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 #define _LGPL_SOURCE
  20 #include <assert.h>
  21 #include <urcu/uatomic.h>
  22
  23 #include <common/common.h>
  24 #include <common/sessiond-comm/agent.h>
  25
  26 #include <common/compat/endian.h>
  27
  28 #include "agent.h"
  29 #include "ust-app.h"
  30 #include "utils.h"
  31
  32 /*
  33  * Match function for the events hash table lookup by name.
  34  */
  35 static int ht_match_event_by_name(struct cds_lfht_node *node,
  36                 const void *_key)
  37 {
  38         struct agent_event *event;
  39         const struct agent_ht_key *key;
  40
  41         assert(node);
  42         assert(_key);
  43
  44         event = caa_container_of(node, struct agent_event, node.node);
  45         key = _key;
  46
  47         /* Match 1 elements of the key: name. */
  48
  49         /* Event name */
  50         if (strncmp(event->name, key->name, sizeof(event->name)) != 0) {
  51                 goto no_match;
  52         }
  53         /* Match. */
  54         return 1;
  55
  56 no_match:
  57         return 0;
  58 }
  59
  60 /*
  61  * Match function for the events hash table lookup by name and loglevel.
  62  */
  63 static int ht_match_event(struct cds_lfht_node *node,
  64                 const void *_key)
  65 {
  66         struct agent_event *event;
  67         const struct agent_ht_key *key;
  68
  69         assert(node);
  70         assert(_key);
  71
  72         event = caa_container_of(node, struct agent_event, node.node);
  73         key = _key;
  74
  75         /* Match 2 elements of the key: name and loglevel. */
  76
  77         /* Event name */
  78         if (strncmp(event->name, key->name, sizeof(event->name)) != 0) {
  79                 goto no_match;
  80         }
  81
  82         if (event->loglevel != key->loglevel) {
  83                 if (event->loglevel_type == LTTNG_EVENT_LOGLEVEL_ALL &&
  84                                 key->loglevel == 0 && event->loglevel == -1) {
  85                         goto match;
  86                 }
  87                 goto no_match;
  88         }
  89 match:
  90         return 1;
  91
  92 no_match:
  93         return 0;
  94 }
  95
  96 /*
  97  * Add unique agent event based on the event name and loglevel.
  98  */
  99 static void add_unique_agent_event(struct lttng_ht *ht,
 100                 struct agent_event *event)
 101 {
 102         struct cds_lfht_node *node_ptr;
 103         struct agent_ht_key key;
 104
 105         assert(ht);
 106         assert(ht->ht);
 107         assert(event);
 108
 109         key.name = event->name;
 110         key.loglevel = event->loglevel;
 111
 112         node_ptr = cds_lfht_add_unique(ht->ht,
 113                         ht->hash_fct(event->node.key, lttng_ht_seed),
 114                         ht_match_event, &key, &event->node.node);
 115         assert(node_ptr == &event->node.node);
 116 }
 117
 118 /*
 119  * URCU delayed agent event reclaim.
 120  */
 121 static void destroy_event_agent_rcu(struct rcu_head *head)
 122 {
 123         struct lttng_ht_node_str *node =
 124                 caa_container_of(head, struct lttng_ht_node_str, head);
 125         struct agent_event *event =
 126                 caa_container_of(node, struct agent_event, node);
 127
 128         free(event);
 129 }
 130
 131 /*
 132  * URCU delayed agent app reclaim.
 133  */
 134 static void destroy_app_agent_rcu(struct rcu_head *head)
 135 {
 136         struct lttng_ht_node_ulong *node =
 137                 caa_container_of(head, struct lttng_ht_node_ulong, head);
 138         struct agent_app *app =
 139                 caa_container_of(node, struct agent_app, node);
 140
 141         free(app);
 142 }
 143
 144 /*
 145  * Communication with the agent. Send the message header to the given socket in
 146  * big endian.
 147  *
 148  * Return 0 on success or else a negative errno message of sendmsg() op.
 149  */
 150 static int send_header(struct lttcomm_sock *sock, uint64_t data_size,
 151                 uint32_t cmd, uint32_t cmd_version)
 152 {
 153         int ret;
 154         ssize_t size;
 155         struct lttcomm_agent_hdr msg;
 156
 157         assert(sock);
 158
 159         memset(&msg, 0, sizeof(msg));
 160         msg.data_size = htobe64(data_size);
 161         msg.cmd = htobe32(cmd);
 162         msg.cmd_version = htobe32(cmd_version);
 163
 164         size = sock->ops->sendmsg(sock, &msg, sizeof(msg), 0);
 165         if (size < sizeof(msg)) {
 166                 ret = -errno;
 167                 goto error;
 168         }
 169         ret = 0;
 170
 171 error:
 172         return ret;
 173 }
 174
 175 /*
 176  * Communication call with the agent. Send the payload to the given socket. The
 177  * header MUST be sent prior to this call.
 178  *
 179  * Return 0 on success or else a negative errno value of sendmsg() op.
 180  */
 181 static int send_payload(struct lttcomm_sock *sock, void *data,
 182                 size_t size)
 183 {
 184         int ret;
 185         ssize_t len;
 186
 187         assert(sock);
 188         assert(data);
 189
 190         len = sock->ops->sendmsg(sock, data, size, 0);
 191         if (len < size) {
 192                 ret = -errno;
 193                 goto error;
 194         }
 195         ret = 0;
 196
 197 error:
 198         return ret;
 199 }
 200
 201 /*
 202  * Communication call with the agent. Receive reply from the agent using the
 203  * given socket.
 204  *
 205  * Return 0 on success or else a negative errno value from recvmsg() op.
 206  */
 207 static int recv_reply(struct lttcomm_sock *sock, void *buf, size_t size)
 208 {
 209         int ret;
 210         ssize_t len;
 211
 212         assert(sock);
 213         assert(buf);
 214
 215         len = sock->ops->recvmsg(sock, buf, size, 0);
 216         if (len < size) {
 217                 ret = -errno;
 218                 goto error;
 219         }
 220         ret = 0;
 221
 222 error:
 223         return ret;
 224 }
 225
 226 /*
 227  * Internal event listing for a given app. Populate events.
 228  *
 229  * Return number of element in the list or else a negative LTTNG_ERR* code.
 230  * On success, the caller is responsible for freeing the memory
 231  * allocated for "events".
 232  */
 233 static ssize_t list_events(struct agent_app *app, struct lttng_event **events)
 234 {
 235         int ret, i, len = 0, offset = 0;
 236         uint32_t nb_event;
 237         size_t data_size;
 238         struct lttng_event *tmp_events = NULL;
 239         struct lttcomm_agent_list_reply *reply = NULL;
 240         struct lttcomm_agent_list_reply_hdr reply_hdr;
 241
 242         assert(app);
 243         assert(app->sock);
 244         assert(events);
 245
 246         DBG2("Agent listing events for app pid: %d and socket %d", app->pid,
 247                         app->sock->fd);
 248
 249         ret = send_header(app->sock, 0, AGENT_CMD_LIST, 0);
 250         if (ret < 0) {
 251                 goto error_io;
 252         }
 253
 254         /* Get list header so we know how much we'll receive. */
 255         ret = recv_reply(app->sock, &reply_hdr, sizeof(reply_hdr));
 256         if (ret < 0) {
 257                 goto error_io;
 258         }
 259
 260         switch (be32toh(reply_hdr.ret_code)) {
 261         case AGENT_RET_CODE_SUCCESS:
 262                 data_size = be32toh(reply_hdr.data_size) + sizeof(*reply);
 263                 break;
 264         default:
 265                 ERR("Agent returned an unknown code: %" PRIu32,
 266                                 be32toh(reply_hdr.ret_code));
 267                 ret = LTTNG_ERR_FATAL;
 268                 goto error;
 269         }
 270
 271         reply = zmalloc(data_size);
 272         if (!reply) {
 273                 ret = LTTNG_ERR_NOMEM;
 274                 goto error;
 275         }
 276
 277         /* Get the list with the appropriate data size. */
 278         ret = recv_reply(app->sock, reply, data_size);
 279         if (ret < 0) {
 280                 goto error_io;
 281         }
 282
 283         nb_event = be32toh(reply->nb_event);
 284         tmp_events = zmalloc(sizeof(*tmp_events) * nb_event);
 285         if (!tmp_events) {
 286                 ret = LTTNG_ERR_NOMEM;
 287                 goto error;
 288         }
 289
 290         for (i = 0; i < nb_event; i++) {
 291                 offset += len;
 292                 strncpy(tmp_events[i].name, reply->payload + offset,
 293                                 sizeof(tmp_events[i].name));
 294                 tmp_events[i].pid = app->pid;
 295                 tmp_events[i].enabled = -1;
 296                 len = strlen(reply->payload + offset) + 1;
 297         }
 298
 299         *events = tmp_events;
 300
 301         free(reply);
 302         return nb_event;
 303
 304 error_io:
 305         ret = LTTNG_ERR_UST_LIST_FAIL;
 306 error:
 307         free(reply);
 308         free(tmp_events);
 309         return -ret;
 310
 311 }
 312
 313 /*
 314  * Internal enable agent event on a agent application. This function
 315  * communicates with the agent to enable a given event.
 316  *
 317  * Return LTTNG_OK on success or else a LTTNG_ERR* code.
 318  */
 319 static int enable_event(struct agent_app *app, struct agent_event *event)
 320 {
 321         int ret;
 322         uint64_t data_size;
 323         struct lttcomm_agent_enable msg;
 324         struct lttcomm_agent_generic_reply reply;
 325
 326         assert(app);
 327         assert(app->sock);
 328         assert(event);
 329
 330         DBG2("Agent enabling event %s for app pid: %d and socket %d", event->name,
 331                         app->pid, app->sock->fd);
 332
 333         data_size = sizeof(msg);
 334
 335         ret = send_header(app->sock, data_size, AGENT_CMD_ENABLE, 0);
 336         if (ret < 0) {
 337                 goto error_io;
 338         }
 339
 340         memset(&msg, 0, sizeof(msg));
 341         msg.loglevel = event->loglevel;
 342         msg.loglevel_type = event->loglevel_type;
 343         strncpy(msg.name, event->name, sizeof(msg.name));
 344         ret = send_payload(app->sock, &msg, sizeof(msg));
 345         if (ret < 0) {
 346                 goto error_io;
 347         }
 348
 349         ret = recv_reply(app->sock, &reply, sizeof(reply));
 350         if (ret < 0) {
 351                 goto error_io;
 352         }
 353
 354         switch (be32toh(reply.ret_code)) {
 355         case AGENT_RET_CODE_SUCCESS:
 356                 break;
 357         case AGENT_RET_CODE_UNKNOWN_NAME:
 358                 ret = LTTNG_ERR_UST_EVENT_NOT_FOUND;
 359                 goto error;
 360         default:
 361                 ERR("Agent returned an unknown code: %" PRIu32,
 362                                 be32toh(reply.ret_code));
 363                 ret = LTTNG_ERR_FATAL;
 364                 goto error;
 365         }
 366
 367         return LTTNG_OK;
 368
 369 error_io:
 370         ret = LTTNG_ERR_UST_ENABLE_FAIL;
 371 error:
 372         return ret;
 373 }
 374
 375 /*
 376  * Internal disable agent event call on a agent application. This function
 377  * communicates with the agent to disable a given event.
 378  *
 379  * Return LTTNG_OK on success or else a LTTNG_ERR* code.
 380  */
 381 static int disable_event(struct agent_app *app, struct agent_event *event)
 382 {
 383         int ret;
 384         uint64_t data_size;
 385         struct lttcomm_agent_disable msg;
 386         struct lttcomm_agent_generic_reply reply;
 387
 388         assert(app);
 389         assert(app->sock);
 390         assert(event);
 391
 392         DBG2("Agent disabling event %s for app pid: %d and socket %d", event->name,
 393                         app->pid, app->sock->fd);
 394
 395         data_size = sizeof(msg);
 396
 397         ret = send_header(app->sock, data_size, AGENT_CMD_DISABLE, 0);
 398         if (ret < 0) {
 399                 goto error_io;
 400         }
 401
 402         memset(&msg, 0, sizeof(msg));
 403         strncpy(msg.name, event->name, sizeof(msg.name));
 404         ret = send_payload(app->sock, &msg, sizeof(msg));
 405         if (ret < 0) {
 406                 goto error_io;
 407         }
 408
 409         ret = recv_reply(app->sock, &reply, sizeof(reply));
 410         if (ret < 0) {
 411                 goto error_io;
 412         }
 413
 414         switch (be32toh(reply.ret_code)) {
 415         case AGENT_RET_CODE_SUCCESS:
 416                 break;
 417         case AGENT_RET_CODE_UNKNOWN_NAME:
 418                 ret = LTTNG_ERR_UST_EVENT_NOT_FOUND;
 419                 goto error;
 420         default:
 421                 ERR("Agent returned an unknown code: %" PRIu32,
 422                                 be32toh(reply.ret_code));
 423                 ret = LTTNG_ERR_FATAL;
 424                 goto error;
 425         }
 426
 427         return LTTNG_OK;
 428
 429 error_io:
 430         ret = LTTNG_ERR_UST_DISABLE_FAIL;
 431 error:
 432         return ret;
 433 }
 434
 435 /*
 436  * Send back the registration DONE command to a given agent application.
 437  *
 438  * Return 0 on success or else a negative value.
 439  */
 440 int agent_send_registration_done(struct agent_app *app)
 441 {
 442         assert(app);
 443         assert(app->sock);
 444
 445         DBG("Agent sending registration done to app socket %d", app->sock->fd);
 446
 447         return send_header(app->sock, 0, AGENT_CMD_REG_DONE, 0);
 448 }
 449
 450 /*
 451  * Enable agent event on every agent applications registered with the session
 452  * daemon.
 453  *
 454  * Return LTTNG_OK on success or else a LTTNG_ERR* code.
 455  */
 456 int agent_enable_event(struct agent_event *event,
 457                 enum lttng_domain_type domain)
 458 {
 459         int ret;
 460         struct agent_app *app;
 461         struct lttng_ht_iter iter;
 462
 463         assert(event);
 464
 465         rcu_read_lock();
 466
 467         cds_lfht_for_each_entry(agent_apps_ht_by_sock->ht, &iter.iter, app,
 468                         node.node) {
 469                 if (app->domain != domain) {
 470                         continue;
 471                 }
 472
 473                 /* Enable event on agent application through TCP socket. */
 474                 ret = enable_event(app, event);
 475                 if (ret != LTTNG_OK) {
 476                         goto error;
 477                 }
 478         }
 479
 480         event->enabled = 1;
 481         ret = LTTNG_OK;
 482
 483 error:
 484         rcu_read_unlock();
 485         return ret;
 486 }
 487
 488 /*
 489  * Disable agent event on every agent applications registered with the session
 490  * daemon.
 491  *
 492  * Return LTTNG_OK on success or else a LTTNG_ERR* code.
 493  */
 494 int agent_disable_event(struct agent_event *event,
 495                 enum lttng_domain_type domain)
 496 {
 497         int ret;
 498         struct agent_app *app;
 499         struct lttng_ht_iter iter;
 500
 501         assert(event);
 502
 503         rcu_read_lock();
 504
 505         cds_lfht_for_each_entry(agent_apps_ht_by_sock->ht, &iter.iter, app,
 506                         node.node) {
 507                 if (app->domain != domain) {
 508                         continue;
 509                 }
 510
 511                 /* Enable event on agent application through TCP socket. */
 512                 ret = disable_event(app, event);
 513                 if (ret != LTTNG_OK) {
 514                         goto error;
 515                 }
 516         }
 517
 518         event->enabled = 0;
 519         ret = LTTNG_OK;
 520
 521 error:
 522         rcu_read_unlock();
 523         return ret;
 524 }
 525
 526 /*
 527  * Ask every agent for the list of possible event. Events is allocated with the
 528  * events of every agent application.
 529  *
 530  * Return the number of events or else a negative value.
 531  */
 532 int agent_list_events(struct lttng_event **events,
 533                 enum lttng_domain_type domain)
 534 {
 535         int ret;
 536         size_t nbmem, count = 0;
 537         struct agent_app *app;
 538         struct lttng_event *tmp_events = NULL;
 539         struct lttng_ht_iter iter;
 540
 541         assert(events);
 542
 543         DBG2("Agent listing events for domain %d", domain);
 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 void agent_delete_app(struct agent_app *app)
 685 {
 686         int ret;
 687         struct lttng_ht_iter iter;
 688
 689         assert(app);
 690
 691         DBG3("Agent deleting app pid: %d and sock: %d", app->pid, app->sock->fd);
 692
 693         iter.iter.node = &app->node.node;
 694         rcu_read_lock();
 695         ret = lttng_ht_del(agent_apps_ht_by_sock, &iter);
 696         rcu_read_unlock();
 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 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);
 918 }
 919
 920 /*
 921  * Destroy an agent completely. Note that the given pointer is NOT freed
 922  * thus a reference to static or stack data can be passed to this function.
 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 }
 962
 963 /*
 964  * Initialize agent subsystem.
 965  */
 966 int agent_setup(void)
 967 {
 968         agent_apps_ht_by_sock = lttng_ht_new(0, LTTNG_HT_TYPE_ULONG);
 969         if (!agent_apps_ht_by_sock) {
 970                 return -1;
 971         }
 972
 973         return 0;
 974 }
 975
 976 /*
 977  * Update a agent application (given socket) using the given agent.
 978  *
 979  * Note that this function is most likely to be used with a tracing session
 980  * thus the caller should make sure to hold the appropriate lock(s).
 981  */
 982 void agent_update(struct agent *agt, int sock)
 983 {
 984         int ret;
 985         struct agent_app *app;
 986         struct agent_event *event;
 987         struct lttng_ht_iter iter;
 988
 989         assert(agt);
 990         assert(sock >= 0);
 991
 992         DBG("Agent updating app socket %d", sock);
 993
 994         rcu_read_lock();
 995         cds_lfht_for_each_entry(agt->events->ht, &iter.iter, event, node.node) {
 996                 /* Skip event if disabled. */
 997                 if (!event->enabled) {
 998                         continue;
 999                 }
1000
1001                 app = agent_find_app_by_sock(sock);
1002                 /*
1003                  * We are in the registration path thus if the application is gone,
1004                  * there is a serious code flow error.
1005                  */
1006                 assert(app);
1007
1008                 ret = enable_event(app, event);
1009                 if (ret != LTTNG_OK) {
1010                         DBG2("Agent update unable to enable event %s on app pid: %d sock %d",
1011                                         event->name, app->pid, app->sock->fd);
1012                         /* Let's try the others here and don't assume the app is dead. */
1013                         continue;
1014                 }
1015         }
1016         rcu_read_unlock();
1017 }