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         free(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, 0);
 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;
 497         struct agent_app *app;
 498         struct lttng_ht_iter iter;
 499
 500         assert(event);
 501
 502         rcu_read_lock();
 503
 504         cds_lfht_for_each_entry(agent_apps_ht_by_sock->ht, &iter.iter, app,
 505                         node.node) {
 506                 if (app->domain != domain) {
 507                         continue;
 508                 }
 509
 510                 /* Enable event on agent application through TCP socket. */
 511                 ret = disable_event(app, event);
 512                 if (ret != LTTNG_OK) {
 513                         goto error;
 514                 }
 515         }
 516
 517         event->enabled = 0;
 518         ret = LTTNG_OK;
 519
 520 error:
 521         rcu_read_unlock();
 522         return ret;
 523 }
 524
 525 /*
 526  * Ask every agent for the list of possible event. Events is allocated with the
 527  * events of every agent application.
 528  *
 529  * Return the number of events or else a negative value.
 530  */
 531 int agent_list_events(struct lttng_event **events,
 532                 enum lttng_domain_type domain)
 533 {
 534         int ret;
 535         size_t nbmem, count = 0;
 536         struct agent_app *app;
 537         struct lttng_event *tmp_events = NULL;
 538         struct lttng_ht_iter iter;
 539
 540         assert(events);
 541
 542         nbmem = UST_APP_EVENT_LIST_SIZE;
 543         tmp_events = zmalloc(nbmem * sizeof(*tmp_events));
 544         if (!tmp_events) {
 545                 PERROR("zmalloc agent list events");
 546                 ret = -ENOMEM;
 547                 goto error;
 548         }
 549
 550         rcu_read_lock();
 551         cds_lfht_for_each_entry(agent_apps_ht_by_sock->ht, &iter.iter, app,
 552                         node.node) {
 553                 ssize_t nb_ev;
 554                 struct lttng_event *agent_events;
 555
 556                 /* Skip domain not asked by the list. */
 557                 if (app->domain != domain) {
 558                         continue;
 559                 }
 560
 561                 nb_ev = list_events(app, &agent_events);
 562                 if (nb_ev < 0) {
 563                         ret = nb_ev;
 564                         goto error_unlock;
 565                 }
 566
 567                 if (count + nb_ev > nbmem) {
 568                         /* In case the realloc fails, we free the memory */
 569                         struct lttng_event *new_tmp_events;
 570                         size_t new_nbmem;
 571
 572                         new_nbmem = max_t(size_t, count + nb_ev, nbmem << 1);
 573                         DBG2("Reallocating agent event list from %zu to %zu entries",
 574                                         nbmem, new_nbmem);
 575                         new_tmp_events = realloc(tmp_events,
 576                                 new_nbmem * sizeof(*new_tmp_events));
 577                         if (!new_tmp_events) {
 578                                 PERROR("realloc agent events");
 579                                 ret = -ENOMEM;
 580                                 free(agent_events);
 581                                 goto error_unlock;
 582                         }
 583                         /* Zero the new memory */
 584                         memset(new_tmp_events + nbmem, 0,
 585                                 (new_nbmem - nbmem) * sizeof(*new_tmp_events));
 586                         nbmem = new_nbmem;
 587                         tmp_events = new_tmp_events;
 588                 }
 589                 memcpy(tmp_events + count, agent_events,
 590                         nb_ev * sizeof(*tmp_events));
 591                 free(agent_events);
 592                 count += nb_ev;
 593         }
 594         rcu_read_unlock();
 595
 596         ret = count;
 597         *events = tmp_events;
 598         return ret;
 599
 600 error_unlock:
 601         rcu_read_unlock();
 602 error:
 603         free(tmp_events);
 604         return ret;
 605 }
 606
 607 /*
 608  * Create a agent app object using the given PID.
 609  *
 610  * Return newly allocated object or else NULL on error.
 611  */
 612 struct agent_app *agent_create_app(pid_t pid, enum lttng_domain_type domain,
 613                 struct lttcomm_sock *sock)
 614 {
 615         struct agent_app *app;
 616
 617         assert(sock);
 618
 619         app = zmalloc(sizeof(*app));
 620         if (!app) {
 621                 PERROR("zmalloc agent create");
 622                 goto error;
 623         }
 624
 625         app->pid = pid;
 626         app->domain = domain;
 627         app->sock = sock;
 628         lttng_ht_node_init_ulong(&app->node, (unsigned long) app->sock->fd);
 629
 630 error:
 631         return app;
 632 }
 633
 634 /*
 635  * Lookup agent app by socket in the global hash table.
 636  *
 637  * RCU read side lock MUST be acquired.
 638  *
 639  * Return object if found else NULL.
 640  */
 641 struct agent_app *agent_find_app_by_sock(int sock)
 642 {
 643         struct lttng_ht_node_ulong *node;
 644         struct lttng_ht_iter iter;
 645         struct agent_app *app;
 646
 647         assert(sock >= 0);
 648
 649         lttng_ht_lookup(agent_apps_ht_by_sock, (void *)((unsigned long) sock), &iter);
 650         node = lttng_ht_iter_get_node_ulong(&iter);
 651         if (node == NULL) {
 652                 goto error;
 653         }
 654         app = caa_container_of(node, struct agent_app, node);
 655
 656         DBG3("Agent app pid %d found by sock %d.", app->pid, sock);
 657         return app;
 658
 659 error:
 660         DBG3("Agent app NOT found by sock %d.", sock);
 661         return NULL;
 662 }
 663
 664 /*
 665  * Add agent application object to the global hash table.
 666  */
 667 void agent_add_app(struct agent_app *app)
 668 {
 669         assert(app);
 670
 671         DBG3("Agent adding app sock: %d and pid: %d to ht", app->sock->fd, app->pid);
 672
 673         rcu_read_lock();
 674         lttng_ht_add_unique_ulong(agent_apps_ht_by_sock, &app->node);
 675         rcu_read_unlock();
 676 }
 677
 678 /*
 679  * Delete agent application from the global hash table.
 680  */
 681 void agent_delete_app(struct agent_app *app)
 682 {
 683         int ret;
 684         struct lttng_ht_iter iter;
 685
 686         assert(app);
 687
 688         DBG3("Agent deleting app pid: %d and sock: %d", app->pid, app->sock->fd);
 689
 690         iter.iter.node = &app->node.node;
 691         rcu_read_lock();
 692         ret = lttng_ht_del(agent_apps_ht_by_sock, &iter);
 693         rcu_read_unlock();
 694         assert(!ret);
 695 }
 696
 697 /*
 698  * Destroy a agent application object by detaching it from its corresponding
 699  * UST app if one is connected by closing the socket. Finally, perform a
 700  * delayed memory reclaim.
 701  */
 702 void agent_destroy_app(struct agent_app *app)
 703 {
 704         assert(app);
 705
 706         if (app->sock) {
 707                 app->sock->ops->close(app->sock);
 708                 lttcomm_destroy_sock(app->sock);
 709         }
 710
 711         call_rcu(&app->node.head, destroy_app_agent_rcu);
 712 }
 713
 714 /*
 715  * Initialize an already allocated agent object.
 716  *
 717  * Return 0 on success or else a negative errno value.
 718  */
 719 int agent_init(struct agent *agt)
 720 {
 721         int ret;
 722
 723         assert(agt);
 724
 725         agt->events = lttng_ht_new(0, LTTNG_HT_TYPE_STRING);
 726         if (!agt->events) {
 727                 ret = -ENOMEM;
 728                 goto error;
 729         }
 730         lttng_ht_node_init_u64(&agt->node, agt->domain);
 731
 732         return 0;
 733
 734 error:
 735         return ret;
 736 }
 737
 738 /*
 739  * Add agent object to the given hash table.
 740  */
 741 void agent_add(struct agent *agt, struct lttng_ht *ht)
 742 {
 743         assert(agt);
 744         assert(ht);
 745
 746         DBG3("Agent adding from domain %d", agt->domain);
 747
 748         rcu_read_lock();
 749         lttng_ht_add_unique_u64(ht, &agt->node);
 750         rcu_read_unlock();
 751 }
 752
 753 /*
 754  * Create an agent object for the given domain.
 755  *
 756  * Return the allocated agent or NULL on error.
 757  */
 758 struct agent *agent_create(enum lttng_domain_type domain)
 759 {
 760         int ret;
 761         struct agent *agt;
 762
 763         agt = zmalloc(sizeof(*agt));
 764         if (!agt) {
 765                 goto error;
 766         }
 767         agt->domain = domain;
 768
 769         ret = agent_init(agt);
 770         if (ret < 0) {
 771                 free(agt);
 772                 goto error;
 773         }
 774
 775 error:
 776         return agt;
 777 }
 778
 779 /*
 780  * Create a newly allocated agent event data structure. If name is valid, it's
 781  * copied into the created event.
 782  *
 783  * Return a new object else NULL on error.
 784  */
 785 struct agent_event *agent_create_event(const char *name,
 786                 struct lttng_filter_bytecode *filter)
 787 {
 788         struct agent_event *event;
 789
 790         DBG3("Agent create new event with name %s", name);
 791
 792         event = zmalloc(sizeof(*event));
 793         if (!event) {
 794                 goto error;
 795         }
 796
 797         if (name) {
 798                 strncpy(event->name, name, sizeof(event->name));
 799                 event->name[sizeof(event->name) - 1] = '\0';
 800                 lttng_ht_node_init_str(&event->node, event->name);
 801         }
 802
 803         if (filter) {
 804                 event->filter = filter;
 805         }
 806
 807 error:
 808         return event;
 809 }
 810
 811 /*
 812  * Unique add of a agent event to an agent object.
 813  */
 814 void agent_add_event(struct agent_event *event, struct agent *agt)
 815 {
 816         assert(event);
 817         assert(agt);
 818         assert(agt->events);
 819
 820         DBG3("Agent adding event %s", event->name);
 821
 822         rcu_read_lock();
 823         add_unique_agent_event(agt->events, event);
 824         rcu_read_unlock();
 825         agt->being_used = 1;
 826 }
 827
 828 /*
 829  * Find a agent event in the given agent using name.
 830  *
 831  * RCU read side lock MUST be acquired.
 832  *
 833  * Return object if found else NULL.
 834  */
 835 struct agent_event *agent_find_event_by_name(const char *name,
 836                 struct agent *agt)
 837 {
 838         struct lttng_ht_node_str *node;
 839         struct lttng_ht_iter iter;
 840         struct lttng_ht *ht;
 841         struct agent_ht_key key;
 842
 843         assert(name);
 844         assert(agt);
 845         assert(agt->events);
 846
 847         ht = agt->events;
 848         key.name = name;
 849
 850         cds_lfht_lookup(ht->ht, ht->hash_fct((void *) name, lttng_ht_seed),
 851                         ht_match_event_by_name, &key, &iter.iter);
 852         node = lttng_ht_iter_get_node_str(&iter);
 853         if (node == NULL) {
 854                 goto error;
 855         }
 856
 857         DBG3("Agent event found %s by name.", name);
 858         return caa_container_of(node, struct agent_event, node);
 859
 860 error:
 861         DBG3("Agent NOT found by name %s.", name);
 862         return NULL;
 863 }
 864
 865 /*
 866  * Find a agent event in the given agent using name and loglevel.
 867  *
 868  * RCU read side lock MUST be acquired.
 869  *
 870  * Return object if found else NULL.
 871  */
 872 struct agent_event *agent_find_event(const char *name, int loglevel,
 873                 struct agent *agt)
 874 {
 875         struct lttng_ht_node_str *node;
 876         struct lttng_ht_iter iter;
 877         struct lttng_ht *ht;
 878         struct agent_ht_key key;
 879
 880         assert(name);
 881         assert(agt);
 882         assert(agt->events);
 883
 884         ht = agt->events;
 885         key.name = name;
 886         key.loglevel = loglevel;
 887
 888         cds_lfht_lookup(ht->ht, ht->hash_fct((void *) name, lttng_ht_seed),
 889                         ht_match_event, &key, &iter.iter);
 890         node = lttng_ht_iter_get_node_str(&iter);
 891         if (node == NULL) {
 892                 goto error;
 893         }
 894
 895         DBG3("Agent event found %s.", name);
 896         return caa_container_of(node, struct agent_event, node);
 897
 898 error:
 899         DBG3("Agent NOT found %s.", name);
 900         return NULL;
 901 }
 902
 903 /*
 904  * Free given agent event. This event must not be globally visible at this
 905  * point (only expected to be used on failure just after event creation). After
 906  * this call, the pointer is not usable anymore.
 907  */
 908 void agent_destroy_event(struct agent_event *event)
 909 {
 910         assert(event);
 911
 912         free(event);
 913 }
 914
 915 /*
 916  * Destroy an agent completely. Note that the given pointer is NOT freed
 917  * thus a reference to static or stack data can be passed to this function.
 918  */
 919 void agent_destroy(struct agent *agt)
 920 {
 921         struct lttng_ht_node_str *node;
 922         struct lttng_ht_iter iter;
 923
 924         assert(agt);
 925
 926         DBG3("Agent destroy");
 927
 928         /*
 929          * Just ignore if no events hash table exists. This is possible if for
 930          * instance an agent object was allocated but not initialized.
 931          */
 932         if (!agt->events) {
 933                 return;
 934         }
 935
 936         rcu_read_lock();
 937         cds_lfht_for_each_entry(agt->events->ht, &iter.iter, node, node) {
 938                 int ret;
 939                 struct agent_event *event;
 940
 941                 /*
 942                  * When destroying an event, we have to try to disable it on the agent
 943                  * side so the event stops generating data. The return value is not
 944                  * important since we have to continue anyway destroying the object.
 945                  */
 946                 event = caa_container_of(node, struct agent_event, node);
 947                 (void) agent_disable_event(event, agt->domain);
 948
 949                 ret = lttng_ht_del(agt->events, &iter);
 950                 assert(!ret);
 951                 call_rcu(&node->head, destroy_event_agent_rcu);
 952         }
 953         rcu_read_unlock();
 954
 955         lttng_ht_destroy(agt->events);
 956 }
 957
 958 /*
 959  * Initialize agent subsystem.
 960  */
 961 int agent_setup(void)
 962 {
 963         agent_apps_ht_by_sock = lttng_ht_new(0, LTTNG_HT_TYPE_ULONG);
 964         if (!agent_apps_ht_by_sock) {
 965                 return -1;
 966         }
 967
 968         return 0;
 969 }
 970
 971 /*
 972  * Update a agent application (given socket) using the given agent.
 973  *
 974  * Note that this function is most likely to be used with a tracing session
 975  * thus the caller should make sure to hold the appropriate lock(s).
 976  */
 977 void agent_update(struct agent *agt, int sock)
 978 {
 979         int ret;
 980         struct agent_app *app;
 981         struct agent_event *event;
 982         struct lttng_ht_iter iter;
 983
 984         assert(agt);
 985         assert(sock >= 0);
 986
 987         DBG("Agent updating app socket %d", sock);
 988
 989         rcu_read_lock();
 990         cds_lfht_for_each_entry(agt->events->ht, &iter.iter, event, node.node) {
 991                 /* Skip event if disabled. */
 992                 if (!event->enabled) {
 993                         continue;
 994                 }
 995
 996                 app = agent_find_app_by_sock(sock);
 997                 /*
 998                  * We are in the registration path thus if the application is gone,
 999                  * there is a serious code flow error.
1000                  */
1001                 assert(app);
1002
1003                 ret = enable_event(app, event);
1004                 if (ret != LTTNG_OK) {
1005                         DBG2("Agent update unable to enable event %s on app pid: %d sock %d",
1006                                         event->name, app->pid, app->sock->fd);
1007                         /* Let's try the others here and don't assume the app is dead. */
1008                         continue;
1009                 }
1010         }
1011         rcu_read_unlock();
1012 }