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