src/bin/lttng-sessiond/session.c

   1 /*
   2  * Copyright (C) 2011 David Goulet <david.goulet@polymtl.ca>
   3  *
   4  * SPDX-License-Identifier: GPL-2.0-only
   5  *
   6  */
   7
   8 #define _LGPL_SOURCE
   9 #include <limits.h>
  10 #include <inttypes.h>
  11 #include <stdio.h>
  12 #include <stdlib.h>
  13 #include <string.h>
  14 #include <sys/stat.h>
  15 #include <urcu.h>
  16 #include <dirent.h>
  17 #include <sys/types.h>
  18 #include <pthread.h>
  19
  20 #include <common/common.h>
  21 #include <common/utils.h>
  22 #include <common/trace-chunk.h>
  23 #include <common/sessiond-comm/sessiond-comm.h>
  24 #include <lttng/location-internal.h>
  25 #include "lttng-sessiond.h"
  26 #include "kernel.h"
  27
  28 #include "session.h"
  29 #include "utils.h"
  30 #include "trace-ust.h"
  31 #include "timer.h"
  32 #include "cmd.h"
  33
  34 struct ltt_session_destroy_notifier_element {
  35         ltt_session_destroy_notifier notifier;
  36         void *user_data;
  37 };
  38
  39 struct ltt_session_clear_notifier_element {
  40         ltt_session_clear_notifier notifier;
  41         void *user_data;
  42 };
  43
  44 /*
  45  * NOTES:
  46  *
  47  * No ltt_session.lock is taken here because those data structure are widely
  48  * spread across the lttng-tools code base so before calling functions below
  49  * that can read/write a session, the caller MUST acquire the session lock
  50  * using session_lock() and session_unlock().
  51  */
  52
  53 /*
  54  * Init tracing session list.
  55  *
  56  * Please see session.h for more explanation and correct usage of the list.
  57  */
  58 static struct ltt_session_list ltt_session_list = {
  59         .head = CDS_LIST_HEAD_INIT(ltt_session_list.head),
  60         .lock = PTHREAD_MUTEX_INITIALIZER,
  61         .removal_cond = PTHREAD_COND_INITIALIZER,
  62         .next_uuid = 0,
  63 };
  64
  65 /* These characters are forbidden in a session name. Used by validate_name. */
  66 static const char *forbidden_name_chars = "/";
  67
  68 /* Global hash table to keep the sessions, indexed by id. */
  69 static struct lttng_ht *ltt_sessions_ht_by_id = NULL;
  70 /* Global hash table to keep the sessions, indexed by name. */
  71 static struct lttng_ht *ltt_sessions_ht_by_name = NULL;
  72
  73 /*
  74  * Validate the session name for forbidden characters.
  75  *
  76  * Return 0 on success else -1 meaning a forbidden char. has been found.
  77  */
  78 static int validate_name(const char *name)
  79 {
  80         int ret;
  81         char *tok, *tmp_name;
  82
  83         assert(name);
  84
  85         tmp_name = strdup(name);
  86         if (!tmp_name) {
  87                 /* ENOMEM here. */
  88                 ret = -1;
  89                 goto error;
  90         }
  91
  92         tok = strpbrk(tmp_name, forbidden_name_chars);
  93         if (tok) {
  94                 DBG("Session name %s contains a forbidden character", name);
  95                 /* Forbidden character has been found. */
  96                 ret = -1;
  97                 goto error;
  98         }
  99         ret = 0;
 100
 101 error:
 102         free(tmp_name);
 103         return ret;
 104 }
 105
 106 /*
 107  * Add a ltt_session structure to the global list.
 108  *
 109  * The caller MUST acquire the session list lock before.
 110  * Returns the unique identifier for the session.
 111  */
 112 static uint64_t add_session_list(struct ltt_session *ls)
 113 {
 114         assert(ls);
 115
 116         cds_list_add(&ls->list, &ltt_session_list.head);
 117         return ltt_session_list.next_uuid++;
 118 }
 119
 120 /*
 121  * Delete a ltt_session structure to the global list.
 122  *
 123  * The caller MUST acquire the session list lock before.
 124  */
 125 static void del_session_list(struct ltt_session *ls)
 126 {
 127         assert(ls);
 128
 129         cds_list_del(&ls->list);
 130 }
 131
 132 /*
 133  * Return a pointer to the session list.
 134  */
 135 struct ltt_session_list *session_get_list(void)
 136 {
 137         return &ltt_session_list;
 138 }
 139
 140 /*
 141  * Returns once the session list is empty.
 142  */
 143 void session_list_wait_empty(void)
 144 {
 145         pthread_mutex_lock(&ltt_session_list.lock);
 146         while (!cds_list_empty(&ltt_session_list.head)) {
 147                 pthread_cond_wait(&ltt_session_list.removal_cond,
 148                                 &ltt_session_list.lock);
 149         }
 150         pthread_mutex_unlock(&ltt_session_list.lock);
 151 }
 152
 153 /*
 154  * Acquire session list lock
 155  */
 156 void session_lock_list(void)
 157 {
 158         pthread_mutex_lock(&ltt_session_list.lock);
 159 }
 160
 161 /*
 162  * Try to acquire session list lock
 163  */
 164 int session_trylock_list(void)
 165 {
 166         return pthread_mutex_trylock(&ltt_session_list.lock);
 167 }
 168
 169 /*
 170  * Release session list lock
 171  */
 172 void session_unlock_list(void)
 173 {
 174         pthread_mutex_unlock(&ltt_session_list.lock);
 175 }
 176
 177 /*
 178  * Get the session's consumer destination type.
 179  *
 180  * The caller must hold the session lock.
 181  */
 182 enum consumer_dst_type session_get_consumer_destination_type(
 183                 const struct ltt_session *session)
 184 {
 185         /*
 186          * The output information is duplicated in both of those session types.
 187          * Hence, it doesn't matter from which it is retrieved. However, it is
 188          * possible for only one of them to be set.
 189          */
 190         return session->kernel_session ?
 191                         session->kernel_session->consumer->type :
 192                         session->ust_session->consumer->type;
 193 }
 194
 195 /*
 196  * Get the session's consumer network hostname.
 197  * The caller must ensure that the destination is of type "net".
 198  *
 199  * The caller must hold the session lock.
 200  */
 201 const char *session_get_net_consumer_hostname(const struct ltt_session *session)
 202 {
 203         const char *hostname = NULL;
 204         const struct consumer_output *output;
 205
 206         output = session->kernel_session ?
 207                         session->kernel_session->consumer :
 208                         session->ust_session->consumer;
 209
 210         /*
 211          * hostname is assumed to be the same for both control and data
 212          * connections.
 213          */
 214         switch (output->dst.net.control.dtype) {
 215         case LTTNG_DST_IPV4:
 216                 hostname = output->dst.net.control.dst.ipv4;
 217                 break;
 218         case LTTNG_DST_IPV6:
 219                 hostname = output->dst.net.control.dst.ipv6;
 220                 break;
 221         default:
 222                 abort();
 223         }
 224         return hostname;
 225 }
 226
 227 /*
 228  * Get the session's consumer network control and data ports.
 229  * The caller must ensure that the destination is of type "net".
 230  *
 231  * The caller must hold the session lock.
 232  */
 233 void session_get_net_consumer_ports(const struct ltt_session *session,
 234                 uint16_t *control_port, uint16_t *data_port)
 235 {
 236         const struct consumer_output *output;
 237
 238         output = session->kernel_session ?
 239                         session->kernel_session->consumer :
 240                         session->ust_session->consumer;
 241         *control_port = output->dst.net.control.port;
 242         *data_port = output->dst.net.data.port;
 243 }
 244
 245 /*
 246  * Get the location of the latest trace archive produced by a rotation.
 247  *
 248  * The caller must hold the session lock.
 249  */
 250 struct lttng_trace_archive_location *session_get_trace_archive_location(
 251                 const struct ltt_session *session)
 252 {
 253         int ret;
 254         struct lttng_trace_archive_location *location = NULL;
 255         char *chunk_path = NULL;
 256
 257         if (session->rotation_state != LTTNG_ROTATION_STATE_COMPLETED ||
 258                         !session->last_archived_chunk_name) {
 259                 goto end;
 260         }
 261
 262         switch (session_get_consumer_destination_type(session)) {
 263         case CONSUMER_DST_LOCAL:
 264                 ret = asprintf(&chunk_path,
 265                                 "%s/" DEFAULT_ARCHIVED_TRACE_CHUNKS_DIRECTORY "/%s",
 266                                 session_get_base_path(session),
 267                                 session->last_archived_chunk_name);
 268                 if (ret == -1) {
 269                         goto end;
 270                 }
 271                 location = lttng_trace_archive_location_local_create(
 272                                 chunk_path);
 273                 break;
 274         case CONSUMER_DST_NET:
 275         {
 276                 const char *hostname;
 277                 uint16_t control_port, data_port;
 278
 279                 hostname = session_get_net_consumer_hostname(session);
 280                 session_get_net_consumer_ports(session,
 281                                 &control_port,
 282                                 &data_port);
 283                 location = lttng_trace_archive_location_relay_create(
 284                                 hostname,
 285                                 LTTNG_TRACE_ARCHIVE_LOCATION_RELAY_PROTOCOL_TYPE_TCP,
 286                                 control_port, data_port, session->last_chunk_path);
 287                 break;
 288         }
 289         default:
 290                 abort();
 291         }
 292 end:
 293         free(chunk_path);
 294         return location;
 295 }
 296
 297 /*
 298  * Allocate the ltt_sessions_ht_by_id and ltt_sessions_ht_by_name HT.
 299  *
 300  * The session list lock must be held.
 301  */
 302 static int ltt_sessions_ht_alloc(void)
 303 {
 304         int ret = 0;
 305
 306         DBG("Allocating ltt_sessions_ht_by_id");
 307         ltt_sessions_ht_by_id = lttng_ht_new(0, LTTNG_HT_TYPE_U64);
 308         if (!ltt_sessions_ht_by_id) {
 309                 ret = -1;
 310                 ERR("Failed to allocate ltt_sessions_ht_by_id");
 311                 goto end;
 312         }
 313
 314         DBG("Allocating ltt_sessions_ht_by_name");
 315         ltt_sessions_ht_by_name = lttng_ht_new(0, LTTNG_HT_TYPE_STRING);
 316         if (!ltt_sessions_ht_by_name) {
 317                 ret = -1;
 318                 ERR("Failed to allocate ltt_sessions_ht_by_name");
 319                 goto end;
 320         }
 321
 322 end:
 323         return ret;
 324 }
 325
 326 /*
 327  * Destroy the ltt_sessions_ht_by_id HT.
 328  *
 329  * The session list lock must be held.
 330  */
 331 static void ltt_sessions_ht_destroy(void)
 332 {
 333         if (ltt_sessions_ht_by_id) {
 334                 ht_cleanup_push(ltt_sessions_ht_by_id);
 335                 ltt_sessions_ht_by_id = NULL;
 336         }
 337
 338         if (ltt_sessions_ht_by_name) {
 339                 ht_cleanup_push(ltt_sessions_ht_by_name);
 340                 ltt_sessions_ht_by_name = NULL;
 341         }
 342
 343         return;
 344 }
 345
 346 /*
 347  * Add a ltt_session to the ltt_sessions_ht_by_id and ltt_sessions_ht_by_name.
 348  * If unallocated, the ltt_sessions_ht_by_id and ltt_sessions_ht_by_name. HTs
 349  * are allocated. The session list lock must be held.
 350  */
 351 static void add_session_ht(struct ltt_session *ls)
 352 {
 353         int ret;
 354
 355         assert(ls);
 356
 357         if (!ltt_sessions_ht_by_id) {
 358                 ret = ltt_sessions_ht_alloc();
 359                 if (ret) {
 360                         ERR("Error allocating the sessions HT");
 361                         goto end;
 362                 }
 363         }
 364
 365         /* Should always be present with ltt_sessions_ht_by_id. */
 366         assert(ltt_sessions_ht_by_name);
 367
 368         lttng_ht_node_init_u64(&ls->node, ls->id);
 369         lttng_ht_add_unique_u64(ltt_sessions_ht_by_id, &ls->node);
 370
 371         lttng_ht_node_init_str(&ls->node_by_name, ls->name);
 372         lttng_ht_add_unique_str(ltt_sessions_ht_by_name, &ls->node_by_name);
 373
 374 end:
 375         return;
 376 }
 377
 378 /*
 379  * Test if ltt_sessions_ht_by_id/name are empty.
 380  * Return 1 if empty, 0 if not empty.
 381  * The session list lock must be held.
 382  */
 383 static int ltt_sessions_ht_empty(void)
 384 {
 385         unsigned long count;
 386
 387         if (!ltt_sessions_ht_by_id) {
 388                 count = 0;
 389                 goto end;
 390         }
 391
 392         assert(ltt_sessions_ht_by_name);
 393
 394         count = lttng_ht_get_count(ltt_sessions_ht_by_id);
 395         assert(count == lttng_ht_get_count(ltt_sessions_ht_by_name));
 396 end:
 397         return count ? 0 : 1;
 398 }
 399
 400 /*
 401  * Remove a ltt_session from the ltt_sessions_ht_by_id/name.
 402  * If empty, the ltt_sessions_ht_by_id/name HTs are freed.
 403  * The session list lock must be held.
 404  */
 405 static void del_session_ht(struct ltt_session *ls)
 406 {
 407         struct lttng_ht_iter iter;
 408         int ret;
 409
 410         assert(ls);
 411         assert(ltt_sessions_ht_by_id);
 412         assert(ltt_sessions_ht_by_name);
 413
 414         iter.iter.node = &ls->node.node;
 415         ret = lttng_ht_del(ltt_sessions_ht_by_id, &iter);
 416         assert(!ret);
 417
 418         iter.iter.node = &ls->node_by_name.node;
 419         ret = lttng_ht_del(ltt_sessions_ht_by_name, &iter);
 420         assert(!ret);
 421
 422         if (ltt_sessions_ht_empty()) {
 423                 DBG("Empty ltt_sessions_ht_by_id/name, destroying hast tables");
 424                 ltt_sessions_ht_destroy();
 425         }
 426 }
 427
 428 /*
 429  * Acquire session lock
 430  */
 431 void session_lock(struct ltt_session *session)
 432 {
 433         assert(session);
 434
 435         pthread_mutex_lock(&session->lock);
 436 }
 437
 438 /*
 439  * Release session lock
 440  */
 441 void session_unlock(struct ltt_session *session)
 442 {
 443         assert(session);
 444
 445         pthread_mutex_unlock(&session->lock);
 446 }
 447
 448 static
 449 int _session_set_trace_chunk_no_lock_check(struct ltt_session *session,
 450                 struct lttng_trace_chunk *new_trace_chunk,
 451                 struct lttng_trace_chunk **_current_trace_chunk)
 452 {
 453         int ret = 0;
 454         unsigned int i, refs_to_acquire = 0, refs_acquired = 0, refs_to_release = 0;
 455         struct cds_lfht_iter iter;
 456         struct consumer_socket *socket;
 457         struct lttng_trace_chunk *current_trace_chunk;
 458         uint64_t chunk_id;
 459         enum lttng_trace_chunk_status chunk_status;
 460
 461         rcu_read_lock();
 462         /*
 463          * Ownership of current trace chunk is transferred to
 464          * `current_trace_chunk`.
 465          */
 466         current_trace_chunk = session->current_trace_chunk;
 467         session->current_trace_chunk = NULL;
 468         if (session->ust_session) {
 469                 lttng_trace_chunk_put(
 470                                 session->ust_session->current_trace_chunk);
 471                 session->ust_session->current_trace_chunk = NULL;
 472         }
 473         if (session->kernel_session) {
 474                 lttng_trace_chunk_put(
 475                                 session->kernel_session->current_trace_chunk);
 476                 session->kernel_session->current_trace_chunk = NULL;
 477         }
 478         if (!new_trace_chunk) {
 479                 ret = 0;
 480                 goto end;
 481         }
 482         chunk_status = lttng_trace_chunk_get_id(new_trace_chunk, &chunk_id);
 483         assert(chunk_status == LTTNG_TRACE_CHUNK_STATUS_OK);
 484
 485         refs_to_acquire = 1;
 486         refs_to_acquire += !!session->ust_session;
 487         refs_to_acquire += !!session->kernel_session;
 488
 489         for (refs_acquired = 0; refs_acquired < refs_to_acquire;
 490                         refs_acquired++) {
 491                 if (!lttng_trace_chunk_get(new_trace_chunk)) {
 492                         ERR("Failed to acquire reference to new trace chunk of session \"%s\"",
 493                                         session->name);
 494                         goto error;
 495                 }
 496         }
 497
 498         if (session->ust_session) {
 499                 const uint64_t relayd_id =
 500                                 session->ust_session->consumer->net_seq_index;
 501                 const bool is_local_trace =
 502                                 session->ust_session->consumer->type ==
 503                                 CONSUMER_DST_LOCAL;
 504
 505                 session->ust_session->current_trace_chunk = new_trace_chunk;
 506                 if (is_local_trace) {
 507                         enum lttng_error_code ret_error_code;
 508
 509                         ret_error_code = ust_app_create_channel_subdirectories(
 510                                         session->ust_session);
 511                         if (ret_error_code != LTTNG_OK) {
 512                                 goto error;
 513                         }
 514                 }
 515                 cds_lfht_for_each_entry(
 516                                 session->ust_session->consumer->socks->ht,
 517                                 &iter, socket, node.node) {
 518                         pthread_mutex_lock(socket->lock);
 519                         ret = consumer_create_trace_chunk(socket,
 520                                         relayd_id,
 521                                         session->id, new_trace_chunk,
 522                                         DEFAULT_UST_TRACE_DIR);
 523                         pthread_mutex_unlock(socket->lock);
 524                         if (ret) {
 525                                 goto error;
 526                         }
 527                 }
 528         }
 529         if (session->kernel_session) {
 530                 const uint64_t relayd_id =
 531                                 session->kernel_session->consumer->net_seq_index;
 532                 const bool is_local_trace =
 533                                 session->kernel_session->consumer->type ==
 534                                 CONSUMER_DST_LOCAL;
 535
 536                 session->kernel_session->current_trace_chunk = new_trace_chunk;
 537                 if (is_local_trace) {
 538                         enum lttng_error_code ret_error_code;
 539
 540                         ret_error_code = kernel_create_channel_subdirectories(
 541                                         session->kernel_session);
 542                         if (ret_error_code != LTTNG_OK) {
 543                                 goto error;
 544                         }
 545                 }
 546                 cds_lfht_for_each_entry(
 547                                 session->kernel_session->consumer->socks->ht,
 548                                 &iter, socket, node.node) {
 549                         pthread_mutex_lock(socket->lock);
 550                         ret = consumer_create_trace_chunk(socket,
 551                                         relayd_id,
 552                                         session->id, new_trace_chunk,
 553                                         DEFAULT_KERNEL_TRACE_DIR);
 554                         pthread_mutex_unlock(socket->lock);
 555                         if (ret) {
 556                                 goto error;
 557                         }
 558                 }
 559         }
 560
 561         /*
 562          * Update local current trace chunk state last, only if all remote
 563          * creations succeeded.
 564          */
 565         session->current_trace_chunk = new_trace_chunk;
 566         LTTNG_OPTIONAL_SET(&session->most_recent_chunk_id, chunk_id);
 567 end:
 568         if (_current_trace_chunk) {
 569                 *_current_trace_chunk = current_trace_chunk;
 570                 current_trace_chunk = NULL;
 571         }
 572 end_no_move:
 573         rcu_read_unlock();
 574         lttng_trace_chunk_put(current_trace_chunk);
 575         return ret;
 576 error:
 577         if (session->ust_session) {
 578                 session->ust_session->current_trace_chunk = NULL;
 579         }
 580         if (session->kernel_session) {
 581                 session->kernel_session->current_trace_chunk = NULL;
 582         }
 583         /*
 584          * Release references taken in the case where all references could not
 585          * be acquired.
 586          */
 587         refs_to_release = refs_to_acquire - refs_acquired;
 588         for (i = 0; i < refs_to_release; i++) {
 589                 lttng_trace_chunk_put(new_trace_chunk);
 590         }
 591         ret = -1;
 592         goto end_no_move;
 593 }
 594
 595 struct lttng_trace_chunk *session_create_new_trace_chunk(
 596                 const struct ltt_session *session,
 597                 const struct consumer_output *consumer_output_override,
 598                 const char *session_base_path_override,
 599                 const char *chunk_name_override)
 600 {
 601         int ret;
 602         struct lttng_trace_chunk *trace_chunk = NULL;
 603         enum lttng_trace_chunk_status chunk_status;
 604         const time_t chunk_creation_ts = time(NULL);
 605         bool is_local_trace;
 606         const char *base_path;
 607         struct lttng_directory_handle *session_output_directory = NULL;
 608         const struct lttng_credentials session_credentials = {
 609                 .uid = LTTNG_OPTIONAL_INIT_VALUE(session->uid),
 610                 .gid = LTTNG_OPTIONAL_INIT_VALUE(session->gid),
 611         };
 612         uint64_t next_chunk_id;
 613         const struct consumer_output *output;
 614         const char *new_path;
 615
 616         if (consumer_output_override) {
 617                 output = consumer_output_override;
 618         } else {
 619                 assert(session->ust_session || session->kernel_session);
 620                 output = session->ust_session ?
 621                                          session->ust_session->consumer :
 622                                          session->kernel_session->consumer;
 623         }
 624
 625         is_local_trace = output->type == CONSUMER_DST_LOCAL;
 626         base_path = session_base_path_override ? :
 627                         consumer_output_get_base_path(output);
 628
 629         if (chunk_creation_ts == (time_t) -1) {
 630                 PERROR("Failed to sample time while creation session \"%s\" trace chunk",
 631                                 session->name);
 632                 goto error;
 633         }
 634
 635         next_chunk_id = session->most_recent_chunk_id.is_set ?
 636                         session->most_recent_chunk_id.value + 1 : 0;
 637
 638         if (session->current_trace_chunk &&
 639                         !lttng_trace_chunk_get_name_overridden(session->current_trace_chunk)) {
 640                 chunk_status = lttng_trace_chunk_rename_path(session->current_trace_chunk,
 641                                         DEFAULT_CHUNK_TMP_OLD_DIRECTORY);
 642                 if (chunk_status != LTTNG_TRACE_CHUNK_STATUS_OK) {
 643                         goto error;
 644                 }
 645         }
 646         if (!session->current_trace_chunk) {
 647                 if (!session->rotated) {
 648                         new_path = "";
 649                 } else {
 650                         new_path = NULL;
 651                 }
 652         } else {
 653                 new_path = DEFAULT_CHUNK_TMP_NEW_DIRECTORY;
 654         }
 655
 656         trace_chunk = lttng_trace_chunk_create(next_chunk_id,
 657                         chunk_creation_ts, new_path);
 658         if (!trace_chunk) {
 659                 goto error;
 660         }
 661
 662         if (chunk_name_override) {
 663                 chunk_status = lttng_trace_chunk_override_name(trace_chunk,
 664                                 chunk_name_override);
 665                 if (chunk_status != LTTNG_TRACE_CHUNK_STATUS_OK) {
 666                         goto error;
 667                 }
 668         }
 669
 670         if (!is_local_trace) {
 671                 /*
 672                  * No need to set crendentials and output directory
 673                  * for remote trace chunks.
 674                  */
 675                 goto end;
 676         }
 677
 678         chunk_status = lttng_trace_chunk_set_credentials(trace_chunk,
 679                         &session_credentials);
 680         if (chunk_status != LTTNG_TRACE_CHUNK_STATUS_OK) {
 681                 goto error;
 682         }
 683
 684         DBG("Creating base output directory of session \"%s\" at %s",
 685                         session->name, base_path);
 686         ret = utils_mkdir_recursive(base_path, S_IRWXU | S_IRWXG,
 687                         session->uid, session->gid);
 688         if (ret) {
 689                 goto error;
 690         }
 691         session_output_directory = lttng_directory_handle_create(base_path);
 692         if (!session_output_directory) {
 693                 goto error;
 694         }
 695         chunk_status = lttng_trace_chunk_set_as_owner(trace_chunk,
 696                         session_output_directory);
 697         lttng_directory_handle_put(session_output_directory);
 698         session_output_directory = NULL;
 699         if (chunk_status != LTTNG_TRACE_CHUNK_STATUS_OK) {
 700                 goto error;
 701         }
 702 end:
 703         return trace_chunk;
 704 error:
 705         lttng_directory_handle_put(session_output_directory);
 706         lttng_trace_chunk_put(trace_chunk);
 707         trace_chunk = NULL;
 708         goto end;
 709 }
 710
 711 int session_close_trace_chunk(struct ltt_session *session,
 712                 struct lttng_trace_chunk *trace_chunk,
 713                 enum lttng_trace_chunk_command_type close_command,
 714                 char *closed_trace_chunk_path)
 715 {
 716         int ret = 0;
 717         bool error_occurred = false;
 718         struct cds_lfht_iter iter;
 719         struct consumer_socket *socket;
 720         enum lttng_trace_chunk_status chunk_status;
 721         const time_t chunk_close_timestamp = time(NULL);
 722         const char *new_path;
 723
 724         chunk_status = lttng_trace_chunk_set_close_command(
 725                         trace_chunk, close_command);
 726         if (chunk_status != LTTNG_TRACE_CHUNK_STATUS_OK) {
 727                 ret = -1;
 728                 goto end;
 729         }
 730
 731         if (chunk_close_timestamp == (time_t) -1) {
 732                 ERR("Failed to sample the close timestamp of the current trace chunk of session \"%s\"",
 733                                 session->name);
 734                 ret = -1;
 735                 goto end;
 736         }
 737
 738         if (close_command == LTTNG_TRACE_CHUNK_COMMAND_TYPE_DELETE && !session->rotated) {
 739                 /* New chunk stays in session output directory. */
 740                 new_path = "";
 741         } else {
 742                 /* Use chunk name for new chunk. */
 743                 new_path = NULL;
 744         }
 745         if (session->current_trace_chunk &&
 746                         !lttng_trace_chunk_get_name_overridden(session->current_trace_chunk)) {
 747                 /* Rename new chunk path. */
 748                 chunk_status = lttng_trace_chunk_rename_path(session->current_trace_chunk,
 749                                         new_path);
 750                 if (chunk_status != LTTNG_TRACE_CHUNK_STATUS_OK) {
 751                         ret = -1;
 752                         goto end;
 753                 }
 754         }
 755         if (!lttng_trace_chunk_get_name_overridden(trace_chunk) &&
 756                         close_command == LTTNG_TRACE_CHUNK_COMMAND_TYPE_NO_OPERATION) {
 757                 const char *old_path;
 758
 759                 if (!session->rotated) {
 760                         old_path = "";
 761                 } else {
 762                         old_path = NULL;
 763                 }
 764                 /* We need to move back the .tmp_old_chunk to its rightful place. */
 765                 chunk_status = lttng_trace_chunk_rename_path(trace_chunk,
 766                                         old_path);
 767                 if (chunk_status != LTTNG_TRACE_CHUNK_STATUS_OK) {
 768                         ret = -1;
 769                         goto end;
 770                 }
 771         }
 772         if (close_command == LTTNG_TRACE_CHUNK_COMMAND_TYPE_MOVE_TO_COMPLETED) {
 773                 session->rotated = true;
 774         }
 775         chunk_status = lttng_trace_chunk_set_close_timestamp(trace_chunk,
 776                         chunk_close_timestamp);
 777         if (chunk_status != LTTNG_TRACE_CHUNK_STATUS_OK) {
 778                 ERR("Failed to set the close timestamp of the current trace chunk of session \"%s\"",
 779                                 session->name);
 780                 ret = -1;
 781                 goto end;
 782         }
 783
 784         if (session->ust_session) {
 785                 const uint64_t relayd_id =
 786                                 session->ust_session->consumer->net_seq_index;
 787
 788                 cds_lfht_for_each_entry(
 789                                 session->ust_session->consumer->socks->ht,
 790                                 &iter, socket, node.node) {
 791                         pthread_mutex_lock(socket->lock);
 792                         ret = consumer_close_trace_chunk(socket,
 793                                         relayd_id,
 794                                         session->id,
 795                                         trace_chunk, closed_trace_chunk_path);
 796                         pthread_mutex_unlock(socket->lock);
 797                         if (ret) {
 798                                 ERR("Failed to close trace chunk on user space consumer");
 799                                 error_occurred = true;
 800                         }
 801                 }
 802         }
 803         if (session->kernel_session) {
 804                 const uint64_t relayd_id =
 805                                 session->kernel_session->consumer->net_seq_index;
 806
 807                 cds_lfht_for_each_entry(
 808                                 session->kernel_session->consumer->socks->ht,
 809                                 &iter, socket, node.node) {
 810                         pthread_mutex_lock(socket->lock);
 811                         ret = consumer_close_trace_chunk(socket,
 812                                         relayd_id,
 813                                         session->id,
 814                                         trace_chunk, closed_trace_chunk_path);
 815                         pthread_mutex_unlock(socket->lock);
 816                         if (ret) {
 817                                 ERR("Failed to close trace chunk on kernel consumer");
 818                                 error_occurred = true;
 819                         }
 820                 }
 821         }
 822         ret = error_occurred ? -1 : 0;
 823 end:
 824         return ret;
 825 }
 826
 827 /*
 828  * This function skips the metadata channel as the begin/end timestamps of a
 829  * metadata packet are useless.
 830  *
 831  * Moreover, opening a packet after a "clear" will cause problems for live
 832  * sessions as it will introduce padding that was not part of the first trace
 833  * chunk. The relay daemon expects the content of the metadata stream of
 834  * successive metadata trace chunks to be strict supersets of one another.
 835  *
 836  * For example, flushing a packet at the beginning of the metadata stream of
 837  * a trace chunk resulting from a "clear" session command will cause the
 838  * size of the metadata stream of the new trace chunk to not match the size of
 839  * the metadata stream of the original chunk. This will confuse the relay
 840  * daemon as the same "offset" in a metadata stream will no longer point
 841  * to the same content.
 842  */
 843 static
 844 enum lttng_error_code session_kernel_open_packets(struct ltt_session *session)
 845 {
 846         enum lttng_error_code ret = LTTNG_OK;
 847         struct consumer_socket *socket;
 848         struct lttng_ht_iter iter;
 849         struct cds_lfht_node *node;
 850         struct ltt_kernel_channel *chan;
 851
 852         rcu_read_lock();
 853
 854         cds_lfht_first(session->kernel_session->consumer->socks->ht, &iter.iter);
 855         node = cds_lfht_iter_get_node(&iter.iter);
 856         socket = container_of(node, typeof(*socket), node.node);
 857
 858         cds_list_for_each_entry(chan,
 859                         &session->kernel_session->channel_list.head, list) {
 860                 int open_ret;
 861
 862                 DBG("Open packet of kernel channel: channel key = %" PRIu64
 863                                 ", session name = %s, session_id = %" PRIu64,
 864                                 chan->key, session->name, session->id);
 865
 866                 open_ret = consumer_open_channel_packets(socket, chan->key);
 867                 if (open_ret < 0) {
 868                         /* General error (no known error expected). */
 869                         ret = LTTNG_ERR_UNK;
 870                         goto end;
 871                 }
 872         }
 873
 874 end:
 875         rcu_read_unlock();
 876         return ret;
 877 }
 878
 879 enum lttng_error_code session_open_packets(struct ltt_session *session)
 880 {
 881         enum lttng_error_code ret = LTTNG_OK;
 882
 883         DBG("Opening packets of session channels: session name = %s, session id = %" PRIu64,
 884                         session->name, session->id);
 885
 886         if (session->ust_session) {
 887                 ret = ust_app_open_packets(session);
 888                 if (ret != LTTNG_OK) {
 889                         goto end;
 890                 }
 891         }
 892
 893         if (session->kernel_session) {
 894                 ret = session_kernel_open_packets(session);
 895                 if (ret != LTTNG_OK) {
 896                         goto end;
 897                 }
 898         }
 899
 900 end:
 901         return ret;
 902 }
 903
 904 /*
 905  * Set a session's current trace chunk.
 906  *
 907  * Must be called with the session lock held.
 908  */
 909 int session_set_trace_chunk(struct ltt_session *session,
 910                 struct lttng_trace_chunk *new_trace_chunk,
 911                 struct lttng_trace_chunk **current_trace_chunk)
 912 {
 913         ASSERT_LOCKED(session->lock);
 914         return _session_set_trace_chunk_no_lock_check(session, new_trace_chunk,
 915                         current_trace_chunk);
 916 }
 917
 918 static
 919 void session_notify_destruction(const struct ltt_session *session)
 920 {
 921         size_t i;
 922         const size_t count = lttng_dynamic_array_get_count(
 923                         &session->destroy_notifiers);
 924
 925         for (i = 0; i < count; i++) {
 926                 const struct ltt_session_destroy_notifier_element *element =
 927                         lttng_dynamic_array_get_element(
 928                                         &session->destroy_notifiers, i);
 929
 930                 element->notifier(session, element->user_data);
 931         }
 932 }
 933
 934 /*
 935  * Fire each clear notifier once, and remove them from the array.
 936  */
 937 void session_notify_clear(struct ltt_session *session)
 938 {
 939         size_t i;
 940         const size_t count = lttng_dynamic_array_get_count(
 941                         &session->clear_notifiers);
 942
 943         for (i = 0; i < count; i++) {
 944                 const struct ltt_session_clear_notifier_element *element =
 945                         lttng_dynamic_array_get_element(
 946                                         &session->clear_notifiers, i);
 947
 948                 element->notifier(session, element->user_data);
 949         }
 950         lttng_dynamic_array_clear(&session->clear_notifiers);
 951 }
 952
 953 static
 954 void session_release(struct urcu_ref *ref)
 955 {
 956         int ret;
 957         struct ltt_ust_session *usess;
 958         struct ltt_kernel_session *ksess;
 959         struct ltt_session *session = container_of(ref, typeof(*session), ref);
 960         const bool session_published = session->published;
 961
 962         assert(!session->chunk_being_archived);
 963
 964         usess = session->ust_session;
 965         ksess = session->kernel_session;
 966
 967         /* Clean kernel session teardown, keeping data for destroy notifier. */
 968         kernel_destroy_session(ksess);
 969
 970         /* UST session teardown, keeping data for destroy notifier. */
 971         if (usess) {
 972                 /* Close any relayd session */
 973                 consumer_output_send_destroy_relayd(usess->consumer);
 974
 975                 /* Destroy every UST application related to this session. */
 976                 ret = ust_app_destroy_trace_all(usess);
 977                 if (ret) {
 978                         ERR("Error in ust_app_destroy_trace_all");
 979                 }
 980
 981                 /* Clean up the rest, keeping destroy notifier data. */
 982                 trace_ust_destroy_session(usess);
 983         }
 984
 985         /*
 986          * Must notify the kernel thread here to update it's poll set in order to
 987          * remove the channel(s)' fd just destroyed.
 988          */
 989         ret = notify_thread_pipe(the_kernel_poll_pipe[1]);
 990         if (ret < 0) {
 991                 PERROR("write kernel poll pipe");
 992         }
 993
 994         DBG("Destroying session %s (id %" PRIu64 ")", session->name, session->id);
 995
 996         snapshot_destroy(&session->snapshot);
 997
 998         pthread_mutex_destroy(&session->lock);
 999
1000         if (session_published) {
1001                 ASSERT_LOCKED(ltt_session_list.lock);
1002                 del_session_list(session);
1003                 del_session_ht(session);
1004         }
1005         session_notify_destruction(session);
1006
1007         consumer_output_put(session->consumer);
1008         kernel_free_session(ksess);
1009         session->kernel_session = NULL;
1010         if (usess) {
1011                 trace_ust_free_session(usess);
1012                 session->ust_session = NULL;
1013         }
1014         lttng_dynamic_array_reset(&session->destroy_notifiers);
1015         lttng_dynamic_array_reset(&session->clear_notifiers);
1016         free(session->last_archived_chunk_name);
1017         free(session->base_path);
1018         free(session);
1019         if (session_published) {
1020                 /*
1021                  * Broadcast after free-ing to ensure the memory is
1022                  * reclaimed before the main thread exits.
1023                  */
1024                 ASSERT_LOCKED(ltt_session_list.lock);
1025                 pthread_cond_broadcast(&ltt_session_list.removal_cond);
1026         }
1027 }
1028
1029 /*
1030  * Acquire a reference to a session.
1031  * This function may fail (return false); its return value must be checked.
1032  */
1033 bool session_get(struct ltt_session *session)
1034 {
1035         return urcu_ref_get_unless_zero(&session->ref);
1036 }
1037
1038 /*
1039  * Release a reference to a session.
1040  */
1041 void session_put(struct ltt_session *session)
1042 {
1043         if (!session) {
1044                 return;
1045         }
1046         /*
1047          * The session list lock must be held as any session_put()
1048          * may cause the removal of the session from the session_list.
1049          */
1050         ASSERT_LOCKED(ltt_session_list.lock);
1051         assert(session->ref.refcount);
1052         urcu_ref_put(&session->ref, session_release);
1053 }
1054
1055 /*
1056  * Destroy a session.
1057  *
1058  * This method does not immediately release/free the session as other
1059  * components may still hold a reference to the session. However,
1060  * the session should no longer be presented to the user.
1061  *
1062  * Releases the session list's reference to the session
1063  * and marks it as destroyed. Iterations on the session list should be
1064  * mindful of the "destroyed" flag.
1065  */
1066 void session_destroy(struct ltt_session *session)
1067 {
1068         assert(!session->destroyed);
1069         session->destroyed = true;
1070         session_put(session);
1071 }
1072
1073 int session_add_destroy_notifier(struct ltt_session *session,
1074                 ltt_session_destroy_notifier notifier, void *user_data)
1075 {
1076         const struct ltt_session_destroy_notifier_element element = {
1077                 .notifier = notifier,
1078                 .user_data = user_data
1079         };
1080
1081         return lttng_dynamic_array_add_element(&session->destroy_notifiers,
1082                         &element);
1083 }
1084
1085 int session_add_clear_notifier(struct ltt_session *session,
1086                 ltt_session_clear_notifier notifier, void *user_data)
1087 {
1088         const struct ltt_session_clear_notifier_element element = {
1089                 .notifier = notifier,
1090                 .user_data = user_data
1091         };
1092
1093         return lttng_dynamic_array_add_element(&session->clear_notifiers,
1094                         &element);
1095 }
1096
1097 /*
1098  * Return a ltt_session structure ptr that matches name. If no session found,
1099  * NULL is returned. This must be called with the session list lock held using
1100  * session_lock_list and session_unlock_list.
1101  * A reference to the session is implicitly acquired by this function.
1102  */
1103 struct ltt_session *session_find_by_name(const char *name)
1104 {
1105         struct ltt_session *iter;
1106
1107         assert(name);
1108         ASSERT_LOCKED(ltt_session_list.lock);
1109
1110         DBG2("Trying to find session by name %s", name);
1111
1112         cds_list_for_each_entry(iter, &ltt_session_list.head, list) {
1113                 if (!strncmp(iter->name, name, NAME_MAX) &&
1114                                 !iter->destroyed) {
1115                         goto found;
1116                 }
1117         }
1118
1119         return NULL;
1120 found:
1121         return session_get(iter) ? iter : NULL;
1122 }
1123
1124 /*
1125  * Return an ltt_session that matches the id. If no session is found,
1126  * NULL is returned. This must be called with rcu_read_lock and
1127  * session list lock held (to guarantee the lifetime of the session).
1128  */
1129 struct ltt_session *session_find_by_id(uint64_t id)
1130 {
1131         struct lttng_ht_node_u64 *node;
1132         struct lttng_ht_iter iter;
1133         struct ltt_session *ls;
1134
1135         ASSERT_LOCKED(ltt_session_list.lock);
1136
1137         if (!ltt_sessions_ht_by_id) {
1138                 goto end;
1139         }
1140
1141         lttng_ht_lookup(ltt_sessions_ht_by_id, &id, &iter);
1142         node = lttng_ht_iter_get_node_u64(&iter);
1143         if (node == NULL) {
1144                 goto end;
1145         }
1146         ls = caa_container_of(node, struct ltt_session, node);
1147
1148         DBG3("Session %" PRIu64 " found by id.", id);
1149         return session_get(ls) ? ls : NULL;
1150
1151 end:
1152         DBG3("Session %" PRIu64 " NOT found by id", id);
1153         return NULL;
1154 }
1155
1156 /*
1157  * Create a new session and add it to the session list.
1158  * Session list lock must be held by the caller.
1159  */
1160 enum lttng_error_code session_create(const char *name, uid_t uid, gid_t gid,
1161                 struct ltt_session **out_session)
1162 {
1163         int ret;
1164         enum lttng_error_code ret_code;
1165         struct ltt_session *new_session = NULL;
1166
1167         ASSERT_LOCKED(ltt_session_list.lock);
1168         if (name) {
1169                 struct ltt_session *clashing_session;
1170
1171                 clashing_session = session_find_by_name(name);
1172                 if (clashing_session) {
1173                         session_put(clashing_session);
1174                         ret_code = LTTNG_ERR_EXIST_SESS;
1175                         goto error;
1176                 }
1177         }
1178         new_session = zmalloc(sizeof(struct ltt_session));
1179         if (!new_session) {
1180                 PERROR("Failed to allocate an ltt_session structure");
1181                 ret_code = LTTNG_ERR_NOMEM;
1182                 goto error;
1183         }
1184
1185         lttng_dynamic_array_init(&new_session->destroy_notifiers,
1186                         sizeof(struct ltt_session_destroy_notifier_element),
1187                         NULL);
1188         lttng_dynamic_array_init(&new_session->clear_notifiers,
1189                         sizeof(struct ltt_session_clear_notifier_element),
1190                         NULL);
1191         urcu_ref_init(&new_session->ref);
1192         pthread_mutex_init(&new_session->lock, NULL);
1193
1194         new_session->creation_time = time(NULL);
1195         if (new_session->creation_time == (time_t) -1) {
1196                 PERROR("Failed to sample session creation time");
1197                 ret_code = LTTNG_ERR_SESSION_FAIL;
1198                 goto error;
1199         }
1200
1201         /* Create default consumer output. */
1202         new_session->consumer = consumer_create_output(CONSUMER_DST_LOCAL);
1203         if (new_session->consumer == NULL) {
1204                 ret_code = LTTNG_ERR_NOMEM;
1205                 goto error;
1206         }
1207
1208         if (name) {
1209                 ret = lttng_strncpy(new_session->name, name, sizeof(new_session->name));
1210                 if (ret) {
1211                         ret_code = LTTNG_ERR_SESSION_INVALID_CHAR;
1212                         goto error;
1213                 }
1214                 ret = validate_name(name);
1215                 if (ret < 0) {
1216                         ret_code = LTTNG_ERR_SESSION_INVALID_CHAR;
1217                         goto error;
1218                 }
1219         } else {
1220                 int i = 0;
1221                 bool found_name = false;
1222                 char datetime[16];
1223                 struct tm *timeinfo;
1224
1225                 timeinfo = localtime(&new_session->creation_time);
1226                 if (!timeinfo) {
1227                         ret_code = LTTNG_ERR_SESSION_FAIL;
1228                         goto error;
1229                 }
1230                 strftime(datetime, sizeof(datetime), "%Y%m%d-%H%M%S", timeinfo);
1231                 for (i = 0; i < INT_MAX; i++) {
1232                         struct ltt_session *clashing_session;
1233
1234                         if (i == 0) {
1235                                 ret = snprintf(new_session->name,
1236                                                 sizeof(new_session->name),
1237                                                 "%s-%s",
1238                                                 DEFAULT_SESSION_NAME,
1239                                                 datetime);
1240                         } else {
1241                                 ret = snprintf(new_session->name,
1242                                                 sizeof(new_session->name),
1243                                                 "%s%d-%s",
1244                                                 DEFAULT_SESSION_NAME, i,
1245                                                 datetime);
1246                         }
1247                         new_session->name_contains_creation_time = true;
1248                         if (ret == -1 || ret >= sizeof(new_session->name)) {
1249                                 /*
1250                                  * Null-terminate in case the name is used
1251                                  * in logging statements.
1252                                  */
1253                                 new_session->name[sizeof(new_session->name) - 1] = '\0';
1254                                 ret_code = LTTNG_ERR_SESSION_FAIL;
1255                                 goto error;
1256                         }
1257
1258                         clashing_session =
1259                                         session_find_by_name(new_session->name);
1260                         session_put(clashing_session);
1261                         if (!clashing_session) {
1262                                 found_name = true;
1263                                 break;
1264                         }
1265                 }
1266                 if (found_name) {
1267                         DBG("Generated session name \"%s\"", new_session->name);
1268                         new_session->has_auto_generated_name = true;
1269                 } else {
1270                         ERR("Failed to auto-generate a session name");
1271                         ret_code = LTTNG_ERR_SESSION_FAIL;
1272                         goto error;
1273                 }
1274         }
1275
1276         ret = gethostname(new_session->hostname, sizeof(new_session->hostname));
1277         if (ret < 0) {
1278                 if (errno == ENAMETOOLONG) {
1279                         new_session->hostname[sizeof(new_session->hostname) - 1] = '\0';
1280                         ERR("Hostname exceeds the maximal permitted length and has been truncated to %s",
1281                                         new_session->hostname);
1282                 } else {
1283                         ret_code = LTTNG_ERR_SESSION_FAIL;
1284                         goto error;
1285                 }
1286         }
1287
1288         new_session->uid = uid;
1289         new_session->gid = gid;
1290
1291         ret = snapshot_init(&new_session->snapshot);
1292         if (ret < 0) {
1293                 ret_code = LTTNG_ERR_NOMEM;
1294                 goto error;
1295         }
1296
1297         new_session->rotation_state = LTTNG_ROTATION_STATE_NO_ROTATION;
1298
1299         /* Add new session to the session list. */
1300         new_session->id = add_session_list(new_session);
1301
1302         /*
1303          * Add the new session to the ltt_sessions_ht_by_id.
1304          * No ownership is taken by the hash table; it is merely
1305          * a wrapper around the session list used for faster access
1306          * by session id.
1307          */
1308         add_session_ht(new_session);
1309         new_session->published = true;
1310
1311         /*
1312          * Consumer is left to NULL since the create_session_uri command will
1313          * set it up and, if valid, assign it to the session.
1314          */
1315         DBG("Tracing session %s created with ID %" PRIu64 " by uid = %d, gid = %d",
1316                         new_session->name, new_session->id, new_session->uid,
1317                         new_session->gid);
1318         ret_code = LTTNG_OK;
1319 end:
1320         if (new_session) {
1321                 (void) session_get(new_session);
1322                 *out_session = new_session;
1323         }
1324         return ret_code;
1325 error:
1326         session_put(new_session);
1327         new_session = NULL;
1328         goto end;
1329 }
1330
1331 /*
1332  * Check if the UID matches the session. Root user has access to all
1333  * sessions.
1334  */
1335 bool session_access_ok(struct ltt_session *session, uid_t uid)
1336 {
1337         assert(session);
1338         return (uid == session->uid) || uid == 0;
1339 }
1340
1341 /*
1342  * Set a session's rotation state and reset all associated state.
1343  *
1344  * This function resets the rotation state (check timers, pending
1345  * flags, etc.) and sets the result of the last rotation. The result
1346  * can be queries by a liblttng-ctl client.
1347  *
1348  * Be careful of the result passed to this function. For instance,
1349  * on failure to launch a rotation, a client will expect the rotation
1350  * state to be set to "NO_ROTATION". If an error occurred while the
1351  * rotation was "ONGOING", result should be set to "ERROR", which will
1352  * allow a client to report it.
1353  *
1354  * Must be called with the session and session_list locks held.
1355  */
1356 int session_reset_rotation_state(struct ltt_session *session,
1357                 enum lttng_rotation_state result)
1358 {
1359         int ret = 0;
1360
1361         ASSERT_LOCKED(ltt_session_list.lock);
1362         ASSERT_LOCKED(session->lock);
1363
1364         session->rotation_state = result;
1365         if (session->rotation_pending_check_timer_enabled) {
1366                 ret = timer_session_rotation_pending_check_stop(session);
1367         }
1368         if (session->chunk_being_archived) {
1369                 uint64_t chunk_id;
1370                 enum lttng_trace_chunk_status chunk_status;
1371
1372                 chunk_status = lttng_trace_chunk_get_id(
1373                                 session->chunk_being_archived,
1374                                 &chunk_id);
1375                 assert(chunk_status == LTTNG_TRACE_CHUNK_STATUS_OK);
1376                 LTTNG_OPTIONAL_SET(&session->last_archived_chunk_id,
1377                                 chunk_id);
1378                 lttng_trace_chunk_put(session->chunk_being_archived);
1379                 session->chunk_being_archived = NULL;
1380                 /*
1381                  * Fire the clear reply notifiers if we are completing a clear
1382                  * rotation.
1383                  */
1384                 session_notify_clear(session);
1385         }
1386         return ret;
1387 }
1388
1389 /*
1390  * Sample the id of a session looked up via its name.
1391  * Here the term "sampling" hint the caller that this return the id at a given
1392  * point in time with no guarantee that the session for which the id was
1393  * sampled still exist at that point.
1394  *
1395  * Return 0 when the session is not found,
1396  * Return 1 when the session is found and set `id`.
1397  */
1398 bool sample_session_id_by_name(const char *name, uint64_t *id)
1399 {
1400         bool found = false;
1401         struct lttng_ht_node_str *node;
1402         struct lttng_ht_iter iter;
1403         struct ltt_session *ls;
1404
1405         rcu_read_lock();
1406
1407         if (!ltt_sessions_ht_by_name) {
1408                 found = false;
1409                 goto end;
1410         }
1411
1412         lttng_ht_lookup(ltt_sessions_ht_by_name, name, &iter);
1413         node = lttng_ht_iter_get_node_str(&iter);
1414         if (node == NULL) {
1415                 found = false;
1416                 goto end;
1417         }
1418
1419         ls = caa_container_of(node, struct ltt_session, node_by_name);
1420         *id = ls->id;
1421         found = true;
1422
1423         DBG3("Session id `%" PRIu64 "` sampled for session `%s", *id, name);
1424 end:
1425         rcu_read_unlock();
1426         return found;
1427 }