src/bin/lttng-sessiond/action-executor.c

   1 /*
   2  * Copyright (C) 2020 Jérémie Galarneau <jeremie.galarneau@efficios.com>
   3  *
   4  * SPDX-License-Identifier: GPL-2.0-only
   5  *
   6  */
   7
   8 #include "action-executor.h"
   9 #include "cmd.h"
  10 #include "health-sessiond.h"
  11 #include "lttng-sessiond.h"
  12 #include "notification-thread-internal.h"
  13 #include "session.h"
  14 #include "thread.h"
  15 #include <common/macros.h>
  16 #include <common/optional.h>
  17 #include <lttng/action/action-internal.h>
  18 #include <lttng/action/group.h>
  19 #include <lttng/action/notify.h>
  20 #include <lttng/action/rotate-session.h>
  21 #include <lttng/action/snapshot-session.h>
  22 #include <lttng/action/start-session.h>
  23 #include <lttng/action/stop-session.h>
  24 #include <lttng/condition/evaluation.h>
  25 #include <lttng/lttng-error.h>
  26 #include <lttng/trigger/trigger-internal.h>
  27 #include <pthread.h>
  28 #include <stdbool.h>
  29 #include <stddef.h>
  30 #include <urcu/list.h>
  31
  32 #define THREAD_NAME "Action Executor"
  33 #define MAX_QUEUED_WORK_COUNT 8192
  34
  35 struct action_work_item {
  36         uint64_t id;
  37         struct lttng_trigger *trigger;
  38         struct lttng_evaluation *evaluation;
  39         struct notification_client_list *client_list;
  40         LTTNG_OPTIONAL(struct lttng_credentials) object_creds;
  41         struct cds_list_head list_node;
  42 };
  43
  44 struct action_executor {
  45         struct lttng_thread *thread;
  46         struct notification_thread_handle *notification_thread_handle;
  47         struct {
  48                 uint64_t pending_count;
  49                 struct cds_list_head list;
  50                 pthread_cond_t cond;
  51                 pthread_mutex_t lock;
  52         } work;
  53         bool should_quit;
  54         uint64_t next_work_item_id;
  55 };
  56
  57 /*
  58  * Only return non-zero on a fatal error that should shut down the action
  59  * executor.
  60  */
  61 typedef int (*action_executor_handler)(struct action_executor *executor,
  62                 const struct action_work_item *,
  63                 const struct lttng_action *action);
  64
  65 static int action_executor_notify_handler(struct action_executor *executor,
  66                 const struct action_work_item *,
  67                 const struct lttng_action *);
  68 static int action_executor_start_session_handler(struct action_executor *executor,
  69                 const struct action_work_item *,
  70                 const struct lttng_action *);
  71 static int action_executor_stop_session_handler(struct action_executor *executor,
  72                 const struct action_work_item *,
  73                 const struct lttng_action *);
  74 static int action_executor_rotate_session_handler(struct action_executor *executor,
  75                 const struct action_work_item *,
  76                 const struct lttng_action *);
  77 static int action_executor_snapshot_session_handler(struct action_executor *executor,
  78                 const struct action_work_item *,
  79                 const struct lttng_action *);
  80 static int action_executor_group_handler(struct action_executor *executor,
  81                 const struct action_work_item *,
  82                 const struct lttng_action *);
  83 static int action_executor_generic_handler(struct action_executor *executor,
  84                 const struct action_work_item *,
  85                 const struct lttng_action *);
  86
  87 static const action_executor_handler action_executors[] = {
  88         [LTTNG_ACTION_TYPE_NOTIFY] = action_executor_notify_handler,
  89         [LTTNG_ACTION_TYPE_START_SESSION] = action_executor_start_session_handler,
  90         [LTTNG_ACTION_TYPE_STOP_SESSION] = action_executor_stop_session_handler,
  91         [LTTNG_ACTION_TYPE_ROTATE_SESSION] = action_executor_rotate_session_handler,
  92         [LTTNG_ACTION_TYPE_SNAPSHOT_SESSION] = action_executor_snapshot_session_handler,
  93         [LTTNG_ACTION_TYPE_GROUP] = action_executor_group_handler,
  94 };
  95
  96 static const char *action_type_names[] = {
  97         [LTTNG_ACTION_TYPE_NOTIFY] = "Notify",
  98         [LTTNG_ACTION_TYPE_START_SESSION] = "Start session",
  99         [LTTNG_ACTION_TYPE_STOP_SESSION] = "Stop session",
 100         [LTTNG_ACTION_TYPE_ROTATE_SESSION] = "Rotate session",
 101         [LTTNG_ACTION_TYPE_SNAPSHOT_SESSION] = "Snapshot session",
 102         [LTTNG_ACTION_TYPE_GROUP] = "Group",
 103 };
 104
 105 static const char *get_action_name(const struct lttng_action *action)
 106 {
 107         const enum lttng_action_type action_type = lttng_action_get_type(action);
 108
 109         assert(action_type != LTTNG_ACTION_TYPE_UNKNOWN);
 110
 111         return action_type_names[action_type];
 112 }
 113
 114 /* Check if this trigger allowed to interect with a given session. */
 115 static bool is_trigger_allowed_for_session(const struct lttng_trigger *trigger,
 116                 struct ltt_session *session)
 117 {
 118         bool is_allowed = false;
 119         const struct lttng_credentials session_creds = {
 120                 .uid = LTTNG_OPTIONAL_INIT_VALUE(session->uid),
 121                 .gid = LTTNG_OPTIONAL_INIT_VALUE(session->gid),
 122         };
 123         /* Can never be NULL. */
 124         const struct lttng_credentials *trigger_creds =
 125                         lttng_trigger_get_credentials(trigger);
 126
 127         is_allowed = (lttng_credentials_is_equal_uid(trigger_creds, &session_creds)) ||
 128                         (lttng_credentials_get_uid(trigger_creds) == 0);
 129         if (!is_allowed) {
 130                 WARN("Trigger is not allowed to interact with session `%s`: session uid = %ld, session gid = %ld, trigger uid = %ld",
 131                                 session->name,
 132                                 (long int) session->uid,
 133                                 (long int) session->gid,
 134                                 (long int) lttng_credentials_get_uid(trigger_creds));
 135         }
 136
 137         return is_allowed;
 138 }
 139
 140 static const char *get_trigger_name(const struct lttng_trigger *trigger)
 141 {
 142         const char *trigger_name;
 143         enum lttng_trigger_status trigger_status;
 144
 145         trigger_status = lttng_trigger_get_name(trigger, &trigger_name);
 146         assert(trigger_status == LTTNG_TRIGGER_STATUS_OK);
 147
 148         return trigger_name;
 149 }
 150
 151 static int client_handle_transmission_status(
 152                 struct notification_client *client,
 153                 enum client_transmission_status status,
 154                 void *user_data)
 155 {
 156         int ret = 0;
 157         struct action_executor *executor = user_data;
 158         bool update_communication = true;
 159
 160         switch (status) {
 161         case CLIENT_TRANSMISSION_STATUS_COMPLETE:
 162                 DBG("Successfully sent full notification to client, client_id = %" PRIu64,
 163                                 client->id);
 164                 update_communication = false;
 165                 break;
 166         case CLIENT_TRANSMISSION_STATUS_QUEUED:
 167                 DBG("Queued notification in client outgoing buffer, client_id = %" PRIu64,
 168                                 client->id);
 169                 break;
 170         case CLIENT_TRANSMISSION_STATUS_FAIL:
 171                 DBG("Communication error occurred while sending notification to client, client_id = %" PRIu64,
 172                                 client->id);
 173                 break;
 174         default:
 175                 ERR("Fatal error encoutered while sending notification to client, client_id = %" PRIu64,
 176                                 client->id);
 177                 ret = -1;
 178                 goto end;
 179         }
 180
 181         if (!update_communication) {
 182                 goto end;
 183         }
 184
 185         /* Safe to read client's id without locking as it is immutable. */
 186         ret = notification_thread_client_communication_update(
 187                         executor->notification_thread_handle, client->id,
 188                         status);
 189 end:
 190         return ret;
 191 }
 192
 193 static int action_executor_notify_handler(struct action_executor *executor,
 194                 const struct action_work_item *work_item,
 195                 const struct lttng_action *action)
 196 {
 197         return notification_client_list_send_evaluation(work_item->client_list,
 198                         lttng_trigger_get_const_condition(work_item->trigger),
 199                         work_item->evaluation,
 200                         lttng_trigger_get_credentials(work_item->trigger),
 201                         work_item->object_creds.is_set ?
 202                                         &(work_item->object_creds.value) :
 203                                         NULL,
 204                         client_handle_transmission_status, executor);
 205 }
 206
 207 static int action_executor_start_session_handler(struct action_executor *executor,
 208                 const struct action_work_item *work_item,
 209                 const struct lttng_action *action)
 210 {
 211         int ret = 0;
 212         const char *session_name;
 213         enum lttng_action_status action_status;
 214         struct ltt_session *session;
 215         enum lttng_error_code cmd_ret;
 216
 217         action_status = lttng_action_start_session_get_session_name(
 218                         action, &session_name);
 219         if (action_status != LTTNG_ACTION_STATUS_OK) {
 220                 ERR("Failed to get session name from `%s` action",
 221                                 get_action_name(action));
 222                 ret = -1;
 223                 goto end;
 224         }
 225
 226         session_lock_list();
 227         session = session_find_by_name(session_name);
 228         if (!session) {
 229                 DBG("Failed to find session `%s` by name while executing `%s` action of trigger `%s`",
 230                                 session_name, get_action_name(action),
 231                                 get_trigger_name(work_item->trigger));
 232                 goto error_unlock_list;
 233         }
 234
 235         session_lock(session);
 236         if (!is_trigger_allowed_for_session(work_item->trigger, session)) {
 237                 goto error_dispose_session;
 238         }
 239
 240         cmd_ret = cmd_start_trace(session);
 241         switch (cmd_ret) {
 242         case LTTNG_OK:
 243                 DBG("Successfully started session `%s` on behalf of trigger `%s`",
 244                                 session_name, get_trigger_name(work_item->trigger));
 245                 break;
 246         case LTTNG_ERR_TRACE_ALREADY_STARTED:
 247                 DBG("Attempted to start session `%s` on behalf of trigger `%s` but it was already started",
 248                                 session_name, get_trigger_name(work_item->trigger));
 249                 break;
 250         default:
 251                 WARN("Failed to start session `%s` on behalf of trigger `%s`: %s",
 252                                 session_name, get_trigger_name(work_item->trigger),
 253                                 lttng_strerror(-cmd_ret));
 254                 break;
 255         }
 256
 257 error_dispose_session:
 258         session_unlock(session);
 259         session_put(session);
 260 error_unlock_list:
 261         session_unlock_list();
 262 end:
 263         return ret;
 264 }
 265
 266 static int action_executor_stop_session_handler(struct action_executor *executor,
 267                 const struct action_work_item *work_item,
 268                 const struct lttng_action *action)
 269 {
 270         int ret = 0;
 271         const char *session_name;
 272         enum lttng_action_status action_status;
 273         struct ltt_session *session;
 274         enum lttng_error_code cmd_ret;
 275
 276         action_status = lttng_action_stop_session_get_session_name(
 277                         action, &session_name);
 278         if (action_status != LTTNG_ACTION_STATUS_OK) {
 279                 ERR("Failed to get session name from `%s` action",
 280                                 get_action_name(action));
 281                 ret = -1;
 282                 goto end;
 283         }
 284
 285         session_lock_list();
 286         session = session_find_by_name(session_name);
 287         if (!session) {
 288                 DBG("Failed to find session `%s` by name while executing `%s` action of trigger `%s`",
 289                                 session_name, get_action_name(action),
 290                                 get_trigger_name(work_item->trigger));
 291                 goto error_unlock_list;
 292         }
 293
 294         session_lock(session);
 295         if (!is_trigger_allowed_for_session(work_item->trigger, session)) {
 296                 goto error_dispose_session;
 297         }
 298
 299         cmd_ret = cmd_stop_trace(session);
 300         switch (cmd_ret) {
 301         case LTTNG_OK:
 302                 DBG("Successfully stopped session `%s` on behalf of trigger `%s`",
 303                                 session_name, get_trigger_name(work_item->trigger));
 304                 break;
 305         case LTTNG_ERR_TRACE_ALREADY_STOPPED:
 306                 DBG("Attempted to stop session `%s` on behalf of trigger `%s` but it was already stopped",
 307                                 session_name, get_trigger_name(work_item->trigger));
 308                 break;
 309         default:
 310                 WARN("Failed to stop session `%s` on behalf of trigger `%s`: %s",
 311                                 session_name, get_trigger_name(work_item->trigger),
 312                                 lttng_strerror(-cmd_ret));
 313                 break;
 314         }
 315
 316 error_dispose_session:
 317         session_unlock(session);
 318         session_put(session);
 319 error_unlock_list:
 320         session_unlock_list();
 321 end:
 322         return ret;
 323 }
 324
 325 static int action_executor_rotate_session_handler(struct action_executor *executor,
 326                 const struct action_work_item *work_item,
 327                 const struct lttng_action *action)
 328 {
 329         int ret = 0;
 330         const char *session_name;
 331         enum lttng_action_status action_status;
 332         struct ltt_session *session;
 333         enum lttng_error_code cmd_ret;
 334
 335         action_status = lttng_action_rotate_session_get_session_name(
 336                         action, &session_name);
 337         if (action_status != LTTNG_ACTION_STATUS_OK) {
 338                 ERR("Failed to get session name from `%s` action",
 339                                 get_action_name(action));
 340                 ret = -1;
 341                 goto end;
 342         }
 343
 344         session_lock_list();
 345         session = session_find_by_name(session_name);
 346         if (!session) {
 347                 DBG("Failed to find session `%s` by name while executing `%s` action of trigger `%s`",
 348                                 session_name, get_action_name(action),
 349                                 get_trigger_name(work_item->trigger));
 350                 goto error_unlock_list;
 351         }
 352
 353         session_lock(session);
 354         if (!is_trigger_allowed_for_session(work_item->trigger, session)) {
 355                 goto error_dispose_session;
 356         }
 357
 358         cmd_ret = cmd_rotate_session(session, NULL, false,
 359                         LTTNG_TRACE_CHUNK_COMMAND_TYPE_MOVE_TO_COMPLETED);
 360         switch (cmd_ret) {
 361         case LTTNG_OK:
 362                 DBG("Successfully started rotation of session `%s` on behalf of trigger `%s`",
 363                                 session_name, get_trigger_name(work_item->trigger));
 364                 break;
 365         case LTTNG_ERR_ROTATION_PENDING:
 366                 DBG("Attempted to start a rotation of session `%s` on behalf of trigger `%s` but a rotation is already ongoing",
 367                                 session_name, get_trigger_name(work_item->trigger));
 368                 break;
 369         case LTTNG_ERR_ROTATION_MULTIPLE_AFTER_STOP:
 370         case LTTNG_ERR_ROTATION_AFTER_STOP_CLEAR:
 371                 DBG("Attempted to start a rotation of session `%s` on behalf of trigger `%s` but a rotation has already been completed since the last stop or clear",
 372                                 session_name, get_trigger_name(work_item->trigger));
 373                 break;
 374         default:
 375                 WARN("Failed to start a rotation of session `%s` on behalf of trigger `%s`: %s",
 376                                 session_name, get_trigger_name(work_item->trigger),
 377                                 lttng_strerror(-cmd_ret));
 378                 break;
 379         }
 380
 381 error_dispose_session:
 382         session_unlock(session);
 383         session_put(session);
 384 error_unlock_list:
 385         session_unlock_list();
 386 end:
 387         return ret;
 388 }
 389
 390 static int action_executor_snapshot_session_handler(struct action_executor *executor,
 391                 const struct action_work_item *work_item,
 392                 const struct lttng_action *action)
 393 {
 394         int ret = 0;
 395         const char *session_name;
 396         enum lttng_action_status action_status;
 397         struct ltt_session *session;
 398         const struct lttng_snapshot_output default_snapshot_output = {
 399                 .max_size = UINT64_MAX,
 400         };
 401         const struct lttng_snapshot_output *snapshot_output =
 402                         &default_snapshot_output;
 403         enum lttng_error_code cmd_ret;
 404
 405         action_status = lttng_action_snapshot_session_get_session_name(
 406                         action, &session_name);
 407         if (action_status != LTTNG_ACTION_STATUS_OK) {
 408                 ERR("Failed to get session name from `%s` action",
 409                                 get_action_name(action));
 410                 ret = -1;
 411                 goto end;
 412         }
 413
 414         action_status = lttng_action_snapshot_session_get_output(
 415                         action, &snapshot_output);
 416         if (action_status != LTTNG_ACTION_STATUS_OK &&
 417                         action_status != LTTNG_ACTION_STATUS_UNSET) {
 418                 ERR("Failed to get output from `%s` action",
 419                                 get_action_name(action));
 420                 ret = -1;
 421                 goto end;
 422         }
 423
 424         session_lock_list();
 425         session = session_find_by_name(session_name);
 426         if (!session) {
 427                 DBG("Failed to find session `%s` by name while executing `%s` action of trigger `%p`",
 428                                 session_name, get_action_name(action),
 429                     work_item->trigger);
 430                 goto error_unlock_list;
 431         }
 432
 433
 434         session_lock(session);
 435         if (!is_trigger_allowed_for_session(work_item->trigger, session)) {
 436                 goto error_dispose_session;
 437         }
 438
 439         cmd_ret = cmd_snapshot_record(session, snapshot_output, 0);
 440         switch (cmd_ret) {
 441         case LTTNG_OK:
 442                 DBG("Successfully recorded snapshot of session `%s` on behalf of trigger `%s`",
 443                                 session_name, get_trigger_name(work_item->trigger));
 444                 break;
 445         default:
 446                 WARN("Failed to record snapshot of session `%s` on behalf of trigger `%s`: %s",
 447                                 session_name, get_trigger_name(work_item->trigger),
 448                                 lttng_strerror(-cmd_ret));
 449                 break;
 450         }
 451
 452 error_dispose_session:
 453         session_unlock(session);
 454         session_put(session);
 455 error_unlock_list:
 456         session_unlock_list();
 457 end:
 458         return ret;
 459 }
 460
 461 static int action_executor_group_handler(struct action_executor *executor,
 462                 const struct action_work_item *work_item,
 463                 const struct lttng_action *action_group)
 464 {
 465         int ret = 0;
 466         unsigned int i, count;
 467         enum lttng_action_status action_status;
 468
 469         action_status = lttng_action_group_get_count(action_group, &count);
 470         if (action_status != LTTNG_ACTION_STATUS_OK) {
 471                 /* Fatal error. */
 472                 ERR("Failed to get count of action in action group");
 473                 ret = -1;
 474                 goto end;
 475         }
 476
 477         DBG("Action group has %u action%s", count, count != 1 ? "s" : "");
 478         for (i = 0; i < count; i++) {
 479                 const struct lttng_action *action =
 480                                 lttng_action_group_get_at_index(
 481                                                 action_group, i);
 482
 483                 ret = action_executor_generic_handler(
 484                                 executor, work_item, action);
 485                 if (ret) {
 486                         ERR("Stopping the execution of the action group of trigger `%s` following a fatal error",
 487                                         get_trigger_name(work_item->trigger));
 488                         goto end;
 489                 }
 490         }
 491 end:
 492         return ret;
 493 }
 494
 495 static int action_executor_generic_handler(struct action_executor *executor,
 496                 const struct action_work_item *work_item,
 497                 const struct lttng_action *action)
 498 {
 499         const enum lttng_action_type action_type = lttng_action_get_type(action);
 500
 501         assert(action_type != LTTNG_ACTION_TYPE_UNKNOWN);
 502
 503         DBG("Executing action `%s` of trigger `%p` action work item %" PRIu64,
 504                         get_action_name(action),
 505                         get_trigger_name(work_item->trigger),
 506                         work_item->id);
 507
 508         return action_executors[action_type](
 509                         executor, work_item, action);
 510 }
 511
 512 static int action_work_item_execute(struct action_executor *executor,
 513                 struct action_work_item *work_item)
 514 {
 515         int ret;
 516         const struct lttng_action *action =
 517                         lttng_trigger_get_const_action(work_item->trigger);
 518
 519         DBG("Starting execution of action work item %" PRIu64 " of trigger `%s`",
 520                         work_item->id, get_trigger_name(work_item->trigger));
 521         ret = action_executor_generic_handler(executor, work_item, action);
 522         DBG("Completed execution of action work item %" PRIu64 " of trigger `%s`",
 523                         work_item->id, get_trigger_name(work_item->trigger));
 524         return ret;
 525 }
 526
 527 static void action_work_item_destroy(struct action_work_item *work_item)
 528 {
 529         lttng_trigger_put(work_item->trigger);
 530         lttng_evaluation_destroy(work_item->evaluation);
 531         notification_client_list_put(work_item->client_list);
 532         free(work_item);
 533 }
 534
 535 static void *action_executor_thread(void *_data)
 536 {
 537         struct action_executor *executor = _data;
 538
 539         assert(executor);
 540
 541         health_register(health_sessiond, HEALTH_SESSIOND_TYPE_ACTION_EXECUTOR);
 542
 543         rcu_register_thread();
 544         rcu_thread_online();
 545
 546         DBG("Entering work execution loop");
 547         pthread_mutex_lock(&executor->work.lock);
 548         while (!executor->should_quit) {
 549                 int ret;
 550                 struct action_work_item *work_item;
 551
 552                 health_code_update();
 553                 if (executor->work.pending_count == 0) {
 554                         health_poll_entry();
 555                         DBG("No work items enqueued, entering wait");
 556                         pthread_cond_wait(&executor->work.cond,
 557                                         &executor->work.lock);
 558                         DBG("Woke-up from wait");
 559                         health_poll_exit();
 560                         continue;
 561                 }
 562
 563                 /* Pop item from front of the list with work lock held. */
 564                 work_item = cds_list_first_entry(&executor->work.list,
 565                                 struct action_work_item, list_node);
 566                 cds_list_del(&work_item->list_node);
 567                 executor->work.pending_count--;
 568
 569                 /*
 570                  * Work can be performed without holding the work lock,
 571                  * allowing new items to be queued.
 572                  */
 573                 pthread_mutex_unlock(&executor->work.lock);
 574                 ret = action_work_item_execute(executor, work_item);
 575                 action_work_item_destroy(work_item);
 576                 if (ret) {
 577                         /* Fatal error. */
 578                         break;
 579                 }
 580
 581                 health_code_update();
 582                 pthread_mutex_lock(&executor->work.lock);
 583         }
 584
 585         if (executor->should_quit) {
 586                 pthread_mutex_unlock(&executor->work.lock);
 587         }
 588         DBG("Left work execution loop");
 589
 590         health_code_update();
 591
 592         rcu_thread_offline();
 593         rcu_unregister_thread();
 594         health_unregister(health_sessiond);
 595
 596         return NULL;
 597 }
 598
 599 static bool shutdown_action_executor_thread(void *_data)
 600 {
 601         struct action_executor *executor = _data;
 602
 603         executor->should_quit = true;
 604         pthread_cond_signal(&executor->work.cond);
 605         return true;
 606 }
 607
 608 static void clean_up_action_executor_thread(void *_data)
 609 {
 610         struct action_executor *executor = _data;
 611
 612         assert(cds_list_empty(&executor->work.list));
 613
 614         pthread_mutex_destroy(&executor->work.lock);
 615         pthread_cond_destroy(&executor->work.cond);
 616         free(executor);
 617 }
 618
 619 struct action_executor *action_executor_create(
 620                 struct notification_thread_handle *handle)
 621 {
 622         struct action_executor *executor = zmalloc(sizeof(*executor));
 623
 624         if (!executor) {
 625                 goto end;
 626         }
 627
 628         CDS_INIT_LIST_HEAD(&executor->work.list);
 629         pthread_cond_init(&executor->work.cond, NULL);
 630         pthread_mutex_init(&executor->work.lock, NULL);
 631         executor->notification_thread_handle = handle;
 632
 633         executor->thread = lttng_thread_create(THREAD_NAME,
 634                         action_executor_thread, shutdown_action_executor_thread,
 635                         clean_up_action_executor_thread, executor);
 636 end:
 637         return executor;
 638 }
 639
 640 void action_executor_destroy(struct action_executor *executor)
 641 {
 642         struct action_work_item *work_item, *tmp;
 643
 644         /* TODO Wait for work list to drain? */
 645         lttng_thread_shutdown(executor->thread);
 646         pthread_mutex_lock(&executor->work.lock);
 647         if (executor->work.pending_count != 0) {
 648                 WARN("%" PRIu64
 649                         " trigger action%s still queued for execution and will be discarded",
 650                                 executor->work.pending_count,
 651                                 executor->work.pending_count == 1 ? " is" :
 652                                                                     "s are");
 653         }
 654
 655         cds_list_for_each_entry_safe (
 656                         work_item, tmp, &executor->work.list, list_node) {
 657                 WARN("Discarding action work item %" PRIu64
 658                                 " associated to trigger `%s`",
 659                                 work_item->id, get_trigger_name(work_item->trigger));
 660                 cds_list_del(&work_item->list_node);
 661                 action_work_item_destroy(work_item);
 662         }
 663         pthread_mutex_unlock(&executor->work.lock);
 664         lttng_thread_put(executor->thread);
 665 }
 666
 667 /* RCU read-lock must be held by the caller. */
 668 enum action_executor_status action_executor_enqueue(
 669                 struct action_executor *executor,
 670                 struct lttng_trigger *trigger,
 671                 struct lttng_evaluation *evaluation,
 672                 const struct lttng_credentials *object_creds,
 673                 struct notification_client_list *client_list)
 674 {
 675         enum action_executor_status executor_status = ACTION_EXECUTOR_STATUS_OK;
 676         const uint64_t work_item_id = executor->next_work_item_id++;
 677         struct action_work_item *work_item;
 678         bool signal = false;
 679
 680         pthread_mutex_lock(&executor->work.lock);
 681         /* Check for queue overflow. */
 682         if (executor->work.pending_count >= MAX_QUEUED_WORK_COUNT) {
 683                 /* Most likely spammy, remove if it is the case. */
 684                 DBG("Refusing to enqueue action for trigger `%s` as work item %" PRIu64
 685                         " (overflow)", get_trigger_name(trigger), work_item_id);
 686                 executor_status = ACTION_EXECUTOR_STATUS_OVERFLOW;
 687                 goto error_unlock;
 688         }
 689
 690         work_item = zmalloc(sizeof(*work_item));
 691         if (!work_item) {
 692                 PERROR("Failed to allocate action executor work item on behalf of trigger `%p`",
 693                                 get_trigger_name(trigger));
 694                 executor_status = ACTION_EXECUTOR_STATUS_ERROR;
 695                 goto error_unlock;
 696         }
 697
 698         lttng_trigger_get(trigger);
 699         if (client_list) {
 700                 const bool reference_acquired =
 701                                 notification_client_list_get(client_list);
 702
 703                 assert(reference_acquired);
 704         }
 705
 706         *work_item = (typeof(*work_item)){
 707                         .id = work_item_id,
 708                         .trigger = trigger,
 709                         /* Ownership transferred to the work item. */
 710                         .evaluation = evaluation,
 711                         .object_creds = {
 712                                 .is_set = !!object_creds,
 713                                 .value = object_creds ? *object_creds :
 714                                         (typeof(work_item->object_creds.value)) {},
 715                         },
 716                         .client_list = client_list,
 717                         .list_node = CDS_LIST_HEAD_INIT(work_item->list_node),
 718         };
 719
 720         evaluation = NULL;
 721         cds_list_add_tail(&work_item->list_node, &executor->work.list);
 722         executor->work.pending_count++;
 723         DBG("Enqueued action for trigger `%p` as work item %" PRIu64,
 724                         get_trigger_name(trigger), work_item_id);
 725         signal = true;
 726
 727 error_unlock:
 728         pthread_mutex_unlock(&executor->work.lock);
 729         if (signal) {
 730                 pthread_cond_signal(&executor->work.cond);
 731         }
 732
 733         lttng_evaluation_destroy(evaluation);
 734         return executor_status;
 735 }