[lttng-tools.git] / lttng-sessiond / ust-app.c

/*
 * Copyright (C) 2011 - David Goulet <david.goulet@polymtl.ca>
 *
 * 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 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.
 */

#define _GNU_SOURCE
#include <errno.h>
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>

#include <urcu/compiler.h>
#include <lttngerr.h>
#include <lttng-share.h>

#include "hashtable.h"
#include "ust-app.h"
#include "ust-consumer.h"
#include "ust-ctl.h"

/*
 * Delete ust app event safely. RCU read lock must be held before calling
 * this function.
 */
static void delete_ust_app_event(int sock, struct ust_app_event *ua_event)
{
        /* TODO : remove context */
        //struct ust_app_ctx *ltctx;
        //cds_lfht_for_each_entry(lte->ctx, &iter, ltctx, node) {
        //      delete_ust_app_ctx(sock, ltctx);
        //}

        if (ua_event->obj != NULL) {
                ustctl_release_object(sock, ua_event->obj);
                free(ua_event->obj);
        }
        free(ua_event);
}

/*
 * Delete ust app stream safely. RCU read lock must be held before calling
 * this function.
 */
static void delete_ust_app_stream(int sock, struct ltt_ust_stream *stream)
{
        ustctl_release_object(sock, stream->obj);
        free(stream->obj);
        free(stream);
}

/*
 * Delete ust app channel safely. RCU read lock must be held before calling
 * this function.
 */
static void delete_ust_app_channel(int sock, struct ust_app_channel *ua_chan)
{
        int ret;
        struct cds_lfht_iter iter;
        struct ust_app_event *ua_event;
        struct ltt_ust_stream *stream, *stmp;

        cds_list_for_each_entry_safe(stream, stmp, &ua_chan->streams.head, list) {
                cds_list_del(&stream->list);
                delete_ust_app_stream(sock, stream);
        }

        /* TODO : remove channel context */
        //cds_lfht_for_each_entry(ltc->ctx, &iter, ltctx, node) {
        //      hashtable_del(ltc->ctx, &iter);
        //      delete_ust_app_ctx(sock, ltctx);
        //}
        //ret = hashtable_destroy(ltc->ctx);

        cds_lfht_for_each_entry(ua_chan->events, &iter, ua_event, node) {
                hashtable_del(ua_chan->events, &iter);
                delete_ust_app_event(sock, ua_event);
        }

        ret = hashtable_destroy(ua_chan->events);
        if (ret < 0) {
                ERR("UST app destroy session hashtable failed");
                goto error;
        }

        if (ua_chan->obj != NULL) {
                ustctl_release_object(sock, ua_chan->obj);
                free(ua_chan->obj);
        }
        free(ua_chan);

error:
        return;
}

/*
 * Delete ust app session safely. RCU read lock must be held before calling
 * this function.
 */
static void delete_ust_app_session(int sock,
                struct ust_app_session *ua_sess)
{
        int ret;
        struct cds_lfht_iter iter;
        struct ust_app_channel *ua_chan;

        if (ua_sess->metadata) {
                ustctl_release_object(sock, ua_sess->metadata->stream_obj);
                free(ua_sess->metadata->stream_obj);
                ustctl_release_object(sock, ua_sess->metadata->obj);
                free(ua_sess->metadata->obj);
        }

        cds_lfht_for_each_entry(ua_sess->channels, &iter, ua_chan, node) {
                hashtable_del(ua_sess->channels, &iter);
                delete_ust_app_channel(sock, ua_chan);
        }

        ret = hashtable_destroy(ua_sess->channels);
        if (ret < 0) {
                ERR("UST app destroy session hashtable failed");
                goto error;
        }

error:
        return;
}

/*
 * Delete a traceable application structure from the global list. Never call
 * this function outside of a call_rcu call.
 */
static void delete_ust_app(struct ust_app *app)
{
        int ret;
        struct cds_lfht_node *node;
        struct cds_lfht_iter iter;
        struct ust_app_session *ua_sess;
        int sock;

        rcu_read_lock();

        /* Remove from key hash table */
        node = hashtable_lookup(ust_app_sock_key_map,
                        (void *) ((unsigned long) app->key.sock), sizeof(void *), &iter);
        if (node == NULL) {
                /* Not suppose to happen */
                ERR("UST app key %d not found in key hash table", app->key.sock);
                goto end;
        }

        ret = hashtable_del(ust_app_sock_key_map, &iter);
        if (ret) {
                ERR("UST app unable to delete app sock %d from key hash table",
                                app->key.sock);
        } else {
                DBG2("UST app pair sock %d key %d deleted",
                                app->key.sock, app->key.pid);
        }

        /* Socket is already closed at this point */

        /* Delete ust app sessions info */
        sock = app->key.sock;
        app->key.sock = -1;

        cds_lfht_for_each_entry(app->sessions, &iter, ua_sess, node) {
                hashtable_del(app->sessions, &iter);
                delete_ust_app_session(app->key.sock, ua_sess);
        }

        ret = hashtable_destroy(app->sessions);
        if (ret < 0) {
                ERR("UST app destroy session hashtable failed");
                goto end;
        }

        /*
         * 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.
         */
        close(sock);

        DBG2("UST app pid %d deleted", app->key.pid);
        free(app);
end:
        rcu_read_unlock();
}

/*
 * URCU intermediate call to delete an UST app.
 */
static void delete_ust_app_rcu(struct rcu_head *head)
{
        struct cds_lfht_node *node =
                caa_container_of(head, struct cds_lfht_node, head);
        struct ust_app *app =
                caa_container_of(node, struct ust_app, node);

        delete_ust_app(app);
}

/*
 * Find an ust_app using the sock and return it. RCU read side lock must be
 * held before calling this helper function.
 */
static struct ust_app *find_app_by_sock(int sock)
{
        struct cds_lfht_node *node;
        struct ust_app_key *key;
        struct cds_lfht_iter iter;

        node = hashtable_lookup(ust_app_sock_key_map,
                        (void *)((unsigned long) sock), sizeof(void *), &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);

        node = hashtable_lookup(ust_app_ht,
                        (void *)((unsigned long) key->pid), sizeof(void *), &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);

error:
        return NULL;
}

/*
 * Disable the specified event on to UST tracer for the UST session.
 */
static int disable_ust_event(struct ust_app *app,
                struct ust_app_session *ua_sess, struct ust_app_event *ua_event)
{
        int ret;

        ret = ustctl_disable(app->key.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);
                goto error;
        }

        DBG2("UST app event %s disabled successfully for app (pid: %d)",
                        ua_event->attr.name, app->key.pid);

error:
        return ret;
}

/*
 * Disable the specified channel on to UST tracer for the UST session.
 */
static int disable_ust_channel(struct ust_app *app,
                struct ust_app_session *ua_sess, struct ust_app_channel *ua_chan)
{
        int ret;

        ret = ustctl_disable(app->key.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);
                goto error;
        }

        ua_chan->enabled = 0;

        DBG2("UST app channel %s disabled successfully for app (pid: %d)",
                        ua_chan->name, app->key.pid);

error:
        return ret;
}

/*
 * Enable the specified channel on to UST tracer for the UST session.
 */
static int enable_ust_channel(struct ust_app *app,
                struct ust_app_session *ua_sess, struct ust_app_channel *ua_chan)
{
        int ret;

        ret = ustctl_enable(app->key.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);
                goto error;
        }

        ua_chan->enabled = 1;

        DBG2("UST app channel %s enabled successfully for app (pid: %d)",
                        ua_chan->name, app->key.pid);

error:
        return ret;
}

/*
 * Enable the specified event on to UST tracer for the UST session.
 */
static int enable_ust_event(struct ust_app *app,
                struct ust_app_session *ua_sess, struct ust_app_event *ua_event)
{
        int ret;

        ret = ustctl_enable(app->key.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);
                goto error;
        }

        DBG2("UST app event %s enabled successfully for app (pid: %d)",
                        ua_event->attr.name, app->key.pid);

error:
        return ret;
}

/*
 * Open metadata onto the UST tracer for a UST session.
 */
static int open_ust_metadata(struct ust_app *app,
                struct ust_app_session *ua_sess)
{
        int ret;
        struct lttng_ust_channel_attr uattr;

        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;
        uattr.switch_timer_interval =
                ua_sess->metadata->attr.switch_timer_interval;
        uattr.read_timer_interval =
                ua_sess->metadata->attr.read_timer_interval;
        uattr.output = ua_sess->metadata->attr.output;

        /* UST tracer metadata creation */
        ret = ustctl_open_metadata(app->key.sock, ua_sess->handle, &uattr,
                        &ua_sess->metadata->obj);
        if (ret < 0) {
                ERR("UST app open metadata failed for app pid:%d",
                                app->key.pid);
                goto error;
        }

error:
        return ret;
}

/*
 * Create stream onto the UST tracer for a UST session.
 */
static int create_ust_stream(struct ust_app *app,
                struct ust_app_session *ua_sess)
{
        int ret;

        ret = ustctl_create_stream(app->key.sock, ua_sess->metadata->obj,
                        &ua_sess->metadata->stream_obj);
        if (ret < 0) {
                ERR("UST create metadata stream failed");
                goto error;
        }

error:
        return ret;
}

/*
 * Create the specified channel onto the UST tracer for a UST session.
 */
static int create_ust_channel(struct ust_app *app,
                struct ust_app_session *ua_sess, struct ust_app_channel *ua_chan)
{
        int ret;

        /* TODO: remove cast and use lttng-ust-abi.h */
        ret = ustctl_create_channel(app->key.sock, ua_sess->handle,
                        (struct lttng_ust_channel_attr *)&ua_chan->attr, &ua_chan->obj);
        if (ret < 0) {
                DBG("Error 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_sess->handle, ret);
                goto error;
        }

        ua_chan->handle = ua_chan->obj->handle;
        ua_chan->attr.shm_fd = ua_chan->obj->shm_fd;
        ua_chan->attr.wait_fd = ua_chan->obj->wait_fd;
        ua_chan->attr.memory_map_size = ua_chan->obj->memory_map_size;

        DBG2("UST app channel %s created successfully for pid:%d and sock:%d",
                        ua_chan->name, app->key.pid, app->key.sock);

error:
        return ret;
}

/*
 * Create the specified event onto the UST tracer for a UST session.
 */
static
int create_ust_event(struct ust_app *app, struct ust_app_session *ua_sess,
                struct ust_app_channel *ua_chan, struct ust_app_event *ua_event)
{
        int ret = 0;

        /* Create UST event on tracer */
        ret = ustctl_create_event(app->key.sock, &ua_event->attr, ua_chan->obj,
                        &ua_event->obj);
        if (ret < 0) {
                ERR("Error ustctl create event %s for app pid: %d with ret %d",
                                ua_event->attr.name, app->key.pid, ret);
                goto error;
        }

        ua_event->handle = ua_event->obj->handle;
        ua_event->enabled = 1;

        DBG2("UST app event %s created successfully for pid:%d",
                        ua_event->attr.name, app->key.pid);

error:
        return ret;
}

/*
 * Alloc new UST app session.
 */
static struct ust_app_session *alloc_ust_app_session(void)
{
        struct ust_app_session *ua_sess;

        /* Init most of the default value by allocating and zeroing */
        ua_sess = zmalloc(sizeof(struct ust_app_session));
        if (ua_sess == NULL) {
                PERROR("malloc");
                goto error;
        }

        ua_sess->handle = -1;
        ua_sess->channels = hashtable_new_str(0);

        return ua_sess;

error:
        return NULL;
}

/*
 * Alloc new UST app channel.
 */
static struct ust_app_channel *alloc_ust_app_channel(char *name,
                struct lttng_ust_channel *attr)
{
        struct ust_app_channel *ua_chan;

        /* Init most of the default value by allocating and zeroing */
        ua_chan = zmalloc(sizeof(struct ust_app_channel));
        if (ua_chan == NULL) {
                PERROR("malloc");
                goto error;
        }

        /* Setup channel name */
        strncpy(ua_chan->name, name, sizeof(ua_chan->name));
        ua_chan->name[sizeof(ua_chan->name) - 1] = '\0';

        ua_chan->handle = -1;
        ua_chan->ctx = hashtable_new(0);
        ua_chan->events = hashtable_new_str(0);
        hashtable_node_init(&ua_chan->node, (void *) ua_chan->name,
                        strlen(ua_chan->name));

        CDS_INIT_LIST_HEAD(&ua_chan->streams.head);

        /* Copy attributes */
        if (attr) {
                memcpy(&ua_chan->attr, attr, sizeof(ua_chan->attr));
        }

        DBG3("UST app channel %s allocated", ua_chan->name);

        return ua_chan;

error:
        return NULL;
}

/*
 * Alloc new UST app event.
 */
static struct ust_app_event *alloc_ust_app_event(char *name,
                struct lttng_ust_event *attr)
{
        struct ust_app_event *ua_event;

        /* Init most of the default value by allocating and zeroing */
        ua_event = zmalloc(sizeof(struct ust_app_event));
        if (ua_event == NULL) {
                PERROR("malloc");
                goto error;
        }

        strncpy(ua_event->name, name, sizeof(ua_event->name));
        ua_event->name[sizeof(ua_event->name) - 1] = '\0';
        ua_event->ctx = hashtable_new(0);
        hashtable_node_init(&ua_event->node, (void *) ua_event->name,
                        strlen(ua_event->name));

        /* Copy attributes */
        if (attr) {
                memcpy(&ua_event->attr, attr, sizeof(ua_event->attr));
        }

        DBG3("UST app event %s allocated", ua_event->name);

        return ua_event;

error:
        return NULL;
}

/*
 * Copy data between an UST app event and a LTT event.
 */
static void shadow_copy_event(struct ust_app_event *ua_event,
                struct ltt_ust_event *uevent)
{
        strncpy(ua_event->name, uevent->attr.name, sizeof(ua_event->name));
        ua_event->name[sizeof(ua_event->name) - 1] = '\0';

        /* Copy event attributes */
        memcpy(&ua_event->attr, &uevent->attr, sizeof(ua_event->attr));

        /* TODO: support copy context */
}

/*
 * Copy data between an UST app channel and a LTT channel.
 */
static void shadow_copy_channel(struct ust_app_channel *ua_chan,
                struct ltt_ust_channel *uchan)
{
        struct cds_lfht_iter iter;
        struct cds_lfht_node *ua_event_node;
        struct ltt_ust_event *uevent;
        struct ust_app_event *ua_event;

        DBG2("Shadow copy of UST app channel %s", ua_chan->name);

        strncpy(ua_chan->name, uchan->name, sizeof(ua_chan->name));
        ua_chan->name[sizeof(ua_chan->name) - 1] = '\0';
        /* Copy event attributes */
        memcpy(&ua_chan->attr, &uchan->attr, sizeof(ua_chan->attr));

        /* TODO: support copy context */

        /* Copy all events from ltt ust channel to ust app channel */
        cds_lfht_for_each_entry(uchan->events, &iter, uevent, node) {
                struct cds_lfht_iter uiter;

                ua_event_node = hashtable_lookup(ua_chan->events,
                                (void *) uevent->attr.name, strlen(uevent->attr.name),
                                &uiter);
                if (ua_event_node == 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);
                        if (ua_event == NULL) {
                                continue;
                        }
                        shadow_copy_event(ua_event, uevent);
                        hashtable_add_unique(ua_chan->events, &ua_event->node);
                }
        }

        DBG3("Shadow copy channel done");
}

/*
 * Copy data between a UST app session and a regular LTT session.
 */
static void shadow_copy_session(struct ust_app_session *ua_sess,
                struct ltt_ust_session *usess,
                struct ust_app *app)
{
        struct cds_lfht_node *ua_chan_node;
        struct cds_lfht_iter iter;
        struct ltt_ust_channel *uchan;
        struct ust_app_channel *ua_chan;
        time_t rawtime;
        struct tm *timeinfo;
        char datetime[16];
        int ret;

        /* Get date and time for unique app path */
        time(&rawtime);
        timeinfo = localtime(&rawtime);
        strftime(datetime, sizeof(datetime), "%Y%m%d-%H%M%S", timeinfo);

        DBG2("Shadow copy of session handle %d", ua_sess->handle);

        ua_sess->uid = usess->uid;

        ret = snprintf(ua_sess->path, PATH_MAX,
                        "%s/%s-%d-%s",
                        usess->pathname, app->name, app->key.pid,
                        datetime);
        if (ret < 0) {
                PERROR("asprintf UST shadow copy session");
                /* TODO: We cannot return an error from here.. */
                assert(0);
        }

        /* TODO: support all UST domain */

        /* Iterate over all channels in global domain. */
        cds_lfht_for_each_entry(usess->domain_global.channels, &iter,
                        uchan, node) {
                struct cds_lfht_iter uiter;

                ua_chan_node = hashtable_lookup(ua_sess->channels,
                                (void *)uchan->name, strlen(uchan->name),
                                &uiter);
                if (ua_chan_node != NULL) {
                        continue;
                }

                DBG2("Channel %s not found on shadow session copy, creating it",
                                uchan->name);
                ua_chan = alloc_ust_app_channel(uchan->name, &uchan->attr);
                if (ua_chan == NULL) {
                        /* malloc failed... continuing */
                        continue;
                }

                shadow_copy_channel(ua_chan, uchan);
                hashtable_add_unique(ua_sess->channels, &ua_chan->node);
        }
}

/*
 * Lookup sesison wrapper.
 */
static
void __lookup_session_by_app(struct ltt_ust_session *usess,
                        struct ust_app *app, struct cds_lfht_iter *iter)
{
        /* Get right UST app session from app */
        (void) hashtable_lookup(app->sessions,
                        (void *) ((unsigned long) usess->uid), sizeof(void *),
                        iter);
}

/*
 * Return ust app session from the app session hashtable using the UST session
 * uid.
 */
static struct ust_app_session *lookup_session_by_app(
                struct ltt_ust_session *usess, struct ust_app *app)
{
        struct cds_lfht_iter iter;
        struct cds_lfht_node *node;

        __lookup_session_by_app(usess, app, &iter);
        node = hashtable_iter_get_node(&iter);
        if (node == NULL) {
                goto error;
        }

        return caa_container_of(node, struct ust_app_session, node);

error:
        return NULL;
}

/*
 * Create a UST session onto the tracer of app and add it the session
 * hashtable.
 *
 * Return ust app session or NULL on error.
 */
static struct ust_app_session *create_ust_app_session(
                struct ltt_ust_session *usess, struct ust_app *app)
{
        int ret;
        struct ust_app_session *ua_sess;

        ua_sess = lookup_session_by_app(usess, app);
        if (ua_sess == NULL) {
                DBG2("UST app pid: %d session uid %d not found, creating it",
                                app->key.pid, usess->uid);
                ua_sess = alloc_ust_app_session();
                if (ua_sess == NULL) {
                        /* Only malloc can failed so something is really wrong */
                        goto error;
                }
                shadow_copy_session(ua_sess, usess, app);
        }

        if (ua_sess->handle == -1) {
                ret = ustctl_create_session(app->key.sock);
                if (ret < 0) {
                        ERR("Error creating session for app pid %d, sock %d",
                                        app->key.pid, app->key.sock);
                        /* TODO: free() ua_sess */
                        goto error;
                }

                DBG2("UST app ustctl create session handle %d", ret);
                ua_sess->handle = ret;

                /* Add ust app session to app's HT */
                hashtable_node_init(&ua_sess->node,
                                (void *)((unsigned long) ua_sess->uid), sizeof(void *));
                hashtable_add_unique(app->sessions, &ua_sess->node);

                DBG2("UST app session created successfully with handle %d", ret);
        }

        return ua_sess;

error:
        return NULL;
}

/*
 * Enable on the tracer side a ust app event for the session and channel.
 */
static
int enable_ust_app_event(struct ust_app_session *ua_sess,
                struct ust_app_channel *ua_chan, struct ust_app_event *ua_event,
                struct ust_app *app)
{
        int ret;

        ret = enable_ust_event(app, ua_sess, ua_event);
        if (ret < 0) {
                goto error;
        }

        ua_event->enabled = 1;

error:
        return ret;
}

/*
 * Disable on the tracer side a ust app event for the session and channel.
 */
static int disable_ust_app_event(struct ust_app_session *ua_sess,
                struct ust_app_channel *ua_chan, struct ust_app_event *ua_event,
                struct ust_app *app)
{
        int ret;

        ret = disable_ust_event(app, ua_sess, ua_event);
        if (ret < 0) {
                goto error;
        }

        ua_event->enabled = 0;

error:
        return ret;
}

/*
 * Lookup ust app channel for session and disable it on the tracer side.
 */
static int disable_ust_app_channel(struct ust_app_session *ua_sess,
                struct ltt_ust_channel *uchan, struct ust_app *app)
{
        int ret = 0;
        struct cds_lfht_iter iter;
        struct cds_lfht_node *ua_chan_node;
        struct ust_app_channel *ua_chan;

        ua_chan_node = hashtable_lookup(ua_sess->channels,
                        (void *)uchan->name, strlen(uchan->name), &iter);
        if (ua_chan_node == NULL) {
                DBG2("Unable to find channel %s in ust session uid %u",
                                uchan->name, ua_sess->uid);
                goto error;
        }

        ua_chan = caa_container_of(ua_chan_node, struct ust_app_channel, node);

        ret = disable_ust_channel(app, ua_sess, ua_chan);
        if (ret < 0) {
                goto error;
        }

error:
        return ret;
}

/*
 * Lookup ust app channel for session and enable it on the tracer side.
 */
static int enable_ust_app_channel(struct ust_app_session *ua_sess,
                struct ltt_ust_channel *uchan, struct ust_app *app)
{
        int ret = 0;
        struct cds_lfht_iter iter;
        struct cds_lfht_node *ua_chan_node;
        struct ust_app_channel *ua_chan;

        ua_chan_node = hashtable_lookup(ua_sess->channels,
                        (void *)uchan->name, strlen(uchan->name), &iter);
        if (ua_chan_node == NULL) {
                DBG2("Unable to find channel %s in ust session uid %u",
                                uchan->name, ua_sess->uid);
                goto error;
        }

        ua_chan = caa_container_of(ua_chan_node, struct ust_app_channel, node);

        ret = enable_ust_channel(app, ua_sess, ua_chan);
        if (ret < 0) {
                goto error;
        }

error:
        return ret;
}

/*
 * Create UST app channel and create it on the tracer.
 */
static struct ust_app_channel *create_ust_app_channel(
                struct ust_app_session *ua_sess, struct ltt_ust_channel *uchan,
                struct ust_app *app)
{
        int ret = 0;
        struct cds_lfht_iter iter;
        struct cds_lfht_node *ua_chan_node;
        struct ust_app_channel *ua_chan;

        /* Lookup channel in the ust app session */
        ua_chan_node = hashtable_lookup(ua_sess->channels,
                        (void *)uchan->name, strlen(uchan->name), &iter);
        if (ua_chan_node == NULL) {
                DBG2("Unable to find channel %s in ust session uid %u",
                                uchan->name, ua_sess->uid);
                ua_chan = alloc_ust_app_channel(uchan->name, &uchan->attr);
                if (ua_chan == NULL) {
                        goto error;
                }
                shadow_copy_channel(ua_chan, uchan);

                hashtable_add_unique(ua_sess->channels, &ua_chan->node);
        } else {
                ua_chan = caa_container_of(ua_chan_node, struct ust_app_channel, node);
        }

        ret = create_ust_channel(app, ua_sess, ua_chan);
        if (ret < 0) {
                goto error;
        }

        return ua_chan;

error:
        return NULL;
}

/*
 * Create UST app event and create it on the tracer side.
 */
static
int create_ust_app_event(struct ust_app_session *ua_sess,
                struct ust_app_channel *ua_chan, struct ltt_ust_event *uevent,
                struct ust_app *app)
{
        int ret = 0;
        struct cds_lfht_iter iter;
        struct cds_lfht_node *ua_event_node;
        struct ust_app_event *ua_event;

        /* Get event node */
        ua_event_node = hashtable_lookup(ua_chan->events,
                        (void *)uevent->attr.name, strlen(uevent->attr.name), &iter);
        if (ua_event_node != NULL) {
                ERR("UST app event %s already exist. Stopping creation.",
                                uevent->attr.name);
                goto end;
        }

        /* Does not exist so create one */
        ua_event = alloc_ust_app_event(uevent->attr.name, &uevent->attr);
        if (ua_event == NULL) {
                /* Only malloc can failed so something is really wrong */
                ret = -ENOMEM;
                goto error;
        }
        shadow_copy_event(ua_event, uevent);

        /* Create it on the tracer side */
        ret = create_ust_event(app, ua_sess, ua_chan, ua_event);
        if (ret < 0) {
                delete_ust_app_event(app->key.sock, ua_event);
                goto error;
        }

        hashtable_add_unique(ua_chan->events, &ua_event->node);

end:
error:
        return ret;
}

/*
 * Create UST metadata and open it on the tracer side.
 */
static int create_ust_app_metadata(struct ust_app_session *ua_sess,
                char *pathname, struct ust_app *app)
{
        int ret = 0;

        if (ua_sess->metadata == NULL) {
                /* Allocate UST metadata */
                ua_sess->metadata = trace_ust_create_metadata(pathname);
                if (ua_sess->metadata == NULL) {
                        ERR("UST app session %d creating metadata failed",
                                        ua_sess->handle);
                        goto error;
                }

                ret = open_ust_metadata(app, ua_sess);
                if (ret < 0) {
                        goto error;
                }

                DBG2("UST metadata opened for app pid %d", app->key.pid);
        }

        /* Open UST metadata stream */
        if (ua_sess->metadata->stream_obj == NULL) {
                ret = create_ust_stream(app, ua_sess);
                if (ret < 0) {
                        goto error;
                }

                ret = mkdir(ua_sess->path, S_IRWXU | S_IRWXG);
                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) {
                        PERROR("asprintf UST create stream");
                        goto error;
                }

                DBG2("UST metadata stream object created for app pid %d",
                                app->key.pid);
        } else {
                ERR("Attempting to create stream without metadata opened");
                goto error;
        }

        return 0;

error:
        return -1;
}

/*
 * Return pointer to traceable apps list.
 */
struct cds_lfht *ust_app_get_ht(void)
{
        return ust_app_ht;
}

/*
 * Return ust app pointer or NULL if not found.
 */
struct ust_app *ust_app_find_by_pid(pid_t pid)
{
        struct cds_lfht_node *node;
        struct cds_lfht_iter iter;

        rcu_read_lock();
        node = hashtable_lookup(ust_app_ht,
                        (void *)((unsigned long) pid), sizeof(void *), &iter);
        if (node == NULL) {
                DBG2("UST app no found with pid %d", pid);
                goto error;
        }
        rcu_read_unlock();

        DBG2("Found UST app by pid %d", pid);

        return caa_container_of(node, struct ust_app, node);

error:
        rcu_read_unlock();
        return NULL;
}

/*
 * Using pid and uid (of the app), allocate a new ust_app struct and
 * add it to the global traceable app list.
 *
 * On success, return 0, else return malloc -ENOMEM, or -EINVAL if app
 * bitness is not supported.
 */
int ust_app_register(struct ust_register_msg *msg, int sock)
{
        struct ust_app *lta;

        if ((msg->bits_per_long == 64 && ust_consumerd64_fd == -EINVAL)
                        || (msg->bits_per_long == 32 && 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);
                close(sock);
                return -EINVAL;
        }
        lta = zmalloc(sizeof(struct ust_app));
        if (lta == NULL) {
                PERROR("malloc");
                return -ENOMEM;
        }

        lta->ppid = msg->ppid;
        lta->uid = msg->uid;
        lta->gid = msg->gid;
        lta->bits_per_long = msg->bits_per_long;
        lta->v_major = msg->major;
        lta->v_minor = msg->minor;
        strncpy(lta->name, msg->name, sizeof(lta->name));
        lta->name[16] = '\0';
        lta->sessions = hashtable_new(0);

        /* Set key map */
        lta->key.pid = msg->pid;
        hashtable_node_init(&lta->node, (void *)((unsigned long)lta->key.pid),
                        sizeof(void *));
        lta->key.sock = sock;
        hashtable_node_init(&lta->key.node, (void *)((unsigned long)lta->key.sock),
                        sizeof(void *));

        rcu_read_lock();
        hashtable_add_unique(ust_app_sock_key_map, &lta->key.node);
        hashtable_add_unique(ust_app_ht, &lta->node);
        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);

        return 0;
}

/*
 * Unregister app by removing it from the global traceable app list and freeing
 * the data struct.
 *
 * The socket is already closed at this point so no close to sock.
 */
void ust_app_unregister(int sock)
{
        struct ust_app *lta;
        struct cds_lfht_node *node;
        struct cds_lfht_iter iter;

        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);

        /* Get the node reference for a call_rcu */
        node = hashtable_lookup(ust_app_ht,
                        (void *)((unsigned long) lta->key.pid), sizeof(void *), &iter);
        if (node == NULL) {
                ERR("Unable to find app sock %d by pid %d", sock, lta->key.pid);
                goto error;
        }

        hashtable_del(ust_app_ht, &iter);
        call_rcu(&node->head, delete_ust_app_rcu);
error:
        rcu_read_unlock();
        return;
}

/*
 * Return traceable_app_count
 */
unsigned long ust_app_list_count(void)
{
        unsigned long count;

        rcu_read_lock();
        count = hashtable_get_count(ust_app_ht);
        rcu_read_unlock();

        return count;
}

/*
 * Fill events array with all events name of all registered apps.
 */
int ust_app_list_events(struct lttng_event **events)
{
        int ret, handle;
        size_t nbmem, count = 0;
        struct cds_lfht_iter iter;
        struct ust_app *app;
        struct lttng_event *tmp;

        nbmem = UST_APP_EVENT_LIST_SIZE;
        tmp = zmalloc(nbmem * sizeof(struct lttng_event));
        if (tmp == NULL) {
                PERROR("zmalloc ust app events");
                ret = -ENOMEM;
                goto error;
        }

        rcu_read_lock();

        cds_lfht_for_each_entry(ust_app_ht, &iter, app, node) {
                handle = ustctl_tracepoint_list(app->key.sock);
                if (handle < 0) {
                        ERR("UST app list events getting handle failed for app pid %d",
                                        app->key.pid);
                        continue;
                }

                while ((ret = ustctl_tracepoint_list_get(app->key.sock, handle,
                                                tmp[count].name)) != -ENOENT) {
                        if (count > nbmem) {
                                DBG2("Reallocating event list from %zu to %zu bytes", nbmem,
                                                nbmem + UST_APP_EVENT_LIST_SIZE);
                                nbmem += UST_APP_EVENT_LIST_SIZE;
                                tmp = realloc(tmp, nbmem);
                                if (tmp == NULL) {
                                        PERROR("realloc ust app events");
                                        ret = -ENOMEM;
                                        goto rcu_error;
                                }
                        }

                        tmp[count].type = LTTNG_UST_TRACEPOINT;
                        tmp[count].pid = app->key.pid;
                        tmp[count].enabled = -1;
                        count++;
                }
        }

        ret = count;
        *events = tmp;

        DBG2("UST app list events done (%zu events)", count);

rcu_error:
        rcu_read_unlock();
error:
        return ret;
}

/*
 * Free and clean all traceable apps of the global list.
 */
void ust_app_clean_list(void)
{
        int ret;
        struct cds_lfht_node *node;
        struct cds_lfht_iter iter;
        struct ust_app *app;

        DBG2("UST app cleaning registered apps hash table");

        rcu_read_lock();

        cds_lfht_for_each_entry(ust_app_ht, &iter, app, node) {
                ret = hashtable_del(ust_app_ht, &iter);
                if (!ret) {
                        call_rcu(&node->head, delete_ust_app_rcu);
                }
        }

        hashtable_destroy(ust_app_ht);
        hashtable_destroy(ust_app_sock_key_map);

        rcu_read_unlock();
}

/*
 * Init UST app hash table.
 */
void ust_app_ht_alloc(void)
{
        ust_app_ht = hashtable_new(0);
        ust_app_sock_key_map = hashtable_new(0);
}

/*
 * For a specific UST session, disable the channel for all registered apps.
 */
int ust_app_disable_channel_all(struct ltt_ust_session *usess,
                struct ltt_ust_channel *uchan)
{
        int ret = 0;
        struct cds_lfht_iter iter;
        struct ust_app *app;
        struct ust_app_session *ua_sess;

        if (usess == NULL || uchan == NULL) {
                ERR("Disabling UST global channel with NULL values");
                ret = -1;
                goto error;
        }

        DBG2("UST app disablling channel %s from global domain for session uid %d",
                        uchan->name, usess->uid);

        rcu_read_lock();

        /* For every registered applications */
        cds_lfht_for_each_entry(ust_app_ht, &iter, app, node) {
                ua_sess = lookup_session_by_app(usess, app);
                if (ua_sess == NULL) {
                        continue;
                }

                /* Create channel onto application */
                ret = disable_ust_app_channel(ua_sess, uchan, app);
                if (ret < 0) {
                        /* XXX: We might want to report this error at some point... */
                        continue;
                }
        }

        rcu_read_unlock();

error:
        return ret;
}

/*
 * For a specific UST session, enable the channel for all registered apps.
 */
int ust_app_enable_channel_all(struct ltt_ust_session *usess,
                struct ltt_ust_channel *uchan)
{
        int ret = 0;
        struct cds_lfht_iter iter;
        struct ust_app *app;
        struct ust_app_session *ua_sess;

        if (usess == NULL || uchan == NULL) {
                ERR("Adding UST global channel to NULL values");
                ret = -1;
                goto error;
        }

        DBG2("UST app enabling channel %s to global domain for session uid %d",
                        uchan->name, usess->uid);

        rcu_read_lock();

        /* For every registered applications */
        cds_lfht_for_each_entry(ust_app_ht, &iter, app, node) {
                ua_sess = lookup_session_by_app(usess, app);
                if (ua_sess == NULL) {
                        continue;
                }

                /* Enable channel onto application */
                ret = enable_ust_app_channel(ua_sess, uchan, app);
                if (ret < 0) {
                        /* XXX: We might want to report this error at some point... */
                        continue;
                }
        }

        rcu_read_unlock();

error:
        return ret;
}

/*
 * Disable an event in a channel and for a specific session.
 */
int ust_app_disable_event(struct ltt_ust_session *usess,
                struct ltt_ust_channel *uchan, char *event_name)
{
        int ret = 0;
        struct cds_lfht_iter iter, uiter;
        struct cds_lfht_node *ua_chan_node, *ua_event_node;
        struct ust_app *app;
        struct ust_app_session *ua_sess;
        struct ust_app_channel *ua_chan;
        struct ust_app_event *ua_event;

        DBG("UST app disabling event %s for all apps in channel "
                        "%s for session uid %d", event_name, uchan->name, usess->uid);

        rcu_read_lock();

        /* For all registered applications */
        cds_lfht_for_each_entry(ust_app_ht, &iter, app, node) {
                ua_sess = lookup_session_by_app(usess, app);
                if (ua_sess == NULL) {
                        /* Next app */
                        continue;
                }

                /* Lookup channel in the ust app session */
                ua_chan_node = hashtable_lookup(ua_sess->channels,
                                (void *)uchan->name, strlen(uchan->name), &uiter);
                if (ua_chan_node == NULL) {
                        DBG2("Channel %s not found in session uid %d for app pid %d."
                                        "Skipping", uchan->name, usess->uid, app->key.pid);
                        continue;
                }
                ua_chan = caa_container_of(ua_chan_node, struct ust_app_channel, node);

                ua_event_node = hashtable_lookup(ua_chan->events,
                                (void *) event_name, strlen(event_name), &uiter);
                if (ua_event_node == NULL) {
                        DBG2("Event %s not found in channel %s for app pid %d."
                                        "Skipping", event_name, uchan->name, app->key.pid);
                        continue;
                }
                ua_event = caa_container_of(ua_event_node, struct ust_app_event, node);

                ret = disable_ust_app_event(ua_sess, ua_chan, ua_event, app);
                if (ret < 0) {
                        /* XXX: Report error someday... */
                        continue;
                }
        }

        rcu_read_unlock();

        return ret;
}

/*
 * For a specific UST session and UST channel, the event for all
 * registered apps.
 */
int ust_app_disable_event_all(struct ltt_ust_session *usess,
                struct ltt_ust_channel *uchan)
{
        int ret = 0;
        struct cds_lfht_iter iter, uiter;
        struct cds_lfht_node *ua_chan_node;
        struct ust_app *app;
        struct ust_app_session *ua_sess;
        struct ust_app_channel *ua_chan;
        struct ust_app_event *ua_event;

        DBG("UST app disabling all event for all apps in channel "
                        "%s for session uid %d", uchan->name, usess->uid);

        rcu_read_lock();

        /* For all registered applications */
        cds_lfht_for_each_entry(ust_app_ht, &iter, app, node) {
                ua_sess = lookup_session_by_app(usess, app);
                /* If ua_sess is NULL, there is a code flow error */
                assert(ua_sess);

                /* Lookup channel in the ust app session */
                ua_chan_node = hashtable_lookup(ua_sess->channels, (void *)uchan->name,
                                strlen(uchan->name), &uiter);
                /* If the channel is not found, there is a code flow error */
                assert(ua_chan_node);

                ua_chan = caa_container_of(ua_chan_node, struct ust_app_channel, node);

                /* Disable each events of channel */
                cds_lfht_for_each_entry(ua_chan->events, &uiter, ua_event, node) {
                        ret = disable_ust_app_event(ua_sess, ua_chan, ua_event, app);
                        if (ret < 0) {
                                /* XXX: Report error someday... */
                                continue;
                        }
                }
        }

        rcu_read_unlock();

        return ret;
}

/*
 * For a specific UST session, create the channel for all registered apps.
 */
int ust_app_create_channel_all(struct ltt_ust_session *usess,
                struct ltt_ust_channel *uchan)
{
        int ret = 0;
        struct cds_lfht_iter iter;
        struct ust_app *app;
        struct ust_app_session *ua_sess;
        struct ust_app_channel *ua_chan;

        if (usess == NULL || uchan == NULL) {
                ERR("Adding UST global channel to NULL values");
                ret = -1;
                goto error;
        }

        DBG2("UST app adding channel %s to global domain for session uid %d",
                        uchan->name, usess->uid);

        rcu_read_lock();

        /* For every registered applications */
        cds_lfht_for_each_entry(ust_app_ht, &iter, app, node) {
                /*
                 * Create session on the tracer side and add it to app session HT. Note
                 * that if session exist, it will simply return a pointer to the ust
                 * app session.
                 */
                ua_sess = create_ust_app_session(usess, app);
                if (ua_sess == NULL) {
                        continue;
                }

                /* Create channel onto application */
                ua_chan = create_ust_app_channel(ua_sess, uchan, app);
                if (ua_chan == NULL) {
                        continue;
                }
        }

        rcu_read_unlock();

error:
        return ret;
}

/*
 * Enable event for a specific session and channel on the tracer.
 */
int ust_app_enable_event_all(struct ltt_ust_session *usess,
                struct ltt_ust_channel *uchan, struct ltt_ust_event *uevent)
{
        int ret = 0;
        struct cds_lfht_iter iter, uiter;
        struct cds_lfht_node *ua_chan_node;
        struct ust_app *app;
        struct ust_app_session *ua_sess;
        struct ust_app_channel *ua_chan;
        struct ust_app_event *ua_event;

        DBG("UST app enabling event %s for all apps for session uid %d",
                        uevent->attr.name, usess->uid);

        /*
         * NOTE: At this point, this function is called only if the session and
         * channel passed are already created for all apps. and enabled on the
         * tracer also.
         */

        rcu_read_lock();

        /* For all registered applications */
        cds_lfht_for_each_entry(ust_app_ht, &iter, app, node) {
                ua_sess = lookup_session_by_app(usess, app);
                /* If ua_sess is NULL, there is a code flow error */
                assert(ua_sess);

                /* Lookup channel in the ust app session */
                ua_chan_node = hashtable_lookup(ua_sess->channels, (void *)uchan->name,
                                strlen(uchan->name), &uiter);
                /* If the channel is not found, there is a code flow error */
                assert(ua_chan_node);

                ua_chan = caa_container_of(ua_chan_node, struct ust_app_channel, node);

                /* Enable each events of channel */
                cds_lfht_for_each_entry(ua_chan->events, &uiter, ua_event, node) {
                        ret = enable_ust_app_event(ua_sess, ua_chan, ua_event, app);
                        if (ret < 0) {
                                /* XXX: Report error someday... */
                                continue;
                        }
                }
        }

        rcu_read_unlock();

        return ret;
}

/*
 * For a specific existing UST session and UST channel, creates the event for
 * all registered apps.
 */
int ust_app_create_event_all(struct ltt_ust_session *usess,
                struct ltt_ust_channel *uchan, struct ltt_ust_event *uevent)
{
        int ret = 0;
        struct cds_lfht_iter iter, uiter;
        struct cds_lfht_node *ua_chan_node;
        struct ust_app *app;
        struct ust_app_session *ua_sess;
        struct ust_app_channel *ua_chan;

        DBG("UST app creating event %s for all apps for session uid %d",
                        uevent->attr.name, usess->uid);

        /*
         * NOTE: At this point, this function is called only if the session and
         * channel passed are already created for all apps. and enabled on the
         * tracer also.
         */

        rcu_read_lock();

        /* For all registered applications */
        cds_lfht_for_each_entry(ust_app_ht, &iter, app, node) {
                ua_sess = lookup_session_by_app(usess, app);
                /* If ua_sess is NULL, there is a code flow error */
                assert(ua_sess);

                /* Lookup channel in the ust app session */
                ua_chan_node = hashtable_lookup(ua_sess->channels, (void *)uchan->name,
                                strlen(uchan->name), &uiter);
                /* If the channel is not found, there is a code flow error */
                assert(ua_chan_node);

                ua_chan = caa_container_of(ua_chan_node, struct ust_app_channel, node);

                ret = create_ust_app_event(ua_sess, ua_chan, uevent, app);
                if (ret < 0) {
                        continue;
                }
        }

        rcu_read_unlock();

        return ret;
}

/*
 * Start tracing for a specific UST session and app.
 */
int ust_app_start_trace(struct ltt_ust_session *usess, struct ust_app *app)
{
        int ret = 0;
        struct cds_lfht_iter iter;
        struct ust_app_session *ua_sess;
        struct ust_app_channel *ua_chan;
        struct ltt_ust_stream *ustream;
        int consumerd_fd;

        DBG("Starting tracing for ust app pid %d", app->key.pid);

        rcu_read_lock();

        ua_sess = lookup_session_by_app(usess, app);
        if (ua_sess == NULL) {
                goto error_rcu_unlock;
        }

        /* Upon restart, we skip the setup, already done */
        if (ua_sess->started) {
                goto skip_setup;
        }

        ret = create_ust_app_metadata(ua_sess, usess->pathname, app);
        if (ret < 0) {
                goto error_rcu_unlock;
        }

        /* For each channel */
        cds_lfht_for_each_entry(ua_sess->channels, &iter, ua_chan, node) {
                /* Create all streams */
                while (1) {
                        /* Create UST stream */
                        ustream = zmalloc(sizeof(*ustream));
                        if (ustream == NULL) {
                                PERROR("zmalloc ust stream");
                                goto error_rcu_unlock;
                        }

                        ret = ustctl_create_stream(app->key.sock, ua_chan->obj,
                                        &ustream->obj);
                        if (ret < 0) {
                                /* Got all streams */
                                break;
                        }
                        ustream->handle = ustream->obj->handle;

                        /* 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++);
                        if (ret < 0) {
                                PERROR("asprintf UST create stream");
                                continue;
                        }
                        DBG2("UST stream %d ready at %s", ua_chan->streams.count,
                                        ustream->pathname);
                }
        }

        switch (app->bits_per_long) {
        case 64:
                consumerd_fd = ust_consumerd64_fd;
                break;
        case 32:
                consumerd_fd = ust_consumerd32_fd;
                break;
        default:
                ret = -EINVAL;
                goto error_rcu_unlock;
        }

        /* Setup UST consumer socket and send fds to it */
        ret = ust_consumer_send_session(consumerd_fd, ua_sess);
        if (ret < 0) {
                goto error_rcu_unlock;
        }
        ua_sess->started = 1;

skip_setup:
        /* This start the UST tracing */
        ret = ustctl_start_session(app->key.sock, ua_sess->handle);
        if (ret < 0) {
                ERR("Error starting tracing for app pid: %d", app->key.pid);
                goto error_rcu_unlock;
        }

        rcu_read_unlock();

        /* Quiescent wait after starting trace */
        ustctl_wait_quiescent(app->key.sock);

        return 0;

error_rcu_unlock:
        rcu_read_unlock();
        return -1;
}

/*
 * Stop tracing for a specific UST session and app.
 */
int ust_app_stop_trace(struct ltt_ust_session *usess, struct ust_app *app)
{
        int ret = 0;
        struct ust_app_session *ua_sess;

        DBG("Stopping tracing for ust app pid %d", app->key.pid);

        rcu_read_lock();

        ua_sess = lookup_session_by_app(usess, app);
        if (ua_sess == NULL) {
                /* Only malloc can failed so something is really wrong */
                goto error_rcu_unlock;
        }

#if 0   /* only useful when periodical flush will be supported */
        /* need to keep a handle on shm in session for this. */
        /* Flush all buffers before stopping */
        ret = ustctl_flush_buffer(usess->sock, usess->metadata->obj);
        if (ret < 0) {
                ERR("UST metadata flush failed");
        }

        cds_list_for_each_entry(ustchan, &usess->channels.head, list) {
                ret = ustctl_flush_buffer(usess->sock, ustchan->obj);
                if (ret < 0) {
                        ERR("UST flush buffer error");
                }
        }
#endif

        /* This inhibits UST tracing */
        ret = ustctl_stop_session(app->key.sock, ua_sess->handle);
        if (ret < 0) {
                ERR("Error stopping tracing for app pid: %d", app->key.pid);
                goto error_rcu_unlock;
        }

        rcu_read_unlock();

        /* Quiescent wait after stopping trace */
        ustctl_wait_quiescent(app->key.sock);

        return 0;

error_rcu_unlock:
        rcu_read_unlock();
        return -1;
}

/*
 * Destroy a specific UST session in apps.
 */
int ust_app_destroy_trace(struct ltt_ust_session *usess, struct ust_app *app)
{
        struct ust_app_session *ua_sess;
        struct lttng_ust_object_data obj;
        struct cds_lfht_iter iter;
        struct cds_lfht_node *node;

        DBG("Destroy tracing for ust app pid %d", app->key.pid);

        rcu_read_lock();

        __lookup_session_by_app(usess, app, &iter);
        node = hashtable_iter_get_node(&iter);
        if (node == NULL) {
                /* Only malloc can failed so something is really wrong */
                goto error_rcu_unlock;
        }
        ua_sess = caa_container_of(node, struct ust_app_session, node);
        hashtable_del(app->sessions, &iter);
        delete_ust_app_session(app->key.sock, ua_sess);
        obj.handle = ua_sess->handle;
        obj.shm_fd = -1;
        obj.wait_fd = -1;
        obj.memory_map_size = 0;
        ustctl_release_object(app->key.sock, &obj);

        rcu_read_unlock();

        /* Quiescent wait after stopping trace */
        ustctl_wait_quiescent(app->key.sock);

        return 0;

error_rcu_unlock:
        rcu_read_unlock();
        return -1;
}

/*
 * Start tracing for the UST session.
 */
int ust_app_start_trace_all(struct ltt_ust_session *usess)
{
        int ret = 0;
        struct cds_lfht_iter iter;
        struct ust_app *app;

        DBG("Starting all UST traces");

        rcu_read_lock();

        cds_lfht_for_each_entry(ust_app_ht, &iter, app, node) {
                ret = ust_app_start_trace(usess, app);
                if (ret < 0) {
                        /* Continue to next apps even on error */
                        continue;
                }
        }

        rcu_read_unlock();

        return 0;
}

/*
 * Start tracing for the UST session.
 */
int ust_app_stop_trace_all(struct ltt_ust_session *usess)
{
        int ret = 0;
        struct cds_lfht_iter iter;
        struct ust_app *app;

        DBG("Stopping all UST traces");

        rcu_read_lock();

        cds_lfht_for_each_entry(ust_app_ht, &iter, app, node) {
                ret = ust_app_stop_trace(usess, app);
                if (ret < 0) {
                        /* Continue to next apps even on error */
                        continue;
                }
        }

        rcu_read_unlock();

        return 0;
}

/*
 * Destroy app UST session.
 */
int ust_app_destroy_trace_all(struct ltt_ust_session *usess)
{
        int ret = 0;
        struct cds_lfht_iter iter;
        struct ust_app *app;

        DBG("Destroy all UST traces");

        rcu_read_lock();

        cds_lfht_for_each_entry(ust_app_ht, &iter, app, node) {
                ret = ust_app_destroy_trace(usess, app);
                if (ret < 0) {
                        /* Continue to next apps even on error */
                        continue;
                }
        }

        rcu_read_unlock();

        return 0;
}

/*
 * Add channels/events from UST global domain to registered apps at sock.
 */
void ust_app_global_update(struct ltt_ust_session *usess, int sock)
{
        int ret = 0;
        struct cds_lfht_iter iter;
        struct ust_app *app;
        struct ust_app_session *ua_sess;
        struct ust_app_channel *ua_chan;
        struct ust_app_event *ua_event;

        if (usess == NULL) {
                ERR("No UST session on global update. Returning");
                goto error;
        }

        DBG2("UST app global update for app sock %d for session uid %d", sock,
                        usess->uid);

        rcu_read_lock();

        app = find_app_by_sock(sock);
        if (app == NULL) {
                ERR("Failed to update app sock %d", sock);
                goto error;
        }

        ua_sess = create_ust_app_session(usess, app);
        if (ua_sess == NULL) {
                goto error;
        }

        /*
         * We can iterate safely here over all UST app session sicne the create ust
         * app session above made a shadow copy of the UST global domain from the
         * ltt ust session.
         */
        cds_lfht_for_each_entry(ua_sess->channels, &iter, ua_chan, node) {
                ret = create_ust_channel(app, ua_sess, ua_chan);
                if (ret < 0) {
                        /* FIXME: Should we quit here or continue... */
                        continue;
                }

                /* For each events */
                cds_lfht_for_each_entry(ua_chan->events, &iter, ua_event, node) {
                        ret = create_ust_event(app, ua_sess, ua_chan, ua_event);
                        if (ret < 0) {
                                /* FIXME: Should we quit here or continue... */
                                continue;
                        }
                }
        }

        if (usess->start_trace) {
                ret = ust_app_start_trace(usess, app);
                if (ret < 0) {
                        goto error;
                }

                DBG2("UST trace started for app pid %d", app->key.pid);
        }

error:
        rcu_read_unlock();
        return;
}