *app,
 {
        int ret;
 
-       ret = ustctl_create_stream(app->key.sock, ua_sess->metadata->obj,
+       health_code_update(&health_thread_cmd);
+
+       /* We are going to receive 2 fds, we need to reserve them. */
+       ret = lttng_fd_get(LTTNG_FD_APPS, 2);
+       if (ret < 0) {
+               ERR("Exhausted number of available FD upon metadata stream create");
+               goto error;
+       }
+       ret = ustctl_create_stream(app->sock, ua_sess->metadata->obj,
                        &ua_sess->metadata->stream_obj);
        if (ret < 0) {
                ERR("UST create metadata stream failed");
@@ -567,6 +745,7 @@ static int create_ust_stream(struct ust_app *app,
        }
 
 error:
+       health_code_update(&health_thread_cmd);
        return ret;
 }
 
@@ -578,21 +757,36 @@ static int create_ust_channel(struct ust_app *app,
 {
        int ret;
 
+       health_code_update(&health_thread_cmd);
+
        /* TODO: remove cast and use lttng-ust-abi.h */
-       ret = ustctl_create_channel(app->key.sock, ua_sess->handle,
+
+       /* We are going to receive 2 fds, we need to reserve them. */
+       ret = lttng_fd_get(LTTNG_FD_APPS, 2);
+       if (ret < 0) {
+               ERR("Exhausted number of available FD upon create channel");
+               goto error;
+       }
+
+       health_code_update(&health_thread_cmd);
+
+       ret = ustctl_create_channel(app->sock, ua_sess->handle,
                        (struct lttng_ust_channel_attr *)&ua_chan->attr, &ua_chan->obj);
        if (ret < 0) {
                ERR("Creating channel %s for app (pid: %d, sock: %d) "
                                "and session handle %d with ret %d",
-                               ua_chan->name, app->key.pid, app->key.sock,
+                               ua_chan->name, app->pid, app->sock,
                                ua_sess->handle, ret);
+               lttng_fd_put(LTTNG_FD_APPS, 2);
                goto error;
        }
 
        ua_chan->handle = ua_chan->obj->handle;
 
        DBG2("UST app channel %s created successfully for pid:%d and sock:%d",
-                       ua_chan->name, app->key.pid, app->key.sock);
+                       ua_chan->name, app->pid, app->sock);
+
+       health_code_update(&health_thread_cmd);
 
        /* If channel is not enabled, disable it on the tracer */
        if (!ua_chan->enabled) {
@@ -603,6 +797,7 @@ static int create_ust_channel(struct ust_app *app,
        }
 
 error:
+       health_code_update(&health_thread_cmd);
        return ret;
 }
 
@@ -615,23 +810,31 @@ int create_ust_event(struct ust_app *app, struct ust_app_session *ua_sess,
 {
        int ret = 0;
 
+       health_code_update(&health_thread_cmd);
+
        /* Create UST event on tracer */
-       ret = ustctl_create_event(app->key.sock, &ua_event->attr, ua_chan->obj,
+       ret = ustctl_create_event(app->sock, &ua_event->attr, ua_chan->obj,
                        &ua_event->obj);
        if (ret < 0) {
-               if (ret == -EEXIST) {
-                       ret = 0;
-                       goto error;
-               }
                ERR("Error ustctl create event %s for app pid: %d with ret %d",
-                               ua_event->attr.name, app->key.pid, ret);
+                               ua_event->attr.name, app->pid, ret);
                goto error;
        }
 
        ua_event->handle = ua_event->obj->handle;
 
        DBG2("UST app event %s created successfully for pid:%d",
-                       ua_event->attr.name, app->key.pid);
+                       ua_event->attr.name, app->pid);
+
+       health_code_update(&health_thread_cmd);
+
+       /* Set filter if one is present. */
+       if (ua_event->filter) {
+               ret = set_ust_event_filter(ua_event, app);
+               if (ret < 0) {
+                       goto error;
+               }
+       }
 
        /* If event not enabled, disable it on the tracer */
        if (ua_event->enabled == 0) {
@@ -643,10 +846,10 @@ int create_ust_event(struct ust_app *app, struct ust_app_session *ua_sess,
                         * just created it.
                         */
                        switch (ret) {
-                       case -EPERM:
+                       case -LTTNG_UST_ERR_PERM:
                                /* Code flow problem */
                                assert(0);
-                       case -EEXIST:
+                       case -LTTNG_UST_ERR_EXIST:
                                /* It's OK for our use case. */
                                ret = 0;
                                break;
@@ -658,6 +861,7 @@ int create_ust_event(struct ust_app *app, struct ust_app_session *ua_sess,
        }
 
 error:
+       health_code_update(&health_thread_cmd);
        return ret;
 }
 
@@ -667,10 +871,6 @@ error:
 static void shadow_copy_event(struct ust_app_event *ua_event,
                struct ltt_ust_event *uevent)
 {
-       struct lttng_ht_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';
 
@@ -679,16 +879,10 @@ static void shadow_copy_event(struct ust_app_event *ua_event,
        /* Copy event attributes */
        memcpy(&ua_event->attr, &uevent->attr, sizeof(ua_event->attr));
 
-       cds_lfht_for_each_entry(uevent->ctx->ht, &iter.iter, uctx, node.node) {
-               ua_ctx = alloc_ust_app_ctx(&uctx->ctx);
-               if (ua_ctx == NULL) {
-                       /* malloc() failed. We should simply stop */
-                       return;
-               }
-
-               lttng_ht_node_init_ulong(&ua_ctx->node,
-                               (unsigned long) ua_ctx->ctx.ctx);
-               lttng_ht_add_unique_ulong(ua_event->ctx, &ua_ctx->node);
+       /* Copy filter bytecode */
+       if (uevent->filter) {
+               ua_event->filter = alloc_copy_ust_app_filter(uevent->filter);
+               /* Filter might be NULL here in case of ENONEM. */
        }
 }
 
@@ -699,7 +893,6 @@ static void shadow_copy_channel(struct ust_app_channel *ua_chan,
                struct ltt_ust_channel *uchan)
 {
        struct lttng_ht_iter iter;
-       struct lttng_ht_node_str *ua_event_node;
        struct ltt_ust_event *uevent;
        struct ltt_ust_context *uctx;
        struct ust_app_event *ua_event;
@@ -726,11 +919,9 @@ static void shadow_copy_channel(struct ust_app_channel *ua_chan,
 
        /* Copy all events from ltt ust channel to ust app channel */
        cds_lfht_for_each_entry(uchan->events->ht, &iter.iter, uevent, node.node) {
-               struct lttng_ht_iter uiter;
-
-               lttng_ht_lookup(ua_chan->events, (void *) uevent->attr.name, &uiter);
-               ua_event_node = lttng_ht_iter_get_node_str(&uiter);
-               if (ua_event_node == NULL) {
+               ua_event = find_ust_app_event(ua_chan->events, uevent->attr.name,
+                               uevent->filter, uevent->attr.loglevel);
+               if (ua_event == NULL) {
                        DBG2("UST event %s not found on shadow copy channel",
                                        uevent->attr.name);
                        ua_event = alloc_ust_app_event(uevent->attr.name, &uevent->attr);
@@ -738,7 +929,7 @@ static void shadow_copy_channel(struct ust_app_channel *ua_chan,
                                continue;
                        }
                        shadow_copy_event(ua_event, uevent);
-                       lttng_ht_add_unique_str(ua_chan->events, &ua_event->node);
+                       add_unique_ust_app_event(ua_chan->events, ua_event);
                }
        }
 
@@ -771,8 +962,8 @@ static void shadow_copy_session(struct ust_app_session *ua_sess,
        ua_sess->uid = usess->uid;
        ua_sess->gid = usess->gid;
 
-       ret = snprintf(ua_sess->path, PATH_MAX, "%s/%s-%d-%s", usess->pathname,
-                       app->name, app->key.pid, datetime);
+       ret = snprintf(ua_sess->path, PATH_MAX, "%s-%d-%s/", app->name, app->pid,
+                       datetime);
        if (ret < 0) {
                PERROR("asprintf UST shadow copy session");
                /* TODO: We cannot return an error from here.. */
@@ -851,10 +1042,12 @@ static struct ust_app_session *create_ust_app_session(
        int ret;
        struct ust_app_session *ua_sess;
 
+       health_code_update(&health_thread_cmd);
+
        ua_sess = lookup_session_by_app(usess, app);
        if (ua_sess == NULL) {
                DBG2("UST app pid: %d session id %d not found, creating it",
-                               app->key.pid, usess->id);
+                               app->pid, usess->id);
                ua_sess = alloc_ust_app_session();
                if (ua_sess == NULL) {
                        /* Only malloc can failed so something is really wrong */
@@ -863,13 +1056,16 @@ static struct ust_app_session *create_ust_app_session(
                shadow_copy_session(ua_sess, usess, app);
        }
 
+       health_code_update(&health_thread_cmd);
+
        if (ua_sess->handle == -1) {
-               ret = ustctl_create_session(app->key.sock);
+               ret = ustctl_create_session(app->sock);
                if (ret < 0) {
-                       ERR("Creating session for app pid %d", app->key.pid);
+                       ERR("Creating session for app pid %d", app->pid);
+                       delete_ust_app_session(-1, ua_sess);
                        /* This means that the tracer is gone... */
                        ua_sess = (void*) -1UL;
-                       goto error;
+                       goto end;
                }
 
                ua_sess->handle = ret;
@@ -882,11 +1078,8 @@ static struct ust_app_session *create_ust_app_session(
        }
 
 end:
+       health_code_update(&health_thread_cmd);
        return ua_sess;
-
-error:
-       delete_ust_app_session(-1, ua_sess);
-       return NULL;
 }
 
 /*
@@ -930,47 +1123,6 @@ 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 lttng_ht_iter iter;
-       struct lttng_ht_node_ulong *node;
-       struct ust_app_ctx *ua_ctx;
-
-       DBG2("UST app adding context to event %s", ua_event->name);
-
-       lttng_ht_lookup(ua_event->ctx, (void *)((unsigned long)uctx->ctx), &iter);
-       node = lttng_ht_iter_get_node_ulong(&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;
-       }
-
-       lttng_ht_node_init_ulong(&ua_ctx->node, (unsigned long) ua_ctx->ctx.ctx);
-       lttng_ht_add_unique_ulong(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.
  */
@@ -1090,14 +1242,14 @@ static struct ust_app_channel *create_ust_app_channel(
        ret = create_ust_channel(app, ua_sess, ua_chan);
        if (ret < 0) {
                /* Not found previously means that it does not exist on the tracer */
-               assert(ret != -EEXIST);
+               assert(ret != -LTTNG_UST_ERR_EXIST);
                goto error;
        }
 
        lttng_ht_add_unique_str(ua_sess->channels, &ua_chan->node);
 
        DBG2("UST app create channel %s for PID %d completed", ua_chan->name,
-                       app->key.pid);
+                       app->pid);
 
 end:
        return ua_chan;
@@ -1116,14 +1268,12 @@ int create_ust_app_event(struct ust_app_session *ua_sess,
                struct ust_app *app)
 {
        int ret = 0;
-       struct lttng_ht_iter iter;
-       struct lttng_ht_node_str *ua_event_node;
        struct ust_app_event *ua_event;
 
        /* Get event node */
-       lttng_ht_lookup(ua_chan->events, (void *)uevent->attr.name, &iter);
-       ua_event_node = lttng_ht_iter_get_node_str(&iter);
-       if (ua_event_node != NULL) {
+       ua_event = find_ust_app_event(ua_chan->events, uevent->attr.name,
+                       uevent->filter, uevent->attr.loglevel);
+       if (ua_event != NULL) {
                ret = -EEXIST;
                goto end;
        }
@@ -1141,14 +1291,14 @@ int create_ust_app_event(struct ust_app_session *ua_sess,
        ret = create_ust_event(app, ua_sess, ua_chan, ua_event);
        if (ret < 0) {
                /* Not found previously means that it does not exist on the tracer */
-               assert(ret != -EEXIST);
+               assert(ret != -LTTNG_UST_ERR_EXIST);
                goto error;
        }
 
-       lttng_ht_add_unique_str(ua_chan->events, &ua_event->node);
+       add_unique_ust_app_event(ua_chan->events, ua_event);
 
        DBG2("UST app create event %s for PID %d completed", ua_event->name,
-                       app->key.pid);
+                       app->pid);
 
 end:
        return ret;
@@ -1189,7 +1339,7 @@ static int create_ust_app_metadata(struct ust_app_session *ua_sess,
                        goto error;
                }
 
-               DBG2("UST metadata opened for app pid %d", app->key.pid);
+               DBG2("UST metadata opened for app pid %d", app->pid);
        }
 
        /* Open UST metadata stream */
@@ -1199,13 +1349,6 @@ static int create_ust_app_metadata(struct ust_app_session *ua_sess,
                        goto error;
                }
 
-               ret = run_as_mkdir(ua_sess->path, S_IRWXU | S_IRWXG,
-                               ua_sess->uid, ua_sess->gid);
-               if (ret < 0) {
-                       PERROR("mkdir UST metadata");
-                       goto error;
-               }
-
                ret = snprintf(ua_sess->metadata->pathname, PATH_MAX,
                                "%s/metadata", ua_sess->path);
                if (ret < 0) {
@@ -1214,7 +1357,7 @@ static int create_ust_app_metadata(struct ust_app_session *ua_sess,
                }
 
                DBG2("UST metadata stream object created for app pid %d",
-                               app->key.pid);
+                               app->pid);
        } else {
                ERR("Attempting to create stream without metadata opened");
                goto error;
@@ -1253,7 +1396,7 @@ struct ust_app *ust_app_find_by_pid(pid_t pid)
 
        DBG2("Found UST app by pid %d", pid);
 
-       return caa_container_of(node, struct ust_app, node);
+       return caa_container_of(node, struct ust_app, pid_n);
 
 error:
        rcu_read_unlock();
@@ -1272,8 +1415,10 @@ int ust_app_register(struct ust_register_msg *msg, int sock)
        struct ust_app *lta;
        int ret;
 
-       if ((msg->bits_per_long == 64 && ust_consumerd64_fd == -EINVAL)
-                       || (msg->bits_per_long == 32 && ust_consumerd32_fd == -EINVAL)) {
+       if ((msg->bits_per_long == 64 &&
+                               (uatomic_read(&ust_consumerd64_fd) == -EINVAL))
+                       || (msg->bits_per_long == 32 &&
+                               (uatomic_read(&ust_consumerd32_fd) == -EINVAL))) {
                ERR("Registration failed: application \"%s\" (pid: %d) has "
                        "%d-bit long, but no consumerd for this long size is available.\n",
                        msg->name, msg->pid, msg->bits_per_long);
@@ -1281,6 +1426,7 @@ int ust_app_register(struct ust_register_msg *msg, int sock)
                if (ret) {
                        PERROR("close");
                }
+               lttng_fd_put(LTTNG_FD_APPS, 1);
                return -EINVAL;
        }
        if (msg->major != LTTNG_UST_COMM_MAJOR) {
@@ -1291,6 +1437,7 @@ int ust_app_register(struct ust_register_msg *msg, int sock)
                if (ret) {
                        PERROR("close");
                }
+               lttng_fd_put(LTTNG_FD_APPS, 1);
                return -EINVAL;
        }
        lta = zmalloc(sizeof(struct ust_app));
@@ -1310,20 +1457,31 @@ int ust_app_register(struct ust_register_msg *msg, int sock)
        lta->name[16] = '\0';
        lta->sessions = lttng_ht_new(0, LTTNG_HT_TYPE_ULONG);
 
-       /* Set key map */
-       lta->key.pid = msg->pid;
-       lttng_ht_node_init_ulong(&lta->node, (unsigned long)lta->key.pid);
-       lta->key.sock = sock;
-       lttng_ht_node_init_ulong(&lta->key.node, (unsigned long)lta->key.sock);
+       lta->pid = msg->pid;
+       lttng_ht_node_init_ulong(&lta->pid_n, (unsigned long)lta->pid);
+       lta->sock = sock;
+       lttng_ht_node_init_ulong(&lta->sock_n, (unsigned long)lta->sock);
 
        rcu_read_lock();
-       lttng_ht_add_unique_ulong(ust_app_sock_key_map, &lta->key.node);
-       lttng_ht_add_unique_ulong(ust_app_ht, &lta->node);
+
+       /*
+        * On a re-registration, we want to kick out the previous registration of
+        * that pid
+        */
+       lttng_ht_add_replace_ulong(ust_app_ht, &lta->pid_n);
+
+       /*
+        * The socket _should_ be unique until _we_ call close. So, a add_unique
+        * for the ust_app_ht_by_sock is used which asserts fail if the entry was
+        * already in the table.
+        */
+       lttng_ht_add_unique_ulong(ust_app_ht_by_sock, &lta->sock_n);
+
        rcu_read_unlock();
 
        DBG("App registered with pid:%d ppid:%d uid:%d gid:%d sock:%d name:%s"
-                       " (version %d.%d)", lta->key.pid, lta->ppid, lta->uid, lta->gid,
-                       lta->key.sock, lta->name, lta->v_major, lta->v_minor);
+                       " (version %d.%d)", lta->pid, lta->ppid, lta->uid, lta->gid,
+                       lta->sock, lta->name, lta->v_major, lta->v_minor);
 
        return 0;
 }
@@ -1342,31 +1500,40 @@ void ust_app_unregister(int sock)
        int ret;
 
        rcu_read_lock();
-       lta = find_app_by_sock(sock);
-       if (lta == NULL) {
-               ERR("Unregister app sock %d not found!", sock);
-               goto error;
-       }
-
-       DBG("PID %d unregistering with sock %d", lta->key.pid, sock);
-
-       /* Remove application from socket hash table */
-       lttng_ht_lookup(ust_app_sock_key_map, (void *)((unsigned long) sock), &iter);
-       ret = lttng_ht_del(ust_app_sock_key_map, &iter);
-       assert(!ret);
 
        /* Get the node reference for a call_rcu */
-       lttng_ht_lookup(ust_app_ht, (void *)((unsigned long) lta->key.pid), &iter);
+       lttng_ht_lookup(ust_app_ht_by_sock, (void *)((unsigned long) sock), &iter);
        node = lttng_ht_iter_get_node_ulong(&iter);
        if (node == NULL) {
-               ERR("Unable to find app sock %d by pid %d", sock, lta->key.pid);
+               ERR("Unable to find app by sock %d", sock);
                goto error;
        }
 
+       lta = caa_container_of(node, struct ust_app, sock_n);
+
+       DBG("PID %d unregistering with sock %d", lta->pid, sock);
+
        /* Remove application from PID hash table */
-       ret = lttng_ht_del(ust_app_ht, &iter);
+       ret = lttng_ht_del(ust_app_ht_by_sock, &iter);
        assert(!ret);
-       call_rcu(&node->head, delete_ust_app_rcu);
+
+       /* Assign second node for deletion */
+       iter.iter.node = &lta->pid_n.node;
+
+       /*
+        * Ignore return value since the node might have been removed before by an
+        * add replace during app registration because the PID can be reassigned by
+        * the OS.
+        */
+       ret = lttng_ht_del(ust_app_ht, &iter);
+       if (ret) {
+               DBG3("Unregister app by PID %d failed. This can happen on pid reuse",
+                               lta->pid);
+       }
+
+       /* Free memory */
+       call_rcu(&lta->pid_n.head, delete_ust_app_rcu);
+
 error:
        rcu_read_unlock();
        return;
@@ -1407,9 +1574,11 @@ int ust_app_list_events(struct lttng_event **events)
 
        rcu_read_lock();
 
-       cds_lfht_for_each_entry(ust_app_ht->ht, &iter.iter, app, node.node) {
+       cds_lfht_for_each_entry(ust_app_ht->ht, &iter.iter, app, pid_n.node) {
                struct lttng_ust_tracepoint_iter uiter;
 
+               health_code_update(&health_thread_cmd);
+
                if (!app->compatible) {
                        /*
                         * TODO: In time, we should notice the caller of this error by
@@ -1417,30 +1586,34 @@ int ust_app_list_events(struct lttng_event **events)
                         */
                        continue;
                }
-               handle = ustctl_tracepoint_list(app->key.sock);
+               handle = ustctl_tracepoint_list(app->sock);
                if (handle < 0) {
                        ERR("UST app list events getting handle failed for app pid %d",
-                                       app->key.pid);
+                                       app->pid);
                        continue;
                }
 
-               while ((ret = ustctl_tracepoint_list_get(app->key.sock, handle,
-                                               &uiter)) != -ENOENT) {
+               while ((ret = ustctl_tracepoint_list_get(app->sock, handle,
+                                       &uiter)) != -LTTNG_UST_ERR_NOENT) {
+                       health_code_update(&health_thread_cmd);
                        if (count >= nbmem) {
+                               /* In case the realloc fails, we free the memory */
+                               void *tmp_ptr = (void *) tmp;
                                DBG2("Reallocating event list from %zu to %zu entries", nbmem,
                                                2 * nbmem);
                                nbmem *= 2;
                                tmp = realloc(tmp, nbmem * sizeof(struct lttng_event));
                                if (tmp == NULL) {
                                        PERROR("realloc ust app events");
+                                       free(tmp_ptr);
                                        ret = -ENOMEM;
                                        goto rcu_error;
                                }
                        }
                        memcpy(tmp[count].name, uiter.name, LTTNG_UST_SYM_NAME_LEN);
                        tmp[count].loglevel = uiter.loglevel;
-                       tmp[count].type = LTTNG_UST_TRACEPOINT;
-                       tmp[count].pid = app->key.pid;
+                       tmp[count].type = (enum lttng_event_type) LTTNG_UST_TRACEPOINT;
+                       tmp[count].pid = app->pid;
                        tmp[count].enabled = -1;
                        count++;
                }
@@ -1454,6 +1627,90 @@ int ust_app_list_events(struct lttng_event **events)
 rcu_error:
        rcu_read_unlock();
 error:
+       health_code_update(&health_thread_cmd);
+       return ret;
+}
+
+/*
+ * Fill events array with all events name of all registered apps.
+ */
+int ust_app_list_event_fields(struct lttng_event_field **fields)
+{
+       int ret, handle;
+       size_t nbmem, count = 0;
+       struct lttng_ht_iter iter;
+       struct ust_app *app;
+       struct lttng_event_field *tmp;
+
+       nbmem = UST_APP_EVENT_LIST_SIZE;
+       tmp = zmalloc(nbmem * sizeof(struct lttng_event_field));
+       if (tmp == NULL) {
+               PERROR("zmalloc ust app event fields");
+               ret = -ENOMEM;
+               goto error;
+       }
+
+       rcu_read_lock();
+
+       cds_lfht_for_each_entry(ust_app_ht->ht, &iter.iter, app, pid_n.node) {
+               struct lttng_ust_field_iter uiter;
+
+               health_code_update(&health_thread_cmd);
+
+               if (!app->compatible) {
+                       /*
+                        * TODO: In time, we should notice the caller of this error by
+                        * telling him that this is a version error.
+                        */
+                       continue;
+               }
+               handle = ustctl_tracepoint_field_list(app->sock);
+               if (handle < 0) {
+                       ERR("UST app list event fields getting handle failed for app pid %d",
+                                       app->pid);
+                       continue;
+               }
+
+               while ((ret = ustctl_tracepoint_field_list_get(app->sock, handle,
+                                       &uiter)) != -LTTNG_UST_ERR_NOENT) {
+                       health_code_update(&health_thread_cmd);
+                       if (count >= nbmem) {
+                               /* In case the realloc fails, we free the memory */
+                               void *tmp_ptr = (void *) tmp;
+                               DBG2("Reallocating event field list from %zu to %zu entries", nbmem,
+                                               2 * nbmem);
+                               nbmem *= 2;
+                               tmp = realloc(tmp, nbmem * sizeof(struct lttng_event_field));
+                               if (tmp == NULL) {
+                                       PERROR("realloc ust app event fields");
+                                       free(tmp_ptr);
+                                       ret = -ENOMEM;
+                                       goto rcu_error;
+                               }
+                       }
+
+                       memcpy(tmp[count].field_name, uiter.field_name, LTTNG_UST_SYM_NAME_LEN);
+                       tmp[count].type = uiter.type;
+                       tmp[count].nowrite = uiter.nowrite;
+
+                       memcpy(tmp[count].event.name, uiter.event_name, LTTNG_UST_SYM_NAME_LEN);
+                       tmp[count].event.loglevel = uiter.loglevel;
+                       tmp[count].event.type = LTTNG_UST_TRACEPOINT;
+                       tmp[count].event.pid = app->pid;
+                       tmp[count].event.enabled = -1;
+                       count++;
+               }
+       }
+
+       ret = count;
+       *fields = tmp;
+
+       DBG2("UST app list event fields done (%zu events)", count);
+
+rcu_error:
+       rcu_read_unlock();
+error:
+       health_code_update(&health_thread_cmd);
        return ret;
 }
 
@@ -1463,27 +1720,29 @@ error:
 void ust_app_clean_list(void)
 {
        int ret;
+       struct ust_app *app;
        struct lttng_ht_iter iter;
-       struct lttng_ht_node_ulong *node;
 
        DBG2("UST app cleaning registered apps hash table");
 
        rcu_read_lock();
 
-       cds_lfht_for_each_entry(ust_app_ht->ht, &iter.iter, node, node) {
+       cds_lfht_for_each_entry(ust_app_ht->ht, &iter.iter, app, pid_n.node) {
                ret = lttng_ht_del(ust_app_ht, &iter);
                assert(!ret);
-               call_rcu(&node->head, delete_ust_app_rcu);
+               call_rcu(&app->pid_n.head, delete_ust_app_rcu);
        }
-       /* Destroy is done only when the ht is empty */
-       lttng_ht_destroy(ust_app_ht);
 
-       cds_lfht_for_each_entry(ust_app_sock_key_map->ht, &iter.iter, node, node) {
-               ret = lttng_ht_del(ust_app_sock_key_map, &iter);
+       /* Cleanup socket hash table */
+       cds_lfht_for_each_entry(ust_app_ht_by_sock->ht, &iter.iter, app,
+                       sock_n.node) {
+               ret = lttng_ht_del(ust_app_ht_by_sock, &iter);
                assert(!ret);
        }
+
        /* Destroy is done only when the ht is empty */
-       lttng_ht_destroy(ust_app_sock_key_map);
+       lttng_ht_destroy(ust_app_ht);
+       lttng_ht_destroy(ust_app_ht_by_sock);
 
        rcu_read_unlock();
 }
@@ -1494,7 +1753,7 @@ void ust_app_clean_list(void)
 void ust_app_ht_alloc(void)
 {
        ust_app_ht = lttng_ht_new(0, LTTNG_HT_TYPE_ULONG);
-       ust_app_sock_key_map = lttng_ht_new(0, LTTNG_HT_TYPE_ULONG);
+       ust_app_ht_by_sock = lttng_ht_new(0, LTTNG_HT_TYPE_ULONG);
 }
 
 /*
@@ -1522,7 +1781,7 @@ int ust_app_disable_channel_glb(struct ltt_ust_session *usess,
        rcu_read_lock();
 
        /* For every registered applications */
-       cds_lfht_for_each_entry(ust_app_ht->ht, &iter.iter, app, node.node) {
+       cds_lfht_for_each_entry(ust_app_ht->ht, &iter.iter, app, pid_n.node) {
                struct lttng_ht_iter uiter;
                if (!app->compatible) {
                        /*
@@ -1583,7 +1842,7 @@ int ust_app_enable_channel_glb(struct ltt_ust_session *usess,
        rcu_read_lock();
 
        /* For every registered applications */
-       cds_lfht_for_each_entry(ust_app_ht->ht, &iter.iter, app, node.node) {
+       cds_lfht_for_each_entry(ust_app_ht->ht, &iter.iter, app, pid_n.node) {
                if (!app->compatible) {
                        /*
                         * TODO: In time, we should notice the caller of this error by
@@ -1630,7 +1889,7 @@ int ust_app_disable_event_glb(struct ltt_ust_session *usess,
        rcu_read_lock();
 
        /* For all registered applications */
-       cds_lfht_for_each_entry(ust_app_ht->ht, &iter.iter, app, node.node) {
+       cds_lfht_for_each_entry(ust_app_ht->ht, &iter.iter, app, pid_n.node) {
                if (!app->compatible) {
                        /*
                         * TODO: In time, we should notice the caller of this error by
@@ -1649,7 +1908,7 @@ int ust_app_disable_event_glb(struct ltt_ust_session *usess,
                ua_chan_node = lttng_ht_iter_get_node_str(&uiter);
                if (ua_chan_node == NULL) {
                        DBG2("Channel %s not found in session id %d for app pid %d."
-                                       "Skipping", uchan->name, usess->id, app->key.pid);
+                                       "Skipping", uchan->name, usess->id, app->pid);
                        continue;
                }
                ua_chan = caa_container_of(ua_chan_node, struct ust_app_channel, node);
@@ -1658,7 +1917,7 @@ int ust_app_disable_event_glb(struct ltt_ust_session *usess,
                ua_event_node = lttng_ht_iter_get_node_str(&uiter);
                if (ua_event_node == NULL) {
                        DBG2("Event %s not found in channel %s for app pid %d."
-                                       "Skipping", uevent->attr.name, uchan->name, app->key.pid);
+                                       "Skipping", uevent->attr.name, uchan->name, app->pid);
                        continue;
                }
                ua_event = caa_container_of(ua_event_node, struct ust_app_event, node);
@@ -1696,7 +1955,7 @@ int ust_app_disable_all_event_glb(struct ltt_ust_session *usess,
        rcu_read_lock();
 
        /* For all registered applications */
-       cds_lfht_for_each_entry(ust_app_ht->ht, &iter.iter, app, node.node) {
+       cds_lfht_for_each_entry(ust_app_ht->ht, &iter.iter, app, pid_n.node) {
                if (!app->compatible) {
                        /*
                         * TODO: In time, we should notice the caller of this error by
@@ -1738,6 +1997,7 @@ int ust_app_disable_all_event_glb(struct ltt_ust_session *usess,
 int ust_app_create_channel_glb(struct ltt_ust_session *usess,
                struct ltt_ust_channel *uchan)
 {
+       int ret = 0;
        struct lttng_ht_iter iter;
        struct ust_app *app;
        struct ust_app_session *ua_sess;
@@ -1753,7 +2013,7 @@ int ust_app_create_channel_glb(struct ltt_ust_session *usess,
        rcu_read_lock();
 
        /* For every registered applications */
-       cds_lfht_for_each_entry(ust_app_ht->ht, &iter.iter, app, node.node) {
+       cds_lfht_for_each_entry(ust_app_ht->ht, &iter.iter, app, pid_n.node) {
                if (!app->compatible) {
                        /*
                         * TODO: In time, we should notice the caller of this error by
@@ -1769,9 +2029,11 @@ int ust_app_create_channel_glb(struct ltt_ust_session *usess,
                ua_sess = create_ust_app_session(usess, app);
                if (ua_sess == NULL) {
                        /* The malloc() failed. */
+                       ret = -1;
                        goto error;
                } else if (ua_sess == (void *) -1UL) {
                        /* The application's socket is not valid. Contiuing */
+                       ret = -1;
                        continue;
                }
 
@@ -1779,16 +2041,15 @@ int ust_app_create_channel_glb(struct ltt_ust_session *usess,
                ua_chan = create_ust_app_channel(ua_sess, uchan, app);
                if (ua_chan == NULL) {
                        /* Major problem here and it's maybe the tracer or malloc() */
+                       ret = -1;
                        goto error;
                }
        }
 
        rcu_read_unlock();
 
-       return 0;
-
 error:
-       return -1;
+       return ret;
 }
 
 /*
@@ -1799,7 +2060,7 @@ int ust_app_enable_event_glb(struct ltt_ust_session *usess,
 {
        int ret = 0;
        struct lttng_ht_iter iter, uiter;
-       struct lttng_ht_node_str *ua_chan_node, *ua_event_node;
+       struct lttng_ht_node_str *ua_chan_node;
        struct ust_app *app;
        struct ust_app_session *ua_sess;
        struct ust_app_channel *ua_chan;
@@ -1817,7 +2078,7 @@ int ust_app_enable_event_glb(struct ltt_ust_session *usess,
        rcu_read_lock();
 
        /* For all registered applications */
-       cds_lfht_for_each_entry(ust_app_ht->ht, &iter.iter, app, node.node) {
+       cds_lfht_for_each_entry(ust_app_ht->ht, &iter.iter, app, pid_n.node) {
                if (!app->compatible) {
                        /*
                         * TODO: In time, we should notice the caller of this error by
@@ -1837,14 +2098,14 @@ int ust_app_enable_event_glb(struct ltt_ust_session *usess,
 
                ua_chan = caa_container_of(ua_chan_node, struct ust_app_channel, node);
 
-               lttng_ht_lookup(ua_chan->events, (void*)uevent->attr.name, &uiter);
-               ua_event_node = lttng_ht_iter_get_node_str(&uiter);
-               if (ua_event_node == NULL) {
+               /* Get event node */
+               ua_event = find_ust_app_event(ua_chan->events, uevent->attr.name,
+                               uevent->filter, uevent->attr.loglevel);
+               if (ua_event == NULL) {
                        DBG3("UST app enable event %s not found for app PID %d."
-                                       "Skipping app", uevent->attr.name, app->key.pid);
+                                       "Skipping app", uevent->attr.name, app->pid);
                        continue;
                }
-               ua_event = caa_container_of(ua_event_node, struct ust_app_event, node);
 
                ret = enable_ust_app_event(ua_sess, ua_event, app);
                if (ret < 0) {
@@ -1877,7 +2138,7 @@ int ust_app_create_event_glb(struct ltt_ust_session *usess,
        rcu_read_lock();
 
        /* For all registered applications */
-       cds_lfht_for_each_entry(ust_app_ht->ht, &iter.iter, app, node.node) {
+       cds_lfht_for_each_entry(ust_app_ht->ht, &iter.iter, app, pid_n.node) {
                if (!app->compatible) {
                        /*
                         * TODO: In time, we should notice the caller of this error by
@@ -1899,12 +2160,12 @@ int ust_app_create_event_glb(struct ltt_ust_session *usess,
 
                ret = create_ust_app_event(ua_sess, ua_chan, uevent, app);
                if (ret < 0) {
-                       if (ret != -EEXIST) {
+                       if (ret != -LTTNG_UST_ERR_EXIST) {
                                /* Possible value at this point: -ENOMEM. If so, we stop! */
                                break;
                        }
                        DBG2("UST app event %s already exist on app PID %d",
-                                       uevent->attr.name, app->key.pid);
+                                       uevent->attr.name, app->pid);
                        continue;
                }
        }
@@ -1924,9 +2185,9 @@ int ust_app_start_trace(struct ltt_ust_session *usess, struct ust_app *app)
        struct ust_app_session *ua_sess;
        struct ust_app_channel *ua_chan;
        struct ltt_ust_stream *ustream;
-       int consumerd_fd;
+       struct consumer_socket *socket;
 
-       DBG("Starting tracing for ust app pid %d", app->key.pid);
+       DBG("Starting tracing for ust app pid %d", app->pid);
 
        rcu_read_lock();
 
@@ -1944,11 +2205,26 @@ int ust_app_start_trace(struct ltt_ust_session *usess, struct ust_app *app)
                goto skip_setup;
        }
 
+       /* Create directories if consumer is LOCAL and has a path defined. */
+       if (usess->consumer->type == CONSUMER_DST_LOCAL &&
+                       strlen(usess->consumer->dst.trace_path) > 0) {
+               ret = run_as_mkdir_recursive(usess->consumer->dst.trace_path,
+                               S_IRWXU | S_IRWXG, usess->uid, usess->gid);
+               if (ret < 0) {
+                       if (ret != -EEXIST) {
+                               ERR("Trace directory creation error");
+                               ret = -1;
+                               goto error_rcu_unlock;
+                       }
+               }
+       }
+
        /* Indicate that the session has been started once */
        ua_sess->started = 1;
 
        ret = create_ust_app_metadata(ua_sess, usess->pathname, app);
        if (ret < 0) {
+               ret = LTTNG_ERR_UST_META_FAIL;
                goto error_rcu_unlock;
        }
 
@@ -1964,34 +2240,63 @@ int ust_app_start_trace(struct ltt_ust_session *usess, struct ust_app *app)
                                goto error_rcu_unlock;
                        }
 
-                       ret = ustctl_create_stream(app->key.sock, ua_chan->obj,
+                       /* We are going to receive 2 fds, we need to reserve them. */
+                       ret = lttng_fd_get(LTTNG_FD_APPS, 2);
+                       if (ret < 0) {
+                               ERR("Exhausted number of available FD upon stream create");
+                               free(ustream);
+                               goto error_rcu_unlock;
+                       }
+
+                       health_code_update(&health_thread_cmd);
+
+                       ret = ustctl_create_stream(app->sock, ua_chan->obj,
                                        &ustream->obj);
                        if (ret < 0) {
                                /* Got all streams */
+                               lttng_fd_put(LTTNG_FD_APPS, 2);
+                               free(ustream);
+                               ret = LTTNG_ERR_UST_STREAM_FAIL;
                                break;
                        }
                        ustream->handle = ustream->obj->handle;
 
+                       health_code_update(&health_thread_cmd);
+
                        /* Order is important */
                        cds_list_add_tail(&ustream->list, &ua_chan->streams.head);
-                       ret = snprintf(ustream->pathname, PATH_MAX, "%s/%s_%u",
-                                       ua_sess->path, ua_chan->name,
-                                       ua_chan->streams.count++);
+                       ret = snprintf(ustream->name, sizeof(ustream->name), "%s_%u",
+                                       ua_chan->name, ua_chan->streams.count);
+                       ua_chan->streams.count++;
                        if (ret < 0) {
                                PERROR("asprintf UST create stream");
+                               /*
+                                * XXX what should we do here with the
+                                * stream ?
+                                */
                                continue;
                        }
-                       DBG2("UST stream %d ready at %s", ua_chan->streams.count,
-                                       ustream->pathname);
+                       DBG2("UST stream %d ready (handle: %d)", ua_chan->streams.count,
+                                       ustream->handle);
                }
+
+               health_code_update(&health_thread_cmd);
        }
 
        switch (app->bits_per_long) {
        case 64:
-               consumerd_fd = ust_consumerd64_fd;
+               socket = consumer_find_socket(uatomic_read(&ust_consumerd64_fd),
+                               usess->consumer);
+               if (socket == NULL) {
+                       goto skip_setup;
+               }
                break;
        case 32:
-               consumerd_fd = ust_consumerd32_fd;
+               socket = consumer_find_socket(uatomic_read(&ust_consumerd32_fd),
+                               usess->consumer);
+               if (socket == NULL) {
+                       goto skip_setup;
+               }
                break;
        default:
                ret = -EINVAL;
@@ -1999,28 +2304,34 @@ int ust_app_start_trace(struct ltt_ust_session *usess, struct ust_app *app)
        }
 
        /* Setup UST consumer socket and send fds to it */
-       ret = ust_consumer_send_session(consumerd_fd, ua_sess);
+       ret = ust_consumer_send_session(ua_sess, usess->consumer, socket);
        if (ret < 0) {
                goto error_rcu_unlock;
        }
 
+       health_code_update(&health_thread_cmd);
+
 skip_setup:
        /* This start the UST tracing */
-       ret = ustctl_start_session(app->key.sock, ua_sess->handle);
+       ret = ustctl_start_session(app->sock, ua_sess->handle);
        if (ret < 0) {
-               ERR("Error starting tracing for app pid: %d", app->key.pid);
+               ERR("Error starting tracing for app pid: %d", app->pid);
                goto error_rcu_unlock;
        }
 
+       health_code_update(&health_thread_cmd);
+
        /* Quiescent wait after starting trace */
-       ustctl_wait_quiescent(app->key.sock);
+       ustctl_wait_quiescent(app->sock);
 
 end:
        rcu_read_unlock();
+       health_code_update(&health_thread_cmd);
        return 0;
 
 error_rcu_unlock:
        rcu_read_unlock();
+       health_code_update(&health_thread_cmd);
        return -1;
 }
 
@@ -2034,7 +2345,7 @@ int ust_app_stop_trace(struct ltt_ust_session *usess, struct ust_app *app)
        struct ust_app_session *ua_sess;
        struct ust_app_channel *ua_chan;
 
-       DBG("Stopping tracing for ust app pid %d", app->key.pid);
+       DBG("Stopping tracing for ust app pid %d", app->pid);
 
        rcu_read_lock();
 
@@ -2055,41 +2366,52 @@ int ust_app_stop_trace(struct ltt_ust_session *usess, struct ust_app *app)
         */
        assert(ua_sess->started == 1);
 
+       health_code_update(&health_thread_cmd);
+
        /* This inhibits UST tracing */
-       ret = ustctl_stop_session(app->key.sock, ua_sess->handle);
+       ret = ustctl_stop_session(app->sock, ua_sess->handle);
        if (ret < 0) {
-               ERR("Error stopping tracing for app pid: %d", app->key.pid);
+               ERR("Error stopping tracing for app pid: %d", app->pid);
                goto error_rcu_unlock;
        }
 
+       health_code_update(&health_thread_cmd);
+
        /* Quiescent wait after stopping trace */
-       ustctl_wait_quiescent(app->key.sock);
+       ustctl_wait_quiescent(app->sock);
+
+       health_code_update(&health_thread_cmd);
 
        /* Flushing buffers */
        cds_lfht_for_each_entry(ua_sess->channels->ht, &iter.iter, ua_chan,
                        node.node) {
-               ret = ustctl_sock_flush_buffer(app->key.sock, ua_chan->obj);
+               health_code_update(&health_thread_cmd);
+               ret = ustctl_sock_flush_buffer(app->sock, ua_chan->obj);
                if (ret < 0) {
                        ERR("UST app PID %d channel %s flush failed with ret %d",
-                                       app->key.pid, ua_chan->name, ret);
+                                       app->pid, ua_chan->name, ret);
                        /* Continuing flushing all buffers */
                        continue;
                }
        }
 
+       health_code_update(&health_thread_cmd);
+
        /* Flush all buffers before stopping */
-       ret = ustctl_sock_flush_buffer(app->key.sock, ua_sess->metadata->obj);
+       ret = ustctl_sock_flush_buffer(app->sock, ua_sess->metadata->obj);
        if (ret < 0) {
-               ERR("UST app PID %d metadata flush failed with ret %d", app->key.pid,
+               ERR("UST app PID %d metadata flush failed with ret %d", app->pid,
                                ret);
        }
 
 end:
        rcu_read_unlock();
+       health_code_update(&health_thread_cmd);
        return 0;
 
 error_rcu_unlock:
        rcu_read_unlock();
+       health_code_update(&health_thread_cmd);
        return -1;
 }
 
@@ -2104,7 +2426,7 @@ int ust_app_destroy_trace(struct ltt_ust_session *usess, struct ust_app *app)
        struct lttng_ht_node_ulong *node;
        int ret;
 
-       DBG("Destroy tracing for ust app pid %d", app->key.pid);
+       DBG("Destroy tracing for ust app pid %d", app->pid);
 
        rcu_read_lock();
 
@@ -2125,19 +2447,23 @@ int ust_app_destroy_trace(struct ltt_ust_session *usess, struct ust_app *app)
        obj.shm_fd = -1;
        obj.wait_fd = -1;
        obj.memory_map_size = 0;
-       ustctl_release_object(app->key.sock, &obj);
+       health_code_update(&health_thread_cmd);
+       ustctl_release_object(app->sock, &obj);
 
-       delete_ust_app_session(app->key.sock, ua_sess);
+       health_code_update(&health_thread_cmd);
+       delete_ust_app_session(app->sock, ua_sess);
 
        /* Quiescent wait after stopping trace */
-       ustctl_wait_quiescent(app->key.sock);
+       ustctl_wait_quiescent(app->sock);
 
 end:
        rcu_read_unlock();
+       health_code_update(&health_thread_cmd);
        return 0;
 
 error_rcu_unlock:
        rcu_read_unlock();
+       health_code_update(&health_thread_cmd);
        return -1;
 }
 
@@ -2154,7 +2480,7 @@ int ust_app_start_trace_all(struct ltt_ust_session *usess)
 
        rcu_read_lock();
 
-       cds_lfht_for_each_entry(ust_app_ht->ht, &iter.iter, app, node.node) {
+       cds_lfht_for_each_entry(ust_app_ht->ht, &iter.iter, app, pid_n.node) {
                ret = ust_app_start_trace(usess, app);
                if (ret < 0) {
                        /* Continue to next apps even on error */
@@ -2180,7 +2506,7 @@ int ust_app_stop_trace_all(struct ltt_ust_session *usess)
 
        rcu_read_lock();
 
-       cds_lfht_for_each_entry(ust_app_ht->ht, &iter.iter, app, node.node) {
+       cds_lfht_for_each_entry(ust_app_ht->ht, &iter.iter, app, pid_n.node) {
                ret = ust_app_stop_trace(usess, app);
                if (ret < 0) {
                        /* Continue to next apps even on error */
@@ -2206,7 +2532,7 @@ int ust_app_destroy_trace_all(struct ltt_ust_session *usess)
 
        rcu_read_lock();
 
-       cds_lfht_for_each_entry(ust_app_ht->ht, &iter.iter, app, node.node) {
+       cds_lfht_for_each_entry(ust_app_ht->ht, &iter.iter, app, pid_n.node) {
                ret = ust_app_destroy_trace(usess, app);
                if (ret < 0) {
                        /* Continue to next apps even on error */
@@ -2253,7 +2579,8 @@ void ust_app_global_update(struct ltt_ust_session *usess, int sock)
        }
 
        ua_sess = create_ust_app_session(usess, app);
-       if (ua_sess == NULL) {
+       if (ua_sess == NULL || ua_sess == (void *) -1UL) {
+               /* Tracer is gone for this session and has been freed */
                goto error;
        }
 
@@ -2289,14 +2616,10 @@ void ust_app_global_update(struct ltt_ust_session *usess, int sock)
                                continue;
                        }
 
-                       /* Add context on events. */
-                       cds_lfht_for_each_entry(ua_event->ctx->ht, &iter_ctx.iter,
-                                       ua_ctx, node.node) {
-                               ret = create_ust_event_context(ua_event, ua_ctx, app);
-                               if (ret < 0) {
-                                       /* FIXME: Should we quit here or continue... */
-                                       continue;
-                               }
+                       ret = set_ust_event_filter(ua_event, app);
+                       if (ret < 0) {
+                               /* FIXME: Should we quit here or continue... */
+                               continue;
                        }
                }
        }
@@ -2307,7 +2630,7 @@ void ust_app_global_update(struct ltt_ust_session *usess, int sock)
                        goto error;
                }
 
-               DBG2("UST trace started for app pid %d", app->key.pid);
+               DBG2("UST trace started for app pid %d", app->pid);
        }
 
 error:
@@ -2330,7 +2653,7 @@ int ust_app_add_ctx_channel_glb(struct ltt_ust_session *usess,
 
        rcu_read_lock();
 
-       cds_lfht_for_each_entry(ust_app_ht->ht, &iter.iter, app, node.node) {
+       cds_lfht_for_each_entry(ust_app_ht->ht, &iter.iter, app, pid_n.node) {
                if (!app->compatible) {
                        /*
                         * TODO: In time, we should notice the caller of this error by
@@ -2362,63 +2685,6 @@ int ust_app_add_ctx_channel_glb(struct ltt_ust_session *usess,
        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 lttng_ht_node_str *ua_chan_node, *ua_event_node;
-       struct lttng_ht_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->ht, &iter.iter, app, node.node) {
-               if (!app->compatible) {
-                       /*
-                        * TODO: In time, we should notice the caller of this error by
-                        * telling him that this is a version error.
-                        */
-                       continue;
-               }
-               ua_sess = lookup_session_by_app(usess, app);
-               if (ua_sess == NULL) {
-                       continue;
-               }
-
-               /* Lookup channel in the ust app session */
-               lttng_ht_lookup(ua_sess->channels, (void *)uchan->name, &uiter);
-               ua_chan_node = lttng_ht_iter_get_node_str(&uiter);
-               if (ua_chan_node == NULL) {
-                       continue;
-               }
-               ua_chan = caa_container_of(ua_chan_node, struct ust_app_channel,
-                               node);
-
-               lttng_ht_lookup(ua_chan->events, (void *)uevent->attr.name, &uiter);
-               ua_event_node = lttng_ht_iter_get_node_str(&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;
-               }
-       }
-
-       rcu_read_unlock();
-       return ret;
-}
-
 /*
  * Enable event for a channel from a UST session for a specific PID.
  */
@@ -2427,7 +2693,7 @@ int ust_app_enable_event_pid(struct ltt_ust_session *usess,
 {
        int ret = 0;
        struct lttng_ht_iter iter;
-       struct lttng_ht_node_str *ua_chan_node, *ua_event_node;
+       struct lttng_ht_node_str *ua_chan_node;
        struct ust_app *app;
        struct ust_app_session *ua_sess;
        struct ust_app_channel *ua_chan;
@@ -2461,16 +2727,14 @@ int ust_app_enable_event_pid(struct ltt_ust_session *usess,
 
        ua_chan = caa_container_of(ua_chan_node, struct ust_app_channel, node);
 
-       lttng_ht_lookup(ua_chan->events, (void *)uevent->attr.name, &iter);
-       ua_event_node = lttng_ht_iter_get_node_str(&iter);
-       if (ua_event_node == NULL) {
+       ua_event = find_ust_app_event(ua_chan->events, uevent->attr.name,
+                       uevent->filter, uevent->attr.loglevel);
+       if (ua_event == NULL) {
                ret = create_ust_app_event(ua_sess, ua_chan, uevent, app);
                if (ret < 0) {
                        goto error;
                }
        } else {
-               ua_event = caa_container_of(ua_event_node, struct ust_app_event, node);
-
                ret = enable_ust_app_event(ua_sess, ua_event, app);
                if (ret < 0) {
                        goto error;
@@ -2556,29 +2820,33 @@ int ust_app_validate_version(int sock)
        app = find_app_by_sock(sock);
        assert(app);
 
+       health_code_update(&health_thread_cmd);
+
        ret = ustctl_tracer_version(sock, &app->version);
        if (ret < 0) {
                goto error;
        }
 
        /* Validate version */
-       if (app->version.major > UST_APP_MAJOR_VERSION) {
+       if (app->version.major != UST_APP_MAJOR_VERSION) {
                goto error;
        }
 
-       DBG2("UST app PID %d is compatible with major version %d "
-                       "(supporting <= %d)", app->key.pid, app->version.major,
+       DBG2("UST app PID %d is compatible with internal major version %d "
+                       "(supporting == %d)", app->pid, app->version.major,
                        UST_APP_MAJOR_VERSION);
        app->compatible = 1;
        rcu_read_unlock();
+       health_code_update(&health_thread_cmd);
        return 0;
 
 error:
-       DBG2("UST app PID %d is not compatible with major version %d "
-                       "(supporting <= %d)", app->key.pid, app->version.major,
+       DBG2("UST app PID %d is not compatible with internal major version %d "
+                       "(supporting == %d)", app->pid, app->version.major,
                        UST_APP_MAJOR_VERSION);
        app->compatible = 0;
        rcu_read_unlock();
+       health_code_update(&health_thread_cmd);
        return -1;
 }
 
@@ -2593,7 +2861,7 @@ int ust_app_calibrate_glb(struct lttng_ust_calibrate *calibrate)
 
        rcu_read_lock();
 
-       cds_lfht_for_each_entry(ust_app_ht->ht, &iter.iter, app, node.node) {
+       cds_lfht_for_each_entry(ust_app_ht->ht, &iter.iter, app, pid_n.node) {
                if (!app->compatible) {
                        /*
                         * TODO: In time, we should notice the caller of this error by
@@ -2602,7 +2870,9 @@ int ust_app_calibrate_glb(struct lttng_ust_calibrate *calibrate)
                        continue;
                }
 
-               ret = ustctl_calibrate(app->key.sock, calibrate);
+               health_code_update(&health_thread_cmd);
+
+               ret = ustctl_calibrate(app->sock, calibrate);
                if (ret < 0) {
                        switch (ret) {
                        case -ENOSYS:
@@ -2612,7 +2882,7 @@ int ust_app_calibrate_glb(struct lttng_ust_calibrate *calibrate)
                        default:
                                /* TODO: Report error to user */
                                DBG2("Calibrate app PID %d returned with error %d",
-                                               app->key.pid, ret);
+                                               app->pid, ret);
                                break;
                        }
                }
@@ -2622,5 +2892,7 @@ int ust_app_calibrate_glb(struct lttng_ust_calibrate *calibrate)
 
        rcu_read_unlock();
 
+       health_code_update(&health_thread_cmd);
+
        return ret;
 }
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