Network streaming support

[lttng-tools.git] / src / bin / lttng-sessiond / main.c

/*
 * Copyright (C) 2011 - David Goulet <david.goulet@polymtl.ca>
 *                      Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License, version 2 only,
 * as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

#define _GNU_SOURCE
#include <getopt.h>
#include <grp.h>
#include <limits.h>
#include <pthread.h>
#include <semaphore.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/mount.h>
#include <sys/resource.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <urcu/uatomic.h>
#include <unistd.h>
#include <config.h>

#include <common/common.h>
#include <common/compat/poll.h>
#include <common/compat/socket.h>
#include <common/defaults.h>
#include <common/kernel-consumer/kernel-consumer.h>
#include <common/futex.h>
#include <common/relayd/relayd.h>

#include "lttng-sessiond.h"
#include "channel.h"
#include "consumer.h"
#include "context.h"
#include "event.h"
#include "kernel.h"
#include "kernel-consumer.h"
#include "modprobe.h"
#include "shm.h"
#include "ust-ctl.h"
#include "ust-consumer.h"
#include "utils.h"
#include "fd-limit.h"

#define CONSUMERD_FILE  "lttng-consumerd"

/* Const values */
const char default_home_dir[] = DEFAULT_HOME_DIR;
const char default_tracing_group[] = DEFAULT_TRACING_GROUP;
const char default_ust_sock_dir[] = DEFAULT_UST_SOCK_DIR;
const char default_global_apps_pipe[] = DEFAULT_GLOBAL_APPS_PIPE;

const char *progname;
const char *opt_tracing_group;
static int opt_sig_parent;
static int opt_verbose_consumer;
static int opt_daemon;
static int opt_no_kernel;
static int is_root;                     /* Set to 1 if the daemon is running as root */
static pid_t ppid;          /* Parent PID for --sig-parent option */
static char *rundir;

/* Consumer daemon specific control data */
static struct consumer_data kconsumer_data = {
        .type = LTTNG_CONSUMER_KERNEL,
        .err_unix_sock_path = DEFAULT_KCONSUMERD_ERR_SOCK_PATH,
        .cmd_unix_sock_path = DEFAULT_KCONSUMERD_CMD_SOCK_PATH,
        .err_sock = -1,
        .cmd_sock = -1,
};
static struct consumer_data ustconsumer64_data = {
        .type = LTTNG_CONSUMER64_UST,
        .err_unix_sock_path = DEFAULT_USTCONSUMERD64_ERR_SOCK_PATH,
        .cmd_unix_sock_path = DEFAULT_USTCONSUMERD64_CMD_SOCK_PATH,
        .err_sock = -1,
        .cmd_sock = -1,
};
static struct consumer_data ustconsumer32_data = {
        .type = LTTNG_CONSUMER32_UST,
        .err_unix_sock_path = DEFAULT_USTCONSUMERD32_ERR_SOCK_PATH,
        .cmd_unix_sock_path = DEFAULT_USTCONSUMERD32_CMD_SOCK_PATH,
        .err_sock = -1,
        .cmd_sock = -1,
};

static int dispatch_thread_exit;

/* Global application Unix socket path */
static char apps_unix_sock_path[PATH_MAX];
/* Global client Unix socket path */
static char client_unix_sock_path[PATH_MAX];
/* global wait shm path for UST */
static char wait_shm_path[PATH_MAX];

/* Sockets and FDs */
static int client_sock = -1;
static int apps_sock = -1;
static int kernel_tracer_fd = -1;
static int kernel_poll_pipe[2] = { -1, -1 };

/*
 * Quit pipe for all threads. This permits a single cancellation point
 * for all threads when receiving an event on the pipe.
 */
static int thread_quit_pipe[2] = { -1, -1 };

/*
 * This pipe is used to inform the thread managing application communication
 * that a command is queued and ready to be processed.
 */
static int apps_cmd_pipe[2] = { -1, -1 };

/* Pthread, Mutexes and Semaphores */
static pthread_t apps_thread;
static pthread_t reg_apps_thread;
static pthread_t client_thread;
static pthread_t kernel_thread;
static pthread_t dispatch_thread;

/*
 * UST registration command queue. This queue is tied with a futex and uses a N
 * wakers / 1 waiter implemented and detailed in futex.c/.h
 *
 * The thread_manage_apps and thread_dispatch_ust_registration interact with
 * this queue and the wait/wake scheme.
 */
static struct ust_cmd_queue ust_cmd_queue;

/*
 * Pointer initialized before thread creation.
 *
 * This points to the tracing session list containing the session count and a
 * mutex lock. The lock MUST be taken if you iterate over the list. The lock
 * MUST NOT be taken if you call a public function in session.c.
 *
 * The lock is nested inside the structure: session_list_ptr->lock. Please use
 * session_lock_list and session_unlock_list for lock acquisition.
 */
static struct ltt_session_list *session_list_ptr;

int ust_consumerd64_fd = -1;
int ust_consumerd32_fd = -1;

static const char *consumerd32_bin = CONFIG_CONSUMERD32_BIN;
static const char *consumerd64_bin = CONFIG_CONSUMERD64_BIN;
static const char *consumerd32_libdir = CONFIG_CONSUMERD32_LIBDIR;
static const char *consumerd64_libdir = CONFIG_CONSUMERD64_LIBDIR;

/*
 * Consumer daemon state which is changed when spawning it, killing it or in
 * case of a fatal error.
 */
enum consumerd_state {
        CONSUMER_STARTED = 1,
        CONSUMER_STOPPED = 2,
        CONSUMER_ERROR   = 3,
};

/*
 * This consumer daemon state is used to validate if a client command will be
 * able to reach the consumer. If not, the client is informed. For instance,
 * doing a "lttng start" when the consumer state is set to ERROR will return an
 * error to the client.
 *
 * The following example shows a possible race condition of this scheme:
 *
 * consumer thread error happens
 *                                    client cmd arrives
 *                                    client cmd checks state -> still OK
 * consumer thread exit, sets error
 *                                    client cmd try to talk to consumer
 *                                    ...
 *
 * However, since the consumer is a different daemon, we have no way of making
 * sure the command will reach it safely even with this state flag. This is why
 * we consider that up to the state validation during command processing, the
 * command is safe. After that, we can not guarantee the correctness of the
 * client request vis-a-vis the consumer.
 */
static enum consumerd_state ust_consumerd_state;
static enum consumerd_state kernel_consumerd_state;

/*
 * Used to keep a unique index for each relayd socket created where this value
 * is associated with streams on the consumer so it can match the right relayd
 * to send to.
 *
 * This value should be incremented atomically for safety purposes and future
 * possible concurrent access.
 */
static unsigned int relayd_net_seq_idx;

static
void setup_consumerd_path(void)
{
        const char *bin, *libdir;

        /*
         * Allow INSTALL_BIN_PATH to be used as a target path for the
         * native architecture size consumer if CONFIG_CONSUMER*_PATH
         * has not been defined.
         */
#if (CAA_BITS_PER_LONG == 32)
        if (!consumerd32_bin[0]) {
                consumerd32_bin = INSTALL_BIN_PATH "/" CONSUMERD_FILE;
        }
        if (!consumerd32_libdir[0]) {
                consumerd32_libdir = INSTALL_LIB_PATH;
        }
#elif (CAA_BITS_PER_LONG == 64)
        if (!consumerd64_bin[0]) {
                consumerd64_bin = INSTALL_BIN_PATH "/" CONSUMERD_FILE;
        }
        if (!consumerd64_libdir[0]) {
                consumerd64_libdir = INSTALL_LIB_PATH;
        }
#else
#error "Unknown bitness"
#endif

        /*
         * runtime env. var. overrides the build default.
         */
        bin = getenv("LTTNG_CONSUMERD32_BIN");
        if (bin) {
                consumerd32_bin = bin;
        }
        bin = getenv("LTTNG_CONSUMERD64_BIN");
        if (bin) {
                consumerd64_bin = bin;
        }
        libdir = getenv("LTTNG_CONSUMERD32_LIBDIR");
        if (libdir) {
                consumerd32_libdir = libdir;
        }
        libdir = getenv("LTTNG_CONSUMERD64_LIBDIR");
        if (libdir) {
                consumerd64_libdir = libdir;
        }
}

/*
 * Create a poll set with O_CLOEXEC and add the thread quit pipe to the set.
 */
static int create_thread_poll_set(struct lttng_poll_event *events,
                unsigned int size)
{
        int ret;

        if (events == NULL || size == 0) {
                ret = -1;
                goto error;
        }

        ret = lttng_poll_create(events, size, LTTNG_CLOEXEC);
        if (ret < 0) {
                goto error;
        }

        /* Add quit pipe */
        ret = lttng_poll_add(events, thread_quit_pipe[0], LPOLLIN);
        if (ret < 0) {
                goto error;
        }

        return 0;

error:
        return ret;
}

/*
 * Check if the thread quit pipe was triggered.
 *
 * Return 1 if it was triggered else 0;
 */
static int check_thread_quit_pipe(int fd, uint32_t events)
{
        if (fd == thread_quit_pipe[0] && (events & LPOLLIN)) {
                return 1;
        }

        return 0;
}

/*
 * Return group ID of the tracing group or -1 if not found.
 */
static gid_t allowed_group(void)
{
        struct group *grp;

        if (opt_tracing_group) {
                grp = getgrnam(opt_tracing_group);
        } else {
                grp = getgrnam(default_tracing_group);
        }
        if (!grp) {
                return -1;
        } else {
                return grp->gr_gid;
        }
}

/*
 * Init thread quit pipe.
 *
 * Return -1 on error or 0 if all pipes are created.
 */
static int init_thread_quit_pipe(void)
{
        int ret, i;

        ret = pipe(thread_quit_pipe);
        if (ret < 0) {
                PERROR("thread quit pipe");
                goto error;
        }

        for (i = 0; i < 2; i++) {
                ret = fcntl(thread_quit_pipe[i], F_SETFD, FD_CLOEXEC);
                if (ret < 0) {
                        PERROR("fcntl");
                        goto error;
                }
        }

error:
        return ret;
}

/*
 * Complete teardown of a kernel session. This free all data structure related
 * to a kernel session and update counter.
 */
static void teardown_kernel_session(struct ltt_session *session)
{
        if (!session->kernel_session) {
                DBG3("No kernel session when tearing down session");
                return;
        }

        DBG("Tearing down kernel session");

        /*
         * If a custom kernel consumer was registered, close the socket before
         * tearing down the complete kernel session structure
         */
        if (kconsumer_data.cmd_sock >= 0 &&
                        session->kernel_session->consumer_fd != kconsumer_data.cmd_sock) {
                lttcomm_close_unix_sock(session->kernel_session->consumer_fd);
        }

        trace_kernel_destroy_session(session->kernel_session);
}

/*
 * Complete teardown of all UST sessions. This will free everything on his path
 * and destroy the core essence of all ust sessions :)
 */
static void teardown_ust_session(struct ltt_session *session)
{
        int ret;

        if (!session->ust_session) {
                DBG3("No UST session when tearing down session");
                return;
        }

        DBG("Tearing down UST session(s)");

        ret = ust_app_destroy_trace_all(session->ust_session);
        if (ret) {
                ERR("Error in ust_app_destroy_trace_all");
        }

        trace_ust_destroy_session(session->ust_session);
}

/*
 * Stop all threads by closing the thread quit pipe.
 */
static void stop_threads(void)
{
        int ret;

        /* Stopping all threads */
        DBG("Terminating all threads");
        ret = notify_thread_pipe(thread_quit_pipe[1]);
        if (ret < 0) {
                ERR("write error on thread quit pipe");
        }

        /* Dispatch thread */
        dispatch_thread_exit = 1;
        futex_nto1_wake(&ust_cmd_queue.futex);
}

/*
 * Cleanup the daemon
 */
static void cleanup(void)
{
        int ret;
        char *cmd;
        struct ltt_session *sess, *stmp;

        DBG("Cleaning up");

        DBG("Removing %s directory", rundir);
        ret = asprintf(&cmd, "rm -rf %s", rundir);
        if (ret < 0) {
                ERR("asprintf failed. Something is really wrong!");
        }

        /* Remove lttng run directory */
        ret = system(cmd);
        if (ret < 0) {
                ERR("Unable to clean %s", rundir);
        }
        free(cmd);

        DBG("Cleaning up all sessions");

        /* Destroy session list mutex */
        if (session_list_ptr != NULL) {
                pthread_mutex_destroy(&session_list_ptr->lock);

                /* Cleanup ALL session */
                cds_list_for_each_entry_safe(sess, stmp,
                                &session_list_ptr->head, list) {
                        teardown_kernel_session(sess);
                        teardown_ust_session(sess);
                        free(sess);
                }
        }

        DBG("Closing all UST sockets");
        ust_app_clean_list();

        pthread_mutex_destroy(&kconsumer_data.pid_mutex);

        if (is_root && !opt_no_kernel) {
                DBG2("Closing kernel fd");
                if (kernel_tracer_fd >= 0) {
                        ret = close(kernel_tracer_fd);
                        if (ret) {
                                PERROR("close");
                        }
                }
                DBG("Unloading kernel modules");
                modprobe_remove_lttng_all();
        }
        utils_close_pipe(kernel_poll_pipe);
        utils_close_pipe(thread_quit_pipe);
        utils_close_pipe(apps_cmd_pipe);

        /* <fun> */
        DBG("%c[%d;%dm*** assert failed :-) *** ==> %c[%dm%c[%d;%dm"
                        "Matthew, BEET driven development works!%c[%dm",
                        27, 1, 31, 27, 0, 27, 1, 33, 27, 0);
        /* </fun> */
}

/*
 * Send data on a unix socket using the liblttsessiondcomm API.
 *
 * Return lttcomm error code.
 */
static int send_unix_sock(int sock, void *buf, size_t len)
{
        /* Check valid length */
        if (len <= 0) {
                return -1;
        }

        return lttcomm_send_unix_sock(sock, buf, len);
}

/*
 * Free memory of a command context structure.
 */
static void clean_command_ctx(struct command_ctx **cmd_ctx)
{
        DBG("Clean command context structure");
        if (*cmd_ctx) {
                if ((*cmd_ctx)->llm) {
                        free((*cmd_ctx)->llm);
                }
                if ((*cmd_ctx)->lsm) {
                        free((*cmd_ctx)->lsm);
                }
                free(*cmd_ctx);
                *cmd_ctx = NULL;
        }
}

/*
 * Notify UST applications using the shm mmap futex.
 */
static int notify_ust_apps(int active)
{
        char *wait_shm_mmap;

        DBG("Notifying applications of session daemon state: %d", active);

        /* See shm.c for this call implying mmap, shm and futex calls */
        wait_shm_mmap = shm_ust_get_mmap(wait_shm_path, is_root);
        if (wait_shm_mmap == NULL) {
                goto error;
        }

        /* Wake waiting process */
        futex_wait_update((int32_t *) wait_shm_mmap, active);

        /* Apps notified successfully */
        return 0;

error:
        return -1;
}

/*
 * Setup the outgoing data buffer for the response (llm) by allocating the
 * right amount of memory and copying the original information from the lsm
 * structure.
 *
 * Return total size of the buffer pointed by buf.
 */
static int setup_lttng_msg(struct command_ctx *cmd_ctx, size_t size)
{
        int ret, buf_size;

        buf_size = size;

        cmd_ctx->llm = zmalloc(sizeof(struct lttcomm_lttng_msg) + buf_size);
        if (cmd_ctx->llm == NULL) {
                PERROR("zmalloc");
                ret = -ENOMEM;
                goto error;
        }

        /* Copy common data */
        cmd_ctx->llm->cmd_type = cmd_ctx->lsm->cmd_type;
        cmd_ctx->llm->pid = cmd_ctx->lsm->domain.attr.pid;

        cmd_ctx->llm->data_size = size;
        cmd_ctx->lttng_msg_size = sizeof(struct lttcomm_lttng_msg) + buf_size;

        return buf_size;

error:
        return ret;
}

/*
 * Update the kernel poll set of all channel fd available over all tracing
 * session. Add the wakeup pipe at the end of the set.
 */
static int update_kernel_poll(struct lttng_poll_event *events)
{
        int ret;
        struct ltt_session *session;
        struct ltt_kernel_channel *channel;

        DBG("Updating kernel poll set");

        session_lock_list();
        cds_list_for_each_entry(session, &session_list_ptr->head, list) {
                session_lock(session);
                if (session->kernel_session == NULL) {
                        session_unlock(session);
                        continue;
                }

                cds_list_for_each_entry(channel,
                                &session->kernel_session->channel_list.head, list) {
                        /* Add channel fd to the kernel poll set */
                        ret = lttng_poll_add(events, channel->fd, LPOLLIN | LPOLLRDNORM);
                        if (ret < 0) {
                                session_unlock(session);
                                goto error;
                        }
                        DBG("Channel fd %d added to kernel set", channel->fd);
                }
                session_unlock(session);
        }
        session_unlock_list();

        return 0;

error:
        session_unlock_list();
        return -1;
}

/*
 * Find the channel fd from 'fd' over all tracing session. When found, check
 * for new channel stream and send those stream fds to the kernel consumer.
 *
 * Useful for CPU hotplug feature.
 */
static int update_kernel_stream(struct consumer_data *consumer_data, int fd)
{
        int ret = 0;
        struct ltt_session *session;
        struct ltt_kernel_channel *channel;

        DBG("Updating kernel streams for channel fd %d", fd);

        session_lock_list();
        cds_list_for_each_entry(session, &session_list_ptr->head, list) {
                session_lock(session);
                if (session->kernel_session == NULL) {
                        session_unlock(session);
                        continue;
                }

                /* This is not suppose to be -1 but this is an extra security check */
                if (session->kernel_session->consumer_fd < 0) {
                        session->kernel_session->consumer_fd = consumer_data->cmd_sock;
                }

                cds_list_for_each_entry(channel,
                                &session->kernel_session->channel_list.head, list) {
                        if (channel->fd == fd) {
                                DBG("Channel found, updating kernel streams");
                                ret = kernel_open_channel_stream(channel);
                                if (ret < 0) {
                                        goto error;
                                }

                                /*
                                 * Have we already sent fds to the consumer? If yes, it means
                                 * that tracing is started so it is safe to send our updated
                                 * stream fds.
                                 */
                                if (session->kernel_session->consumer_fds_sent == 1 &&
                                                session->kernel_session->consumer != NULL) {
                                        ret = kernel_consumer_send_channel_stream(
                                                        session->kernel_session->consumer_fd, channel,
                                                        session->kernel_session);
                                        if (ret < 0) {
                                                goto error;
                                        }
                                }
                                goto error;
                        }
                }
                session_unlock(session);
        }
        session_unlock_list();
        return ret;

error:
        session_unlock(session);
        session_unlock_list();
        return ret;
}

/*
 * For each tracing session, update newly registered apps.
 */
static void update_ust_app(int app_sock)
{
        struct ltt_session *sess, *stmp;

        session_lock_list();

        /* For all tracing session(s) */
        cds_list_for_each_entry_safe(sess, stmp, &session_list_ptr->head, list) {
                session_lock(sess);
                if (sess->ust_session) {
                        ust_app_global_update(sess->ust_session, app_sock);
                }
                session_unlock(sess);
        }

        session_unlock_list();
}

/*
 * This thread manage event coming from the kernel.
 *
 * Features supported in this thread:
 *    -) CPU Hotplug
 */
static void *thread_manage_kernel(void *data)
{
        int ret, i, pollfd, update_poll_flag = 1;
        uint32_t revents, nb_fd;
        char tmp;
        struct lttng_poll_event events;

        DBG("Thread manage kernel started");

        ret = create_thread_poll_set(&events, 2);
        if (ret < 0) {
                goto error_poll_create;
        }

        ret = lttng_poll_add(&events, kernel_poll_pipe[0], LPOLLIN);
        if (ret < 0) {
                goto error;
        }

        while (1) {
                if (update_poll_flag == 1) {
                        /*
                         * Reset number of fd in the poll set. Always 2 since there is the thread
                         * quit pipe and the kernel pipe.
                         */
                        events.nb_fd = 2;

                        ret = update_kernel_poll(&events);
                        if (ret < 0) {
                                goto error;
                        }
                        update_poll_flag = 0;
                }

                nb_fd = LTTNG_POLL_GETNB(&events);

                DBG("Thread kernel polling on %d fds", nb_fd);

                /* Zeroed the poll events */
                lttng_poll_reset(&events);

                /* Poll infinite value of time */
        restart:
                ret = lttng_poll_wait(&events, -1);
                if (ret < 0) {
                        /*
                         * Restart interrupted system call.
                         */
                        if (errno == EINTR) {
                                goto restart;
                        }
                        goto error;
                } else if (ret == 0) {
                        /* Should not happen since timeout is infinite */
                        ERR("Return value of poll is 0 with an infinite timeout.\n"
                                "This should not have happened! Continuing...");
                        continue;
                }

                for (i = 0; i < nb_fd; i++) {
                        /* Fetch once the poll data */
                        revents = LTTNG_POLL_GETEV(&events, i);
                        pollfd = LTTNG_POLL_GETFD(&events, i);

                        /* Thread quit pipe has been closed. Killing thread. */
                        ret = check_thread_quit_pipe(pollfd, revents);
                        if (ret) {
                                goto error;
                        }

                        /* Check for data on kernel pipe */
                        if (pollfd == kernel_poll_pipe[0] && (revents & LPOLLIN)) {
                                ret = read(kernel_poll_pipe[0], &tmp, 1);
                                update_poll_flag = 1;
                                continue;
                        } else {
                                /*
                                 * New CPU detected by the kernel. Adding kernel stream to
                                 * kernel session and updating the kernel consumer
                                 */
                                if (revents & LPOLLIN) {
                                        ret = update_kernel_stream(&kconsumer_data, pollfd);
                                        if (ret < 0) {
                                                continue;
                                        }
                                        break;
                                        /*
                                         * TODO: We might want to handle the LPOLLERR | LPOLLHUP
                                         * and unregister kernel stream at this point.
                                         */
                                }
                        }
                }
        }

error:
        lttng_poll_clean(&events);
error_poll_create:
        DBG("Kernel thread dying");
        return NULL;
}

/*
 * This thread manage the consumer error sent back to the session daemon.
 */
static void *thread_manage_consumer(void *data)
{
        int sock = -1, i, ret, pollfd;
        uint32_t revents, nb_fd;
        enum lttcomm_return_code code;
        struct lttng_poll_event events;
        struct consumer_data *consumer_data = data;

        DBG("[thread] Manage consumer started");

        ret = lttcomm_listen_unix_sock(consumer_data->err_sock);
        if (ret < 0) {
                goto error_listen;
        }

        /*
         * Pass 2 as size here for the thread quit pipe and kconsumerd_err_sock.
         * Nothing more will be added to this poll set.
         */
        ret = create_thread_poll_set(&events, 2);
        if (ret < 0) {
                goto error_poll;
        }

        ret = lttng_poll_add(&events, consumer_data->err_sock, LPOLLIN | LPOLLRDHUP);
        if (ret < 0) {
                goto error;
        }

        nb_fd = LTTNG_POLL_GETNB(&events);

        /* Inifinite blocking call, waiting for transmission */
restart:
        ret = lttng_poll_wait(&events, -1);
        if (ret < 0) {
                /*
                 * Restart interrupted system call.
                 */
                if (errno == EINTR) {
                        goto restart;
                }
                goto error;
        }

        for (i = 0; i < nb_fd; i++) {
                /* Fetch once the poll data */
                revents = LTTNG_POLL_GETEV(&events, i);
                pollfd = LTTNG_POLL_GETFD(&events, i);

                /* Thread quit pipe has been closed. Killing thread. */
                ret = check_thread_quit_pipe(pollfd, revents);
                if (ret) {
                        goto error;
                }

                /* Event on the registration socket */
                if (pollfd == consumer_data->err_sock) {
                        if (revents & (LPOLLERR | LPOLLHUP | LPOLLRDHUP)) {
                                ERR("consumer err socket poll error");
                                goto error;
                        }
                }
        }

        sock = lttcomm_accept_unix_sock(consumer_data->err_sock);
        if (sock < 0) {
                goto error;
        }

        DBG2("Receiving code from consumer err_sock");

        /* Getting status code from kconsumerd */
        ret = lttcomm_recv_unix_sock(sock, &code,
                        sizeof(enum lttcomm_return_code));
        if (ret <= 0) {
                goto error;
        }

        if (code == CONSUMERD_COMMAND_SOCK_READY) {
                consumer_data->cmd_sock =
                        lttcomm_connect_unix_sock(consumer_data->cmd_unix_sock_path);
                if (consumer_data->cmd_sock < 0) {
                        sem_post(&consumer_data->sem);
                        PERROR("consumer connect");
                        goto error;
                }
                /* Signal condition to tell that the kconsumerd is ready */
                sem_post(&consumer_data->sem);
                DBG("consumer command socket ready");
        } else {
                ERR("consumer error when waiting for SOCK_READY : %s",
                                lttcomm_get_readable_code(-code));
                goto error;
        }

        /* Remove the kconsumerd error sock since we've established a connexion */
        ret = lttng_poll_del(&events, consumer_data->err_sock);
        if (ret < 0) {
                goto error;
        }

        ret = lttng_poll_add(&events, sock, LPOLLIN | LPOLLRDHUP);
        if (ret < 0) {
                goto error;
        }

        /* Update number of fd */
        nb_fd = LTTNG_POLL_GETNB(&events);

        /* Inifinite blocking call, waiting for transmission */
restart_poll:
        ret = lttng_poll_wait(&events, -1);
        if (ret < 0) {
                /*
                 * Restart interrupted system call.
                 */
                if (errno == EINTR) {
                        goto restart_poll;
                }
                goto error;
        }

        for (i = 0; i < nb_fd; i++) {
                /* Fetch once the poll data */
                revents = LTTNG_POLL_GETEV(&events, i);
                pollfd = LTTNG_POLL_GETFD(&events, i);

                /* Thread quit pipe has been closed. Killing thread. */
                ret = check_thread_quit_pipe(pollfd, revents);
                if (ret) {
                        goto error;
                }

                /* Event on the kconsumerd socket */
                if (pollfd == sock) {
                        if (revents & (LPOLLERR | LPOLLHUP | LPOLLRDHUP)) {
                                ERR("consumer err socket second poll error");
                                goto error;
                        }
                }
        }

        /* Wait for any kconsumerd error */
        ret = lttcomm_recv_unix_sock(sock, &code,
                        sizeof(enum lttcomm_return_code));
        if (ret <= 0) {
                ERR("consumer closed the command socket");
                goto error;
        }

        ERR("consumer return code : %s", lttcomm_get_readable_code(-code));

error:
        /* Immediately set the consumerd state to stopped */
        if (consumer_data->type == LTTNG_CONSUMER_KERNEL) {
                uatomic_set(&kernel_consumerd_state, CONSUMER_ERROR);
        } else if (consumer_data->type == LTTNG_CONSUMER64_UST ||
                        consumer_data->type == LTTNG_CONSUMER32_UST) {
                uatomic_set(&ust_consumerd_state, CONSUMER_ERROR);
        } else {
                /* Code flow error... */
                assert(0);
        }

        if (consumer_data->err_sock >= 0) {
                ret = close(consumer_data->err_sock);
                if (ret) {
                        PERROR("close");
                }
        }
        if (consumer_data->cmd_sock >= 0) {
                ret = close(consumer_data->cmd_sock);
                if (ret) {
                        PERROR("close");
                }
        }
        if (sock >= 0) {
                ret = close(sock);
                if (ret) {
                        PERROR("close");
                }
        }

        unlink(consumer_data->err_unix_sock_path);
        unlink(consumer_data->cmd_unix_sock_path);
        consumer_data->pid = 0;

        lttng_poll_clean(&events);
error_poll:
error_listen:
        DBG("consumer thread cleanup completed");

        return NULL;
}

/*
 * This thread manage application communication.
 */
static void *thread_manage_apps(void *data)
{
        int i, ret, pollfd;
        uint32_t revents, nb_fd;
        struct ust_command ust_cmd;
        struct lttng_poll_event events;

        DBG("[thread] Manage application started");

        rcu_register_thread();
        rcu_thread_online();

        ret = create_thread_poll_set(&events, 2);
        if (ret < 0) {
                goto error_poll_create;
        }

        ret = lttng_poll_add(&events, apps_cmd_pipe[0], LPOLLIN | LPOLLRDHUP);
        if (ret < 0) {
                goto error;
        }

        while (1) {
                /* Zeroed the events structure */
                lttng_poll_reset(&events);

                nb_fd = LTTNG_POLL_GETNB(&events);

                DBG("Apps thread polling on %d fds", nb_fd);

                /* Inifinite blocking call, waiting for transmission */
        restart:
                ret = lttng_poll_wait(&events, -1);
                if (ret < 0) {
                        /*
                         * Restart interrupted system call.
                         */
                        if (errno == EINTR) {
                                goto restart;
                        }
                        goto error;
                }

                for (i = 0; i < nb_fd; i++) {
                        /* Fetch once the poll data */
                        revents = LTTNG_POLL_GETEV(&events, i);
                        pollfd = LTTNG_POLL_GETFD(&events, i);

                        /* Thread quit pipe has been closed. Killing thread. */
                        ret = check_thread_quit_pipe(pollfd, revents);
                        if (ret) {
                                goto error;
                        }

                        /* Inspect the apps cmd pipe */
                        if (pollfd == apps_cmd_pipe[0]) {
                                if (revents & (LPOLLERR | LPOLLHUP | LPOLLRDHUP)) {
                                        ERR("Apps command pipe error");
                                        goto error;
                                } else if (revents & LPOLLIN) {
                                        /* Empty pipe */
                                        ret = read(apps_cmd_pipe[0], &ust_cmd, sizeof(ust_cmd));
                                        if (ret < 0 || ret < sizeof(ust_cmd)) {
                                                PERROR("read apps cmd pipe");
                                                goto error;
                                        }

                                        /* Register applicaton to the session daemon */
                                        ret = ust_app_register(&ust_cmd.reg_msg,
                                                        ust_cmd.sock);
                                        if (ret == -ENOMEM) {
                                                goto error;
                                        } else if (ret < 0) {
                                                break;
                                        }

                                        /*
                                         * Validate UST version compatibility.
                                         */
                                        ret = ust_app_validate_version(ust_cmd.sock);
                                        if (ret >= 0) {
                                                /*
                                                 * Add channel(s) and event(s) to newly registered apps
                                                 * from lttng global UST domain.
                                                 */
                                                update_ust_app(ust_cmd.sock);
                                        }

                                        ret = ust_app_register_done(ust_cmd.sock);
                                        if (ret < 0) {
                                                /*
                                                 * If the registration is not possible, we simply
                                                 * unregister the apps and continue
                                                 */
                                                ust_app_unregister(ust_cmd.sock);
                                        } else {
                                                /*
                                                 * We just need here to monitor the close of the UST
                                                 * socket and poll set monitor those by default.
                                                 * Listen on POLLIN (even if we never expect any
                                                 * data) to ensure that hangup wakes us.
                                                 */
                                                ret = lttng_poll_add(&events, ust_cmd.sock, LPOLLIN);
                                                if (ret < 0) {
                                                        goto error;
                                                }

                                                DBG("Apps with sock %d added to poll set",
                                                                ust_cmd.sock);
                                        }

                                        break;
                                }
                        } else {
                                /*
                                 * At this point, we know that a registered application made
                                 * the event at poll_wait.
                                 */
                                if (revents & (LPOLLERR | LPOLLHUP | LPOLLRDHUP)) {
                                        /* Removing from the poll set */
                                        ret = lttng_poll_del(&events, pollfd);
                                        if (ret < 0) {
                                                goto error;
                                        }

                                        /* Socket closed on remote end. */
                                        ust_app_unregister(pollfd);
                                        break;
                                }
                        }
                }
        }

error:
        lttng_poll_clean(&events);
error_poll_create:
        DBG("Application communication apps thread cleanup complete");
        rcu_thread_offline();
        rcu_unregister_thread();
        return NULL;
}

/*
 * Dispatch request from the registration threads to the application
 * communication thread.
 */
static void *thread_dispatch_ust_registration(void *data)
{
        int ret;
        struct cds_wfq_node *node;
        struct ust_command *ust_cmd = NULL;

        DBG("[thread] Dispatch UST command started");

        while (!dispatch_thread_exit) {
                /* Atomically prepare the queue futex */
                futex_nto1_prepare(&ust_cmd_queue.futex);

                do {
                        /* Dequeue command for registration */
                        node = cds_wfq_dequeue_blocking(&ust_cmd_queue.queue);
                        if (node == NULL) {
                                DBG("Woken up but nothing in the UST command queue");
                                /* Continue thread execution */
                                break;
                        }

                        ust_cmd = caa_container_of(node, struct ust_command, node);

                        DBG("Dispatching UST registration pid:%d ppid:%d uid:%d"
                                        " gid:%d sock:%d name:%s (version %d.%d)",
                                        ust_cmd->reg_msg.pid, ust_cmd->reg_msg.ppid,
                                        ust_cmd->reg_msg.uid, ust_cmd->reg_msg.gid,
                                        ust_cmd->sock, ust_cmd->reg_msg.name,
                                        ust_cmd->reg_msg.major, ust_cmd->reg_msg.minor);
                        /*
                         * Inform apps thread of the new application registration. This
                         * call is blocking so we can be assured that the data will be read
                         * at some point in time or wait to the end of the world :)
                         */
                        ret = write(apps_cmd_pipe[1], ust_cmd,
                                        sizeof(struct ust_command));
                        if (ret < 0) {
                                PERROR("write apps cmd pipe");
                                if (errno == EBADF) {
                                        /*
                                         * We can't inform the application thread to process
                                         * registration. We will exit or else application
                                         * registration will not occur and tracing will never
                                         * start.
                                         */
                                        goto error;
                                }
                        }
                        free(ust_cmd);
                } while (node != NULL);

                /* Futex wait on queue. Blocking call on futex() */
                futex_nto1_wait(&ust_cmd_queue.futex);
        }

error:
        DBG("Dispatch thread dying");
        return NULL;
}

/*
 * This thread manage application registration.
 */
static void *thread_registration_apps(void *data)
{
        int sock = -1, i, ret, pollfd;
        uint32_t revents, nb_fd;
        struct lttng_poll_event events;
        /*
         * Get allocated in this thread, enqueued to a global queue, dequeued and
         * freed in the manage apps thread.
         */
        struct ust_command *ust_cmd = NULL;

        DBG("[thread] Manage application registration started");

        ret = lttcomm_listen_unix_sock(apps_sock);
        if (ret < 0) {
                goto error_listen;
        }

        /*
         * Pass 2 as size here for the thread quit pipe and apps socket. Nothing
         * more will be added to this poll set.
         */
        ret = create_thread_poll_set(&events, 2);
        if (ret < 0) {
                goto error_create_poll;
        }

        /* Add the application registration socket */
        ret = lttng_poll_add(&events, apps_sock, LPOLLIN | LPOLLRDHUP);
        if (ret < 0) {
                goto error_poll_add;
        }

        /* Notify all applications to register */
        ret = notify_ust_apps(1);
        if (ret < 0) {
                ERR("Failed to notify applications or create the wait shared memory.\n"
                        "Execution continues but there might be problem for already\n"
                        "running applications that wishes to register.");
        }

        while (1) {
                DBG("Accepting application registration");

                nb_fd = LTTNG_POLL_GETNB(&events);

                /* Inifinite blocking call, waiting for transmission */
        restart:
                ret = lttng_poll_wait(&events, -1);
                if (ret < 0) {
                        /*
                         * Restart interrupted system call.
                         */
                        if (errno == EINTR) {
                                goto restart;
                        }
                        goto error;
                }

                for (i = 0; i < nb_fd; i++) {
                        /* Fetch once the poll data */
                        revents = LTTNG_POLL_GETEV(&events, i);
                        pollfd = LTTNG_POLL_GETFD(&events, i);

                        /* Thread quit pipe has been closed. Killing thread. */
                        ret = check_thread_quit_pipe(pollfd, revents);
                        if (ret) {
                                goto error;
                        }

                        /* Event on the registration socket */
                        if (pollfd == apps_sock) {
                                if (revents & (LPOLLERR | LPOLLHUP | LPOLLRDHUP)) {
                                        ERR("Register apps socket poll error");
                                        goto error;
                                } else if (revents & LPOLLIN) {
                                        sock = lttcomm_accept_unix_sock(apps_sock);
                                        if (sock < 0) {
                                                goto error;
                                        }

                                        /* Create UST registration command for enqueuing */
                                        ust_cmd = zmalloc(sizeof(struct ust_command));
                                        if (ust_cmd == NULL) {
                                                PERROR("ust command zmalloc");
                                                goto error;
                                        }

                                        /*
                                         * Using message-based transmissions to ensure we don't
                                         * have to deal with partially received messages.
                                         */
                                        ret = lttng_fd_get(LTTNG_FD_APPS, 1);
                                        if (ret < 0) {
                                                ERR("Exhausted file descriptors allowed for applications.");
                                                free(ust_cmd);
                                                ret = close(sock);
                                                if (ret) {
                                                        PERROR("close");
                                                }
                                                sock = -1;
                                                continue;
                                        }
                                        ret = lttcomm_recv_unix_sock(sock, &ust_cmd->reg_msg,
                                                        sizeof(struct ust_register_msg));
                                        if (ret < 0 || ret < sizeof(struct ust_register_msg)) {
                                                if (ret < 0) {
                                                        PERROR("lttcomm_recv_unix_sock register apps");
                                                } else {
                                                        ERR("Wrong size received on apps register");
                                                }
                                                free(ust_cmd);
                                                ret = close(sock);
                                                if (ret) {
                                                        PERROR("close");
                                                }
                                                lttng_fd_put(LTTNG_FD_APPS, 1);
                                                sock = -1;
                                                continue;
                                        }

                                        ust_cmd->sock = sock;
                                        sock = -1;

                                        DBG("UST registration received with pid:%d ppid:%d uid:%d"
                                                        " gid:%d sock:%d name:%s (version %d.%d)",
                                                        ust_cmd->reg_msg.pid, ust_cmd->reg_msg.ppid,
                                                        ust_cmd->reg_msg.uid, ust_cmd->reg_msg.gid,
                                                        ust_cmd->sock, ust_cmd->reg_msg.name,
                                                        ust_cmd->reg_msg.major, ust_cmd->reg_msg.minor);

                                        /*
                                         * Lock free enqueue the registration request. The red pill
                                         * has been taken! This apps will be part of the *system*.
                                         */
                                        cds_wfq_enqueue(&ust_cmd_queue.queue, &ust_cmd->node);

                                        /*
                                         * Wake the registration queue futex. Implicit memory
                                         * barrier with the exchange in cds_wfq_enqueue.
                                         */
                                        futex_nto1_wake(&ust_cmd_queue.futex);
                                }
                        }
                }
        }

error:
        /* Notify that the registration thread is gone */
        notify_ust_apps(0);

        if (apps_sock >= 0) {
                ret = close(apps_sock);
                if (ret) {
                        PERROR("close");
                }
        }
        if (sock >= 0) {
                ret = close(sock);
                if (ret) {
                        PERROR("close");
                }
                lttng_fd_put(LTTNG_FD_APPS, 1);
        }
        unlink(apps_unix_sock_path);

error_poll_add:
        lttng_poll_clean(&events);
error_listen:
error_create_poll:
        DBG("UST Registration thread cleanup complete");

        return NULL;
}

/*
 * Start the thread_manage_consumer. This must be done after a lttng-consumerd
 * exec or it will fails.
 */
static int spawn_consumer_thread(struct consumer_data *consumer_data)
{
        int ret;
        struct timespec timeout;

        timeout.tv_sec = DEFAULT_SEM_WAIT_TIMEOUT;
        timeout.tv_nsec = 0;

        /* Setup semaphore */
        ret = sem_init(&consumer_data->sem, 0, 0);
        if (ret < 0) {
                PERROR("sem_init consumer semaphore");
                goto error;
        }

        ret = pthread_create(&consumer_data->thread, NULL,
                        thread_manage_consumer, consumer_data);
        if (ret != 0) {
                PERROR("pthread_create consumer");
                ret = -1;
                goto error;
        }

        /* Get time for sem_timedwait absolute timeout */
        ret = clock_gettime(CLOCK_REALTIME, &timeout);
        if (ret < 0) {
                PERROR("clock_gettime spawn consumer");
                /* Infinite wait for the kconsumerd thread to be ready */
                ret = sem_wait(&consumer_data->sem);
        } else {
                /* Normal timeout if the gettime was successful */
                timeout.tv_sec += DEFAULT_SEM_WAIT_TIMEOUT;
                ret = sem_timedwait(&consumer_data->sem, &timeout);
        }

        if (ret < 0) {
                if (errno == ETIMEDOUT) {
                        /*
                         * Call has timed out so we kill the kconsumerd_thread and return
                         * an error.
                         */
                        ERR("The consumer thread was never ready. Killing it");
                        ret = pthread_cancel(consumer_data->thread);
                        if (ret < 0) {
                                PERROR("pthread_cancel consumer thread");
                        }
                } else {
                        PERROR("semaphore wait failed consumer thread");
                }
                goto error;
        }

        pthread_mutex_lock(&consumer_data->pid_mutex);
        if (consumer_data->pid == 0) {
                ERR("Kconsumerd did not start");
                pthread_mutex_unlock(&consumer_data->pid_mutex);
                goto error;
        }
        pthread_mutex_unlock(&consumer_data->pid_mutex);

        return 0;

error:
        return ret;
}

/*
 * Join consumer thread
 */
static int join_consumer_thread(struct consumer_data *consumer_data)
{
        void *status;
        int ret;

        if (consumer_data->pid != 0) {
                ret = kill(consumer_data->pid, SIGTERM);
                if (ret) {
                        ERR("Error killing consumer daemon");
                        return ret;
                }
                return pthread_join(consumer_data->thread, &status);
        } else {
                return 0;
        }
}

/*
 * Fork and exec a consumer daemon (consumerd).
 *
 * Return pid if successful else -1.
 */
static pid_t spawn_consumerd(struct consumer_data *consumer_data)
{
        int ret;
        pid_t pid;
        const char *consumer_to_use;
        const char *verbosity;
        struct stat st;

        DBG("Spawning consumerd");

        pid = fork();
        if (pid == 0) {
                /*
                 * Exec consumerd.
                 */
                if (opt_verbose_consumer) {
                        verbosity = "--verbose";
                } else {
                        verbosity = "--quiet";
                }
                switch (consumer_data->type) {
                case LTTNG_CONSUMER_KERNEL:
                        /*
                         * Find out which consumerd to execute. We will first try the
                         * 64-bit path, then the sessiond's installation directory, and
                         * fallback on the 32-bit one,
                         */
                        DBG3("Looking for a kernel consumer at these locations:");
                        DBG3("  1) %s", consumerd64_bin);
                        DBG3("  2) %s/%s", INSTALL_BIN_PATH, CONSUMERD_FILE);
                        DBG3("  3) %s", consumerd32_bin);
                        if (stat(consumerd64_bin, &st) == 0) {
                                DBG3("Found location #1");
                                consumer_to_use = consumerd64_bin;
                        } else if (stat(INSTALL_BIN_PATH "/" CONSUMERD_FILE, &st) == 0) {
                                DBG3("Found location #2");
                                consumer_to_use = INSTALL_BIN_PATH "/" CONSUMERD_FILE;
                        } else if (stat(consumerd32_bin, &st) == 0) {
                                DBG3("Found location #3");
                                consumer_to_use = consumerd32_bin;
                        } else {
                                DBG("Could not find any valid consumerd executable");
                                break;
                        }
                        DBG("Using kernel consumer at: %s",  consumer_to_use);
                        execl(consumer_to_use,
                                "lttng-consumerd", verbosity, "-k",
                                "--consumerd-cmd-sock", consumer_data->cmd_unix_sock_path,
                                "--consumerd-err-sock", consumer_data->err_unix_sock_path,
                                NULL);
                        break;
                case LTTNG_CONSUMER64_UST:
                {
                        char *tmpnew = NULL;

                        if (consumerd64_libdir[0] != '\0') {
                                char *tmp;
                                size_t tmplen;

                                tmp = getenv("LD_LIBRARY_PATH");
                                if (!tmp) {
                                        tmp = "";
                                }
                                tmplen = strlen("LD_LIBRARY_PATH=")
                                        + strlen(consumerd64_libdir) + 1 /* : */ + strlen(tmp);
                                tmpnew = zmalloc(tmplen + 1 /* \0 */);
                                if (!tmpnew) {
                                        ret = -ENOMEM;
                                        goto error;
                                }
                                strcpy(tmpnew, "LD_LIBRARY_PATH=");
                                strcat(tmpnew, consumerd64_libdir);
                                if (tmp[0] != '\0') {
                                        strcat(tmpnew, ":");
                                        strcat(tmpnew, tmp);
                                }
                                ret = putenv(tmpnew);
                                if (ret) {
                                        ret = -errno;
                                        goto error;
                                }
                        }
                        DBG("Using 64-bit UST consumer at: %s",  consumerd64_bin);
                        ret = execl(consumerd64_bin, "lttng-consumerd", verbosity, "-u",
                                        "--consumerd-cmd-sock", consumer_data->cmd_unix_sock_path,
                                        "--consumerd-err-sock", consumer_data->err_unix_sock_path,
                                        NULL);
                        if (consumerd64_libdir[0] != '\0') {
                                free(tmpnew);
                        }
                        if (ret) {
                                goto error;
                        }
                        break;
                }
                case LTTNG_CONSUMER32_UST:
                {
                        char *tmpnew = NULL;

                        if (consumerd32_libdir[0] != '\0') {
                                char *tmp;
                                size_t tmplen;

                                tmp = getenv("LD_LIBRARY_PATH");
                                if (!tmp) {
                                        tmp = "";
                                }
                                tmplen = strlen("LD_LIBRARY_PATH=")
                                        + strlen(consumerd32_libdir) + 1 /* : */ + strlen(tmp);
                                tmpnew = zmalloc(tmplen + 1 /* \0 */);
                                if (!tmpnew) {
                                        ret = -ENOMEM;
                                        goto error;
                                }
                                strcpy(tmpnew, "LD_LIBRARY_PATH=");
                                strcat(tmpnew, consumerd32_libdir);
                                if (tmp[0] != '\0') {
                                        strcat(tmpnew, ":");
                                        strcat(tmpnew, tmp);
                                }
                                ret = putenv(tmpnew);
                                if (ret) {
                                        ret = -errno;
                                        goto error;
                                }
                        }
                        DBG("Using 32-bit UST consumer at: %s",  consumerd32_bin);
                        ret = execl(consumerd32_bin, "lttng-consumerd", verbosity, "-u",
                                        "--consumerd-cmd-sock", consumer_data->cmd_unix_sock_path,
                                        "--consumerd-err-sock", consumer_data->err_unix_sock_path,
                                        NULL);
                        if (consumerd32_libdir[0] != '\0') {
                                free(tmpnew);
                        }
                        if (ret) {
                                goto error;
                        }
                        break;
                }
                default:
                        PERROR("unknown consumer type");
                        exit(EXIT_FAILURE);
                }
                if (errno != 0) {
                        PERROR("kernel start consumer exec");
                }
                exit(EXIT_FAILURE);
        } else if (pid > 0) {
                ret = pid;
        } else {
                PERROR("start consumer fork");
                ret = -errno;
        }
error:
        return ret;
}

/*
 * Spawn the consumerd daemon and session daemon thread.
 */
static int start_consumerd(struct consumer_data *consumer_data)
{
        int ret;

        pthread_mutex_lock(&consumer_data->pid_mutex);
        if (consumer_data->pid != 0) {
                pthread_mutex_unlock(&consumer_data->pid_mutex);
                goto end;
        }

        ret = spawn_consumerd(consumer_data);
        if (ret < 0) {
                ERR("Spawning consumerd failed");
                pthread_mutex_unlock(&consumer_data->pid_mutex);
                goto error;
        }

        /* Setting up the consumer_data pid */
        consumer_data->pid = ret;
        DBG2("Consumer pid %d", consumer_data->pid);
        pthread_mutex_unlock(&consumer_data->pid_mutex);

        DBG2("Spawning consumer control thread");
        ret = spawn_consumer_thread(consumer_data);
        if (ret < 0) {
                ERR("Fatal error spawning consumer control thread");
                goto error;
        }

end:
        return 0;

error:
        return ret;
}

/*
 * Check version of the lttng-modules.
 */
static int validate_lttng_modules_version(void)
{
        return kernel_validate_version(kernel_tracer_fd);
}

/*
 * Setup necessary data for kernel tracer action.
 */
static int init_kernel_tracer(void)
{
        int ret;

        /* Modprobe lttng kernel modules */
        ret = modprobe_lttng_control();
        if (ret < 0) {
                goto error;
        }

        /* Open debugfs lttng */
        kernel_tracer_fd = open(module_proc_lttng, O_RDWR);
        if (kernel_tracer_fd < 0) {
                DBG("Failed to open %s", module_proc_lttng);
                ret = -1;
                goto error_open;
        }

        /* Validate kernel version */
        ret = validate_lttng_modules_version();
        if (ret < 0) {
                goto error_version;
        }

        ret = modprobe_lttng_data();
        if (ret < 0) {
                goto error_modules;
        }

        DBG("Kernel tracer fd %d", kernel_tracer_fd);
        return 0;

error_version:
        modprobe_remove_lttng_control();
        ret = close(kernel_tracer_fd);
        if (ret) {
                PERROR("close");
        }
        kernel_tracer_fd = -1;
        return LTTCOMM_KERN_VERSION;

error_modules:
        ret = close(kernel_tracer_fd);
        if (ret) {
                PERROR("close");
        }

error_open:
        modprobe_remove_lttng_control();

error:
        WARN("No kernel tracer available");
        kernel_tracer_fd = -1;
        if (!is_root) {
                return LTTCOMM_NEED_ROOT_SESSIOND;
        } else {
                return LTTCOMM_KERN_NA;
        }
}

/*
 * Init tracing by creating trace directory and sending fds kernel consumer.
 */
static int init_kernel_tracing(struct ltt_kernel_session *session)
{
        int ret = 0;

        if (session->consumer_fds_sent == 0 && session->consumer != NULL) {
                /*
                 * Assign default kernel consumer socket if no consumer assigned to the
                 * kernel session. At this point, it's NOT supposed to be -1 but this is
                 * an extra security check.
                 */
                if (session->consumer_fd < 0) {
                        session->consumer_fd = kconsumer_data.cmd_sock;
                }

                ret = kernel_consumer_send_session(session->consumer_fd, session);
                if (ret < 0) {
                        ret = LTTCOMM_KERN_CONSUMER_FAIL;
                        goto error;
                }
        }

error:
        return ret;
}

/*
 * Create a socket to the relayd using the URI.
 *
 * On success, the relayd_sock pointer is set to the created socket.
 * Else, it is untouched and an lttcomm error code is returned.
 */
static int create_connect_relayd(struct consumer_output *output,
                const char *session_name, struct lttng_uri *uri,
                struct lttcomm_sock **relayd_sock)
{
        int ret;
        struct lttcomm_sock *sock;

        /* Create socket object from URI */
        sock = lttcomm_alloc_sock_from_uri(uri);
        if (sock == NULL) {
                ret = LTTCOMM_FATAL;
                goto error;
        }

        ret = lttcomm_create_sock(sock);
        if (ret < 0) {
                ret = LTTCOMM_FATAL;
                goto error;
        }

        /* Connect to relayd so we can proceed with a session creation. */
        ret = relayd_connect(sock);
        if (ret < 0) {
                ERR("Unable to reach lttng-relayd");
                ret = LTTCOMM_RELAYD_SESSION_FAIL;
                goto free_sock;
        }

        /* Create socket for control stream. */
        if (uri->stype == LTTNG_STREAM_CONTROL) {
                DBG3("Creating relayd stream socket from URI");

                /* Check relayd version */
                ret = relayd_version_check(sock, LTTNG_UST_COMM_MAJOR, 0);
                if (ret < 0) {
                        ret = LTTCOMM_RELAYD_VERSION_FAIL;
                        goto close_sock;
                }
        } else if (uri->stype == LTTNG_STREAM_DATA) {
                DBG3("Creating relayd data socket from URI");
        } else {
                /* Command is not valid */
                ERR("Relayd invalid stream type: %d", uri->stype);
                ret = LTTCOMM_INVALID;
                goto close_sock;
        }

        *relayd_sock = sock;

        return LTTCOMM_OK;

close_sock:
        if (sock) {
                (void) relayd_close(sock);
        }
free_sock:
        if (sock) {
                lttcomm_destroy_sock(sock);
        }
error:
        return ret;
}

/*
 * Connect to the relayd using URI and send the socket to the right consumer.
 */
static int send_socket_relayd_consumer(int domain, struct ltt_session *session,
                struct lttng_uri *relayd_uri, struct consumer_output *consumer,
                int consumer_fd)
{
        int ret;
        struct lttcomm_sock *sock = NULL;

        /* Set the network sequence index if not set. */
        if (consumer->net_seq_index == -1) {
                /*
                 * Increment net_seq_idx because we are about to transfer the
                 * new relayd socket to the consumer.
                 */
                uatomic_inc(&relayd_net_seq_idx);
                /* Assign unique key so the consumer can match streams */
                consumer->net_seq_index = uatomic_read(&relayd_net_seq_idx);
        }

        /* Connect to relayd and make version check if uri is the control. */
        ret = create_connect_relayd(consumer, session->name, relayd_uri, &sock);
        if (ret != LTTCOMM_OK) {
                goto close_sock;
        }

        /* If the control socket is connected, network session is ready */
        if (relayd_uri->stype == LTTNG_STREAM_CONTROL) {
                session->net_handle = 1;
        }

        switch (domain) {
        case LTTNG_DOMAIN_KERNEL:
                /* Send relayd socket to consumer. */
                ret = kernel_consumer_send_relayd_socket(consumer_fd, sock,
                                consumer, relayd_uri->stype);
                if (ret < 0) {
                        ret = LTTCOMM_ENABLE_CONSUMER_FAIL;
                        goto close_sock;
                }
                break;
        case LTTNG_DOMAIN_UST:
                /* Send relayd socket to consumer. */
                ret = ust_consumer_send_relayd_socket(consumer_fd, sock,
                                consumer, relayd_uri->stype);
                if (ret < 0) {
                        ret = LTTCOMM_ENABLE_CONSUMER_FAIL;
                        goto close_sock;
                }
                break;
        }

        ret = LTTCOMM_OK;

        /*
         * Close socket which was dup on the consumer side. The session daemon does
         * NOT keep track of the relayd socket(s) once transfer to the consumer.
         */

close_sock:
        if (sock) {
                (void) relayd_close(sock);
                lttcomm_destroy_sock(sock);
        }

        return ret;
}

/*
 * Send both relayd sockets to a specific consumer and domain.  This is a
 * helper function to facilitate sending the information to the consumer for a
 * session.
 */
static int send_sockets_relayd_consumer(int domain,
                struct ltt_session *session, struct consumer_output *consumer, int fd)
{
        int ret;

        /* Sending control relayd socket. */
        ret = send_socket_relayd_consumer(domain, session,
                        &consumer->dst.net.control, consumer, fd);
        if (ret != LTTCOMM_OK) {
                goto error;
        }

        /* Sending data relayd socket. */
        ret = send_socket_relayd_consumer(domain, session,
                        &consumer->dst.net.data, consumer, fd);
        if (ret != LTTCOMM_OK) {
                goto error;
        }

error:
        return ret;
}

/*
 * Setup relayd connections for a tracing session. First creates the socket to
 * the relayd and send them to the right domain consumer. Consumer type MUST be
 * network.
 */
static int setup_relayd(struct ltt_session *session)
{
        int ret = LTTCOMM_OK;
        struct ltt_ust_session *usess;
        struct ltt_kernel_session *ksess;

        assert(session);

        usess = session->ust_session;
        ksess = session->kernel_session;

        DBG2("Setting relayd for session %s", session->name);

        if (usess && usess->consumer->sock == -1 &&
                        usess->consumer->type == CONSUMER_DST_NET &&
                        usess->consumer->enabled) {
                /* Setup relayd for 64 bits consumer */
                if (ust_consumerd64_fd >= 0) {
                        send_sockets_relayd_consumer(LTTNG_DOMAIN_UST, session,
                                        usess->consumer, ust_consumerd64_fd);
                        if (ret != LTTCOMM_OK) {
                                goto error;
                        }
                }

                /* Setup relayd for 32 bits consumer */
                if (ust_consumerd32_fd >= 0) {
                        send_sockets_relayd_consumer(LTTNG_DOMAIN_UST, session,
                                        usess->consumer, ust_consumerd32_fd);
                        if (ret != LTTCOMM_OK) {
                                goto error;
                        }
                }
        } else if (ksess && ksess->consumer->sock == -1 &&
                        ksess->consumer->type == CONSUMER_DST_NET &&
                        ksess->consumer->enabled) {
                send_sockets_relayd_consumer(LTTNG_DOMAIN_KERNEL, session,
                                ksess->consumer, ksess->consumer_fd);
                if (ret != LTTCOMM_OK) {
                        goto error;
                }
        }

error:
        return ret;
}

/*
 * Copy consumer output from the tracing session to the domain session. The
 * function also applies the right modification on a per domain basis for the
 * trace files destination directory.
 */
static int copy_session_consumer(int domain, struct ltt_session *session)
{
        int ret;
        const char *dir_name;
        struct consumer_output *consumer;

        switch (domain) {
        case LTTNG_DOMAIN_KERNEL:
                DBG3("Copying tracing session consumer output in kernel session");
                session->kernel_session->consumer =
                        consumer_copy_output(session->consumer);
                /* Ease our life a bit for the next part */
                consumer = session->kernel_session->consumer;
                dir_name = DEFAULT_KERNEL_TRACE_DIR;
                break;
        case LTTNG_DOMAIN_UST:
                DBG3("Copying tracing session consumer output in UST session");
                session->ust_session->consumer =
                        consumer_copy_output(session->consumer);
                /* Ease our life a bit for the next part */
                consumer = session->ust_session->consumer;
                dir_name = DEFAULT_UST_TRACE_DIR;
                break;
        default:
                ret = LTTCOMM_UNKNOWN_DOMAIN;
                goto error;
        }

        /* Append correct directory to subdir */
        strncat(consumer->subdir, dir_name, sizeof(consumer->subdir));
        DBG3("Copy session consumer subdir %s", consumer->subdir);

        /* Add default trace directory name */
        if (consumer->type == CONSUMER_DST_LOCAL) {
                strncat(consumer->dst.trace_path, dir_name,
                                sizeof(consumer->dst.trace_path));
        }

        ret = LTTCOMM_OK;

error:
        return ret;
}

/*
 * Create an UST session and add it to the session ust list.
 */
static int create_ust_session(struct ltt_session *session,
                struct lttng_domain *domain)
{
        int ret;
        struct ltt_ust_session *lus = NULL;

        assert(session);
        assert(session->consumer);

        switch (domain->type) {
        case LTTNG_DOMAIN_UST:
                break;
        default:
                ERR("Unknown UST domain on create session %d", domain->type);
                ret = LTTCOMM_UNKNOWN_DOMAIN;
                goto error;
        }

        DBG("Creating UST session");

        lus = trace_ust_create_session(session->path, session->id, domain);
        if (lus == NULL) {
                ret = LTTCOMM_UST_SESS_FAIL;
                goto error;
        }

        if (session->consumer->type == CONSUMER_DST_LOCAL) {
                ret = run_as_mkdir_recursive(lus->pathname, S_IRWXU | S_IRWXG,
                                session->uid, session->gid);
                if (ret < 0) {
                        if (ret != -EEXIST) {
                                ERR("Trace directory creation error");
                                ret = LTTCOMM_UST_SESS_FAIL;
                                goto error;
                        }
                }
        }

        lus->uid = session->uid;
        lus->gid = session->gid;
        session->ust_session = lus;

        /* Copy session output to the newly created UST session */
        ret = copy_session_consumer(domain->type, session);
        if (ret != LTTCOMM_OK) {
                goto error;
        }

        return LTTCOMM_OK;

error:
        free(lus);
        session->ust_session = NULL;
        return ret;
}

/*
 * Create a kernel tracer session then create the default channel.
 */
static int create_kernel_session(struct ltt_session *session)
{
        int ret;

        DBG("Creating kernel session");

        ret = kernel_create_session(session, kernel_tracer_fd);
        if (ret < 0) {
                ret = LTTCOMM_KERN_SESS_FAIL;
                goto error;
        }

        /* Set kernel consumer socket fd */
        if (kconsumer_data.cmd_sock >= 0) {
                session->kernel_session->consumer_fd = kconsumer_data.cmd_sock;
        }

        /* Copy session output to the newly created Kernel session */
        ret = copy_session_consumer(LTTNG_DOMAIN_KERNEL, session);
        if (ret != LTTCOMM_OK) {
                goto error;
        }

        /* Create directory(ies) on local filesystem. */
        if (session->consumer->type == CONSUMER_DST_LOCAL) {
                ret = run_as_mkdir_recursive(
                                session->kernel_session->consumer->dst.trace_path,
                                S_IRWXU | S_IRWXG, session->uid, session->gid);
                if (ret < 0) {
                        if (ret != -EEXIST) {
                                ERR("Trace directory creation error");
                                goto error;
                        }
                }
        }

        session->kernel_session->uid = session->uid;
        session->kernel_session->gid = session->gid;

        return LTTCOMM_OK;

error:
        trace_kernel_destroy_session(session->kernel_session);
        session->kernel_session = NULL;
        return ret;
}

/*
 * Check if the UID or GID match the session. Root user has access to all
 * sessions.
 */
static int session_access_ok(struct ltt_session *session, uid_t uid, gid_t gid)
{
        if (uid != session->uid && gid != session->gid && uid != 0) {
                return 0;
        } else {
                return 1;
        }
}

/*
 * Count number of session permitted by uid/gid.
 */
static unsigned int lttng_sessions_count(uid_t uid, gid_t gid)
{
        unsigned int i = 0;
        struct ltt_session *session;

        DBG("Counting number of available session for UID %d GID %d",
                uid, gid);
        cds_list_for_each_entry(session, &session_list_ptr->head, list) {
                /*
                 * Only list the sessions the user can control.
                 */
                if (!session_access_ok(session, uid, gid)) {
                        continue;
                }
                i++;
        }
        return i;
}

/*
 * Using the session list, filled a lttng_session array to send back to the
 * client for session listing.
 *
 * The session list lock MUST be acquired before calling this function. Use
 * session_lock_list() and session_unlock_list().
 */
static void list_lttng_sessions(struct lttng_session *sessions, uid_t uid,
                gid_t gid)
{
        unsigned int i = 0;
        struct ltt_session *session;

        DBG("Getting all available session for UID %d GID %d",
                uid, gid);
        /*
         * Iterate over session list and append data after the control struct in
         * the buffer.
         */
        cds_list_for_each_entry(session, &session_list_ptr->head, list) {
                /*
                 * Only list the sessions the user can control.
                 */
                if (!session_access_ok(session, uid, gid)) {
                        continue;
                }
                strncpy(sessions[i].path, session->path, PATH_MAX);
                sessions[i].path[PATH_MAX - 1] = '\0';
                strncpy(sessions[i].name, session->name, NAME_MAX);
                sessions[i].name[NAME_MAX - 1] = '\0';
                sessions[i].enabled = session->enabled;
                i++;
        }
}

/*
 * Fill lttng_channel array of all channels.
 */
static void list_lttng_channels(int domain, struct ltt_session *session,
                struct lttng_channel *channels)
{
        int i = 0;
        struct ltt_kernel_channel *kchan;

        DBG("Listing channels for session %s", session->name);

        switch (domain) {
        case LTTNG_DOMAIN_KERNEL:
                /* Kernel channels */
                if (session->kernel_session != NULL) {
                        cds_list_for_each_entry(kchan,
                                        &session->kernel_session->channel_list.head, list) {
                                /* Copy lttng_channel struct to array */
                                memcpy(&channels[i], kchan->channel, sizeof(struct lttng_channel));
                                channels[i].enabled = kchan->enabled;
                                i++;
                        }
                }
                break;
        case LTTNG_DOMAIN_UST:
        {
                struct lttng_ht_iter iter;
                struct ltt_ust_channel *uchan;

                cds_lfht_for_each_entry(session->ust_session->domain_global.channels->ht,
                                &iter.iter, uchan, node.node) {
                        strncpy(channels[i].name, uchan->name, LTTNG_SYMBOL_NAME_LEN);
                        channels[i].attr.overwrite = uchan->attr.overwrite;
                        channels[i].attr.subbuf_size = uchan->attr.subbuf_size;
                        channels[i].attr.num_subbuf = uchan->attr.num_subbuf;
                        channels[i].attr.switch_timer_interval =
                                uchan->attr.switch_timer_interval;
                        channels[i].attr.read_timer_interval =
                                uchan->attr.read_timer_interval;
                        channels[i].enabled = uchan->enabled;
                        switch (uchan->attr.output) {
                        case LTTNG_UST_MMAP:
                        default:
                                channels[i].attr.output = LTTNG_EVENT_MMAP;
                                break;
                        }
                        i++;
                }
                break;
        }
        default:
                break;
        }
}

/*
 * Create a list of ust global domain events.
 */
static int list_lttng_ust_global_events(char *channel_name,
                struct ltt_ust_domain_global *ust_global, struct lttng_event **events)
{
        int i = 0, ret = 0;
        unsigned int nb_event = 0;
        struct lttng_ht_iter iter;
        struct lttng_ht_node_str *node;
        struct ltt_ust_channel *uchan;
        struct ltt_ust_event *uevent;
        struct lttng_event *tmp;

        DBG("Listing UST global events for channel %s", channel_name);

        rcu_read_lock();

        lttng_ht_lookup(ust_global->channels, (void *)channel_name, &iter);
        node = lttng_ht_iter_get_node_str(&iter);
        if (node == NULL) {
                ret = -LTTCOMM_UST_CHAN_NOT_FOUND;
                goto error;
        }

        uchan = caa_container_of(&node->node, struct ltt_ust_channel, node.node);

        nb_event += lttng_ht_get_count(uchan->events);

        if (nb_event == 0) {
                ret = nb_event;
                goto error;
        }

        DBG3("Listing UST global %d events", nb_event);

        tmp = zmalloc(nb_event * sizeof(struct lttng_event));
        if (tmp == NULL) {
                ret = -LTTCOMM_FATAL;
                goto error;
        }

        cds_lfht_for_each_entry(uchan->events->ht, &iter.iter, uevent, node.node) {
                strncpy(tmp[i].name, uevent->attr.name, LTTNG_SYMBOL_NAME_LEN);
                tmp[i].name[LTTNG_SYMBOL_NAME_LEN - 1] = '\0';
                tmp[i].enabled = uevent->enabled;
                switch (uevent->attr.instrumentation) {
                case LTTNG_UST_TRACEPOINT:
                        tmp[i].type = LTTNG_EVENT_TRACEPOINT;
                        break;
                case LTTNG_UST_PROBE:
                        tmp[i].type = LTTNG_EVENT_PROBE;
                        break;
                case LTTNG_UST_FUNCTION:
                        tmp[i].type = LTTNG_EVENT_FUNCTION;
                        break;
                }
                tmp[i].loglevel = uevent->attr.loglevel;
                switch (uevent->attr.loglevel_type) {
                case LTTNG_UST_LOGLEVEL_ALL:
                        tmp[i].loglevel_type = LTTNG_EVENT_LOGLEVEL_ALL;
                        break;
                case LTTNG_UST_LOGLEVEL_RANGE:
                        tmp[i].loglevel_type = LTTNG_EVENT_LOGLEVEL_RANGE;
                        break;
                case LTTNG_UST_LOGLEVEL_SINGLE:
                        tmp[i].loglevel_type = LTTNG_EVENT_LOGLEVEL_SINGLE;
                        break;
                }
                i++;
        }

        ret = nb_event;
        *events = tmp;

error:
        rcu_read_unlock();
        return ret;
}

/*
 * Fill lttng_event array of all kernel events in the channel.
 */
static int list_lttng_kernel_events(char *channel_name,
                struct ltt_kernel_session *kernel_session, struct lttng_event **events)
{
        int i = 0, ret;
        unsigned int nb_event;
        struct ltt_kernel_event *event;
        struct ltt_kernel_channel *kchan;

        kchan = trace_kernel_get_channel_by_name(channel_name, kernel_session);
        if (kchan == NULL) {
                ret = LTTCOMM_KERN_CHAN_NOT_FOUND;
                goto error;
        }

        nb_event = kchan->event_count;

        DBG("Listing events for channel %s", kchan->channel->name);

        if (nb_event == 0) {
                ret = nb_event;
                goto error;
        }

        *events = zmalloc(nb_event * sizeof(struct lttng_event));
        if (*events == NULL) {
                ret = LTTCOMM_FATAL;
                goto error;
        }

        /* Kernel channels */
        cds_list_for_each_entry(event, &kchan->events_list.head , list) {
                strncpy((*events)[i].name, event->event->name, LTTNG_SYMBOL_NAME_LEN);
                (*events)[i].name[LTTNG_SYMBOL_NAME_LEN - 1] = '\0';
                (*events)[i].enabled = event->enabled;
                switch (event->event->instrumentation) {
                        case LTTNG_KERNEL_TRACEPOINT:
                                (*events)[i].type = LTTNG_EVENT_TRACEPOINT;
                                break;
                        case LTTNG_KERNEL_KPROBE:
                        case LTTNG_KERNEL_KRETPROBE:
                                (*events)[i].type = LTTNG_EVENT_PROBE;
                                memcpy(&(*events)[i].attr.probe, &event->event->u.kprobe,
                                                sizeof(struct lttng_kernel_kprobe));
                                break;
                        case LTTNG_KERNEL_FUNCTION:
                                (*events)[i].type = LTTNG_EVENT_FUNCTION;
                                memcpy(&((*events)[i].attr.ftrace), &event->event->u.ftrace,
                                                sizeof(struct lttng_kernel_function));
                                break;
                        case LTTNG_KERNEL_NOOP:
                                (*events)[i].type = LTTNG_EVENT_NOOP;
                                break;
                        case LTTNG_KERNEL_SYSCALL:
                                (*events)[i].type = LTTNG_EVENT_SYSCALL;
                                break;
                        case LTTNG_KERNEL_ALL:
                                assert(0);
                                break;
                }
                i++;
        }

        return nb_event;

error:
        return ret;
}

/*
 * Command LTTNG_DISABLE_CHANNEL processed by the client thread.
 */
static int cmd_disable_channel(struct ltt_session *session,
                int domain, char *channel_name)
{
        int ret;
        struct ltt_ust_session *usess;

        usess = session->ust_session;

        switch (domain) {
        case LTTNG_DOMAIN_KERNEL:
        {
                ret = channel_kernel_disable(session->kernel_session,
                                channel_name);
                if (ret != LTTCOMM_OK) {
                        goto error;
                }

                kernel_wait_quiescent(kernel_tracer_fd);
                break;
        }
        case LTTNG_DOMAIN_UST:
        {
                struct ltt_ust_channel *uchan;
                struct lttng_ht *chan_ht;

                chan_ht = usess->domain_global.channels;

                uchan = trace_ust_find_channel_by_name(chan_ht, channel_name);
                if (uchan == NULL) {
                        ret = LTTCOMM_UST_CHAN_NOT_FOUND;
                        goto error;
                }

                ret = channel_ust_disable(usess, domain, uchan);
                if (ret != LTTCOMM_OK) {
                        goto error;
                }
                break;
        }
#if 0
        case LTTNG_DOMAIN_UST_PID_FOLLOW_CHILDREN:
        case LTTNG_DOMAIN_UST_EXEC_NAME:
        case LTTNG_DOMAIN_UST_PID:
#endif
        default:
                ret = LTTCOMM_UNKNOWN_DOMAIN;
                goto error;
        }

        ret = LTTCOMM_OK;

error:
        return ret;
}

/*
 * Command LTTNG_ENABLE_CHANNEL processed by the client thread.
 */
static int cmd_enable_channel(struct ltt_session *session,
                int domain, struct lttng_channel *attr)
{
        int ret;
        struct ltt_ust_session *usess = session->ust_session;
        struct lttng_ht *chan_ht;

        DBG("Enabling channel %s for session %s", attr->name, session->name);

        switch (domain) {
        case LTTNG_DOMAIN_KERNEL:
        {
                struct ltt_kernel_channel *kchan;

                kchan = trace_kernel_get_channel_by_name(attr->name,
                                session->kernel_session);
                if (kchan == NULL) {
                        ret = channel_kernel_create(session->kernel_session,
                                        attr, kernel_poll_pipe[1]);
                } else {
                        ret = channel_kernel_enable(session->kernel_session, kchan);
                }

                if (ret != LTTCOMM_OK) {
                        goto error;
                }

                kernel_wait_quiescent(kernel_tracer_fd);
                break;
        }
        case LTTNG_DOMAIN_UST:
        {
                struct ltt_ust_channel *uchan;

                chan_ht = usess->domain_global.channels;

                uchan = trace_ust_find_channel_by_name(chan_ht, attr->name);
                if (uchan == NULL) {
                        ret = channel_ust_create(usess, domain, attr);
                } else {
                        ret = channel_ust_enable(usess, domain, uchan);
                }
                break;
        }
#if 0
        case LTTNG_DOMAIN_UST_PID_FOLLOW_CHILDREN:
        case LTTNG_DOMAIN_UST_EXEC_NAME:
        case LTTNG_DOMAIN_UST_PID:
#endif
        default:
                ret = LTTCOMM_UNKNOWN_DOMAIN;
                goto error;
        }

error:
        return ret;
}

/*
 * Command LTTNG_DISABLE_EVENT processed by the client thread.
 */
static int cmd_disable_event(struct ltt_session *session, int domain,
                char *channel_name, char *event_name)
{
        int ret;

        switch (domain) {
        case LTTNG_DOMAIN_KERNEL:
        {
                struct ltt_kernel_channel *kchan;
                struct ltt_kernel_session *ksess;

                ksess = session->kernel_session;

                kchan = trace_kernel_get_channel_by_name(channel_name, ksess);
                if (kchan == NULL) {
                        ret = LTTCOMM_KERN_CHAN_NOT_FOUND;
                        goto error;
                }

                ret = event_kernel_disable_tracepoint(ksess, kchan, event_name);
                if (ret != LTTCOMM_OK) {
                        goto error;
                }

                kernel_wait_quiescent(kernel_tracer_fd);
                break;
        }
        case LTTNG_DOMAIN_UST:
        {
                struct ltt_ust_channel *uchan;
                struct ltt_ust_session *usess;

                usess = session->ust_session;

                uchan = trace_ust_find_channel_by_name(usess->domain_global.channels,
                                channel_name);
                if (uchan == NULL) {
                        ret = LTTCOMM_UST_CHAN_NOT_FOUND;
                        goto error;
                }

                ret = event_ust_disable_tracepoint(usess, domain, uchan, event_name);
                if (ret != LTTCOMM_OK) {
                        goto error;
                }

                DBG3("Disable UST event %s in channel %s completed", event_name,
                                channel_name);
                break;
        }
#if 0
        case LTTNG_DOMAIN_UST_EXEC_NAME:
        case LTTNG_DOMAIN_UST_PID:
        case LTTNG_DOMAIN_UST_PID_FOLLOW_CHILDREN:
#endif
        default:
                ret = LTTCOMM_UND;
                goto error;
        }

        ret = LTTCOMM_OK;

error:
        return ret;
}

/*
 * Command LTTNG_DISABLE_ALL_EVENT processed by the client thread.
 */
static int cmd_disable_event_all(struct ltt_session *session, int domain,
                char *channel_name)
{
        int ret;

        switch (domain) {
        case LTTNG_DOMAIN_KERNEL:
        {
                struct ltt_kernel_session *ksess;
                struct ltt_kernel_channel *kchan;

                ksess = session->kernel_session;

                kchan = trace_kernel_get_channel_by_name(channel_name, ksess);
                if (kchan == NULL) {
                        ret = LTTCOMM_KERN_CHAN_NOT_FOUND;
                        goto error;
                }

                ret = event_kernel_disable_all(ksess, kchan);
                if (ret != LTTCOMM_OK) {
                        goto error;
                }

                kernel_wait_quiescent(kernel_tracer_fd);
                break;
        }
        case LTTNG_DOMAIN_UST:
        {
                struct ltt_ust_session *usess;
                struct ltt_ust_channel *uchan;

                usess = session->ust_session;

                uchan = trace_ust_find_channel_by_name(usess->domain_global.channels,
                                channel_name);
                if (uchan == NULL) {
                        ret = LTTCOMM_UST_CHAN_NOT_FOUND;
                        goto error;
                }

                ret = event_ust_disable_all_tracepoints(usess, domain, uchan);
                if (ret != 0) {
                        goto error;
                }

                DBG3("Disable all UST events in channel %s completed", channel_name);

                break;
        }
#if 0
        case LTTNG_DOMAIN_UST_EXEC_NAME:
        case LTTNG_DOMAIN_UST_PID:
        case LTTNG_DOMAIN_UST_PID_FOLLOW_CHILDREN:
#endif
        default:
                ret = LTTCOMM_UND;
                goto error;
        }

        ret = LTTCOMM_OK;

error:
        return ret;
}

/*
 * Command LTTNG_ADD_CONTEXT processed by the client thread.
 */
static int cmd_add_context(struct ltt_session *session, int domain,
                char *channel_name, char *event_name, struct lttng_event_context *ctx)
{
        int ret;

        switch (domain) {
        case LTTNG_DOMAIN_KERNEL:
                /* Add kernel context to kernel tracer */
                ret = context_kernel_add(session->kernel_session, ctx,
                                event_name, channel_name);
                if (ret != LTTCOMM_OK) {
                        goto error;
                }
                break;
        case LTTNG_DOMAIN_UST:
        {
                struct ltt_ust_session *usess = session->ust_session;

                ret = context_ust_add(usess, domain, ctx, event_name, channel_name);
                if (ret != LTTCOMM_OK) {
                        goto error;
                }
                break;
        }
#if 0
        case LTTNG_DOMAIN_UST_EXEC_NAME:
        case LTTNG_DOMAIN_UST_PID:
        case LTTNG_DOMAIN_UST_PID_FOLLOW_CHILDREN:
#endif
        default:
                ret = LTTCOMM_UND;
                goto error;
        }

        ret = LTTCOMM_OK;

error:
        return ret;
}

/*
 * Command LTTNG_ENABLE_EVENT processed by the client thread.
 */
static int cmd_enable_event(struct ltt_session *session, int domain,
                char *channel_name, struct lttng_event *event)
{
        int ret;
        struct lttng_channel *attr;
        struct ltt_ust_session *usess = session->ust_session;

        switch (domain) {
        case LTTNG_DOMAIN_KERNEL:
        {
                struct ltt_kernel_channel *kchan;

                kchan = trace_kernel_get_channel_by_name(channel_name,
                                session->kernel_session);
                if (kchan == NULL) {
                        attr = channel_new_default_attr(domain);
                        if (attr == NULL) {
                                ret = LTTCOMM_FATAL;
                                goto error;
                        }
                        snprintf(attr->name, NAME_MAX, "%s", channel_name);

                        /* This call will notify the kernel thread */
                        ret = channel_kernel_create(session->kernel_session,
                                        attr, kernel_poll_pipe[1]);
                        if (ret != LTTCOMM_OK) {
                                free(attr);
                                goto error;
                        }
                        free(attr);
                }

                /* Get the newly created kernel channel pointer */
                kchan = trace_kernel_get_channel_by_name(channel_name,
                                session->kernel_session);
                if (kchan == NULL) {
                        /* This sould not happen... */
                        ret = LTTCOMM_FATAL;
                        goto error;
                }

                ret = event_kernel_enable_tracepoint(session->kernel_session, kchan,
                                event);
                if (ret != LTTCOMM_OK) {
                        goto error;
                }

                kernel_wait_quiescent(kernel_tracer_fd);
                break;
        }
        case LTTNG_DOMAIN_UST:
        {
                struct lttng_channel *attr;
                struct ltt_ust_channel *uchan;

                /* Get channel from global UST domain */
                uchan = trace_ust_find_channel_by_name(usess->domain_global.channels,
                                channel_name);
                if (uchan == NULL) {
                        /* Create default channel */
                        attr = channel_new_default_attr(domain);
                        if (attr == NULL) {
                                ret = LTTCOMM_FATAL;
                                goto error;
                        }
                        snprintf(attr->name, NAME_MAX, "%s", channel_name);
                        attr->name[NAME_MAX - 1] = '\0';

                        ret = channel_ust_create(usess, domain, attr);
                        if (ret != LTTCOMM_OK) {
                                free(attr);
                                goto error;
                        }
                        free(attr);

                        /* Get the newly created channel reference back */
                        uchan = trace_ust_find_channel_by_name(
                                        usess->domain_global.channels, channel_name);
                        if (uchan == NULL) {
                                /* Something is really wrong */
                                ret = LTTCOMM_FATAL;
                                goto error;
                        }
                }

                /* At this point, the session and channel exist on the tracer */
                ret = event_ust_enable_tracepoint(usess, domain, uchan, event);
                if (ret != LTTCOMM_OK) {
                        goto error;
                }
                break;
        }
#if 0
        case LTTNG_DOMAIN_UST_EXEC_NAME:
        case LTTNG_DOMAIN_UST_PID:
        case LTTNG_DOMAIN_UST_PID_FOLLOW_CHILDREN:
#endif
        default:
                ret = LTTCOMM_UND;
                goto error;
        }

        ret = LTTCOMM_OK;

error:
        return ret;
}

/*
 * Command LTTNG_ENABLE_ALL_EVENT processed by the client thread.
 */
static int cmd_enable_event_all(struct ltt_session *session, int domain,
                char *channel_name, int event_type)
{
        int ret;
        struct ltt_kernel_channel *kchan;

        switch (domain) {
        case LTTNG_DOMAIN_KERNEL:
                kchan = trace_kernel_get_channel_by_name(channel_name,
                                session->kernel_session);
                if (kchan == NULL) {
                        /* This call will notify the kernel thread */
                        ret = channel_kernel_create(session->kernel_session, NULL,
                                        kernel_poll_pipe[1]);
                        if (ret != LTTCOMM_OK) {
                                goto error;
                        }

                        /* Get the newly created kernel channel pointer */
                        kchan = trace_kernel_get_channel_by_name(channel_name,
                                        session->kernel_session);
                        if (kchan == NULL) {
                                /* This sould not happen... */
                                ret = LTTCOMM_FATAL;
                                goto error;
                        }

                }

                switch (event_type) {
                case LTTNG_EVENT_SYSCALL:
                        ret = event_kernel_enable_all_syscalls(session->kernel_session,
                                        kchan, kernel_tracer_fd);
                        break;
                case LTTNG_EVENT_TRACEPOINT:
                        /*
                         * This call enables all LTTNG_KERNEL_TRACEPOINTS and
                         * events already registered to the channel.
                         */
                        ret = event_kernel_enable_all_tracepoints(session->kernel_session,
                                        kchan, kernel_tracer_fd);
                        break;
                case LTTNG_EVENT_ALL:
                        /* Enable syscalls and tracepoints */
                        ret = event_kernel_enable_all(session->kernel_session,
                                        kchan, kernel_tracer_fd);
                        break;
                default:
                        ret = LTTCOMM_KERN_ENABLE_FAIL;
                        goto error;
                }

                /* Manage return value */
                if (ret != LTTCOMM_OK) {
                        goto error;
                }

                kernel_wait_quiescent(kernel_tracer_fd);
                break;
        case LTTNG_DOMAIN_UST:
        {
                struct lttng_channel *attr;
                struct ltt_ust_channel *uchan;
                struct ltt_ust_session *usess = session->ust_session;

                /* Get channel from global UST domain */
                uchan = trace_ust_find_channel_by_name(usess->domain_global.channels,
                                channel_name);
                if (uchan == NULL) {
                        /* Create default channel */
                        attr = channel_new_default_attr(domain);
                        if (attr == NULL) {
                                ret = LTTCOMM_FATAL;
                                goto error;
                        }
                        snprintf(attr->name, NAME_MAX, "%s", channel_name);
                        attr->name[NAME_MAX - 1] = '\0';

                        /* Use the internal command enable channel */
                        ret = channel_ust_create(usess, domain, attr);
                        if (ret != LTTCOMM_OK) {
                                free(attr);
                                goto error;
                        }
                        free(attr);

                        /* Get the newly created channel reference back */
                        uchan = trace_ust_find_channel_by_name(
                                        usess->domain_global.channels, channel_name);
                        if (uchan == NULL) {
                                /* Something is really wrong */
                                ret = LTTCOMM_FATAL;
                                goto error;
                        }
                }

                /* At this point, the session and channel exist on the tracer */

                switch (event_type) {
                case LTTNG_EVENT_ALL:
                case LTTNG_EVENT_TRACEPOINT:
                        ret = event_ust_enable_all_tracepoints(usess, domain, uchan);
                        if (ret != LTTCOMM_OK) {
                                goto error;
                        }
                        break;
                default:
                        ret = LTTCOMM_UST_ENABLE_FAIL;
                        goto error;
                }

                /* Manage return value */
                if (ret != LTTCOMM_OK) {
                        goto error;
                }

                break;
        }
#if 0
        case LTTNG_DOMAIN_UST_EXEC_NAME:
        case LTTNG_DOMAIN_UST_PID:
        case LTTNG_DOMAIN_UST_PID_FOLLOW_CHILDREN:
#endif
        default:
                ret = LTTCOMM_UND;
                goto error;
        }

        ret = LTTCOMM_OK;

error:
        return ret;
}

/*
 * Command LTTNG_LIST_TRACEPOINTS processed by the client thread.
 */
static ssize_t cmd_list_tracepoints(int domain, struct lttng_event **events)
{
        int ret;
        ssize_t nb_events = 0;

        switch (domain) {
        case LTTNG_DOMAIN_KERNEL:
                nb_events = kernel_list_events(kernel_tracer_fd, events);
                if (nb_events < 0) {
                        ret = LTTCOMM_KERN_LIST_FAIL;
                        goto error;
                }
                break;
        case LTTNG_DOMAIN_UST:
                nb_events = ust_app_list_events(events);
                if (nb_events < 0) {
                        ret = LTTCOMM_UST_LIST_FAIL;
                        goto error;
                }
                break;
        default:
                ret = LTTCOMM_UND;
                goto error;
        }

        return nb_events;

error:
        /* Return negative value to differentiate return code */
        return -ret;
}

/*
 * Command LTTNG_LIST_TRACEPOINT_FIELDS processed by the client thread.
 */
static ssize_t cmd_list_tracepoint_fields(int domain,
                        struct lttng_event_field **fields)
{
        int ret;
        ssize_t nb_fields = 0;

        switch (domain) {
        case LTTNG_DOMAIN_UST:
                nb_fields = ust_app_list_event_fields(fields);
                if (nb_fields < 0) {
                        ret = LTTCOMM_UST_LIST_FAIL;
                        goto error;
                }
                break;
        case LTTNG_DOMAIN_KERNEL:
        default:        /* fall-through */
                ret = LTTCOMM_UND;
                goto error;
        }

        return nb_fields;

error:
        /* Return negative value to differentiate return code */
        return -ret;
}

/*
 * Command LTTNG_START_TRACE processed by the client thread.
 */
static int cmd_start_trace(struct ltt_session *session)
{
        int ret;
        struct ltt_kernel_session *ksession;
        struct ltt_ust_session *usess;
        struct ltt_kernel_channel *kchan;

        /* Ease our life a bit ;) */
        ksession = session->kernel_session;
        usess = session->ust_session;

        if (session->enabled) {
                /* Already started. */
                ret = LTTCOMM_TRACE_ALREADY_STARTED;
                goto error;
        }

        session->enabled = 1;

        ret = setup_relayd(session);
        if (ret != LTTCOMM_OK) {
                ERR("Error setting up relayd for session %s", session->name);
                goto error;
        }

        /* Kernel tracing */
        if (ksession != NULL) {
                /* Open kernel metadata */
                if (ksession->metadata == NULL) {
                        ret = kernel_open_metadata(ksession,
                                        ksession->consumer->dst.trace_path);
                        if (ret < 0) {
                                ret = LTTCOMM_KERN_META_FAIL;
                                goto error;
                        }
                }

                /* Open kernel metadata stream */
                if (ksession->metadata_stream_fd < 0) {
                        ret = kernel_open_metadata_stream(ksession);
                        if (ret < 0) {
                                ERR("Kernel create metadata stream failed");
                                ret = LTTCOMM_KERN_STREAM_FAIL;
                                goto error;
                        }
                }

                /* For each channel */
                cds_list_for_each_entry(kchan, &ksession->channel_list.head, list) {
                        if (kchan->stream_count == 0) {
                                ret = kernel_open_channel_stream(kchan);
                                if (ret < 0) {
                                        ret = LTTCOMM_KERN_STREAM_FAIL;
                                        goto error;
                                }
                                /* Update the stream global counter */
                                ksession->stream_count_global += ret;
                        }
                }

                /* Setup kernel consumer socket and send fds to it */
                ret = init_kernel_tracing(ksession);
                if (ret < 0) {
                        ret = LTTCOMM_KERN_START_FAIL;
                        goto error;
                }

                /* This start the kernel tracing */
                ret = kernel_start_session(ksession);
                if (ret < 0) {
                        ret = LTTCOMM_KERN_START_FAIL;
                        goto error;
                }

                /* Quiescent wait after starting trace */
                kernel_wait_quiescent(kernel_tracer_fd);
        }

        /* Flag session that trace should start automatically */
        if (usess) {
                usess->start_trace = 1;

                ret = ust_app_start_trace_all(usess);
                if (ret < 0) {
                        ret = LTTCOMM_UST_START_FAIL;
                        goto error;
                }
        }

        ret = LTTCOMM_OK;

error:
        return ret;
}

/*
 * Command LTTNG_STOP_TRACE processed by the client thread.
 */
static int cmd_stop_trace(struct ltt_session *session)
{
        int ret;
        struct ltt_kernel_channel *kchan;
        struct ltt_kernel_session *ksession;
        struct ltt_ust_session *usess;

        /* Short cut */
        ksession = session->kernel_session;
        usess = session->ust_session;

        if (!session->enabled) {
                ret = LTTCOMM_TRACE_ALREADY_STOPPED;
                goto error;
        }

        session->enabled = 0;

        /* Kernel tracer */
        if (ksession != NULL) {
                DBG("Stop kernel tracing");

                /* Flush metadata if exist */
                if (ksession->metadata_stream_fd >= 0) {
                        ret = kernel_metadata_flush_buffer(ksession->metadata_stream_fd);
                        if (ret < 0) {
                                ERR("Kernel metadata flush failed");
                        }
                }

                /* Flush all buffers before stopping */
                cds_list_for_each_entry(kchan, &ksession->channel_list.head, list) {
                        ret = kernel_flush_buffer(kchan);
                        if (ret < 0) {
                                ERR("Kernel flush buffer error");
                        }
                }

                ret = kernel_stop_session(ksession);
                if (ret < 0) {
                        ret = LTTCOMM_KERN_STOP_FAIL;
                        goto error;
                }

                kernel_wait_quiescent(kernel_tracer_fd);
        }

        if (usess) {
                usess->start_trace = 0;

                ret = ust_app_stop_trace_all(usess);
                if (ret < 0) {
                        ret = LTTCOMM_UST_STOP_FAIL;
                        goto error;
                }
        }

        ret = LTTCOMM_OK;

error:
        return ret;
}

/*
 * Command LTTNG_CREATE_SESSION_URI processed by the client thread.
 */
static int cmd_create_session_uri(char *name, struct lttng_uri *ctrl_uri,
                struct lttng_uri *data_uri, unsigned int enable_consumer,
                lttng_sock_cred *creds)
{
        int ret;
        char *path = NULL;
        struct ltt_session *session;
        struct consumer_output *consumer;

        /* Verify if the session already exist */
        session = session_find_by_name(name);
        if (session != NULL) {
                ret = LTTCOMM_EXIST_SESS;
                goto error;
        }

        /* TODO: validate URIs */

        /* Create default consumer output */
        consumer = consumer_create_output(CONSUMER_DST_LOCAL);
        if (consumer == NULL) {
                ret = LTTCOMM_FATAL;
                goto error;
        }
        strncpy(consumer->subdir, ctrl_uri->subdir, sizeof(consumer->subdir));
        DBG2("Consumer subdir set to %s", consumer->subdir);

        switch (ctrl_uri->dtype) {
        case LTTNG_DST_IPV4:
        case LTTNG_DST_IPV6:
                /* Set control URI into consumer output object */
                ret = consumer_set_network_uri(consumer, ctrl_uri);
                if (ret < 0) {
                        ret = LTTCOMM_FATAL;
                        goto error;
                }

                /* Set data URI into consumer output object */
                ret = consumer_set_network_uri(consumer, data_uri);
                if (ret < 0) {
                        ret = LTTCOMM_FATAL;
                        goto error;
                }

                /* Empty path since the session is network */
                path = "";
                break;
        case LTTNG_DST_PATH:
                /* Very volatile pointer. Only used for the create session. */
                path = ctrl_uri->dst.path;
                strncpy(consumer->dst.trace_path, path,
                                sizeof(consumer->dst.trace_path));
                break;
        }

        /* Set if the consumer is enabled or not */
        consumer->enabled = enable_consumer;