src/bin/lttng-sessiond/agent.c

   1 /*
   2  * Copyright (C) 2013 - David Goulet <dgoulet@efficios.com>
   3  *
   4  * This program is free software; you can redistribute it and/or modify it
   5  * under the terms of the GNU General Public License, version 2 only, as
   6  * published by the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it will be useful, but WITHOUT
   9  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  10  * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
  11  * more details.
  12  *
  13  * You should have received a copy of the GNU General Public License along with
  14  * this program; if not, write to the Free Software Foundation, Inc., 51
  15  * Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  16  */
  17
  18 #define _GNU_SOURCE
  19 #include <assert.h>
  20 #include <urcu/uatomic.h>
  21
  22 #include <common/common.h>
  23 #include <common/sessiond-comm/agent.h>
  24
  25 #include <common/compat/endian.h>
  26
  27 #include "agent.h"
  28 #include "ust-app.h"
  29 #include "utils.h"
  30
  31 /*
  32  * Match function for the events hash table lookup by name.
  33  */
  34 static int ht_match_event_by_name(struct cds_lfht_node *node,
  35                 const void *_key)
  36 {
  37         struct agent_event *event;
  38         const struct agent_ht_key *key;
  39
  40         assert(node);
  41         assert(_key);
  42
  43         event = caa_container_of(node, struct agent_event, node.node);
  44         key = _key;
  45
  46         /* Match 1 elements of the key: name. */
  47
  48         /* Event name */
  49         if (strncmp(event->name, key->name, sizeof(event->name)) != 0) {
  50                 goto no_match;
  51         }
  52         /* Match. */
  53         return 1;
  54
  55 no_match:
  56         return 0;
  57 }
  58
  59 /*
  60  * Match function for the events hash table lookup by name and loglevel.
  61  */
  62 static int ht_match_event(struct cds_lfht_node *node,
  63                 const void *_key)
  64 {
  65         struct agent_event *event;
  66         const struct agent_ht_key *key;
  67
  68         assert(node);
  69         assert(_key);
  70
  71         event = caa_container_of(node, struct agent_event, node.node);
  72         key = _key;
  73
  74         /* Match 2 elements of the key: name and loglevel. */
  75
  76         /* Event name */
  77         if (strncmp(event->name, key->name, sizeof(event->name)) != 0) {
  78                 goto no_match;
  79         }
  80
  81         if (event->loglevel != key->loglevel) {
  82                 if (event->loglevel_type == LTTNG_EVENT_LOGLEVEL_ALL &&
  83                                 key->loglevel == 0 && event->loglevel == -1) {
  84                         goto match;
  85                 }
  86                 goto no_match;
  87         }
  88 match:
  89         return 1;
  90
  91 no_match:
  92         return 0;
  93 }
  94
  95 /*
  96  * Add unique agent event based on the event name and loglevel.
  97  */
  98 static void add_unique_agent_event(struct lttng_ht *ht,
  99                 struct agent_event *event)
 100 {
 101         struct cds_lfht_node *node_ptr;
 102         struct agent_ht_key key;
 103
 104         assert(ht);
 105         assert(ht->ht);
 106         assert(event);
 107
 108         key.name = event->name;
 109         key.loglevel = event->loglevel;
 110
 111         node_ptr = cds_lfht_add_unique(ht->ht,
 112                         ht->hash_fct(event->node.key, lttng_ht_seed),
 113                         ht_match_event, &key, &event->node.node);
 114         assert(node_ptr == &event->node.node);
 115 }
 116
 117 /*
 118  * URCU delayed agent event reclaim.
 119  */
 120 static void destroy_event_agent_rcu(struct rcu_head *head)
 121 {
 122         struct lttng_ht_node_str *node =
 123                 caa_container_of(head, struct lttng_ht_node_str, head);
 124         struct agent_event *event =
 125                 caa_container_of(node, struct agent_event, node);
 126
 127         agent_destroy_event(event);
 128 }
 129
 130 /*
 131  * URCU delayed agent app reclaim.
 132  */
 133 static void destroy_app_agent_rcu(struct rcu_head *head)
 134 {
 135         struct lttng_ht_node_ulong *node =
 136                 caa_container_of(head, struct lttng_ht_node_ulong, head);
 137         struct agent_app *app =
 138                 caa_container_of(node, struct agent_app, node);
 139
 140         free(app);
 141 }
 142
 143 /*
 144  * Communication with the agent. Send the message header to the given socket in
 145  * big endian.
 146  *
 147  * Return 0 on success or else a negative errno message of sendmsg() op.
 148  */
 149 static int send_header(struct lttcomm_sock *sock, uint64_t data_size,
 150                 uint32_t cmd, uint32_t cmd_version)
 151 {
 152         int ret;
 153         ssize_t size;
 154         struct lttcomm_agent_hdr msg;
 155
 156         assert(sock);
 157
 158         memset(&msg, 0, sizeof(msg));
 159         msg.data_size = htobe64(data_size);
 160         msg.cmd = htobe32(cmd);
 161         msg.cmd_version = htobe32(cmd_version);
 162
 163         size = sock->ops->sendmsg(sock, &msg, sizeof(msg), 0);
 164         if (size < sizeof(msg)) {
 165                 ret = -errno;
 166                 goto error;
 167         }
 168         ret = 0;
 169
 170 error:
 171         return ret;
 172 }
 173
 174 /*
 175  * Communication call with the agent. Send the payload to the given socket. The
 176  * header MUST be sent prior to this call.
 177  *
 178  * Return 0 on success or else a negative errno value of sendmsg() op.
 179  */
 180 static int send_payload(struct lttcomm_sock *sock, void *data,
 181                 size_t size)
 182 {
 183         int ret;
 184         ssize_t len;
 185
 186         assert(sock);
 187         assert(data);
 188
 189         len = sock->ops->sendmsg(sock, data, size, 0);
 190         if (len < size) {
 191                 ret = -errno;
 192                 goto error;
 193         }
 194         ret = 0;
 195
 196 error:
 197         return ret;
 198 }
 199
 200 /*
 201  * Communication call with the agent. Receive reply from the agent using the
 202  * given socket.
 203  *
 204  * Return 0 on success or else a negative errno value from recvmsg() op.
 205  */
 206 static int recv_reply(struct lttcomm_sock *sock, void *buf, size_t size)
 207 {
 208         int ret;
 209         ssize_t len;
 210
 211         assert(sock);
 212         assert(buf);
 213
 214         len = sock->ops->recvmsg(sock, buf, size, 0);
 215         if (len < size) {
 216                 ret = -errno;
 217                 goto error;
 218         }
 219         ret = 0;
 220
 221 error:
 222         return ret;
 223 }
 224
 225 /*
 226  * Internal event listing for a given app. Populate events.
 227  *
 228  * Return number of element in the list or else a negative LTTNG_ERR* code.
 229  * On success, the caller is responsible for freeing the memory
 230  * allocated for "events".
 231  */
 232 static ssize_t list_events(struct agent_app *app, struct lttng_event **events)
 233 {
 234         int ret, i, len = 0, offset = 0;
 235         uint32_t nb_event;
 236         size_t data_size;
 237         struct lttng_event *tmp_events = NULL;
 238         struct lttcomm_agent_list_reply *reply = NULL;
 239         struct lttcomm_agent_list_reply_hdr reply_hdr;
 240
 241         assert(app);
 242         assert(app->sock);
 243         assert(events);
 244
 245         DBG2("Agent listing events for app pid: %d and socket %d", app->pid,
 246                         app->sock->fd);
 247
 248         ret = send_header(app->sock, 0, AGENT_CMD_LIST, 0);
 249         if (ret < 0) {
 250                 goto error_io;
 251         }
 252
 253         /* Get list header so we know how much we'll receive. */
 254         ret = recv_reply(app->sock, &reply_hdr, sizeof(reply_hdr));
 255         if (ret < 0) {
 256                 goto error_io;
 257         }
 258
 259         switch (be32toh(reply_hdr.ret_code)) {
 260         case AGENT_RET_CODE_SUCCESS:
 261                 data_size = be32toh(reply_hdr.data_size) + sizeof(*reply);
 262                 break;
 263         default:
 264                 ERR("Agent returned an unknown code: %" PRIu32,
 265                                 be32toh(reply_hdr.ret_code));
 266                 ret = LTTNG_ERR_FATAL;
 267                 goto error;
 268         }
 269
 270         reply = zmalloc(data_size);
 271         if (!reply) {
 272                 ret = LTTNG_ERR_NOMEM;
 273                 goto error;
 274         }
 275
 276         /* Get the list with the appropriate data size. */
 277         ret = recv_reply(app->sock, reply, data_size);
 278         if (ret < 0) {
 279                 goto error_io;
 280         }
 281
 282         nb_event = be32toh(reply->nb_event);
 283         tmp_events = zmalloc(sizeof(*tmp_events) * nb_event);
 284         if (!tmp_events) {
 285                 ret = LTTNG_ERR_NOMEM;
 286                 goto error;
 287         }
 288
 289         for (i = 0; i < nb_event; i++) {
 290                 offset += len;
 291                 strncpy(tmp_events[i].name, reply->payload + offset,
 292                                 sizeof(tmp_events[i].name));
 293                 tmp_events[i].pid = app->pid;
 294                 tmp_events[i].enabled = -1;
 295                 len = strlen(reply->payload + offset) + 1;
 296         }
 297
 298         *events = tmp_events;
 299
 300         free(reply);
 301         return nb_event;
 302
 303 error_io:
 304         ret = LTTNG_ERR_UST_LIST_FAIL;
 305 error:
 306         free(reply);
 307         free(tmp_events);
 308         return -ret;
 309
 310 }
 311
 312 /*
 313  * Internal enable agent event on a agent application. This function
 314  * communicates with the agent to enable a given event.
 315  *
 316  * Return LTTNG_OK on success or else a LTTNG_ERR* code.
 317  */
 318 static int enable_event(struct agent_app *app, struct agent_event *event)
 319 {
 320         int ret;
 321         uint64_t data_size;
 322         struct lttcomm_agent_enable msg;
 323         struct lttcomm_agent_generic_reply reply;
 324
 325         assert(app);
 326         assert(app->sock);
 327         assert(event);
 328
 329         DBG2("Agent enabling event %s for app pid: %d and socket %d", event->name,
 330                         app->pid, app->sock->fd);
 331
 332         data_size = sizeof(msg);
 333
 334         ret = send_header(app->sock, data_size, AGENT_CMD_ENABLE, 0);
 335         if (ret < 0) {
 336                 goto error_io;
 337         }
 338
 339         memset(&msg, 0, sizeof(msg));
 340         msg.loglevel = event->loglevel;
 341         msg.loglevel_type = event->loglevel_type;
 342         strncpy(msg.name, event->name, sizeof(msg.name));
 343         ret = send_payload(app->sock, &msg, sizeof(msg));
 344         if (ret < 0) {
 345                 goto error_io;
 346         }
 347
 348         ret = recv_reply(app->sock, &reply, sizeof(reply));
 349         if (ret < 0) {
 350                 goto error_io;
 351         }
 352
 353         switch (be32toh(reply.ret_code)) {
 354         case AGENT_RET_CODE_SUCCESS:
 355                 break;
 356         case AGENT_RET_CODE_UNKNOWN_NAME:
 357                 ret = LTTNG_ERR_UST_EVENT_NOT_FOUND;
 358                 goto error;
 359         default:
 360                 ERR("Agent returned an unknown code: %" PRIu32,
 361                                 be32toh(reply.ret_code));
 362                 ret = LTTNG_ERR_FATAL;
 363                 goto error;
 364         }
 365
 366         return LTTNG_OK;
 367
 368 error_io:
 369         ret = LTTNG_ERR_UST_ENABLE_FAIL;
 370 error:
 371         return ret;
 372 }
 373
 374 /*
 375  * Internal disable agent event call on a agent application. This function
 376  * communicates with the agent to disable a given event.
 377  *
 378  * Return LTTNG_OK on success or else a LTTNG_ERR* code.
 379  */
 380 static int disable_event(struct agent_app *app, struct agent_event *event)
 381 {
 382         int ret;
 383         uint64_t data_size;
 384         struct lttcomm_agent_disable msg;
 385         struct lttcomm_agent_generic_reply reply;
 386
 387         assert(app);
 388         assert(app->sock);
 389         assert(event);
 390
 391         DBG2("Agent disabling event %s for app pid: %d and socket %d", event->name,
 392                         app->pid, app->sock->fd);
 393
 394         data_size = sizeof(msg);
 395
 396         ret = send_header(app->sock, data_size, AGENT_CMD_DISABLE, 0);
 397         if (ret < 0) {
 398                 goto error_io;
 399         }
 400
 401         memset(&msg, 0, sizeof(msg));
 402         strncpy(msg.name, event->name, sizeof(msg.name));
 403         ret = send_payload(app->sock, &msg, sizeof(msg));
 404         if (ret < 0) {
 405                 goto error_io;
 406         }
 407
 408         ret = recv_reply(app->sock, &reply, sizeof(reply));
 409         if (ret < 0) {
 410                 goto error_io;
 411         }
 412
 413         switch (be32toh(reply.ret_code)) {
 414         case AGENT_RET_CODE_SUCCESS:
 415                 break;
 416         case AGENT_RET_CODE_UNKNOWN_NAME:
 417                 ret = LTTNG_ERR_UST_EVENT_NOT_FOUND;
 418                 goto error;
 419         default:
 420                 ERR("Agent returned an unknown code: %" PRIu32,
 421                                 be32toh(reply.ret_code));
 422                 ret = LTTNG_ERR_FATAL;
 423                 goto error;
 424         }
 425
 426         return LTTNG_OK;
 427
 428 error_io:
 429         ret = LTTNG_ERR_UST_DISABLE_FAIL;
 430 error:
 431         return ret;
 432 }
 433
 434 /*
 435  * Send back the registration DONE command to a given agent application.
 436  *
 437  * Return 0 on success or else a negative value.
 438  */
 439 int agent_send_registration_done(struct agent_app *app)
 440 {
 441         assert(app);
 442         assert(app->sock);
 443
 444         DBG("Agent sending registration done to app socket %d", app->sock->fd);
 445
 446         return send_header(app->sock, 0, AGENT_CMD_REG_DONE, 1);
 447 }
 448
 449 /*
 450  * Enable agent event on every agent applications registered with the session
 451  * daemon.
 452  *
 453  * Return LTTNG_OK on success or else a LTTNG_ERR* code.
 454  */
 455 int agent_enable_event(struct agent_event *event,
 456                 enum lttng_domain_type domain)
 457 {
 458         int ret;
 459         struct agent_app *app;
 460         struct lttng_ht_iter iter;
 461
 462         assert(event);
 463
 464         rcu_read_lock();
 465
 466         cds_lfht_for_each_entry(agent_apps_ht_by_sock->ht, &iter.iter, app,
 467                         node.node) {
 468                 if (app->domain != domain) {
 469                         continue;
 470                 }
 471
 472                 /* Enable event on agent application through TCP socket. */
 473                 ret = enable_event(app, event);
 474                 if (ret != LTTNG_OK) {
 475                         goto error;
 476                 }
 477         }
 478
 479         event->enabled = 1;
 480         ret = LTTNG_OK;
 481
 482 error:
 483         rcu_read_unlock();
 484         return ret;
 485 }
 486
 487 /*
 488  * Disable agent event on every agent applications registered with the session
 489  * daemon.
 490  *
 491  * Return LTTNG_OK on success or else a LTTNG_ERR* code.
 492  */
 493 int agent_disable_event(struct agent_event *event,
 494                 enum lttng_domain_type domain)
 495 {
 496         int ret = LTTNG_OK;
 497         struct agent_app *app;
 498         struct lttng_ht_iter iter;
 499
 500         assert(event);
 501         if (!event->enabled) {
 502                 goto end;
 503         }
 504
 505         rcu_read_lock();
 506
 507         cds_lfht_for_each_entry(agent_apps_ht_by_sock->ht, &iter.iter, app,
 508                         node.node) {
 509                 if (app->domain != domain) {
 510                         continue;
 511                 }
 512
 513                 /* Enable event on agent application through TCP socket. */
 514                 ret = disable_event(app, event);
 515                 if (ret != LTTNG_OK) {
 516                         goto error;
 517                 }
 518         }
 519
 520         event->enabled = 0;
 521
 522 error:
 523         rcu_read_unlock();
 524 end:
 525         return ret;
 526 }
 527
 528 /*
 529  * Ask every agent for the list of possible event. Events is allocated with the
 530  * events of every agent application.
 531  *
 532  * Return the number of events or else a negative value.
 533  */
 534 int agent_list_events(struct lttng_event **events,
 535                 enum lttng_domain_type domain)
 536 {
 537         int ret;
 538         size_t nbmem, count = 0;
 539         struct agent_app *app;
 540         struct lttng_event *tmp_events = NULL;
 541         struct lttng_ht_iter iter;
 542
 543         assert(events);
 544
 545         nbmem = UST_APP_EVENT_LIST_SIZE;
 546         tmp_events = zmalloc(nbmem * sizeof(*tmp_events));
 547         if (!tmp_events) {
 548                 PERROR("zmalloc agent list events");
 549                 ret = -ENOMEM;
 550                 goto error;
 551         }
 552
 553         rcu_read_lock();
 554         cds_lfht_for_each_entry(agent_apps_ht_by_sock->ht, &iter.iter, app,
 555                         node.node) {
 556                 ssize_t nb_ev;
 557                 struct lttng_event *agent_events;
 558
 559                 /* Skip domain not asked by the list. */
 560                 if (app->domain != domain) {
 561                         continue;
 562                 }
 563
 564                 nb_ev = list_events(app, &agent_events);
 565                 if (nb_ev < 0) {
 566                         ret = nb_ev;
 567                         goto error_unlock;
 568                 }
 569
 570                 if (count + nb_ev > nbmem) {
 571                         /* In case the realloc fails, we free the memory */
 572                         struct lttng_event *new_tmp_events;
 573                         size_t new_nbmem;
 574
 575                         new_nbmem = max_t(size_t, count + nb_ev, nbmem << 1);
 576                         DBG2("Reallocating agent event list from %zu to %zu entries",
 577                                         nbmem, new_nbmem);
 578                         new_tmp_events = realloc(tmp_events,
 579                                 new_nbmem * sizeof(*new_tmp_events));
 580                         if (!new_tmp_events) {
 581                                 PERROR("realloc agent events");
 582                                 ret = -ENOMEM;
 583                                 free(agent_events);
 584                                 goto error_unlock;
 585                         }
 586                         /* Zero the new memory */
 587                         memset(new_tmp_events + nbmem, 0,
 588                                 (new_nbmem - nbmem) * sizeof(*new_tmp_events));
 589                         nbmem = new_nbmem;
 590                         tmp_events = new_tmp_events;
 591                 }
 592                 memcpy(tmp_events + count, agent_events,
 593                         nb_ev * sizeof(*tmp_events));
 594                 free(agent_events);
 595                 count += nb_ev;
 596         }
 597         rcu_read_unlock();
 598
 599         ret = count;
 600         *events = tmp_events;
 601         return ret;
 602
 603 error_unlock:
 604         rcu_read_unlock();
 605 error:
 606         free(tmp_events);
 607         return ret;
 608 }
 609
 610 /*
 611  * Create a agent app object using the given PID.
 612  *
 613  * Return newly allocated object or else NULL on error.
 614  */
 615 struct agent_app *agent_create_app(pid_t pid, enum lttng_domain_type domain,
 616                 struct lttcomm_sock *sock)
 617 {
 618         struct agent_app *app;
 619
 620         assert(sock);
 621
 622         app = zmalloc(sizeof(*app));
 623         if (!app) {
 624                 PERROR("zmalloc agent create");
 625                 goto error;
 626         }
 627
 628         app->pid = pid;
 629         app->domain = domain;
 630         app->sock = sock;
 631         lttng_ht_node_init_ulong(&app->node, (unsigned long) app->sock->fd);
 632
 633 error:
 634         return app;
 635 }
 636
 637 /*
 638  * Lookup agent app by socket in the global hash table.
 639  *
 640  * RCU read side lock MUST be acquired.
 641  *
 642  * Return object if found else NULL.
 643  */
 644 struct agent_app *agent_find_app_by_sock(int sock)
 645 {
 646         struct lttng_ht_node_ulong *node;
 647         struct lttng_ht_iter iter;
 648         struct agent_app *app;
 649
 650         assert(sock >= 0);
 651
 652         lttng_ht_lookup(agent_apps_ht_by_sock, (void *)((unsigned long) sock), &iter);
 653         node = lttng_ht_iter_get_node_ulong(&iter);
 654         if (node == NULL) {
 655                 goto error;
 656         }
 657         app = caa_container_of(node, struct agent_app, node);
 658
 659         DBG3("Agent app pid %d found by sock %d.", app->pid, sock);
 660         return app;
 661
 662 error:
 663         DBG3("Agent app NOT found by sock %d.", sock);
 664         return NULL;
 665 }
 666
 667 /*
 668  * Add agent application object to the global hash table.
 669  */
 670 void agent_add_app(struct agent_app *app)
 671 {
 672         assert(app);
 673
 674         DBG3("Agent adding app sock: %d and pid: %d to ht", app->sock->fd, app->pid);
 675
 676         rcu_read_lock();
 677         lttng_ht_add_unique_ulong(agent_apps_ht_by_sock, &app->node);
 678         rcu_read_unlock();
 679 }
 680
 681 /*
 682  * Delete agent application from the global hash table.
 683  *
 684  * rcu_read_lock() must be held by the caller.
 685  */
 686 void agent_delete_app(struct agent_app *app)
 687 {
 688         int ret;
 689         struct lttng_ht_iter iter;
 690
 691         assert(app);
 692
 693         DBG3("Agent deleting app pid: %d and sock: %d", app->pid, app->sock->fd);
 694
 695         iter.iter.node = &app->node.node;
 696         ret = lttng_ht_del(agent_apps_ht_by_sock, &iter);
 697         assert(!ret);
 698 }
 699
 700 /*
 701  * Destroy a agent application object by detaching it from its corresponding
 702  * UST app if one is connected by closing the socket. Finally, perform a
 703  * delayed memory reclaim.
 704  */
 705 void agent_destroy_app(struct agent_app *app)
 706 {
 707         assert(app);
 708
 709         if (app->sock) {
 710                 app->sock->ops->close(app->sock);
 711                 lttcomm_destroy_sock(app->sock);
 712         }
 713
 714         call_rcu(&app->node.head, destroy_app_agent_rcu);
 715 }
 716
 717 /*
 718  * Initialize an already allocated agent object.
 719  *
 720  * Return 0 on success or else a negative errno value.
 721  */
 722 int agent_init(struct agent *agt)
 723 {
 724         int ret;
 725
 726         assert(agt);
 727
 728         agt->events = lttng_ht_new(0, LTTNG_HT_TYPE_STRING);
 729         if (!agt->events) {
 730                 ret = -ENOMEM;
 731                 goto error;
 732         }
 733         lttng_ht_node_init_u64(&agt->node, agt->domain);
 734
 735         return 0;
 736
 737 error:
 738         return ret;
 739 }
 740
 741 /*
 742  * Add agent object to the given hash table.
 743  */
 744 void agent_add(struct agent *agt, struct lttng_ht *ht)
 745 {
 746         assert(agt);
 747         assert(ht);
 748
 749         DBG3("Agent adding from domain %d", agt->domain);
 750
 751         rcu_read_lock();
 752         lttng_ht_add_unique_u64(ht, &agt->node);
 753         rcu_read_unlock();
 754 }
 755
 756 /*
 757  * Create an agent object for the given domain.
 758  *
 759  * Return the allocated agent or NULL on error.
 760  */
 761 struct agent *agent_create(enum lttng_domain_type domain)
 762 {
 763         int ret;
 764         struct agent *agt;
 765
 766         agt = zmalloc(sizeof(*agt));
 767         if (!agt) {
 768                 goto error;
 769         }
 770         agt->domain = domain;
 771
 772         ret = agent_init(agt);
 773         if (ret < 0) {
 774                 free(agt);
 775                 agt = NULL;
 776                 goto error;
 777         }
 778
 779 error:
 780         return agt;
 781 }
 782
 783 /*
 784  * Create a newly allocated agent event data structure. If name is valid, it's
 785  * copied into the created event.
 786  *
 787  * Return a new object else NULL on error.
 788  */
 789 struct agent_event *agent_create_event(const char *name,
 790                 struct lttng_filter_bytecode *filter)
 791 {
 792         struct agent_event *event;
 793
 794         DBG3("Agent create new event with name %s", name);
 795
 796         event = zmalloc(sizeof(*event));
 797         if (!event) {
 798                 goto error;
 799         }
 800
 801         if (name) {
 802                 strncpy(event->name, name, sizeof(event->name));
 803                 event->name[sizeof(event->name) - 1] = '\0';
 804                 lttng_ht_node_init_str(&event->node, event->name);
 805         }
 806
 807         if (filter) {
 808                 event->filter = filter;
 809         }
 810
 811 error:
 812         return event;
 813 }
 814
 815 /*
 816  * Unique add of a agent event to an agent object.
 817  */
 818 void agent_add_event(struct agent_event *event, struct agent *agt)
 819 {
 820         assert(event);
 821         assert(agt);
 822         assert(agt->events);
 823
 824         DBG3("Agent adding event %s", event->name);
 825
 826         rcu_read_lock();
 827         add_unique_agent_event(agt->events, event);
 828         rcu_read_unlock();
 829         agt->being_used = 1;
 830 }
 831
 832 /*
 833  * Find a agent event in the given agent using name.
 834  *
 835  * RCU read side lock MUST be acquired.
 836  *
 837  * Return object if found else NULL.
 838  */
 839 struct agent_event *agent_find_event_by_name(const char *name,
 840                 struct agent *agt)
 841 {
 842         struct lttng_ht_node_str *node;
 843         struct lttng_ht_iter iter;
 844         struct lttng_ht *ht;
 845         struct agent_ht_key key;
 846
 847         assert(name);
 848         assert(agt);
 849         assert(agt->events);
 850
 851         ht = agt->events;
 852         key.name = name;
 853
 854         cds_lfht_lookup(ht->ht, ht->hash_fct((void *) name, lttng_ht_seed),
 855                         ht_match_event_by_name, &key, &iter.iter);
 856         node = lttng_ht_iter_get_node_str(&iter);
 857         if (node == NULL) {
 858                 goto error;
 859         }
 860
 861         DBG3("Agent event found %s by name.", name);
 862         return caa_container_of(node, struct agent_event, node);
 863
 864 error:
 865         DBG3("Agent NOT found by name %s.", name);
 866         return NULL;
 867 }
 868
 869 /*
 870  * Find a agent event in the given agent using name and loglevel.
 871  *
 872  * RCU read side lock MUST be acquired.
 873  *
 874  * Return object if found else NULL.
 875  */
 876 struct agent_event *agent_find_event(const char *name, int loglevel,
 877                 struct agent *agt)
 878 {
 879         struct lttng_ht_node_str *node;
 880         struct lttng_ht_iter iter;
 881         struct lttng_ht *ht;
 882         struct agent_ht_key key;
 883
 884         assert(name);
 885         assert(agt);
 886         assert(agt->events);
 887
 888         ht = agt->events;
 889         key.name = name;
 890         key.loglevel = loglevel;
 891
 892         cds_lfht_lookup(ht->ht, ht->hash_fct((void *) name, lttng_ht_seed),
 893                         ht_match_event, &key, &iter.iter);
 894         node = lttng_ht_iter_get_node_str(&iter);
 895         if (node == NULL) {
 896                 goto error;
 897         }
 898
 899         DBG3("Agent event found %s.", name);
 900         return caa_container_of(node, struct agent_event, node);
 901
 902 error:
 903         DBG3("Agent event NOT found %s.", name);
 904         return NULL;
 905 }
 906
 907 /*
 908  * Free given agent event. This event must not be globally visible at this
 909  * point (only expected to be used on failure just after event creation). After
 910  * this call, the pointer is not usable anymore.
 911  */
 912 void agent_destroy_event(struct agent_event *event)
 913 {
 914         assert(event);
 915
 916         free(event->filter);
 917         free(event->filter_expression);
 918         free(event);
 919 }
 920
 921 /*
 922  * Destroy an agent completely.
 923  */
 924 void agent_destroy(struct agent *agt)
 925 {
 926         struct lttng_ht_node_str *node;
 927         struct lttng_ht_iter iter;
 928
 929         assert(agt);
 930
 931         DBG3("Agent destroy");
 932
 933         /*
 934          * Just ignore if no events hash table exists. This is possible if for
 935          * instance an agent object was allocated but not initialized.
 936          */
 937         if (!agt->events) {
 938                 return;
 939         }
 940
 941         rcu_read_lock();
 942         cds_lfht_for_each_entry(agt->events->ht, &iter.iter, node, node) {
 943                 int ret;
 944                 struct agent_event *event;
 945
 946                 /*
 947                  * When destroying an event, we have to try to disable it on the agent
 948                  * side so the event stops generating data. The return value is not
 949                  * important since we have to continue anyway destroying the object.
 950                  */
 951                 event = caa_container_of(node, struct agent_event, node);
 952                 (void) agent_disable_event(event, agt->domain);
 953
 954                 ret = lttng_ht_del(agt->events, &iter);
 955                 assert(!ret);
 956                 call_rcu(&node->head, destroy_event_agent_rcu);
 957         }
 958         rcu_read_unlock();
 959
 960         ht_cleanup_push(agt->events);
 961         free(agt);
 962 }
 963
 964 /*
 965  * Allocate agent_apps_ht_by_sock.
 966  */
 967 int agent_app_ht_alloc(void)
 968 {
 969         int ret = 0;
 970
 971         agent_apps_ht_by_sock = lttng_ht_new(0, LTTNG_HT_TYPE_ULONG);
 972         if (!agent_apps_ht_by_sock) {
 973                 ret = -1;
 974         }
 975
 976         return ret;
 977 }
 978
 979 /*
 980  * Destroy a agent application by socket.
 981  */
 982 void agent_destroy_app_by_sock(int sock)
 983 {
 984         struct agent_app *app;
 985
 986         assert(sock >= 0);
 987
 988         /*
 989          * Not finding an application is a very important error that should NEVER
 990          * happen. The hash table deletion is ONLY done through this call when the
 991          * main sessiond thread is torn down.
 992          */
 993         rcu_read_lock();
 994         app = agent_find_app_by_sock(sock);
 995         assert(app);
 996
 997         /* RCU read side lock is assumed to be held by this function. */
 998         agent_delete_app(app);
 999
1000         /* The application is freed in a RCU call but the socket is closed here. */
1001         agent_destroy_app(app);
1002         rcu_read_unlock();
1003 }
1004
1005 /*
1006  * Clean-up the agent app hash table and destroy it.
1007  */
1008 void agent_app_ht_clean(void)
1009 {
1010         struct lttng_ht_node_ulong *node;
1011         struct lttng_ht_iter iter;
1012
1013         if (!agent_apps_ht_by_sock) {
1014                 return;
1015         }
1016         rcu_read_lock();
1017         cds_lfht_for_each_entry(agent_apps_ht_by_sock->ht, &iter.iter, node, node) {
1018                 struct agent_app *app;
1019
1020                 app = caa_container_of(node, struct agent_app, node);
1021                 agent_destroy_app_by_sock(app->sock->fd);
1022         }
1023         rcu_read_unlock();
1024
1025         lttng_ht_destroy(agent_apps_ht_by_sock);
1026 }
1027
1028 /*
1029  * Update a agent application (given socket) using the given agent.
1030  *
1031  * Note that this function is most likely to be used with a tracing session
1032  * thus the caller should make sure to hold the appropriate lock(s).
1033  */
1034 void agent_update(struct agent *agt, int sock)
1035 {
1036         int ret;
1037         struct agent_app *app;
1038         struct agent_event *event;
1039         struct lttng_ht_iter iter;
1040
1041         assert(agt);
1042         assert(sock >= 0);
1043
1044         DBG("Agent updating app socket %d", sock);
1045
1046         rcu_read_lock();
1047         cds_lfht_for_each_entry(agt->events->ht, &iter.iter, event, node.node) {
1048                 /* Skip event if disabled. */
1049                 if (!event->enabled) {
1050                         continue;
1051                 }
1052
1053                 app = agent_find_app_by_sock(sock);
1054                 /*
1055                  * We are in the registration path thus if the application is gone,
1056                  * there is a serious code flow error.
1057                  */
1058                 assert(app);
1059
1060                 ret = enable_event(app, event);
1061                 if (ret != LTTNG_OK) {
1062                         DBG2("Agent update unable to enable event %s on app pid: %d sock %d",
1063                                         event->name, app->pid, app->sock->fd);
1064                         /* Let's try the others here and don't assume the app is dead. */
1065                         continue;
1066                 }
1067         }
1068         rcu_read_unlock();
1069 }