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

   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.hpp"
   9 #include "cmd.hpp"
  10 #include "health-sessiond.hpp"
  11 #include "lttng-sessiond.hpp"
  12 #include "notification-thread-internal.hpp"
  13 #include "session.hpp"
  14 #include "thread.hpp"
  15
  16 #include <common/dynamic-array.hpp>
  17 #include <common/macros.hpp>
  18 #include <common/optional.hpp>
  19
  20 #include <lttng/action/action-internal.hpp>
  21 #include <lttng/action/list-internal.hpp>
  22 #include <lttng/action/list.h>
  23 #include <lttng/action/notify-internal.hpp>
  24 #include <lttng/action/notify.h>
  25 #include <lttng/action/rotate-session.h>
  26 #include <lttng/action/snapshot-session.h>
  27 #include <lttng/action/start-session.h>
  28 #include <lttng/action/stop-session.h>
  29 #include <lttng/condition/evaluation.h>
  30 #include <lttng/condition/event-rule-matches-internal.hpp>
  31 #include <lttng/lttng-error.h>
  32 #include <lttng/trigger/trigger-internal.hpp>
  33
  34 #include <pthread.h>
  35 #include <stdbool.h>
  36 #include <stddef.h>
  37 #include <urcu/list.h>
  38
  39 #define THREAD_NAME           "Action Executor"
  40 #define MAX_QUEUED_WORK_COUNT 8192
  41
  42 struct action_executor {
  43         struct lttng_thread *thread;
  44         struct notification_thread_handle *notification_thread_handle;
  45         struct {
  46                 uint64_t pending_count;
  47                 struct cds_list_head list;
  48                 pthread_cond_t cond;
  49                 pthread_mutex_t lock;
  50         } work;
  51         bool should_quit;
  52         uint64_t next_work_item_id;
  53 };
  54
  55 namespace {
  56 /*
  57  * A work item is composed of a dynamic array of sub-items which
  58  * represent a flattened, and augmented, version of a trigger's actions.
  59  *
  60  * We cannot rely solely on the trigger's actions since each action can have an
  61  * execution context we need to comply with.
  62  *
  63  * The notion of execution context is required since for some actions the
  64  * associated object are referenced by name and not by id. This can lead to
  65  * a number of ambiguities when executing an action work item.
  66  *
  67  * For example, let's take a simple trigger such as:
  68  *   - condition: ust event a
  69  *   - action: start session S
  70  *
  71  * At time T, session S exists.
  72  * At T + 1, the event A is hit.
  73  * At T + 2, the tracer event notification is received and the work item is
  74  * queued. Here session S have an id of 1.
  75  * At T + 3, the session S is destroyed and a new session S is created, with a
  76  * resulting id of 200.
  77  * At T +4, the work item is popped from the queue and begin execution and will
  78  * start session S with an id of 200 instead of the session S id 1 that was
  79  * present at the queuing phase.
  80  *
  81  * The context to be respected is the one when the work item is queued. If the
  82  * execution context is not the same at the moment of execution, we skip the
  83  * execution of that sub-item.
  84  *
  85  * It is the same policy in regards to the validity of the associated
  86  * trigger object at the moment of execution, if the trigger is found to be
  87  * unregistered, the execution is skipped.
  88  */
  89 struct action_work_item {
  90         uint64_t id;
  91
  92         /*
  93          * The actions to be executed with their respective execution context.
  94          * See struct `action_work_subitem`.
  95          */
  96         struct lttng_dynamic_array subitems;
  97
  98         /* Execution context data */
  99         struct lttng_trigger *trigger;
 100         struct lttng_evaluation *evaluation;
 101         struct notification_client_list *client_list;
 102         LTTNG_OPTIONAL(struct lttng_credentials) object_creds;
 103         struct cds_list_head list_node;
 104 };
 105
 106 struct action_work_subitem {
 107         struct lttng_action *action;
 108         struct {
 109                 /* Used by actions targeting a session. */
 110                 LTTNG_OPTIONAL(uint64_t) session_id;
 111         } context;
 112 };
 113 } /* namespace */
 114
 115 /*
 116  * Only return non-zero on a fatal error that should shut down the action
 117  * executor.
 118  */
 119 using action_executor_handler = int (*)(struct action_executor *,
 120                                         const struct action_work_item *,
 121                                         struct action_work_subitem *);
 122
 123 static int action_executor_notify_handler(struct action_executor *executor,
 124                                           const struct action_work_item *,
 125                                           struct action_work_subitem *);
 126 static int action_executor_start_session_handler(struct action_executor *executor,
 127                                                  const struct action_work_item *,
 128                                                  struct action_work_subitem *);
 129 static int action_executor_stop_session_handler(struct action_executor *executor,
 130                                                 const struct action_work_item *,
 131                                                 struct action_work_subitem *);
 132 static int action_executor_rotate_session_handler(struct action_executor *executor,
 133                                                   const struct action_work_item *,
 134                                                   struct action_work_subitem *);
 135 static int action_executor_snapshot_session_handler(struct action_executor *executor,
 136                                                     const struct action_work_item *,
 137                                                     struct action_work_subitem *);
 138 static int action_executor_list_handler(struct action_executor *executor,
 139                                         const struct action_work_item *,
 140                                         struct action_work_subitem *);
 141 static int action_executor_generic_handler(struct action_executor *executor,
 142                                            const struct action_work_item *,
 143                                            struct action_work_subitem *);
 144
 145 static const action_executor_handler action_executors[] = {
 146         action_executor_notify_handler,           action_executor_start_session_handler,
 147         action_executor_stop_session_handler,     action_executor_rotate_session_handler,
 148         action_executor_snapshot_session_handler, action_executor_list_handler,
 149 };
 150
 151 /* Forward declaration */
 152 static int add_action_to_subitem_array(struct lttng_action *action,
 153                                        struct lttng_dynamic_array *subitems);
 154
 155 static int populate_subitem_array_from_trigger(struct lttng_trigger *trigger,
 156                                                struct lttng_dynamic_array *subitems);
 157
 158 static void action_work_subitem_destructor(void *element)
 159 {
 160         struct action_work_subitem *subitem = (action_work_subitem *) element;
 161
 162         lttng_action_put(subitem->action);
 163 }
 164
 165 static const char *get_action_name(const struct lttng_action *action)
 166 {
 167         const enum lttng_action_type action_type = lttng_action_get_type(action);
 168
 169         LTTNG_ASSERT(action_type != LTTNG_ACTION_TYPE_UNKNOWN);
 170
 171         return lttng_action_type_string(action_type);
 172 }
 173
 174 /* Check if this trigger allowed to interect with a given session. */
 175 static bool is_trigger_allowed_for_session(const struct lttng_trigger *trigger,
 176                                            struct ltt_session *session)
 177 {
 178         bool is_allowed = false;
 179         const struct lttng_credentials session_creds = {
 180                 .uid = LTTNG_OPTIONAL_INIT_VALUE(session->uid),
 181                 .gid = LTTNG_OPTIONAL_INIT_VALUE(session->gid),
 182         };
 183         /* Can never be NULL. */
 184         const struct lttng_credentials *trigger_creds = lttng_trigger_get_credentials(trigger);
 185
 186         is_allowed = (lttng_credentials_is_equal_uid(trigger_creds, &session_creds)) ||
 187                 (lttng_credentials_get_uid(trigger_creds) == 0);
 188         if (!is_allowed) {
 189                 WARN("Trigger is not allowed to interact with session `%s`: session uid = %ld, session gid = %ld, trigger uid = %ld",
 190                      session->name,
 191                      (long int) session->uid,
 192                      (long int) session->gid,
 193                      (long int) lttng_credentials_get_uid(trigger_creds));
 194         }
 195
 196         return is_allowed;
 197 }
 198
 199 static const char *get_trigger_name(const struct lttng_trigger *trigger)
 200 {
 201         const char *trigger_name;
 202         enum lttng_trigger_status trigger_status;
 203
 204         trigger_status = lttng_trigger_get_name(trigger, &trigger_name);
 205         switch (trigger_status) {
 206         case LTTNG_TRIGGER_STATUS_OK:
 207                 break;
 208         case LTTNG_TRIGGER_STATUS_UNSET:
 209                 trigger_name = "(anonymous)";
 210                 break;
 211         default:
 212                 trigger_name = "(failed to get name)";
 213                 break;
 214         }
 215
 216         return trigger_name;
 217 }
 218
 219 static int client_handle_transmission_status(struct notification_client *client,
 220                                              enum client_transmission_status status,
 221                                              void *user_data)
 222 {
 223         int ret = 0;
 224         struct action_executor *executor = (action_executor *) user_data;
 225         bool update_communication = true;
 226
 227         switch (status) {
 228         case CLIENT_TRANSMISSION_STATUS_COMPLETE:
 229                 DBG("Successfully sent full notification to client, client_id = %" PRIu64,
 230                     client->id);
 231                 /*
 232                  * There is no need to wake the (e)poll thread. If it was waiting for
 233                  * "out" events on the client's socket, it will see that no payload
 234                  * in queued and will unsubscribe from that event.
 235                  *
 236                  * In the other cases, we have to wake the the (e)poll thread to either
 237                  * handle the error on the client or to get it to monitor the client "out"
 238                  * events.
 239                  */
 240                 update_communication = false;
 241                 break;
 242         case CLIENT_TRANSMISSION_STATUS_QUEUED:
 243                 DBG("Queued notification in client outgoing buffer, client_id = %" PRIu64,
 244                     client->id);
 245                 break;
 246         case CLIENT_TRANSMISSION_STATUS_FAIL:
 247                 DBG("Communication error occurred while sending notification to client, client_id = %" PRIu64,
 248                     client->id);
 249                 break;
 250         default:
 251                 ERR("Fatal error encoutered while sending notification to client, client_id = %" PRIu64,
 252                     client->id);
 253                 ret = -1;
 254                 goto end;
 255         }
 256
 257         if (!update_communication) {
 258                 goto end;
 259         }
 260
 261         /* Safe to read client's id without locking as it is immutable. */
 262         ret = notification_thread_client_communication_update(
 263                 executor->notification_thread_handle, client->id, status);
 264 end:
 265         return ret;
 266 }
 267
 268 static int action_executor_notify_handler(struct action_executor *executor,
 269                                           const struct action_work_item *work_item,
 270                                           struct action_work_subitem *item __attribute__((unused)))
 271 {
 272         return notification_client_list_send_evaluation(
 273                 work_item->client_list,
 274                 work_item->trigger,
 275                 work_item->evaluation,
 276                 work_item->object_creds.is_set ? &(work_item->object_creds.value) : nullptr,
 277                 client_handle_transmission_status,
 278                 executor);
 279 }
 280
 281 static int action_executor_start_session_handler(struct action_executor *executor
 282                                                  __attribute__((unused)),
 283                                                  const struct action_work_item *work_item,
 284                                                  struct action_work_subitem *item)
 285 {
 286         int ret = 0;
 287         const char *session_name;
 288         enum lttng_action_status action_status;
 289         struct ltt_session *session;
 290         enum lttng_error_code cmd_ret;
 291         struct lttng_action *action = item->action;
 292
 293         action_status = lttng_action_start_session_get_session_name(action, &session_name);
 294         if (action_status != LTTNG_ACTION_STATUS_OK) {
 295                 ERR("Failed to get session name from `%s` action", get_action_name(action));
 296                 ret = -1;
 297                 goto end;
 298         }
 299
 300         /*
 301          * Validate if at the moment of the action was queued the session
 302          * existed. If not skip the action altogether.
 303          */
 304         if (!item->context.session_id.is_set) {
 305                 DBG("Session `%s` was not present at the moment the work item was enqueued for `%s` action of trigger `%s`",
 306                     session_name,
 307                     get_action_name(action),
 308                     get_trigger_name(work_item->trigger));
 309                 lttng_action_increase_execution_failure_count(action);
 310                 goto end;
 311         }
 312
 313         session_lock_list();
 314         rcu_read_lock();
 315         session = session_find_by_id(LTTNG_OPTIONAL_GET(item->context.session_id));
 316         if (!session) {
 317                 DBG("Failed to find session `%s` by name while executing `%s` action of trigger `%s`",
 318                     session_name,
 319                     get_action_name(action),
 320                     get_trigger_name(work_item->trigger));
 321                 lttng_action_increase_execution_failure_count(action);
 322                 goto error_unlock_list;
 323         }
 324
 325         session_lock(session);
 326         if (session->destroyed) {
 327                 DBG("Session `%s` with id = %" PRIu64
 328                     " is flagged as destroyed. Skipping: action = `%s`, trigger = `%s`",
 329                     session->name,
 330                     session->id,
 331                     get_action_name(action),
 332                     get_trigger_name(work_item->trigger));
 333                 goto error_unlock_session;
 334         }
 335
 336         if (!is_trigger_allowed_for_session(work_item->trigger, session)) {
 337                 goto error_unlock_session;
 338         }
 339
 340         cmd_ret = (lttng_error_code) cmd_start_trace(session);
 341         switch (cmd_ret) {
 342         case LTTNG_OK:
 343                 DBG("Successfully started session `%s` on behalf of trigger `%s`",
 344                     session_name,
 345                     get_trigger_name(work_item->trigger));
 346                 break;
 347         case LTTNG_ERR_TRACE_ALREADY_STARTED:
 348                 DBG("Attempted to start session `%s` on behalf of trigger `%s` but it was already started",
 349                     session_name,
 350                     get_trigger_name(work_item->trigger));
 351                 break;
 352         default:
 353                 WARN("Failed to start session `%s` on behalf of trigger `%s`: %s",
 354                      session_name,
 355                      get_trigger_name(work_item->trigger),
 356                      lttng_strerror(-cmd_ret));
 357                 lttng_action_increase_execution_failure_count(action);
 358                 break;
 359         }
 360
 361 error_unlock_session:
 362         session_unlock(session);
 363         session_put(session);
 364 error_unlock_list:
 365         rcu_read_unlock();
 366         session_unlock_list();
 367 end:
 368         return ret;
 369 }
 370
 371 static int action_executor_stop_session_handler(struct action_executor *executor
 372                                                 __attribute__((unused)),
 373                                                 const struct action_work_item *work_item,
 374                                                 struct action_work_subitem *item)
 375 {
 376         int ret = 0;
 377         const char *session_name;
 378         enum lttng_action_status action_status;
 379         struct ltt_session *session;
 380         enum lttng_error_code cmd_ret;
 381         struct lttng_action *action = item->action;
 382
 383         action_status = lttng_action_stop_session_get_session_name(action, &session_name);
 384         if (action_status != LTTNG_ACTION_STATUS_OK) {
 385                 ERR("Failed to get session name from `%s` action", get_action_name(action));
 386                 ret = -1;
 387                 goto end;
 388         }
 389
 390         /*
 391          * Validate if, at the moment the action was queued, the target session
 392          * existed. If not, skip the action altogether.
 393          */
 394         if (!item->context.session_id.is_set) {
 395                 DBG("Session `%s` was not present at the moment the work item was enqueued for `%s` action of trigger `%s`",
 396                     session_name,
 397                     get_action_name(action),
 398                     get_trigger_name(work_item->trigger));
 399                 lttng_action_increase_execution_failure_count(action);
 400                 goto end;
 401         }
 402
 403         session_lock_list();
 404         rcu_read_lock();
 405         session = session_find_by_id(LTTNG_OPTIONAL_GET(item->context.session_id));
 406         if (!session) {
 407                 DBG("Failed to find session `%s` by name while executing `%s` action of trigger `%s`",
 408                     session_name,
 409                     get_action_name(action),
 410                     get_trigger_name(work_item->trigger));
 411                 lttng_action_increase_execution_failure_count(action);
 412                 goto error_unlock_list;
 413         }
 414
 415         session_lock(session);
 416         if (session->destroyed) {
 417                 DBG("Session `%s` with id = %" PRIu64
 418                     " is flagged as destroyed. Skipping: action = `%s`, trigger = `%s`",
 419                     session->name,
 420                     session->id,
 421                     get_action_name(action),
 422                     get_trigger_name(work_item->trigger));
 423                 goto error_unlock_session;
 424         }
 425
 426         if (!is_trigger_allowed_for_session(work_item->trigger, session)) {
 427                 goto error_unlock_session;
 428         }
 429
 430         cmd_ret = (lttng_error_code) cmd_stop_trace(session);
 431         switch (cmd_ret) {
 432         case LTTNG_OK:
 433                 DBG("Successfully stopped session `%s` on behalf of trigger `%s`",
 434                     session_name,
 435                     get_trigger_name(work_item->trigger));
 436                 break;
 437         case LTTNG_ERR_TRACE_ALREADY_STOPPED:
 438                 DBG("Attempted to stop session `%s` on behalf of trigger `%s` but it was already stopped",
 439                     session_name,
 440                     get_trigger_name(work_item->trigger));
 441                 break;
 442         default:
 443                 WARN("Failed to stop session `%s` on behalf of trigger `%s`: %s",
 444                      session_name,
 445                      get_trigger_name(work_item->trigger),
 446                      lttng_strerror(-cmd_ret));
 447                 lttng_action_increase_execution_failure_count(action);
 448                 break;
 449         }
 450
 451 error_unlock_session:
 452         session_unlock(session);
 453         session_put(session);
 454 error_unlock_list:
 455         rcu_read_unlock();
 456         session_unlock_list();
 457 end:
 458         return ret;
 459 }
 460
 461 static int action_executor_rotate_session_handler(struct action_executor *executor
 462                                                   __attribute__((unused)),
 463                                                   const struct action_work_item *work_item,
 464                                                   struct action_work_subitem *item)
 465 {
 466         int ret = 0;
 467         const char *session_name;
 468         enum lttng_action_status action_status;
 469         struct ltt_session *session;
 470         enum lttng_error_code cmd_ret;
 471         struct lttng_action *action = item->action;
 472
 473         action_status = lttng_action_rotate_session_get_session_name(action, &session_name);
 474         if (action_status != LTTNG_ACTION_STATUS_OK) {
 475                 ERR("Failed to get session name from `%s` action", get_action_name(action));
 476                 ret = -1;
 477                 goto end;
 478         }
 479
 480         /*
 481          * Validate if, at the moment the action was queued, the target session
 482          * existed. If not, skip the action altogether.
 483          */
 484         if (!item->context.session_id.is_set) {
 485                 DBG("Session `%s` was not present at the moment the work item was enqueued for `%s` action of trigger `%s`",
 486                     session_name,
 487                     get_action_name(action),
 488                     get_trigger_name(work_item->trigger));
 489                 lttng_action_increase_execution_failure_count(action);
 490                 goto end;
 491         }
 492
 493         session_lock_list();
 494         rcu_read_lock();
 495         session = session_find_by_id(LTTNG_OPTIONAL_GET(item->context.session_id));
 496         if (!session) {
 497                 DBG("Failed to find session `%s` by name while executing `%s` action of trigger `%s`",
 498                     session_name,
 499                     get_action_name(action),
 500                     get_trigger_name(work_item->trigger));
 501                 lttng_action_increase_execution_failure_count(action);
 502                 goto error_unlock_list;
 503         }
 504
 505         session_lock(session);
 506         if (session->destroyed) {
 507                 DBG("Session `%s` with id = %" PRIu64
 508                     " is flagged as destroyed. Skipping: action = `%s`, trigger = `%s`",
 509                     session->name,
 510                     session->id,
 511                     get_action_name(action),
 512                     get_trigger_name(work_item->trigger));
 513                 goto error_unlock_session;
 514         }
 515
 516         if (!is_trigger_allowed_for_session(work_item->trigger, session)) {
 517                 goto error_unlock_session;
 518         }
 519
 520         cmd_ret = (lttng_error_code) cmd_rotate_session(
 521                 session, nullptr, false, LTTNG_TRACE_CHUNK_COMMAND_TYPE_MOVE_TO_COMPLETED);
 522         switch (cmd_ret) {
 523         case LTTNG_OK:
 524                 DBG("Successfully started rotation of session `%s` on behalf of trigger `%s`",
 525                     session_name,
 526                     get_trigger_name(work_item->trigger));
 527                 break;
 528         case LTTNG_ERR_ROTATION_PENDING:
 529                 DBG("Attempted to start a rotation of session `%s` on behalf of trigger `%s` but a rotation is already ongoing",
 530                     session_name,
 531                     get_trigger_name(work_item->trigger));
 532                 lttng_action_increase_execution_failure_count(action);
 533                 break;
 534         case LTTNG_ERR_ROTATION_MULTIPLE_AFTER_STOP:
 535         case LTTNG_ERR_ROTATION_AFTER_STOP_CLEAR:
 536                 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",
 537                     session_name,
 538                     get_trigger_name(work_item->trigger));
 539                 break;
 540         default:
 541                 WARN("Failed to start a rotation of session `%s` on behalf of trigger `%s`: %s",
 542                      session_name,
 543                      get_trigger_name(work_item->trigger),
 544                      lttng_strerror(-cmd_ret));
 545                 lttng_action_increase_execution_failure_count(action);
 546                 break;
 547         }
 548
 549 error_unlock_session:
 550         session_unlock(session);
 551         session_put(session);
 552 error_unlock_list:
 553         rcu_read_unlock();
 554         session_unlock_list();
 555 end:
 556         return ret;
 557 }
 558
 559 static int action_executor_snapshot_session_handler(struct action_executor *executor
 560                                                     __attribute__((unused)),
 561                                                     const struct action_work_item *work_item,
 562                                                     struct action_work_subitem *item)
 563 {
 564         int ret = 0;
 565         const char *session_name;
 566         enum lttng_action_status action_status;
 567         struct ltt_session *session;
 568         lttng_snapshot_output default_snapshot_output;
 569         const struct lttng_snapshot_output *snapshot_output = &default_snapshot_output;
 570         enum lttng_error_code cmd_ret;
 571         struct lttng_action *action = item->action;
 572
 573         default_snapshot_output.max_size = UINT64_MAX;
 574
 575         /*
 576          * Validate if, at the moment the action was queued, the target session
 577          * existed. If not, skip the action altogether.
 578          */
 579         if (!item->context.session_id.is_set) {
 580                 DBG("Session was not present at the moment the work item was enqueued for `%s` action of trigger `%s`",
 581                     get_action_name(action),
 582                     get_trigger_name(work_item->trigger));
 583                 lttng_action_increase_execution_failure_count(action);
 584                 goto end;
 585         }
 586
 587         action_status = lttng_action_snapshot_session_get_session_name(action, &session_name);
 588         if (action_status != LTTNG_ACTION_STATUS_OK) {
 589                 ERR("Failed to get session name from `%s` action", get_action_name(action));
 590                 ret = -1;
 591                 goto end;
 592         }
 593
 594         action_status = lttng_action_snapshot_session_get_output(action, &snapshot_output);
 595         if (action_status != LTTNG_ACTION_STATUS_OK && action_status != LTTNG_ACTION_STATUS_UNSET) {
 596                 ERR("Failed to get output from `%s` action", get_action_name(action));
 597                 ret = -1;
 598                 goto end;
 599         }
 600
 601         session_lock_list();
 602         rcu_read_lock();
 603         session = session_find_by_id(LTTNG_OPTIONAL_GET(item->context.session_id));
 604         if (!session) {
 605                 DBG("Failed to find session `%s` by name while executing `%s` action of trigger `%s`",
 606                     session_name,
 607                     get_action_name(action),
 608                     get_trigger_name(work_item->trigger));
 609                 lttng_action_increase_execution_failure_count(action);
 610                 goto error_unlock_list;
 611         }
 612
 613         session_lock(session);
 614         if (session->destroyed) {
 615                 DBG("Session `%s` with id = %" PRIu64
 616                     " is flagged as destroyed. Skipping: action = `%s`, trigger = `%s`",
 617                     session->name,
 618                     session->id,
 619                     get_action_name(action),
 620                     get_trigger_name(work_item->trigger));
 621                 goto error_unlock_session;
 622         }
 623
 624         if (!is_trigger_allowed_for_session(work_item->trigger, session)) {
 625                 goto error_unlock_session;
 626         }
 627
 628         cmd_ret = (lttng_error_code) cmd_snapshot_record(session, snapshot_output, 0);
 629         switch (cmd_ret) {
 630         case LTTNG_OK:
 631                 DBG("Successfully recorded snapshot of session `%s` on behalf of trigger `%s`",
 632                     session_name,
 633                     get_trigger_name(work_item->trigger));
 634                 break;
 635         default:
 636                 WARN("Failed to record snapshot of session `%s` on behalf of trigger `%s`: %s",
 637                      session_name,
 638                      get_trigger_name(work_item->trigger),
 639                      lttng_strerror(-cmd_ret));
 640                 lttng_action_increase_execution_failure_count(action);
 641                 break;
 642         }
 643
 644 error_unlock_session:
 645         session_unlock(session);
 646         session_put(session);
 647 error_unlock_list:
 648         rcu_read_unlock();
 649         session_unlock_list();
 650 end:
 651         return ret;
 652 }
 653
 654 static int action_executor_list_handler(struct action_executor *executor __attribute__((unused)),
 655                                         const struct action_work_item *work_item
 656                                         __attribute__((unused)),
 657                                         struct action_work_subitem *item __attribute__((unused)))
 658 {
 659         ERR("Execution of a list action by the action executor should never occur");
 660         abort();
 661 }
 662
 663 static int action_executor_generic_handler(struct action_executor *executor,
 664                                            const struct action_work_item *work_item,
 665                                            struct action_work_subitem *item)
 666 {
 667         int ret;
 668         struct lttng_action *action = item->action;
 669         const enum lttng_action_type action_type = lttng_action_get_type(action);
 670
 671         LTTNG_ASSERT(action_type != LTTNG_ACTION_TYPE_UNKNOWN);
 672
 673         lttng_action_increase_execution_request_count(action);
 674         if (!lttng_action_should_execute(action)) {
 675                 DBG("Policy prevented execution of action `%s` of trigger `%s` action work item %" PRIu64,
 676                     get_action_name(action),
 677                     get_trigger_name(work_item->trigger),
 678                     work_item->id);
 679                 ret = 0;
 680                 goto end;
 681         }
 682
 683         lttng_action_increase_execution_count(action);
 684         DBG("Executing action `%s` of trigger `%s` action work item %" PRIu64,
 685             get_action_name(action),
 686             get_trigger_name(work_item->trigger),
 687             work_item->id);
 688         ret = action_executors[action_type](executor, work_item, item);
 689 end:
 690         return ret;
 691 }
 692
 693 static int action_work_item_execute(struct action_executor *executor,
 694                                     struct action_work_item *work_item)
 695 {
 696         int ret;
 697         size_t count, i;
 698
 699         DBG("Starting execution of action work item %" PRIu64 " of trigger `%s`",
 700             work_item->id,
 701             get_trigger_name(work_item->trigger));
 702
 703         count = lttng_dynamic_array_get_count(&work_item->subitems);
 704         for (i = 0; i < count; i++) {
 705                 struct action_work_subitem *item;
 706
 707                 item = (action_work_subitem *) lttng_dynamic_array_get_element(&work_item->subitems,
 708                                                                                i);
 709                 ret = action_executor_generic_handler(executor, work_item, item);
 710                 if (ret) {
 711                         goto end;
 712                 }
 713         }
 714 end:
 715         DBG("Completed execution of action work item %" PRIu64 " of trigger `%s`",
 716             work_item->id,
 717             get_trigger_name(work_item->trigger));
 718         return ret;
 719 }
 720
 721 static void action_work_item_destroy(struct action_work_item *work_item)
 722 {
 723         lttng_trigger_put(work_item->trigger);
 724         lttng_evaluation_destroy(work_item->evaluation);
 725         notification_client_list_put(work_item->client_list);
 726         lttng_dynamic_array_reset(&work_item->subitems);
 727         free(work_item);
 728 }
 729
 730 static void *action_executor_thread(void *_data)
 731 {
 732         struct action_executor *executor = (action_executor *) _data;
 733
 734         LTTNG_ASSERT(executor);
 735
 736         health_register(the_health_sessiond, HEALTH_SESSIOND_TYPE_ACTION_EXECUTOR);
 737
 738         rcu_register_thread();
 739         rcu_thread_online();
 740
 741         DBG("Entering work execution loop");
 742         pthread_mutex_lock(&executor->work.lock);
 743         while (!executor->should_quit) {
 744                 int ret = 0;
 745                 struct action_work_item *work_item;
 746
 747                 health_code_update();
 748                 if (executor->work.pending_count == 0) {
 749                         health_poll_entry();
 750                         DBG("No work items enqueued, entering wait");
 751                         pthread_cond_wait(&executor->work.cond, &executor->work.lock);
 752                         DBG("Woke-up from wait");
 753                         health_poll_exit();
 754                         continue;
 755                 }
 756
 757                 /* Pop item from front of the list with work lock held. */
 758                 work_item = cds_list_first_entry(
 759                         &executor->work.list, struct action_work_item, list_node);
 760                 cds_list_del(&work_item->list_node);
 761                 executor->work.pending_count--;
 762
 763                 /*
 764                  * Work can be performed without holding the work lock,
 765                  * allowing new items to be queued.
 766                  */
 767                 pthread_mutex_unlock(&executor->work.lock);
 768
 769                 /* Execute item only if a trigger is registered. */
 770                 lttng_trigger_lock(work_item->trigger);
 771                 if (!lttng_trigger_is_registered(work_item->trigger)) {
 772                         const char *trigger_name = nullptr;
 773                         uid_t trigger_owner_uid;
 774                         enum lttng_trigger_status trigger_status;
 775
 776                         trigger_name = get_trigger_name(work_item->trigger);
 777
 778                         trigger_status =
 779                                 lttng_trigger_get_owner_uid(work_item->trigger, &trigger_owner_uid);
 780                         LTTNG_ASSERT(trigger_status == LTTNG_TRIGGER_STATUS_OK);
 781
 782                         DBG("Work item skipped since the associated trigger is no longer registered: work item id = %" PRIu64
 783                             ", trigger name = `%s`, trigger owner uid = %d",
 784                             work_item->id,
 785                             trigger_name,
 786                             (int) trigger_owner_uid);
 787                         ret = 0;
 788                         goto skip_execute;
 789                 }
 790
 791                 ret = action_work_item_execute(executor, work_item);
 792
 793         skip_execute:
 794                 lttng_trigger_unlock(work_item->trigger);
 795                 action_work_item_destroy(work_item);
 796                 if (ret) {
 797                         /* Fatal error. */
 798                         break;
 799                 }
 800
 801                 health_code_update();
 802                 pthread_mutex_lock(&executor->work.lock);
 803         }
 804
 805         if (executor->should_quit) {
 806                 pthread_mutex_unlock(&executor->work.lock);
 807         }
 808         DBG("Left work execution loop");
 809
 810         health_code_update();
 811
 812         rcu_thread_offline();
 813         rcu_unregister_thread();
 814         health_unregister(the_health_sessiond);
 815
 816         return nullptr;
 817 }
 818
 819 static bool shutdown_action_executor_thread(void *_data)
 820 {
 821         struct action_executor *executor = (action_executor *) _data;
 822
 823         pthread_mutex_lock(&executor->work.lock);
 824         executor->should_quit = true;
 825         pthread_cond_signal(&executor->work.cond);
 826         pthread_mutex_unlock(&executor->work.lock);
 827         return true;
 828 }
 829
 830 static void clean_up_action_executor_thread(void *_data)
 831 {
 832         struct action_executor *executor = (action_executor *) _data;
 833
 834         LTTNG_ASSERT(cds_list_empty(&executor->work.list));
 835
 836         pthread_mutex_destroy(&executor->work.lock);
 837         pthread_cond_destroy(&executor->work.cond);
 838         free(executor);
 839 }
 840
 841 struct action_executor *action_executor_create(struct notification_thread_handle *handle)
 842 {
 843         struct action_executor *executor = zmalloc<action_executor>();
 844
 845         if (!executor) {
 846                 goto end;
 847         }
 848
 849         CDS_INIT_LIST_HEAD(&executor->work.list);
 850         pthread_cond_init(&executor->work.cond, nullptr);
 851         pthread_mutex_init(&executor->work.lock, nullptr);
 852         executor->notification_thread_handle = handle;
 853
 854         executor->thread = lttng_thread_create(THREAD_NAME,
 855                                                action_executor_thread,
 856                                                shutdown_action_executor_thread,
 857                                                clean_up_action_executor_thread,
 858                                                executor);
 859 end:
 860         return executor;
 861 }
 862
 863 void action_executor_destroy(struct action_executor *executor)
 864 {
 865         struct action_work_item *work_item, *tmp;
 866
 867         /* TODO Wait for work list to drain? */
 868         lttng_thread_shutdown(executor->thread);
 869         pthread_mutex_lock(&executor->work.lock);
 870         if (executor->work.pending_count != 0) {
 871                 WARN("%" PRIu64
 872                      " trigger action%s still queued for execution and will be discarded",
 873                      executor->work.pending_count,
 874                      executor->work.pending_count == 1 ? " is" : "s are");
 875         }
 876
 877         cds_list_for_each_entry_safe (work_item, tmp, &executor->work.list, list_node) {
 878                 WARN("Discarding action work item %" PRIu64 " associated to trigger `%s`",
 879                      work_item->id,
 880                      get_trigger_name(work_item->trigger));
 881                 cds_list_del(&work_item->list_node);
 882                 action_work_item_destroy(work_item);
 883         }
 884         pthread_mutex_unlock(&executor->work.lock);
 885         lttng_thread_put(executor->thread);
 886 }
 887
 888 /* RCU read-lock must be held by the caller. */
 889 enum action_executor_status
 890 action_executor_enqueue_trigger(struct action_executor *executor,
 891                                 struct lttng_trigger *trigger,
 892                                 struct lttng_evaluation *evaluation,
 893                                 const struct lttng_credentials *object_creds,
 894                                 struct notification_client_list *client_list)
 895 {
 896         int ret;
 897         enum action_executor_status executor_status = ACTION_EXECUTOR_STATUS_OK;
 898         const uint64_t work_item_id = executor->next_work_item_id++;
 899         struct action_work_item *work_item;
 900         bool signal = false;
 901
 902         LTTNG_ASSERT(trigger);
 903         ASSERT_RCU_READ_LOCKED();
 904
 905         pthread_mutex_lock(&executor->work.lock);
 906         /* Check for queue overflow. */
 907         if (executor->work.pending_count >= MAX_QUEUED_WORK_COUNT) {
 908                 /* Most likely spammy, remove if it is the case. */
 909                 DBG("Refusing to enqueue action for trigger (overflow): trigger name = `%s`, work item id = %" PRIu64,
 910                     get_trigger_name(trigger),
 911                     work_item_id);
 912                 executor_status = ACTION_EXECUTOR_STATUS_OVERFLOW;
 913                 goto error_unlock;
 914         }
 915
 916         work_item = zmalloc<action_work_item>();
 917         if (!work_item) {
 918                 PERROR("Failed to allocate action executor work item: trigger name = `%s`",
 919                        get_trigger_name(trigger));
 920                 executor_status = ACTION_EXECUTOR_STATUS_ERROR;
 921                 goto error_unlock;
 922         }
 923
 924         lttng_trigger_get(trigger);
 925         if (client_list) {
 926                 const bool reference_acquired = notification_client_list_get(client_list);
 927
 928                 LTTNG_ASSERT(reference_acquired);
 929         }
 930
 931         work_item->id = work_item_id;
 932         work_item->trigger = trigger;
 933
 934         /* Ownership transferred to the work item. */
 935         work_item->evaluation = evaluation;
 936         evaluation = nullptr;
 937
 938         work_item->client_list = client_list;
 939         work_item->object_creds.is_set = !!object_creds;
 940         if (object_creds) {
 941                 work_item->object_creds.value = *object_creds;
 942         }
 943
 944         CDS_INIT_LIST_HEAD(&work_item->list_node);
 945
 946         /* Build the array of action work subitems for the passed trigger. */
 947         lttng_dynamic_array_init(&work_item->subitems,
 948                                  sizeof(struct action_work_subitem),
 949                                  action_work_subitem_destructor);
 950
 951         ret = populate_subitem_array_from_trigger(trigger, &work_item->subitems);
 952         if (ret) {
 953                 ERR("Failed to populate work item sub items on behalf of trigger: trigger name = `%s`",
 954                     get_trigger_name(trigger));
 955                 executor_status = ACTION_EXECUTOR_STATUS_ERROR;
 956                 goto error_unlock;
 957         }
 958
 959         cds_list_add_tail(&work_item->list_node, &executor->work.list);
 960         executor->work.pending_count++;
 961         DBG("Enqueued action for trigger: trigger name = `%s`, work item id = %" PRIu64,
 962             get_trigger_name(trigger),
 963             work_item_id);
 964         signal = true;
 965
 966 error_unlock:
 967         if (signal) {
 968                 pthread_cond_signal(&executor->work.cond);
 969         }
 970
 971         pthread_mutex_unlock(&executor->work.lock);
 972         lttng_evaluation_destroy(evaluation);
 973         return executor_status;
 974 }
 975
 976 static int add_action_to_subitem_array(struct lttng_action *action,
 977                                        struct lttng_dynamic_array *subitems)
 978 {
 979         int ret = 0;
 980         enum lttng_action_type type = lttng_action_get_type(action);
 981         const char *session_name = nullptr;
 982         enum lttng_action_status status;
 983         struct action_work_subitem subitem = {
 984                 .action = nullptr,
 985                 .context = {
 986                         .session_id = LTTNG_OPTIONAL_INIT_UNSET,
 987                 },
 988         };
 989
 990         LTTNG_ASSERT(action);
 991         LTTNG_ASSERT(subitems);
 992
 993         if (type == LTTNG_ACTION_TYPE_LIST) {
 994                 unsigned int count, i;
 995
 996                 status = lttng_action_list_get_count(action, &count);
 997                 LTTNG_ASSERT(status == LTTNG_ACTION_STATUS_OK);
 998
 999                 for (i = 0; i < count; i++) {
1000                         struct lttng_action *inner_action = nullptr;
1001
1002                         inner_action = lttng_action_list_borrow_mutable_at_index(action, i);
1003                         LTTNG_ASSERT(inner_action);
1004                         ret = add_action_to_subitem_array(inner_action, subitems);
1005                         if (ret) {
1006                                 goto end;
1007                         }
1008                 }
1009
1010                 /*
1011                  * Go directly to the end since there is no need to add the
1012                  * list action by itself to the subitems array.
1013                  */
1014                 goto end;
1015         }
1016
1017         /* Gather execution context. */
1018         switch (type) {
1019         case LTTNG_ACTION_TYPE_NOTIFY:
1020                 break;
1021         case LTTNG_ACTION_TYPE_START_SESSION:
1022                 status = lttng_action_start_session_get_session_name(action, &session_name);
1023                 LTTNG_ASSERT(status == LTTNG_ACTION_STATUS_OK);
1024                 break;
1025         case LTTNG_ACTION_TYPE_STOP_SESSION:
1026                 status = lttng_action_stop_session_get_session_name(action, &session_name);
1027                 LTTNG_ASSERT(status == LTTNG_ACTION_STATUS_OK);
1028                 break;
1029         case LTTNG_ACTION_TYPE_ROTATE_SESSION:
1030                 status = lttng_action_rotate_session_get_session_name(action, &session_name);
1031                 LTTNG_ASSERT(status == LTTNG_ACTION_STATUS_OK);
1032                 break;
1033         case LTTNG_ACTION_TYPE_SNAPSHOT_SESSION:
1034                 status = lttng_action_snapshot_session_get_session_name(action, &session_name);
1035                 LTTNG_ASSERT(status == LTTNG_ACTION_STATUS_OK);
1036                 break;
1037         case LTTNG_ACTION_TYPE_LIST:
1038         case LTTNG_ACTION_TYPE_UNKNOWN:
1039                 /* Fallthrough */
1040         default:
1041                 abort();
1042                 break;
1043         }
1044
1045         /*
1046          * Fetch the session execution context info as needed.
1047          * Note that we could decide to not add an action for which we know the
1048          * execution will not happen (i.e no session exists for that name). For
1049          * now we leave the decision to skip to the action executor for sake of
1050          * simplicity and consistency.
1051          */
1052         if (session_name != nullptr) {
1053                 uint64_t session_id;
1054
1055                 /*
1056                  * Instantaneous sampling of the session id if present.
1057                  *
1058                  * This method is preferred over `sessiond_find_by_name` then
1059                  * fetching the session'd id since `sessiond_find_by_name`
1060                  * requires the session list lock to be taken.
1061                  *
1062                  * Taking the session list lock can lead to a deadlock
1063                  * between the action executor and the notification thread
1064                  * (caller of add_action_to_subitem_array). It is okay if the
1065                  * session state changes between the enqueuing time and the
1066                  * execution time. The execution context is validated at
1067                  * execution time.
1068                  */
1069                 if (sample_session_id_by_name(session_name, &session_id)) {
1070                         LTTNG_OPTIONAL_SET(&subitem.context.session_id, session_id);
1071                 }
1072         }
1073
1074         /* Get a reference to the action. */
1075         lttng_action_get(action);
1076         subitem.action = action;
1077
1078         ret = lttng_dynamic_array_add_element(subitems, &subitem);
1079         if (ret) {
1080                 ERR("Failed to add work subitem to the subitem array");
1081                 lttng_action_put(action);
1082                 ret = -1;
1083                 goto end;
1084         }
1085
1086 end:
1087         return ret;
1088 }
1089
1090 static int populate_subitem_array_from_trigger(struct lttng_trigger *trigger,
1091                                                struct lttng_dynamic_array *subitems)
1092 {
1093         struct lttng_action *action;
1094
1095         action = lttng_trigger_get_action(trigger);
1096         LTTNG_ASSERT(action);
1097
1098         return add_action_to_subitem_array(action, subitems);
1099 }