ltt-sessiond/session.c

   1 /*
   2  * Copyright (C)  2011 - David Goulet <david.goulet@polymtl.ca>
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public License
   6  * as published by the Free Software Foundation; only version 2
   7  * of the License.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, write to the Free Software
  16  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
  17  */
  18
  19 #define _GNU_SOURCE
  20 #include <limits.h>
  21 #include <stdio.h>
  22 #include <stdlib.h>
  23 #include <string.h>
  24
  25 #include <lttng-sessiond-comm.h>
  26 #include <lttngerr.h>
  27
  28 #include "session.h"
  29
  30 /*
  31  * NOTES:
  32  *
  33  * No ltt_session.lock is taken here because those data structure are widely
  34  * spread across the lttng-tools code base so before caling functions below
  35  * that can read/write a session, the caller MUST acquire the session lock
  36  * using session_lock() and session_unlock().
  37  */
  38
  39 /*
  40  * Init tracing session list.
  41  *
  42  * Please see session.h for more explanation and correct usage of the list.
  43  */
  44 static struct ltt_session_list ltt_session_list = {
  45         .head = CDS_LIST_HEAD_INIT(ltt_session_list.head),
  46         .lock = PTHREAD_MUTEX_INITIALIZER,
  47         .count = 0,
  48 };
  49
  50 /*
  51  * Add a ltt_session structure to the global list.
  52  *
  53  * The caller MUST acquire the session list lock before.
  54  */
  55 static void add_session_list(struct ltt_session *ls)
  56 {
  57         cds_list_add(&ls->list, &ltt_session_list.head);
  58         ltt_session_list.count++;
  59 }
  60
  61 /*
  62  * Delete a ltt_session structure to the global list.
  63  *
  64  * The caller MUST acquire the session list lock before.
  65  */
  66 static void del_session_list(struct ltt_session *ls)
  67 {
  68         cds_list_del(&ls->list);
  69         /* Sanity check */
  70         if (ltt_session_list.count > 0) {
  71                 ltt_session_list.count--;
  72         }
  73 }
  74
  75 /*
  76  * Return a pointer to the session list.
  77  */
  78 struct ltt_session_list *session_get_list(void)
  79 {
  80         return &ltt_session_list;
  81 }
  82
  83 /*
  84  * Acquire session list lock
  85  */
  86 void session_lock_list(void)
  87 {
  88         pthread_mutex_lock(&ltt_session_list.lock);
  89 }
  90
  91 /*
  92  * Release session list lock
  93  */
  94 void session_unlock_list(void)
  95 {
  96         pthread_mutex_unlock(&ltt_session_list.lock);
  97 }
  98
  99 /*
 100  * Acquire session lock
 101  */
 102 void session_lock(struct ltt_session *session)
 103 {
 104         pthread_mutex_lock(&session->lock);
 105 }
 106
 107 /*
 108  * Release session lock
 109  */
 110 void session_unlock(struct ltt_session *session)
 111 {
 112         pthread_mutex_unlock(&session->lock);
 113 }
 114
 115 /*
 116  * Return a ltt_session structure ptr that matches name. If no session found,
 117  * NULL is returned. This must be called with the session lock held using
 118  * session_lock_list and session_unlock_list.
 119  */
 120 struct ltt_session *session_find_by_name(char *name)
 121 {
 122         struct ltt_session *iter;
 123
 124         DBG2("Trying to find session by name %s", name);
 125
 126         cds_list_for_each_entry(iter, &ltt_session_list.head, list) {
 127                 if (strncmp(iter->name, name, NAME_MAX) == 0) {
 128                         goto found;
 129                 }
 130         }
 131
 132         iter = NULL;
 133
 134 found:
 135         return iter;
 136 }
 137
 138 /*
 139  * Delete session from the session list and free the memory.
 140  *
 141  * Return -1 if no session is found.  On success, return 1;
 142  */
 143 int session_destroy(struct ltt_session *session)
 144 {
 145         /* Safety check */
 146         if (session == NULL) {
 147                 ERR("Session pointer was null on session destroy");
 148                 return LTTCOMM_OK;
 149         }
 150
 151         DBG("Destroying session %s", session->name);
 152         del_session_list(session);
 153         pthread_mutex_destroy(&session->lock);
 154         free(session);
 155
 156         return LTTCOMM_OK;
 157 }
 158
 159 /*
 160  * Create a brand new session and add it to the session list.
 161  */
 162 int session_create(char *name, char *path)
 163 {
 164         int ret;
 165         struct ltt_session *new_session;
 166
 167         new_session = session_find_by_name(name);
 168         if (new_session != NULL) {
 169                 ret = LTTCOMM_EXIST_SESS;
 170                 goto error_exist;
 171         }
 172
 173         /* Allocate session data structure */
 174         new_session = malloc(sizeof(struct ltt_session));
 175         if (new_session == NULL) {
 176                 perror("malloc");
 177                 ret = LTTCOMM_FATAL;
 178                 goto error_malloc;
 179         }
 180
 181         /* Define session name */
 182         if (name != NULL) {
 183                 if (snprintf(new_session->name, NAME_MAX, "%s", name) < 0) {
 184                         ret = LTTCOMM_FATAL;
 185                         goto error_asprintf;
 186                 }
 187         } else {
 188                 ERR("No session name given");
 189                 ret = LTTCOMM_FATAL;
 190                 goto error;
 191         }
 192
 193         /* Define session system path */
 194         if (path != NULL) {
 195                 if (snprintf(new_session->path, PATH_MAX, "%s", path) < 0) {
 196                         ret = LTTCOMM_FATAL;
 197                         goto error_asprintf;
 198                 }
 199         } else {
 200                 ERR("No session path given");
 201                 ret = LTTCOMM_FATAL;
 202                 goto error;
 203         }
 204
 205         /* Init kernel session */
 206         new_session->kernel_session = NULL;
 207
 208         /* Init UST session list */
 209         CDS_INIT_LIST_HEAD(&new_session->ust_session_list.head);
 210
 211         /* Init lock */
 212         pthread_mutex_init(&new_session->lock, NULL);
 213
 214         /* Add new session to the session list */
 215         session_lock_list();
 216         add_session_list(new_session);
 217         session_unlock_list();
 218
 219         DBG("Tracing session %s created in %s", name, path);
 220
 221         return LTTCOMM_OK;
 222
 223 error:
 224 error_asprintf:
 225         if (new_session != NULL) {
 226                 free(new_session);
 227         }
 228
 229 error_exist:
 230 error_malloc:
 231         return ret;
 232 }