lttng-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 #include <urcu.h>
  25
  26 #include <lttng-sessiond-comm.h>
  27 #include <lttngerr.h>
  28
  29 #include "hashtable.h"
  30 #include "session.h"
  31
  32 #include "../hashtable/hash.h"
  33
  34 /*
  35  * NOTES:
  36  *
  37  * No ltt_session.lock is taken here because those data structure are widely
  38  * spread across the lttng-tools code base so before caling functions below
  39  * that can read/write a session, the caller MUST acquire the session lock
  40  * using session_lock() and session_unlock().
  41  */
  42
  43 /*
  44  * Init tracing session list.
  45  *
  46  * Please see session.h for more explanation and correct usage of the list.
  47  */
  48 static struct ltt_session_list ltt_session_list = {
  49         .head = CDS_LIST_HEAD_INIT(ltt_session_list.head),
  50         .lock = PTHREAD_MUTEX_INITIALIZER,
  51         .count = 0,
  52 };
  53
  54 /*
  55  * Add a ltt_session structure to the global list.
  56  *
  57  * The caller MUST acquire the session list lock before.
  58  * Returns the unique identifier for the session.
  59  */
  60 static int add_session_list(struct ltt_session *ls)
  61 {
  62         cds_list_add(&ls->list, &ltt_session_list.head);
  63         return ++ltt_session_list.count;
  64 }
  65
  66 /*
  67  * Delete a ltt_session structure to the global list.
  68  *
  69  * The caller MUST acquire the session list lock before.
  70  */
  71 static void del_session_list(struct ltt_session *ls)
  72 {
  73         cds_list_del(&ls->list);
  74         /* Sanity check */
  75         if (ltt_session_list.count > 0) {
  76                 ltt_session_list.count--;
  77         }
  78 }
  79
  80 /*
  81  * Return a pointer to the session list.
  82  */
  83 struct ltt_session_list *session_get_list(void)
  84 {
  85         return &ltt_session_list;
  86 }
  87
  88 /*
  89  * Acquire session list lock
  90  */
  91 void session_lock_list(void)
  92 {
  93         pthread_mutex_lock(&ltt_session_list.lock);
  94 }
  95
  96 /*
  97  * Release session list lock
  98  */
  99 void session_unlock_list(void)
 100 {
 101         pthread_mutex_unlock(&ltt_session_list.lock);
 102 }
 103
 104 /*
 105  * Acquire session lock
 106  */
 107 void session_lock(struct ltt_session *session)
 108 {
 109         pthread_mutex_lock(&session->lock);
 110 }
 111
 112 /*
 113  * Release session lock
 114  */
 115 void session_unlock(struct ltt_session *session)
 116 {
 117         pthread_mutex_unlock(&session->lock);
 118 }
 119
 120 /*
 121  * Return a ltt_session structure ptr that matches name. If no session found,
 122  * NULL is returned. This must be called with the session lock held using
 123  * session_lock_list and session_unlock_list.
 124  */
 125 struct ltt_session *session_find_by_name(char *name)
 126 {
 127         struct ltt_session *iter;
 128
 129         DBG2("Trying to find session by name %s", name);
 130
 131         cds_list_for_each_entry(iter, &ltt_session_list.head, list) {
 132                 if (strncmp(iter->name, name, NAME_MAX) == 0) {
 133                         goto found;
 134                 }
 135         }
 136
 137         iter = NULL;
 138
 139 found:
 140         return iter;
 141 }
 142
 143 /*
 144  * Delete session from the session list and free the memory.
 145  *
 146  * Return -1 if no session is found.  On success, return 1;
 147  */
 148 int session_destroy(struct ltt_session *session)
 149 {
 150         /* Safety check */
 151         if (session == NULL) {
 152                 ERR("Session pointer was null on session destroy");
 153                 return LTTCOMM_OK;
 154         }
 155
 156         DBG("Destroying session %s", session->name);
 157         del_session_list(session);
 158         pthread_mutex_destroy(&session->lock);
 159         free(session);
 160
 161         return LTTCOMM_OK;
 162 }
 163
 164 /*
 165  * Create a brand new session and add it to the session list.
 166  */
 167 int session_create(char *name, char *path)
 168 {
 169         int ret;
 170         struct ltt_session *new_session;
 171
 172         new_session = session_find_by_name(name);
 173         if (new_session != NULL) {
 174                 ret = LTTCOMM_EXIST_SESS;
 175                 goto error_exist;
 176         }
 177
 178         /* Allocate session data structure */
 179         new_session = zmalloc(sizeof(struct ltt_session));
 180         if (new_session == NULL) {
 181                 perror("zmalloc");
 182                 ret = LTTCOMM_FATAL;
 183                 goto error_malloc;
 184         }
 185
 186         /* Define session name */
 187         if (name != NULL) {
 188                 if (snprintf(new_session->name, NAME_MAX, "%s", name) < 0) {
 189                         ret = LTTCOMM_FATAL;
 190                         goto error_asprintf;
 191                 }
 192         } else {
 193                 ERR("No session name given");
 194                 ret = LTTCOMM_FATAL;
 195                 goto error;
 196         }
 197
 198         /* Define session system path */
 199         if (path != NULL) {
 200                 if (snprintf(new_session->path, PATH_MAX, "%s", path) < 0) {
 201                         ret = LTTCOMM_FATAL;
 202                         goto error_asprintf;
 203                 }
 204         } else {
 205                 ERR("No session path given");
 206                 ret = LTTCOMM_FATAL;
 207                 goto error;
 208         }
 209
 210         /* Init kernel session */
 211         new_session->kernel_session = NULL;
 212         new_session->ust_session = NULL;
 213
 214         /* Init lock */
 215         pthread_mutex_init(&new_session->lock, NULL);
 216
 217         /* Add new session to the session list */
 218         session_lock_list();
 219         new_session->uid = add_session_list(new_session);
 220         session_unlock_list();
 221
 222         DBG("Tracing session %s created in %s with UID %d", name, path, new_session->uid);
 223
 224         return LTTCOMM_OK;
 225
 226 error:
 227 error_asprintf:
 228         if (new_session != NULL) {
 229                 free(new_session);
 230         }
 231
 232 error_exist:
 233 error_malloc:
 234         return ret;
 235 }