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 <pthread.h>
  22 #include <stdio.h>
  23 #include <stdlib.h>
  24 #include <string.h>
  25 #include <urcu/list.h>
  26
  27 #include <lttngerr.h>
  28
  29 #include "session.h"
  30
  31 /*
  32  * NOTES:
  33  *
  34  * No ltt_session.lock is taken here because those data structure are widely
  35  * spread across the lttng-tools code base so before caling functions below
  36  * that can read/write a session, the caller MUST acquire the session lock
  37  * using lock_session() and unlock_session().
  38  */
  39
  40 /*
  41  * Init tracing session list.
  42  *
  43  * Please see session.h for more explanation and correct usage of the list.
  44  */
  45 static struct ltt_session_list ltt_session_list = {
  46         .head = CDS_LIST_HEAD_INIT(ltt_session_list.head),
  47         .lock = PTHREAD_MUTEX_INITIALIZER,
  48         .count = 0,
  49 };
  50
  51 /*
  52  * Add a ltt_session structure to the global list.
  53  *
  54  * The caller MUST acquire the session list lock before.
  55  */
  56 static void add_session_list(struct ltt_session *ls)
  57 {
  58         cds_list_add(&ls->list, &ltt_session_list.head);
  59         ltt_session_list.count++;
  60 }
  61
  62 /*
  63  * Delete a ltt_session structure to the global list.
  64  *
  65  * The caller MUST acquire the session list lock before.
  66  */
  67 static void del_session_list(struct ltt_session *ls)
  68 {
  69         cds_list_del(&ls->list);
  70         /* Sanity check */
  71         if (ltt_session_list.count > 0) {
  72                 ltt_session_list.count--;
  73         }
  74 }
  75
  76 /*
  77  * Return a pointer to the session list.
  78  */
  79 struct ltt_session_list *get_session_list(void)
  80 {
  81         return &ltt_session_list;
  82 }
  83
  84 /*
  85  * Acquire session list lock
  86  */
  87 void lock_session_list(void)
  88 {
  89         pthread_mutex_lock(&ltt_session_list.lock);
  90 }
  91
  92 /*
  93  * Release session list lock
  94  */
  95 void unlock_session_list(void)
  96 {
  97         pthread_mutex_unlock(&ltt_session_list.lock);
  98 }
  99
 100 /*
 101  * Acquire session lock
 102  */
 103 void lock_session(struct ltt_session *session)
 104 {
 105         pthread_mutex_lock(&session->lock);
 106 }
 107
 108 /*
 109  * Release session lock
 110  */
 111 void unlock_session(struct ltt_session *session)
 112 {
 113         pthread_mutex_unlock(&session->lock);
 114 }
 115
 116 /*
 117  * Return a ltt_session structure ptr that matches name.
 118  * If no session found, NULL is returned.
 119  */
 120 struct ltt_session *find_session_by_name(char *name)
 121 {
 122         int found = 0;
 123         struct ltt_session *iter;
 124
 125         lock_session_list();
 126         cds_list_for_each_entry(iter, &ltt_session_list.head, list) {
 127                 if (strncmp(iter->name, name, NAME_MAX) == 0) {
 128                         found = 1;
 129                         break;
 130                 }
 131         }
 132         unlock_session_list();
 133
 134         if (!found) {
 135                 iter = NULL;
 136         }
 137
 138         return iter;
 139 }
 140
 141 /*
 142  * Delete session from the session list and free the memory.
 143  *
 144  * Return -1 if no session is found.  On success, return 1;
 145  */
 146 int destroy_session(char *name)
 147 {
 148         int found = -1;
 149         struct ltt_session *iter, *tmp;
 150
 151         lock_session_list();
 152         cds_list_for_each_entry_safe(iter, tmp, &ltt_session_list.head, list) {
 153                 if (strcmp(iter->name, name) == 0) {
 154                         DBG("Destroying session %s", iter->name);
 155                         del_session_list(iter);
 156                         free(iter->name);
 157                         free(iter->path);
 158                         pthread_mutex_destroy(&iter->lock);
 159                         free(iter);
 160                         found = 1;
 161                         break;
 162                 }
 163         }
 164         unlock_session_list();
 165
 166         return found;
 167 }
 168
 169 /*
 170  * Create a brand new session and add it to the session list.
 171  */
 172 int create_session(char *name, char *path)
 173 {
 174         int ret;
 175         struct ltt_session *new_session;
 176
 177         new_session = find_session_by_name(name);
 178         if (new_session != NULL) {
 179                 ret = -EEXIST;
 180                 goto error_exist;
 181         }
 182
 183         /* Allocate session data structure */
 184         new_session = malloc(sizeof(struct ltt_session));
 185         if (new_session == NULL) {
 186                 perror("malloc");
 187                 ret = -ENOMEM;
 188                 goto error_malloc;
 189         }
 190
 191         /* Define session name */
 192         if (name != NULL) {
 193                 if (asprintf(&new_session->name, "%s", name) < 0) {
 194                         ret = -ENOMEM;
 195                         goto error_asprintf;
 196                 }
 197         } else {
 198                 ERR("No session name given");
 199                 ret = -1;
 200                 goto error;
 201         }
 202
 203         /* Define session system path */
 204         if (path != NULL) {
 205                 if (asprintf(&new_session->path, "%s", path) < 0) {
 206                         ret = -ENOMEM;
 207                         goto error_asprintf;
 208                 }
 209         } else {
 210                 ERR("No session path given");
 211                 ret = -1;
 212                 goto error;
 213         }
 214
 215         /* Init kernel session */
 216         new_session->kernel_session = NULL;
 217
 218         /* Init list */
 219         CDS_INIT_LIST_HEAD(&new_session->ust_traces);
 220
 221         /* Set trace list counter */
 222         new_session->ust_trace_count = 0;
 223
 224         /* Add new session to the session list */
 225         lock_session_list();
 226         add_session_list(new_session);
 227         unlock_session_list();
 228
 229         /* Init lock */
 230         pthread_mutex_init(&new_session->lock, NULL);
 231
 232         DBG("Tracing session %s created in %s", new_session->name, new_session->path);
 233
 234         return 0;
 235
 236 error:
 237 error_asprintf:
 238         if (new_session != NULL) {
 239                 free(new_session);
 240         }
 241
 242 error_exist:
 243 error_malloc:
 244         return ret;
 245 }