Fix missing events for all threads pollfd struct

[lttng-tools.git] / ltt-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
 * as published by the Free Software Foundation; only version 2
 * of the License.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 */

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

#include <ltt-kconsumerd.h>
#include <lttng-sessiond-comm.h>
#include <lttng/lttng-kconsumerd.h>
#include <lttngerr.h>

#include "context.h"
#include "futex.h"
#include "kernel-ctl.h"
#include "ltt-sessiond.h"
#include "shm.h"
#include "traceable-app.h"
#include "ust-ctl.h"
#include "utils.h"
#include "ust-ctl.h"

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

/* Variables */
int opt_verbose;    /* Not static for lttngerr.h */
int opt_verbose_kconsumerd;    /* Not static for lttngerr.h */
int opt_quiet;      /* Not static for lttngerr.h */

const char *progname;
const char *opt_tracing_group;
static int opt_sig_parent;
static int opt_daemon;
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 pid_t kconsumerd_pid;
static struct pollfd *kernel_pollfd;
static int dispatch_thread_exit;

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

/* Sockets and FDs */
static int client_sock;
static int apps_sock;
static int kconsumerd_err_sock;
static int kconsumerd_cmd_sock;
static int kernel_tracer_fd;
static int kernel_poll_pipe[2];

/*
 * 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];

/*
 * 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];

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

static pthread_mutex_t kconsumerd_pid_mutex;    /* Mutex to control kconsumerd pid assignation */

/*
 * 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
 * lock_session_list and unlock_session_list for lock acquisition.
 */
static struct ltt_session_list *session_list_ptr;

/*
 * Remove modules in reverse load order.
 */
static int modprobe_remove_kernel_modules(void)
{
        int ret = 0, i;
        char modprobe[256];

        for (i = ARRAY_SIZE(kernel_modules_list) - 1; i >= 0; i--) {
                ret = snprintf(modprobe, sizeof(modprobe),
                                "/sbin/modprobe --remove --quiet %s",
                                kernel_modules_list[i].name);
                if (ret < 0) {
                        perror("snprintf modprobe --remove");
                        goto error;
                }
                modprobe[sizeof(modprobe) - 1] = '\0';
                ret = system(modprobe);
                if (ret == -1) {
                        ERR("Unable to launch modprobe --remove for module %s",
                                        kernel_modules_list[i].name);
                } else if (kernel_modules_list[i].required
                                && WEXITSTATUS(ret) != 0) {
                        ERR("Unable to remove module %s",
                                        kernel_modules_list[i].name);
                } else {
                        DBG("Modprobe removal successful %s",
                                        kernel_modules_list[i].name);
                }
        }

error:
        return ret;
}

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

        ret = pipe2(thread_quit_pipe, O_CLOEXEC);
        if (ret < 0) {
                perror("thread quit pipe");
                goto error;
        }

error:
        return ret;
}

/*
 * Complete teardown of a kernel session. This free all data structure related
 * to a kernel session and update counter.
 */
static void teardown_kernel_session(struct ltt_session *session)
{
        if (session->kernel_session != NULL) {
                DBG("Tearing down kernel session");

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

                trace_kernel_destroy_session(session->kernel_session);
                /* Extra precaution */
                session->kernel_session = NULL;
        }
}

/*
 * Stop all threads by closing the thread quit pipe.
 */
static void stop_threads(void)
{
        /* Stopping all threads */
        DBG("Terminating all threads");
        close(thread_quit_pipe[0]);
        close(thread_quit_pipe[1]);
        /* Dispatch thread */
        dispatch_thread_exit = 1;
        futex_nto1_wake(&ust_cmd_queue.futex);
}

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

        DBG("Cleaning up");

        /* <fun> */
        MSG("%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> */

        DBG("Removing %s directory", LTTNG_RUNDIR);
        ret = asprintf(&cmd, "rm -rf " LTTNG_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 " LTTNG_RUNDIR);
        }

        DBG("Cleaning up all session");

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

                /* Cleanup ALL session */
                cds_list_for_each_entry_safe(sess, stmp, &session_list_ptr->head, list) {
                        teardown_kernel_session(sess);
                        // TODO complete session cleanup (including UST)
                }
        }

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

        pthread_mutex_destroy(&kconsumerd_pid_mutex);

        DBG("Closing kernel fd");
        close(kernel_tracer_fd);

        if (is_root) {
                DBG("Unloading kernel modules");
                modprobe_remove_kernel_modules();
        }
}

/*
 * 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;
        }
}

/*
 * Send all stream fds of kernel channel to the consumer.
 */
static int send_kconsumerd_channel_fds(int sock, struct ltt_kernel_channel *channel)
{
        int ret;
        size_t nb_fd;
        struct ltt_kernel_stream *stream;
        struct lttcomm_kconsumerd_header lkh;
        struct lttcomm_kconsumerd_msg lkm;

        DBG("Sending fds of channel %s to kernel consumer", channel->channel->name);

        nb_fd = channel->stream_count;

        /* Setup header */
        lkh.payload_size = nb_fd * sizeof(struct lttcomm_kconsumerd_msg);
        lkh.cmd_type = ADD_STREAM;

        DBG("Sending kconsumerd header");

        ret = lttcomm_send_unix_sock(sock, &lkh, sizeof(struct lttcomm_kconsumerd_header));
        if (ret < 0) {
                perror("send kconsumerd header");
                goto error;
        }

        cds_list_for_each_entry(stream, &channel->stream_list.head, list) {
                if (stream->fd != 0) {
                        lkm.fd = stream->fd;
                        lkm.state = stream->state;
                        lkm.max_sb_size = channel->channel->attr.subbuf_size;
                        lkm.output = channel->channel->attr.output;
                        strncpy(lkm.path_name, stream->pathname, PATH_MAX);
                        lkm.path_name[PATH_MAX - 1] = '\0';

                        DBG("Sending fd %d to kconsumerd", lkm.fd);

                        ret = lttcomm_send_fds_unix_sock(sock, &lkm, &lkm.fd, 1, sizeof(lkm));
                        if (ret < 0) {
                                perror("send kconsumerd fd");
                                goto error;
                        }
                }
        }

        DBG("Kconsumerd channel fds sent");

        return 0;

error:
        return ret;
}

/*
 * Send all stream fds of the kernel session to the consumer.
 */
static int send_kconsumerd_fds(struct ltt_kernel_session *session)
{
        int ret;
        struct ltt_kernel_channel *chan;
        struct lttcomm_kconsumerd_header lkh;
        struct lttcomm_kconsumerd_msg lkm;

        /* Setup header */
        lkh.payload_size = sizeof(struct lttcomm_kconsumerd_msg);
        lkh.cmd_type = ADD_STREAM;

        DBG("Sending kconsumerd header for metadata");

        ret = lttcomm_send_unix_sock(session->consumer_fd, &lkh, sizeof(struct lttcomm_kconsumerd_header));
        if (ret < 0) {
                perror("send kconsumerd header");
                goto error;
        }

        DBG("Sending metadata stream fd");

        /* Extra protection. It's NOT suppose to be set to 0 at this point */
        if (session->consumer_fd == 0) {
                session->consumer_fd = kconsumerd_cmd_sock;
        }

        if (session->metadata_stream_fd != 0) {
                /* Send metadata stream fd first */
                lkm.fd = session->metadata_stream_fd;
                lkm.state = ACTIVE_FD;
                lkm.max_sb_size = session->metadata->conf->attr.subbuf_size;
                lkm.output = DEFAULT_KERNEL_CHANNEL_OUTPUT;
                strncpy(lkm.path_name, session->metadata->pathname, PATH_MAX);
                lkm.path_name[PATH_MAX - 1] = '\0';

                ret = lttcomm_send_fds_unix_sock(session->consumer_fd, &lkm, &lkm.fd, 1, sizeof(lkm));
                if (ret < 0) {
                        perror("send kconsumerd fd");
                        goto error;
                }
        }

        cds_list_for_each_entry(chan, &session->channel_list.head, list) {
                ret = send_kconsumerd_channel_fds(session->consumer_fd, chan);
                if (ret < 0) {
                        goto error;
                }
        }

        DBG("Kconsumerd fds (metadata and channel streams) sent");

        return 0;

error:
        return ret;
}

/*
 * 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 = malloc(sizeof(struct lttcomm_lttng_msg) + buf_size);
        if (cmd_ctx->llm == NULL) {
                perror("malloc");
                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 pollfd set of all channel fd available over all tracing
 * session. Add the wakeup pipe at the end of the set.
 */
static int update_kernel_pollfd(void)
{
        int i = 0;
        /*
         * The wakup pipe and the quit pipe are needed so the number of fds starts
         * at 2 for those pipes.
         */
        unsigned int nb_fd = 2;
        struct ltt_session *session;
        struct ltt_kernel_channel *channel;

        DBG("Updating kernel_pollfd");

        /* Get the number of channel of all kernel session */
        lock_session_list();
        cds_list_for_each_entry(session, &session_list_ptr->head, list) {
                lock_session(session);
                if (session->kernel_session == NULL) {
                        unlock_session(session);
                        continue;
                }
                nb_fd += session->kernel_session->channel_count;
                unlock_session(session);
        }

        DBG("Resizing kernel_pollfd to size %d", nb_fd);

        kernel_pollfd = realloc(kernel_pollfd, nb_fd * sizeof(struct pollfd));
        if (kernel_pollfd == NULL) {
                perror("malloc kernel_pollfd");
                goto error;
        }

        cds_list_for_each_entry(session, &session_list_ptr->head, list) {
                lock_session(session);
                if (session->kernel_session == NULL) {
                        unlock_session(session);
                        continue;
                }
                if (i >= nb_fd) {
                        ERR("To much channel for kernel_pollfd size");
                        unlock_session(session);
                        break;
                }
                cds_list_for_each_entry(channel, &session->kernel_session->channel_list.head, list) {
                        kernel_pollfd[i].fd = channel->fd;
                        kernel_pollfd[i].events = POLLIN | POLLRDNORM;
                        i++;
                }
                unlock_session(session);
        }
        unlock_session_list();

        /* Adding wake up pipe */
        kernel_pollfd[nb_fd - 2].fd = kernel_poll_pipe[0];
        kernel_pollfd[nb_fd - 2].events = POLLIN;

        /* Adding the quit pipe */
        kernel_pollfd[nb_fd - 1].fd = thread_quit_pipe[0];
        kernel_pollfd[nb_fd - 1].events =
                POLLHUP | POLLNVAL | POLLERR | POLLIN | POLLRDHUP | POLLPRI;

        return nb_fd;

error:
        unlock_session_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(int fd)
{
        int ret = 0;
        struct ltt_session *session;
        struct ltt_kernel_channel *channel;

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

        lock_session_list();
        cds_list_for_each_entry(session, &session_list_ptr->head, list) {
                lock_session(session);
                if (session->kernel_session == NULL) {
                        unlock_session(session);
                        continue;
                }

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

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

                                /*
                                 * Have we already sent fds to the consumer? If yes, it means that
                                 * tracing is started so it is safe to send our updated stream fds.
                                 */
                                if (session->kernel_session->kconsumer_fds_sent == 1) {
                                        ret = send_kconsumerd_channel_fds(session->kernel_session->consumer_fd,
                                                        channel);
                                        if (ret < 0) {
                                                goto end;
                                        }
                                }
                                goto end;
                        }
                }
                unlock_session(session);
        }

end:
        unlock_session_list();
        if (session) {
                unlock_session(session);
        }
        return ret;
}

/*
 * 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, nb_fd = 0;
        char tmp;
        int update_poll_flag = 1;

        DBG("Thread manage kernel started");

        while (1) {
                if (update_poll_flag == 1) {
                        nb_fd = update_kernel_pollfd();
                        if (nb_fd < 0) {
                                goto error;
                        }
                        update_poll_flag = 0;
                }

                DBG("Polling on %d fds", nb_fd);

                /* Poll infinite value of time */
                ret = poll(kernel_pollfd, nb_fd, -1);
                if (ret < 0) {
                        perror("poll kernel thread");
                        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;
                }

                /* Thread quit pipe has been closed. Killing thread. */
                if (kernel_pollfd[nb_fd - 1].revents == POLLNVAL) {
                        goto error;
                }

                DBG("Kernel poll event triggered");

                /*
                 * Check if the wake up pipe was triggered. If so, the kernel_pollfd
                 * must be updated.
                 */
                switch (kernel_pollfd[nb_fd - 2].revents) {
                case POLLIN:
                        ret = read(kernel_poll_pipe[0], &tmp, 1);
                        update_poll_flag = 1;
                        continue;
                case POLLERR:
                        goto error;
                default:
                        break;
                }

                for (i = 0; i < nb_fd; i++) {
                        switch (kernel_pollfd[i].revents) {
                        /*
                         * New CPU detected by the kernel. Adding kernel stream to kernel
                         * session and updating the kernel consumer
                         */
                        case POLLIN | POLLRDNORM:
                                ret = update_kernel_stream(kernel_pollfd[i].fd);
                                if (ret < 0) {
                                        continue;
                                }
                                break;
                        }
                }
        }

error:
        DBG("Kernel thread dying");
        if (kernel_pollfd) {
                free(kernel_pollfd);
        }

        close(kernel_poll_pipe[0]);
        close(kernel_poll_pipe[1]);
        return NULL;
}

/*
 * This thread manage the kconsumerd error sent back to the session daemon.
 */
static void *thread_manage_kconsumerd(void *data)
{
        int sock = 0, ret;
        enum lttcomm_return_code code;
        struct pollfd pollfd[2];

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

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

        /* First fd is always the quit pipe */
        pollfd[0].fd = thread_quit_pipe[0];

        /* Apps socket */
        pollfd[1].fd = kconsumerd_err_sock;
        pollfd[1].events = POLLIN;

        /* Inifinite blocking call, waiting for transmission */
        ret = poll(pollfd, 2, -1);
        if (ret < 0) {
                perror("poll kconsumerd thread");
                goto error;
        }

        /* Thread quit pipe has been closed. Killing thread. */
        if (pollfd[0].revents == POLLNVAL) {
                goto error;
        } else if (pollfd[1].revents == POLLERR) {
                ERR("Kconsumerd err socket poll error");
                goto error;
        }

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

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

        if (code == KCONSUMERD_COMMAND_SOCK_READY) {
                kconsumerd_cmd_sock = lttcomm_connect_unix_sock(kconsumerd_cmd_unix_sock_path);
                if (kconsumerd_cmd_sock < 0) {
                        sem_post(&kconsumerd_sem);
                        perror("kconsumerd connect");
                        goto error;
                }
                /* Signal condition to tell that the kconsumerd is ready */
                sem_post(&kconsumerd_sem);
                DBG("Kconsumerd command socket ready");
        } else {
                DBG("Kconsumerd error when waiting for SOCK_READY : %s",
                                lttcomm_get_readable_code(-code));
                goto error;
        }

        /* Kconsumerd err socket */
        pollfd[1].fd = sock;
        pollfd[1].events = POLLIN;

        /* Inifinite blocking call, waiting for transmission */
        ret = poll(pollfd, 2, -1);
        if (ret < 0) {
                perror("poll kconsumerd thread");
                goto error;
        }

        /* Thread quit pipe has been closed. Killing thread. */
        if (pollfd[0].revents == POLLNVAL) {
                goto error;
        } else if (pollfd[1].revents == POLLERR) {
                ERR("Kconsumerd err socket second poll error");
                goto error;
        }

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

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

error:
        DBG("Kconsumerd thread dying");
        if (kconsumerd_err_sock) {
                close(kconsumerd_err_sock);
        }
        if (kconsumerd_cmd_sock) {
                close(kconsumerd_cmd_sock);
        }
        if (sock) {
                close(sock);
        }

        unlink(kconsumerd_err_unix_sock_path);
        unlink(kconsumerd_cmd_unix_sock_path);

        kconsumerd_pid = 0;
        return NULL;
}

/*
 * Reallocate the apps command pollfd structure of nb_fd size.
 *
 * The first two fds must be there at all time.
 */
static int update_apps_cmd_pollfd(unsigned int nb_fd, unsigned int old_nb_fd,
                struct pollfd **pollfd)
{
        int i, count;
        struct pollfd *old_pollfd = NULL;

        /* Can't accept pollfd less than 2 */
        if (nb_fd < 2) {
                goto end;
        }

        if (*pollfd) {
                /* Save pointer */
                old_pollfd = *pollfd;
        }

        *pollfd = malloc(nb_fd * sizeof(struct pollfd));
        if (*pollfd == NULL) {
                perror("malloc manage apps pollfd");
                goto error;
        }

        /* First fd is always the quit pipe */
        (*pollfd)[0].fd = thread_quit_pipe[0];
        (*pollfd)[0].events =
                POLLHUP | POLLNVAL | POLLERR | POLLIN | POLLRDHUP | POLLPRI;

        /* Apps command pipe */
        (*pollfd)[1].fd = apps_cmd_pipe[0];
        (*pollfd)[1].events = POLLIN;

        /* Start count after the two pipes below */
        count = 2;
        for (i = 2; i < old_nb_fd; i++) {
                /* Add to new pollfd */
                if (old_pollfd[i].fd != -1) {
                        (*pollfd)[count].fd = old_pollfd[i].fd;
                        (*pollfd)[count].events = POLLHUP | POLLNVAL | POLLERR;
                        count++;
                }

                if (count > nb_fd) {
                        ERR("Updating poll fd wrong size");
                        goto error;
                }
        }

        if (nb_fd < 2) {
                /*
                 * There should *always* be at least two fds in the pollfd. This safety
                 * check make sure the poll() will actually try on those two pipes at
                 * best which are the thread_quit_pipe and apps_cmd_pipe.
                 */
                nb_fd = 2;
                MSG("nb_fd < 2 --> Not good! Continuing...");
        }

        /* Destroy old pollfd */
        free(old_pollfd);

        DBG("Apps cmd pollfd realloc of size %d", nb_fd);

end:
        return 0;

error:
        /* Destroy old pollfd */
        free(old_pollfd);
        return -1;
}

/*
 * This thread manage application communication.
 */
static void *thread_manage_apps(void *data)
{
        int i, ret, current_nb_fd;
        unsigned int nb_fd = 2;
        int update_poll_flag = 1;
        struct pollfd *pollfd = NULL;
        struct ust_command ust_cmd;

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

        ust_cmd.sock = -1;
        current_nb_fd = nb_fd;

        while (1) {
                /* See if we have a valid socket to add to pollfd */
                if (ust_cmd.sock != -1) {
                        nb_fd++;
                        update_poll_flag = 1;
                }

                /* The pollfd struct must be updated */
                if (update_poll_flag) {
                        ret = update_apps_cmd_pollfd(nb_fd, current_nb_fd, &pollfd);
                        if (ret < 0) {
                                /* malloc failed so we quit */
                                goto error;
                        }

                        if (ust_cmd.sock != -1) {
                                /* Update pollfd with the new UST socket */
                                DBG("Adding sock %d to apps cmd pollfd", ust_cmd.sock);
                                pollfd[nb_fd - 1].fd = ust_cmd.sock;
                                pollfd[nb_fd - 1].events = POLLHUP | POLLNVAL | POLLERR;
                                ust_cmd.sock = -1;
                        }
                }

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

                /* Inifinite blocking call, waiting for transmission */
                ret = poll(pollfd, nb_fd, -1);
                if (ret < 0) {
                        perror("poll apps thread");
                        goto error;
                }

                /* Thread quit pipe has been closed. Killing thread. */
                if (pollfd[0].revents == POLLNVAL) {
                        goto error;
                } else {
                        /* apps_cmd_pipe pipe events */
                        switch (pollfd[1].revents) {
                        case POLLERR:
                                ERR("Apps command pipe poll error");
                                goto error;
                        case POLLIN:
                                /* Empty pipe */
                                ret = read(apps_cmd_pipe[0], &ust_cmd, sizeof(ust_cmd));
                                if (ret < 0 || ret < sizeof(ust_cmd)) {
                                        perror("read apps cmd pipe");
                                        goto error;
                                }

                                /* Register applicaton to the session daemon */
                                ret = register_traceable_app(&ust_cmd.reg_msg, ust_cmd.sock);
                                if (ret < 0) {
                                        /* Only critical ENOMEM error can be returned here */
                                        goto error;
                                }

                                ret = ustctl_register_done(ust_cmd.sock);
                                if (ret < 0) {
                                        /*
                                         * If the registration is not possible, we simply unregister
                                         * the apps and continue
                                         */
                                        unregister_traceable_app(ust_cmd.sock);
                                }
                                break;
                        }
                }

                current_nb_fd = nb_fd;
                for (i = 2; i < current_nb_fd; i++) {
                        /* Apps socket is closed/hungup */
                        switch (pollfd[i].revents) {
                        case POLLERR:
                        case POLLHUP:
                        case POLLNVAL:
                                /* Pipe closed */
                                unregister_traceable_app(pollfd[i].fd);
                                /* Indicate to remove this fd from the pollfd */
                                pollfd[i].fd = -1;
                                nb_fd--;
                                break;
                        }
                }

                if (nb_fd != current_nb_fd) {
                        update_poll_flag = 1;
                }
        }

error:
        DBG("Application communication apps dying");
        close(apps_cmd_pipe[0]);
        close(apps_cmd_pipe[1]);

        free(pollfd);

        return NULL;
}

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

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

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

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

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

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

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

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

/*
 * This thread manage application registration.
 */
static void *thread_registration_apps(void *data)
{
        int sock = 0, ret;
        struct pollfd pollfd[2];
        /*
         * Get allocated in this thread, enqueued to a global queue, dequeued and
         * freed in the manage apps thread.
         */
        struct ust_command *ust_cmd = NULL;

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

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

        /* First fd is always the quit pipe */
        pollfd[0].fd = thread_quit_pipe[0];
        pollfd[0].events =
                POLLHUP | POLLNVAL | POLLERR | POLLIN | POLLRDHUP | POLLPRI;

        /* Apps socket */
        pollfd[1].fd = apps_sock;
        pollfd[1].events = POLLIN;

        /* 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 running\n"
                        "applications that wishes to register.");
        }

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

                /* Inifinite blocking call, waiting for transmission */
                ret = poll(pollfd, 2, -1);
                if (ret < 0) {
                        perror("poll register apps thread");
                        goto error;
                }

                /* Thread quit pipe has been closed. Killing thread. */
                if (pollfd[0].revents == POLLNVAL) {
                        goto error;
                } else if (pollfd[1].revents == POLLERR) {
                        ERR("Register apps socket poll error");
                        goto error;
                }

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

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

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

                ust_cmd->sock = sock;

                DBG("UST registration received with pid:%d ppid:%d uid:%d"
                                " gid:%d sock:%d name:%s (version %d.%d)",
                                ust_cmd->reg_msg.pid, ust_cmd->reg_msg.ppid,
                                ust_cmd->reg_msg.uid, ust_cmd->reg_msg.gid,
                                ust_cmd->sock, ust_cmd->reg_msg.name,
                                ust_cmd->reg_msg.major, ust_cmd->reg_msg.minor);
                /*
                 * Lock free enqueue the registration request.
                 * The red pill has been taken! This apps will be part of the *system*
                 */
                cds_wfq_enqueue(&ust_cmd_queue.queue, &ust_cmd->node);

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

error:
        DBG("UST Registration thread dying");

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

        close(apps_sock);
        close(sock);

        unlink(apps_unix_sock_path);

        return NULL;
}

/*
 * Start the thread_manage_kconsumerd. This must be done after a kconsumerd
 * exec or it will fails.
 */
static int spawn_kconsumerd_thread(void)
{
        int ret;

        /* Setup semaphore */
        sem_init(&kconsumerd_sem, 0, 0);

        ret = pthread_create(&kconsumerd_thread, NULL, thread_manage_kconsumerd, (void *) NULL);
        if (ret != 0) {
                perror("pthread_create kconsumerd");
                goto error;
        }

        /* Wait for the kconsumerd thread to be ready */
        sem_wait(&kconsumerd_sem);

        if (kconsumerd_pid == 0) {
                ERR("Kconsumerd did not start");
                goto error;
        }

        return 0;

error:
        ret = LTTCOMM_KERN_CONSUMER_FAIL;
        return ret;
}

/*
 * Join kernel consumer thread
 */
static int join_kconsumerd_thread(void)
{
        void *status;
        int ret;

        if (kconsumerd_pid != 0) {
                ret = kill(kconsumerd_pid, SIGTERM);
                if (ret) {
                        ERR("Error killing kconsumerd");
                        return ret;
                }
                return pthread_join(kconsumerd_thread, &status);
        } else {
                return 0;
        }
}

/*
 * Fork and exec a kernel consumer daemon (kconsumerd).
 *
 * Return pid if successful else -1.
 */
static pid_t spawn_kconsumerd(void)
{
        int ret;
        pid_t pid;
        const char *verbosity;

        DBG("Spawning kconsumerd");

        pid = fork();
        if (pid == 0) {
                /*
                 * Exec kconsumerd.
                 */
                if (opt_verbose > 1 || opt_verbose_kconsumerd) {
                        verbosity = "--verbose";
                } else {
                        verbosity = "--quiet";
                }
                execl(INSTALL_BIN_PATH "/ltt-kconsumerd", "ltt-kconsumerd", verbosity, NULL);
                if (errno != 0) {
                        perror("kernel start consumer exec");
                }
                exit(EXIT_FAILURE);
        } else if (pid > 0) {
                ret = pid;
                goto error;
        } else {
                perror("kernel start consumer fork");
                ret = -errno;
                goto error;
        }

error:
        return ret;
}

/*
 * Spawn the kconsumerd daemon and session daemon thread.
 */
static int start_kconsumerd(void)
{
        int ret;

        pthread_mutex_lock(&kconsumerd_pid_mutex);
        if (kconsumerd_pid != 0) {
                pthread_mutex_unlock(&kconsumerd_pid_mutex);
                goto end;
        }

        ret = spawn_kconsumerd();
        if (ret < 0) {
                ERR("Spawning kconsumerd failed");
                ret = LTTCOMM_KERN_CONSUMER_FAIL;
                pthread_mutex_unlock(&kconsumerd_pid_mutex);
                goto error;
        }

        /* Setting up the global kconsumerd_pid */
        kconsumerd_pid = ret;
        pthread_mutex_unlock(&kconsumerd_pid_mutex);

        DBG("Kconsumerd pid %d", ret);

        DBG("Spawning kconsumerd thread");
        ret = spawn_kconsumerd_thread();
        if (ret < 0) {
                ERR("Fatal error spawning kconsumerd thread");
                goto error;
        }

end:
        return 0;

error:
        return ret;
}

/*
 * modprobe_kernel_modules
 */
static int modprobe_kernel_modules(void)
{
        int ret = 0, i;
        char modprobe[256];

        for (i = 0; i < ARRAY_SIZE(kernel_modules_list); i++) {
                ret = snprintf(modprobe, sizeof(modprobe),
                        "/sbin/modprobe %s%s",
                        kernel_modules_list[i].required ? "" : "--quiet ",
                        kernel_modules_list[i].name);
                if (ret < 0) {
                        perror("snprintf modprobe");
                        goto error;
                }
                modprobe[sizeof(modprobe) - 1] = '\0';
                ret = system(modprobe);
                if (ret == -1) {
                        ERR("Unable to launch modprobe for module %s",
                                kernel_modules_list[i].name);
                } else if (kernel_modules_list[i].required
                                && WEXITSTATUS(ret) != 0) {
                        ERR("Unable to load module %s",
                                kernel_modules_list[i].name);
                } else {
                        DBG("Modprobe successfully %s",
                                kernel_modules_list[i].name);
                }
        }

error:
        return ret;
}

/*
 * mount_debugfs
 */
static int mount_debugfs(char *path)
{
        int ret;
        char *type = "debugfs";

        ret = mkdir_recursive(path, S_IRWXU | S_IRWXG, geteuid(), getegid());
        if (ret < 0) {
                goto error;
        }

        ret = mount(type, path, type, 0, NULL);
        if (ret < 0) {
                perror("mount debugfs");
                goto error;
        }

        DBG("Mounted debugfs successfully at %s", path);

error:
        return ret;
}

/*
 * Setup necessary data for kernel tracer action.
 */
static void init_kernel_tracer(void)
{
        int ret;
        char *proc_mounts = "/proc/mounts";
        char line[256];
        char *debugfs_path = NULL, *lttng_path;
        FILE *fp;

        /* Detect debugfs */
        fp = fopen(proc_mounts, "r");
        if (fp == NULL) {
                ERR("Unable to probe %s", proc_mounts);
                goto error;
        }

        while (fgets(line, sizeof(line), fp) != NULL) {
                if (strstr(line, "debugfs") != NULL) {
                        /* Remove first string */
                        strtok(line, " ");
                        /* Dup string here so we can reuse line later on */
                        debugfs_path = strdup(strtok(NULL, " "));
                        DBG("Got debugfs path : %s", debugfs_path);
                        break;
                }
        }

        fclose(fp);

        /* Mount debugfs if needded */
        if (debugfs_path == NULL) {
                ret = asprintf(&debugfs_path, "/mnt/debugfs");
                if (ret < 0) {
                        perror("asprintf debugfs path");
                        goto error;
                }
                ret = mount_debugfs(debugfs_path);
                if (ret < 0) {
                        goto error;
                }
        }

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

        /* Setup lttng kernel path */
        ret = asprintf(&lttng_path, "%s/lttng", debugfs_path);
        if (ret < 0) {
                perror("asprintf lttng path");
                goto error;
        }

        /* Open debugfs lttng */
        kernel_tracer_fd = open(lttng_path, O_RDWR);
        if (kernel_tracer_fd < 0) {
                DBG("Failed to open %s", lttng_path);
                goto error;
        }

        free(lttng_path);
        free(debugfs_path);
        DBG("Kernel tracer fd %d", kernel_tracer_fd);
        return;

error:
        if (lttng_path) {
                free(lttng_path);
        }
        if (debugfs_path) {
                free(debugfs_path);
        }
        WARN("No kernel tracer available");
        kernel_tracer_fd = 0;
        return;
}

/*
 * Start tracing by creating trace directory and sending FDs to the kernel
 * consumer.
 */
static int start_kernel_trace(struct ltt_kernel_session *session)
{
        int ret = 0;

        if (session->kconsumer_fds_sent == 0) {
                /*
                 * Assign default kernel consumer if no consumer assigned to the kernel
                 * session. At this point, it's NOT suppose to be 0 but this is an extra
                 * security check.
                 */
                if (session->consumer_fd == 0) {
                        session->consumer_fd = kconsumerd_cmd_sock;
                }

                ret = send_kconsumerd_fds(session);
                if (ret < 0) {
                        ERR("Send kconsumerd fds failed");
                        ret = LTTCOMM_KERN_CONSUMER_FAIL;
                        goto error;
                }

                session->kconsumer_fds_sent = 1;
        }

error:
        return ret;
}

/*
 * Notify kernel thread to update it's pollfd.
 */
static int notify_kernel_pollfd(void)
{
        int ret;

        /* Inform kernel thread of the new kernel channel */
        ret = write(kernel_poll_pipe[1], "!", 1);
        if (ret < 0) {
                perror("write kernel poll pipe");
        }

        return ret;
}

/*
 * Allocate a channel structure and fill it.
 */
static struct lttng_channel *init_default_channel(enum lttng_domain_type domain_type,
                                                char *name)
{
        struct lttng_channel *chan;

        chan = malloc(sizeof(struct lttng_channel));
        if (chan == NULL) {
                perror("init channel malloc");
                goto error;
        }

        if (snprintf(chan->name, NAME_MAX, "%s", name) < 0) {
                perror("snprintf channel name");
                goto error;
        }

        chan->attr.overwrite = DEFAULT_CHANNEL_OVERWRITE;
        chan->attr.switch_timer_interval = DEFAULT_CHANNEL_SWITCH_TIMER;
        chan->attr.read_timer_interval = DEFAULT_CHANNEL_READ_TIMER;

        switch (domain_type) {
        case LTTNG_DOMAIN_KERNEL:
                chan->attr.subbuf_size = DEFAULT_KERNEL_CHANNEL_SUBBUF_SIZE;
                chan->attr.num_subbuf = DEFAULT_KERNEL_CHANNEL_SUBBUF_NUM;
                chan->attr.output = DEFAULT_KERNEL_CHANNEL_OUTPUT;
                break;
                /* TODO: add UST */
        default:
                goto error;     /* Not implemented */
        }

        return chan;

error:
        free(chan);
        return NULL;
}

/*
 * Create an UST session and add it to the session ust list.
 */
static int create_ust_session(pid_t pid, struct ltt_session *session)
{
        int ret = -1;
        struct ltt_ust_session *lus;

        DBG("Creating UST session");

        lus = trace_ust_create_session(session->path, pid);
        if (lus == NULL) {
                goto error;
        }

        ret = mkdir_recursive(lus->path, S_IRWXU | S_IRWXG,
                        geteuid(), allowed_group());
        if (ret < 0) {
                if (ret != -EEXIST) {
                        ERR("Trace directory creation error");
                        goto error;
                }
        }

        /* Create session on the UST tracer */
        ret = ustctl_create_session(lus);
        if (ret < 0) {
                goto error;
        }

        return 0;

error:
        free(lus);
        return ret;
}

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

        DBG("Creating kernel session");

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

        /* Set kernel consumer socket fd */
        if (kconsumerd_cmd_sock) {
                session->kernel_session->consumer_fd = kconsumerd_cmd_sock;
        }

        ret = mkdir_recursive(session->kernel_session->trace_path,
                        S_IRWXU | S_IRWXG, geteuid(), allowed_group());
        if (ret < 0) {
                if (ret != -EEXIST) {
                        ERR("Trace directory creation error");
                        goto error;
                }
        }

error:
        return ret;
}

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

        DBG("Getting all available session");
        /*
         * Iterate over session list and append data after the control struct in
         * the buffer.
         */
        cds_list_for_each_entry(session, &session_list_ptr->head, list) {
                strncpy(sessions[i].path, session->path, PATH_MAX);
                sessions[i].path[PATH_MAX - 1] = '\0';
                strncpy(sessions[i].name, session->name, NAME_MAX);
                sessions[i].name[NAME_MAX - 1] = '\0';
                i++;
        }
}

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

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

        /* Kernel channels */
        if (session->kernel_session != NULL) {
                cds_list_for_each_entry(kchan, &session->kernel_session->channel_list.head, list) {
                        /* Copy lttng_channel struct to array */
                        memcpy(&channels[i], kchan->channel, sizeof(struct lttng_channel));
                        channels[i].enabled = kchan->enabled;
                        i++;
                }
        }

        /* TODO: Missing UST listing */
}

/*
 * Fill lttng_event array of all events in the channel.
 */
static void list_lttng_events(struct ltt_kernel_channel *kchan,
                struct lttng_event *events)
{
        /*
         * TODO: This is ONLY kernel. Need UST support.
         */
        int i = 0;
        struct ltt_kernel_event *event;

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

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

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

        /*
         * Commands that DO NOT need a session.
         */
        switch (cmd_ctx->lsm->cmd_type) {
        case LTTNG_CREATE_SESSION:
        case LTTNG_LIST_SESSIONS:
        case LTTNG_LIST_TRACEPOINTS:
        case LTTNG_CALIBRATE:
                break;
        default:
                DBG("Getting session %s by name", cmd_ctx->lsm->session.name);
                cmd_ctx->session = find_session_by_name(cmd_ctx->lsm->session.name);
                if (cmd_ctx->session == NULL) {
                        /* If session name not found */
                        if (cmd_ctx->lsm->session.name != NULL) {
                                ret = LTTCOMM_SESS_NOT_FOUND;
                        } else {        /* If no session name specified */
                                ret = LTTCOMM_SELECT_SESS;
                        }
                        goto error;
                } else {
                        /* Acquire lock for the session */
                        lock_session(cmd_ctx->session);
                }
                break;
        }

        /*
         * Check domain type for specific "pre-action".
         */
        switch (cmd_ctx->lsm->domain.type) {
        case LTTNG_DOMAIN_KERNEL:
                /* Kernel tracer check */
                if (kernel_tracer_fd == 0) {
                        init_kernel_tracer();
                        if (kernel_tracer_fd == 0) {
                                ret = LTTCOMM_KERN_NA;
                                goto error;
                        }
                }
                /* Need a session for kernel command */
                switch (cmd_ctx->lsm->cmd_type) {
                case LTTNG_CALIBRATE:
                case LTTNG_CREATE_SESSION:
                case LTTNG_LIST_SESSIONS:
                case LTTNG_LIST_TRACEPOINTS:
                        break;
                default:
                        if (cmd_ctx->session->kernel_session == NULL) {
                                ret = create_kernel_session(cmd_ctx->session);
                                if (ret < 0) {
                                        ret = LTTCOMM_KERN_SESS_FAIL;
                                        goto error;
                                }
                                /* Start the kernel consumer daemon */
                                if (kconsumerd_pid == 0 &&
                                                cmd_ctx->lsm->cmd_type != LTTNG_REGISTER_CONSUMER) {
                                        ret = start_kconsumerd();
                                        if (ret < 0) {
                                                goto error;
                                        }
                                }
                        }
                }
                break;
        case LTTNG_DOMAIN_UST_PID:
                break;
        default:
                break;
        }

        /* Process by command type */
        switch (cmd_ctx->lsm->cmd_type) {
        case LTTNG_ADD_CONTEXT:
        {
                struct lttng_kernel_context kctx;

                /* Setup lttng message with no payload */
                ret = setup_lttng_msg(cmd_ctx, 0);
                if (ret < 0) {
                        goto setup_error;
                }

                switch (cmd_ctx->lsm->domain.type) {
                case LTTNG_DOMAIN_KERNEL:
                        /* Create Kernel context */
                        kctx.ctx = cmd_ctx->lsm->u.context.ctx.ctx;
                        kctx.u.perf_counter.type = cmd_ctx->lsm->u.context.ctx.u.perf_counter.type;
                        kctx.u.perf_counter.config = cmd_ctx->lsm->u.context.ctx.u.perf_counter.config;
                        strncpy(kctx.u.perf_counter.name,
                                        cmd_ctx->lsm->u.context.ctx.u.perf_counter.name,
                                        LTTNG_SYMBOL_NAME_LEN);
                        kctx.u.perf_counter.name[LTTNG_SYMBOL_NAME_LEN - 1] = '\0';

                        /* Add kernel context to kernel tracer. See context.c */
                        ret = add_kernel_context(cmd_ctx->session->kernel_session, &kctx,
                                        cmd_ctx->lsm->u.context.event_name,
                                        cmd_ctx->lsm->u.context.channel_name);
                        if (ret != LTTCOMM_OK) {
                                goto error;
                        }
                        break;
                default:
                        /* TODO: Userspace tracing */
                        ret = LTTCOMM_NOT_IMPLEMENTED;
                        goto error;
                }

                ret = LTTCOMM_OK;
                break;
        }
        case LTTNG_DISABLE_CHANNEL:
        {
                struct ltt_kernel_channel *kchan;

                /* Setup lttng message with no payload */
                ret = setup_lttng_msg(cmd_ctx, 0);
                if (ret < 0) {
                        goto setup_error;
                }

                switch (cmd_ctx->lsm->domain.type) {
                case LTTNG_DOMAIN_KERNEL:
                        kchan = trace_kernel_get_channel_by_name(cmd_ctx->lsm->u.disable.channel_name,
                                        cmd_ctx->session->kernel_session);
                        if (kchan == NULL) {
                                ret = LTTCOMM_KERN_CHAN_NOT_FOUND;
                                goto error;
                        } else if (kchan->enabled == 1) {
                                ret = kernel_disable_channel(kchan);
                                if (ret < 0) {
                                        if (ret != EEXIST) {
                                                ret = LTTCOMM_KERN_CHAN_DISABLE_FAIL;
                                        }
                                        goto error;
                                }
                        }
                        kernel_wait_quiescent(kernel_tracer_fd);
                        break;
                default:
                        /* TODO: Userspace tracing */
                        ret = LTTCOMM_NOT_IMPLEMENTED;
                        goto error;
                }

                ret = LTTCOMM_OK;
                break;
        }
        case LTTNG_DISABLE_EVENT:
        {
                struct ltt_kernel_channel *kchan;
                struct ltt_kernel_event *kevent;

                /* Setup lttng message with no payload */
                ret = setup_lttng_msg(cmd_ctx, 0);
                if (ret < 0) {
                        goto setup_error;
                }

                switch (cmd_ctx->lsm->domain.type) {
                case LTTNG_DOMAIN_KERNEL:
                        kchan = trace_kernel_get_channel_by_name(cmd_ctx->lsm->u.disable.channel_name,
                                        cmd_ctx->session->kernel_session);
                        if (kchan == NULL) {
                                ret = LTTCOMM_KERN_CHAN_NOT_FOUND;
                                goto error;
                        }

                        kevent = trace_kernel_get_event_by_name(cmd_ctx->lsm->u.disable.name, kchan);
                        if (kevent != NULL) {
                                DBG("Disabling kernel event %s for channel %s.", kevent->event->name,
                                                kchan->channel->name);
                                ret = kernel_disable_event(kevent);
                                if (ret < 0) {
                                        ret = LTTCOMM_KERN_ENABLE_FAIL;
                                        goto error;
                                }
                        }

                        kernel_wait_quiescent(kernel_tracer_fd);
                        break;
                default:
                        /* TODO: Userspace tracing */
                        ret = LTTCOMM_NOT_IMPLEMENTED;
                        goto error;
                }

                ret = LTTCOMM_OK;
                break;
        }
        case LTTNG_DISABLE_ALL_EVENT:
        {
                struct ltt_kernel_channel *kchan;
                struct ltt_kernel_event *kevent;

                /* Setup lttng message with no payload */
                ret = setup_lttng_msg(cmd_ctx, 0);
                if (ret < 0) {
                        goto setup_error;
                }

                switch (cmd_ctx->lsm->domain.type) {
                case LTTNG_DOMAIN_KERNEL:
                        DBG("Disabling all enabled kernel events");
                        kchan = trace_kernel_get_channel_by_name(cmd_ctx->lsm->u.disable.channel_name,
                                        cmd_ctx->session->kernel_session);
                        if (kchan == NULL) {
                                ret = LTTCOMM_KERN_CHAN_NOT_FOUND;
                                goto error;
                        }

                        /* For each event in the kernel session */
                        cds_list_for_each_entry(kevent, &kchan->events_list.head, list) {
                                DBG("Disabling kernel event %s for channel %s.",
                                                kevent->event->name, kchan->channel->name);
                                ret = kernel_disable_event(kevent);
                                if (ret < 0) {
                                        continue;
                                }
                        }

                        /* Quiescent wait after event disable */
                        kernel_wait_quiescent(kernel_tracer_fd);
                        break;
                default:
                        /* TODO: Userspace tracing */
                        ret = LTTCOMM_NOT_IMPLEMENTED;
                        goto error;
                }

                ret = LTTCOMM_OK;
                break;
        }
        case LTTNG_ENABLE_CHANNEL:
        {
                struct ltt_kernel_channel *kchan;

                /* Setup lttng message with no payload */
                ret = setup_lttng_msg(cmd_ctx, 0);
                if (ret < 0) {
                        goto setup_error;
                }

                switch (cmd_ctx->lsm->domain.type) {
                case LTTNG_DOMAIN_KERNEL:
                        kchan = trace_kernel_get_channel_by_name(cmd_ctx->lsm->u.enable.channel_name,
                                        cmd_ctx->session->kernel_session);
                        if (kchan == NULL) {
                                /* Channel not found, creating it */
                                DBG("Creating kernel channel");

                                ret = kernel_create_channel(cmd_ctx->session->kernel_session,
                                                &cmd_ctx->lsm->u.channel.chan,
                                                cmd_ctx->session->kernel_session->trace_path);
                                if (ret < 0) {
                                        ret = LTTCOMM_KERN_CHAN_FAIL;
                                        goto error;
                                }

                                /* Notify kernel thread that there is a new channel */
                                ret = notify_kernel_pollfd();
                                if (ret < 0) {
                                        ret = LTTCOMM_FATAL;
                                        goto error;
                                }
                        } else if (kchan->enabled == 0) {
                                ret = kernel_enable_channel(kchan);
                                if (ret < 0) {
                                        if (ret != EEXIST) {
                                                ret = LTTCOMM_KERN_CHAN_ENABLE_FAIL;
                                        }
                                        goto error;
                                }
                        }

                        kernel_wait_quiescent(kernel_tracer_fd);
                        break;
                case LTTNG_DOMAIN_UST_PID:

                        break;
                default:
                        ret = LTTCOMM_NOT_IMPLEMENTED;
                        goto error;
                }

                ret = LTTCOMM_OK;
                break;
        }
        case LTTNG_ENABLE_EVENT:
        {
                char *channel_name;
                struct ltt_kernel_channel *kchan;
                struct ltt_kernel_event *kevent;
                struct lttng_channel *chan;

                /* Setup lttng message with no payload */
                ret = setup_lttng_msg(cmd_ctx, 0);
                if (ret < 0) {
                        goto setup_error;
                }

                channel_name = cmd_ctx->lsm->u.enable.channel_name;

                switch (cmd_ctx->lsm->domain.type) {
                case LTTNG_DOMAIN_KERNEL:
                        kchan = trace_kernel_get_channel_by_name(channel_name,
                                        cmd_ctx->session->kernel_session);
                        if (kchan == NULL) {
                                DBG("Channel not found. Creating channel %s", channel_name);

                                chan = init_default_channel(cmd_ctx->lsm->domain.type, channel_name);
                                if (chan == NULL) {
                                        ret = LTTCOMM_FATAL;
                                        goto error;
                                }

                                ret = kernel_create_channel(cmd_ctx->session->kernel_session,
                                                chan, cmd_ctx->session->kernel_session->trace_path);
                                if (ret < 0) {
                                        ret = LTTCOMM_KERN_CHAN_FAIL;
                                        goto error;
                                }
                                kchan = trace_kernel_get_channel_by_name(channel_name,
                                                cmd_ctx->session->kernel_session);
                                if (kchan == NULL) {
                                        ERR("Channel %s not found after creation. Internal error, giving up.",
                                                channel_name);
                                        ret = LTTCOMM_FATAL;
                                        goto error;
                                }
                        }

                        kevent = trace_kernel_get_event_by_name(cmd_ctx->lsm->u.enable.event.name, kchan);
                        if (kevent == NULL) {
                                DBG("Creating kernel event %s for channel %s.",
                                                cmd_ctx->lsm->u.enable.event.name, channel_name);
                                ret = kernel_create_event(&cmd_ctx->lsm->u.enable.event, kchan);
                        } else {
                                DBG("Enabling kernel event %s for channel %s.",
                                                kevent->event->name, channel_name);
                                ret = kernel_enable_event(kevent);
                                if (ret == -EEXIST) {
                                        ret = LTTCOMM_KERN_EVENT_EXIST;
                                        goto error;
                                }
                        }

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

                        kernel_wait_quiescent(kernel_tracer_fd);
                        break;
                default:
                        /* TODO: Userspace tracing */
                        ret = LTTCOMM_NOT_IMPLEMENTED;
                        goto error;
                }
                ret = LTTCOMM_OK;
                break;
        }
        case LTTNG_ENABLE_ALL_EVENT:
        {
                int size, i;
                char *channel_name;
                struct ltt_kernel_channel *kchan;
                struct ltt_kernel_event *kevent;
                struct lttng_event *event_list;
                struct lttng_channel *chan;

                /* Setup lttng message with no payload */
                ret = setup_lttng_msg(cmd_ctx, 0);
                if (ret < 0) {
                        goto setup_error;
                }

                DBG("Enabling all kernel event");

                channel_name = cmd_ctx->lsm->u.enable.channel_name;

                switch (cmd_ctx->lsm->domain.type) {
                case LTTNG_DOMAIN_KERNEL:
                        kchan = trace_kernel_get_channel_by_name(channel_name,
                                        cmd_ctx->session->kernel_session);
                        if (kchan == NULL) {
                                DBG("Channel not found. Creating channel %s", channel_name);

                                chan = init_default_channel(cmd_ctx->lsm->domain.type, channel_name);
                                if (chan == NULL) {
                                        ret = LTTCOMM_FATAL;
                                        goto error;
                                }

                                ret = kernel_create_channel(cmd_ctx->session->kernel_session,
                                                chan, cmd_ctx->session->kernel_session->trace_path);
                                if (ret < 0) {
                                        ret = LTTCOMM_KERN_CHAN_FAIL;
                                        goto error;
                                }
                                kchan = trace_kernel_get_channel_by_name(channel_name,
                                                cmd_ctx->session->kernel_session);
                                if (kchan == NULL) {
                                        ERR("Channel %s not found after creation. Internal error, giving up.",
                                                channel_name);
                                        ret = LTTCOMM_FATAL;
                                        goto error;
                                }
                        }

                        /* For each event in the kernel session */
                        cds_list_for_each_entry(kevent, &kchan->events_list.head, list) {
                                DBG("Enabling kernel event %s for channel %s.",
                                                kevent->event->name, channel_name);
                                ret = kernel_enable_event(kevent);
                                if (ret < 0) {
                                        continue;
                                }
                        }

                        size = kernel_list_events(kernel_tracer_fd, &event_list);
                        if (size < 0) {
                                ret = LTTCOMM_KERN_LIST_FAIL;
                                goto error;
                        }

                        for (i = 0; i < size; i++) {
                                kevent = trace_kernel_get_event_by_name(event_list[i].name, kchan);
                                if (kevent == NULL) {
                                        /* Default event type for enable all */
                                        event_list[i].type = LTTNG_EVENT_TRACEPOINT;
                                        /* Enable each single tracepoint event */
                                        ret = kernel_create_event(&event_list[i], kchan);
                                        if (ret < 0) {
                                                /* Ignore error here and continue */
                                        }
                                }
                        }

                        free(event_list);

                        /* Quiescent wait after event enable */
                        kernel_wait_quiescent(kernel_tracer_fd);
                        break;
                default:
                        /* TODO: Userspace tracing */
                        ret = LTTCOMM_NOT_IMPLEMENTED;
                        goto error;
                }

                ret = LTTCOMM_OK;
                break;
        }
        case LTTNG_LIST_TRACEPOINTS:
        {
                struct lttng_event *events;
                ssize_t nb_events = 0;

                switch (cmd_ctx->lsm->domain.type) {
                case LTTNG_DOMAIN_KERNEL:
                        DBG("Listing kernel events");
                        nb_events = kernel_list_events(kernel_tracer_fd, &events);
                        if (nb_events < 0) {
                                ret = LTTCOMM_KERN_LIST_FAIL;
                                goto error;
                        }
                        break;
                default:
                        /* TODO: Userspace listing */
                        ret = LTTCOMM_NOT_IMPLEMENTED;
                        break;
                }

                /*
                 * 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 = LTTCOMM_OK;
                break;
        }
        case LTTNG_START_TRACE:
        {
                struct ltt_kernel_channel *chan;

                /* Setup lttng message with no payload */
                ret = setup_lttng_msg(cmd_ctx, 0);
                if (ret < 0) {
                        goto setup_error;
                }

                /* Kernel tracing */
                if (cmd_ctx->session->kernel_session != NULL) {
                        if (cmd_ctx->session->kernel_session->metadata == NULL) {
                                DBG("Open kernel metadata");
                                ret = kernel_open_metadata(cmd_ctx->session->kernel_session,
                                                cmd_ctx->session->kernel_session->trace_path);
                                if (ret < 0) {
                                        ret = LTTCOMM_KERN_META_FAIL;
                                        goto error;
                                }
                        }

                        if (cmd_ctx->session->kernel_session->metadata_stream_fd == 0) {
                                DBG("Opening kernel metadata stream");
                                if (cmd_ctx->session->kernel_session->metadata_stream_fd == 0) {
                                        ret = kernel_open_metadata_stream(cmd_ctx->session->kernel_session);
                                        if (ret < 0) {
                                                ERR("Kernel create metadata stream failed");
                                                ret = LTTCOMM_KERN_STREAM_FAIL;
                                                goto error;
                                        }
                                }
                        }

                        /* For each channel */
                        cds_list_for_each_entry(chan,
                                        &cmd_ctx->session->kernel_session->channel_list.head, list) {
                                if (chan->stream_count == 0) {
                                        ret = kernel_open_channel_stream(chan);
                                        if (ret < 0) {
                                                ERR("Kernel create channel stream failed");
                                                ret = LTTCOMM_KERN_STREAM_FAIL;
                                                goto error;
                                        }
                                        /* Update the stream global counter */
                                        cmd_ctx->session->kernel_session->stream_count_global += ret;
                                }
                        }

                        ret = start_kernel_trace(cmd_ctx->session->kernel_session);
                        if (ret < 0) {
                                ret = LTTCOMM_KERN_START_FAIL;
                                goto error;
                        }

                        DBG("Start kernel tracing");
                        ret = kernel_start_session(cmd_ctx->session->kernel_session);
                        if (ret < 0) {
                                ERR("Kernel start session failed");
                                ret = LTTCOMM_KERN_START_FAIL;
                                goto error;
                        }

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

                /* TODO: Start all UST traces */

                ret = LTTCOMM_OK;
                break;
        }
        case LTTNG_STOP_TRACE:
        {
                struct ltt_kernel_channel *chan;
                /* Setup lttng message with no payload */
                ret = setup_lttng_msg(cmd_ctx, 0);
                if (ret < 0) {
                        goto setup_error;
                }

                /* Kernel tracer */
                if (cmd_ctx->session->kernel_session != NULL) {
                        DBG("Stop kernel tracing");

                        ret = kernel_metadata_flush_buffer(cmd_ctx->session->kernel_session->metadata_stream_fd);
                        if (ret < 0) {
                                ERR("Kernel metadata flush failed");
                        }

                        cds_list_for_each_entry(chan, &cmd_ctx->session->kernel_session->channel_list.head, list) {
                                ret = kernel_flush_buffer(chan);
                                if (ret < 0) {
                                        ERR("Kernel flush buffer error");
                                }
                        }

                        ret = kernel_stop_session(cmd_ctx->session->kernel_session);
                        if (ret < 0) {
                                ERR("Kernel stop session failed");
                                ret = LTTCOMM_KERN_STOP_FAIL;
                                goto error;
                        }

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

                /* TODO : User-space tracer */

                ret = LTTCOMM_OK;
                break;
        }
        case LTTNG_CREATE_SESSION:
        {
                /* Setup lttng message with no payload */
                ret = setup_lttng_msg(cmd_ctx, 0);
                if (ret < 0) {
                        goto setup_error;
                }

                ret = create_session(cmd_ctx->lsm->session.name, cmd_ctx->lsm->session.path);
                if (ret < 0) {
                        if (ret == -EEXIST) {
                                ret = LTTCOMM_EXIST_SESS;
                        } else {
                                ret = LTTCOMM_FATAL;
                        }
                        goto error;
                }

                ret = LTTCOMM_OK;
                break;
        }
        case LTTNG_DESTROY_SESSION:
        {
                /* Setup lttng message with no payload */
                ret = setup_lttng_msg(cmd_ctx, 0);
                if (ret < 0) {
                        goto setup_error;
                }

                /* Clean kernel session teardown */
                teardown_kernel_session(cmd_ctx->session);

                ret = destroy_session(cmd_ctx->lsm->session.name);
                if (ret < 0) {
                        ret = LTTCOMM_FATAL;
                        goto error;
                }

                /*
                 * Must notify the kernel thread here to update it's pollfd in order to
                 * remove the channel(s)' fd just destroyed.
                 */
                ret = notify_kernel_pollfd();
                if (ret < 0) {
                        ret = LTTCOMM_FATAL;
                        goto error;
                }

                ret = LTTCOMM_OK;
                break;
        }
        case LTTNG_LIST_DOMAINS:
        {
                size_t nb_dom = 0;

                if (cmd_ctx->session->kernel_session != NULL) {
                        nb_dom++;
                }

                nb_dom += cmd_ctx->session->ust_session_list.count;

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

                ((struct lttng_domain *)(cmd_ctx->llm->payload))[0].type =
                        LTTNG_DOMAIN_KERNEL;

                /* TODO: User-space tracer domain support */
                ret = LTTCOMM_OK;
                break;
        }
        case LTTNG_LIST_CHANNELS:
        {
                /*
                 * TODO: Only kernel channels are listed here. UST listing
                 * is needed on lttng-ust 2.0 release.
                 */
                size_t nb_chan = 0;
                if (cmd_ctx->session->kernel_session != NULL) {
                        nb_chan += cmd_ctx->session->kernel_session->channel_count;
                }

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

                list_lttng_channels(cmd_ctx->session,
                                (struct lttng_channel *)(cmd_ctx->llm->payload));

                ret = LTTCOMM_OK;
                break;
        }
        case LTTNG_LIST_EVENTS:
        {
                /*
                 * TODO: Only kernel events are listed here. UST listing
                 * is needed on lttng-ust 2.0 release.
                 */
                size_t nb_event = 0;
                struct ltt_kernel_channel *kchan = NULL;

                if (cmd_ctx->session->kernel_session != NULL) {
                        kchan = trace_kernel_get_channel_by_name(cmd_ctx->lsm->u.list.channel_name,
                                        cmd_ctx->session->kernel_session);
                        if (kchan == NULL) {
                                ret = LTTCOMM_KERN_CHAN_NOT_FOUND;
                                goto error;
                        }
                        nb_event += kchan->event_count;
                }

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

                DBG("Listing events (%zu events)", nb_event);

                list_lttng_events(kchan,
                                (struct lttng_event *)(cmd_ctx->llm->payload));

                ret = LTTCOMM_OK;
                break;
        }
        case LTTNG_LIST_SESSIONS:
        {
                lock_session_list();

                if (session_list_ptr->count == 0) {
                        ret = LTTCOMM_NO_SESSION;
                        unlock_session_list();
                        goto error;
                }

                ret = setup_lttng_msg(cmd_ctx, sizeof(struct lttng_session) *
                                session_list_ptr->count);
                if (ret < 0) {
                        unlock_session_list();
                        goto setup_error;
                }

                /* Filled the session array */
                list_lttng_sessions((struct lttng_session *)(cmd_ctx->llm->payload));

                unlock_session_list();

                ret = LTTCOMM_OK;
                break;
        }
        case LTTNG_CALIBRATE:
        {
                /* Setup lttng message with no payload */
                ret = setup_lttng_msg(cmd_ctx, 0);
                if (ret < 0) {
                        goto setup_error;
                }

                switch (cmd_ctx->lsm->domain.type) {
                case LTTNG_DOMAIN_KERNEL:
                {
                        struct lttng_kernel_calibrate kcalibrate;

                        kcalibrate.type = cmd_ctx->lsm->u.calibrate.type;
                        ret = kernel_calibrate(kernel_tracer_fd, &kcalibrate);
                        if (ret < 0) {
                                ret = LTTCOMM_KERN_ENABLE_FAIL;
                                goto error;
                        }
                        break;
                }
                default:
                        /* TODO: Userspace tracing */
                        ret = LTTCOMM_NOT_IMPLEMENTED;
                        goto error;
                }
                ret = LTTCOMM_OK;
                break;
        }
        case LTTNG_REGISTER_CONSUMER:
        {
                int sock;

                /* Setup lttng message with no payload */
                ret = setup_lttng_msg(cmd_ctx, 0);
                if (ret < 0) {
                        goto setup_error;
                }

                switch (cmd_ctx->lsm->domain.type) {
                case LTTNG_DOMAIN_KERNEL:
                        {
                                /* Can't register a consumer if there is already one */
                                if (cmd_ctx->session->kernel_session->consumer_fd != 0) {
                                        ret = LTTCOMM_CONNECT_FAIL;
                                        goto error;
                                }

                                sock = lttcomm_connect_unix_sock(cmd_ctx->lsm->u.reg.path);
                                if (sock < 0) {
                                        ret = LTTCOMM_CONNECT_FAIL;
                                        goto error;
                                }

                                cmd_ctx->session->kernel_session->consumer_fd = sock;
                                break;
                        }
                default:
                        /* TODO: Userspace tracing */
                        ret = LTTCOMM_NOT_IMPLEMENTED;
                        goto error;
                }

                ret = LTTCOMM_OK;
                break;
        }

        default:
                /* Undefined command */
                ret = setup_lttng_msg(cmd_ctx, 0);
                if (ret < 0) {
                        goto setup_error;
                }

                ret = LTTCOMM_UND;
                break;
        }

        /* Set return code */
        cmd_ctx->llm->ret_code = ret;

        if (cmd_ctx->session) {
                unlock_session(cmd_ctx->session);
        }

        return ret;

error:
        if (cmd_ctx->llm == NULL) {
                DBG("Missing llm structure. Allocating one.");
                if (setup_lttng_msg(cmd_ctx, 0) < 0) {
                        goto setup_error;
                }
        }
        /* Notify client of error */
        cmd_ctx->llm->ret_code = ret;

setup_error:
        if (cmd_ctx->session) {
                unlock_session(cmd_ctx->session);
        }
        return ret;
}

/*
 * This thread manage all clients request using the unix client socket for
 * communication.
 */
static void *thread_manage_clients(void *data)
{
        int sock = 0, ret;
        struct command_ctx *cmd_ctx = NULL;
        struct pollfd pollfd[2];

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

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

        /* First fd is always the quit pipe */
        pollfd[0].fd = thread_quit_pipe[0];
        pollfd[0].events =
                POLLHUP | POLLNVAL | POLLERR | POLLIN | POLLRDHUP | POLLPRI;

        /* Apps socket */
        pollfd[1].fd = client_sock;
        pollfd[1].events = POLLIN;

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

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

                /* Inifinite blocking call, waiting for transmission */
                ret = poll(pollfd, 2, -1);
                if (ret < 0) {
                        perror("poll client thread");
                        goto error;
                }

                /* Thread quit pipe has been closed. Killing thread. */
                if (pollfd[0].revents == POLLNVAL) {
                        goto error;
                } else if (pollfd[1].revents == POLLERR) {
                        ERR("Client socket poll error");
                        goto error;
                }

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

                /* Allocate context command to process the client request */
                cmd_ctx = malloc(sizeof(struct command_ctx));

                /* Allocate data buffer for reception */
                cmd_ctx->lsm = malloc(sizeof(struct lttcomm_session_msg));
                cmd_ctx->llm = NULL;
                cmd_ctx->session = NULL;

                /*
                 * 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_unix_sock(sock, cmd_ctx->lsm, sizeof(struct lttcomm_session_msg));
                if (ret <= 0) {
                        continue;
                }

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

                /*
                 * 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);
                if (ret < 0) {
                        /* TODO: Inform client somehow of the fatal error. At this point,
                         * ret < 0 means that a malloc failed (ENOMEM). */
                        /* Error detected but still accept command */
                        clean_command_ctx(&cmd_ctx);
                        continue;
                }

                DBG("Sending response (size: %d, retcode: %d)",
                                cmd_ctx->lttng_msg_size, 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");
                }

                clean_command_ctx(&cmd_ctx);

                /* End of transmission */
                close(sock);
        }

error:
        DBG("Client thread dying");
        if (client_sock) {
                close(client_sock);
        }
        if (sock) {
                close(sock);
        }

        unlink(client_unix_sock_path);

        clean_command_ctx(&cmd_ctx);
        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, "  -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 SIGCHLD 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, "      --verbose-kconsumerd           Verbose mode for kconsumerd. Activate DBG() macro.\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, 0 },
                { "kconsumerd-err-sock", 1, 0, 0 },
                { "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-kconsumerd", 0, 0, 'Z' },
                { NULL, 0, 0, 0 }
        };

        while (1) {
                int option_index = 0;
                c = getopt_long(argc, argv, "dhqvVS" "a:c:g:s:E:C:Z", 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 = strdup(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(kconsumerd_err_unix_sock_path, PATH_MAX, "%s", optarg);
                        break;
                case 'C':
                        snprintf(kconsumerd_cmd_unix_sock_path, PATH_MAX, "%s", optarg);
                        break;
                case 'q':
                        opt_quiet = 1;
                        break;
                case 'v':
                        /* Verbose level can increase using multiple -v */
                        opt_verbose += 1;
                        break;
                case 'Z':
                        opt_verbose_kconsumerd += 1;
                        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;
        }

        /* 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;
        }

        /* 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;
        }

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)
{
        if (access(client_unix_sock_path, F_OK) < 0 &&
                        access(apps_unix_sock_path, F_OK) < 0) {
                return 0;
        }
        /* Is there anybody out there ? */
        if (lttng_session_daemon_alive()) {
                return -EEXIST;
        } else {
                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 les permissive (root.tracing).
 */
static int set_permissions(void)
{
        int ret;
        gid_t gid;

        gid = allowed_group();
        if (gid < 0) {
                if (is_root) {
                        WARN("No tracing group detected");
                        ret = 0;
                } else {
                        ERR("Missing tracing group. Aborting execution.");
                        ret = -1;
                }
                goto end;
        }

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

        /* 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");
        }

        /* kconsumerd error socket path */
        ret = chown(kconsumerd_err_unix_sock_path, 0, gid);
        if (ret < 0) {
                ERR("Unable to set group on %s", kconsumerd_err_unix_sock_path);
                perror("chown");
        }

        DBG("All permissions are set");

end:
        return ret;
}

/*
 * Create the pipe used to wake up the kernel thread.
 */
static int create_kernel_poll_pipe(void)
{
        return pipe2(kernel_poll_pipe, O_CLOEXEC);
}

/*
 * Create the application command pipe to wake thread_manage_apps.
 */
static int create_apps_cmd_pipe(void)
{
        return pipe2(apps_cmd_pipe, O_CLOEXEC);
}

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

        ret = mkdir(LTTNG_RUNDIR, S_IRWXU | S_IRWXG );
        if (ret < 0) {
                if (errno != EEXIST) {
                        ERR("Unable to create " LTTNG_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_kconsumerd_sockets(void)
{
        int ret;

        if (strlen(kconsumerd_err_unix_sock_path) == 0) {
                snprintf(kconsumerd_err_unix_sock_path, PATH_MAX, KCONSUMERD_ERR_SOCK_PATH);
        }

        if (strlen(kconsumerd_cmd_unix_sock_path) == 0) {
                snprintf(kconsumerd_cmd_unix_sock_path, PATH_MAX, KCONSUMERD_CMD_SOCK_PATH);
        }

        ret = mkdir(KCONSUMERD_PATH, S_IRWXU | S_IRWXG);
        if (ret < 0) {
                if (errno != EEXIST) {
                        ERR("Failed to create " KCONSUMERD_PATH);
                        goto error;
                }
                ret = 0;
        }

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

        /* File permission MUST be 660 */
        ret = chmod(kconsumerd_err_unix_sock_path, S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP);
        if (ret < 0) {
                ERR("Set file permissions failed: %s", kconsumerd_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 catched");
                return;
        case SIGINT:
                DBG("SIGINT catched");
                stop_threads();
                break;
        case SIGTERM:
                DBG("SIGTERM catched");
                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");
        }
}

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

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

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

        /* Daemonize */
        if (opt_daemon) {
                ret = daemon(0, 0);
                if (ret < 0) {
                        perror("daemon");
                        goto error;
                }
        }

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

        if (is_root) {
                ret = create_lttng_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);
                }
        } else {
                home_path = 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;
                }

                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, geteuid());
                }
        }

        DBG("Client socket path %s", client_unix_sock_path);
        DBG("Application socket path %s", apps_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;
        }

        /* After this point, we can safely call cleanup() so goto error is used */

        /*
         * 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_kconsumerd_sockets();
                if (ret < 0) {
                        goto exit;
                }

                /* Setup kernel tracer */
                init_kernel_tracer();

                /* Set ulimit for open files */
                set_ulimit();
        }

        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()) < 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 ((ret = create_kernel_poll_pipe()) < 0) {
                goto exit;
        }

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

        /* 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 = get_session_list();

        /* 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 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_kconsumerd_thread();
        if (ret != 0) {
                perror("join_kconsumerd");
                goto error;     /* join error, exit without cleanup */
        }

exit_client:
exit:
        /*
         * cleanup() is called when no other thread is running.
         */
        cleanup();
        if (!ret)
                exit(EXIT_SUCCESS);
error:
        exit(EXIT_FAILURE);
}