src/bin/lttng-sessiond/trace-ust.c

   1 /*
   2  * Copyright (C) 2011 - David Goulet <david.goulet@polymtl.ca>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License, version 2 only,
   6  * as published by the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11  * GNU General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU General Public License along
  14  * with this program; if not, write to the Free Software Foundation, Inc.,
  15  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  16  */
  17
  18 #define _GNU_SOURCE
  19 #include <stdio.h>
  20 #include <stdlib.h>
  21 #include <string.h>
  22 #include <unistd.h>
  23 #include <inttypes.h>
  24
  25 #include <common/common.h>
  26 #include <common/defaults.h>
  27
  28 #include "buffer-registry.h"
  29 #include "trace-ust.h"
  30 #include "utils.h"
  31
  32 /*
  33  * Match function for the events hash table lookup.
  34  *
  35  * Matches by name only. Used by the disable command.
  36  */
  37 int trace_ust_ht_match_event_by_name(struct cds_lfht_node *node,
  38                 const void *_key)
  39 {
  40         struct ltt_ust_event *event;
  41         const char *name;
  42
  43         assert(node);
  44         assert(_key);
  45
  46         event = caa_container_of(node, struct ltt_ust_event, node.node);
  47         name = _key;
  48
  49         /* Event name */
  50         if (strncmp(event->attr.name, name, sizeof(event->attr.name)) != 0) {
  51                 goto no_match;
  52         }
  53
  54         /* Match */
  55         return 1;
  56
  57 no_match:
  58         return 0;
  59 }
  60
  61 /*
  62  * Match function for the hash table lookup.
  63  *
  64  * It matches an ust event based on three attributes which are the event name,
  65  * the filter bytecode and the loglevel.
  66  */
  67 int trace_ust_ht_match_event(struct cds_lfht_node *node, const void *_key)
  68 {
  69         struct ltt_ust_event *event;
  70         const struct ltt_ust_ht_key *key;
  71
  72         assert(node);
  73         assert(_key);
  74
  75         event = caa_container_of(node, struct ltt_ust_event, node.node);
  76         key = _key;
  77
  78         /* Match the 4 elements of the key: name, filter, loglevel, exclusions. */
  79
  80         /* Event name */
  81         if (strncmp(event->attr.name, key->name, sizeof(event->attr.name)) != 0) {
  82                 goto no_match;
  83         }
  84
  85         /* Event loglevel. */
  86         if (event->attr.loglevel != key->loglevel) {
  87                 if (event->attr.loglevel_type == LTTNG_UST_LOGLEVEL_ALL
  88                                 && key->loglevel == 0 && event->attr.loglevel == -1) {
  89                         /*
  90                          * Match is accepted. This is because on event creation, the
  91                          * loglevel is set to -1 if the event loglevel type is ALL so 0 and
  92                          * -1 are accepted for this loglevel type since 0 is the one set by
  93                          * the API when receiving an enable event.
  94                          */
  95                 } else {
  96                         goto no_match;
  97                 }
  98         }
  99
 100         /* Only one of the filters is NULL, fail. */
 101         if ((key->filter && !event->filter) || (!key->filter && event->filter)) {
 102                 goto no_match;
 103         }
 104
 105         if (key->filter && event->filter) {
 106                 /* Both filters exists, check length followed by the bytecode. */
 107                 if (event->filter->len != key->filter->len ||
 108                                 memcmp(event->filter->data, key->filter->data,
 109                                         event->filter->len) != 0) {
 110                         goto no_match;
 111                 }
 112         }
 113
 114         /* If only one of the exclusions is NULL, fail. */
 115         if ((key->exclusion && !event->exclusion) || (!key->exclusion && event->exclusion)) {
 116                 goto no_match;
 117         }
 118
 119         if (key->exclusion && event->exclusion) {
 120                 /* Both exclusions exist; check count followed by names. */
 121                 if (event->exclusion->count != key->exclusion->count ||
 122                                 memcmp(event->exclusion->names, key->exclusion->names,
 123                                         event->exclusion->count * LTTNG_SYMBOL_NAME_LEN) != 0) {
 124                         goto no_match;
 125                 }
 126         }
 127         /* Match. */
 128         return 1;
 129
 130 no_match:
 131         return 0;
 132 }
 133
 134 /*
 135  * Find the channel in the hashtable and return channel pointer. RCU read side
 136  * lock MUST be acquired before calling this.
 137  */
 138 struct ltt_ust_channel *trace_ust_find_channel_by_name(struct lttng_ht *ht,
 139                 char *name)
 140 {
 141         struct lttng_ht_node_str *node;
 142         struct lttng_ht_iter iter;
 143
 144         /*
 145          * If we receive an empty string for channel name, it means the
 146          * default channel name is requested.
 147          */
 148         if (name[0] == '\0')
 149                 name = DEFAULT_CHANNEL_NAME;
 150
 151         lttng_ht_lookup(ht, (void *)name, &iter);
 152         node = lttng_ht_iter_get_node_str(&iter);
 153         if (node == NULL) {
 154                 goto error;
 155         }
 156
 157         DBG2("Trace UST channel %s found by name", name);
 158
 159         return caa_container_of(node, struct ltt_ust_channel, node);
 160
 161 error:
 162         DBG2("Trace UST channel %s not found by name", name);
 163         return NULL;
 164 }
 165
 166 /*
 167  * Find the event in the hashtable and return event pointer. RCU read side lock
 168  * MUST be acquired before calling this.
 169  */
 170 struct ltt_ust_event *trace_ust_find_event(struct lttng_ht *ht,
 171                 char *name, struct lttng_filter_bytecode *filter, int loglevel,
 172                 struct lttng_event_exclusion *exclusion)
 173 {
 174         struct lttng_ht_node_str *node;
 175         struct lttng_ht_iter iter;
 176         struct ltt_ust_ht_key key;
 177
 178         assert(name);
 179         assert(ht);
 180
 181         key.name = name;
 182         key.filter = filter;
 183         key.loglevel = loglevel;
 184         key.exclusion = exclusion;
 185
 186         cds_lfht_lookup(ht->ht, ht->hash_fct((void *) name, lttng_ht_seed),
 187                         trace_ust_ht_match_event, &key, &iter.iter);
 188         node = lttng_ht_iter_get_node_str(&iter);
 189         if (node == NULL) {
 190                 goto error;
 191         }
 192
 193         DBG2("Trace UST event %s found", key.name);
 194
 195         return caa_container_of(node, struct ltt_ust_event, node);
 196
 197 error:
 198         DBG2("Trace UST event %s NOT found", key.name);
 199         return NULL;
 200 }
 201
 202 /*
 203  * Lookup an agent in the session agents hash table by domain type and return
 204  * the object if found else NULL.
 205  *
 206  * RCU read side lock must be acquired before calling and only released
 207  * once the agent is no longer in scope or being used.
 208  */
 209 struct agent *trace_ust_find_agent(struct ltt_ust_session *session,
 210                 enum lttng_domain_type domain_type)
 211 {
 212         struct agent *agt = NULL;
 213         struct lttng_ht_node_u64 *node;
 214         struct lttng_ht_iter iter;
 215         uint64_t key;
 216
 217         assert(session);
 218
 219         DBG3("Trace ust agent lookup for domain %d", domain_type);
 220
 221         key = domain_type;
 222
 223         lttng_ht_lookup(session->agents, &key, &iter);
 224         node = lttng_ht_iter_get_node_u64(&iter);
 225         if (!node) {
 226                 goto end;
 227         }
 228         agt = caa_container_of(node, struct agent, node);
 229
 230 end:
 231         return agt;
 232 }
 233
 234 /*
 235  * Allocate and initialize a ust session data structure.
 236  *
 237  * Return pointer to structure or NULL.
 238  */
 239 struct ltt_ust_session *trace_ust_create_session(uint64_t session_id)
 240 {
 241         struct ltt_ust_session *lus;
 242
 243         /* Allocate a new ltt ust session */
 244         lus = zmalloc(sizeof(struct ltt_ust_session));
 245         if (lus == NULL) {
 246                 PERROR("create ust session zmalloc");
 247                 goto error;
 248         }
 249
 250         /* Init data structure */
 251         lus->id = session_id;
 252         lus->active = 0;
 253
 254         /* Set default metadata channel attribute. */
 255         lus->metadata_attr.overwrite = DEFAULT_CHANNEL_OVERWRITE;
 256         lus->metadata_attr.subbuf_size = default_get_metadata_subbuf_size();
 257         lus->metadata_attr.num_subbuf = DEFAULT_METADATA_SUBBUF_NUM;
 258         lus->metadata_attr.switch_timer_interval = DEFAULT_METADATA_SWITCH_TIMER;
 259         lus->metadata_attr.read_timer_interval = DEFAULT_METADATA_READ_TIMER;
 260         lus->metadata_attr.output = LTTNG_UST_MMAP;
 261
 262         /*
 263          * Default buffer type. This can be changed through an enable channel
 264          * requesting a different type. Note that this can only be changed once
 265          * during the session lifetime which is at the first enable channel and
 266          * only before start. The flag buffer_type_changed indicates the status.
 267          */
 268         lus->buffer_type = LTTNG_BUFFER_PER_UID;
 269         /* Once set to 1, the buffer_type is immutable for the session. */
 270         lus->buffer_type_changed = 0;
 271         /* Init it in case it get used after allocation. */
 272         CDS_INIT_LIST_HEAD(&lus->buffer_reg_uid_list);
 273
 274         /* Alloc UST global domain channels' HT */
 275         lus->domain_global.channels = lttng_ht_new(0, LTTNG_HT_TYPE_STRING);
 276         /* Alloc agent hash table. */
 277         lus->agents = lttng_ht_new(0, LTTNG_HT_TYPE_U64);
 278
 279         lus->consumer = consumer_create_output(CONSUMER_DST_LOCAL);
 280         if (lus->consumer == NULL) {
 281                 goto error_consumer;
 282         }
 283
 284         /*
 285          * The tmp_consumer stays NULL until a set_consumer_uri command is
 286          * executed. At this point, the consumer should be nullify until an
 287          * enable_consumer command. This assignment is symbolic since we've zmalloc
 288          * the struct.
 289          */
 290         lus->tmp_consumer = NULL;
 291
 292         DBG2("UST trace session create successful");
 293
 294         return lus;
 295
 296 error_consumer:
 297         ht_cleanup_push(lus->domain_global.channels);
 298         ht_cleanup_push(lus->agents);
 299         free(lus);
 300 error:
 301         return NULL;
 302 }
 303
 304 /*
 305  * Allocate and initialize a ust channel data structure.
 306  *
 307  * Return pointer to structure or NULL.
 308  */
 309 struct ltt_ust_channel *trace_ust_create_channel(struct lttng_channel *chan)
 310 {
 311         struct ltt_ust_channel *luc;
 312
 313         assert(chan);
 314
 315         luc = zmalloc(sizeof(struct ltt_ust_channel));
 316         if (luc == NULL) {
 317                 PERROR("ltt_ust_channel zmalloc");
 318                 goto error;
 319         }
 320
 321         /* Copy UST channel attributes */
 322         luc->attr.overwrite = chan->attr.overwrite;
 323         luc->attr.subbuf_size = chan->attr.subbuf_size;
 324         luc->attr.num_subbuf = chan->attr.num_subbuf;
 325         luc->attr.switch_timer_interval = chan->attr.switch_timer_interval;
 326         luc->attr.read_timer_interval = chan->attr.read_timer_interval;
 327         luc->attr.output = (enum lttng_ust_output) chan->attr.output;
 328
 329         /* Translate to UST output enum */
 330         switch (luc->attr.output) {
 331         default:
 332                 luc->attr.output = LTTNG_UST_MMAP;
 333                 break;
 334         }
 335
 336         /*
 337          * If we receive an empty string for channel name, it means the
 338          * default channel name is requested.
 339          */
 340         if (chan->name[0] == '\0') {
 341                 strncpy(luc->name, DEFAULT_CHANNEL_NAME, sizeof(luc->name));
 342         } else {
 343                 /* Copy channel name */
 344                 strncpy(luc->name, chan->name, sizeof(luc->name));
 345         }
 346         luc->name[LTTNG_UST_SYM_NAME_LEN - 1] = '\0';
 347
 348         /* Init node */
 349         lttng_ht_node_init_str(&luc->node, luc->name);
 350         CDS_INIT_LIST_HEAD(&luc->ctx_list);
 351
 352         /* Alloc hash tables */
 353         luc->events = lttng_ht_new(0, LTTNG_HT_TYPE_STRING);
 354         luc->ctx = lttng_ht_new(0, LTTNG_HT_TYPE_ULONG);
 355
 356         /* On-disk circular buffer parameters */
 357         luc->tracefile_size = chan->attr.tracefile_size;
 358         luc->tracefile_count = chan->attr.tracefile_count;
 359
 360         DBG2("Trace UST channel %s created", luc->name);
 361
 362 error:
 363         return luc;
 364 }
 365
 366 /*
 367  * Allocate and initialize a ust event. Set name and event type.
 368  * We own filter_expression, filter, and exclusion.
 369  *
 370  * Return pointer to structure or NULL.
 371  */
 372 struct ltt_ust_event *trace_ust_create_event(struct lttng_event *ev,
 373                 char *filter_expression,
 374                 struct lttng_filter_bytecode *filter,
 375                 struct lttng_event_exclusion *exclusion)
 376 {
 377         struct ltt_ust_event *lue;
 378
 379         assert(ev);
 380
 381         lue = zmalloc(sizeof(struct ltt_ust_event));
 382         if (lue == NULL) {
 383                 PERROR("ust event zmalloc");
 384                 goto error;
 385         }
 386
 387         switch (ev->type) {
 388         case LTTNG_EVENT_PROBE:
 389                 lue->attr.instrumentation = LTTNG_UST_PROBE;
 390                 break;
 391         case LTTNG_EVENT_FUNCTION:
 392                 lue->attr.instrumentation = LTTNG_UST_FUNCTION;
 393                 break;
 394         case LTTNG_EVENT_FUNCTION_ENTRY:
 395                 lue->attr.instrumentation = LTTNG_UST_FUNCTION;
 396                 break;
 397         case LTTNG_EVENT_TRACEPOINT:
 398                 lue->attr.instrumentation = LTTNG_UST_TRACEPOINT;
 399                 break;
 400         default:
 401                 ERR("Unknown ust instrumentation type (%d)", ev->type);
 402                 goto error_free_event;
 403         }
 404
 405         /* Copy event name */
 406         strncpy(lue->attr.name, ev->name, LTTNG_UST_SYM_NAME_LEN);
 407         lue->attr.name[LTTNG_UST_SYM_NAME_LEN - 1] = '\0';
 408
 409         switch (ev->loglevel_type) {
 410         case LTTNG_EVENT_LOGLEVEL_ALL:
 411                 lue->attr.loglevel_type = LTTNG_UST_LOGLEVEL_ALL;
 412                 lue->attr.loglevel = -1;        /* Force to -1 */
 413                 break;
 414         case LTTNG_EVENT_LOGLEVEL_RANGE:
 415                 lue->attr.loglevel_type = LTTNG_UST_LOGLEVEL_RANGE;
 416                 lue->attr.loglevel = ev->loglevel;
 417                 break;
 418         case LTTNG_EVENT_LOGLEVEL_SINGLE:
 419                 lue->attr.loglevel_type = LTTNG_UST_LOGLEVEL_SINGLE;
 420                 lue->attr.loglevel = ev->loglevel;
 421                 break;
 422         default:
 423                 ERR("Unknown ust loglevel type (%d)", ev->loglevel_type);
 424                 goto error_free_event;
 425         }
 426         /*
 427          * Fix for enabler race. Enable is now done explicitly by
 428          * sessiond after setting filter.
 429          */
 430         lue->attr.disabled = 1;
 431
 432         /* Same layout. */
 433         lue->filter_expression = filter_expression;
 434         lue->filter = (struct lttng_ust_filter_bytecode *) filter;
 435         lue->exclusion = (struct lttng_event_exclusion *) exclusion;
 436
 437         /* Init node */
 438         lttng_ht_node_init_str(&lue->node, lue->attr.name);
 439
 440         DBG2("Trace UST event %s, loglevel (%d,%d) created",
 441                 lue->attr.name, lue->attr.loglevel_type,
 442                 lue->attr.loglevel);
 443
 444         return lue;
 445
 446 error_free_event:
 447         free(lue);
 448 error:
 449         free(filter_expression);
 450         free(filter);
 451         free(exclusion);
 452         return NULL;
 453 }
 454
 455 static
 456 int trace_ust_context_type_event_to_ust(enum lttng_event_context_type type)
 457 {
 458         int utype;
 459
 460         switch (type) {
 461         case LTTNG_EVENT_CONTEXT_VTID:
 462                 utype = LTTNG_UST_CONTEXT_VTID;
 463                 break;
 464         case LTTNG_EVENT_CONTEXT_VPID:
 465                 utype = LTTNG_UST_CONTEXT_VPID;
 466                 break;
 467         case LTTNG_EVENT_CONTEXT_PTHREAD_ID:
 468                 utype = LTTNG_UST_CONTEXT_PTHREAD_ID;
 469                 break;
 470         case LTTNG_EVENT_CONTEXT_PROCNAME:
 471                 utype = LTTNG_UST_CONTEXT_PROCNAME;
 472                 break;
 473         case LTTNG_EVENT_CONTEXT_IP:
 474                 utype = LTTNG_UST_CONTEXT_IP;
 475                 break;
 476         case LTTNG_EVENT_CONTEXT_PERF_THREAD_COUNTER:
 477                 if (!ustctl_has_perf_counters()) {
 478                         utype = -1;
 479                         WARN("Perf counters not implemented in UST");
 480                 } else {
 481                         utype = LTTNG_UST_CONTEXT_PERF_THREAD_COUNTER;
 482                 }
 483                 break;
 484         default:
 485                 ERR("Invalid UST context");
 486                 utype = -1;
 487                 break;
 488         }
 489         return utype;
 490 }
 491
 492 /*
 493  * Return 1 if contexts match, 0 otherwise.
 494  */
 495 int trace_ust_match_context(struct ltt_ust_context *uctx,
 496                 struct lttng_event_context *ctx)
 497 {
 498         int utype;
 499
 500         utype = trace_ust_context_type_event_to_ust(ctx->ctx);
 501         if (utype < 0) {
 502                 return 0;
 503         }
 504         if (uctx->ctx.ctx != utype) {
 505                 return 0;
 506         }
 507         switch (utype) {
 508         case LTTNG_UST_CONTEXT_PERF_THREAD_COUNTER:
 509                 if (uctx->ctx.u.perf_counter.type
 510                                 != ctx->u.perf_counter.type) {
 511                         return 0;
 512                 }
 513                 if (uctx->ctx.u.perf_counter.config
 514                                 != ctx->u.perf_counter.config) {
 515                         return 0;
 516                 }
 517                 if (strncmp(uctx->ctx.u.perf_counter.name,
 518                                 ctx->u.perf_counter.name,
 519                                 LTTNG_UST_SYM_NAME_LEN)) {
 520                         return 0;
 521                 }
 522                 break;
 523         default:
 524                 break;
 525
 526         }
 527         return 1;
 528 }
 529
 530 /*
 531  * Allocate and initialize an UST context.
 532  *
 533  * Return pointer to structure or NULL.
 534  */
 535 struct ltt_ust_context *trace_ust_create_context(
 536                 struct lttng_event_context *ctx)
 537 {
 538         struct ltt_ust_context *uctx;
 539         int utype;
 540
 541         assert(ctx);
 542
 543         utype = trace_ust_context_type_event_to_ust(ctx->ctx);
 544         if (utype < 0) {
 545                 return NULL;
 546         }
 547
 548         uctx = zmalloc(sizeof(struct ltt_ust_context));
 549         if (uctx == NULL) {
 550                 PERROR("zmalloc ltt_ust_context");
 551                 goto error;
 552         }
 553
 554         uctx->ctx.ctx = (enum lttng_ust_context_type) utype;
 555         switch (utype) {
 556         case LTTNG_UST_CONTEXT_PERF_THREAD_COUNTER:
 557                 uctx->ctx.u.perf_counter.type = ctx->u.perf_counter.type;
 558                 uctx->ctx.u.perf_counter.config = ctx->u.perf_counter.config;
 559                 strncpy(uctx->ctx.u.perf_counter.name, ctx->u.perf_counter.name,
 560                                 LTTNG_UST_SYM_NAME_LEN);
 561                 uctx->ctx.u.perf_counter.name[LTTNG_UST_SYM_NAME_LEN - 1] = '\0';
 562                 break;
 563         default:
 564                 break;
 565         }
 566         lttng_ht_node_init_ulong(&uctx->node, (unsigned long) uctx->ctx.ctx);
 567
 568         return uctx;
 569
 570 error:
 571         return NULL;
 572 }
 573
 574 /*
 575  * RCU safe free context structure.
 576  */
 577 static void destroy_context_rcu(struct rcu_head *head)
 578 {
 579         struct lttng_ht_node_ulong *node =
 580                 caa_container_of(head, struct lttng_ht_node_ulong, head);
 581         struct ltt_ust_context *ctx =
 582                 caa_container_of(node, struct ltt_ust_context, node);
 583
 584         free(ctx);
 585 }
 586
 587 /*
 588  * Cleanup UST context hash table.
 589  */
 590 static void destroy_contexts(struct lttng_ht *ht)
 591 {
 592         int ret;
 593         struct lttng_ht_node_ulong *node;
 594         struct lttng_ht_iter iter;
 595         struct ltt_ust_context *ctx;
 596
 597         assert(ht);
 598
 599         rcu_read_lock();
 600         cds_lfht_for_each_entry(ht->ht, &iter.iter, node, node) {
 601                 /* Remove from ordered list. */
 602                 ctx = caa_container_of(node, struct ltt_ust_context, node);
 603                 cds_list_del(&ctx->list);
 604                 /* Remove from channel's hash table. */
 605                 ret = lttng_ht_del(ht, &iter);
 606                 if (!ret) {
 607                         call_rcu(&node->head, destroy_context_rcu);
 608                 }
 609         }
 610         rcu_read_unlock();
 611
 612         ht_cleanup_push(ht);
 613 }
 614
 615 /*
 616  * Cleanup ust event structure.
 617  */
 618 void trace_ust_destroy_event(struct ltt_ust_event *event)
 619 {
 620         assert(event);
 621
 622         DBG2("Trace destroy UST event %s", event->attr.name);
 623         free(event->filter_expression);
 624         free(event->filter);
 625         free(event->exclusion);
 626         free(event);
 627 }
 628
 629 /*
 630  * URCU intermediate call to complete destroy event.
 631  */
 632 static void destroy_event_rcu(struct rcu_head *head)
 633 {
 634         struct lttng_ht_node_str *node =
 635                 caa_container_of(head, struct lttng_ht_node_str, head);
 636         struct ltt_ust_event *event =
 637                 caa_container_of(node, struct ltt_ust_event, node);
 638
 639         trace_ust_destroy_event(event);
 640 }
 641
 642 /*
 643  * Cleanup UST events hashtable.
 644  */
 645 static void destroy_events(struct lttng_ht *events)
 646 {
 647         int ret;
 648         struct lttng_ht_node_str *node;
 649         struct lttng_ht_iter iter;
 650
 651         assert(events);
 652
 653         rcu_read_lock();
 654         cds_lfht_for_each_entry(events->ht, &iter.iter, node, node) {
 655                 ret = lttng_ht_del(events, &iter);
 656                 assert(!ret);
 657                 call_rcu(&node->head, destroy_event_rcu);
 658         }
 659         rcu_read_unlock();
 660
 661         ht_cleanup_push(events);
 662 }
 663
 664 /*
 665  * Cleanup ust channel structure.
 666  *
 667  * Should _NOT_ be called with RCU read lock held.
 668  */
 669 static void _trace_ust_destroy_channel(struct ltt_ust_channel *channel)
 670 {
 671         assert(channel);
 672
 673         DBG2("Trace destroy UST channel %s", channel->name);
 674
 675         /* Destroying all events of the channel */
 676         destroy_events(channel->events);
 677         /* Destroying all context of the channel */
 678         destroy_contexts(channel->ctx);
 679
 680         free(channel);
 681 }
 682
 683 /*
 684  * URCU intermediate call to complete destroy channel.
 685  */
 686 static void destroy_channel_rcu(struct rcu_head *head)
 687 {
 688         struct lttng_ht_node_str *node =
 689                 caa_container_of(head, struct lttng_ht_node_str, head);
 690         struct ltt_ust_channel *channel =
 691                 caa_container_of(node, struct ltt_ust_channel, node);
 692
 693         _trace_ust_destroy_channel(channel);
 694 }
 695
 696 void trace_ust_destroy_channel(struct ltt_ust_channel *channel)
 697 {
 698         call_rcu(&channel->node.head, destroy_channel_rcu);
 699 }
 700
 701 /*
 702  * Remove an UST channel from a channel HT.
 703  */
 704 void trace_ust_delete_channel(struct lttng_ht *ht,
 705                 struct ltt_ust_channel *channel)
 706 {
 707         int ret;
 708         struct lttng_ht_iter iter;
 709
 710         assert(ht);
 711         assert(channel);
 712
 713         iter.iter.node = &channel->node.node;
 714         ret = lttng_ht_del(ht, &iter);
 715         assert(!ret);
 716 }
 717
 718 /*
 719  * Iterate over a hash table containing channels and cleanup safely.
 720  */
 721 static void destroy_channels(struct lttng_ht *channels)
 722 {
 723         int ret;
 724         struct lttng_ht_node_str *node;
 725         struct lttng_ht_iter iter;
 726
 727         assert(channels);
 728
 729         rcu_read_lock();
 730
 731         cds_lfht_for_each_entry(channels->ht, &iter.iter, node, node) {
 732                 ret = lttng_ht_del(channels, &iter);
 733                 assert(!ret);
 734                 call_rcu(&node->head, destroy_channel_rcu);
 735         }
 736         rcu_read_unlock();
 737
 738         ht_cleanup_push(channels);
 739 }
 740
 741 /*
 742  * Cleanup UST global domain.
 743  */
 744 static void destroy_domain_global(struct ltt_ust_domain_global *dom)
 745 {
 746         assert(dom);
 747
 748         destroy_channels(dom->channels);
 749 }
 750
 751 /*
 752  * Cleanup ust session structure
 753  *
 754  * Should *NOT* be called with RCU read-side lock held.
 755  */
 756 void trace_ust_destroy_session(struct ltt_ust_session *session)
 757 {
 758         struct agent *agt;
 759         struct buffer_reg_uid *reg, *sreg;
 760         struct lttng_ht_iter iter;
 761
 762         assert(session);
 763
 764         DBG2("Trace UST destroy session %" PRIu64, session->id);
 765
 766         /* Cleaning up UST domain */
 767         destroy_domain_global(&session->domain_global);
 768
 769         rcu_read_lock();
 770         cds_lfht_for_each_entry(session->agents->ht, &iter.iter, agt, node.node) {
 771                 lttng_ht_del(session->agents, &iter);
 772                 agent_destroy(agt);
 773         }
 774         rcu_read_unlock();
 775
 776         /* Cleanup UID buffer registry object(s). */
 777         cds_list_for_each_entry_safe(reg, sreg, &session->buffer_reg_uid_list,
 778                         lnode) {
 779                 cds_list_del(&reg->lnode);
 780                 buffer_reg_uid_remove(reg);
 781                 buffer_reg_uid_destroy(reg, session->consumer);
 782         }
 783
 784         consumer_destroy_output(session->consumer);
 785         consumer_destroy_output(session->tmp_consumer);
 786
 787         free(session);
 788 }