[lttng-ust.git] / liblttng-ust / ltt-events.c

/*
 * ltt-events.c
 *
 * Holds LTTng per-session event registry.
 *
 * Copyright (C) 2010-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; only
 * version 2.1 of the License.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#define _GNU_SOURCE
#include <stdio.h>
#include <urcu/list.h>
#include <urcu/hlist.h>
#include <pthread.h>
#include <errno.h>
#include <sys/shm.h>
#include <sys/ipc.h>
#include <stdint.h>
#include <stddef.h>
#include <inttypes.h>
#include <time.h>
#include <lttng/ust-endian.h>
#include "clock.h"

#include <urcu-bp.h>
#include <urcu/compiler.h>
#include <urcu/uatomic.h>
#include <urcu/arch.h>

#include <lttng/tracepoint.h>
#include <lttng/ust-events.h>

#include <usterr-signal-safe.h>
#include <helper.h>
#include "error.h"
#include "compat.h"
#include "lttng-ust-uuid.h"

#include "tracepoint-internal.h"
#include "ltt-tracer.h"
#include "ltt-tracer-core.h"
#include "wait.h"
#include "../libringbuffer/shm.h"
#include "jhash.h"

/*
 * The sessions mutex is the centralized mutex across UST tracing
 * control and probe registration. All operations within this file are
 * called by the communication thread, under ust_lock protection.
 */
static pthread_mutex_t sessions_mutex = PTHREAD_MUTEX_INITIALIZER;

void ust_lock(void)
{
        pthread_mutex_lock(&sessions_mutex);
}

void ust_unlock(void)
{
        pthread_mutex_unlock(&sessions_mutex);
}

static CDS_LIST_HEAD(sessions);

/*
 * Wildcard list, containing the active wildcards.
 * Protected by ust lock.
 */
static CDS_LIST_HEAD(wildcard_list);

/*
 * Pending probes hash table, containing the registered ltt events for
 * which tracepoint probes are still missing. Protected by the sessions
 * mutex.
 */
#define PENDING_PROBE_HASH_BITS         6
#define PENDING_PROBE_HASH_SIZE         (1 << PENDING_PROBE_HASH_BITS)
static struct cds_hlist_head pending_probe_table[PENDING_PROBE_HASH_SIZE];

struct ust_pending_probe {
        struct ltt_event *event;
        struct cds_hlist_node node;
        enum lttng_ust_loglevel_type loglevel_type;
        int loglevel;
        char name[];
};

/*
 * Callsite hash table, containing the registered callsites.
 * Protected by the sessions mutex.
 */
#define CALLSITE_HASH_BITS              6
#define CALLSITE_HASH_SIZE              (1 << CALLSITE_HASH_BITS)
static struct cds_hlist_head callsite_table[CALLSITE_HASH_SIZE];

static void _ltt_event_destroy(struct ltt_event *event);
static void _ltt_wildcard_destroy(struct session_wildcard *sw);
static void _ltt_channel_destroy(struct ltt_channel *chan);
static int _ltt_event_unregister(struct ltt_event *event);
static
int _ltt_event_metadata_statedump(struct ltt_session *session,
                                  struct ltt_channel *chan,
                                  struct ltt_event *event);
static
int _ltt_callsite_metadata_statedump(struct ltt_session *session,
                                  struct lttng_callsite *callsite);

static
int _ltt_session_metadata_statedump(struct ltt_session *session);

int ltt_loglevel_match(const struct lttng_event_desc *desc,
                enum lttng_ust_loglevel_type req_type,
                int req_loglevel)
{
        int ev_loglevel;

        if (req_type == LTTNG_UST_LOGLEVEL_ALL)
                return 1;
        if (!desc->loglevel)
                ev_loglevel = TRACE_DEFAULT;
        else
                ev_loglevel = *(*desc->loglevel);
        switch (req_type) {
        case LTTNG_UST_LOGLEVEL_RANGE:
                if (ev_loglevel <= req_loglevel || req_loglevel == -1)
                        return 1;
                else
                        return 0;
        case LTTNG_UST_LOGLEVEL_SINGLE:
                if (ev_loglevel == req_loglevel || req_loglevel == -1)
                        return 1;
                else
                        return 0;
        case LTTNG_UST_LOGLEVEL_ALL:
        default:
                return 1;
        }
}

/*
 * Return wildcard for a given event name if the event name match the
 * one of the wildcards.
 * Must be called with ust lock held.
 * Returns NULL if not present.
 */
static
struct wildcard_entry *match_wildcard(const struct lttng_event_desc *desc)
{
        struct wildcard_entry *e;

        cds_list_for_each_entry(e, &wildcard_list, list) {
                /* If only contain '*' */
                if (strlen(e->name) == 1)
                        goto possible_match;
                /* Compare excluding final '*' */
                if (!strncmp(desc->name, e->name, strlen(e->name) - 1))
                        goto possible_match;
                continue;       /* goto next, no match */
        possible_match:
                if (ltt_loglevel_match(desc,
                                e->loglevel_type,
                                e->loglevel)) {
                        return e;
                }
                /* no match, loop to next */
        }
        return NULL;
}

/*
 * called at event creation if probe is missing.
 * called with session mutex held.
 */
static
int add_pending_probe(struct ltt_event *event, const char *name,
                enum lttng_ust_loglevel_type loglevel_type,
                int loglevel)
{
        struct cds_hlist_head *head;
        struct ust_pending_probe *e;
        size_t name_len = strlen(name) + 1;
        uint32_t hash;

        if (name_len > LTTNG_UST_SYM_NAME_LEN) {
                WARN("Truncating tracepoint name %s which exceeds size limits of %u chars", name, LTTNG_UST_SYM_NAME_LEN);
                name_len = LTTNG_UST_SYM_NAME_LEN;
        }
        hash = jhash(name, name_len - 1, 0);
        head = &pending_probe_table[hash & (PENDING_PROBE_HASH_SIZE - 1)];
        e = zmalloc(sizeof(struct ust_pending_probe) + name_len);
        if (!e)
                return -ENOMEM;
        memcpy(&e->name[0], name, name_len);
        e->name[name_len - 1] = '\0';
        e->loglevel_type = loglevel_type;
        e->loglevel = loglevel;
        cds_hlist_add_head(&e->node, head);
        e->event = event;
        event->pending_probe = e;
        return 0;
}

/*
 * remove a pending probe. called when at event teardown and when an
 * event is fixed (probe is loaded).
 * called with session mutex held.
 */
static
void remove_pending_probe(struct ust_pending_probe *e)
{
        if (!e)
                return;
        cds_hlist_del(&e->node);
        free(e);
}

/*
 * Called at library load: connect the probe on the events pending on
 * probe load.
 * called with session mutex held.
 */
int pending_probe_fix_events(const struct lttng_event_desc *desc)
{
        struct cds_hlist_head *head;
        struct cds_hlist_node *node, *p;
        struct ust_pending_probe *e;
        const char *name = desc->name;
        int ret = 0;
        struct lttng_ust_event event_param;
        size_t name_len = strlen(name) + 1;
        uint32_t hash;

        /* Wildcard */
        {
                struct wildcard_entry *wildcard;

                wildcard = match_wildcard(desc);
                if (strcmp(desc->name, "lttng_ust:metadata") && wildcard) {
                        struct session_wildcard *sw;

                        cds_list_for_each_entry(sw, &wildcard->session_list,
                                        session_list) {
                                struct ltt_event *ev;
                                int ret;

                                memcpy(&event_param, &sw->event_param,
                                                sizeof(event_param));
                                strncpy(event_param.name,
                                        desc->name,
                                        sizeof(event_param.name));
                                event_param.name[sizeof(event_param.name) - 1] = '\0';
                                /* create event */
                                ret = ltt_event_create(sw->chan,
                                        &event_param, &ev);
                                if (ret) {
                                        DBG("Error creating event");
                                        continue;
                                }
                                cds_list_add(&ev->wildcard_list,
                                        &sw->events);
                                lttng_filter_event_link_bytecode(ev,
                                        sw->filter_bytecode);
                        }
                }
        }

        if (name_len > LTTNG_UST_SYM_NAME_LEN) {
                WARN("Truncating tracepoint name %s which exceeds size limits of %u chars", name, LTTNG_UST_SYM_NAME_LEN);
                name_len = LTTNG_UST_SYM_NAME_LEN;
        }
        hash = jhash(name, name_len - 1, 0);
        head = &pending_probe_table[hash & (PENDING_PROBE_HASH_SIZE - 1)];
        cds_hlist_for_each_entry_safe(e, node, p, head, node) {
                struct ltt_event *event;
                struct ltt_channel *chan;

                if (!ltt_loglevel_match(desc,
                                e->loglevel_type,
                                e->loglevel)) {
                        continue;
                }
                if (strncmp(name, e->name, LTTNG_UST_SYM_NAME_LEN - 1)) {
                        continue;
                }
                event = e->event;
                chan = event->chan;
                assert(!event->desc);
                event->desc = desc;
                event->pending_probe = NULL;
                remove_pending_probe(e);
                ret |= __tracepoint_probe_register(name,
                                event->desc->probe_callback,
                                event, event->desc->signature);
                if (ret)
                        continue;
                event->id = chan->free_event_id++;
                ret |= _ltt_event_metadata_statedump(chan->session, chan,
                                event);
                lttng_filter_event_link_bytecode(event,
                        event->filter_bytecode);
        }
        return ret;
}

/*
 * Called at library load: add callsite information.
 * Takes the session mutex.
 * Should _not_ be called with tracepoint mutex held (would cause
 * deadlock with session mutex).
 */
int lttng_callsite_add(const struct tracepoint_callsite *tp_cs)
{
        struct cds_hlist_head *head;
        struct lttng_callsite *cs_node;
        struct ltt_session *session;
        uint32_t hash;
        int ret;

        ust_lock();
        /* hash by pointer value */
        hash = jhash(&tp_cs, sizeof(tp_cs), 0);
        head = &callsite_table[hash & (CALLSITE_HASH_SIZE - 1)];
        cs_node = zmalloc(sizeof(struct lttng_callsite));
        if (!cs_node)
                goto error_mem;
        cds_hlist_add_head(&cs_node->node, head);
        cs_node->tp_cs = tp_cs;

        /* print metadata for each session */
        cds_list_for_each_entry(session, &sessions, list) {
                ret = _ltt_callsite_metadata_statedump(session, cs_node);
                assert(!ret);
        }
        ust_unlock();
        return 0;

error_mem:
        ust_unlock();
        return -ENOMEM;
}

/*
 * Called at library unload: remove callsite information.
 * Takes the session mutex.
 * Should _not_ be called with tracepoint mutex held (would cause
 * deadlock with session mutex).
 */
int lttng_callsite_remove(const struct tracepoint_callsite *tp_cs)
{
        struct cds_hlist_head *head;
        struct cds_hlist_node *node;
        struct lttng_callsite *cs_node;
        uint32_t hash;
        int found = 0;

        ust_lock();
        /* hash by pointer value */
        hash = jhash(&tp_cs, sizeof(tp_cs), 0);
        head = &callsite_table[hash & (CALLSITE_HASH_SIZE - 1)];
        cds_hlist_for_each_entry(cs_node, node, head, node) {
                if (cs_node->tp_cs == tp_cs) {
                        found = 1;
                        break;
                }
        }
        if (!found)
                goto error;
        cds_hlist_del(&cs_node->node);
        free(cs_node);
        ust_unlock();
        return 0;

error:
        ust_unlock();
        return -ENOENT;
}

/*
 * Called with ust mutex held.
 */
static
int _callsite_session_metadata_statedump(struct ltt_session *session)
{
        int ret = 0;
        unsigned int i;

        for (i = 0; i < CALLSITE_HASH_SIZE; i++) {
                struct cds_hlist_head *head;
                struct cds_hlist_node *node;
                struct lttng_callsite *cs_node;

                head = &callsite_table[i];
                cds_hlist_for_each_entry(cs_node, node, head, node) {
                        ret = _ltt_callsite_metadata_statedump(session,
                                                        cs_node);
                        if (ret)
                                return ret;
                }
        }
        return ret;
}

void synchronize_trace(void)
{
        synchronize_rcu();
}

struct ltt_session *ltt_session_create(void)
{
        struct ltt_session *session;
        int ret;

        session = zmalloc(sizeof(struct ltt_session));
        if (!session)
                return NULL;
        CDS_INIT_LIST_HEAD(&session->chan);
        CDS_INIT_LIST_HEAD(&session->events);
        CDS_INIT_LIST_HEAD(&session->wildcards);
        ret = lttng_ust_uuid_generate(session->uuid);
        if (ret != 0) {
                session->uuid[0] = '\0';
        }
        cds_list_add(&session->list, &sessions);
        return session;
}

void ltt_session_destroy(struct ltt_session *session)
{
        struct ltt_channel *chan, *tmpchan;
        struct ltt_event *event, *tmpevent;
        struct session_wildcard *wildcard, *tmpwildcard;
        int ret;

        CMM_ACCESS_ONCE(session->active) = 0;
        cds_list_for_each_entry(event, &session->events, list) {
                ret = _ltt_event_unregister(event);
                WARN_ON(ret);
        }
        synchronize_trace();    /* Wait for in-flight events to complete */
        cds_list_for_each_entry_safe(wildcard, tmpwildcard, &session->wildcards, list)
                _ltt_wildcard_destroy(wildcard);
        cds_list_for_each_entry_safe(event, tmpevent, &session->events, list)
                _ltt_event_destroy(event);
        cds_list_for_each_entry_safe(chan, tmpchan, &session->chan, list)
                _ltt_channel_destroy(chan);
        cds_list_del(&session->list);
        free(session);
}

int ltt_session_enable(struct ltt_session *session)
{
        int ret = 0;
        struct ltt_channel *chan;

        if (session->active) {
                ret = -EBUSY;
                goto end;
        }

        /*
         * Snapshot the number of events per channel to know the type of header
         * we need to use.
         */
        cds_list_for_each_entry(chan, &session->chan, list) {
                if (chan->header_type)
                        continue;               /* don't change it if session stop/restart */
                if (chan->free_event_id < 31)
                        chan->header_type = 1;  /* compact */
                else
                        chan->header_type = 2;  /* large */
        }

        CMM_ACCESS_ONCE(session->active) = 1;
        CMM_ACCESS_ONCE(session->been_active) = 1;
        ret = _ltt_session_metadata_statedump(session);
        if (ret)
                CMM_ACCESS_ONCE(session->active) = 0;
end:
        return ret;
}

int ltt_session_disable(struct ltt_session *session)
{
        int ret = 0;

        if (!session->active) {
                ret = -EBUSY;
                goto end;
        }
        CMM_ACCESS_ONCE(session->active) = 0;
end:
        return ret;
}

int ltt_channel_enable(struct ltt_channel *channel)
{
        int old;

        if (channel == channel->session->metadata)
                return -EPERM;
        old = uatomic_xchg(&channel->enabled, 1);
        if (old)
                return -EEXIST;
        return 0;
}

int ltt_channel_disable(struct ltt_channel *channel)
{
        int old;

        if (channel == channel->session->metadata)
                return -EPERM;
        old = uatomic_xchg(&channel->enabled, 0);
        if (!old)
                return -EEXIST;
        return 0;
}

int ltt_event_enable(struct ltt_event *event)
{
        int old;

        if (event->chan == event->chan->session->metadata)
                return -EPERM;
        old = uatomic_xchg(&event->enabled, 1);
        if (old)
                return -EEXIST;
        return 0;
}

int ltt_event_disable(struct ltt_event *event)
{
        int old;

        if (event->chan == event->chan->session->metadata)
                return -EPERM;
        old = uatomic_xchg(&event->enabled, 0);
        if (!old)
                return -EEXIST;
        return 0;
}

struct ltt_channel *ltt_channel_create(struct ltt_session *session,
                                       const char *transport_name,
                                       void *buf_addr,
                                       size_t subbuf_size, size_t num_subbuf,
                                       unsigned int switch_timer_interval,
                                       unsigned int read_timer_interval,
                                       int **shm_fd, int **wait_fd,
                                       uint64_t **memory_map_size,
                                       struct ltt_channel *chan_priv_init)
{
        struct ltt_channel *chan = NULL;
        struct ltt_transport *transport;

        if (session->been_active)
                goto active;    /* Refuse to add channel to active session */
        transport = ltt_transport_find(transport_name);
        if (!transport) {
                DBG("LTTng transport %s not found\n",
                       transport_name);
                goto notransport;
        }
        chan_priv_init->id = session->free_chan_id++;
        chan_priv_init->session = session;
        /*
         * Note: the channel creation op already writes into the packet
         * headers. Therefore the "chan" information used as input
         * should be already accessible.
         */
        chan = transport->ops.channel_create(transport_name, buf_addr,
                        subbuf_size, num_subbuf, switch_timer_interval,
                        read_timer_interval, shm_fd, wait_fd,
                        memory_map_size, chan_priv_init);
        if (!chan)
                goto create_error;
        chan->enabled = 1;
        chan->ops = &transport->ops;
        cds_list_add(&chan->list, &session->chan);
        return chan;

create_error:
notransport:
active:
        return NULL;
}

/*
 * Only used internally at session destruction.
 */
static
void _ltt_channel_destroy(struct ltt_channel *chan)
{
        cds_list_del(&chan->list);
        lttng_destroy_context(chan->ctx);
        chan->ops->channel_destroy(chan);
}

/*
 * Supports event creation while tracing session is active.
 */
int ltt_event_create(struct ltt_channel *chan,
                struct lttng_ust_event *event_param,
                struct ltt_event **_event)
{
        const struct lttng_event_desc *desc = NULL;     /* silence gcc */
        struct ltt_event *event;
        int ret = 0;

        if (chan->used_event_id == -1U) {
                ret = -ENOMEM;
                goto full;
        }
        /*
         * This is O(n^2) (for each event, the loop is called at event
         * creation). Might require a hash if we have lots of events.
         */
        cds_list_for_each_entry(event, &chan->session->events, list) {
                if (event->desc && !strncmp(event->desc->name,
                                event_param->name,
                                LTTNG_UST_SYM_NAME_LEN - 1)) {
                        ret = -EEXIST;
                        goto exist;
                }
        }

        /*
         * Check if loglevel match. Refuse to connect event if not.
         */
        if (event_param->instrumentation == LTTNG_UST_TRACEPOINT) {
                desc = ltt_event_get(event_param->name);
                if (desc) {
                        if (!ltt_loglevel_match(desc,
                                        event_param->loglevel_type,
                                        event_param->loglevel)) {
                                ret = -EPERM;
                                goto no_loglevel_match;
                        }
                }
                /*
                 * If descriptor is not there, it will be added to
                 * pending probes.
                 */
        }
        event = zmalloc(sizeof(struct ltt_event));
        if (!event) {
                ret = -ENOMEM;
                goto cache_error;
        }
        event->chan = chan;
        /*
         * used_event_id counts the maximum number of event IDs that can
         * register if all probes register.
         */
        chan->used_event_id++;
        event->enabled = 1;
        event->instrumentation = event_param->instrumentation;
        /* Populate ltt_event structure before tracepoint registration. */
        cmm_smp_wmb();
        switch (event_param->instrumentation) {
        case LTTNG_UST_TRACEPOINT:
                event->desc = desc;
                if (event->desc) {
                        ret = __tracepoint_probe_register(event_param->name,
                                        event->desc->probe_callback,
                                        event, event->desc->signature);
                        if (ret)
                                goto register_error;
                        event->id = chan->free_event_id++;
                } else {
                        /*
                         * If the probe is not present, event->desc stays NULL,
                         * waiting for the probe to register, and the event->id
                         * stays unallocated.
                         */
                        ret = add_pending_probe(event, event_param->name,
                                        event_param->loglevel_type,
                                        event_param->loglevel);
                        if (ret)
                                goto add_pending_error;
                }
                break;
        default:
                WARN_ON_ONCE(1);
        }
        if (event->desc) {
                ret = _ltt_event_metadata_statedump(chan->session, chan, event);
                if (ret)
                        goto statedump_error;
        }
        cds_list_add(&event->list, &chan->session->events);
        *_event = event;
        return 0;

statedump_error:
        if (event->desc) {
                WARN_ON_ONCE(__tracepoint_probe_unregister(event_param->name,
                                        event->desc->probe_callback,
                                        event));
                ltt_event_put(event->desc);
        }
add_pending_error:
register_error:
        free(event);
cache_error:
no_loglevel_match:
exist:
full:
        return ret;
}

/*
 * Only used internally at session destruction.
 */
int _ltt_event_unregister(struct ltt_event *event)
{
        int ret = -EINVAL;

        switch (event->instrumentation) {
        case LTTNG_UST_TRACEPOINT:
                if (event->desc) {
                        ret = __tracepoint_probe_unregister(event->desc->name,
                                                          event->desc->probe_callback,
                                                          event);
                        if (ret)
                                return ret;
                } else {
                        remove_pending_probe(event->pending_probe);
                        ret = 0;
                }
                break;
        default:
                WARN_ON_ONCE(1);
        }
        return ret;
}

/*
 * Only used internally at session destruction.
 */
static
void _ltt_event_destroy(struct ltt_event *event)
{
        switch (event->instrumentation) {
        case LTTNG_UST_TRACEPOINT:
                if (event->desc) {
                        ltt_event_put(event->desc);
                }
                break;
        default:
                WARN_ON_ONCE(1);
        }
        cds_list_del(&event->list);
        lttng_destroy_context(event->ctx);
        free(event->filter_bytecode);
        free(event->filter_data);
        free(event);
}

/*
 * We have exclusive access to our metadata buffer (protected by the
 * ust_lock), so we can do racy operations such as looking for
 * remaining space left in packet and write, since mutual exclusion
 * protects us from concurrent writes.
 */
int lttng_metadata_printf(struct ltt_session *session,
                          const char *fmt, ...)
{
        struct lttng_ust_lib_ring_buffer_ctx ctx;
        struct ltt_channel *chan = session->metadata;
        char *str = NULL;
        int ret = 0, waitret;
        size_t len, reserve_len, pos;
        va_list ap;

        WARN_ON_ONCE(!CMM_ACCESS_ONCE(session->active));

        va_start(ap, fmt);
        ret = vasprintf(&str, fmt, ap);
        va_end(ap);
        if (ret < 0)
                return -ENOMEM;

        len = strlen(str);
        pos = 0;

        for (pos = 0; pos < len; pos += reserve_len) {
                reserve_len = min_t(size_t,
                                chan->ops->packet_avail_size(chan->chan, chan->handle),
                                len - pos);
                lib_ring_buffer_ctx_init(&ctx, chan->chan, NULL, reserve_len,
                                         sizeof(char), -1, chan->handle);
                /*
                 * We don't care about metadata buffer's records lost
                 * count, because we always retry here. Report error if
                 * we need to bail out after timeout or being
                 * interrupted.
                 */
                waitret = wait_cond_interruptible_timeout(
                        ({
                                ret = chan->ops->event_reserve(&ctx, 0);
                                ret != -ENOBUFS || !ret;
                        }),
                        LTTNG_METADATA_TIMEOUT_MSEC);
                if (waitret == -ETIMEDOUT || waitret == -EINTR || ret) {
                        DBG("LTTng: Failure to write metadata to buffers (%s)\n",
                                waitret == -EINTR ? "interrupted" :
                                        (ret == -ENOBUFS ? "timeout" : "I/O error"));
                        if (waitret == -EINTR)
                                ret = waitret;
                        goto end;
                }
                chan->ops->event_write(&ctx, &str[pos], reserve_len);
                chan->ops->event_commit(&ctx);
        }
end:
        free(str);
        return ret;
}

static
int _ltt_field_statedump(struct ltt_session *session,
                         const struct lttng_event_field *field)
{
        int ret = 0;

        if (field->nowrite)
                return 0;

        switch (field->type.atype) {
        case atype_integer:
                ret = lttng_metadata_printf(session,
                        "               integer { size = %u; align = %u; signed = %u; encoding = %s; base = %u;%s } _%s;\n",
                        field->type.u.basic.integer.size,
                        field->type.u.basic.integer.alignment,
                        field->type.u.basic.integer.signedness,
                        (field->type.u.basic.integer.encoding == lttng_encode_none)
                                ? "none"
                                : (field->type.u.basic.integer.encoding == lttng_encode_UTF8)
                                        ? "UTF8"
                                        : "ASCII",
                        field->type.u.basic.integer.base,
#if (BYTE_ORDER == BIG_ENDIAN)
                        field->type.u.basic.integer.reverse_byte_order ? " byte_order = le;" : "",
#else
                        field->type.u.basic.integer.reverse_byte_order ? " byte_order = be;" : "",
#endif
                        field->name);
                break;
        case atype_float:
                ret = lttng_metadata_printf(session,
                        "               floating_point { exp_dig = %u; mant_dig = %u; align = %u;%s } _%s;\n",
                        field->type.u.basic._float.exp_dig,
                        field->type.u.basic._float.mant_dig,
                        field->type.u.basic._float.alignment,
#if (BYTE_ORDER == BIG_ENDIAN)
                        field->type.u.basic.integer.reverse_byte_order ? " byte_order = le;" : "",
#else
                        field->type.u.basic.integer.reverse_byte_order ? " byte_order = be;" : "",
#endif
                        field->name);
                break;
        case atype_enum:
                ret = lttng_metadata_printf(session,
                        "               %s %s;\n",
                        field->type.u.basic.enumeration.name,
                        field->name);
                break;
        case atype_array:
        {
                const struct lttng_basic_type *elem_type;

                elem_type = &field->type.u.array.elem_type;
                ret = lttng_metadata_printf(session,
                        "               integer { size = %u; align = %u; signed = %u; encoding = %s; base = %u;%s } _%s[%u];\n",
                        elem_type->u.basic.integer.size,
                        elem_type->u.basic.integer.alignment,
                        elem_type->u.basic.integer.signedness,
                        (elem_type->u.basic.integer.encoding == lttng_encode_none)
                                ? "none"
                                : (elem_type->u.basic.integer.encoding == lttng_encode_UTF8)
                                        ? "UTF8"
                                        : "ASCII",
                        elem_type->u.basic.integer.base,
#if (BYTE_ORDER == BIG_ENDIAN)
                        elem_type->u.basic.integer.reverse_byte_order ? " byte_order = le;" : "",
#else
                        elem_type->u.basic.integer.reverse_byte_order ? " byte_order = be;" : "",
#endif
                        field->name, field->type.u.array.length);
                break;
        }
        case atype_sequence:
        {
                const struct lttng_basic_type *elem_type;
                const struct lttng_basic_type *length_type;

                elem_type = &field->type.u.sequence.elem_type;
                length_type = &field->type.u.sequence.length_type;
                ret = lttng_metadata_printf(session,
                        "               integer { size = %u; align = %u; signed = %u; encoding = %s; base = %u;%s } __%s_length;\n",
                        length_type->u.basic.integer.size,
                        (unsigned int) length_type->u.basic.integer.alignment,
                        length_type->u.basic.integer.signedness,
                        (length_type->u.basic.integer.encoding == lttng_encode_none)
                                ? "none"
                                : ((length_type->u.basic.integer.encoding == lttng_encode_UTF8)
                                        ? "UTF8"
                                        : "ASCII"),
                        length_type->u.basic.integer.base,
#if (BYTE_ORDER == BIG_ENDIAN)
                        length_type->u.basic.integer.reverse_byte_order ? " byte_order = le;" : "",
#else
                        length_type->u.basic.integer.reverse_byte_order ? " byte_order = be;" : "",
#endif
                        field->name);
                if (ret)
                        return ret;

                ret = lttng_metadata_printf(session,
                        "               integer { size = %u; align = %u; signed = %u; encoding = %s; base = %u;%s } _%s[ __%s_length ];\n",
                        elem_type->u.basic.integer.size,
                        (unsigned int) elem_type->u.basic.integer.alignment,
                        elem_type->u.basic.integer.signedness,
                        (elem_type->u.basic.integer.encoding == lttng_encode_none)
                                ? "none"
                                : ((elem_type->u.basic.integer.encoding == lttng_encode_UTF8)
                                        ? "UTF8"
                                        : "ASCII"),
                        elem_type->u.basic.integer.base,
#if (BYTE_ORDER == BIG_ENDIAN)
                        elem_type->u.basic.integer.reverse_byte_order ? " byte_order = le;" : "",
#else
                        elem_type->u.basic.integer.reverse_byte_order ? " byte_order = be;" : "",
#endif
                        field->name,
                        field->name);
                break;
        }

        case atype_string:
                /* Default encoding is UTF8 */
                ret = lttng_metadata_printf(session,
                        "               string%s _%s;\n",
                        field->type.u.basic.string.encoding == lttng_encode_ASCII ?
                                " { encoding = ASCII; }" : "",
                        field->name);
                break;
        default:
                WARN_ON_ONCE(1);
                return -EINVAL;
        }
        return ret;
}

static
int _ltt_context_metadata_statedump(struct ltt_session *session,
                                    struct lttng_ctx *ctx)
{
        int ret = 0;
        int i;

        if (!ctx)
                return 0;
        for (i = 0; i < ctx->nr_fields; i++) {
                const struct lttng_ctx_field *field = &ctx->fields[i];

                ret = _ltt_field_statedump(session, &field->event_field);
                if (ret)
                        return ret;
        }
        return ret;
}

static
int _ltt_fields_metadata_statedump(struct ltt_session *session,
                                   struct ltt_event *event)
{
        const struct lttng_event_desc *desc = event->desc;
        int ret = 0;
        int i;

        for (i = 0; i < desc->nr_fields; i++) {
                const struct lttng_event_field *field = &desc->fields[i];

                ret = _ltt_field_statedump(session, field);
                if (ret)
                        return ret;
        }
        return ret;
}

static
int _ltt_callsite_metadata_statedump(struct ltt_session *session,
                                  struct lttng_callsite *callsite)
{
        int ret = 0;

        if (!CMM_ACCESS_ONCE(session->active))
                return 0;

        ret = lttng_metadata_printf(session,
                "callsite {\n"
                "       name = \"%s\";\n"
                "       func = \"%s\";\n"
                "       ip = %p;\n"
                "       file = \"%s\";\n"
                "       line = %u;\n"
                "};\n\n",
                callsite->tp_cs->name,
                callsite->tp_cs->func,
                callsite->tp_cs->ip,
                callsite->tp_cs->file,
                callsite->tp_cs->lineno);
        if (ret)
                goto end;
end:
        return ret;
}

static
int _ltt_event_metadata_statedump(struct ltt_session *session,
                                  struct ltt_channel *chan,
                                  struct ltt_event *event)
{
        int ret = 0;
        int loglevel = TRACE_DEFAULT;

        if (event->metadata_dumped || !CMM_ACCESS_ONCE(session->active))
                return 0;
        if (chan == session->metadata)
                return 0;
        /*
         * Don't print events for which probe load is pending.
         */
        if (!event->desc)
                return 0;

        ret = lttng_metadata_printf(session,
                "event {\n"
                "       name = \"%s\";\n"
                "       id = %u;\n"
                "       stream_id = %u;\n",
                event->desc->name,
                event->id,
                event->chan->id);
        if (ret)
                goto end;

        if (event->desc->loglevel)
                loglevel = *(*event->desc->loglevel);

        ret = lttng_metadata_printf(session,
                "       loglevel = %d;\n",
                loglevel);
        if (ret)
                goto end;

        if (event->desc->u.ext.model_emf_uri) {
                ret = lttng_metadata_printf(session,
                        "       model.emf.uri = \"%s\";\n",
                        *(event->desc->u.ext.model_emf_uri));
                if (ret)
                        goto end;
        }

        if (event->ctx) {
                ret = lttng_metadata_printf(session,
                        "       context := struct {\n");
                if (ret)
                        goto end;
        }
        ret = _ltt_context_metadata_statedump(session, event->ctx);
        if (ret)
                goto end;
        if (event->ctx) {
                ret = lttng_metadata_printf(session,
                        "       };\n");
                if (ret)
                        goto end;
        }

        ret = lttng_metadata_printf(session,
                "       fields := struct {\n"
                );
        if (ret)
                goto end;

        ret = _ltt_fields_metadata_statedump(session, event);
        if (ret)
                goto end;

        /*
         * LTTng space reservation can only reserve multiples of the
         * byte size.
         */
        ret = lttng_metadata_printf(session,
                "       };\n"
                "};\n\n");
        if (ret)
                goto end;

        event->metadata_dumped = 1;
end:
        return ret;

}

static
int _ltt_channel_metadata_statedump(struct ltt_session *session,
                                    struct ltt_channel *chan)
{
        int ret = 0;

        if (chan->metadata_dumped || !CMM_ACCESS_ONCE(session->active))
                return 0;
        if (chan == session->metadata)
                return 0;

        WARN_ON_ONCE(!chan->header_type);
        ret = lttng_metadata_printf(session,
                "stream {\n"
                "       id = %u;\n"
                "       event.header := %s;\n"
                "       packet.context := struct packet_context;\n",
                chan->id,
                chan->header_type == 1 ? "struct event_header_compact" :
                        "struct event_header_large");
        if (ret)
                goto end;

        if (chan->ctx) {
                ret = lttng_metadata_printf(session,
                        "       event.context := struct {\n");
                if (ret)
                        goto end;
        }
        ret = _ltt_context_metadata_statedump(session, chan->ctx);
        if (ret)
                goto end;
        if (chan->ctx) {
                ret = lttng_metadata_printf(session,
                        "       };\n");
                if (ret)
                        goto end;
        }

        ret = lttng_metadata_printf(session,
                "};\n\n");

        chan->metadata_dumped = 1;
end:
        return ret;
}

static
int _ltt_stream_packet_context_declare(struct ltt_session *session)
{
        return lttng_metadata_printf(session,
                "struct packet_context {\n"
                "       uint64_clock_monotonic_t timestamp_begin;\n"
                "       uint64_clock_monotonic_t timestamp_end;\n"
                "       uint64_t content_size;\n"
                "       uint64_t packet_size;\n"
                "       unsigned long events_discarded;\n"
                "       uint32_t cpu_id;\n"
                "};\n\n"
                );
}

/*
 * Compact header:
 * id: range: 0 - 30.
 * id 31 is reserved to indicate an extended header.
 *
 * Large header:
 * id: range: 0 - 65534.
 * id 65535 is reserved to indicate an extended header.
 */
static
int _ltt_event_header_declare(struct ltt_session *session)
{
        return lttng_metadata_printf(session,
        "struct event_header_compact {\n"
        "       enum : uint5_t { compact = 0 ... 30, extended = 31 } id;\n"
        "       variant <id> {\n"
        "               struct {\n"
        "                       uint27_clock_monotonic_t timestamp;\n"
        "               } compact;\n"
        "               struct {\n"
        "                       uint32_t id;\n"
        "                       uint64_clock_monotonic_t timestamp;\n"
        "               } extended;\n"
        "       } v;\n"
        "} align(%u);\n"
        "\n"
        "struct event_header_large {\n"
        "       enum : uint16_t { compact = 0 ... 65534, extended = 65535 } id;\n"
        "       variant <id> {\n"
        "               struct {\n"
        "                       uint32_clock_monotonic_t timestamp;\n"
        "               } compact;\n"
        "               struct {\n"
        "                       uint32_t id;\n"
        "                       uint64_clock_monotonic_t timestamp;\n"
        "               } extended;\n"
        "       } v;\n"
        "} align(%u);\n\n",
        lttng_alignof(uint32_t) * CHAR_BIT,
        lttng_alignof(uint16_t) * CHAR_BIT
        );
}

/*
 * Approximation of NTP time of day to clock monotonic correlation,
 * taken at start of trace.
 * Yes, this is only an approximation. Yes, we can (and will) do better
 * in future versions.
 */
static
uint64_t measure_clock_offset(void)
{
        uint64_t offset, monotonic[2], realtime;
        struct timespec rts = { 0, 0 };
        int ret;

        monotonic[0] = trace_clock_read64();
        ret = clock_gettime(CLOCK_REALTIME, &rts);      
        if (ret < 0)
                return 0;
        monotonic[1] = trace_clock_read64();
        offset = (monotonic[0] + monotonic[1]) >> 1;
        realtime = (uint64_t) rts.tv_sec * 1000000000ULL;
        realtime += rts.tv_nsec;
        offset = realtime - offset;
        return offset;
}

/*
 * Output metadata into this session's metadata buffers.
 */
static
int _ltt_session_metadata_statedump(struct ltt_session *session)
{
        unsigned char *uuid_c = session->uuid;
        char uuid_s[LTTNG_UST_UUID_STR_LEN],
                clock_uuid_s[LTTNG_UST_UUID_STR_LEN];
        struct ltt_channel *chan;
        struct ltt_event *event;
        int ret = 0;
        char procname[LTTNG_UST_PROCNAME_LEN] = "";
        char hostname[HOST_NAME_MAX];

        if (!CMM_ACCESS_ONCE(session->active))
                return 0;
        if (session->metadata_dumped)
                goto skip_session;
        if (!session->metadata) {
                DBG("LTTng: attempt to start tracing, but metadata channel is not found. Operation abort.\n");
                return -EPERM;
        }

        snprintf(uuid_s, sizeof(uuid_s),
                "%02x%02x%02x%02x-%02x%02x-%02x%02x-%02x%02x-%02x%02x%02x%02x%02x%02x",
                uuid_c[0], uuid_c[1], uuid_c[2], uuid_c[3],
                uuid_c[4], uuid_c[5], uuid_c[6], uuid_c[7],
                uuid_c[8], uuid_c[9], uuid_c[10], uuid_c[11],
                uuid_c[12], uuid_c[13], uuid_c[14], uuid_c[15]);

        ret = lttng_metadata_printf(session,
                "typealias integer { size = 8; align = %u; signed = false; } := uint8_t;\n"
                "typealias integer { size = 16; align = %u; signed = false; } := uint16_t;\n"
                "typealias integer { size = 32; align = %u; signed = false; } := uint32_t;\n"
                "typealias integer { size = 64; align = %u; signed = false; } := uint64_t;\n"
                "typealias integer { size = %u; align = %u; signed = false; } := unsigned long;\n"
                "typealias integer { size = 5; align = 1; signed = false; } := uint5_t;\n"
                "typealias integer { size = 27; align = 1; signed = false; } := uint27_t;\n"
                "\n"
                "trace {\n"
                "       major = %u;\n"
                "       minor = %u;\n"
                "       uuid = \"%s\";\n"
                "       byte_order = %s;\n"
                "       packet.header := struct {\n"
                "               uint32_t magic;\n"
                "               uint8_t  uuid[16];\n"
                "               uint32_t stream_id;\n"
                "       };\n"
                "};\n\n",
                lttng_alignof(uint8_t) * CHAR_BIT,
                lttng_alignof(uint16_t) * CHAR_BIT,
                lttng_alignof(uint32_t) * CHAR_BIT,
                lttng_alignof(uint64_t) * CHAR_BIT,
                sizeof(unsigned long) * CHAR_BIT,
                lttng_alignof(unsigned long) * CHAR_BIT,
                CTF_SPEC_MAJOR,
                CTF_SPEC_MINOR,
                uuid_s,
#if (BYTE_ORDER == BIG_ENDIAN)
                "be"
#else
                "le"
#endif
                );
        if (ret)
                goto end;

        /* ignore error, just use empty string if error. */
        hostname[0] = '\0';
        ret = gethostname(hostname, sizeof(hostname));
        if (ret && errno == ENAMETOOLONG)
                hostname[HOST_NAME_MAX - 1] = '\0';
        lttng_ust_getprocname(procname);
        procname[LTTNG_UST_PROCNAME_LEN - 1] = '\0';
        ret = lttng_metadata_printf(session,
                "env {\n"
                "       hostname = \"%s\";\n"
                "       vpid = %d;\n"
                "       procname = \"%s\";\n"
                "       domain = \"ust\";\n"
                "       tracer_name = \"lttng-ust\";\n"
                "       tracer_major = %u;\n"
                "       tracer_minor = %u;\n"
                "       tracer_patchlevel = %u;\n"
                "};\n\n",
                hostname,
                (int) getpid(),
                procname,
                LTTNG_UST_MAJOR_VERSION,
                LTTNG_UST_MINOR_VERSION,
                LTTNG_UST_PATCHLEVEL_VERSION
                );
        if (ret)
                goto end;

        ret = lttng_metadata_printf(session,
                "clock {\n"
                "       name = %s;\n",
                "monotonic"
                );
        if (ret)
                goto end;

        if (!trace_clock_uuid(clock_uuid_s)) {
                ret = lttng_metadata_printf(session,
                        "       uuid = \"%s\";\n",
                        clock_uuid_s
                        );
                if (ret)
                        goto end;
        }

        ret = lttng_metadata_printf(session,
                "       description = \"Monotonic Clock\";\n"
                "       freq = %" PRIu64 "; /* Frequency, in Hz */\n"
                "       /* clock value offset from Epoch is: offset * (1/freq) */\n"
                "       offset = %" PRIu64 ";\n"
                "};\n\n",
                trace_clock_freq(),
                measure_clock_offset()
                );
        if (ret)
                goto end;

        ret = lttng_metadata_printf(session,
                "typealias integer {\n"
                "       size = 27; align = 1; signed = false;\n"
                "       map = clock.monotonic.value;\n"
                "} := uint27_clock_monotonic_t;\n"
                "\n"
                "typealias integer {\n"
                "       size = 32; align = %u; signed = false;\n"
                "       map = clock.monotonic.value;\n"
                "} := uint32_clock_monotonic_t;\n"
                "\n"
                "typealias integer {\n"
                "       size = 64; align = %u; signed = false;\n"
                "       map = clock.monotonic.value;\n"
                "} := uint64_clock_monotonic_t;\n\n",
                lttng_alignof(uint32_t) * CHAR_BIT,
                lttng_alignof(uint64_t) * CHAR_BIT
                );
        if (ret)
                goto end;

        ret = _ltt_stream_packet_context_declare(session);
        if (ret)
                goto end;

        ret = _ltt_event_header_declare(session);
        if (ret)
                goto end;
        ret = _callsite_session_metadata_statedump(session);
        if (ret)
                goto end;

skip_session:
        cds_list_for_each_entry(chan, &session->chan, list) {
                ret = _ltt_channel_metadata_statedump(session, chan);
                if (ret)
                        goto end;
        }

        cds_list_for_each_entry(event, &session->events, list) {
                ret = _ltt_event_metadata_statedump(session, event->chan, event);
                if (ret)
                        goto end;
        }
        session->metadata_dumped = 1;
end:
        return ret;
}

void lttng_ust_events_exit(void)
{
        struct ltt_session *session, *tmpsession;

        cds_list_for_each_entry_safe(session, tmpsession, &sessions, list)
                ltt_session_destroy(session);
}

/* WILDCARDS */

static
int wildcard_same_loglevel(struct wildcard_entry *e,
        enum lttng_ust_loglevel_type loglevel_type,
        int loglevel)
{
        if (e->loglevel_type == loglevel_type && e->loglevel == loglevel)
                return 1;
        else
                return 0;
}

#if 0
static
int wildcard_is_within(struct wildcard_entry *e,
        enum lttng_ust_loglevel_type loglevel_type,
        int loglevel)
{
        if (e->loglevel_type == LTTNG_UST_LOGLEVEL_ALL
                        || e->loglevel == -1)
                return 1;
        switch (e->loglevel_type) {
        case LTTNG_UST_LOGLEVEL_RANGE:
                switch (loglevel_type) {
                case LTTNG_UST_LOGLEVEL_RANGE:
                        if (e->loglevel >= loglevel)
                                return 1;
                        else
                                return 0;
                case LTTNG_UST_LOGLEVEL_SINGLE:
                        if (e->loglevel <= 0 && loglevel == 0)
                                return 1;
                        else
                                return 0;
                }
        case LTTNG_UST_LOGLEVEL_SINGLE:
                switch (loglevel_type) {
                case LTTNG_UST_LOGLEVEL_RANGE:
                        if (loglevel <= 0)
                                return 1;
                        else
                                return 0;
                case LTTNG_UST_LOGLEVEL_SINGLE:
                        if (e->loglevel == loglevel)
                                return 1;
                        else
                                return 0;
                }
        }
}
#endif

/*
 * Add the wildcard to the wildcard list. Must be called with
 * ust lock held.
 */
static
struct session_wildcard *add_wildcard(struct ltt_channel *chan,
        struct lttng_ust_event *event_param)
{
        struct wildcard_entry *e;
        struct session_wildcard *sw;
        size_t name_len = strlen(event_param->name) + 1;
        int found = 0;

        /*
         * Try to find global wildcard entry. Given that this is shared
         * across all sessions, we need to check for exact loglevel
         * match, not just whether contained within the existing ones.
         */
        cds_list_for_each_entry(e, &wildcard_list, list) {
                if (!strncmp(event_param->name, e->name,
                                LTTNG_UST_SYM_NAME_LEN - 1)) {
                        if (wildcard_same_loglevel(e,
                                        event_param->loglevel_type,
                                        event_param->loglevel)) {
                                found = 1;
                                break;
                        }
                }
        }

        if (!found) {
                /*
                 * Create global wildcard entry if not found. Using
                 * zmalloc here to allocate a variable length element.
                 * Could cause some memory fragmentation if overused.
                 */
                e = zmalloc(sizeof(struct wildcard_entry) + name_len);
                if (!e)
                        return ERR_PTR(-ENOMEM);
                memcpy(&e->name[0], event_param->name, name_len);
                e->loglevel_type = event_param->loglevel_type;
                e->loglevel = event_param->loglevel;
                cds_list_add(&e->list, &wildcard_list);
                CDS_INIT_LIST_HEAD(&e->session_list);
        }

        /* session wildcard */
        cds_list_for_each_entry(sw, &e->session_list, session_list) {
                if (chan == sw->chan) {
                        DBG("wildcard %s busy for this channel",
                                event_param->name);
                        return ERR_PTR(-EEXIST);        /* Already there */
                }
        }
        sw = zmalloc(sizeof(struct session_wildcard));
        if (!sw)
                return ERR_PTR(-ENOMEM);
        sw->chan = chan;
        sw->enabled = 1;
        memcpy(&sw->event_param, event_param, sizeof(sw->event_param));
        sw->event_param.instrumentation = LTTNG_UST_TRACEPOINT;
        sw->event_param.loglevel_type = event_param->loglevel_type;
        sw->event_param.loglevel = event_param->loglevel;
        CDS_INIT_LIST_HEAD(&sw->events);
        cds_list_add(&sw->list, &chan->session->wildcards);
        cds_list_add(&sw->session_list, &e->session_list);
        sw->entry = e;
        ltt_probes_create_wildcard_events(e, sw);
        return sw;
}

/*
 * Remove the wildcard from the wildcard list. Must be called with
 * ust_lock held. Only called at session teardown.
 */
static
void _remove_wildcard(struct session_wildcard *wildcard)
{
        struct ltt_event *ev, *tmp;

        /*
         * Just remove the events owned (for enable/disable) by this
         * wildcard from the list. The session teardown will take care
         * of freeing the event memory.
         */
        cds_list_for_each_entry_safe(ev, tmp, &wildcard->events,
                        wildcard_list) {
                cds_list_del(&ev->wildcard_list);
        }
        cds_list_del(&wildcard->session_list);
        cds_list_del(&wildcard->list);
        if (cds_list_empty(&wildcard->entry->session_list)) {
                cds_list_del(&wildcard->entry->list);
                free(wildcard->entry);
        }
        free(wildcard->filter_bytecode);
        free(wildcard);
}

int ltt_wildcard_create(struct ltt_channel *chan,
        struct lttng_ust_event *event_param,
        struct session_wildcard **_sw)
{
        struct session_wildcard *sw;

        sw = add_wildcard(chan, event_param);
        if (!sw || IS_ERR(sw)) {
                return PTR_ERR(sw);
        }
        *_sw = sw;
        return 0;
}

static
void _ltt_wildcard_destroy(struct session_wildcard *sw)
{
        _remove_wildcard(sw);
}

int ltt_wildcard_enable(struct session_wildcard *wildcard)
{
        struct ltt_event *ev;
        int ret;

        if (wildcard->enabled)
                return -EEXIST;
        cds_list_for_each_entry(ev, &wildcard->events, wildcard_list) {
                ret = ltt_event_enable(ev);
                if (ret) {
                        DBG("Error: enable error.\n");
                        return ret;
                }
        }
        wildcard->enabled = 1;
        return 0;
}

int ltt_wildcard_disable(struct session_wildcard *wildcard)
{
        struct ltt_event *ev;
        int ret;

        if (!wildcard->enabled)
                return -EEXIST;
        cds_list_for_each_entry(ev, &wildcard->events, wildcard_list) {
                ret = ltt_event_disable(ev);
                if (ret) {
                        DBG("Error: disable error.\n");
                        return ret;
                }
        }
        wildcard->enabled = 0;
        return 0;
}

/*
 * Take the TLS "fault" in libuuid if dlopen'd, which can take the
 * dynamic linker mutex, outside of the UST lock, since the UST lock is
 * taken in constructors, which are called with dynamic linker mutex
 * held.
 */
void lttng_fixup_event_tls(void)
{
        unsigned char uuid[LTTNG_UST_UUID_STR_LEN];

        (void) lttng_ust_uuid_generate(uuid);
}