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/condition/event-rule-internal.h>
  26 #include <lttng/lttng-error.h>
  27 #include <lttng/trigger/trigger-internal.h>
  28 #include <pthread.h>
  29 #include <stdbool.h>
  30 #include <stddef.h>
  31 #include <urcu/list.h>
  32
  33 #define THREAD_NAME "Action Executor"
  34 #define MAX_QUEUED_WORK_COUNT 8192
  35
  36 struct action_work_item {
  37         uint64_t id;
  38         struct lttng_trigger *trigger;
  39         struct lttng_evaluation *evaluation;
  40         struct notification_client_list *client_list;
  41         LTTNG_OPTIONAL(struct lttng_credentials) object_creds;
  42         struct cds_list_head list_node;
  43 };
  44
  45 struct action_executor {
  46         struct lttng_thread *thread;
  47         struct notification_thread_handle *notification_thread_handle;
  48         struct {
  49                 uint64_t pending_count;
  50                 struct cds_list_head list;
  51                 pthread_cond_t cond;
  52                 pthread_mutex_t lock;
  53         } work;
  54         bool should_quit;
  55         uint64_t next_work_item_id;
  56 };
  57
  58 /*
  59  * Only return non-zero on a fatal error that should shut down the action
  60  * executor.
  61  */
  62 typedef int (*action_executor_handler)(struct action_executor *executor,
  63                 const struct action_work_item *,
  64                 const struct lttng_action *action);
  65
  66 static int action_executor_notify_handler(struct action_executor *executor,
  67                 const struct action_work_item *,
  68                 const struct lttng_action *);
  69 static int action_executor_start_session_handler(struct action_executor *executor,
  70                 const struct action_work_item *,
  71                 const struct lttng_action *);
  72 static int action_executor_stop_session_handler(struct action_executor *executor,
  73                 const struct action_work_item *,
  74                 const struct lttng_action *);
  75 static int action_executor_rotate_session_handler(struct action_executor *executor,
  76                 const struct action_work_item *,
  77                 const struct lttng_action *);
  78 static int action_executor_snapshot_session_handler(struct action_executor *executor,
  79                 const struct action_work_item *,
  80                 const struct lttng_action *);
  81 static int action_executor_group_handler(struct action_executor *executor,
  82                 const struct action_work_item *,
  83                 const struct lttng_action *);
  84 static int action_executor_generic_handler(struct action_executor *executor,
  85                 const struct action_work_item *,
  86                 const struct lttng_action *);
  87
  88 static const action_executor_handler action_executors[] = {
  89         [LTTNG_ACTION_TYPE_NOTIFY] = action_executor_notify_handler,
  90         [LTTNG_ACTION_TYPE_START_SESSION] = action_executor_start_session_handler,
  91         [LTTNG_ACTION_TYPE_STOP_SESSION] = action_executor_stop_session_handler,
  92         [LTTNG_ACTION_TYPE_ROTATE_SESSION] = action_executor_rotate_session_handler,
  93         [LTTNG_ACTION_TYPE_SNAPSHOT_SESSION] = action_executor_snapshot_session_handler,
  94         [LTTNG_ACTION_TYPE_GROUP] = action_executor_group_handler,
  95 };
  96
  97 static const char *action_type_names[] = {
  98         [LTTNG_ACTION_TYPE_NOTIFY] = "Notify",
  99         [LTTNG_ACTION_TYPE_START_SESSION] = "Start session",
 100         [LTTNG_ACTION_TYPE_STOP_SESSION] = "Stop session",
 101         [LTTNG_ACTION_TYPE_ROTATE_SESSION] = "Rotate session",
 102         [LTTNG_ACTION_TYPE_SNAPSHOT_SESSION] = "Snapshot session",
 103         [LTTNG_ACTION_TYPE_GROUP] = "Group",
 104 };
 105
 106 static const char *get_action_name(const struct lttng_action *action)
 107 {
 108         const enum lttng_action_type action_type = lttng_action_get_type(action);
 109
 110         assert(action_type != LTTNG_ACTION_TYPE_UNKNOWN);
 111
 112         return action_type_names[action_type];
 113 }
 114
 115 /* Check if this trigger allowed to interect with a given session. */
 116 static bool is_trigger_allowed_for_session(const struct lttng_trigger *trigger,
 117                 struct ltt_session *session)
 118 {
 119         bool is_allowed = false;
 120         const struct lttng_credentials session_creds = {
 121                 .uid = LTTNG_OPTIONAL_INIT_VALUE(session->uid),
 122                 .gid = LTTNG_OPTIONAL_INIT_VALUE(session->gid),
 123         };
 124         /* Can never be NULL. */
 125         const struct lttng_credentials *trigger_creds =
 126                         lttng_trigger_get_credentials(trigger);
 127
 128         is_allowed = (lttng_credentials_is_equal_uid(trigger_creds, &session_creds)) ||
 129                         (lttng_credentials_get_uid(trigger_creds) == 0);
 130         if (!is_allowed) {
 131                 WARN("Trigger is not allowed to interact with session `%s`: session uid = %ld, session gid = %ld, trigger uid = %ld",
 132                                 session->name,
 133                                 (long int) session->uid,
 134                                 (long int) session->gid,
 135                                 (long int) lttng_credentials_get_uid(trigger_creds));
 136         }
 137
 138         return is_allowed;
 139 }
 140
 141 static const char *get_trigger_name(const struct lttng_trigger *trigger)
 142 {
 143         const char *trigger_name;
 144         enum lttng_trigger_status trigger_status;
 145
 146         trigger_status = lttng_trigger_get_name(trigger, &trigger_name);
 147         assert(trigger_status == LTTNG_TRIGGER_STATUS_OK);
 148
 149         return trigger_name;
 150 }
 151
 152 static int client_handle_transmission_status(
 153                 struct notification_client *client,
 154                 enum client_transmission_status status,
 155                 void *user_data)
 156 {
 157         int ret = 0;
 158         struct action_executor *executor = user_data;
 159         bool update_communication = true;
 160
 161         switch (status) {
 162         case CLIENT_TRANSMISSION_STATUS_COMPLETE:
 163                 DBG("Successfully sent full notification to client, client_id = %" PRIu64,
 164                                 client->id);
 165                 update_communication = false;
 166                 break;
 167         case CLIENT_TRANSMISSION_STATUS_QUEUED:
 168                 DBG("Queued notification in client outgoing buffer, client_id = %" PRIu64,
 169                                 client->id);
 170                 break;
 171         case CLIENT_TRANSMISSION_STATUS_FAIL:
 172                 DBG("Communication error occurred while sending notification to client, client_id = %" PRIu64,
 173                                 client->id);
 174                 break;
 175         default:
 176                 ERR("Fatal error encoutered while sending notification to client, client_id = %" PRIu64,
 177                                 client->id);
 178                 ret = -1;
 179                 goto end;
 180         }
 181
 182         if (!update_communication) {
 183                 goto end;
 184         }
 185
 186         /* Safe to read client's id without locking as it is immutable. */
 187         ret = notification_thread_client_communication_update(
 188                         executor->notification_thread_handle, client->id,
 189                         status);
 190 end:
 191         return ret;
 192 }
 193
 194 static int action_executor_notify_handler(struct action_executor *executor,
 195                 const struct action_work_item *work_item,
 196                 const struct lttng_action *action)
 197 {
 198         return notification_client_list_send_evaluation(work_item->client_list,
 199                         lttng_trigger_get_const_condition(work_item->trigger),
 200                         work_item->evaluation,
 201                         lttng_trigger_get_credentials(work_item->trigger),
 202                         work_item->object_creds.is_set ?
 203                                         &(work_item->object_creds.value) :
 204                                         NULL,
 205                         client_handle_transmission_status, executor);
 206 }
 207
 208 static int action_executor_start_session_handler(struct action_executor *executor,
 209                 const struct action_work_item *work_item,
 210                 const struct lttng_action *action)
 211 {
 212         int ret = 0;
 213         const char *session_name;
 214         enum lttng_action_status action_status;
 215         struct ltt_session *session;
 216         enum lttng_error_code cmd_ret;
 217
 218         action_status = lttng_action_start_session_get_session_name(
 219                         action, &session_name);
 220         if (action_status != LTTNG_ACTION_STATUS_OK) {
 221                 ERR("Failed to get session name from `%s` action",
 222                                 get_action_name(action));
 223                 ret = -1;
 224                 goto end;
 225         }
 226
 227         session_lock_list();
 228         session = session_find_by_name(session_name);
 229         if (!session) {
 230                 DBG("Failed to find session `%s` by name while executing `%s` action of trigger `%s`",
 231                                 session_name, get_action_name(action),
 232                                 get_trigger_name(work_item->trigger));
 233                 goto error_unlock_list;
 234         }
 235
 236         session_lock(session);
 237         if (!is_trigger_allowed_for_session(work_item->trigger, session)) {
 238                 goto error_dispose_session;
 239         }
 240
 241         cmd_ret = cmd_start_trace(session);
 242         switch (cmd_ret) {
 243         case LTTNG_OK:
 244                 DBG("Successfully started session `%s` on behalf of trigger `%s`",
 245                                 session_name, get_trigger_name(work_item->trigger));
 246                 break;
 247         case LTTNG_ERR_TRACE_ALREADY_STARTED:
 248                 DBG("Attempted to start session `%s` on behalf of trigger `%s` but it was already started",
 249                                 session_name, get_trigger_name(work_item->trigger));
 250                 break;
 251         default:
 252                 WARN("Failed to start session `%s` on behalf of trigger `%s`: %s",
 253                                 session_name, get_trigger_name(work_item->trigger),
 254                                 lttng_strerror(-cmd_ret));
 255                 break;
 256         }
 257
 258 error_dispose_session:
 259         session_unlock(session);
 260         session_put(session);
 261 error_unlock_list:
 262         session_unlock_list();
 263 end:
 264         return ret;
 265 }
 266
 267 static int action_executor_stop_session_handler(struct action_executor *executor,
 268                 const struct action_work_item *work_item,
 269                 const struct lttng_action *action)
 270 {
 271         int ret = 0;
 272         const char *session_name;
 273         enum lttng_action_status action_status;
 274         struct ltt_session *session;
 275         enum lttng_error_code cmd_ret;
 276
 277         action_status = lttng_action_stop_session_get_session_name(
 278                         action, &session_name);
 279         if (action_status != LTTNG_ACTION_STATUS_OK) {
 280                 ERR("Failed to get session name from `%s` action",
 281                                 get_action_name(action));
 282                 ret = -1;
 283                 goto end;
 284         }
 285
 286         session_lock_list();
 287         session = session_find_by_name(session_name);
 288         if (!session) {
 289                 DBG("Failed to find session `%s` by name while executing `%s` action of trigger `%s`",
 290                                 session_name, get_action_name(action),
 291                                 get_trigger_name(work_item->trigger));
 292                 goto error_unlock_list;
 293         }
 294
 295         session_lock(session);
 296         if (!is_trigger_allowed_for_session(work_item->trigger, session)) {
 297                 goto error_dispose_session;
 298         }
 299
 300         cmd_ret = cmd_stop_trace(session);
 301         switch (cmd_ret) {
 302         case LTTNG_OK:
 303                 DBG("Successfully stopped session `%s` on behalf of trigger `%s`",
 304                                 session_name, get_trigger_name(work_item->trigger));
 305                 break;
 306         case LTTNG_ERR_TRACE_ALREADY_STOPPED:
 307                 DBG("Attempted to stop session `%s` on behalf of trigger `%s` but it was already stopped",
 308                                 session_name, get_trigger_name(work_item->trigger));
 309                 break;
 310         default:
 311                 WARN("Failed to stop session `%s` on behalf of trigger `%s`: %s",
 312                                 session_name, get_trigger_name(work_item->trigger),
 313                                 lttng_strerror(-cmd_ret));
 314                 break;
 315         }
 316
 317 error_dispose_session:
 318         session_unlock(session);
 319         session_put(session);
 320 error_unlock_list:
 321         session_unlock_list();
 322 end:
 323         return ret;
 324 }
 325
 326 static int action_executor_rotate_session_handler(struct action_executor *executor,
 327                 const struct action_work_item *work_item,
 328                 const struct lttng_action *action)
 329 {
 330         int ret = 0;
 331         const char *session_name;
 332         enum lttng_action_status action_status;
 333         struct ltt_session *session;
 334         enum lttng_error_code cmd_ret;
 335
 336         action_status = lttng_action_rotate_session_get_session_name(
 337                         action, &session_name);
 338         if (action_status != LTTNG_ACTION_STATUS_OK) {
 339                 ERR("Failed to get session name from `%s` action",
 340                                 get_action_name(action));
 341                 ret = -1;
 342                 goto end;
 343         }
 344
 345         session_lock_list();
 346         session = session_find_by_name(session_name);
 347         if (!session) {
 348                 DBG("Failed to find session `%s` by name while executing `%s` action of trigger `%s`",
 349                                 session_name, get_action_name(action),
 350                                 get_trigger_name(work_item->trigger));
 351                 goto error_unlock_list;
 352         }
 353
 354         session_lock(session);
 355         if (!is_trigger_allowed_for_session(work_item->trigger, session)) {
 356                 goto error_dispose_session;
 357         }
 358
 359         cmd_ret = cmd_rotate_session(session, NULL, false,
 360                         LTTNG_TRACE_CHUNK_COMMAND_TYPE_MOVE_TO_COMPLETED);
 361         switch (cmd_ret) {
 362         case LTTNG_OK:
 363                 DBG("Successfully started rotation of session `%s` on behalf of trigger `%s`",
 364                                 session_name, get_trigger_name(work_item->trigger));
 365                 break;
 366         case LTTNG_ERR_ROTATION_PENDING:
 367                 DBG("Attempted to start a rotation of session `%s` on behalf of trigger `%s` but a rotation is already ongoing",
 368                                 session_name, get_trigger_name(work_item->trigger));
 369                 break;
 370         case LTTNG_ERR_ROTATION_MULTIPLE_AFTER_STOP:
 371         case LTTNG_ERR_ROTATION_AFTER_STOP_CLEAR:
 372                 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",
 373                                 session_name, get_trigger_name(work_item->trigger));
 374                 break;
 375         default:
 376                 WARN("Failed to start a rotation of session `%s` on behalf of trigger `%s`: %s",
 377                                 session_name, get_trigger_name(work_item->trigger),
 378                                 lttng_strerror(-cmd_ret));
 379                 break;
 380         }
 381
 382 error_dispose_session:
 383         session_unlock(session);
 384         session_put(session);
 385 error_unlock_list:
 386         session_unlock_list();
 387 end:
 388         return ret;
 389 }
 390
 391 static int action_executor_snapshot_session_handler(struct action_executor *executor,
 392                 const struct action_work_item *work_item,
 393                 const struct lttng_action *action)
 394 {
 395         int ret = 0;
 396         const char *session_name;
 397         enum lttng_action_status action_status;
 398         struct ltt_session *session;
 399         const struct lttng_snapshot_output default_snapshot_output = {
 400                 .max_size = UINT64_MAX,
 401         };
 402         const struct lttng_snapshot_output *snapshot_output =
 403                         &default_snapshot_output;
 404         enum lttng_error_code cmd_ret;
 405
 406         action_status = lttng_action_snapshot_session_get_session_name(
 407                         action, &session_name);
 408         if (action_status != LTTNG_ACTION_STATUS_OK) {
 409                 ERR("Failed to get session name from `%s` action",
 410                                 get_action_name(action));
 411                 ret = -1;
 412                 goto end;
 413         }
 414
 415         action_status = lttng_action_snapshot_session_get_output(
 416                         action, &snapshot_output);
 417         if (action_status != LTTNG_ACTION_STATUS_OK &&
 418                         action_status != LTTNG_ACTION_STATUS_UNSET) {
 419                 ERR("Failed to get output from `%s` action",
 420                                 get_action_name(action));
 421                 ret = -1;
 422                 goto end;
 423         }
 424
 425         session_lock_list();
 426         session = session_find_by_name(session_name);
 427         if (!session) {
 428                 DBG("Failed to find session `%s` by name while executing `%s` action of trigger `%p`",
 429                                 session_name, get_action_name(action),
 430                     work_item->trigger);
 431                 goto error_unlock_list;
 432         }
 433
 434
 435         session_lock(session);
 436         if (!is_trigger_allowed_for_session(work_item->trigger, session)) {
 437                 goto error_dispose_session;
 438         }
 439
 440         cmd_ret = cmd_snapshot_record(session, snapshot_output, 0);
 441         switch (cmd_ret) {
 442         case LTTNG_OK:
 443                 DBG("Successfully recorded snapshot of session `%s` on behalf of trigger `%s`",
 444                                 session_name, get_trigger_name(work_item->trigger));
 445                 break;
 446         default:
 447                 WARN("Failed to record snapshot of session `%s` on behalf of trigger `%s`: %s",
 448                                 session_name, get_trigger_name(work_item->trigger),
 449                                 lttng_strerror(-cmd_ret));
 450                 break;
 451         }
 452
 453 error_dispose_session:
 454         session_unlock(session);
 455         session_put(session);
 456 error_unlock_list:
 457         session_unlock_list();
 458 end:
 459         return ret;
 460 }
 461
 462 static int action_executor_group_handler(struct action_executor *executor,
 463                 const struct action_work_item *work_item,
 464                 const struct lttng_action *action_group)
 465 {
 466         int ret = 0;
 467         unsigned int i, count;
 468         enum lttng_action_status action_status;
 469
 470         action_status = lttng_action_group_get_count(action_group, &count);
 471         if (action_status != LTTNG_ACTION_STATUS_OK) {
 472                 /* Fatal error. */
 473                 ERR("Failed to get count of action in action group");
 474                 ret = -1;
 475                 goto end;
 476         }
 477
 478         DBG("Action group has %u action%s", count, count != 1 ? "s" : "");
 479         for (i = 0; i < count; i++) {
 480                 const struct lttng_action *action =
 481                                 lttng_action_group_get_at_index(
 482                                                 action_group, i);
 483
 484                 ret = action_executor_generic_handler(
 485                                 executor, work_item, action);
 486                 if (ret) {
 487                         ERR("Stopping the execution of the action group of trigger `%s` following a fatal error",
 488                                         get_trigger_name(work_item->trigger));
 489                         goto end;
 490                 }
 491         }
 492 end:
 493         return ret;
 494 }
 495
 496 static int action_executor_generic_handler(struct action_executor *executor,
 497                 const struct action_work_item *work_item,
 498                 const struct lttng_action *action)
 499 {
 500         const enum lttng_action_type action_type = lttng_action_get_type(action);
 501
 502         assert(action_type != LTTNG_ACTION_TYPE_UNKNOWN);
 503
 504         DBG("Executing action `%s` of trigger `%s` action work item %" PRIu64,
 505                         get_action_name(action),
 506                         get_trigger_name(work_item->trigger),
 507                         work_item->id);
 508
 509         return action_executors[action_type](
 510                         executor, work_item, action);
 511 }
 512
 513 static int action_work_item_execute(struct action_executor *executor,
 514                 struct action_work_item *work_item)
 515 {
 516         int ret;
 517         const struct lttng_action *action =
 518                         lttng_trigger_get_const_action(work_item->trigger);
 519
 520         DBG("Starting execution of action work item %" PRIu64 " of trigger `%s`",
 521                         work_item->id, get_trigger_name(work_item->trigger));
 522         ret = action_executor_generic_handler(executor, work_item, action);
 523         DBG("Completed execution of action work item %" PRIu64 " of trigger `%s`",
 524                         work_item->id, get_trigger_name(work_item->trigger));
 525         return ret;
 526 }
 527
 528 static void action_work_item_destroy(struct action_work_item *work_item)
 529 {
 530         lttng_trigger_put(work_item->trigger);
 531         lttng_evaluation_destroy(work_item->evaluation);
 532         notification_client_list_put(work_item->client_list);
 533         free(work_item);
 534 }
 535
 536 static void *action_executor_thread(void *_data)
 537 {
 538         struct action_executor *executor = _data;
 539
 540         assert(executor);
 541
 542         health_register(health_sessiond, HEALTH_SESSIOND_TYPE_ACTION_EXECUTOR);
 543
 544         rcu_register_thread();
 545         rcu_thread_online();
 546
 547         DBG("Entering work execution loop");
 548         pthread_mutex_lock(&executor->work.lock);
 549         while (!executor->should_quit) {
 550                 int ret;
 551                 struct action_work_item *work_item;
 552
 553                 health_code_update();
 554                 if (executor->work.pending_count == 0) {
 555                         health_poll_entry();
 556                         DBG("No work items enqueued, entering wait");
 557                         pthread_cond_wait(&executor->work.cond,
 558                                         &executor->work.lock);
 559                         DBG("Woke-up from wait");
 560                         health_poll_exit();
 561                         continue;
 562                 }
 563
 564                 /* Pop item from front of the list with work lock held. */
 565                 work_item = cds_list_first_entry(&executor->work.list,
 566                                 struct action_work_item, list_node);
 567                 cds_list_del(&work_item->list_node);
 568                 executor->work.pending_count--;
 569
 570                 /*
 571                  * Work can be performed without holding the work lock,
 572                  * allowing new items to be queued.
 573                  */
 574                 pthread_mutex_unlock(&executor->work.lock);
 575                 ret = action_work_item_execute(executor, work_item);
 576                 action_work_item_destroy(work_item);
 577                 if (ret) {
 578                         /* Fatal error. */
 579                         break;
 580                 }
 581
 582                 health_code_update();
 583                 pthread_mutex_lock(&executor->work.lock);
 584         }
 585
 586         if (executor->should_quit) {
 587                 pthread_mutex_unlock(&executor->work.lock);
 588         }
 589         DBG("Left work execution loop");
 590
 591         health_code_update();
 592
 593         rcu_thread_offline();
 594         rcu_unregister_thread();
 595         health_unregister(health_sessiond);
 596
 597         return NULL;
 598 }
 599
 600 static bool shutdown_action_executor_thread(void *_data)
 601 {
 602         struct action_executor *executor = _data;
 603
 604         pthread_mutex_lock(&executor->work.lock);
 605         executor->should_quit = true;
 606         pthread_cond_signal(&executor->work.cond);
 607         pthread_mutex_unlock(&executor->work.lock);
 608         return true;
 609 }
 610
 611 static void clean_up_action_executor_thread(void *_data)
 612 {
 613         struct action_executor *executor = _data;
 614
 615         assert(cds_list_empty(&executor->work.list));
 616
 617         pthread_mutex_destroy(&executor->work.lock);
 618         pthread_cond_destroy(&executor->work.cond);
 619         free(executor);
 620 }
 621
 622 struct action_executor *action_executor_create(
 623                 struct notification_thread_handle *handle)
 624 {
 625         struct action_executor *executor = zmalloc(sizeof(*executor));
 626
 627         if (!executor) {
 628                 goto end;
 629         }
 630
 631         CDS_INIT_LIST_HEAD(&executor->work.list);
 632         pthread_cond_init(&executor->work.cond, NULL);
 633         pthread_mutex_init(&executor->work.lock, NULL);
 634         executor->notification_thread_handle = handle;
 635
 636         executor->thread = lttng_thread_create(THREAD_NAME,
 637                         action_executor_thread, shutdown_action_executor_thread,
 638                         clean_up_action_executor_thread, executor);
 639 end:
 640         return executor;
 641 }
 642
 643 void action_executor_destroy(struct action_executor *executor)
 644 {
 645         struct action_work_item *work_item, *tmp;
 646
 647         /* TODO Wait for work list to drain? */
 648         lttng_thread_shutdown(executor->thread);
 649         pthread_mutex_lock(&executor->work.lock);
 650         if (executor->work.pending_count != 0) {
 651                 WARN("%" PRIu64
 652                         " trigger action%s still queued for execution and will be discarded",
 653                                 executor->work.pending_count,
 654                                 executor->work.pending_count == 1 ? " is" :
 655                                                                     "s are");
 656         }
 657
 658         cds_list_for_each_entry_safe (
 659                         work_item, tmp, &executor->work.list, list_node) {
 660                 WARN("Discarding action work item %" PRIu64
 661                                 " associated to trigger `%s`",
 662                                 work_item->id, get_trigger_name(work_item->trigger));
 663                 cds_list_del(&work_item->list_node);
 664                 action_work_item_destroy(work_item);
 665         }
 666         pthread_mutex_unlock(&executor->work.lock);
 667         lttng_thread_put(executor->thread);
 668 }
 669
 670 /* RCU read-lock must be held by the caller. */
 671 enum action_executor_status action_executor_enqueue(
 672                 struct action_executor *executor,
 673                 struct lttng_trigger *trigger,
 674                 struct lttng_evaluation *evaluation,
 675                 const struct lttng_credentials *object_creds,
 676                 struct notification_client_list *client_list)
 677 {
 678         enum action_executor_status executor_status = ACTION_EXECUTOR_STATUS_OK;
 679         const uint64_t work_item_id = executor->next_work_item_id++;
 680         struct action_work_item *work_item;
 681         bool signal = false;
 682
 683         pthread_mutex_lock(&executor->work.lock);
 684         /* Check for queue overflow. */
 685         if (executor->work.pending_count >= MAX_QUEUED_WORK_COUNT) {
 686                 /* Most likely spammy, remove if it is the case. */
 687                 DBG("Refusing to enqueue action for trigger `%s` as work item %" PRIu64
 688                         " (overflow)", get_trigger_name(trigger), work_item_id);
 689                 executor_status = ACTION_EXECUTOR_STATUS_OVERFLOW;
 690                 goto error_unlock;
 691         }
 692
 693         work_item = zmalloc(sizeof(*work_item));
 694         if (!work_item) {
 695                 PERROR("Failed to allocate action executor work item on behalf of trigger `%s`",
 696                                 get_trigger_name(trigger));
 697                 executor_status = ACTION_EXECUTOR_STATUS_ERROR;
 698                 goto error_unlock;
 699         }
 700
 701         lttng_trigger_get(trigger);
 702         if (client_list) {
 703                 const bool reference_acquired =
 704                                 notification_client_list_get(client_list);
 705
 706                 assert(reference_acquired);
 707         }
 708
 709         *work_item = (typeof(*work_item)){
 710                         .id = work_item_id,
 711                         .trigger = trigger,
 712                         /* Ownership transferred to the work item. */
 713                         .evaluation = evaluation,
 714                         .object_creds = {
 715                                 .is_set = !!object_creds,
 716                                 .value = object_creds ? *object_creds :
 717                                         (typeof(work_item->object_creds.value)) {},
 718                         },
 719                         .client_list = client_list,
 720                         .list_node = CDS_LIST_HEAD_INIT(work_item->list_node),
 721         };
 722
 723         evaluation = NULL;
 724         cds_list_add_tail(&work_item->list_node, &executor->work.list);
 725         executor->work.pending_count++;
 726         DBG("Enqueued action for trigger `%s` as work item #%" PRIu64,
 727                         get_trigger_name(trigger), work_item_id);
 728         signal = true;
 729
 730 error_unlock:
 731         if (signal) {
 732                 pthread_cond_signal(&executor->work.cond);
 733         }
 734         pthread_mutex_unlock(&executor->work.lock);
 735
 736         lttng_evaluation_destroy(evaluation);
 737         return executor_status;
 738 }