src/bin/lttng-sessiond/event.c

   1 /*
   2  * Copyright (C) 2011 - David Goulet <david.goulet@polymtl.ca>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License, version 2 only,
   6  * as published by the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11  * GNU General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU General Public License along
  14  * with this program; if not, write to the Free Software Foundation, Inc.,
  15  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  16  */
  17
  18 #define _GNU_SOURCE
  19 #define _LGPL_SOURCE
  20 #include <errno.h>
  21 #include <urcu/list.h>
  22 #include <string.h>
  23
  24 #include <lttng/lttng.h>
  25 #include <common/error.h>
  26 #include <common/sessiond-comm/sessiond-comm.h>
  27
  28 #include "channel.h"
  29 #include "event.h"
  30 #include "kernel.h"
  31 #include "lttng-sessiond.h"
  32 #include "ust-ctl.h"
  33 #include "ust-app.h"
  34 #include "trace-kernel.h"
  35 #include "trace-ust.h"
  36 #include "agent.h"
  37
  38 /*
  39  * Add unique UST event based on the event name, filter bytecode and loglevel.
  40  */
  41 static void add_unique_ust_event(struct lttng_ht *ht,
  42                 struct ltt_ust_event *event)
  43 {
  44         struct cds_lfht_node *node_ptr;
  45         struct ltt_ust_ht_key key;
  46
  47         assert(ht);
  48         assert(ht->ht);
  49         assert(event);
  50
  51         key.name = event->attr.name;
  52         key.filter = (struct lttng_filter_bytecode *) event->filter;
  53         key.loglevel = event->attr.loglevel;
  54         key.exclusion = event->exclusion;
  55
  56         node_ptr = cds_lfht_add_unique(ht->ht,
  57                         ht->hash_fct(event->node.key, lttng_ht_seed),
  58                         trace_ust_ht_match_event, &key, &event->node.node);
  59         assert(node_ptr == &event->node.node);
  60 }
  61
  62 /*
  63  * Disable kernel tracepoint event for a channel from the kernel session.
  64  */
  65 int event_kernel_disable_event(struct ltt_kernel_channel *kchan,
  66                 char *event_name)
  67 {
  68         int ret;
  69         struct ltt_kernel_event *kevent;
  70
  71         assert(kchan);
  72
  73         kevent = trace_kernel_get_event_by_name(event_name, kchan,
  74                         LTTNG_EVENT_ALL);
  75         if (kevent == NULL) {
  76                 ret = LTTNG_ERR_NO_EVENT;
  77                 goto error;
  78         }
  79
  80         ret = kernel_disable_event(kevent);
  81         if (ret < 0) {
  82                 ret = LTTNG_ERR_KERN_DISABLE_FAIL;
  83                 goto error;
  84         }
  85
  86         DBG("Kernel event %s disable for channel %s.",
  87                         kevent->event->name, kchan->channel->name);
  88
  89         ret = LTTNG_OK;
  90
  91 error:
  92         return ret;
  93 }
  94
  95 /*
  96  * Disable kernel tracepoint events for a channel from the kernel session.
  97  */
  98 int event_kernel_disable_event_type(struct ltt_kernel_channel *kchan,
  99                 enum lttng_event_type type)
 100 {
 101         int ret;
 102         struct ltt_kernel_event *kevent;
 103
 104         assert(kchan);
 105
 106         /* For each event in the kernel session */
 107         cds_list_for_each_entry(kevent, &kchan->events_list.head, list) {
 108                 if (type != LTTNG_EVENT_ALL && kevent->type != type)
 109                         continue;
 110                 ret = kernel_disable_event(kevent);
 111                 if (ret < 0) {
 112                         /* We continue disabling the rest */
 113                         continue;
 114                 }
 115         }
 116         ret = LTTNG_OK;
 117         return ret;
 118 }
 119
 120 /*
 121  * Disable all kernel event for a channel from the kernel session.
 122  */
 123 int event_kernel_disable_event_all(struct ltt_kernel_channel *kchan)
 124 {
 125         return event_kernel_disable_event_type(kchan, LTTNG_EVENT_ALL);
 126 }
 127
 128 /*
 129  * Enable kernel tracepoint event for a channel from the kernel session.
 130  * We own filter_expression and filter.
 131  */
 132 int event_kernel_enable_event(struct ltt_kernel_channel *kchan,
 133                 struct lttng_event *event, char *filter_expression,
 134                 struct lttng_filter_bytecode *filter)
 135 {
 136         int ret;
 137         struct ltt_kernel_event *kevent;
 138
 139         assert(kchan);
 140         assert(event);
 141
 142         kevent = trace_kernel_find_event(event->name, kchan,
 143                         event->type, filter);
 144         if (kevent == NULL) {
 145                 ret = kernel_create_event(event, kchan,
 146                         filter_expression, filter);
 147                 /* We have passed ownership */
 148                 filter_expression = NULL;
 149                 filter = NULL;
 150                 if (ret < 0) {
 151                         switch (-ret) {
 152                         case EEXIST:
 153                                 ret = LTTNG_ERR_KERN_EVENT_EXIST;
 154                                 break;
 155                         case ENOSYS:
 156                                 ret = LTTNG_ERR_KERN_EVENT_ENOSYS;
 157                                 break;
 158                         default:
 159                                 ret = LTTNG_ERR_KERN_ENABLE_FAIL;
 160                                 break;
 161                         }
 162                         goto end;
 163                 }
 164         } else if (kevent->enabled == 0) {
 165                 ret = kernel_enable_event(kevent);
 166                 if (ret < 0) {
 167                         ret = LTTNG_ERR_KERN_ENABLE_FAIL;
 168                         goto end;
 169                 }
 170         } else {
 171                 /* At this point, the event is considered enabled */
 172                 ret = LTTNG_ERR_KERN_EVENT_EXIST;
 173                 goto end;
 174         }
 175
 176         ret = LTTNG_OK;
 177 end:
 178         free(filter_expression);
 179         free(filter);
 180         return ret;
 181 }
 182
 183 /*
 184  * ============================
 185  * UST : The Ultimate Frontier!
 186  * ============================
 187  */
 188
 189 /*
 190  * Enable all UST tracepoints for a channel from a UST session.
 191  */
 192 int event_ust_enable_all_tracepoints(struct ltt_ust_session *usess,
 193                 struct ltt_ust_channel *uchan,
 194                 char *filter_expression,
 195                 struct lttng_filter_bytecode *filter)
 196 {
 197         int ret, i, size;
 198         struct lttng_ht_iter iter;
 199         struct ltt_ust_event *uevent = NULL;
 200         struct lttng_event *events = NULL;
 201
 202         assert(usess);
 203         assert(uchan);
 204
 205         rcu_read_lock();
 206
 207         /* Enable existing events */
 208         cds_lfht_for_each_entry(uchan->events->ht, &iter.iter, uevent,
 209                         node.node) {
 210                 if (uevent->enabled == 0) {
 211                         ret = ust_app_enable_event_glb(usess, uchan, uevent);
 212                         if (ret < 0) {
 213                                 continue;
 214                         }
 215                         uevent->enabled = 1;
 216                 }
 217         }
 218
 219         /* Get all UST available events */
 220         size = ust_app_list_events(&events);
 221         if (size < 0) {
 222                 ret = LTTNG_ERR_UST_LIST_FAIL;
 223                 goto error;
 224         }
 225
 226         for (i = 0; i < size; i++) {
 227                 /*
 228                  * Check if event exist and if so, continue since it was enable
 229                  * previously.
 230                  */
 231                 uevent = trace_ust_find_event(uchan->events, events[i].name, filter,
 232                                 events[i].loglevel, NULL);
 233                 if (uevent != NULL) {
 234                         ret = ust_app_enable_event_pid(usess, uchan, uevent,
 235                                         events[i].pid);
 236                         if (ret < 0) {
 237                                 if (ret != -LTTNG_UST_ERR_EXIST) {
 238                                         ret = LTTNG_ERR_UST_ENABLE_FAIL;
 239                                         goto error;
 240                                 }
 241                         }
 242                         continue;
 243                 }
 244
 245                 /* Create ust event */
 246                 uevent = trace_ust_create_event(&events[i], filter_expression,
 247                         filter, NULL);
 248                 if (uevent == NULL) {
 249                         ret = LTTNG_ERR_FATAL;
 250                         goto error_destroy;
 251                 }
 252
 253                 /* Create event for the specific PID */
 254                 ret = ust_app_enable_event_pid(usess, uchan, uevent,
 255                                 events[i].pid);
 256                 if (ret < 0) {
 257                         if (ret == -LTTNG_UST_ERR_EXIST) {
 258                                 ret = LTTNG_ERR_UST_EVENT_EXIST;
 259                                 goto error;
 260                         } else {
 261                                 ret = LTTNG_ERR_UST_ENABLE_FAIL;
 262                                 goto error_destroy;
 263                         }
 264                 }
 265
 266                 uevent->enabled = 1;
 267                 /* Add ltt ust event to channel */
 268                 rcu_read_lock();
 269                 add_unique_ust_event(uchan->events, uevent);
 270                 rcu_read_unlock();
 271         }
 272         free(events);
 273
 274         rcu_read_unlock();
 275         return LTTNG_OK;
 276
 277 error_destroy:
 278         trace_ust_destroy_event(uevent);
 279
 280 error:
 281         free(events);
 282         rcu_read_unlock();
 283         return ret;
 284 }
 285
 286 /*
 287  * Enable UST tracepoint event for a channel from a UST session.
 288  * We own filter_expression, filter, and exclusion.
 289  */
 290 int event_ust_enable_tracepoint(struct ltt_ust_session *usess,
 291                 struct ltt_ust_channel *uchan, struct lttng_event *event,
 292                 char *filter_expression,
 293                 struct lttng_filter_bytecode *filter,
 294                 struct lttng_event_exclusion *exclusion)
 295 {
 296         int ret = LTTNG_OK, to_create = 0;
 297         struct ltt_ust_event *uevent;
 298
 299         assert(usess);
 300         assert(uchan);
 301         assert(event);
 302
 303         rcu_read_lock();
 304
 305         uevent = trace_ust_find_event(uchan->events, event->name, filter,
 306                         event->loglevel, exclusion);
 307         if (uevent == NULL) {
 308                 uevent = trace_ust_create_event(event, filter_expression,
 309                         filter, exclusion);
 310                 /* We have passed ownership */
 311                 filter_expression = NULL;
 312                 filter = NULL;
 313                 exclusion = NULL;
 314                 if (uevent == NULL) {
 315                         ret = LTTNG_ERR_UST_ENABLE_FAIL;
 316                         goto error;
 317                 }
 318
 319                 /* Valid to set it after the goto error since uevent is still NULL */
 320                 to_create = 1;
 321         }
 322
 323         if (uevent->enabled) {
 324                 /* It's already enabled so everything is OK */
 325                 ret = LTTNG_ERR_UST_EVENT_ENABLED;
 326                 goto end;
 327         }
 328
 329         uevent->enabled = 1;
 330
 331         if (to_create) {
 332                 /* Create event on all UST registered apps for session */
 333                 ret = ust_app_create_event_glb(usess, uchan, uevent);
 334         } else {
 335                 /* Enable event on all UST registered apps for session */
 336                 ret = ust_app_enable_event_glb(usess, uchan, uevent);
 337         }
 338
 339         if (ret < 0) {
 340                 if (ret == -LTTNG_UST_ERR_EXIST) {
 341                         ret = LTTNG_ERR_UST_EVENT_EXIST;
 342                         goto end;
 343                 } else {
 344                         ret = LTTNG_ERR_UST_ENABLE_FAIL;
 345                         goto error;
 346                 }
 347         }
 348
 349         if (to_create) {
 350                 /* Add ltt ust event to channel */
 351                 add_unique_ust_event(uchan->events, uevent);
 352         }
 353
 354         DBG("Event UST %s %s in channel %s", uevent->attr.name,
 355                         to_create ? "created" : "enabled", uchan->name);
 356
 357         ret = LTTNG_OK;
 358
 359 end:
 360         rcu_read_unlock();
 361         free(filter_expression);
 362         free(filter);
 363         free(exclusion);
 364         return ret;
 365
 366 error:
 367         /*
 368          * Only destroy event on creation time (not enabling time) because if the
 369          * event is found in the channel (to_create == 0), it means that at some
 370          * point the enable_event worked and it's thus valid to keep it alive.
 371          * Destroying it also implies that we also destroy it's shadow copy to sync
 372          * everyone up.
 373          */
 374         if (to_create) {
 375                 /* In this code path, the uevent was not added to the hash table */
 376                 trace_ust_destroy_event(uevent);
 377         }
 378         rcu_read_unlock();
 379         free(filter_expression);
 380         free(filter);
 381         free(exclusion);
 382         return ret;
 383 }
 384
 385 /*
 386  * Disable UST tracepoint of a channel from a UST session.
 387  */
 388 int event_ust_disable_tracepoint(struct ltt_ust_session *usess,
 389                 struct ltt_ust_channel *uchan, char *event_name)
 390 {
 391         int ret;
 392         struct ltt_ust_event *uevent;
 393         struct lttng_ht_node_str *node;
 394         struct lttng_ht_iter iter;
 395         struct lttng_ht *ht;
 396
 397         assert(usess);
 398         assert(uchan);
 399         assert(event_name);
 400
 401         ht = uchan->events;
 402
 403         rcu_read_lock();
 404
 405         /*
 406          * We use a custom lookup since we need the iterator for the next_duplicate
 407          * call in the do while loop below.
 408          */
 409         cds_lfht_lookup(ht->ht, ht->hash_fct((void *) event_name, lttng_ht_seed),
 410                         trace_ust_ht_match_event_by_name, event_name, &iter.iter);
 411         node = lttng_ht_iter_get_node_str(&iter);
 412         if (node == NULL) {
 413                 DBG2("Trace UST event NOT found by name %s", event_name);
 414                 ret = LTTNG_ERR_UST_EVENT_NOT_FOUND;
 415                 goto error;
 416         }
 417
 418         do {
 419                 uevent = caa_container_of(node, struct ltt_ust_event, node);
 420                 assert(uevent);
 421
 422                 if (uevent->enabled == 0) {
 423                         /* It's already disabled so everything is OK */
 424                         goto next;
 425                 }
 426
 427                 ret = ust_app_disable_event_glb(usess, uchan, uevent);
 428                 if (ret < 0 && ret != -LTTNG_UST_ERR_EXIST) {
 429                         ret = LTTNG_ERR_UST_DISABLE_FAIL;
 430                         goto error;
 431                 }
 432                 uevent->enabled = 0;
 433
 434                 DBG2("Event UST %s disabled in channel %s", uevent->attr.name,
 435                                 uchan->name);
 436
 437 next:
 438                 /* Get next duplicate event by name. */
 439                 cds_lfht_next_duplicate(ht->ht, trace_ust_ht_match_event_by_name,
 440                                 event_name, &iter.iter);
 441                 node = lttng_ht_iter_get_node_str(&iter);
 442         } while (node);
 443
 444         ret = LTTNG_OK;
 445
 446 error:
 447         rcu_read_unlock();
 448         return ret;
 449 }
 450
 451 /*
 452  * Disable all UST tracepoints for a channel from a UST session.
 453  */
 454 int event_ust_disable_all_tracepoints(struct ltt_ust_session *usess,
 455                 struct ltt_ust_channel *uchan)
 456 {
 457         int ret, i, size;
 458         struct lttng_ht_iter iter;
 459         struct ltt_ust_event *uevent = NULL;
 460         struct lttng_event *events = NULL;
 461
 462         assert(usess);
 463         assert(uchan);
 464
 465         rcu_read_lock();
 466
 467         /* Disabling existing events */
 468         cds_lfht_for_each_entry(uchan->events->ht, &iter.iter, uevent,
 469                         node.node) {
 470                 if (uevent->enabled == 1) {
 471                         ret = event_ust_disable_tracepoint(usess, uchan,
 472                                         uevent->attr.name);
 473                         if (ret < 0) {
 474                                 continue;
 475                         }
 476                 }
 477         }
 478
 479         /* Get all UST available events */
 480         size = ust_app_list_events(&events);
 481         if (size < 0) {
 482                 ret = LTTNG_ERR_UST_LIST_FAIL;
 483                 goto error;
 484         }
 485
 486         for (i = 0; i < size; i++) {
 487                 ret = event_ust_disable_tracepoint(usess, uchan,
 488                                 events[i].name);
 489                 if (ret != LTTNG_OK) {
 490                         /* Continue to disable the rest... */
 491                         continue;
 492                 }
 493         }
 494         free(events);
 495
 496         rcu_read_unlock();
 497         return LTTNG_OK;
 498
 499 error:
 500         free(events);
 501         rcu_read_unlock();
 502         return ret;
 503 }
 504
 505 /*
 506  * Enable all agent event for a given UST session.
 507  *
 508  * Return LTTNG_OK on success or else a LTTNG_ERR* code.
 509  */
 510 int event_agent_enable_all(struct ltt_ust_session *usess,
 511                 struct agent *agt, struct lttng_event *event,
 512                 struct lttng_filter_bytecode *filter)
 513 {
 514         int ret;
 515         struct agent_event *aevent;
 516         struct lttng_ht_iter iter;
 517
 518         assert(usess);
 519
 520         DBG("Event agent enabling ALL events for session %" PRIu64, usess->id);
 521
 522         /* Enable event on agent application through TCP socket. */
 523         ret = event_agent_enable(usess, agt, event, filter);
 524         if (ret != LTTNG_OK) {
 525                 goto error;
 526         }
 527
 528         /* Flag every event that they are now enabled. */
 529         rcu_read_lock();
 530         cds_lfht_for_each_entry(agt->events->ht, &iter.iter, aevent,
 531                         node.node) {
 532                 aevent->enabled = 1;
 533         }
 534         rcu_read_unlock();
 535
 536         ret = LTTNG_OK;
 537
 538 error:
 539         return ret;
 540 }
 541
 542 /*
 543  * Enable a single agent event for a given UST session.
 544  *
 545  * Return LTTNG_OK on success or else a LTTNG_ERR* code.
 546  */
 547 int event_agent_enable(struct ltt_ust_session *usess,
 548                 struct agent *agt, struct lttng_event *event,
 549                 struct lttng_filter_bytecode *filter)
 550 {
 551         int ret, created = 0;
 552         struct agent_event *aevent;
 553
 554         assert(usess);
 555         assert(event);
 556         assert(agt);
 557
 558         DBG("Event agent enabling %s for session %" PRIu64 " with loglevel type %d "
 559                         "and loglevel %d", event->name, usess->id, event->loglevel_type,
 560                         event->loglevel);
 561
 562         aevent = agent_find_event(event->name, event->loglevel, agt);
 563         if (!aevent) {
 564                 aevent = agent_create_event(event->name, filter);
 565                 if (!aevent) {
 566                         ret = LTTNG_ERR_NOMEM;
 567                         goto error;
 568                 }
 569                 aevent->loglevel = event->loglevel;
 570                 aevent->loglevel_type = event->loglevel_type;
 571                 created = 1;
 572         }
 573
 574         /* Already enabled? */
 575         if (aevent->enabled) {
 576                 goto end;
 577         }
 578
 579         ret = agent_enable_event(aevent, agt->domain);
 580         if (ret != LTTNG_OK) {
 581                 goto error;
 582         }
 583
 584         /* If the event was created prior to the enable, add it to the domain. */
 585         if (created) {
 586                 agent_add_event(aevent, agt);
 587         }
 588
 589 end:
 590         return LTTNG_OK;
 591
 592 error:
 593         if (created) {
 594                 agent_destroy_event(aevent);
 595         }
 596         return ret;
 597 }
 598
 599 /*
 600  * Return the agent default event name to use by testing if the process is root
 601  * or not. Return NULL on error.
 602  */
 603 const char *event_get_default_agent_ust_name(enum lttng_domain_type domain)
 604 {
 605         const char *default_event_name = NULL;
 606
 607         switch (domain) {
 608         case LTTNG_DOMAIN_LOG4J:
 609                 if (is_root) {
 610                         default_event_name = DEFAULT_SYS_LOG4J_EVENT_NAME;
 611                 } else {
 612                         default_event_name = DEFAULT_USER_LOG4J_EVENT_NAME;
 613                 }
 614                 break;
 615         case LTTNG_DOMAIN_JUL:
 616                 if (is_root) {
 617                         default_event_name = DEFAULT_SYS_JUL_EVENT_NAME;
 618                 } else {
 619                         default_event_name = DEFAULT_USER_JUL_EVENT_NAME;
 620                 }
 621                 break;
 622         case LTTNG_DOMAIN_PYTHON:
 623                 default_event_name = DEFAULT_USER_PYTHON_EVENT_NAME;
 624                 break;
 625         default:
 626                 assert(0);
 627         }
 628
 629         return default_event_name;
 630 }
 631
 632 /*
 633  * Disable a single agent event for a given UST session.
 634  *
 635  * Return LTTNG_OK on success or else a LTTNG_ERR* code.
 636  */
 637 int event_agent_disable(struct ltt_ust_session *usess, struct agent *agt,
 638                 char *event_name)
 639 {
 640         int ret;
 641         struct agent_event *aevent;
 642         struct ltt_ust_event *uevent = NULL;
 643         struct ltt_ust_channel *uchan = NULL;
 644         const char *ust_event_name, *ust_channel_name;
 645
 646         assert(agt);
 647         assert(usess);
 648         assert(event_name);
 649
 650         DBG("Event agent disabling %s for session %" PRIu64, event_name, usess->id);
 651
 652         aevent = agent_find_event_by_name(event_name, agt);
 653         if (!aevent) {
 654                 ret = LTTNG_ERR_UST_EVENT_NOT_FOUND;
 655                 goto error;
 656         }
 657
 658         /* Already disabled? */
 659         if (!aevent->enabled) {
 660                 goto end;
 661         }
 662
 663         if (agt->domain == LTTNG_DOMAIN_JUL) {
 664                 ust_channel_name = DEFAULT_JUL_CHANNEL_NAME;
 665         } else if (agt->domain == LTTNG_DOMAIN_LOG4J) {
 666                 ust_channel_name = DEFAULT_LOG4J_CHANNEL_NAME;
 667         } else if (agt->domain == LTTNG_DOMAIN_PYTHON) {
 668                 ust_channel_name = DEFAULT_PYTHON_CHANNEL_NAME;
 669         } else {
 670                 ret = LTTNG_ERR_INVALID;
 671                 goto error;
 672         }
 673
 674         /*
 675          * Disable it on the UST side. First get the channel reference then find
 676          * the event and finally disable it.
 677          */
 678         uchan = trace_ust_find_channel_by_name(usess->domain_global.channels,
 679                         (char *) ust_channel_name);
 680         if (!uchan) {
 681                 ret = LTTNG_ERR_UST_CHAN_NOT_FOUND;
 682                 goto error;
 683         }
 684
 685         ust_event_name = event_get_default_agent_ust_name(agt->domain);
 686         if (!ust_event_name) {
 687                 ret = LTTNG_ERR_FATAL;
 688                 goto error;
 689         }
 690
 691         /*
 692          * The loglevel is hardcoded with 0 here since the agent ust event is set
 693          * with the loglevel type to ALL thus the loglevel stays 0. The event's
 694          * filter is the one handling the loglevel for agent.
 695          */
 696         uevent = trace_ust_find_event(uchan->events, (char *) ust_event_name,
 697                         aevent->filter, 0, NULL);
 698         /* If the agent event exists, it must be available on the UST side. */
 699         assert(uevent);
 700
 701         ret = ust_app_disable_event_glb(usess, uchan, uevent);
 702         if (ret < 0 && ret != -LTTNG_UST_ERR_EXIST) {
 703                 ret = LTTNG_ERR_UST_DISABLE_FAIL;
 704                 goto error;
 705         }
 706
 707         /*
 708          * Flag event that it's disabled so the shadow copy on the ust app side
 709          * will disable it if an application shows up.
 710          */
 711         uevent->enabled = 0;
 712
 713         ret = agent_disable_event(aevent, agt->domain);
 714         if (ret != LTTNG_OK) {
 715                 goto error;
 716         }
 717
 718 end:
 719         return LTTNG_OK;
 720
 721 error:
 722         return ret;
 723 }
 724 /*
 725  * Disable all agent event for a given UST session.
 726  *
 727  * Return LTTNG_OK on success or else a LTTNG_ERR* code.
 728  */
 729 int event_agent_disable_all(struct ltt_ust_session *usess,
 730                 struct agent *agt)
 731 {
 732         int ret;
 733         struct agent_event *aevent;
 734         struct lttng_ht_iter iter;
 735
 736         assert(agt);
 737         assert(usess);
 738
 739         /*
 740          * Disable event on agent application. Continue to disable all other events
 741          * if the * event is not found.
 742          */
 743         ret = event_agent_disable(usess, agt, "*");
 744         if (ret != LTTNG_OK && ret != LTTNG_ERR_UST_EVENT_NOT_FOUND) {
 745                 goto error;
 746         }
 747
 748         /* Flag every event that they are now enabled. */
 749         rcu_read_lock();
 750         cds_lfht_for_each_entry(agt->events->ht, &iter.iter, aevent,
 751                         node.node) {
 752                 if (!aevent->enabled) {
 753                         continue;
 754                 }
 755
 756                 ret = event_agent_disable(usess, agt, aevent->name);
 757                 if (ret != LTTNG_OK) {
 758                         rcu_read_unlock();
 759                         goto error;
 760                 }
 761         }
 762         rcu_read_unlock();
 763
 764         ret = LTTNG_OK;
 765
 766 error:
 767         return ret;
 768 }