Fix: remove break in epoll loop of apps. thread

[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 <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <inttypes.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/socket.h>
#include <common/defaults.h>
#include <common/kernel-consumer/kernel-consumer.h>
#include <common/futex.h>
#include <common/relayd/relayd.h>
#include <common/utils.h>

#include "lttng-sessiond.h"
#include "buffer-registry.h"
#include "channel.h"
#include "cmd.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"
#include "health.h"
#include "testpoint.h"
#include "ust-thread.h"

#define CONSUMERD_FILE  "lttng-consumerd"

/* Const values */
const char default_tracing_group[] = DEFAULT_TRACING_GROUP;

const char *progname;
const char *opt_tracing_group;
static const char *opt_pidfile;
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. Every value not initialized here is
 * set to 0 by the static definition.
 */
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,
        .metadata_sock.fd = -1,
        .pid_mutex = PTHREAD_MUTEX_INITIALIZER,
        .lock = PTHREAD_MUTEX_INITIALIZER,
        .cond = PTHREAD_COND_INITIALIZER,
        .cond_mutex = PTHREAD_MUTEX_INITIALIZER,
};
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,
        .metadata_sock.fd = -1,
        .pid_mutex = PTHREAD_MUTEX_INITIALIZER,
        .lock = PTHREAD_MUTEX_INITIALIZER,
        .cond = PTHREAD_COND_INITIALIZER,
        .cond_mutex = PTHREAD_MUTEX_INITIALIZER,
};
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,
        .metadata_sock.fd = -1,
        .pid_mutex = PTHREAD_MUTEX_INITIALIZER,
        .lock = PTHREAD_MUTEX_INITIALIZER,
        .cond = PTHREAD_COND_INITIALIZER,
        .cond_mutex = PTHREAD_MUTEX_INITIALIZER,
};

/* Shared between threads */
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];
/* Global health check unix path */
static char health_unix_sock_path[PATH_MAX];

/* Sockets and FDs */
static int client_sock = -1;
static int apps_sock = -1;
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 };

int apps_cmd_notify_pipe[2] = { -1, -1 };

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

static const char *module_proc_lttng = "/proc/lttng";

/*
 * 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;

/*
 * Socket timeout for receiving and sending in seconds.
 */
static int app_socket_timeout;

/* Set in main() with the current page size. */
long page_size;

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.
 */
int sessiond_set_thread_pollset(struct lttng_poll_event *events, size_t size)
{
        int ret;

        assert(events);

        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 | LPOLLERR);
        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;
 */
int sessiond_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;
}

/*
 * 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 */
        CMM_STORE_SHARED(dispatch_thread_exit, 1);
        futex_nto1_wake(&ust_cmd_queue.futex);
}

/*
 * Close every consumer sockets.
 */
static void close_consumer_sockets(void)
{
        int ret;

        if (kconsumer_data.err_sock >= 0) {
                ret = close(kconsumer_data.err_sock);
                if (ret < 0) {
                        PERROR("kernel consumer err_sock close");
                }
        }
        if (ustconsumer32_data.err_sock >= 0) {
                ret = close(ustconsumer32_data.err_sock);
                if (ret < 0) {
                        PERROR("UST consumerd32 err_sock close");
                }
        }
        if (ustconsumer64_data.err_sock >= 0) {
                ret = close(ustconsumer64_data.err_sock);
                if (ret < 0) {
                        PERROR("UST consumerd64 err_sock close");
                }
        }
        if (kconsumer_data.cmd_sock >= 0) {
                ret = close(kconsumer_data.cmd_sock);
                if (ret < 0) {
                        PERROR("kernel consumer cmd_sock close");
                }
        }
        if (ustconsumer32_data.cmd_sock >= 0) {
                ret = close(ustconsumer32_data.cmd_sock);
                if (ret < 0) {
                        PERROR("UST consumerd32 cmd_sock close");
                }
        }
        if (ustconsumer64_data.cmd_sock >= 0) {
                ret = close(ustconsumer64_data.cmd_sock);
                if (ret < 0) {
                        PERROR("UST consumerd64 cmd_sock close");
                }
        }
}

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

        DBG("Cleaning up");

        /* First thing first, stop all threads */
        utils_close_pipe(thread_quit_pipe);

        /*
         * If opt_pidfile is undefined, the default file will be wiped when
         * removing the rundir.
         */
        if (opt_pidfile) {
                ret = remove(opt_pidfile);
                if (ret < 0) {
                        PERROR("remove pidfile %s", opt_pidfile);
                }
        }

        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);
        free(rundir);

        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) {
                        cmd_destroy_session(sess, kernel_poll_pipe[1]);
                }
        }

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

        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();
        }

        close_consumer_sockets();

        /* <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_session *ksess;
        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;
                }
                ksess = session->kernel_session;

                cds_list_for_each_entry(channel, &ksess->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 (ksess->consumer_fds_sent == 1 && ksess->consumer != NULL) {
                                        struct lttng_ht_iter iter;
                                        struct consumer_socket *socket;

                                        rcu_read_lock();
                                        cds_lfht_for_each_entry(ksess->consumer->socks->ht,
                                                        &iter.iter, socket, node.node) {
                                                /* Code flow error */
                                                assert(socket->fd >= 0);

                                                pthread_mutex_lock(socket->lock);
                                                ret = kernel_consumer_send_channel_stream(socket,
                                                                channel, ksess);
                                                pthread_mutex_unlock(socket->lock);
                                                if (ret < 0) {
                                                        rcu_read_unlock();
                                                        goto error;
                                                }
                                        }
                                        rcu_read_unlock();
                                }
                                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. The session list
 * lock MUST be acquired before calling this.
 */
static void update_ust_app(int app_sock)
{
        struct ltt_session *sess, *stmp;

        /* 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);
        }
}

/*
 * 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, err = -1;
        uint32_t revents, nb_fd;
        char tmp;
        struct lttng_poll_event events;

        DBG("[thread] Thread manage kernel started");

        health_register(HEALTH_TYPE_KERNEL);

        /*
         * This first step of the while is to clean this structure which could free
         * non NULL pointers so initialize it before the loop.
         */
        lttng_poll_init(&events);

        if (testpoint(thread_manage_kernel)) {
                goto error_testpoint;
        }

        health_code_update();

        if (testpoint(thread_manage_kernel_before_loop)) {
                goto error_testpoint;
        }

        while (1) {
                health_code_update();

                if (update_poll_flag == 1) {
                        /* Clean events object. We are about to populate it again. */
                        lttng_poll_clean(&events);

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

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

                        /* This will add the available kernel channel if any. */
                        ret = update_kernel_poll(&events);
                        if (ret < 0) {
                                goto error;
                        }
                        update_poll_flag = 0;
                }

                DBG("Thread kernel polling on %d fds", LTTNG_POLL_GETNB(&events));

                /* Poll infinite value of time */
        restart:
                health_poll_entry();
                ret = lttng_poll_wait(&events, -1);
                health_poll_exit();
                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;
                }

                nb_fd = ret;

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

                        health_code_update();

                        /* Thread quit pipe has been closed. Killing thread. */
                        ret = sessiond_check_thread_quit_pipe(pollfd, revents);
                        if (ret) {
                                err = 0;
                                goto exit;
                        }

                        /* Check for data on kernel pipe */
                        if (pollfd == kernel_poll_pipe[0] && (revents & LPOLLIN)) {
                                do {
                                        ret = read(kernel_poll_pipe[0], &tmp, 1);
                                } while (ret < 0 && errno == EINTR);
                                /*
                                 * Ret value is useless here, if this pipe gets any actions an
                                 * update is required anyway.
                                 */
                                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.
                                         */
                                }
                        }
                }
        }

exit:
error:
        lttng_poll_clean(&events);
error_poll_create:
error_testpoint:
        utils_close_pipe(kernel_poll_pipe);
        kernel_poll_pipe[0] = kernel_poll_pipe[1] = -1;
        if (err) {
                health_error();
                ERR("Health error occurred in %s", __func__);
                WARN("Kernel thread died unexpectedly. "
                                "Kernel tracing can continue but CPU hotplug is disabled.");
        }
        health_unregister();
        DBG("Kernel thread dying");
        return NULL;
}

/*
 * Signal pthread condition of the consumer data that the thread.
 */
static void signal_consumer_condition(struct consumer_data *data, int state)
{
        pthread_mutex_lock(&data->cond_mutex);

        /*
         * The state is set before signaling. It can be any value, it's the waiter
         * job to correctly interpret this condition variable associated to the
         * consumer pthread_cond.
         *
         * A value of 0 means that the corresponding thread of the consumer data
         * was not started. 1 indicates that the thread has started and is ready
         * for action. A negative value means that there was an error during the
         * thread bootstrap.
         */
        data->consumer_thread_is_ready = state;
        (void) pthread_cond_signal(&data->cond);

        pthread_mutex_unlock(&data->cond_mutex);
}

/*
 * 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, err = -1;
        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");

        health_register(HEALTH_TYPE_CONSUMER);

        health_code_update();

        /*
         * Pass 3 as size here for the thread quit pipe, consumerd_err_sock and the
         * metadata_sock. Nothing more will be added to this poll set.
         */
        ret = sessiond_set_thread_pollset(&events, 3);
        if (ret < 0) {
                goto error_poll;
        }

        /*
         * The error socket here is already in a listening state which was done
         * just before spawning this thread to avoid a race between the consumer
         * daemon exec trying to connect and the listen() call.
         */
        ret = lttng_poll_add(&events, consumer_data->err_sock, LPOLLIN | LPOLLRDHUP);
        if (ret < 0) {
                goto error;
        }

        health_code_update();

        /* Infinite blocking call, waiting for transmission */
restart:
        health_poll_entry();

        if (testpoint(thread_manage_consumer)) {
                goto error;
        }

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

        nb_fd = ret;

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

                health_code_update();

                /* Thread quit pipe has been closed. Killing thread. */
                ret = sessiond_check_thread_quit_pipe(pollfd, revents);
                if (ret) {
                        err = 0;
                        goto exit;
                }

                /* 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;
        }

        /*
         * Set the CLOEXEC flag. Return code is useless because either way, the
         * show must go on.
         */
        (void) utils_set_fd_cloexec(sock);

        health_code_update();

        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;
        }

        health_code_update();

        if (code == LTTCOMM_CONSUMERD_COMMAND_SOCK_READY) {
                /* Connect both socket, command and metadata. */
                consumer_data->cmd_sock =
                        lttcomm_connect_unix_sock(consumer_data->cmd_unix_sock_path);
                consumer_data->metadata_sock.fd =
                        lttcomm_connect_unix_sock(consumer_data->cmd_unix_sock_path);
                if (consumer_data->cmd_sock < 0 ||
                                consumer_data->metadata_sock.fd < 0) {
                        PERROR("consumer connect cmd socket");
                        /* On error, signal condition and quit. */
                        signal_consumer_condition(consumer_data, -1);
                        goto error;
                }
                /* Create metadata socket lock. */
                consumer_data->metadata_sock.lock = zmalloc(sizeof(pthread_mutex_t));
                if (consumer_data->metadata_sock.lock == NULL) {
                        PERROR("zmalloc pthread mutex");
                        ret = -1;
                        goto error;
                }
                pthread_mutex_init(consumer_data->metadata_sock.lock, NULL);

                signal_consumer_condition(consumer_data, 1);
                DBG("Consumer command socket ready (fd: %d", consumer_data->cmd_sock);
                DBG("Consumer metadata socket ready (fd: %d)",
                                consumer_data->metadata_sock.fd);
        } else {
                ERR("consumer error when waiting for SOCK_READY : %s",
                                lttcomm_get_readable_code(-code));
                goto error;
        }

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

        /* Add new accepted error socket. */
        ret = lttng_poll_add(&events, sock, LPOLLIN | LPOLLRDHUP);
        if (ret < 0) {
                goto error;
        }

        /* Add metadata socket that is successfully connected. */
        ret = lttng_poll_add(&events, consumer_data->metadata_sock.fd,
                        LPOLLIN | LPOLLRDHUP);
        if (ret < 0) {
                goto error;
        }

        health_code_update();

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

                nb_fd = ret;

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

                        health_code_update();

                        /* Thread quit pipe has been closed. Killing thread. */
                        ret = sessiond_check_thread_quit_pipe(pollfd, revents);
                        if (ret) {
                                err = 0;
                                goto exit;
                        }

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

                                goto exit;
                        } else if (pollfd == consumer_data->metadata_sock.fd) {
                                /* UST metadata requests */
                                ret = ust_consumer_metadata_request(
                                                &consumer_data->metadata_sock);
                                if (ret < 0) {
                                        ERR("Handling metadata request");
                                        goto error;
                                }
                                break;
                        } else {
                                ERR("Unknown pollfd");
                                goto error;
                        }
                }
                health_code_update();
        }

exit:
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");
                }
                consumer_data->err_sock = -1;
        }
        if (consumer_data->cmd_sock >= 0) {
                ret = close(consumer_data->cmd_sock);
                if (ret) {
                        PERROR("close");
                }
                consumer_data->cmd_sock = -1;
        }
        if (consumer_data->metadata_sock.fd >= 0) {
                ret = close(consumer_data->metadata_sock.fd);
                if (ret) {
                        PERROR("close");
                }
        }
        /* Cleanup metadata socket mutex. */
        pthread_mutex_destroy(consumer_data->metadata_sock.lock);
        free(consumer_data->metadata_sock.lock);

        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:
        if (err) {
                health_error();
                ERR("Health error occurred in %s", __func__);
        }
        health_unregister();
        DBG("consumer thread cleanup completed");

        return NULL;
}

/*
 * This thread manage application communication.
 */
static void *thread_manage_apps(void *data)
{
        int i, ret, pollfd, err = -1;
        uint32_t revents, nb_fd;
        struct lttng_poll_event events;

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

        rcu_register_thread();
        rcu_thread_online();

        health_register(HEALTH_TYPE_APP_MANAGE);

        if (testpoint(thread_manage_apps)) {
                goto error_testpoint;
        }

        health_code_update();

        ret = sessiond_set_thread_pollset(&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;
        }

        if (testpoint(thread_manage_apps_before_loop)) {
                goto error;
        }

        health_code_update();

        while (1) {
                DBG("Apps thread polling on %d fds", LTTNG_POLL_GETNB(&events));

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

                nb_fd = ret;

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

                        health_code_update();

                        /* Thread quit pipe has been closed. Killing thread. */
                        ret = sessiond_check_thread_quit_pipe(pollfd, revents);
                        if (ret) {
                                err = 0;
                                goto exit;
                        }

                        /* 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) {
                                        int sock;

                                        /* Empty pipe */
                                        do {
                                                ret = read(apps_cmd_pipe[0], &sock, sizeof(sock));
                                        } while (ret < 0 && errno == EINTR);
                                        if (ret < 0 || ret < sizeof(sock)) {
                                                PERROR("read apps cmd pipe");
                                                goto error;
                                        }

                                        health_code_update();

                                        /*
                                         * We only monitor the error events of the socket. This
                                         * thread does not handle any incoming data from UST
                                         * (POLLIN).
                                         */
                                        ret = lttng_poll_add(&events, sock,
                                                        LPOLLERR | LPOLLHUP | LPOLLRDHUP);
                                        if (ret < 0) {
                                                goto error;
                                        }

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

                        health_code_update();
                }
        }

exit:
error:
        lttng_poll_clean(&events);
error_poll_create:
error_testpoint:
        utils_close_pipe(apps_cmd_pipe);
        apps_cmd_pipe[0] = apps_cmd_pipe[1] = -1;

        /*
         * We don't clean the UST app hash table here since already registered
         * applications can still be controlled so let them be until the session
         * daemon dies or the applications stop.
         */

        if (err) {
                health_error();
                ERR("Health error occurred in %s", __func__);
        }
        health_unregister();
        DBG("Application communication apps thread cleanup complete");
        rcu_thread_offline();
        rcu_unregister_thread();
        return NULL;
}

/*
 * Send a socket to a thread This is called from the dispatch UST registration
 * thread once all sockets are set for the application.
 *
 * The sock value can be invalid, we don't really care, the thread will handle
 * it and make the necessary cleanup if so.
 *
 * On success, return 0 else a negative value being the errno message of the
 * write().
 */
static int send_socket_to_thread(int fd, int sock)
{
        int ret;

        /*
         * It's possible that the FD is set as invalid with -1 concurrently just
         * before calling this function being a shutdown state of the thread.
         */
        if (fd < 0) {
                ret = -EBADF;
                goto error;
        }

        do {
                ret = write(fd, &sock, sizeof(sock));
        } while (ret < 0 && errno == EINTR);
        if (ret < 0 || ret != sizeof(sock)) {
                PERROR("write apps pipe %d", fd);
                if (ret < 0) {
                        ret = -errno;
                }
                goto error;
        }

        /* All good. Don't send back the write positive ret value. */
        ret = 0;
error:
        return ret;
}

/*
 * Sanitize the wait queue of the dispatch registration thread meaning removing
 * invalid nodes from it. This is to avoid memory leaks for the case the UST
 * notify socket is never received.
 */
static void sanitize_wait_queue(struct ust_reg_wait_queue *wait_queue)
{
        int ret, nb_fd = 0, i;
        unsigned int fd_added = 0;
        struct lttng_poll_event events;
        struct ust_reg_wait_node *wait_node = NULL, *tmp_wait_node;

        assert(wait_queue);

        lttng_poll_init(&events);

        /* Just skip everything for an empty queue. */
        if (!wait_queue->count) {
                goto end;
        }

        ret = lttng_poll_create(&events, wait_queue->count, LTTNG_CLOEXEC);
        if (ret < 0) {
                goto error_create;
        }

        cds_list_for_each_entry_safe(wait_node, tmp_wait_node,
                        &wait_queue->head, head) {
                assert(wait_node->app);
                ret = lttng_poll_add(&events, wait_node->app->sock,
                                LPOLLHUP | LPOLLERR);
                if (ret < 0) {
                        goto error;
                }

                fd_added = 1;
        }

        if (!fd_added) {
                goto end;
        }

        /*
         * Poll but don't block so we can quickly identify the faulty events and
         * clean them afterwards from the wait queue.
         */
        ret = lttng_poll_wait(&events, 0);
        if (ret < 0) {
                goto error;
        }
        nb_fd = ret;

        for (i = 0; i < nb_fd; i++) {
                /* Get faulty FD. */
                uint32_t revents = LTTNG_POLL_GETEV(&events, i);
                int pollfd = LTTNG_POLL_GETFD(&events, i);

                cds_list_for_each_entry_safe(wait_node, tmp_wait_node,
                                &wait_queue->head, head) {
                        if (pollfd == wait_node->app->sock &&
                                        (revents & (LPOLLHUP | LPOLLERR))) {
                                cds_list_del(&wait_node->head);
                                wait_queue->count--;
                                ust_app_destroy(wait_node->app);
                                free(wait_node);
                                break;
                        }
                }
        }

        if (nb_fd > 0) {
                DBG("Wait queue sanitized, %d node were cleaned up", nb_fd);
        }

end:
        lttng_poll_clean(&events);
        return;

error:
        lttng_poll_clean(&events);
error_create:
        ERR("Unable to sanitize wait queue");
        return;
}

/*
 * Dispatch request from the registration threads to the application
 * communication thread.
 */
static void *thread_dispatch_ust_registration(void *data)
{
        int ret, err = -1;
        struct cds_wfq_node *node;
        struct ust_command *ust_cmd = NULL;
        struct ust_reg_wait_node *wait_node = NULL, *tmp_wait_node;
        struct ust_reg_wait_queue wait_queue = {
                .count = 0,
        };

        health_register(HEALTH_TYPE_APP_REG_DISPATCH);

        health_code_update();

        CDS_INIT_LIST_HEAD(&wait_queue.head);

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

        while (!CMM_LOAD_SHARED(dispatch_thread_exit)) {
                health_code_update();

                /* Atomically prepare the queue futex */
                futex_nto1_prepare(&ust_cmd_queue.futex);

                do {
                        struct ust_app *app = NULL;
                        ust_cmd = NULL;

                        /*
                         * Make sure we don't have node(s) that have hung up before receiving
                         * the notify socket. This is to clean the list in order to avoid
                         * memory leaks from notify socket that are never seen.
                         */
                        sanitize_wait_queue(&wait_queue);

                        health_code_update();
                        /* 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);

                        if (ust_cmd->reg_msg.type == USTCTL_SOCKET_CMD) {
                                wait_node = zmalloc(sizeof(*wait_node));
                                if (!wait_node) {
                                        PERROR("zmalloc wait_node dispatch");
                                        ret = close(ust_cmd->sock);
                                        if (ret < 0) {
                                                PERROR("close ust sock dispatch %d", ust_cmd->sock);
                                        }
                                        lttng_fd_put(LTTNG_FD_APPS, 1);
                                        free(ust_cmd);
                                        goto error;
                                }
                                CDS_INIT_LIST_HEAD(&wait_node->head);

                                /* Create application object if socket is CMD. */
                                wait_node->app = ust_app_create(&ust_cmd->reg_msg,
                                                ust_cmd->sock);
                                if (!wait_node->app) {
                                        ret = close(ust_cmd->sock);
                                        if (ret < 0) {
                                                PERROR("close ust sock dispatch %d", ust_cmd->sock);
                                        }
                                        lttng_fd_put(LTTNG_FD_APPS, 1);
                                        free(wait_node);
                                        free(ust_cmd);
                                        continue;
                                }
                                /*
                                 * Add application to the wait queue so we can set the notify
                                 * socket before putting this object in the global ht.
                                 */
                                cds_list_add(&wait_node->head, &wait_queue.head);
                                wait_queue.count++;

                                free(ust_cmd);
                                /*
                                 * We have to continue here since we don't have the notify
                                 * socket and the application MUST be added to the hash table
                                 * only at that moment.
                                 */
                                continue;
                        } else {
                                /*
                                 * Look for the application in the local wait queue and set the
                                 * notify socket if found.
                                 */
                                cds_list_for_each_entry_safe(wait_node, tmp_wait_node,
                                                &wait_queue.head, head) {
                                        health_code_update();
                                        if (wait_node->app->pid == ust_cmd->reg_msg.pid) {
                                                wait_node->app->notify_sock = ust_cmd->sock;
                                                cds_list_del(&wait_node->head);
                                                wait_queue.count--;
                                                app = wait_node->app;
                                                free(wait_node);
                                                DBG3("UST app notify socket %d is set", ust_cmd->sock);
                                                break;
                                        }
                                }

                                /*
                                 * With no application at this stage the received socket is
                                 * basically useless so close it before we free the cmd data
                                 * structure for good.
                                 */
                                if (!app) {
                                        ret = close(ust_cmd->sock);
                                        if (ret < 0) {
                                                PERROR("close ust sock dispatch %d", ust_cmd->sock);
                                        }
                                        lttng_fd_put(LTTNG_FD_APPS, 1);
                                }
                                free(ust_cmd);
                        }

                        if (app) {
                                /*
                                 * @session_lock_list
                                 *
                                 * Lock the global session list so from the register up to the
                                 * registration done message, no thread can see the application
                                 * and change its state.
                                 */
                                session_lock_list();
                                rcu_read_lock();

                                /*
                                 * Add application to the global hash table. This needs to be
                                 * done before the update to the UST registry can locate the
                                 * application.
                                 */
                                ust_app_add(app);

                                /* Set app version. This call will print an error if needed. */
                                (void) ust_app_version(app);

                                /* Send notify socket through the notify pipe. */
                                ret = send_socket_to_thread(apps_cmd_notify_pipe[1],
                                                app->notify_sock);
                                if (ret < 0) {
                                        rcu_read_unlock();
                                        session_unlock_list();
                                        /*
                                         * No notify thread, stop the UST tracing. However, this is
                                         * not an internal error of the this thread thus setting
                                         * the health error code to a normal exit.
                                         */
                                        err = 0;
                                        goto error;
                                }

                                /*
                                 * Update newly registered application with the tracing
                                 * registry info already enabled information.
                                 */
                                update_ust_app(app->sock);

                                /*
                                 * Don't care about return value. Let the manage apps threads
                                 * handle app unregistration upon socket close.
                                 */
                                (void) ust_app_register_done(app->sock);

                                /*
                                 * Even if the application socket has been closed, send the app
                                 * to the thread and unregistration will take place at that
                                 * place.
                                 */
                                ret = send_socket_to_thread(apps_cmd_pipe[1], app->sock);
                                if (ret < 0) {
                                        rcu_read_unlock();
                                        session_unlock_list();
                                        /*
                                         * No apps. thread, stop the UST tracing. However, this is
                                         * not an internal error of the this thread thus setting
                                         * the health error code to a normal exit.
                                         */
                                        err = 0;
                                        goto error;
                                }

                                rcu_read_unlock();
                                session_unlock_list();
                        }
                } while (node != NULL);

                health_poll_entry();
                /* Futex wait on queue. Blocking call on futex() */
                futex_nto1_wait(&ust_cmd_queue.futex);
                health_poll_exit();
        }
        /* Normal exit, no error */
        err = 0;

error:
        /* Clean up wait queue. */
        cds_list_for_each_entry_safe(wait_node, tmp_wait_node,
                        &wait_queue.head, head) {
                cds_list_del(&wait_node->head);
                wait_queue.count--;
                free(wait_node);
        }

        DBG("Dispatch thread dying");
        if (err) {
                health_error();
                ERR("Health error occurred in %s", __func__);
        }
        health_unregister();
        return NULL;
}

/*
 * This thread manage application registration.
 */
static void *thread_registration_apps(void *data)
{
        int sock = -1, i, ret, pollfd, err = -1;
        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");

        health_register(HEALTH_TYPE_APP_REG);

        if (testpoint(thread_registration_apps)) {
                goto error_testpoint;
        }

        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 = sessiond_set_thread_pollset(&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");

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

                nb_fd = ret;

                for (i = 0; i < nb_fd; i++) {
                        health_code_update();

                        /* 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 = sessiond_check_thread_quit_pipe(pollfd, revents);
                        if (ret) {
                                err = 0;
                                goto exit;
                        }

                        /* 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;
                                        }

                                        /*
                                         * Set socket timeout for both receiving and ending.
                                         * app_socket_timeout is in seconds, whereas
                                         * lttcomm_setsockopt_rcv_timeout and
                                         * lttcomm_setsockopt_snd_timeout expect msec as
                                         * parameter.
                                         */
                                        (void) lttcomm_setsockopt_rcv_timeout(sock,
                                                        app_socket_timeout);
                                        (void) lttcomm_setsockopt_snd_timeout(sock,
                                                        app_socket_timeout);

                                        /*
                                         * Set the CLOEXEC flag. Return code is useless because
                                         * either way, the show must go on.
                                         */
                                        (void) utils_set_fd_cloexec(sock);

                                        /* 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;
                                        }

                                        health_code_update();
                                        ret = ust_app_recv_registration(sock, &ust_cmd->reg_msg);
                                        if (ret < 0) {
                                                free(ust_cmd);
                                                /* Close socket of the application. */
                                                ret = close(sock);
                                                if (ret) {
                                                        PERROR("close");
                                                }
                                                lttng_fd_put(LTTNG_FD_APPS, 1);
                                                sock = -1;
                                                continue;
                                        }
                                        health_code_update();

                                        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);
                                }
                        }
                }
        }

exit:
error:
        if (err) {
                health_error();
                ERR("Health error occurred in %s", __func__);
        }

        /* 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:
error_testpoint:
        DBG("UST Registration thread cleanup complete");
        health_unregister();

        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, clock_ret;
        struct timespec timeout;

        /* Make sure we set the readiness flag to 0 because we are NOT ready */
        consumer_data->consumer_thread_is_ready = 0;

        /* Setup pthread condition */
        ret = pthread_condattr_init(&consumer_data->condattr);
        if (ret != 0) {
                errno = ret;
                PERROR("pthread_condattr_init consumer data");
                goto error;
        }

        /*
         * Set the monotonic clock in order to make sure we DO NOT jump in time
         * between the clock_gettime() call and the timedwait call. See bug #324
         * for a more details and how we noticed it.
         */
        ret = pthread_condattr_setclock(&consumer_data->condattr, CLOCK_MONOTONIC);
        if (ret != 0) {
                errno = ret;
                PERROR("pthread_condattr_setclock consumer data");
                goto error;
        }

        ret = pthread_cond_init(&consumer_data->cond, &consumer_data->condattr);
        if (ret != 0) {
                errno = ret;
                PERROR("pthread_cond_init consumer data");
                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;
        }

        /* We are about to wait on a pthread condition */
        pthread_mutex_lock(&consumer_data->cond_mutex);

        /* Get time for sem_timedwait absolute timeout */
        clock_ret = clock_gettime(CLOCK_MONOTONIC, &timeout);
        /*
         * Set the timeout for the condition timed wait even if the clock gettime
         * call fails since we might loop on that call and we want to avoid to
         * increment the timeout too many times.
         */
        timeout.tv_sec += DEFAULT_SEM_WAIT_TIMEOUT;

        /*
         * The following loop COULD be skipped in some conditions so this is why we
         * set ret to 0 in order to make sure at least one round of the loop is
         * done.
         */
        ret = 0;

        /*
         * Loop until the condition is reached or when a timeout is reached. Note
         * that the pthread_cond_timedwait(P) man page specifies that EINTR can NOT
         * be returned but the pthread_cond(3), from the glibc-doc, says that it is
         * possible. This loop does not take any chances and works with both of
         * them.
         */
        while (!consumer_data->consumer_thread_is_ready && ret != ETIMEDOUT) {
                if (clock_ret < 0) {
                        PERROR("clock_gettime spawn consumer");
                        /* Infinite wait for the consumerd thread to be ready */
                        ret = pthread_cond_wait(&consumer_data->cond,
                                        &consumer_data->cond_mutex);
                } else {
                        ret = pthread_cond_timedwait(&consumer_data->cond,
                                        &consumer_data->cond_mutex, &timeout);
                }
        }

        /* Release the pthread condition */
        pthread_mutex_unlock(&consumer_data->cond_mutex);

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

        pthread_mutex_lock(&consumer_data->pid_mutex);
        if (consumer_data->pid == 0) {
                ERR("Consumerd 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;

        /* Consumer pid must be a real one. */
        if (consumer_data->pid > 0) {
                int ret;
                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;
                                        free(tmpnew);
                                        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;
                                        free(tmpnew);
                                        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;

        /*
         * Set the listen() state on the socket since there is a possible race
         * between the exec() of the consumer daemon and this call if place in the
         * consumer thread. See bug #366 for more details.
         */
        ret = lttcomm_listen_unix_sock(consumer_data->err_sock);
        if (ret < 0) {
                goto error;
        }

        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:
        /* Cleanup already created sockets on error. */
        if (consumer_data->err_sock >= 0) {
                int err;

                err = close(consumer_data->err_sock);
                if (err < 0) {
                        PERROR("close consumer data error socket");
                }
        }
        return ret;
}

/*
 * Compute health status of each consumer. If one of them is zero (bad
 * state), we return 0.
 */
static int check_consumer_health(void)
{
        int ret;

        ret = health_check_state(HEALTH_TYPE_CONSUMER);

        DBG3("Health consumer check %d", ret);

        return ret;
}

/*
 * 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 = kernel_validate_version(kernel_tracer_fd);
        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 LTTNG_ERR_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 LTTNG_ERR_NEED_ROOT_SESSIOND;
        } else {
                return LTTNG_ERR_KERN_NA;
        }
}


/*
 * 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.
 *
 * Should *NOT* be called with RCU read-side lock held.
 */
static int copy_session_consumer(int domain, struct ltt_session *session)
{
        int ret;
        const char *dir_name;
        struct consumer_output *consumer;

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

        switch (domain) {
        case LTTNG_DOMAIN_KERNEL:
                DBG3("Copying tracing session consumer output in kernel session");
                /*
                 * XXX: We should audit the session creation and what this function
                 * does "extra" in order to avoid a destroy since this function is used
                 * in the domain session creation (kernel and ust) only. Same for UST
                 * domain.
                 */
                if (session->kernel_session->consumer) {
                        consumer_destroy_output(session->kernel_session->consumer);
                }
                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");
                if (session->ust_session->consumer) {
                        consumer_destroy_output(session->ust_session->consumer);
                }
                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 = LTTNG_ERR_UNKNOWN_DOMAIN;
                goto error;
        }

        /* Append correct directory to subdir */
        strncat(consumer->subdir, dir_name,
                        sizeof(consumer->subdir) - strlen(consumer->subdir) - 1);
        DBG3("Copy session consumer subdir %s", consumer->subdir);

        ret = LTTNG_OK;

error:
        return ret;
}

/*
 * Create an UST session and add it to the session ust list.
 *
 * Should *NOT* be called with RCU read-side lock held.
 */
static int create_ust_session(struct ltt_session *session,
                struct lttng_domain *domain)
{
        int ret;
        struct ltt_ust_session *lus = NULL;

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

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

        DBG("Creating UST session");

        lus = trace_ust_create_session(session->id);
        if (lus == NULL) {
                ret = LTTNG_ERR_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 != LTTNG_OK) {
                goto error;
        }

        return LTTNG_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 = LTTNG_ERR_KERN_SESS_FAIL;
                goto error;
        }

        /* Code flow safety */
        assert(session->kernel_session);

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

        /* Create directory(ies) on local filesystem. */
        if (session->kernel_session->consumer->type == CONSUMER_DST_LOCAL &&
                        strlen(session->kernel_session->consumer->dst.trace_path) > 0) {
                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 LTTNG_OK;

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

/*
 * 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;
}

/*
 * Process the command requested by the lttng client within the command
 * context structure. This function make sure that the return structure (llm)
 * is set and ready for transmission before returning.
 *
 * Return any error encountered or 0 for success.
 *
 * "sock" is only used for special-case var. len data.
 *
 * Should *NOT* be called with RCU read-side lock held.
 */
static int process_client_msg(struct command_ctx *cmd_ctx, int sock,
                int *sock_error)
{
        int ret = LTTNG_OK;
        int need_tracing_session = 1;
        int need_domain;

        DBG("Processing client command %d", cmd_ctx->lsm->cmd_type);

        *sock_error = 0;

        switch (cmd_ctx->lsm->cmd_type) {
        case LTTNG_CREATE_SESSION:
        case LTTNG_DESTROY_SESSION:
        case LTTNG_LIST_SESSIONS:
        case LTTNG_LIST_DOMAINS:
        case LTTNG_START_TRACE:
        case LTTNG_STOP_TRACE:
        case LTTNG_DATA_PENDING:
                need_domain = 0;
                break;
        default:
                need_domain = 1;
        }

        if (opt_no_kernel && need_domain
                        && cmd_ctx->lsm->domain.type == LTTNG_DOMAIN_KERNEL) {
                if (!is_root) {
                        ret = LTTNG_ERR_NEED_ROOT_SESSIOND;
                } else {
                        ret = LTTNG_ERR_KERN_NA;
                }
                goto error;
        }

        /* Deny register consumer if we already have a spawned consumer. */
        if (cmd_ctx->lsm->cmd_type == LTTNG_REGISTER_CONSUMER) {
                pthread_mutex_lock(&kconsumer_data.pid_mutex);
                if (kconsumer_data.pid > 0) {
                        ret = LTTNG_ERR_KERN_CONSUMER_FAIL;
                        pthread_mutex_unlock(&kconsumer_data.pid_mutex);
                        goto error;
                }
                pthread_mutex_unlock(&kconsumer_data.pid_mutex);
        }

        /*
         * Check for command that don't needs to allocate a returned payload. We do
         * this here so we don't have to make the call for no payload at each
         * command.
         */
        switch(cmd_ctx->lsm->cmd_type) {
        case LTTNG_LIST_SESSIONS:
        case LTTNG_LIST_TRACEPOINTS:
        case LTTNG_LIST_TRACEPOINT_FIELDS:
        case LTTNG_LIST_DOMAINS:
        case LTTNG_LIST_CHANNELS:
        case LTTNG_LIST_EVENTS:
                break;
        default:
                /* Setup lttng message with no payload */
                ret = setup_lttng_msg(cmd_ctx, 0);
                if (ret < 0) {
                        /* This label does not try to unlock the session */
                        goto init_setup_error;
                }
        }

        /* Commands that DO NOT need a session. */
        switch (cmd_ctx->lsm->cmd_type) {
        case LTTNG_CREATE_SESSION:
        case LTTNG_CALIBRATE:
        case LTTNG_LIST_SESSIONS:
        case LTTNG_LIST_TRACEPOINTS:
        case LTTNG_LIST_TRACEPOINT_FIELDS:
                need_tracing_session = 0;
                break;
        default:
                DBG("Getting session %s by name", cmd_ctx->lsm->session.name);
                /*
                 * We keep the session list lock across _all_ commands
                 * for now, because the per-session lock does not
                 * handle teardown properly.
                 */
                session_lock_list();
                cmd_ctx->session = session_find_by_name(cmd_ctx->lsm->session.name);
                if (cmd_ctx->session == NULL) {
                        ret = LTTNG_ERR_SESS_NOT_FOUND;
                        goto error;
                } else {
                        /* Acquire lock for the session */
                        session_lock(cmd_ctx->session);
                }
                break;
        }

        if (!need_domain) {
                goto skip_domain;
        }

        /*
         * Check domain type for specific "pre-action".
         */
        switch (cmd_ctx->lsm->domain.type) {
        case LTTNG_DOMAIN_KERNEL:
                if (!is_root) {
                        ret = LTTNG_ERR_NEED_ROOT_SESSIOND;
                        goto error;
                }

                /* Kernel tracer check */
                if (kernel_tracer_fd == -1) {
                        /* Basically, load kernel tracer modules */
                        ret = init_kernel_tracer();
                        if (ret != 0) {
                                goto error;
                        }
                }

                /* Consumer is in an ERROR state. Report back to client */
                if (uatomic_read(&kernel_consumerd_state) == CONSUMER_ERROR) {
                        ret = LTTNG_ERR_NO_KERNCONSUMERD;
                        goto error;
                }

                /* Need a session for kernel command */
                if (need_tracing_session) {
                        if (cmd_ctx->session->kernel_session == NULL) {
                                ret = create_kernel_session(cmd_ctx->session);
                                if (ret < 0) {
                                        ret = LTTNG_ERR_KERN_SESS_FAIL;
                                        goto error;
                                }
                        }

                        /* Start the kernel consumer daemon */
                        pthread_mutex_lock(&kconsumer_data.pid_mutex);
                        if (kconsumer_data.pid == 0 &&
                                        cmd_ctx->lsm->cmd_type != LTTNG_REGISTER_CONSUMER) {
                                pthread_mutex_unlock(&kconsumer_data.pid_mutex);
                                ret = start_consumerd(&kconsumer_data);
                                if (ret < 0) {
                                        ret = LTTNG_ERR_KERN_CONSUMER_FAIL;
                                        goto error;
                                }
                                uatomic_set(&kernel_consumerd_state, CONSUMER_STARTED);
                        } else {
                                pthread_mutex_unlock(&kconsumer_data.pid_mutex);
                        }

                        /*
                         * The consumer was just spawned so we need to add the socket to
                         * the consumer output of the session if exist.
                         */
                        ret = consumer_create_socket(&kconsumer_data,
                                        cmd_ctx->session->kernel_session->consumer);
                        if (ret < 0) {
                                goto error;
                        }
                }

                break;
        case LTTNG_DOMAIN_UST:
        {
                if (!ust_app_supported()) {
                        ret = LTTNG_ERR_NO_UST;
                        goto error;
                }
                /* Consumer is in an ERROR state. Report back to client */
                if (uatomic_read(&ust_consumerd_state) == CONSUMER_ERROR) {
                        ret = LTTNG_ERR_NO_USTCONSUMERD;
                        goto error;
                }

                if (need_tracing_session) {
                        /* Create UST session if none exist. */
                        if (cmd_ctx->session->ust_session == NULL) {
                                ret = create_ust_session(cmd_ctx->session,
                                                &cmd_ctx->lsm->domain);
                                if (ret != LTTNG_OK) {
                                        goto error;
                                }
                        }

                        /* Start the UST consumer daemons */
                        /* 64-bit */
                        pthread_mutex_lock(&ustconsumer64_data.pid_mutex);
                        if (consumerd64_bin[0] != '\0' &&
                                        ustconsumer64_data.pid == 0 &&
                                        cmd_ctx->lsm->cmd_type != LTTNG_REGISTER_CONSUMER) {
                                pthread_mutex_unlock(&ustconsumer64_data.pid_mutex);
                                ret = start_consumerd(&ustconsumer64_data);
                                if (ret < 0) {
                                        ret = LTTNG_ERR_UST_CONSUMER64_FAIL;
                                        uatomic_set(&ust_consumerd64_fd, -EINVAL);
                                        goto error;
                                }

                                uatomic_set(&ust_consumerd64_fd, ustconsumer64_data.cmd_sock);
                                uatomic_set(&ust_consumerd_state, CONSUMER_STARTED);
                        } else {
                                pthread_mutex_unlock(&ustconsumer64_data.pid_mutex);
                        }

                        /*
                         * Setup socket for consumer 64 bit. No need for atomic access
                         * since it was set above and can ONLY be set in this thread.
                         */
                        ret = consumer_create_socket(&ustconsumer64_data,
                                        cmd_ctx->session->ust_session->consumer);
                        if (ret < 0) {
                                goto error;
                        }

                        /* 32-bit */
                        if (consumerd32_bin[0] != '\0' &&
                                        ustconsumer32_data.pid == 0 &&
                                        cmd_ctx->lsm->cmd_type != LTTNG_REGISTER_CONSUMER) {
                                pthread_mutex_unlock(&ustconsumer32_data.pid_mutex);
                                ret = start_consumerd(&ustconsumer32_data);
                                if (ret < 0) {
                                        ret = LTTNG_ERR_UST_CONSUMER32_FAIL;
                                        uatomic_set(&ust_consumerd32_fd, -EINVAL);
                                        goto error;
                                }

                                uatomic_set(&ust_consumerd32_fd, ustconsumer32_data.cmd_sock);
                                uatomic_set(&ust_consumerd_state, CONSUMER_STARTED);
                        } else {
                                pthread_mutex_unlock(&ustconsumer32_data.pid_mutex);
                        }

                        /*
                         * Setup socket for consumer 64 bit. No need for atomic access
                         * since it was set above and can ONLY be set in this thread.
                         */
                        ret = consumer_create_socket(&ustconsumer32_data,
                                        cmd_ctx->session->ust_session->consumer);
                        if (ret < 0) {
                                goto error;
                        }
                }
                break;
        }
        default:
                break;
        }
skip_domain:

        /* Validate consumer daemon state when start/stop trace command */
        if (cmd_ctx->lsm->cmd_type == LTTNG_START_TRACE ||
                        cmd_ctx->lsm->cmd_type == LTTNG_STOP_TRACE) {
                switch (cmd_ctx->lsm->domain.type) {
                case LTTNG_DOMAIN_UST:
                        if (uatomic_read(&ust_consumerd_state) != CONSUMER_STARTED) {
                                ret = LTTNG_ERR_NO_USTCONSUMERD;
                                goto error;
                        }
                        break;
                case LTTNG_DOMAIN_KERNEL:
                        if (uatomic_read(&kernel_consumerd_state) != CONSUMER_STARTED) {
                                ret = LTTNG_ERR_NO_KERNCONSUMERD;
                                goto error;
                        }
                        break;
                }
        }

        /*
         * Check that the UID or GID match that of the tracing session.
         * The root user can interact with all sessions.
         */
        if (need_tracing_session) {
                if (!session_access_ok(cmd_ctx->session,
                                LTTNG_SOCK_GET_UID_CRED(&cmd_ctx->creds),
                                LTTNG_SOCK_GET_GID_CRED(&cmd_ctx->creds))) {
                        ret = LTTNG_ERR_EPERM;
                        goto error;
                }
        }

        /*
         * Send relayd information to consumer as soon as we have a domain and a
         * session defined.
         */
        if (cmd_ctx->session && need_domain) {
                /*
                 * Setup relayd if not done yet. If the relayd information was already
                 * sent to the consumer, this call will gracefully return.
                 */
                ret = cmd_setup_relayd(cmd_ctx->session);
                if (ret != LTTNG_OK) {
                        goto error;
                }
        }

        /* Process by command type */
        switch (cmd_ctx->lsm->cmd_type) {
        case LTTNG_ADD_CONTEXT:
        {
                ret = cmd_add_context(cmd_ctx->session, cmd_ctx->lsm->domain.type,
                                cmd_ctx->lsm->u.context.channel_name,
                                &cmd_ctx->lsm->u.context.ctx, kernel_poll_pipe[1]);
                break;
        }
        case LTTNG_DISABLE_CHANNEL:
        {
                ret = cmd_disable_channel(cmd_ctx->session, cmd_ctx->lsm->domain.type,
                                cmd_ctx->lsm->u.disable.channel_name);
                break;
        }
        case LTTNG_DISABLE_EVENT:
        {
                ret = cmd_disable_event(cmd_ctx->session, cmd_ctx->lsm->domain.type,
                                cmd_ctx->lsm->u.disable.channel_name,
                                cmd_ctx->lsm->u.disable.name);
                break;
        }
        case LTTNG_DISABLE_ALL_EVENT:
        {
                DBG("Disabling all events");

                ret = cmd_disable_event_all(cmd_ctx->session, cmd_ctx->lsm->domain.type,
                                cmd_ctx->lsm->u.disable.channel_name);
                break;
        }
        case LTTNG_ENABLE_CHANNEL:
        {
                ret = cmd_enable_channel(cmd_ctx->session, &cmd_ctx->lsm->domain,
                                &cmd_ctx->lsm->u.channel.chan, kernel_poll_pipe[1]);
                break;
        }
        case LTTNG_ENABLE_EVENT:
        {
                ret = cmd_enable_event(cmd_ctx->session, &cmd_ctx->lsm->domain,
                                cmd_ctx->lsm->u.enable.channel_name,
                                &cmd_ctx->lsm->u.enable.event, NULL, kernel_poll_pipe[1]);
                break;
        }
        case LTTNG_ENABLE_ALL_EVENT:
        {
                DBG("Enabling all events");

                ret = cmd_enable_event_all(cmd_ctx->session, &cmd_ctx->lsm->domain,
                                cmd_ctx->lsm->u.enable.channel_name,
                                cmd_ctx->lsm->u.enable.event.type, NULL, kernel_poll_pipe[1]);
                break;
        }
        case LTTNG_LIST_TRACEPOINTS:
        {
                struct lttng_event *events;
                ssize_t nb_events;

                nb_events = cmd_list_tracepoints(cmd_ctx->lsm->domain.type, &events);
                if (nb_events < 0) {
                        /* Return value is a negative lttng_error_code. */
                        ret = -nb_events;
                        goto error;
                }

                /*
                 * Setup lttng message with payload size set to the event list size in
                 * bytes and then copy list into the llm payload.
                 */
                ret = setup_lttng_msg(cmd_ctx, sizeof(struct lttng_event) * nb_events);
                if (ret < 0) {
                        free(events);
                        goto setup_error;
                }

                /* Copy event list into message payload */
                memcpy(cmd_ctx->llm->payload, events,
                                sizeof(struct lttng_event) * nb_events);

                free(events);

                ret = LTTNG_OK;
                break;
        }
        case LTTNG_LIST_TRACEPOINT_FIELDS:
        {
                struct lttng_event_field *fields;
                ssize_t nb_fields;

                nb_fields = cmd_list_tracepoint_fields(cmd_ctx->lsm->domain.type,
                                &fields);
                if (nb_fields < 0) {
                        /* Return value is a negative lttng_error_code. */
                        ret = -nb_fields;
                        goto error;
                }

                /*
                 * Setup lttng message with payload size set to the event list size in
                 * bytes and then copy list into the llm payload.
                 */
                ret = setup_lttng_msg(cmd_ctx,
                                sizeof(struct lttng_event_field) * nb_fields);
                if (ret < 0) {
                        free(fields);
                        goto setup_error;
                }

                /* Copy event list into message payload */
                memcpy(cmd_ctx->llm->payload, fields,
                                sizeof(struct lttng_event_field) * nb_fields);

                free(fields);

                ret = LTTNG_OK;
                break;
        }
        case LTTNG_SET_CONSUMER_URI:
        {
                size_t nb_uri, len;
                struct lttng_uri *uris;

                nb_uri = cmd_ctx->lsm->u.uri.size;
                len = nb_uri * sizeof(struct lttng_uri);

                if (nb_uri == 0) {
                        ret = LTTNG_ERR_INVALID;
                        goto error;
                }

                uris = zmalloc(len);
                if (uris == NULL) {
                        ret = LTTNG_ERR_FATAL;
                        goto error;
                }

                /* Receive variable len data */
                DBG("Receiving %zu URI(s) from client ...", nb_uri);
                ret = lttcomm_recv_unix_sock(sock, uris, len);
                if (ret <= 0) {
                        DBG("No URIs received from client... continuing");
                        *sock_error = 1;
                        ret = LTTNG_ERR_SESSION_FAIL;
                        free(uris);
                        goto error;
                }

                ret = cmd_set_consumer_uri(cmd_ctx->lsm->domain.type, cmd_ctx->session,
                                nb_uri, uris);
                if (ret != LTTNG_OK) {
                        free(uris);
                        goto error;
                }

                /*
                 * XXX: 0 means that this URI should be applied on the session. Should
                 * be a DOMAIN enuam.
                 */
                if (cmd_ctx->lsm->domain.type == 0) {
                        /* Add the URI for the UST session if a consumer is present. */
                        if (cmd_ctx->session->ust_session &&
                                        cmd_ctx->session->ust_session->consumer) {
                                ret = cmd_set_consumer_uri(LTTNG_DOMAIN_UST, cmd_ctx->session,
                                                nb_uri, uris);
                        } else if (cmd_ctx->session->kernel_session &&
                                        cmd_ctx->session->kernel_session->consumer) {
                                ret = cmd_set_consumer_uri(LTTNG_DOMAIN_KERNEL,
                                                cmd_ctx->session, nb_uri, uris);
                        }
                }

                free(uris);

                break;
        }
        case LTTNG_START_TRACE:
        {
                ret = cmd_start_trace(cmd_ctx->session);
                break;
        }
        case LTTNG_STOP_TRACE:
        {
                ret = cmd_stop_trace(cmd_ctx->session);
                break;
        }
        case LTTNG_CREATE_SESSION:
        {
                size_t nb_uri, len;
                struct lttng_uri *uris = NULL;

                nb_uri = cmd_ctx->lsm->u.uri.size;
                len = nb_uri * sizeof(struct lttng_uri);

                if (nb_uri > 0) {
                        uris = zmalloc(len);
                        if (uris == NULL) {
                                ret = LTTNG_ERR_FATAL;
                                goto error;
                        }

                        /* Receive variable len data */
                        DBG("Waiting for %zu URIs from client ...", nb_uri);
                        ret = lttcomm_recv_unix_sock(sock, uris, len);
                        if (ret <= 0) {
                                DBG("No URIs received from client... continuing");
                                *sock_error = 1;
                                ret = LTTNG_ERR_SESSION_FAIL;
                                free(uris);
                                goto error;
                        }

                        if (nb_uri == 1 && uris[0].dtype != LTTNG_DST_PATH) {
                                DBG("Creating session with ONE network URI is a bad call");
                                ret = LTTNG_ERR_SESSION_FAIL;
                                free(uris);
                                goto error;
                        }
                }

                ret = cmd_create_session_uri(cmd_ctx->lsm->session.name, uris, nb_uri,
                        &cmd_ctx->creds);

                free(uris);

                break;
        }
        case LTTNG_DESTROY_SESSION:
        {
                ret = cmd_destroy_session(cmd_ctx->session, kernel_poll_pipe[1]);

                /* Set session to NULL so we do not unlock it after free. */
                cmd_ctx->session = NULL;
                break;
        }
        case LTTNG_LIST_DOMAINS:
        {
                ssize_t nb_dom;
                struct lttng_domain *domains;

                nb_dom = cmd_list_domains(cmd_ctx->session, &domains);
                if (nb_dom < 0) {
                        /* Return value is a negative lttng_error_code. */
                        ret = -nb_dom;
                        goto error;
                }

                ret = setup_lttng_msg(cmd_ctx, nb_dom * sizeof(struct lttng_domain));
                if (ret < 0) {
                        free(domains);
                        goto setup_error;
                }

                /* Copy event list into message payload */
                memcpy(cmd_ctx->llm->payload, domains,
                                nb_dom * sizeof(struct lttng_domain));

                free(domains);

                ret = LTTNG_OK;
                break;
        }
        case LTTNG_LIST_CHANNELS:
        {
                int nb_chan;
                struct lttng_channel *channels;

                nb_chan = cmd_list_channels(cmd_ctx->lsm->domain.type,
                                cmd_ctx->session, &channels);
                if (nb_chan < 0) {
                        /* Return value is a negative lttng_error_code. */
                        ret = -nb_chan;
                        goto error;
                }

                ret = setup_lttng_msg(cmd_ctx, nb_chan * sizeof(struct lttng_channel));
                if (ret < 0) {
                        free(channels);
                        goto setup_error;
                }

                /* Copy event list into message payload */
                memcpy(cmd_ctx->llm->payload, channels,
                                nb_chan * sizeof(struct lttng_channel));

                free(channels);

                ret = LTTNG_OK;
                break;
        }
        case LTTNG_LIST_EVENTS:
        {
                ssize_t nb_event;
                struct lttng_event *events = NULL;

                nb_event = cmd_list_events(cmd_ctx->lsm->domain.type, cmd_ctx->session,
                                cmd_ctx->lsm->u.list.channel_name, &events);
                if (nb_event < 0) {
                        /* Return value is a negative lttng_error_code. */
                        ret = -nb_event;
                        goto error;
                }

                ret = setup_lttng_msg(cmd_ctx, nb_event * sizeof(struct lttng_event));
                if (ret < 0) {
                        free(events);
                        goto setup_error;
                }

                /* Copy event list into message payload */
                memcpy(cmd_ctx->llm->payload, events,
                                nb_event * sizeof(struct lttng_event));

                free(events);

                ret = LTTNG_OK;
                break;
        }
        case LTTNG_LIST_SESSIONS:
        {
                unsigned int nr_sessions;

                session_lock_list();
                nr_sessions = lttng_sessions_count(
                                LTTNG_SOCK_GET_UID_CRED(&cmd_ctx->creds),
                                LTTNG_SOCK_GET_GID_CRED(&cmd_ctx->creds));

                ret = setup_lttng_msg(cmd_ctx, sizeof(struct lttng_session) * nr_sessions);
                if (ret < 0) {
                        session_unlock_list();
                        goto setup_error;
                }

                /* Filled the session array */
                cmd_list_lttng_sessions((struct lttng_session *)(cmd_ctx->llm->payload),
                        LTTNG_SOCK_GET_UID_CRED(&cmd_ctx->creds),
                        LTTNG_SOCK_GET_GID_CRED(&cmd_ctx->creds));

                session_unlock_list();

                ret = LTTNG_OK;
                break;
        }
        case LTTNG_CALIBRATE:
        {
                ret = cmd_calibrate(cmd_ctx->lsm->domain.type,
                                &cmd_ctx->lsm->u.calibrate);
                break;
        }
        case LTTNG_REGISTER_CONSUMER:
        {
                struct consumer_data *cdata;

                switch (cmd_ctx->lsm->domain.type) {
                case LTTNG_DOMAIN_KERNEL:
                        cdata = &kconsumer_data;
                        break;
                default:
                        ret = LTTNG_ERR_UND;
                        goto error;
                }

                ret = cmd_register_consumer(cmd_ctx->session, cmd_ctx->lsm->domain.type,
                                cmd_ctx->lsm->u.reg.path, cdata);
                break;
        }
        case LTTNG_ENABLE_EVENT_WITH_FILTER:
        {
                struct lttng_filter_bytecode *bytecode;

                if (cmd_ctx->lsm->u.enable.bytecode_len > LTTNG_FILTER_MAX_LEN) {
                        ret = LTTNG_ERR_FILTER_INVAL;
                        goto error;
                }
                if (cmd_ctx->lsm->u.enable.bytecode_len == 0) {
                        ret = LTTNG_ERR_FILTER_INVAL;
                        goto error;
                }
                bytecode = zmalloc(cmd_ctx->lsm->u.enable.bytecode_len);
                if (!bytecode) {
                        ret = LTTNG_ERR_FILTER_NOMEM;
                        goto error;
                }
                /* Receive var. len. data */
                DBG("Receiving var len data from client ...");
                ret = lttcomm_recv_unix_sock(sock, bytecode,
                                cmd_ctx->lsm->u.enable.bytecode_len);
                if (ret <= 0) {
                        DBG("Nothing recv() from client var len data... continuing");
                        *sock_error = 1;
                        ret = LTTNG_ERR_FILTER_INVAL;
                        goto error;
                }

                if (bytecode->len + sizeof(*bytecode)
                                != cmd_ctx->lsm->u.enable.bytecode_len) {
                        free(bytecode);
                        ret = LTTNG_ERR_FILTER_INVAL;
                        goto error;
                }

                ret = cmd_enable_event(cmd_ctx->session, &cmd_ctx->lsm->domain,
                                cmd_ctx->lsm->u.enable.channel_name,
                                &cmd_ctx->lsm->u.enable.event, bytecode, kernel_poll_pipe[1]);
                break;
        }
        case LTTNG_DATA_PENDING:
        {
                ret = cmd_data_pending(cmd_ctx->session);
                break;
        }
        default:
                ret = LTTNG_ERR_UND;
                break;
        }

error:
        if (cmd_ctx->llm == NULL) {
                DBG("Missing llm structure. Allocating one.");
                if (setup_lttng_msg(cmd_ctx, 0) < 0) {
                        goto setup_error;
                }
        }
        /* Set return code */
        cmd_ctx->llm->ret_code = ret;
setup_error:
        if (cmd_ctx->session) {
                session_unlock(cmd_ctx->session);
        }
        if (need_tracing_session) {
                session_unlock_list();
        }
init_setup_error:
        return ret;
}

/*
 * Thread managing health check socket.
 */
static void *thread_manage_health(void *data)
{
        int sock = -1, new_sock = -1, ret, i, pollfd, err = -1;
        uint32_t revents, nb_fd;
        struct lttng_poll_event events;
        struct lttcomm_health_msg msg;
        struct lttcomm_health_data reply;

        DBG("[thread] Manage health check started");

        rcu_register_thread();

        /* We might hit an error path before this is created. */
        lttng_poll_init(&events);

        /* Create unix socket */
        sock = lttcomm_create_unix_sock(health_unix_sock_path);
        if (sock < 0) {
                ERR("Unable to create health check Unix socket");
                ret = -1;
                goto error;
        }

        /*
         * Set the CLOEXEC flag. Return code is useless because either way, the
         * show must go on.
         */
        (void) utils_set_fd_cloexec(sock);

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

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

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

        while (1) {
                DBG("Health check ready");

                /* 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;
                }

                nb_fd = ret;

                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 = sessiond_check_thread_quit_pipe(pollfd, revents);
                        if (ret) {
                                err = 0;
                                goto exit;
                        }

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

                new_sock = lttcomm_accept_unix_sock(sock);
                if (new_sock < 0) {
                        goto error;
                }

                /*
                 * Set the CLOEXEC flag. Return code is useless because either way, the
                 * show must go on.
                 */
                (void) utils_set_fd_cloexec(new_sock);

                DBG("Receiving data from client for health...");
                ret = lttcomm_recv_unix_sock(new_sock, (void *)&msg, sizeof(msg));
                if (ret <= 0) {
                        DBG("Nothing recv() from client... continuing");
                        ret = close(new_sock);
                        if (ret) {
                                PERROR("close");
                        }
                        new_sock = -1;
                        continue;
                }

                rcu_thread_online();

                switch (msg.component) {
                case LTTNG_HEALTH_CMD:
                        reply.ret_code = health_check_state(HEALTH_TYPE_CMD);
                        break;
                case LTTNG_HEALTH_APP_MANAGE:
                        reply.ret_code = health_check_state(HEALTH_TYPE_APP_MANAGE);
                        break;
                case LTTNG_HEALTH_APP_REG:
                        reply.ret_code = health_check_state(HEALTH_TYPE_APP_REG);
                        break;
                case LTTNG_HEALTH_KERNEL:
                        reply.ret_code = health_check_state(HEALTH_TYPE_KERNEL);
                        break;
                case LTTNG_HEALTH_CONSUMER:
                        reply.ret_code = check_consumer_health();
                        break;
                case LTTNG_HEALTH_HT_CLEANUP:
                        reply.ret_code = health_check_state(HEALTH_TYPE_HT_CLEANUP);
                        break;
                case LTTNG_HEALTH_APP_MANAGE_NOTIFY:
                        reply.ret_code = health_check_state(HEALTH_TYPE_APP_MANAGE_NOTIFY);
                        break;
                case LTTNG_HEALTH_APP_REG_DISPATCH:
                        reply.ret_code = health_check_state(HEALTH_TYPE_APP_REG_DISPATCH);
                        break;
                case LTTNG_HEALTH_ALL:
                        reply.ret_code =
                                health_check_state(HEALTH_TYPE_APP_MANAGE) &&
                                health_check_state(HEALTH_TYPE_APP_REG) &&
                                health_check_state(HEALTH_TYPE_CMD) &&
                                health_check_state(HEALTH_TYPE_KERNEL) &&
                                check_consumer_health() &&
                                health_check_state(HEALTH_TYPE_HT_CLEANUP) &&
                                health_check_state(HEALTH_TYPE_APP_MANAGE_NOTIFY) &&
                                health_check_state(HEALTH_TYPE_APP_REG_DISPATCH);
                        break;
                default:
                        reply.ret_code = LTTNG_ERR_UND;
                        break;
                }

                /*
                 * Flip ret value since 0 is a success and 1 indicates a bad health for
                 * the client where in the sessiond it is the opposite. Again, this is
                 * just to make things easier for us poor developer which enjoy a lot
                 * lazyness.
                 */
                if (reply.ret_code == 0 || reply.ret_code == 1) {
                        reply.ret_code = !reply.ret_code;
                }

                DBG2("Health check return value %d", reply.ret_code);

                ret = send_unix_sock(new_sock, (void *) &reply, sizeof(reply));
                if (ret < 0) {
                        ERR("Failed to send health data back to client");
                }

                /* End of transmission */
                ret = close(new_sock);
                if (ret) {
                        PERROR("close");
                }
                new_sock = -1;
        }

exit:
error:
        if (err) {
                ERR("Health error occurred in %s", __func__);
        }
        DBG("Health check thread dying");
        unlink(health_unix_sock_path);
        if (sock >= 0) {
                ret = close(sock);
                if (ret) {
                        PERROR("close");
                }
        }

        lttng_poll_clean(&events);

        rcu_unregister_thread();
        return NULL;
}

/*
 * This thread manage all clients request using the unix client socket for
 * communication.
 */
static void *thread_manage_clients(void *data)
{
        int sock = -1, ret, i, pollfd, err = -1;
        int sock_error;
        uint32_t revents, nb_fd;
        struct command_ctx *cmd_ctx = NULL;
        struct lttng_poll_event events;

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

        rcu_register_thread();

        health_register(HEALTH_TYPE_CMD);

        if (testpoint(thread_manage_clients)) {
                goto error_testpoint;
        }

        health_code_update();

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

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

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

        /*
         * Notify parent pid that we are ready to accept command for client side.
         */
        if (opt_sig_parent) {
                kill(ppid, SIGUSR1);
        }

        if (testpoint(thread_manage_clients_before_loop)) {
                goto error;
        }

        health_code_update();

        while (1) {
                DBG("Accepting client command ...");

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

                nb_fd = ret;

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

                        health_code_update();

                        /* Thread quit pipe has been closed. Killing thread. */
                        ret = sessiond_check_thread_quit_pipe(pollfd, revents);
                        if (ret) {
                                err = 0;
                                goto exit;
                        }

                        /* Event on the registration socket */
                        if (pollfd == client_sock) {
                                if (revents & (LPOLLERR | LPOLLHUP | LPOLLRDHUP)) {
                                        ERR("Client socket poll error");
                                        goto error;
                                }
                        }
                }

                DBG("Wait for client response");

                health_code_update();

                sock = lttcomm_accept_unix_sock(client_sock);
                if (sock < 0) {
                        goto error;
                }

                /*
                 * Set the CLOEXEC flag. Return code is useless because either way, the
                 * show must go on.
                 */
                (void) utils_set_fd_cloexec(sock);

                /* Set socket option for credentials retrieval */
                ret = lttcomm_setsockopt_creds_unix_sock(sock);
                if (ret < 0) {
                        goto error;
                }

                /* Allocate context command to process the client request */
                cmd_ctx = zmalloc(sizeof(struct command_ctx));
                if (cmd_ctx == NULL) {
                        PERROR("zmalloc cmd_ctx");
                        goto error;
                }

                /* Allocate data buffer for reception */
                cmd_ctx->lsm = zmalloc(sizeof(struct lttcomm_session_msg));
                if (cmd_ctx->lsm == NULL) {
                        PERROR("zmalloc cmd_ctx->lsm");
                        goto error;
                }

                cmd_ctx->llm = NULL;
                cmd_ctx->session = NULL;

                health_code_update();

                /*
                 * Data is received from the lttng client. The struct
                 * lttcomm_session_msg (lsm) contains the command and data request of
                 * the client.
                 */
                DBG("Receiving data from client ...");
                ret = lttcomm_recv_creds_unix_sock(sock, cmd_ctx->lsm,
                                sizeof(struct lttcomm_session_msg), &cmd_ctx->creds);
                if (ret <= 0) {
                        DBG("Nothing recv() from client... continuing");
                        ret = close(sock);
                        if (ret) {
                                PERROR("close");
                        }
                        sock = -1;
                        clean_command_ctx(&cmd_ctx);
                        continue;
                }

                health_code_update();

                // TODO: Validate cmd_ctx including sanity check for
                // security purpose.

                rcu_thread_online();
                /*
                 * This function dispatch the work to the kernel or userspace tracer
                 * libs and fill the lttcomm_lttng_msg data structure of all the needed
                 * informations for the client. The command context struct contains
                 * everything this function may needs.
                 */
                ret = process_client_msg(cmd_ctx, sock, &sock_error);
                rcu_thread_offline();
                if (ret < 0) {
                        ret = close(sock);
                        if (ret) {
                                PERROR("close");
                        }
                        sock = -1;
                        /*
                         * TODO: Inform client somehow of the fatal error. At
                         * this point, ret < 0 means that a zmalloc failed
                         * (ENOMEM). Error detected but still accept
                         * command, unless a socket error has been
                         * detected.
                         */
                        clean_command_ctx(&cmd_ctx);
                        continue;
                }

                health_code_update();

                DBG("Sending response (size: %d, retcode: %s)",
                                cmd_ctx->lttng_msg_size,
                                lttng_strerror(-cmd_ctx->llm->ret_code));
                ret = send_unix_sock(sock, cmd_ctx->llm, cmd_ctx->lttng_msg_size);
                if (ret < 0) {
                        ERR("Failed to send data back to client");
                }

                /* End of transmission */
                ret = close(sock);
                if (ret) {
                        PERROR("close");
                }
                sock = -1;

                clean_command_ctx(&cmd_ctx);

                health_code_update();
        }

exit:
error:
        if (sock >= 0) {
                ret = close(sock);
                if (ret) {
                        PERROR("close");
                }
        }

        lttng_poll_clean(&events);
        clean_command_ctx(&cmd_ctx);

error_listen:
error_create_poll:
error_testpoint:
        unlink(client_unix_sock_path);
        if (client_sock >= 0) {
                ret = close(client_sock);
                if (ret) {
                        PERROR("close");
                }
        }

        if (err) {
                health_error();
                ERR("Health error occurred in %s", __func__);
        }

        health_unregister();

        DBG("Client thread dying");

        rcu_unregister_thread();
        return NULL;
}


/*
 * usage function on stderr
 */
static void usage(void)
{
        fprintf(stderr, "Usage: %s OPTIONS\n\nOptions:\n", progname);
        fprintf(stderr, "  -h, --help                         Display this usage.\n");
        fprintf(stderr, "  -c, --client-sock PATH             Specify path for the client unix socket\n");
        fprintf(stderr, "  -a, --apps-sock PATH               Specify path for apps unix socket\n");
        fprintf(stderr, "      --kconsumerd-err-sock PATH     Specify path for the kernel consumer error socket\n");
        fprintf(stderr, "      --kconsumerd-cmd-sock PATH     Specify path for the kernel consumer command socket\n");
        fprintf(stderr, "      --ustconsumerd32-err-sock PATH Specify path for the 32-bit UST consumer error socket\n");
        fprintf(stderr, "      --ustconsumerd64-err-sock PATH Specify path for the 64-bit UST consumer error socket\n");
        fprintf(stderr, "      --ustconsumerd32-cmd-sock PATH Specify path for the 32-bit UST consumer command socket\n");
        fprintf(stderr, "      --ustconsumerd64-cmd-sock PATH Specify path for the 64-bit UST consumer command socket\n");
        fprintf(stderr, "      --consumerd32-path PATH     Specify path for the 32-bit UST consumer daemon binary\n");
        fprintf(stderr, "      --consumerd32-libdir PATH   Specify path for the 32-bit UST consumer daemon libraries\n");
        fprintf(stderr, "      --consumerd64-path PATH     Specify path for the 64-bit UST consumer daemon binary\n");
        fprintf(stderr, "      --consumerd64-libdir PATH   Specify path for the 64-bit UST consumer daemon libraries\n");
        fprintf(stderr, "  -d, --daemonize                    Start as a daemon.\n");
        fprintf(stderr, "  -g, --group NAME                   Specify the tracing group name. (default: tracing)\n");
        fprintf(stderr, "  -V, --version                      Show version number.\n");
        fprintf(stderr, "  -S, --sig-parent                   Send SIGUSR1 to parent pid to notify readiness.\n");
        fprintf(stderr, "  -q, --quiet                        No output at all.\n");
        fprintf(stderr, "  -v, --verbose                      Verbose mode. Activate DBG() macro.\n");
        fprintf(stderr, "  -p, --pidfile FILE                 Write a pid to FILE name overriding the default value.\n");
        fprintf(stderr, "      --verbose-consumer             Verbose mode for consumer. Activate DBG() macro.\n");
        fprintf(stderr, "      --no-kernel                    Disable kernel tracer\n");
}

/*
 * daemon argument parsing
 */
static int parse_args(int argc, char **argv)
{
        int c;

        static struct option long_options[] = {
                { "client-sock", 1, 0, 'c' },
                { "apps-sock", 1, 0, 'a' },
                { "kconsumerd-cmd-sock", 1, 0, 'C' },
                { "kconsumerd-err-sock", 1, 0, 'E' },
                { "ustconsumerd32-cmd-sock", 1, 0, 'G' },
                { "ustconsumerd32-err-sock", 1, 0, 'H' },
                { "ustconsumerd64-cmd-sock", 1, 0, 'D' },
                { "ustconsumerd64-err-sock", 1, 0, 'F' },
                { "consumerd32-path", 1, 0, 'u' },
                { "consumerd32-libdir", 1, 0, 'U' },
                { "consumerd64-path", 1, 0, 't' },
                { "consumerd64-libdir", 1, 0, 'T' },
                { "daemonize", 0, 0, 'd' },
                { "sig-parent", 0, 0, 'S' },
                { "help", 0, 0, 'h' },
                { "group", 1, 0, 'g' },
                { "version", 0, 0, 'V' },
                { "quiet", 0, 0, 'q' },
                { "verbose", 0, 0, 'v' },
                { "verbose-consumer", 0, 0, 'Z' },
                { "no-kernel", 0, 0, 'N' },
                { "pidfile", 1, 0, 'p' },
                { NULL, 0, 0, 0 }
        };

        while (1) {
                int option_index = 0;
                c = getopt_long(argc, argv, "dhqvVSN" "a:c:g:s:C:E:D:F:Z:u:t:p:",
                                long_options, &option_index);
                if (c == -1) {
                        break;
                }

                switch (c) {
                case 0:
                        fprintf(stderr, "option %s", long_options[option_index].name);
                        if (optarg) {
                                fprintf(stderr, " with arg %s\n", optarg);
                        }
                        break;
                case 'c':
                        snprintf(client_unix_sock_path, PATH_MAX, "%s", optarg);
                        break;
                case 'a':
                        snprintf(apps_unix_sock_path, PATH_MAX, "%s", optarg);
                        break;
                case 'd':
                        opt_daemon = 1;
                        break;
                case 'g':
                        opt_tracing_group = optarg;
                        break;
                case 'h':
                        usage();
                        exit(EXIT_FAILURE);
                case 'V':
                        fprintf(stdout, "%s\n", VERSION);
                        exit(EXIT_SUCCESS);
                case 'S':
                        opt_sig_parent = 1;
                        break;
                case 'E':
                        snprintf(kconsumer_data.err_unix_sock_path, PATH_MAX, "%s", optarg);
                        break;
                case 'C':
                        snprintf(kconsumer_data.cmd_unix_sock_path, PATH_MAX, "%s", optarg);
                        break;
                case 'F':
                        snprintf(ustconsumer64_data.err_unix_sock_path, PATH_MAX, "%s", optarg);
                        break;
                case 'D':
                        snprintf(ustconsumer64_data.cmd_unix_sock_path, PATH_MAX, "%s", optarg);
                        break;
                case 'H':
                        snprintf(ustconsumer32_data.err_unix_sock_path, PATH_MAX, "%s", optarg);
                        break;
                case 'G':
                        snprintf(ustconsumer32_data.cmd_unix_sock_path, PATH_MAX, "%s", optarg);
                        break;
                case 'N':
                        opt_no_kernel = 1;
                        break;
                case 'q':
                        lttng_opt_quiet = 1;
                        break;
                case 'v':
                        /* Verbose level can increase using multiple -v */
                        lttng_opt_verbose += 1;
                        break;
                case 'Z':
                        opt_verbose_consumer += 1;
                        break;
                case 'u':
                        consumerd32_bin= optarg;
                        break;
                case 'U':
                        consumerd32_libdir = optarg;
                        break;
                case 't':
                        consumerd64_bin = optarg;
                        break;
                case 'T':
                        consumerd64_libdir = optarg;
                        break;
                case 'p':
                        opt_pidfile = optarg;
                        break;
                default:
                        /* Unknown option or other error.
                         * Error is printed by getopt, just return */
                        return -1;
                }
        }

        return 0;
}

/*
 * Creates the two needed socket by the daemon.
 *          apps_sock - The communication socket for all UST apps.
 *          client_sock - The communication of the cli tool (lttng).
 */
static int init_daemon_socket(void)
{
        int ret = 0;
        mode_t old_umask;

        old_umask = umask(0);

        /* Create client tool unix socket */
        client_sock = lttcomm_create_unix_sock(client_unix_sock_path);
        if (client_sock < 0) {
                ERR("Create unix sock failed: %s", client_unix_sock_path);
                ret = -1;
                goto end;
        }

        /* Set the cloexec flag */
        ret = utils_set_fd_cloexec(client_sock);
        if (ret < 0) {
                ERR("Unable to set CLOEXEC flag to the client Unix socket (fd: %d). "
                                "Continuing but note that the consumer daemon will have a "
                                "reference to this socket on exec()", client_sock);
        }

        /* File permission MUST be 660 */
        ret = chmod(client_unix_sock_path, S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP);
        if (ret < 0) {
                ERR("Set file permissions failed: %s", client_unix_sock_path);
                PERROR("chmod");
                goto end;
        }

        /* Create the application unix socket */
        apps_sock = lttcomm_create_unix_sock(apps_unix_sock_path);
        if (apps_sock < 0) {
                ERR("Create unix sock failed: %s", apps_unix_sock_path);
                ret = -1;
                goto end;
        }

        /* Set the cloexec flag */
        ret = utils_set_fd_cloexec(apps_sock);
        if (ret < 0) {
                ERR("Unable to set CLOEXEC flag to the app Unix socket (fd: %d). "
                                "Continuing but note that the consumer daemon will have a "
                                "reference to this socket on exec()", apps_sock);
        }

        /* File permission MUST be 666 */
        ret = chmod(apps_unix_sock_path,
                        S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH);
        if (ret < 0) {
                ERR("Set file permissions failed: %s", apps_unix_sock_path);
                PERROR("chmod");
                goto end;
        }

        DBG3("Session daemon client socket %d and application socket %d created",
                        client_sock, apps_sock);

end:
        umask(old_umask);
        return ret;
}

/*
 * Check if the global socket is available, and if a daemon is answering at the
 * other side. If yes, error is returned.
 */
static int check_existing_daemon(void)
{
        /* Is there anybody out there ? */
        if (lttng_session_daemon_alive()) {
                return -EEXIST;
        }

        return 0;
}

/*
 * Set the tracing group gid onto the client socket.
 *
 * Race window between mkdir and chown is OK because we are going from more
 * permissive (root.root) to less permissive (root.tracing).
 */
static int set_permissions(char *rundir)
{
        int ret;
        gid_t gid;

        ret = allowed_group();
        if (ret < 0) {
                WARN("No tracing group detected");
                /* Setting gid to 0 if no tracing group is found */
                gid = 0;
        } else {
                gid = ret;
        }

        /* Set lttng run dir */
        ret = chown(rundir, 0, gid);
        if (ret < 0) {
                ERR("Unable to set group on %s", rundir);
                PERROR("chown");
        }

        /* Ensure all applications and tracing group can search the run dir */
        ret = chmod(rundir, S_IRWXU | S_IXGRP | S_IXOTH);
        if (ret < 0) {
                ERR("Unable to set permissions on %s", rundir);
                PERROR("chmod");
        }

        /* lttng client socket path */
        ret = chown(client_unix_sock_path, 0, gid);
        if (ret < 0) {
                ERR("Unable to set group on %s", client_unix_sock_path);
                PERROR("chown");
        }

        /* kconsumer error socket path */
        ret = chown(kconsumer_data.err_unix_sock_path, 0, gid);
        if (ret < 0) {
                ERR("Unable to set group on %s", kconsumer_data.err_unix_sock_path);
                PERROR("chown");
        }

        /* 64-bit ustconsumer error socket path */
        ret = chown(ustconsumer64_data.err_unix_sock_path, 0, gid);
        if (ret < 0) {
                ERR("Unable to set group on %s", ustconsumer64_data.err_unix_sock_path);
                PERROR("chown");
        }

        /* 32-bit ustconsumer compat32 error socket path */
        ret = chown(ustconsumer32_data.err_unix_sock_path, 0, gid);
        if (ret < 0) {
                ERR("Unable to set group on %s", ustconsumer32_data.err_unix_sock_path);
                PERROR("chown");
        }

        DBG("All permissions are set");

        return ret;
}

/*
 * Create the lttng run directory needed for all global sockets and pipe.
 */
static int create_lttng_rundir(const char *rundir)
{
        int ret;

        DBG3("Creating LTTng run directory: %s", rundir);

        ret = mkdir(rundir, S_IRWXU);
        if (ret < 0) {
                if (errno != EEXIST) {
                        ERR("Unable to create %s", rundir);
                        goto error;
                } else {
                        ret = 0;
                }
        }

error:
        return ret;
}

/*
 * Setup sockets and directory needed by the kconsumerd communication with the
 * session daemon.
 */
static int set_consumer_sockets(struct consumer_data *consumer_data,
                const char *rundir)
{
        int ret;
        char path[PATH_MAX];

    switch (consumer_data->type) {
        case LTTNG_CONSUMER_KERNEL:
                snprintf(path, PATH_MAX, DEFAULT_KCONSUMERD_PATH, rundir);
                break;
        case LTTNG_CONSUMER64_UST:
                snprintf(path, PATH_MAX, DEFAULT_USTCONSUMERD64_PATH, rundir);
                break;
        case LTTNG_CONSUMER32_UST:
                snprintf(path, PATH_MAX, DEFAULT_USTCONSUMERD32_PATH, rundir);
                break;
        default:
                ERR("Consumer type unknown");
                ret = -EINVAL;
                goto error;
        }

        DBG2("Creating consumer directory: %s", path);

        ret = mkdir(path, S_IRWXU);
        if (ret < 0) {
                if (errno != EEXIST) {
                        PERROR("mkdir");
                        ERR("Failed to create %s", path);
                        goto error;
                }
                ret = -1;
        }

        /* Create the kconsumerd error unix socket */
        consumer_data->err_sock =
                lttcomm_create_unix_sock(consumer_data->err_unix_sock_path);
        if (consumer_data->err_sock < 0) {
                ERR("Create unix sock failed: %s", consumer_data->err_unix_sock_path);
                ret = -1;
                goto error;
        }

        /*
         * Set the CLOEXEC flag. Return code is useless because either way, the
         * show must go on.
         */
        ret = utils_set_fd_cloexec(consumer_data->err_sock);
        if (ret < 0) {
                PERROR("utils_set_fd_cloexec");
                /* continue anyway */
        }

        /* File permission MUST be 660 */
        ret = chmod(consumer_data->err_unix_sock_path,
                        S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP);
        if (ret < 0) {
                ERR("Set file permissions failed: %s", consumer_data->err_unix_sock_path);
                PERROR("chmod");
                goto error;
        }

error:
        return ret;
}

/*
 * Signal handler for the daemon
 *
 * Simply stop all worker threads, leaving main() return gracefully after
 * joining all threads and calling cleanup().
 */
static void sighandler(int sig)
{
        switch (sig) {
        case SIGPIPE:
                DBG("SIGPIPE caught");
                return;
        case SIGINT:
                DBG("SIGINT caught");
                stop_threads();
                break;
        case SIGTERM:
                DBG("SIGTERM caught");
                stop_threads();
                break;
        default:
                break;
        }
}

/*
 * Setup signal handler for :
 *              SIGINT, SIGTERM, SIGPIPE
 */
static int set_signal_handler(void)
{
        int ret = 0;
        struct sigaction sa;
        sigset_t sigset;

        if ((ret = sigemptyset(&sigset)) < 0) {
                PERROR("sigemptyset");
                return ret;
        }

        sa.sa_handler = sighandler;
        sa.sa_mask = sigset;
        sa.sa_flags = 0;
        if ((ret = sigaction(SIGTERM, &sa, NULL)) < 0) {
                PERROR("sigaction");
                return ret;
        }

        if ((ret = sigaction(SIGINT, &sa, NULL)) < 0) {
                PERROR("sigaction");
                return ret;
        }

        if ((ret = sigaction(SIGPIPE, &sa, NULL)) < 0) {
                PERROR("sigaction");
                return ret;
        }

        DBG("Signal handler set for SIGTERM, SIGPIPE and SIGINT");

        return ret;
}

/*
 * Set open files limit to unlimited. This daemon can open a large number of
 * file descriptors in order to consumer multiple kernel traces.
 */
static void set_ulimit(void)
{
        int ret;
        struct rlimit lim;

        /* The kernel does not allowed an infinite limit for open files */
        lim.rlim_cur = 65535;
        lim.rlim_max = 65535;

        ret = setrlimit(RLIMIT_NOFILE, &lim);
        if (ret < 0) {
                PERROR("failed to set open files limit");
        }
}

/*
 * Write pidfile using the rundir and opt_pidfile.
 */
static void write_pidfile(void)
{
        int ret;
        char pidfile_path[PATH_MAX];

        assert(rundir);

        if (opt_pidfile) {
                strncpy(pidfile_path, opt_pidfile, sizeof(pidfile_path));
        } else {
                /* Build pidfile path from rundir and opt_pidfile. */
                ret = snprintf(pidfile_path, sizeof(pidfile_path), "%s/"
                                DEFAULT_LTTNG_SESSIOND_PIDFILE, rundir);
                if (ret < 0) {
                        PERROR("snprintf pidfile path");
                        goto error;
                }
        }

        /*
         * Create pid file in rundir. Return value is of no importance. The
         * execution will continue even though we are not able to write the file.
         */
        (void) utils_create_pid_file(getpid(), pidfile_path);

error:
        return;
}

/*
 * main
 */
int main(int argc, char **argv)
{
        int ret = 0;
        void *status;
        const char *home_path, *env_app_timeout;

        init_kernel_workarounds();

        rcu_register_thread();

        setup_consumerd_path();

        page_size = sysconf(_SC_PAGESIZE);
        if (page_size < 0) {
                PERROR("sysconf _SC_PAGESIZE");
                page_size = LONG_MAX;
                WARN("Fallback page size to %ld", page_size);
        }

        /* Parse arguments */
        progname = argv[0];
        if ((ret = parse_args(argc, argv)) < 0) {
                goto error;
        }

        /* Daemonize */
        if (opt_daemon) {
                int i;

                /*
                 * fork
                 * child: setsid, close FD 0, 1, 2, chdir /
                 * parent: exit (if fork is successful)
                 */
                ret = daemon(0, 0);
                if (ret < 0) {
                        PERROR("daemon");
                        goto error;
                }
                /*
                 * We are in the child. Make sure all other file
                 * descriptors are closed, in case we are called with
                 * more opened file descriptors than the standard ones.
                 */
                for (i = 3; i < sysconf(_SC_OPEN_MAX); i++) {
                        (void) close(i);
                }
        }

        /* Create thread quit pipe */
        if ((ret = init_thread_quit_pipe()) < 0) {
                goto error;
        }

        /* Check if daemon is UID = 0 */
        is_root = !getuid();

        if (is_root) {
                rundir = strdup(DEFAULT_LTTNG_RUNDIR);

                /* Create global run dir with root access */
                ret = create_lttng_rundir(rundir);
                if (ret < 0) {
                        goto error;
                }

                if (strlen(apps_unix_sock_path) == 0) {
                        snprintf(apps_unix_sock_path, PATH_MAX,
                                        DEFAULT_GLOBAL_APPS_UNIX_SOCK);
                }

                if (strlen(client_unix_sock_path) == 0) {
                        snprintf(client_unix_sock_path, PATH_MAX,
                                        DEFAULT_GLOBAL_CLIENT_UNIX_SOCK);
                }

                /* Set global SHM for ust */
                if (strlen(wait_shm_path) == 0) {
                        snprintf(wait_shm_path, PATH_MAX,
                                        DEFAULT_GLOBAL_APPS_WAIT_SHM_PATH);
                }

                if (strlen(health_unix_sock_path) == 0) {
                        snprintf(health_unix_sock_path, sizeof(health_unix_sock_path),
                                        DEFAULT_GLOBAL_HEALTH_UNIX_SOCK);
                }

                /* Setup kernel consumerd path */
                snprintf(kconsumer_data.err_unix_sock_path, PATH_MAX,
                                DEFAULT_KCONSUMERD_ERR_SOCK_PATH, rundir);
                snprintf(kconsumer_data.cmd_unix_sock_path, PATH_MAX,
                                DEFAULT_KCONSUMERD_CMD_SOCK_PATH, rundir);

                DBG2("Kernel consumer err path: %s",
                                kconsumer_data.err_unix_sock_path);
                DBG2("Kernel consumer cmd path: %s",
                                kconsumer_data.cmd_unix_sock_path);
        } else {
                home_path = utils_get_home_dir();
                if (home_path == NULL) {
                        /* TODO: Add --socket PATH option */
                        ERR("Can't get HOME directory for sockets creation.");
                        ret = -EPERM;
                        goto error;
                }

                /*
                 * Create rundir from home path. This will create something like
                 * $HOME/.lttng
                 */
                ret = asprintf(&rundir, DEFAULT_LTTNG_HOME_RUNDIR, home_path);
                if (ret < 0) {
                        ret = -ENOMEM;
                        goto error;
                }

                ret = create_lttng_rundir(rundir);
                if (ret < 0) {
                        goto error;
                }

                if (strlen(apps_unix_sock_path) == 0) {
                        snprintf(apps_unix_sock_path, PATH_MAX,
                                        DEFAULT_HOME_APPS_UNIX_SOCK, home_path);
                }

                /* Set the cli tool unix socket path */
                if (strlen(client_unix_sock_path) == 0) {
                        snprintf(client_unix_sock_path, PATH_MAX,
                                        DEFAULT_HOME_CLIENT_UNIX_SOCK, home_path);
                }

                /* Set global SHM for ust */
                if (strlen(wait_shm_path) == 0) {
                        snprintf(wait_shm_path, PATH_MAX,
                                        DEFAULT_HOME_APPS_WAIT_SHM_PATH, getuid());
                }

                /* Set health check Unix path */
                if (strlen(health_unix_sock_path) == 0) {
                        snprintf(health_unix_sock_path, sizeof(health_unix_sock_path),
                                        DEFAULT_HOME_HEALTH_UNIX_SOCK, home_path);
                }
        }

        /* Set consumer initial state */
        kernel_consumerd_state = CONSUMER_STOPPED;
        ust_consumerd_state = CONSUMER_STOPPED;

        DBG("Client socket path %s", client_unix_sock_path);
        DBG("Application socket path %s", apps_unix_sock_path);
        DBG("Application wait path %s", wait_shm_path);
        DBG("LTTng run directory path: %s", rundir);

        /* 32 bits consumerd path setup */
        snprintf(ustconsumer32_data.err_unix_sock_path, PATH_MAX,
                        DEFAULT_USTCONSUMERD32_ERR_SOCK_PATH, rundir);
        snprintf(ustconsumer32_data.cmd_unix_sock_path, PATH_MAX,
                        DEFAULT_USTCONSUMERD32_CMD_SOCK_PATH, rundir);

        DBG2("UST consumer 32 bits err path: %s",
                        ustconsumer32_data.err_unix_sock_path);
        DBG2("UST consumer 32 bits cmd path: %s",
                        ustconsumer32_data.cmd_unix_sock_path);

        /* 64 bits consumerd path setup */
        snprintf(ustconsumer64_data.err_unix_sock_path, PATH_MAX,
                        DEFAULT_USTCONSUMERD64_ERR_SOCK_PATH, rundir);
        snprintf(ustconsumer64_data.cmd_unix_sock_path, PATH_MAX,
                        DEFAULT_USTCONSUMERD64_CMD_SOCK_PATH, rundir);

        DBG2("UST consumer 64 bits err path: %s",
                        ustconsumer64_data.err_unix_sock_path);
        DBG2("UST consumer 64 bits cmd path: %s",
                        ustconsumer64_data.cmd_unix_sock_path);

        /*
         * See if daemon already exist.
         */
        if ((ret = check_existing_daemon()) < 0) {
                ERR("Already running daemon.\n");
                /*
                 * We do not goto exit because we must not cleanup()
                 * because a daemon is already running.
                 */
                goto error;
        }

        /*
         * Init UST app hash table. Alloc hash table before this point since
         * cleanup() can get called after that point.
         */
        ust_app_ht_alloc();

        /* After this point, we can safely call cleanup() with "goto exit" */

        /*
         * These actions must be executed as root. We do that *after* setting up
         * the sockets path because we MUST make the check for another daemon using
         * those paths *before* trying to set the kernel consumer sockets and init
         * kernel tracer.
         */
        if (is_root) {
                ret = set_consumer_sockets(&kconsumer_data, rundir);
                if (ret < 0) {
                        goto exit;
                }

                /* Setup kernel tracer */
                if (!opt_no_kernel) {
                        init_kernel_tracer();
                }

                /* Set ulimit for open files */
                set_ulimit();
        }
        /* init lttng_fd tracking must be done after set_ulimit. */
        lttng_fd_init();

        ret = set_consumer_sockets(&ustconsumer64_data, rundir);
        if (ret < 0) {
                goto exit;
        }

        ret = set_consumer_sockets(&ustconsumer32_data, rundir);
        if (ret < 0) {
                goto exit;
        }

        if ((ret = set_signal_handler()) < 0) {
                goto exit;
        }

        /* Setup the needed unix socket */
        if ((ret = init_daemon_socket()) < 0) {
                goto exit;
        }

        /* Set credentials to socket */
        if (is_root && ((ret = set_permissions(rundir)) < 0)) {
                goto exit;
        }

        /* Get parent pid if -S, --sig-parent is specified. */
        if (opt_sig_parent) {
                ppid = getppid();
        }

        /* Setup the kernel pipe for waking up the kernel thread */
        if (is_root && !opt_no_kernel) {
                if ((ret = utils_create_pipe_cloexec(kernel_poll_pipe)) < 0) {
                        goto exit;
                }
        }

        /* Setup the thread ht_cleanup communication pipe. */
        if (utils_create_pipe_cloexec(ht_cleanup_pipe) < 0) {
                goto exit;
        }

        /* Setup the thread apps communication pipe. */
        if ((ret = utils_create_pipe_cloexec(apps_cmd_pipe)) < 0) {
                goto exit;
        }

        /* Setup the thread apps notify communication pipe. */
        if (utils_create_pipe_cloexec(apps_cmd_notify_pipe) < 0) {
                goto exit;
        }

        /* Initialize global buffer per UID and PID registry. */
        buffer_reg_init_uid_registry();
        buffer_reg_init_pid_registry();

        /* Init UST command queue. */
        cds_wfq_init(&ust_cmd_queue.queue);

        /*
         * Get session list pointer. This pointer MUST NOT be free(). This list is
         * statically declared in session.c
         */
        session_list_ptr = session_get_list();

        /* Set up max poll set size */
        lttng_poll_set_max_size();

        cmd_init();

        /* Check for the application socket timeout env variable. */
        env_app_timeout = getenv(DEFAULT_APP_SOCKET_TIMEOUT_ENV);
        if (env_app_timeout) {
                app_socket_timeout = atoi(env_app_timeout);
        } else {
                app_socket_timeout = DEFAULT_APP_SOCKET_RW_TIMEOUT;
        }

        write_pidfile();

        /* This is to get the TCP timeout value. */
        lttcomm_inet_init();

        /*
         * Initialize the health check subsystem. This call should set the
         * appropriate time values.
         */
        health_init();

        /* Create thread to manage the client socket */
        ret = pthread_create(&ht_cleanup_thread, NULL,
                        thread_ht_cleanup, (void *) NULL);
        if (ret != 0) {
                PERROR("pthread_create ht_cleanup");
                goto exit_ht_cleanup;
        }

        /* Create thread to manage the client socket */
        ret = pthread_create(&health_thread, NULL,
                        thread_manage_health, (void *) NULL);
        if (ret != 0) {
                PERROR("pthread_create health");
                goto exit_health;
        }

        /* Create thread to manage the client socket */
        ret = pthread_create(&client_thread, NULL,
                        thread_manage_clients, (void *) NULL);
        if (ret != 0) {
                PERROR("pthread_create clients");
                goto exit_client;
        }

        /* Create thread to dispatch registration */
        ret = pthread_create(&dispatch_thread, NULL,
                        thread_dispatch_ust_registration, (void *) NULL);
        if (ret != 0) {
                PERROR("pthread_create dispatch");
                goto exit_dispatch;
        }

        /* Create thread to manage application registration. */
        ret = pthread_create(&reg_apps_thread, NULL,
                        thread_registration_apps, (void *) NULL);
        if (ret != 0) {
                PERROR("pthread_create registration");
                goto exit_reg_apps;
        }

        /* Create thread to manage application socket */
        ret = pthread_create(&apps_thread, NULL,
                        thread_manage_apps, (void *) NULL);
        if (ret != 0) {
                PERROR("pthread_create apps");
                goto exit_apps;
        }

        /* Create thread to manage application notify socket */
        ret = pthread_create(&apps_notify_thread, NULL,
                        ust_thread_manage_notify, (void *) NULL);
        if (ret != 0) {
                PERROR("pthread_create apps");
                goto exit_apps;
        }

        /* Don't start this thread if kernel tracing is not requested nor root */
        if (is_root && !opt_no_kernel) {
                /* Create kernel thread to manage kernel event */
                ret = pthread_create(&kernel_thread, NULL,
                                thread_manage_kernel, (void *) NULL);
                if (ret != 0) {
                        PERROR("pthread_create kernel");
                        goto exit_kernel;
                }

                ret = pthread_join(kernel_thread, &status);
                if (ret != 0) {
                        PERROR("pthread_join");
                        goto error;     /* join error, exit without cleanup */
                }
        }

exit_kernel:
        ret = pthread_join(apps_thread, &status);
        if (ret != 0) {
                PERROR("pthread_join");
                goto error;     /* join error, exit without cleanup */
        }

exit_apps:
        ret = pthread_join(reg_apps_thread, &status);
        if (ret != 0) {
                PERROR("pthread_join");
                goto error;     /* join error, exit without cleanup */
        }

exit_reg_apps:
        ret = pthread_join(dispatch_thread, &status);
        if (ret != 0) {
                PERROR("pthread_join");
                goto error;     /* join error, exit without cleanup */
        }

exit_dispatch:
        ret = pthread_join(client_thread, &status);
        if (ret != 0) {
                PERROR("pthread_join");
                goto error;     /* join error, exit without cleanup */
        }

        ret = join_consumer_thread(&kconsumer_data);
        if (ret != 0) {
                PERROR("join_consumer");
                goto error;     /* join error, exit without cleanup */
        }

        ret = join_consumer_thread(&ustconsumer32_data);
        if (ret != 0) {
                PERROR("join_consumer ust32");
                goto error;     /* join error, exit without cleanup */
        }

        ret = join_consumer_thread(&ustconsumer64_data);
        if (ret != 0) {
                PERROR("join_consumer ust64");
                goto error;     /* join error, exit without cleanup */
        }

exit_client:
        ret = pthread_join(health_thread, &status);
        if (ret != 0) {
                PERROR("pthread_join health thread");
                goto error;     /* join error, exit without cleanup */
        }

exit_health:
        ret = pthread_join(ht_cleanup_thread, &status);
        if (ret != 0) {
                PERROR("pthread_join ht cleanup thread");
                goto error;     /* join error, exit without cleanup */
        }
exit_ht_cleanup:
exit:
        /*
         * cleanup() is called when no other thread is running.
         */
        rcu_thread_online();
        cleanup();
        rcu_thread_offline();
        rcu_unregister_thread();
        if (!ret) {
                exit(EXIT_SUCCESS);
        }
error:
        exit(EXIT_FAILURE);
}