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