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_incr_value_handler(struct action_executor *executor,
  71                 const struct action_work_item *,
  72                 const struct lttng_action *);
  73 static int action_executor_start_session_handler(struct action_executor *executor,
  74                 const struct action_work_item *,
  75                 const struct lttng_action *);
  76 static int action_executor_stop_session_handler(struct action_executor *executor,
  77                 const struct action_work_item *,
  78                 const struct lttng_action *);
  79 static int action_executor_rotate_session_handler(struct action_executor *executor,
  80                 const struct action_work_item *,
  81                 const struct lttng_action *);
  82 static int action_executor_snapshot_session_handler(struct action_executor *executor,
  83                 const struct action_work_item *,
  84                 const struct lttng_action *);
  85 static int action_executor_group_handler(struct action_executor *executor,
  86                 const struct action_work_item *,
  87                 const struct lttng_action *);
  88 static int action_executor_generic_handler(struct action_executor *executor,
  89                 const struct action_work_item *,
  90                 const struct lttng_action *);
  91
  92 static const action_executor_handler action_executors[] = {
  93         [LTTNG_ACTION_TYPE_NOTIFY] = action_executor_notify_handler,
  94         [LTTNG_ACTION_TYPE_INCREMENT_VALUE] = action_executor_incr_value_handler,
  95         [LTTNG_ACTION_TYPE_START_SESSION] = action_executor_start_session_handler,
  96         [LTTNG_ACTION_TYPE_STOP_SESSION] = action_executor_stop_session_handler,
  97         [LTTNG_ACTION_TYPE_ROTATE_SESSION] = action_executor_rotate_session_handler,
  98         [LTTNG_ACTION_TYPE_SNAPSHOT_SESSION] = action_executor_snapshot_session_handler,
  99         [LTTNG_ACTION_TYPE_GROUP] = action_executor_group_handler,
 100 };
 101
 102
 103 static const char *get_action_name(const struct lttng_action *action)
 104 {
 105         const enum lttng_action_type action_type = lttng_action_get_type(action);
 106
 107         assert(action_type != LTTNG_ACTION_TYPE_UNKNOWN);
 108
 109         return lttng_action_type_string(action_type);
 110 }
 111
 112 /* Check if this trigger allowed to interect with a given session. */
 113 static bool is_trigger_allowed_for_session(const struct lttng_trigger *trigger,
 114                 struct ltt_session *session)
 115 {
 116         bool is_allowed = false;
 117         const struct lttng_credentials session_creds = {
 118                 .uid = LTTNG_OPTIONAL_INIT_VALUE(session->uid),
 119                 .gid = LTTNG_OPTIONAL_INIT_VALUE(session->gid),
 120         };
 121         /* Can never be NULL. */
 122         const struct lttng_credentials *trigger_creds =
 123                         lttng_trigger_get_credentials(trigger);
 124
 125         is_allowed = (lttng_credentials_is_equal_uid(trigger_creds, &session_creds)) ||
 126                         (lttng_credentials_get_uid(trigger_creds) == 0);
 127         if (!is_allowed) {
 128                 WARN("Trigger is not allowed to interact with session `%s`: session uid = %ld, session gid = %ld, trigger uid = %ld",
 129                                 session->name,
 130                                 (long int) session->uid,
 131                                 (long int) session->gid,
 132                                 (long int) lttng_credentials_get_uid(trigger_creds));
 133         }
 134
 135         return is_allowed;
 136 }
 137
 138 static const char *get_trigger_name(const struct lttng_trigger *trigger)
 139 {
 140         const char *trigger_name;
 141         enum lttng_trigger_status trigger_status;
 142
 143         trigger_status = lttng_trigger_get_name(trigger, &trigger_name);
 144         assert(trigger_status == LTTNG_TRIGGER_STATUS_OK);
 145
 146         return trigger_name;
 147 }
 148
 149 static int client_handle_transmission_status(
 150                 struct notification_client *client,
 151                 enum client_transmission_status status,
 152                 void *user_data)
 153 {
 154         int ret = 0;
 155         struct action_executor *executor = user_data;
 156         bool update_communication = true;
 157
 158         switch (status) {
 159         case CLIENT_TRANSMISSION_STATUS_COMPLETE:
 160                 DBG("Successfully sent full notification to client, client_id = %" PRIu64,
 161                                 client->id);
 162                 update_communication = false;
 163                 break;
 164         case CLIENT_TRANSMISSION_STATUS_QUEUED:
 165                 DBG("Queued notification in client outgoing buffer, client_id = %" PRIu64,
 166                                 client->id);
 167                 break;
 168         case CLIENT_TRANSMISSION_STATUS_FAIL:
 169                 DBG("Communication error occurred while sending notification to client, client_id = %" PRIu64,
 170                                 client->id);
 171                 break;
 172         default:
 173                 ERR("Fatal error encoutered while sending notification to client, client_id = %" PRIu64,
 174                                 client->id);
 175                 ret = -1;
 176                 goto end;
 177         }
 178
 179         if (!update_communication) {
 180                 goto end;
 181         }
 182
 183         /* Safe to read client's id without locking as it is immutable. */
 184         ret = notification_thread_client_communication_update(
 185                         executor->notification_thread_handle, client->id,
 186                         status);
 187 end:
 188         return ret;
 189 }
 190
 191 static int action_executor_notify_handler(struct action_executor *executor,
 192                 const struct action_work_item *work_item,
 193                 const struct lttng_action *action)
 194 {
 195         return notification_client_list_send_evaluation(work_item->client_list,
 196                         lttng_trigger_get_const_condition(work_item->trigger),
 197                         work_item->evaluation,
 198                         lttng_trigger_get_credentials(work_item->trigger),
 199                         work_item->object_creds.is_set ?
 200                                         &(work_item->object_creds.value) :
 201                                         NULL,
 202                         client_handle_transmission_status, executor);
 203 }
 204
 205 static int action_executor_incr_value_handler(struct action_executor *executor,
 206                 const struct action_work_item *work_item,
 207                 const struct lttng_action *action)
 208 {
 209         /* This action is executed by the tracer. */
 210         return 0;
 211 }
 212
 213 static int action_executor_start_session_handler(struct action_executor *executor,
 214                 const struct action_work_item *work_item,
 215                 const struct lttng_action *action)
 216 {
 217         int ret = 0;
 218         const char *session_name;
 219         enum lttng_action_status action_status;
 220         struct ltt_session *session;
 221         enum lttng_error_code cmd_ret;
 222
 223         action_status = lttng_action_start_session_get_session_name(
 224                         action, &session_name);
 225         if (action_status != LTTNG_ACTION_STATUS_OK) {
 226                 ERR("Failed to get session name from `%s` action",
 227                                 get_action_name(action));
 228                 ret = -1;
 229                 goto end;
 230         }
 231
 232         session_lock_list();
 233         session = session_find_by_name(session_name);
 234         if (!session) {
 235                 DBG("Failed to find session `%s` by name while executing `%s` action of trigger `%s`",
 236                                 session_name, get_action_name(action),
 237                                 get_trigger_name(work_item->trigger));
 238                 goto error_unlock_list;
 239         }
 240
 241         session_lock(session);
 242         if (!is_trigger_allowed_for_session(work_item->trigger, session)) {
 243                 goto error_dispose_session;
 244         }
 245         cmd_ret = cmd_start_trace(session);
 246         switch (cmd_ret) {
 247         case LTTNG_OK:
 248                 DBG("Successfully started session `%s` on behalf of trigger `%s`",
 249                                 session_name, get_trigger_name(work_item->trigger));
 250                 break;
 251         case LTTNG_ERR_TRACE_ALREADY_STARTED:
 252                 DBG("Attempted to start session `%s` on behalf of trigger `%s` but it was already started",
 253                                 session_name, get_trigger_name(work_item->trigger));
 254                 break;
 255         default:
 256                 WARN("Failed to start session `%s` on behalf of trigger `%s`: %s",
 257                                 session_name, get_trigger_name(work_item->trigger),
 258                                 lttng_strerror(-cmd_ret));
 259                 break;
 260         }
 261
 262 error_dispose_session:
 263         session_unlock(session);
 264         session_put(session);
 265 error_unlock_list:
 266         session_unlock_list();
 267 end:
 268         return ret;
 269 }
 270
 271 static int action_executor_stop_session_handler(struct action_executor *executor,
 272                 const struct action_work_item *work_item,
 273                 const struct lttng_action *action)
 274 {
 275         int ret = 0;
 276         const char *session_name;
 277         enum lttng_action_status action_status;
 278         struct ltt_session *session;
 279         enum lttng_error_code cmd_ret;
 280
 281         action_status = lttng_action_stop_session_get_session_name(
 282                         action, &session_name);
 283         if (action_status != LTTNG_ACTION_STATUS_OK) {
 284                 ERR("Failed to get session name from `%s` action",
 285                                 get_action_name(action));
 286                 ret = -1;
 287                 goto end;
 288         }
 289
 290         session_lock_list();
 291         session = session_find_by_name(session_name);
 292         if (!session) {
 293                 DBG("Failed to find session `%s` by name while executing `%s` action of trigger `%s`",
 294                                 session_name, get_action_name(action),
 295                                 get_trigger_name(work_item->trigger));
 296                 goto error_unlock_list;
 297         }
 298
 299         session_lock(session);
 300         if (!is_trigger_allowed_for_session(work_item->trigger, session)) {
 301                 goto error_dispose_session;
 302         }
 303
 304         cmd_ret = cmd_stop_trace(session);
 305         switch (cmd_ret) {
 306         case LTTNG_OK:
 307                 DBG("Successfully stopped session `%s` on behalf of trigger `%s`",
 308                                 session_name, get_trigger_name(work_item->trigger));
 309                 break;
 310         case LTTNG_ERR_TRACE_ALREADY_STOPPED:
 311                 DBG("Attempted to stop session `%s` on behalf of trigger `%s` but it was already stopped",
 312                                 session_name, get_trigger_name(work_item->trigger));
 313                 break;
 314         default:
 315                 WARN("Failed to stop session `%s` on behalf of trigger `%s`: %s",
 316                                 session_name, get_trigger_name(work_item->trigger),
 317                                 lttng_strerror(-cmd_ret));
 318                 break;
 319         }
 320
 321 error_dispose_session:
 322         session_unlock(session);
 323         session_put(session);
 324 error_unlock_list:
 325         session_unlock_list();
 326 end:
 327         return ret;
 328 }
 329
 330 static int action_executor_rotate_session_handler(struct action_executor *executor,
 331                 const struct action_work_item *work_item,
 332                 const struct lttng_action *action)
 333 {
 334         int ret = 0;
 335         const char *session_name;
 336         enum lttng_action_status action_status;
 337         struct ltt_session *session;
 338         enum lttng_error_code cmd_ret;
 339
 340         action_status = lttng_action_rotate_session_get_session_name(
 341                         action, &session_name);
 342         if (action_status != LTTNG_ACTION_STATUS_OK) {
 343                 ERR("Failed to get session name from `%s` action",
 344                                 get_action_name(action));
 345                 ret = -1;
 346                 goto end;
 347         }
 348
 349         session_lock_list();
 350         session = session_find_by_name(session_name);
 351         if (!session) {
 352                 DBG("Failed to find session `%s` by name while executing `%s` action of trigger `%s`",
 353                                 session_name, get_action_name(action),
 354                                 get_trigger_name(work_item->trigger));
 355                 goto error_unlock_list;
 356         }
 357
 358         session_lock(session);
 359         if (!is_trigger_allowed_for_session(work_item->trigger, session)) {
 360                 goto error_dispose_session;
 361         }
 362
 363         cmd_ret = cmd_rotate_session(session, NULL, false,
 364                         LTTNG_TRACE_CHUNK_COMMAND_TYPE_MOVE_TO_COMPLETED);
 365         switch (cmd_ret) {
 366         case LTTNG_OK:
 367                 DBG("Successfully started rotation of session `%s` on behalf of trigger `%s`",
 368                                 session_name, get_trigger_name(work_item->trigger));
 369                 break;
 370         case LTTNG_ERR_ROTATION_PENDING:
 371                 DBG("Attempted to start a rotation of session `%s` on behalf of trigger `%s` but a rotation is already ongoing",
 372                                 session_name, get_trigger_name(work_item->trigger));
 373                 break;
 374         case LTTNG_ERR_ROTATION_MULTIPLE_AFTER_STOP:
 375         case LTTNG_ERR_ROTATION_AFTER_STOP_CLEAR:
 376                 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",
 377                                 session_name, get_trigger_name(work_item->trigger));
 378                 break;
 379         default:
 380                 WARN("Failed to start a rotation of session `%s` on behalf of trigger `%s`: %s",
 381                                 session_name, get_trigger_name(work_item->trigger),
 382                                 lttng_strerror(-cmd_ret));
 383                 break;
 384         }
 385
 386 error_dispose_session:
 387         session_unlock(session);
 388         session_put(session);
 389 error_unlock_list:
 390         session_unlock_list();
 391 end:
 392         return ret;
 393 }
 394
 395 static int action_executor_snapshot_session_handler(struct action_executor *executor,
 396                 const struct action_work_item *work_item,
 397                 const struct lttng_action *action)
 398 {
 399         int ret = 0;
 400         const char *session_name;
 401         enum lttng_action_status action_status;
 402         struct ltt_session *session;
 403         const struct lttng_snapshot_output default_snapshot_output = {
 404                 .max_size = UINT64_MAX,
 405         };
 406         const struct lttng_snapshot_output *snapshot_output =
 407                         &default_snapshot_output;
 408         enum lttng_error_code cmd_ret;
 409
 410         action_status = lttng_action_snapshot_session_get_session_name(
 411                         action, &session_name);
 412         if (action_status != LTTNG_ACTION_STATUS_OK) {
 413                 ERR("Failed to get session name from `%s` action",
 414                                 get_action_name(action));
 415                 ret = -1;
 416                 goto end;
 417         }
 418
 419         action_status = lttng_action_snapshot_session_get_output(
 420                         action, &snapshot_output);
 421         if (action_status != LTTNG_ACTION_STATUS_OK &&
 422                         action_status != LTTNG_ACTION_STATUS_UNSET) {
 423                 ERR("Failed to get output from `%s` action",
 424                                 get_action_name(action));
 425                 ret = -1;
 426                 goto end;
 427         }
 428
 429         session_lock_list();
 430         session = session_find_by_name(session_name);
 431         if (!session) {
 432                 DBG("Failed to find session `%s` by name while executing `%s` action of trigger `%s`",
 433                                 session_name, get_action_name(action),
 434                                 get_trigger_name(work_item->trigger));
 435                 goto error_unlock_list;
 436         }
 437
 438
 439         session_lock(session);
 440         if (!is_trigger_allowed_for_session(work_item->trigger, session)) {
 441                 goto error_dispose_session;
 442         }
 443
 444         cmd_ret = cmd_snapshot_record(session, snapshot_output, 0);
 445         switch (cmd_ret) {
 446         case LTTNG_OK:
 447                 DBG("Successfully recorded snapshot of session `%s` on behalf of trigger `%s`",
 448                                 session_name, get_trigger_name(work_item->trigger));
 449                 break;
 450         default:
 451                 WARN("Failed to record snapshot of session `%s` on behalf of trigger `%s`: %s",
 452                                 session_name, get_trigger_name(work_item->trigger),
 453                                 lttng_strerror(-cmd_ret));
 454                 break;
 455         }
 456
 457 error_dispose_session:
 458         session_unlock(session);
 459         session_put(session);
 460 error_unlock_list:
 461         session_unlock_list();
 462 end:
 463         return ret;
 464 }
 465
 466 static int action_executor_group_handler(struct action_executor *executor,
 467                 const struct action_work_item *work_item,
 468                 const struct lttng_action *action_group)
 469 {
 470         int ret = 0;
 471         unsigned int i, count;
 472         enum lttng_action_status action_status;
 473
 474         action_status = lttng_action_group_get_count(action_group, &count);
 475         if (action_status != LTTNG_ACTION_STATUS_OK) {
 476                 /* Fatal error. */
 477                 ERR("Failed to get count of action in action group");
 478                 ret = -1;
 479                 goto end;
 480         }
 481
 482         DBG("Action group has %u action%s", count, count != 1 ? "s" : "");
 483         for (i = 0; i < count; i++) {
 484                 const struct lttng_action *action =
 485                                 lttng_action_group_get_at_index(
 486                                                 action_group, i);
 487
 488                 ret = action_executor_generic_handler(
 489                                 executor, work_item, action);
 490                 if (ret) {
 491                         ERR("Stopping the execution of the action group of trigger `%s` following a fatal error",
 492                                         get_trigger_name(work_item->trigger));
 493                         goto end;
 494                 }
 495         }
 496 end:
 497         return ret;
 498 }
 499
 500 static int action_executor_generic_handler(struct action_executor *executor,
 501                 const struct action_work_item *work_item,
 502                 const struct lttng_action *action)
 503 {
 504         const enum lttng_action_type action_type = lttng_action_get_type(action);
 505
 506         assert(action_type != LTTNG_ACTION_TYPE_UNKNOWN);
 507
 508         DBG("Executing action `%s` of trigger `%s` action work item %" PRIu64,
 509                         get_action_name(action),
 510                         get_trigger_name(work_item->trigger),
 511                         work_item->id);
 512
 513         return action_executors[action_type](
 514                         executor, work_item, action);
 515 }
 516
 517 static int action_work_item_execute(struct action_executor *executor,
 518                 struct action_work_item *work_item)
 519 {
 520         int ret;
 521         const struct lttng_action *action =
 522                         lttng_trigger_get_const_action(work_item->trigger);
 523
 524         DBG("Starting execution of action work item %" PRIu64 " of trigger `%s`",
 525                         work_item->id, get_trigger_name(work_item->trigger));
 526         ret = action_executor_generic_handler(executor, work_item, action);
 527         DBG("Completed execution of action work item %" PRIu64 " of trigger `%s`",
 528                         work_item->id, get_trigger_name(work_item->trigger));
 529         return ret;
 530 }
 531
 532 static void action_work_item_destroy(struct action_work_item *work_item)
 533 {
 534         lttng_trigger_put(work_item->trigger);
 535         lttng_evaluation_destroy(work_item->evaluation);
 536         notification_client_list_put(work_item->client_list);
 537         free(work_item);
 538 }
 539
 540 static void *action_executor_thread(void *_data)
 541 {
 542         struct action_executor *executor = _data;
 543
 544         assert(executor);
 545
 546         health_register(health_sessiond, HEALTH_SESSIOND_TYPE_ACTION_EXECUTOR);
 547
 548         rcu_register_thread();
 549         rcu_thread_online();
 550
 551         DBG("Entering work execution loop");
 552         pthread_mutex_lock(&executor->work.lock);
 553         while (!executor->should_quit) {
 554                 int ret;
 555                 struct action_work_item *work_item;
 556
 557                 health_code_update();
 558                 if (executor->work.pending_count == 0) {
 559                         health_poll_entry();
 560                         DBG("No work items enqueued, entering wait");
 561                         pthread_cond_wait(&executor->work.cond,
 562                                         &executor->work.lock);
 563                         DBG("Woke-up from wait");
 564                         health_poll_exit();
 565                         continue;
 566                 }
 567
 568                 /* Pop item from front of the list with work lock held. */
 569                 work_item = cds_list_first_entry(&executor->work.list,
 570                                 struct action_work_item, list_node);
 571                 cds_list_del(&work_item->list_node);
 572                 executor->work.pending_count--;
 573
 574                 /*
 575                  * Work can be performed without holding the work lock,
 576                  * allowing new items to be queued.
 577                  */
 578                 pthread_mutex_unlock(&executor->work.lock);
 579                 ret = action_work_item_execute(executor, work_item);
 580                 action_work_item_destroy(work_item);
 581                 if (ret) {
 582                         /* Fatal error. */
 583                         break;
 584                 }
 585
 586                 health_code_update();
 587                 pthread_mutex_lock(&executor->work.lock);
 588         }
 589
 590         if (executor->should_quit) {
 591                 pthread_mutex_unlock(&executor->work.lock);
 592         }
 593         DBG("Left work execution loop");
 594
 595         health_code_update();
 596
 597         rcu_thread_offline();
 598         rcu_unregister_thread();
 599         health_unregister(health_sessiond);
 600
 601         return NULL;
 602 }
 603
 604 static bool shutdown_action_executor_thread(void *_data)
 605 {
 606         struct action_executor *executor = _data;
 607
 608         pthread_mutex_lock(&executor->work.lock);
 609         executor->should_quit = true;
 610         pthread_cond_signal(&executor->work.cond);
 611         pthread_mutex_unlock(&executor->work.lock);
 612         return true;
 613 }
 614
 615 static void clean_up_action_executor_thread(void *_data)
 616 {
 617         struct action_executor *executor = _data;
 618
 619         assert(cds_list_empty(&executor->work.list));
 620
 621         pthread_mutex_destroy(&executor->work.lock);
 622         pthread_cond_destroy(&executor->work.cond);
 623         free(executor);
 624 }
 625
 626 struct action_executor *action_executor_create(
 627                 struct notification_thread_handle *handle)
 628 {
 629         struct action_executor *executor = zmalloc(sizeof(*executor));
 630
 631         if (!executor) {
 632                 goto end;
 633         }
 634
 635         CDS_INIT_LIST_HEAD(&executor->work.list);
 636         pthread_cond_init(&executor->work.cond, NULL);
 637         pthread_mutex_init(&executor->work.lock, NULL);
 638         executor->notification_thread_handle = handle;
 639
 640         executor->thread = lttng_thread_create(THREAD_NAME,
 641                         action_executor_thread, shutdown_action_executor_thread,
 642                         clean_up_action_executor_thread, executor);
 643 end:
 644         return executor;
 645 }
 646
 647 void action_executor_destroy(struct action_executor *executor)
 648 {
 649         struct action_work_item *work_item, *tmp;
 650
 651         /* TODO Wait for work list to drain? */
 652         lttng_thread_shutdown(executor->thread);
 653         pthread_mutex_lock(&executor->work.lock);
 654         if (executor->work.pending_count != 0) {
 655                 WARN("%" PRIu64
 656                         " trigger action%s still queued for execution and will be discarded",
 657                                 executor->work.pending_count,
 658                                 executor->work.pending_count == 1 ? " is" :
 659                                                                     "s are");
 660         }
 661
 662         cds_list_for_each_entry_safe (
 663                         work_item, tmp, &executor->work.list, list_node) {
 664                 WARN("Discarding action work item %" PRIu64
 665                                 " associated to trigger `%s`",
 666                                 work_item->id, get_trigger_name(work_item->trigger));
 667                 cds_list_del(&work_item->list_node);
 668                 action_work_item_destroy(work_item);
 669         }
 670         pthread_mutex_unlock(&executor->work.lock);
 671         lttng_thread_put(executor->thread);
 672 }
 673
 674 /* RCU read-lock must be held by the caller. */
 675 enum action_executor_status action_executor_enqueue(
 676                 struct action_executor *executor,
 677                 struct lttng_trigger *trigger,
 678                 struct lttng_evaluation *evaluation,
 679                 const struct lttng_credentials *object_creds,
 680                 struct notification_client_list *client_list)
 681 {
 682         enum action_executor_status executor_status = ACTION_EXECUTOR_STATUS_OK;
 683         const uint64_t work_item_id = executor->next_work_item_id++;
 684         struct action_work_item *work_item;
 685         bool signal = false;
 686
 687         pthread_mutex_lock(&executor->work.lock);
 688         /* Check for queue overflow. */
 689         if (executor->work.pending_count >= MAX_QUEUED_WORK_COUNT) {
 690                 /* Most likely spammy, remove if it is the case. */
 691                 DBG("Refusing to enqueue action for trigger `%s` as work item %" PRIu64
 692                         " (overflow)", get_trigger_name(trigger), work_item_id);
 693                 executor_status = ACTION_EXECUTOR_STATUS_OVERFLOW;
 694                 goto error_unlock;
 695         }
 696
 697         work_item = zmalloc(sizeof(*work_item));
 698         if (!work_item) {
 699                 PERROR("Failed to allocate action executor work item on behalf of trigger `%s`",
 700                                 get_trigger_name(trigger));
 701                 executor_status = ACTION_EXECUTOR_STATUS_ERROR;
 702                 goto error_unlock;
 703         }
 704
 705         lttng_trigger_get(trigger);
 706         if (client_list) {
 707                 const bool reference_acquired =
 708                                 notification_client_list_get(client_list);
 709
 710                 assert(reference_acquired);
 711         }
 712
 713         *work_item = (typeof(*work_item)){
 714                         .id = work_item_id,
 715                         .trigger = trigger,
 716                         /* Ownership transferred to the work item. */
 717                         .evaluation = evaluation,
 718                         .object_creds = {
 719                                 .is_set = !!object_creds,
 720                                 .value = object_creds ? *object_creds :
 721                                         (typeof(work_item->object_creds.value)) {},
 722                         },
 723                         .client_list = client_list,
 724                         .list_node = CDS_LIST_HEAD_INIT(work_item->list_node),
 725         };
 726
 727         evaluation = NULL;
 728         cds_list_add_tail(&work_item->list_node, &executor->work.list);
 729         executor->work.pending_count++;
 730         DBG("Enqueued action for trigger `%s` as work item #%" PRIu64,
 731                         get_trigger_name(trigger), work_item_id);
 732         signal = true;
 733
 734 error_unlock:
 735         if (signal) {
 736                 pthread_cond_signal(&executor->work.cond);
 737         }
 738         pthread_mutex_unlock(&executor->work.lock);
 739
 740         lttng_evaluation_destroy(evaluation);
 741         return executor_status;
 742 }