src/bin/lttng-sessiond/notification-thread.c

   1 /*
   2  * Copyright (C) 2017 Jérémie Galarneau <jeremie.galarneau@efficios.com>
   3  *
   4  * SPDX-License-Identifier: GPL-2.0-only
   5  *
   6  */
   7
   8 #define _LGPL_SOURCE
   9 #include <lttng/trigger/trigger.h>
  10 #include <lttng/notification/channel-internal.h>
  11 #include <lttng/notification/notification-internal.h>
  12 #include <lttng/condition/condition-internal.h>
  13 #include <lttng/condition/buffer-usage-internal.h>
  14 #include <common/error.h>
  15 #include <common/config/session-config.h>
  16 #include <common/defaults.h>
  17 #include <common/utils.h>
  18 #include <common/align.h>
  19 #include <common/time.h>
  20 #include <sys/stat.h>
  21 #include <time.h>
  22 #include <signal.h>
  23
  24 #include "notification-thread.h"
  25 #include "notification-thread-events.h"
  26 #include "notification-thread-commands.h"
  27 #include "lttng-sessiond.h"
  28 #include "health-sessiond.h"
  29 #include "thread.h"
  30
  31 #include <urcu.h>
  32 #include <urcu/list.h>
  33 #include <urcu/rculfhash.h>
  34
  35 /*
  36  * Destroy the thread data previously created by the init function.
  37  */
  38 void notification_thread_handle_destroy(
  39                 struct notification_thread_handle *handle)
  40 {
  41         int ret;
  42
  43         if (!handle) {
  44                 goto end;
  45         }
  46
  47         assert(cds_list_empty(&handle->cmd_queue.list));
  48         pthread_mutex_destroy(&handle->cmd_queue.lock);
  49         sem_destroy(&handle->ready);
  50
  51         if (handle->cmd_queue.event_pipe) {
  52                 lttng_pipe_destroy(handle->cmd_queue.event_pipe);
  53         }
  54         if (handle->channel_monitoring_pipes.ust32_consumer >= 0) {
  55                 ret = close(handle->channel_monitoring_pipes.ust32_consumer);
  56                 if (ret) {
  57                         PERROR("close 32-bit consumer channel monitoring pipe");
  58                 }
  59         }
  60         if (handle->channel_monitoring_pipes.ust64_consumer >= 0) {
  61                 ret = close(handle->channel_monitoring_pipes.ust64_consumer);
  62                 if (ret) {
  63                         PERROR("close 64-bit consumer channel monitoring pipe");
  64                 }
  65         }
  66         if (handle->channel_monitoring_pipes.kernel_consumer >= 0) {
  67                 ret = close(handle->channel_monitoring_pipes.kernel_consumer);
  68                 if (ret) {
  69                         PERROR("close kernel consumer channel monitoring pipe");
  70                 }
  71         }
  72 end:
  73         free(handle);
  74 }
  75
  76 struct notification_thread_handle *notification_thread_handle_create(
  77                 struct lttng_pipe *ust32_channel_monitor_pipe,
  78                 struct lttng_pipe *ust64_channel_monitor_pipe,
  79                 struct lttng_pipe *kernel_channel_monitor_pipe)
  80 {
  81         int ret;
  82         struct notification_thread_handle *handle;
  83         struct lttng_pipe *event_pipe = NULL;
  84
  85         handle = zmalloc(sizeof(*handle));
  86         if (!handle) {
  87                 goto end;
  88         }
  89
  90         sem_init(&handle->ready, 0, 0);
  91
  92         event_pipe = lttng_pipe_open(FD_CLOEXEC);
  93         if (!event_pipe) {
  94                 ERR("event_pipe creation");
  95                 goto error;
  96         }
  97
  98         handle->cmd_queue.event_pipe = event_pipe;
  99         event_pipe = NULL;
 100
 101         CDS_INIT_LIST_HEAD(&handle->cmd_queue.list);
 102         ret = pthread_mutex_init(&handle->cmd_queue.lock, NULL);
 103         if (ret) {
 104                 goto error;
 105         }
 106
 107         if (ust32_channel_monitor_pipe) {
 108                 handle->channel_monitoring_pipes.ust32_consumer =
 109                                 lttng_pipe_release_readfd(
 110                                         ust32_channel_monitor_pipe);
 111                 if (handle->channel_monitoring_pipes.ust32_consumer < 0) {
 112                         goto error;
 113                 }
 114         } else {
 115                 handle->channel_monitoring_pipes.ust32_consumer = -1;
 116         }
 117         if (ust64_channel_monitor_pipe) {
 118                 handle->channel_monitoring_pipes.ust64_consumer =
 119                                 lttng_pipe_release_readfd(
 120                                         ust64_channel_monitor_pipe);
 121                 if (handle->channel_monitoring_pipes.ust64_consumer < 0) {
 122                         goto error;
 123                 }
 124         } else {
 125                 handle->channel_monitoring_pipes.ust64_consumer = -1;
 126         }
 127         if (kernel_channel_monitor_pipe) {
 128                 handle->channel_monitoring_pipes.kernel_consumer =
 129                                 lttng_pipe_release_readfd(
 130                                         kernel_channel_monitor_pipe);
 131                 if (handle->channel_monitoring_pipes.kernel_consumer < 0) {
 132                         goto error;
 133                 }
 134         } else {
 135                 handle->channel_monitoring_pipes.kernel_consumer = -1;
 136         }
 137
 138 end:
 139         return handle;
 140 error:
 141         lttng_pipe_destroy(event_pipe);
 142         notification_thread_handle_destroy(handle);
 143         return NULL;
 144 }
 145
 146 static
 147 char *get_notification_channel_sock_path(void)
 148 {
 149         int ret;
 150         bool is_root = !getuid();
 151         char *sock_path;
 152
 153         sock_path = zmalloc(LTTNG_PATH_MAX);
 154         if (!sock_path) {
 155                 goto error;
 156         }
 157
 158         if (is_root) {
 159                 ret = snprintf(sock_path, LTTNG_PATH_MAX,
 160                                 DEFAULT_GLOBAL_NOTIFICATION_CHANNEL_UNIX_SOCK);
 161                 if (ret < 0) {
 162                         goto error;
 163                 }
 164         } else {
 165                 const char *home_path = utils_get_home_dir();
 166
 167                 if (!home_path) {
 168                         ERR("Can't get HOME directory for socket creation");
 169                         goto error;
 170                 }
 171
 172                 ret = snprintf(sock_path, LTTNG_PATH_MAX,
 173                                 DEFAULT_HOME_NOTIFICATION_CHANNEL_UNIX_SOCK,
 174                                 home_path);
 175                 if (ret < 0) {
 176                         goto error;
 177                 }
 178         }
 179
 180         return sock_path;
 181 error:
 182         free(sock_path);
 183         return NULL;
 184 }
 185
 186 static
 187 void notification_channel_socket_destroy(int fd)
 188 {
 189         int ret;
 190         char *sock_path = get_notification_channel_sock_path();
 191
 192         DBG("[notification-thread] Destroying notification channel socket");
 193
 194         if (sock_path) {
 195                 ret = unlink(sock_path);
 196                 free(sock_path);
 197                 if (ret < 0) {
 198                         PERROR("unlink notification channel socket");
 199                 }
 200         }
 201
 202         ret = close(fd);
 203         if (ret) {
 204                 PERROR("close notification channel socket");
 205         }
 206 }
 207
 208 static
 209 int notification_channel_socket_create(void)
 210 {
 211         int fd = -1, ret;
 212         char *sock_path = get_notification_channel_sock_path();
 213
 214         DBG("[notification-thread] Creating notification channel UNIX socket at %s",
 215                         sock_path);
 216
 217         ret = lttcomm_create_unix_sock(sock_path);
 218         if (ret < 0) {
 219                 ERR("[notification-thread] Failed to create notification socket");
 220                 goto error;
 221         }
 222         fd = ret;
 223
 224         ret = chmod(sock_path, S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP);
 225         if (ret < 0) {
 226                 ERR("Set file permissions failed: %s", sock_path);
 227                 PERROR("chmod notification channel socket");
 228                 goto error;
 229         }
 230
 231         if (getuid() == 0) {
 232                 gid_t gid;
 233
 234                 ret =  utils_get_group_id(config.tracing_group_name.value, true,
 235                                 &gid);
 236                 if (ret) {
 237                         /* Default to root group. */
 238                         gid = 0;
 239                 }
 240
 241                 ret = chown(sock_path, 0, gid);
 242                 if (ret) {
 243                         ERR("Failed to set the notification channel socket's group");
 244                         ret = -1;
 245                         goto error;
 246                 }
 247         }
 248
 249         DBG("[notification-thread] Notification channel UNIX socket created (fd = %i)",
 250                         fd);
 251         free(sock_path);
 252         return fd;
 253 error:
 254         if (fd >= 0 && close(fd) < 0) {
 255                 PERROR("close notification channel socket");
 256         }
 257         free(sock_path);
 258         return ret;
 259 }
 260
 261 static
 262 int init_poll_set(struct lttng_poll_event *poll_set,
 263                 struct notification_thread_handle *handle,
 264                 int notification_channel_socket)
 265 {
 266         int ret;
 267
 268         /*
 269          * Create pollset with size 5:
 270          *      - notification channel socket (listen for new connections),
 271          *      - command queue event fd (internal sessiond commands),
 272          *      - consumerd (32-bit user space) channel monitor pipe,
 273          *      - consumerd (64-bit user space) channel monitor pipe,
 274          *      - consumerd (kernel) channel monitor pipe.
 275          */
 276         ret = lttng_poll_create(poll_set, 5, LTTNG_CLOEXEC);
 277         if (ret < 0) {
 278                 goto end;
 279         }
 280
 281         ret = lttng_poll_add(poll_set, notification_channel_socket,
 282                         LPOLLIN | LPOLLERR | LPOLLHUP | LPOLLRDHUP);
 283         if (ret < 0) {
 284                 ERR("[notification-thread] Failed to add notification channel socket to pollset");
 285                 goto error;
 286         }
 287         ret = lttng_poll_add(poll_set, lttng_pipe_get_readfd(handle->cmd_queue.event_pipe),
 288                         LPOLLIN | LPOLLERR);
 289         if (ret < 0) {
 290                 ERR("[notification-thread] Failed to add notification command queue event fd to pollset");
 291                 goto error;
 292         }
 293         ret = lttng_poll_add(poll_set,
 294                         handle->channel_monitoring_pipes.ust32_consumer,
 295                         LPOLLIN | LPOLLERR);
 296         if (ret < 0) {
 297                 ERR("[notification-thread] Failed to add ust-32 channel monitoring pipe fd to pollset");
 298                 goto error;
 299         }
 300         ret = lttng_poll_add(poll_set,
 301                         handle->channel_monitoring_pipes.ust64_consumer,
 302                         LPOLLIN | LPOLLERR);
 303         if (ret < 0) {
 304                 ERR("[notification-thread] Failed to add ust-64 channel monitoring pipe fd to pollset");
 305                 goto error;
 306         }
 307         if (handle->channel_monitoring_pipes.kernel_consumer < 0) {
 308                 goto end;
 309         }
 310         ret = lttng_poll_add(poll_set,
 311                         handle->channel_monitoring_pipes.kernel_consumer,
 312                         LPOLLIN | LPOLLERR);
 313         if (ret < 0) {
 314                 ERR("[notification-thread] Failed to add kernel channel monitoring pipe fd to pollset");
 315                 goto error;
 316         }
 317 end:
 318         return ret;
 319 error:
 320         lttng_poll_clean(poll_set);
 321         return ret;
 322 }
 323
 324 static
 325 void fini_thread_state(struct notification_thread_state *state)
 326 {
 327         int ret;
 328
 329         if (state->client_socket_ht) {
 330                 ret = handle_notification_thread_client_disconnect_all(state);
 331                 assert(!ret);
 332                 ret = cds_lfht_destroy(state->client_socket_ht, NULL);
 333                 assert(!ret);
 334         }
 335         if (state->client_id_ht) {
 336                 ret = cds_lfht_destroy(state->client_id_ht, NULL);
 337                 assert(!ret);
 338         }
 339         if (state->triggers_ht) {
 340                 ret = handle_notification_thread_trigger_unregister_all(state);
 341                 assert(!ret);
 342                 ret = cds_lfht_destroy(state->triggers_ht, NULL);
 343                 assert(!ret);
 344         }
 345         if (state->channel_triggers_ht) {
 346                 ret = cds_lfht_destroy(state->channel_triggers_ht, NULL);
 347                 assert(!ret);
 348         }
 349         if (state->channel_state_ht) {
 350                 ret = cds_lfht_destroy(state->channel_state_ht, NULL);
 351                 assert(!ret);
 352         }
 353         if (state->notification_trigger_clients_ht) {
 354                 ret = cds_lfht_destroy(state->notification_trigger_clients_ht,
 355                                 NULL);
 356                 assert(!ret);
 357         }
 358         if (state->channels_ht) {
 359                 ret = cds_lfht_destroy(state->channels_ht, NULL);
 360                 assert(!ret);
 361         }
 362         if (state->sessions_ht) {
 363                 ret = cds_lfht_destroy(state->sessions_ht, NULL);
 364                 assert(!ret);
 365         }
 366         if (state->triggers_by_name_uid_ht) {
 367                 ret = cds_lfht_destroy(state->triggers_by_name_uid_ht, NULL);
 368                 assert(!ret);
 369         }
 370         /*
 371          * Must be destroyed after all channels have been destroyed.
 372          * See comment in struct lttng_session_trigger_list.
 373          */
 374         if (state->session_triggers_ht) {
 375                 ret = cds_lfht_destroy(state->session_triggers_ht, NULL);
 376                 assert(!ret);
 377         }
 378         if (state->notification_channel_socket >= 0) {
 379                 notification_channel_socket_destroy(
 380                                 state->notification_channel_socket);
 381         }
 382
 383         assert(cds_list_empty(&state->tracer_event_sources_list));
 384
 385         if (state->executor) {
 386                 action_executor_destroy(state->executor);
 387         }
 388         lttng_poll_clean(&state->events);
 389 }
 390
 391 static
 392 void mark_thread_as_ready(struct notification_thread_handle *handle)
 393 {
 394         DBG("Marking notification thread as ready");
 395         sem_post(&handle->ready);
 396 }
 397
 398 static
 399 void wait_until_thread_is_ready(struct notification_thread_handle *handle)
 400 {
 401         DBG("Waiting for notification thread to be ready");
 402         sem_wait(&handle->ready);
 403         DBG("Notification thread is ready");
 404 }
 405
 406 static
 407 int init_thread_state(struct notification_thread_handle *handle,
 408                 struct notification_thread_state *state)
 409 {
 410         int ret;
 411
 412         memset(state, 0, sizeof(*state));
 413         state->notification_channel_socket = -1;
 414         state->trigger_id.next_tracer_token = 1;
 415         lttng_poll_init(&state->events);
 416
 417         ret = notification_channel_socket_create();
 418         if (ret < 0) {
 419                 goto end;
 420         }
 421         state->notification_channel_socket = ret;
 422
 423         ret = init_poll_set(&state->events, handle,
 424                         state->notification_channel_socket);
 425         if (ret) {
 426                 goto end;
 427         }
 428
 429         DBG("[notification-thread] Listening on notification channel socket");
 430         ret = lttcomm_listen_unix_sock(state->notification_channel_socket);
 431         if (ret < 0) {
 432                 ERR("[notification-thread] Listen failed on notification channel socket");
 433                 goto error;
 434         }
 435
 436         state->client_socket_ht = cds_lfht_new(DEFAULT_HT_SIZE, 1, 0,
 437                         CDS_LFHT_AUTO_RESIZE | CDS_LFHT_ACCOUNTING, NULL);
 438         if (!state->client_socket_ht) {
 439                 goto error;
 440         }
 441
 442         state->client_id_ht = cds_lfht_new(DEFAULT_HT_SIZE, 1, 0,
 443                         CDS_LFHT_AUTO_RESIZE | CDS_LFHT_ACCOUNTING, NULL);
 444         if (!state->client_id_ht) {
 445                 goto error;
 446         }
 447
 448         state->channel_triggers_ht = cds_lfht_new(DEFAULT_HT_SIZE, 1, 0,
 449                         CDS_LFHT_AUTO_RESIZE | CDS_LFHT_ACCOUNTING, NULL);
 450         if (!state->channel_triggers_ht) {
 451                 goto error;
 452         }
 453
 454         state->session_triggers_ht = cds_lfht_new(DEFAULT_HT_SIZE, 1, 0,
 455                         CDS_LFHT_AUTO_RESIZE | CDS_LFHT_ACCOUNTING, NULL);
 456         if (!state->session_triggers_ht) {
 457                 goto error;
 458         }
 459
 460         state->channel_state_ht = cds_lfht_new(DEFAULT_HT_SIZE, 1, 0,
 461                         CDS_LFHT_AUTO_RESIZE | CDS_LFHT_ACCOUNTING, NULL);
 462         if (!state->channel_state_ht) {
 463                 goto error;
 464         }
 465
 466         state->notification_trigger_clients_ht = cds_lfht_new(DEFAULT_HT_SIZE,
 467                         1, 0, CDS_LFHT_AUTO_RESIZE | CDS_LFHT_ACCOUNTING, NULL);
 468         if (!state->notification_trigger_clients_ht) {
 469                 goto error;
 470         }
 471
 472         state->channels_ht = cds_lfht_new(DEFAULT_HT_SIZE,
 473                         1, 0, CDS_LFHT_AUTO_RESIZE | CDS_LFHT_ACCOUNTING, NULL);
 474         if (!state->channels_ht) {
 475                 goto error;
 476         }
 477         state->sessions_ht = cds_lfht_new(DEFAULT_HT_SIZE,
 478                         1, 0, CDS_LFHT_AUTO_RESIZE | CDS_LFHT_ACCOUNTING, NULL);
 479         if (!state->sessions_ht) {
 480                 goto error;
 481         }
 482         state->triggers_ht = cds_lfht_new(DEFAULT_HT_SIZE,
 483                         1, 0, CDS_LFHT_AUTO_RESIZE | CDS_LFHT_ACCOUNTING, NULL);
 484         if (!state->triggers_ht) {
 485                 goto error;
 486         }
 487         state->triggers_by_name_uid_ht = cds_lfht_new(DEFAULT_HT_SIZE,
 488                         1, 0, CDS_LFHT_AUTO_RESIZE | CDS_LFHT_ACCOUNTING, NULL);
 489         if (!state->triggers_by_name_uid_ht) {
 490                 goto error;
 491         }
 492
 493         CDS_INIT_LIST_HEAD(&state->tracer_event_sources_list);
 494
 495         state->executor = action_executor_create(handle);
 496         if (!state->executor) {
 497                 goto error;
 498         }
 499         mark_thread_as_ready(handle);
 500 end:
 501         return 0;
 502 error:
 503         fini_thread_state(state);
 504         return -1;
 505 }
 506
 507 static
 508 int handle_channel_monitoring_pipe(int fd, uint32_t revents,
 509                 struct notification_thread_handle *handle,
 510                 struct notification_thread_state *state)
 511 {
 512         int ret = 0;
 513         enum lttng_domain_type domain;
 514
 515         if (fd == handle->channel_monitoring_pipes.ust32_consumer ||
 516                         fd == handle->channel_monitoring_pipes.ust64_consumer) {
 517                 domain = LTTNG_DOMAIN_UST;
 518         } else if (fd == handle->channel_monitoring_pipes.kernel_consumer) {
 519                 domain = LTTNG_DOMAIN_KERNEL;
 520         } else {
 521                 abort();
 522         }
 523
 524         if (revents & (LPOLLERR | LPOLLHUP | LPOLLRDHUP)) {
 525                 ret = lttng_poll_del(&state->events, fd);
 526                 if (ret) {
 527                         ERR("[notification-thread] Failed to remove consumer monitoring pipe from poll set");
 528                 }
 529                 goto end;
 530         }
 531
 532         ret = handle_notification_thread_channel_sample(
 533                         state, fd, domain);
 534         if (ret) {
 535                 ERR("[notification-thread] Consumer sample handling error occurred");
 536                 ret = -1;
 537                 goto end;
 538         }
 539 end:
 540         return ret;
 541 }
 542
 543 /*
 544  * This thread services notification channel clients and commands received
 545  * from various lttng-sessiond components over a command queue.
 546  */
 547 static
 548 void *thread_notification(void *data)
 549 {
 550         int ret;
 551         struct notification_thread_handle *handle = data;
 552         struct notification_thread_state state;
 553
 554         DBG("[notification-thread] Started notification thread");
 555
 556         health_register(health_sessiond, HEALTH_SESSIOND_TYPE_NOTIFICATION);
 557         rcu_register_thread();
 558         rcu_thread_online();
 559
 560         if (!handle) {
 561                 ERR("[notification-thread] Invalid thread context provided");
 562                 goto end;
 563         }
 564
 565         health_code_update();
 566
 567         ret = init_thread_state(handle, &state);
 568         if (ret) {
 569                 goto end;
 570         }
 571
 572         while (true) {
 573                 int fd_count, i;
 574
 575                 health_poll_entry();
 576                 DBG("[notification-thread] Entering poll wait");
 577                 ret = lttng_poll_wait(&state.events, -1);
 578                 DBG("[notification-thread] Poll wait returned (%i)", ret);
 579                 health_poll_exit();
 580                 if (ret < 0) {
 581                         /*
 582                          * Restart interrupted system call.
 583                          */
 584                         if (errno == EINTR) {
 585                                 continue;
 586                         }
 587                         ERR("[notification-thread] Error encountered during lttng_poll_wait (%i)", ret);
 588                         goto error;
 589                 }
 590
 591                 fd_count = ret;
 592                 for (i = 0; i < fd_count; i++) {
 593                         int fd = LTTNG_POLL_GETFD(&state.events, i);
 594                         uint32_t revents = LTTNG_POLL_GETEV(&state.events, i);
 595
 596                         DBG("[notification-thread] Handling fd (%i) activity (%u)", fd, revents);
 597
 598                         if (fd == state.notification_channel_socket) {
 599                                 if (revents & LPOLLIN) {
 600                                         ret = handle_notification_thread_client_connect(
 601                                                         &state);
 602                                         if (ret < 0) {
 603                                                 goto error;
 604                                         }
 605                                 } else if (revents &
 606                                                 (LPOLLERR | LPOLLHUP | LPOLLRDHUP)) {
 607                                         ERR("[notification-thread] Notification socket poll error");
 608                                         goto error;
 609                                 } else {
 610                                         ERR("[notification-thread] Unexpected poll events %u for notification socket %i", revents, fd);
 611                                         goto error;
 612                                 }
 613                         } else if (fd == lttng_pipe_get_readfd(handle->cmd_queue.event_pipe)) {
 614                                 ret = handle_notification_thread_command(handle,
 615                                                 &state);
 616                                 if (ret < 0) {
 617                                         DBG("[notification-thread] Error encountered while servicing command queue");
 618                                         goto error;
 619                                 } else if (ret > 0) {
 620                                         goto exit;
 621                                 }
 622                         } else if (fd == handle->channel_monitoring_pipes.ust32_consumer ||
 623                                         fd == handle->channel_monitoring_pipes.ust64_consumer ||
 624                                         fd == handle->channel_monitoring_pipes.kernel_consumer) {
 625                                 ret = handle_channel_monitoring_pipe(fd,
 626                                                 revents, handle, &state);
 627                                 if (ret) {
 628                                         goto error;
 629                                 }
 630                         } else {
 631                                 /* Activity on a client's socket. */
 632                                 if (revents & (LPOLLERR | LPOLLHUP | LPOLLRDHUP)) {
 633                                         /*
 634                                          * It doesn't matter if a command was
 635                                          * pending on the client socket at this
 636                                          * point since it now has no way to
 637                                          * receive the notifications to which
 638                                          * it was subscribing or unsubscribing.
 639                                          */
 640                                         ret = handle_notification_thread_client_disconnect(
 641                                                         fd, &state);
 642                                         if (ret) {
 643                                                 goto error;
 644                                         }
 645                                 } else {
 646                                         if (revents & LPOLLIN) {
 647                                                 ret = handle_notification_thread_client_in(
 648                                                         &state, fd);
 649                                                 if (ret) {
 650                                                         goto error;
 651                                                 }
 652                                         }
 653
 654                                         if (revents & LPOLLOUT) {
 655                                                 ret = handle_notification_thread_client_out(
 656                                                         &state, fd);
 657                                                 if (ret) {
 658                                                         goto error;
 659                                                 }
 660                                         }
 661                                 }
 662                         }
 663                 }
 664         }
 665 exit:
 666 error:
 667         fini_thread_state(&state);
 668 end:
 669         rcu_thread_offline();
 670         rcu_unregister_thread();
 671         health_unregister(health_sessiond);
 672         return NULL;
 673 }
 674
 675 static
 676 bool shutdown_notification_thread(void *thread_data)
 677 {
 678         struct notification_thread_handle *handle = thread_data;
 679
 680         notification_thread_command_quit(handle);
 681         return true;
 682 }
 683
 684 struct lttng_thread *launch_notification_thread(
 685                 struct notification_thread_handle *handle)
 686 {
 687         struct lttng_thread *thread;
 688
 689         thread = lttng_thread_create("Notification",
 690                         thread_notification,
 691                         shutdown_notification_thread,
 692                         NULL,
 693                         handle);
 694         if (!thread) {
 695                 goto error;
 696         }
 697
 698         /*
 699          * Wait for the thread to be marked as "ready" before returning
 700          * as other subsystems depend on the notification subsystem
 701          * (e.g. rotation thread).
 702          */
 703         wait_until_thread_is_ready(handle);
 704         return thread;
 705 error:
 706         return NULL;
 707 }