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 #include "error.h"
  32
  33 #define AGENT_RET_CODE_INDEX(code) (code - AGENT_RET_CODE_SUCCESS)
  34
  35 /*
  36  * Human readable agent return code.
  37  */
  38 static const char *error_string_array[] = {
  39         [ AGENT_RET_CODE_INDEX(AGENT_RET_CODE_SUCCESS) ] = "Success",
  40         [ AGENT_RET_CODE_INDEX(AGENT_RET_CODE_INVALID) ] = "Invalid command",
  41         [ AGENT_RET_CODE_INDEX(AGENT_RET_CODE_UNKNOWN_NAME) ] = "Unknown logger name",
  42
  43         /* Last element */
  44         [ AGENT_RET_CODE_INDEX(AGENT_RET_CODE_NR) ] = "Unknown code",
  45 };
  46
  47 static
  48 void log_reply_code(uint32_t in_reply_ret_code)
  49 {
  50         int level = PRINT_DBG3;
  51         /*
  52          * reply_ret_code and in_reply_ret_code are kept separate to have a
  53          * sanitized value (used to retrieve the human readable string) and the
  54          * original value which is logged as-is.
  55          */
  56         uint32_t reply_ret_code = in_reply_ret_code;
  57
  58         if (reply_ret_code < AGENT_RET_CODE_SUCCESS ||
  59                         reply_ret_code >= AGENT_RET_CODE_NR) {
  60                 reply_ret_code = AGENT_RET_CODE_NR;
  61                 level = PRINT_ERR;
  62         }
  63
  64         LOG(level, "Agent replied with retcode: %s (%"PRIu32")",
  65                         error_string_array[AGENT_RET_CODE_INDEX(
  66                         reply_ret_code)],
  67                         in_reply_ret_code);
  68 }
  69
  70 /*
  71  * Match function for the events hash table lookup by name.
  72  */
  73 static int ht_match_event_by_name(struct cds_lfht_node *node,
  74                 const void *_key)
  75 {
  76         struct agent_event *event;
  77         const struct agent_ht_key *key;
  78
  79         assert(node);
  80         assert(_key);
  81
  82         event = caa_container_of(node, struct agent_event, node.node);
  83         key = _key;
  84
  85         /* Match 1 elements of the key: name. */
  86
  87         /* Event name */
  88         if (strncmp(event->name, key->name, sizeof(event->name)) != 0) {
  89                 goto no_match;
  90         }
  91         /* Match. */
  92         return 1;
  93
  94 no_match:
  95         return 0;
  96 }
  97
  98 /*
  99  * Match function for the events hash table lookup by name and loglevel.
 100  */
 101 static int ht_match_event(struct cds_lfht_node *node,
 102                 const void *_key)
 103 {
 104         struct agent_event *event;
 105         const struct agent_ht_key *key;
 106
 107         assert(node);
 108         assert(_key);
 109
 110         event = caa_container_of(node, struct agent_event, node.node);
 111         key = _key;
 112
 113         /* Match 2 elements of the key: name and loglevel. */
 114
 115         /* Event name */
 116         if (strncmp(event->name, key->name, sizeof(event->name)) != 0) {
 117                 goto no_match;
 118         }
 119
 120         if (event->loglevel != key->loglevel) {
 121                 if (event->loglevel_type == LTTNG_EVENT_LOGLEVEL_ALL &&
 122                                 key->loglevel == 0 && event->loglevel == -1) {
 123                         goto match;
 124                 }
 125                 goto no_match;
 126         }
 127 match:
 128         return 1;
 129
 130 no_match:
 131         return 0;
 132 }
 133
 134 /*
 135  * Add unique agent event based on the event name and loglevel.
 136  */
 137 static void add_unique_agent_event(struct lttng_ht *ht,
 138                 struct agent_event *event)
 139 {
 140         struct cds_lfht_node *node_ptr;
 141         struct agent_ht_key key;
 142
 143         assert(ht);
 144         assert(ht->ht);
 145         assert(event);
 146
 147         key.name = event->name;
 148         key.loglevel = event->loglevel;
 149
 150         node_ptr = cds_lfht_add_unique(ht->ht,
 151                         ht->hash_fct(event->node.key, lttng_ht_seed),
 152                         ht_match_event, &key, &event->node.node);
 153         assert(node_ptr == &event->node.node);
 154 }
 155
 156 /*
 157  * URCU delayed agent event reclaim.
 158  */
 159 static void destroy_event_agent_rcu(struct rcu_head *head)
 160 {
 161         struct lttng_ht_node_str *node =
 162                 caa_container_of(head, struct lttng_ht_node_str, head);
 163         struct agent_event *event =
 164                 caa_container_of(node, struct agent_event, node);
 165
 166         free(event);
 167 }
 168
 169 /*
 170  * URCU delayed agent app reclaim.
 171  */
 172 static void destroy_app_agent_rcu(struct rcu_head *head)
 173 {
 174         struct lttng_ht_node_ulong *node =
 175                 caa_container_of(head, struct lttng_ht_node_ulong, head);
 176         struct agent_app *app =
 177                 caa_container_of(node, struct agent_app, node);
 178
 179         free(app);
 180 }
 181
 182 /*
 183  * Communication with the agent. Send the message header to the given socket in
 184  * big endian.
 185  *
 186  * Return 0 on success or else a negative errno message of sendmsg() op.
 187  */
 188 static int send_header(struct lttcomm_sock *sock, uint64_t data_size,
 189                 uint32_t cmd, uint32_t cmd_version)
 190 {
 191         int ret;
 192         ssize_t size;
 193         struct lttcomm_agent_hdr msg;
 194
 195         assert(sock);
 196
 197         memset(&msg, 0, sizeof(msg));
 198         msg.data_size = htobe64(data_size);
 199         msg.cmd = htobe32(cmd);
 200         msg.cmd_version = htobe32(cmd_version);
 201
 202         size = sock->ops->sendmsg(sock, &msg, sizeof(msg), 0);
 203         if (size < sizeof(msg)) {
 204                 ret = -errno;
 205                 goto error;
 206         }
 207         ret = 0;
 208
 209 error:
 210         return ret;
 211 }
 212
 213 /*
 214  * Communication call with the agent. Send the payload to the given socket. The
 215  * header MUST be sent prior to this call.
 216  *
 217  * Return 0 on success or else a negative errno value of sendmsg() op.
 218  */
 219 static int send_payload(struct lttcomm_sock *sock, void *data,
 220                 size_t size)
 221 {
 222         int ret;
 223         ssize_t len;
 224
 225         assert(sock);
 226         assert(data);
 227
 228         len = sock->ops->sendmsg(sock, data, size, 0);
 229         if (len < size) {
 230                 ret = -errno;
 231                 goto error;
 232         }
 233         ret = 0;
 234
 235 error:
 236         return ret;
 237 }
 238
 239 /*
 240  * Communication call with the agent. Receive reply from the agent using the
 241  * given socket.
 242  *
 243  * Return 0 on success or else a negative errno value from recvmsg() op.
 244  */
 245 static int recv_reply(struct lttcomm_sock *sock, void *buf, size_t size)
 246 {
 247         int ret;
 248         ssize_t len;
 249
 250         assert(sock);
 251         assert(buf);
 252
 253         len = sock->ops->recvmsg(sock, buf, size, 0);
 254         if (len < size) {
 255                 ret = -errno;
 256                 goto error;
 257         }
 258         ret = 0;
 259
 260 error:
 261         return ret;
 262 }
 263
 264 /*
 265  * Internal event listing for a given app. Populate events.
 266  *
 267  * Return number of element in the list or else a negative LTTNG_ERR* code.
 268  * On success, the caller is responsible for freeing the memory
 269  * allocated for "events".
 270  */
 271 static ssize_t list_events(struct agent_app *app, struct lttng_event **events)
 272 {
 273         int ret, i, len = 0, offset = 0;
 274         uint32_t nb_event;
 275         size_t data_size;
 276         uint32_t reply_ret_code;
 277         struct lttng_event *tmp_events = NULL;
 278         struct lttcomm_agent_list_reply *reply = NULL;
 279         struct lttcomm_agent_list_reply_hdr reply_hdr;
 280
 281         assert(app);
 282         assert(app->sock);
 283         assert(events);
 284
 285         DBG2("Agent listing events for app pid: %d and socket %d", app->pid,
 286                         app->sock->fd);
 287
 288         ret = send_header(app->sock, 0, AGENT_CMD_LIST, 0);
 289         if (ret < 0) {
 290                 goto error_io;
 291         }
 292
 293         /* Get list header so we know how much we'll receive. */
 294         ret = recv_reply(app->sock, &reply_hdr, sizeof(reply_hdr));
 295         if (ret < 0) {
 296                 goto error_io;
 297         }
 298
 299         reply_ret_code = be32toh(reply_hdr.ret_code);
 300         log_reply_code(reply_ret_code);
 301         switch (reply_ret_code) {
 302         case AGENT_RET_CODE_SUCCESS:
 303                 data_size = be32toh(reply_hdr.data_size) + sizeof(*reply);
 304                 break;
 305         default:
 306                 ret = LTTNG_ERR_UNK;
 307                 goto error;
 308         }
 309
 310         reply = zmalloc(data_size);
 311         if (!reply) {
 312                 ret = LTTNG_ERR_NOMEM;
 313                 goto error;
 314         }
 315
 316         /* Get the list with the appropriate data size. */
 317         ret = recv_reply(app->sock, reply, data_size);
 318         if (ret < 0) {
 319                 goto error_io;
 320         }
 321
 322         nb_event = be32toh(reply->nb_event);
 323         tmp_events = zmalloc(sizeof(*tmp_events) * nb_event);
 324         if (!tmp_events) {
 325                 ret = LTTNG_ERR_NOMEM;
 326                 goto error;
 327         }
 328
 329         for (i = 0; i < nb_event; i++) {
 330                 offset += len;
 331                 strncpy(tmp_events[i].name, reply->payload + offset,
 332                                 sizeof(tmp_events[i].name));
 333                 tmp_events[i].pid = app->pid;
 334                 tmp_events[i].enabled = -1;
 335                 len = strlen(reply->payload + offset) + 1;
 336         }
 337
 338         *events = tmp_events;
 339
 340         free(reply);
 341         return nb_event;
 342
 343 error_io:
 344         ret = LTTNG_ERR_UST_LIST_FAIL;
 345 error:
 346         free(reply);
 347         free(tmp_events);
 348         return -ret;
 349
 350 }
 351
 352 /*
 353  * Internal enable agent event on a agent application. This function
 354  * communicates with the agent to enable a given event.
 355  *
 356  * Return LTTNG_OK on success or else a LTTNG_ERR* code.
 357  */
 358 static int enable_event(struct agent_app *app, struct agent_event *event)
 359 {
 360         int ret;
 361         uint64_t data_size;
 362         uint32_t reply_ret_code;
 363         struct lttcomm_agent_enable msg;
 364         struct lttcomm_agent_generic_reply reply;
 365
 366         assert(app);
 367         assert(app->sock);
 368         assert(event);
 369
 370         DBG2("Agent enabling event %s for app pid: %d and socket %d", event->name,
 371                         app->pid, app->sock->fd);
 372
 373         data_size = sizeof(msg);
 374
 375         ret = send_header(app->sock, data_size, AGENT_CMD_ENABLE, 0);
 376         if (ret < 0) {
 377                 goto error_io;
 378         }
 379
 380         memset(&msg, 0, sizeof(msg));
 381         msg.loglevel = event->loglevel;
 382         msg.loglevel_type = event->loglevel_type;
 383         strncpy(msg.name, event->name, sizeof(msg.name));
 384         ret = send_payload(app->sock, &msg, sizeof(msg));
 385         if (ret < 0) {
 386                 goto error_io;
 387         }
 388
 389         ret = recv_reply(app->sock, &reply, sizeof(reply));
 390         if (ret < 0) {
 391                 goto error_io;
 392         }
 393
 394         reply_ret_code = be32toh(reply.ret_code);
 395         log_reply_code(reply_ret_code);
 396         switch (reply_ret_code) {
 397         case AGENT_RET_CODE_SUCCESS:
 398                 break;
 399         case AGENT_RET_CODE_UNKNOWN_NAME:
 400                 ret = LTTNG_ERR_UST_EVENT_NOT_FOUND;
 401                 goto error;
 402         default:
 403                 ret = LTTNG_ERR_UNK;
 404                 goto error;
 405         }
 406
 407         return LTTNG_OK;
 408
 409 error_io:
 410         ret = LTTNG_ERR_UST_ENABLE_FAIL;
 411 error:
 412         return ret;
 413 }
 414
 415 /*
 416  * Internal disable agent event call on a agent application. This function
 417  * communicates with the agent to disable a given event.
 418  *
 419  * Return LTTNG_OK on success or else a LTTNG_ERR* code.
 420  */
 421 static int disable_event(struct agent_app *app, struct agent_event *event)
 422 {
 423         int ret;
 424         uint64_t data_size;
 425         uint32_t reply_ret_code;
 426         struct lttcomm_agent_disable msg;
 427         struct lttcomm_agent_generic_reply reply;
 428
 429         assert(app);
 430         assert(app->sock);
 431         assert(event);
 432
 433         DBG2("Agent disabling event %s for app pid: %d and socket %d", event->name,
 434                         app->pid, app->sock->fd);
 435
 436         data_size = sizeof(msg);
 437
 438         ret = send_header(app->sock, data_size, AGENT_CMD_DISABLE, 0);
 439         if (ret < 0) {
 440                 goto error_io;
 441         }
 442
 443         memset(&msg, 0, sizeof(msg));
 444         strncpy(msg.name, event->name, sizeof(msg.name));
 445         ret = send_payload(app->sock, &msg, sizeof(msg));
 446         if (ret < 0) {
 447                 goto error_io;
 448         }
 449
 450         ret = recv_reply(app->sock, &reply, sizeof(reply));
 451         if (ret < 0) {
 452                 goto error_io;
 453         }
 454
 455         reply_ret_code = be32toh(reply.ret_code);
 456         log_reply_code(reply_ret_code);
 457         switch (reply_ret_code) {
 458         case AGENT_RET_CODE_SUCCESS:
 459                 break;
 460         case AGENT_RET_CODE_UNKNOWN_NAME:
 461                 ret = LTTNG_ERR_UST_EVENT_NOT_FOUND;
 462                 goto error;
 463         default:
 464                 ret = LTTNG_ERR_UNK;
 465                 goto error;
 466         }
 467
 468         return LTTNG_OK;
 469
 470 error_io:
 471         ret = LTTNG_ERR_UST_DISABLE_FAIL;
 472 error:
 473         return ret;
 474 }
 475
 476 /*
 477  * Send back the registration DONE command to a given agent application.
 478  *
 479  * Return 0 on success or else a negative value.
 480  */
 481 int agent_send_registration_done(struct agent_app *app)
 482 {
 483         assert(app);
 484         assert(app->sock);
 485
 486         DBG("Agent sending registration done to app socket %d", app->sock->fd);
 487
 488         return send_header(app->sock, 0, AGENT_CMD_REG_DONE, 0);
 489 }
 490
 491 /*
 492  * Enable agent event on every agent applications registered with the session
 493  * daemon.
 494  *
 495  * Return LTTNG_OK on success or else a LTTNG_ERR* code.
 496  */
 497 int agent_enable_event(struct agent_event *event,
 498                 enum lttng_domain_type domain)
 499 {
 500         int ret;
 501         struct agent_app *app;
 502         struct lttng_ht_iter iter;
 503
 504         assert(event);
 505
 506         rcu_read_lock();
 507
 508         cds_lfht_for_each_entry(agent_apps_ht_by_sock->ht, &iter.iter, app,
 509                         node.node) {
 510                 if (app->domain != domain) {
 511                         continue;
 512                 }
 513
 514                 /* Enable event on agent application through TCP socket. */
 515                 ret = enable_event(app, event);
 516                 if (ret != LTTNG_OK) {
 517                         goto error;
 518                 }
 519         }
 520
 521         event->enabled = 1;
 522         ret = LTTNG_OK;
 523
 524 error:
 525         rcu_read_unlock();
 526         return ret;
 527 }
 528
 529 /*
 530  * Disable agent event on every agent applications registered with the session
 531  * daemon.
 532  *
 533  * Return LTTNG_OK on success or else a LTTNG_ERR* code.
 534  */
 535 int agent_disable_event(struct agent_event *event,
 536                 enum lttng_domain_type domain)
 537 {
 538         int ret = LTTNG_OK;
 539         struct agent_app *app;
 540         struct lttng_ht_iter iter;
 541
 542         assert(event);
 543         if (!event->enabled) {
 544                 goto end;
 545         }
 546
 547         rcu_read_lock();
 548
 549         cds_lfht_for_each_entry(agent_apps_ht_by_sock->ht, &iter.iter, app,
 550                         node.node) {
 551                 if (app->domain != domain) {
 552                         continue;
 553                 }
 554
 555                 /* Enable event on agent application through TCP socket. */
 556                 ret = disable_event(app, event);
 557                 if (ret != LTTNG_OK) {
 558                         goto error;
 559                 }
 560         }
 561
 562         event->enabled = 0;
 563
 564 error:
 565         rcu_read_unlock();
 566 end:
 567         return ret;
 568 }
 569
 570 /*
 571  * Ask every agent for the list of possible event. Events is allocated with the
 572  * events of every agent application.
 573  *
 574  * Return the number of events or else a negative value.
 575  */
 576 int agent_list_events(struct lttng_event **events,
 577                 enum lttng_domain_type domain)
 578 {
 579         int ret;
 580         size_t nbmem, count = 0;
 581         struct agent_app *app;
 582         struct lttng_event *tmp_events = NULL;
 583         struct lttng_ht_iter iter;
 584
 585         assert(events);
 586
 587         DBG2("Agent listing events for domain %d", domain);
 588
 589         nbmem = UST_APP_EVENT_LIST_SIZE;
 590         tmp_events = zmalloc(nbmem * sizeof(*tmp_events));
 591         if (!tmp_events) {
 592                 PERROR("zmalloc agent list events");
 593                 ret = -ENOMEM;
 594                 goto error;
 595         }
 596
 597         rcu_read_lock();
 598         cds_lfht_for_each_entry(agent_apps_ht_by_sock->ht, &iter.iter, app,
 599                         node.node) {
 600                 ssize_t nb_ev;
 601                 struct lttng_event *agent_events;
 602
 603                 /* Skip domain not asked by the list. */
 604                 if (app->domain != domain) {
 605                         continue;
 606                 }
 607
 608                 nb_ev = list_events(app, &agent_events);
 609                 if (nb_ev < 0) {
 610                         ret = nb_ev;
 611                         goto error_unlock;
 612                 }
 613
 614                 if (count + nb_ev > nbmem) {
 615                         /* In case the realloc fails, we free the memory */
 616                         struct lttng_event *new_tmp_events;
 617                         size_t new_nbmem;
 618
 619                         new_nbmem = max_t(size_t, count + nb_ev, nbmem << 1);
 620                         DBG2("Reallocating agent event list from %zu to %zu entries",
 621                                         nbmem, new_nbmem);
 622                         new_tmp_events = realloc(tmp_events,
 623                                 new_nbmem * sizeof(*new_tmp_events));
 624                         if (!new_tmp_events) {
 625                                 PERROR("realloc agent events");
 626                                 ret = -ENOMEM;
 627                                 free(agent_events);
 628                                 goto error_unlock;
 629                         }
 630                         /* Zero the new memory */
 631                         memset(new_tmp_events + nbmem, 0,
 632                                 (new_nbmem - nbmem) * sizeof(*new_tmp_events));
 633                         nbmem = new_nbmem;
 634                         tmp_events = new_tmp_events;
 635                 }
 636                 memcpy(tmp_events + count, agent_events,
 637                         nb_ev * sizeof(*tmp_events));
 638                 free(agent_events);
 639                 count += nb_ev;
 640         }
 641         rcu_read_unlock();
 642
 643         ret = count;
 644         *events = tmp_events;
 645         return ret;
 646
 647 error_unlock:
 648         rcu_read_unlock();
 649 error:
 650         free(tmp_events);
 651         return ret;
 652 }
 653
 654 /*
 655  * Create a agent app object using the given PID.
 656  *
 657  * Return newly allocated object or else NULL on error.
 658  */
 659 struct agent_app *agent_create_app(pid_t pid, enum lttng_domain_type domain,
 660                 struct lttcomm_sock *sock)
 661 {
 662         struct agent_app *app;
 663
 664         assert(sock);
 665
 666         app = zmalloc(sizeof(*app));
 667         if (!app) {
 668                 PERROR("zmalloc agent create");
 669                 goto error;
 670         }
 671
 672         app->pid = pid;
 673         app->domain = domain;
 674         app->sock = sock;
 675         lttng_ht_node_init_ulong(&app->node, (unsigned long) app->sock->fd);
 676
 677 error:
 678         return app;
 679 }
 680
 681 /*
 682  * Lookup agent app by socket in the global hash table.
 683  *
 684  * RCU read side lock MUST be acquired.
 685  *
 686  * Return object if found else NULL.
 687  */
 688 struct agent_app *agent_find_app_by_sock(int sock)
 689 {
 690         struct lttng_ht_node_ulong *node;
 691         struct lttng_ht_iter iter;
 692         struct agent_app *app;
 693
 694         assert(sock >= 0);
 695
 696         lttng_ht_lookup(agent_apps_ht_by_sock, (void *)((unsigned long) sock), &iter);
 697         node = lttng_ht_iter_get_node_ulong(&iter);
 698         if (node == NULL) {
 699                 goto error;
 700         }
 701         app = caa_container_of(node, struct agent_app, node);
 702
 703         DBG3("Agent app pid %d found by sock %d.", app->pid, sock);
 704         return app;
 705
 706 error:
 707         DBG3("Agent app NOT found by sock %d.", sock);
 708         return NULL;
 709 }
 710
 711 /*
 712  * Add agent application object to the global hash table.
 713  */
 714 void agent_add_app(struct agent_app *app)
 715 {
 716         assert(app);
 717
 718         DBG3("Agent adding app sock: %d and pid: %d to ht", app->sock->fd, app->pid);
 719         lttng_ht_add_unique_ulong(agent_apps_ht_by_sock, &app->node);
 720 }
 721
 722 /*
 723  * Delete agent application from the global hash table.
 724  *
 725  * rcu_read_lock() must be held by the caller.
 726  */
 727 void agent_delete_app(struct agent_app *app)
 728 {
 729         int ret;
 730         struct lttng_ht_iter iter;
 731
 732         assert(app);
 733
 734         DBG3("Agent deleting app pid: %d and sock: %d", app->pid, app->sock->fd);
 735
 736         iter.iter.node = &app->node.node;
 737         ret = lttng_ht_del(agent_apps_ht_by_sock, &iter);
 738         assert(!ret);
 739 }
 740
 741 /*
 742  * Destroy an agent application object by detaching it from its corresponding
 743  * UST app if one is connected by closing the socket. Finally, perform a
 744  * delayed memory reclaim.
 745  */
 746 void agent_destroy_app(struct agent_app *app)
 747 {
 748         assert(app);
 749
 750         if (app->sock) {
 751                 app->sock->ops->close(app->sock);
 752                 lttcomm_destroy_sock(app->sock);
 753         }
 754
 755         call_rcu(&app->node.head, destroy_app_agent_rcu);
 756 }
 757
 758 /*
 759  * Initialize an already allocated agent object.
 760  *
 761  * Return 0 on success or else a negative errno value.
 762  */
 763 int agent_init(struct agent *agt)
 764 {
 765         int ret;
 766
 767         assert(agt);
 768
 769         agt->events = lttng_ht_new(0, LTTNG_HT_TYPE_STRING);
 770         if (!agt->events) {
 771                 ret = -ENOMEM;
 772                 goto error;
 773         }
 774         lttng_ht_node_init_u64(&agt->node, agt->domain);
 775
 776         return 0;
 777
 778 error:
 779         return ret;
 780 }
 781
 782 /*
 783  * Add agent object to the given hash table.
 784  */
 785 void agent_add(struct agent *agt, struct lttng_ht *ht)
 786 {
 787         assert(agt);
 788         assert(ht);
 789
 790         DBG3("Agent adding from domain %d", agt->domain);
 791
 792         rcu_read_lock();
 793         lttng_ht_add_unique_u64(ht, &agt->node);
 794         rcu_read_unlock();
 795 }
 796
 797 /*
 798  * Create an agent object for the given domain.
 799  *
 800  * Return the allocated agent or NULL on error.
 801  */
 802 struct agent *agent_create(enum lttng_domain_type domain)
 803 {
 804         int ret;
 805         struct agent *agt;
 806
 807         agt = zmalloc(sizeof(*agt));
 808         if (!agt) {
 809                 goto error;
 810         }
 811         agt->domain = domain;
 812
 813         ret = agent_init(agt);
 814         if (ret < 0) {
 815                 free(agt);
 816                 agt = NULL;
 817                 goto error;
 818         }
 819
 820 error:
 821         return agt;
 822 }
 823
 824 /*
 825  * Create a newly allocated agent event data structure. If name is valid, it's
 826  * copied into the created event.
 827  *
 828  * Return a new object else NULL on error.
 829  */
 830 struct agent_event *agent_create_event(const char *name,
 831                 struct lttng_filter_bytecode *filter)
 832 {
 833         struct agent_event *event;
 834
 835         DBG3("Agent create new event with name %s", name);
 836
 837         event = zmalloc(sizeof(*event));
 838         if (!event) {
 839                 goto error;
 840         }
 841
 842         if (name) {
 843                 strncpy(event->name, name, sizeof(event->name));
 844                 event->name[sizeof(event->name) - 1] = '\0';
 845                 lttng_ht_node_init_str(&event->node, event->name);
 846         }
 847
 848         if (filter) {
 849                 event->filter = filter;
 850         }
 851
 852 error:
 853         return event;
 854 }
 855
 856 /*
 857  * Unique add of a agent event to an agent object.
 858  */
 859 void agent_add_event(struct agent_event *event, struct agent *agt)
 860 {
 861         assert(event);
 862         assert(agt);
 863         assert(agt->events);
 864
 865         DBG3("Agent adding event %s", event->name);
 866
 867         rcu_read_lock();
 868         add_unique_agent_event(agt->events, event);
 869         rcu_read_unlock();
 870         agt->being_used = 1;
 871 }
 872
 873 /*
 874  * Find a agent event in the given agent using name.
 875  *
 876  * RCU read side lock MUST be acquired.
 877  *
 878  * Return object if found else NULL.
 879  */
 880 struct agent_event *agent_find_event_by_name(const char *name,
 881                 struct agent *agt)
 882 {
 883         struct lttng_ht_node_str *node;
 884         struct lttng_ht_iter iter;
 885         struct lttng_ht *ht;
 886         struct agent_ht_key key;
 887
 888         assert(name);
 889         assert(agt);
 890         assert(agt->events);
 891
 892         ht = agt->events;
 893         key.name = name;
 894
 895         cds_lfht_lookup(ht->ht, ht->hash_fct((void *) name, lttng_ht_seed),
 896                         ht_match_event_by_name, &key, &iter.iter);
 897         node = lttng_ht_iter_get_node_str(&iter);
 898         if (node == NULL) {
 899                 goto error;
 900         }
 901
 902         DBG3("Agent event found %s by name.", name);
 903         return caa_container_of(node, struct agent_event, node);
 904
 905 error:
 906         DBG3("Agent NOT found by name %s.", name);
 907         return NULL;
 908 }
 909
 910 /*
 911  * Find a agent event in the given agent using name and loglevel.
 912  *
 913  * RCU read side lock MUST be acquired.
 914  *
 915  * Return object if found else NULL.
 916  */
 917 struct agent_event *agent_find_event(const char *name, int loglevel,
 918                 struct agent *agt)
 919 {
 920         struct lttng_ht_node_str *node;
 921         struct lttng_ht_iter iter;
 922         struct lttng_ht *ht;
 923         struct agent_ht_key key;
 924
 925         assert(name);
 926         assert(agt);
 927         assert(agt->events);
 928
 929         ht = agt->events;
 930         key.name = name;
 931         key.loglevel = loglevel;
 932
 933         cds_lfht_lookup(ht->ht, ht->hash_fct((void *) name, lttng_ht_seed),
 934                         ht_match_event, &key, &iter.iter);
 935         node = lttng_ht_iter_get_node_str(&iter);
 936         if (node == NULL) {
 937                 goto error;
 938         }
 939
 940         DBG3("Agent event found %s.", name);
 941         return caa_container_of(node, struct agent_event, node);
 942
 943 error:
 944         DBG3("Agent event NOT found %s.", name);
 945         return NULL;
 946 }
 947
 948 /*
 949  * Free given agent event. This event must not be globally visible at this
 950  * point (only expected to be used on failure just after event creation). After
 951  * this call, the pointer is not usable anymore.
 952  */
 953 void agent_destroy_event(struct agent_event *event)
 954 {
 955         assert(event);
 956
 957         free(event->filter);
 958         free(event->filter_expression);
 959         free(event);
 960 }
 961
 962 /*
 963  * Destroy an agent completely. Note that the given pointer is NOT freed
 964  * thus a reference to static or stack data can be passed to this function.
 965  */
 966 void agent_destroy(struct agent *agt)
 967 {
 968         struct lttng_ht_node_str *node;
 969         struct lttng_ht_iter iter;
 970
 971         assert(agt);
 972
 973         DBG3("Agent destroy");
 974
 975         /*
 976          * Just ignore if no events hash table exists. This is possible if for
 977          * instance an agent object was allocated but not initialized.
 978          */
 979         if (!agt->events) {
 980                 return;
 981         }
 982
 983         rcu_read_lock();
 984         cds_lfht_for_each_entry(agt->events->ht, &iter.iter, node, node) {
 985                 int ret;
 986                 struct agent_event *event;
 987
 988                 /*
 989                  * When destroying an event, we have to try to disable it on the agent
 990                  * side so the event stops generating data. The return value is not
 991                  * important since we have to continue anyway destroying the object.
 992                  */
 993                 event = caa_container_of(node, struct agent_event, node);
 994                 (void) agent_disable_event(event, agt->domain);
 995
 996                 ret = lttng_ht_del(agt->events, &iter);
 997                 assert(!ret);
 998                 call_rcu(&node->head, destroy_event_agent_rcu);
 999         }
1000         rcu_read_unlock();
1001
1002         ht_cleanup_push(agt->events);
1003 }
1004
1005 /*
1006  * Allocate agent_apps_ht_by_sock.
1007  */
1008 int agent_app_ht_alloc(void)
1009 {
1010         int ret = 0;
1011
1012         agent_apps_ht_by_sock = lttng_ht_new(0, LTTNG_HT_TYPE_ULONG);
1013         if (!agent_apps_ht_by_sock) {
1014                 ret = -1;
1015         }
1016
1017         return ret;
1018 }
1019
1020 /*
1021  * Destroy a agent application by socket.
1022  */
1023 void agent_destroy_app_by_sock(int sock)
1024 {
1025         struct agent_app *app;
1026
1027         assert(sock >= 0);
1028
1029         /*
1030          * Not finding an application is a very important error that should NEVER
1031          * happen. The hash table deletion is ONLY done through this call when the
1032          * main sessiond thread is torn down.
1033          */
1034         rcu_read_lock();
1035         app = agent_find_app_by_sock(sock);
1036         assert(app);
1037
1038         /* RCU read side lock is assumed to be held by this function. */
1039         agent_delete_app(app);
1040
1041         /* The application is freed in a RCU call but the socket is closed here. */
1042         agent_destroy_app(app);
1043         rcu_read_unlock();
1044 }
1045
1046 /*
1047  * Clean-up the agent app hash table and destroy it.
1048  */
1049 void agent_app_ht_clean(void)
1050 {
1051         struct lttng_ht_node_ulong *node;
1052         struct lttng_ht_iter iter;
1053
1054         if (!agent_apps_ht_by_sock) {
1055                 return;
1056         }
1057         rcu_read_lock();
1058         cds_lfht_for_each_entry(agent_apps_ht_by_sock->ht, &iter.iter, node, node) {
1059                 struct agent_app *app;
1060
1061                 app = caa_container_of(node, struct agent_app, node);
1062                 agent_destroy_app_by_sock(app->sock->fd);
1063         }
1064         rcu_read_unlock();
1065
1066         lttng_ht_destroy(agent_apps_ht_by_sock);
1067 }
1068
1069 /*
1070  * Update a agent application (given socket) using the given agent.
1071  *
1072  * Note that this function is most likely to be used with a tracing session
1073  * thus the caller should make sure to hold the appropriate lock(s).
1074  */
1075 void agent_update(struct agent *agt, int sock)
1076 {
1077         int ret;
1078         struct agent_app *app;
1079         struct agent_event *event;
1080         struct lttng_ht_iter iter;
1081
1082         assert(agt);
1083         assert(sock >= 0);
1084
1085         DBG("Agent updating app socket %d", sock);
1086
1087         rcu_read_lock();
1088         cds_lfht_for_each_entry(agt->events->ht, &iter.iter, event, node.node) {
1089                 /* Skip event if disabled. */
1090                 if (!event->enabled) {
1091                         continue;
1092                 }
1093
1094                 app = agent_find_app_by_sock(sock);
1095                 /*
1096                  * We are in the registration path thus if the application is gone,
1097                  * there is a serious code flow error.
1098                  */
1099                 assert(app);
1100
1101                 ret = enable_event(app, event);
1102                 if (ret != LTTNG_OK) {
1103                         DBG2("Agent update unable to enable event %s on app pid: %d sock %d",
1104                                         event->name, app->pid, app->sock->fd);
1105                         /* Let's try the others here and don't assume the app is dead. */
1106                         continue;
1107                 }
1108         }
1109         rcu_read_unlock();
1110 }