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 struct agent *trace_ust_find_agent(struct ltt_ust_session *session,
 207                 enum lttng_domain_type domain_type)
 208 {
 209         struct agent *agt = NULL;
 210         struct lttng_ht_node_u64 *node;
 211         struct lttng_ht_iter iter;
 212         uint64_t key;
 213
 214         assert(session);
 215
 216         DBG3("Trace ust agent lookup for domain %d", domain_type);
 217
 218         key = domain_type;
 219
 220         lttng_ht_lookup(session->agents, &key, &iter);
 221         node = lttng_ht_iter_get_node_u64(&iter);
 222         if (!node) {
 223                 goto end;
 224         }
 225         agt = caa_container_of(node, struct agent, node);
 226
 227 end:
 228         return agt;
 229 }
 230
 231 /*
 232  * Allocate and initialize a ust session data structure.
 233  *
 234  * Return pointer to structure or NULL.
 235  */
 236 struct ltt_ust_session *trace_ust_create_session(uint64_t session_id)
 237 {
 238         struct ltt_ust_session *lus;
 239
 240         /* Allocate a new ltt ust session */
 241         lus = zmalloc(sizeof(struct ltt_ust_session));
 242         if (lus == NULL) {
 243                 PERROR("create ust session zmalloc");
 244                 goto error;
 245         }
 246
 247         /* Init data structure */
 248         lus->id = session_id;
 249         lus->active = 0;
 250
 251         /* Set default metadata channel attribute. */
 252         lus->metadata_attr.overwrite = DEFAULT_CHANNEL_OVERWRITE;
 253         lus->metadata_attr.subbuf_size = default_get_metadata_subbuf_size();
 254         lus->metadata_attr.num_subbuf = DEFAULT_METADATA_SUBBUF_NUM;
 255         lus->metadata_attr.switch_timer_interval = DEFAULT_METADATA_SWITCH_TIMER;
 256         lus->metadata_attr.read_timer_interval = DEFAULT_METADATA_READ_TIMER;
 257         lus->metadata_attr.output = LTTNG_UST_MMAP;
 258
 259         /*
 260          * Default buffer type. This can be changed through an enable channel
 261          * requesting a different type. Note that this can only be changed once
 262          * during the session lifetime which is at the first enable channel and
 263          * only before start. The flag buffer_type_changed indicates the status.
 264          */
 265         lus->buffer_type = LTTNG_BUFFER_PER_UID;
 266         /* Once set to 1, the buffer_type is immutable for the session. */
 267         lus->buffer_type_changed = 0;
 268         /* Init it in case it get used after allocation. */
 269         CDS_INIT_LIST_HEAD(&lus->buffer_reg_uid_list);
 270
 271         /* Alloc UST global domain channels' HT */
 272         lus->domain_global.channels = lttng_ht_new(0, LTTNG_HT_TYPE_STRING);
 273         /* Alloc agent hash table. */
 274         lus->agents = lttng_ht_new(0, LTTNG_HT_TYPE_U64);
 275
 276         lus->consumer = consumer_create_output(CONSUMER_DST_LOCAL);
 277         if (lus->consumer == NULL) {
 278                 goto error_consumer;
 279         }
 280
 281         /*
 282          * The tmp_consumer stays NULL until a set_consumer_uri command is
 283          * executed. At this point, the consumer should be nullify until an
 284          * enable_consumer command. This assignment is symbolic since we've zmalloc
 285          * the struct.
 286          */
 287         lus->tmp_consumer = NULL;
 288
 289         DBG2("UST trace session create successful");
 290
 291         return lus;
 292
 293 error_consumer:
 294         ht_cleanup_push(lus->domain_global.channels);
 295         ht_cleanup_push(lus->agents);
 296         free(lus);
 297 error:
 298         return NULL;
 299 }
 300
 301 /*
 302  * Allocate and initialize a ust channel data structure.
 303  *
 304  * Return pointer to structure or NULL.
 305  */
 306 struct ltt_ust_channel *trace_ust_create_channel(struct lttng_channel *chan)
 307 {
 308         struct ltt_ust_channel *luc;
 309
 310         assert(chan);
 311
 312         luc = zmalloc(sizeof(struct ltt_ust_channel));
 313         if (luc == NULL) {
 314                 PERROR("ltt_ust_channel zmalloc");
 315                 goto error;
 316         }
 317
 318         /* Copy UST channel attributes */
 319         luc->attr.overwrite = chan->attr.overwrite;
 320         luc->attr.subbuf_size = chan->attr.subbuf_size;
 321         luc->attr.num_subbuf = chan->attr.num_subbuf;
 322         luc->attr.switch_timer_interval = chan->attr.switch_timer_interval;
 323         luc->attr.read_timer_interval = chan->attr.read_timer_interval;
 324         luc->attr.output = (enum lttng_ust_output) chan->attr.output;
 325
 326         /* Translate to UST output enum */
 327         switch (luc->attr.output) {
 328         default:
 329                 luc->attr.output = LTTNG_UST_MMAP;
 330                 break;
 331         }
 332
 333         /*
 334          * If we receive an empty string for channel name, it means the
 335          * default channel name is requested.
 336          */
 337         if (chan->name[0] == '\0') {
 338                 strncpy(luc->name, DEFAULT_CHANNEL_NAME, sizeof(luc->name));
 339         } else {
 340                 /* Copy channel name */
 341                 strncpy(luc->name, chan->name, sizeof(luc->name));
 342         }
 343         luc->name[LTTNG_UST_SYM_NAME_LEN - 1] = '\0';
 344
 345         /* Init node */
 346         lttng_ht_node_init_str(&luc->node, luc->name);
 347         CDS_INIT_LIST_HEAD(&luc->ctx_list);
 348
 349         /* Alloc hash tables */
 350         luc->events = lttng_ht_new(0, LTTNG_HT_TYPE_STRING);
 351         luc->ctx = lttng_ht_new(0, LTTNG_HT_TYPE_ULONG);
 352
 353         /* On-disk circular buffer parameters */
 354         luc->tracefile_size = chan->attr.tracefile_size;
 355         luc->tracefile_count = chan->attr.tracefile_count;
 356
 357         DBG2("Trace UST channel %s created", luc->name);
 358
 359 error:
 360         return luc;
 361 }
 362
 363 /*
 364  * Allocate and initialize a ust event. Set name and event type.
 365  *
 366  * Return pointer to structure or NULL.
 367  */
 368 struct ltt_ust_event *trace_ust_create_event(struct lttng_event *ev,
 369                 char *filter_expression,
 370                 struct lttng_filter_bytecode *filter,
 371                 struct lttng_event_exclusion *exclusion)
 372 {
 373         struct ltt_ust_event *lue;
 374
 375         assert(ev);
 376
 377         lue = zmalloc(sizeof(struct ltt_ust_event));
 378         if (lue == NULL) {
 379                 PERROR("ust event zmalloc");
 380                 goto error;
 381         }
 382
 383         switch (ev->type) {
 384         case LTTNG_EVENT_PROBE:
 385                 lue->attr.instrumentation = LTTNG_UST_PROBE;
 386                 break;
 387         case LTTNG_EVENT_FUNCTION:
 388                 lue->attr.instrumentation = LTTNG_UST_FUNCTION;
 389                 break;
 390         case LTTNG_EVENT_FUNCTION_ENTRY:
 391                 lue->attr.instrumentation = LTTNG_UST_FUNCTION;
 392                 break;
 393         case LTTNG_EVENT_TRACEPOINT:
 394                 lue->attr.instrumentation = LTTNG_UST_TRACEPOINT;
 395                 break;
 396         default:
 397                 ERR("Unknown ust instrumentation type (%d)", ev->type);
 398                 goto error_free_event;
 399         }
 400
 401         /* Copy event name */
 402         strncpy(lue->attr.name, ev->name, LTTNG_UST_SYM_NAME_LEN);
 403         lue->attr.name[LTTNG_UST_SYM_NAME_LEN - 1] = '\0';
 404
 405         switch (ev->loglevel_type) {
 406         case LTTNG_EVENT_LOGLEVEL_ALL:
 407                 lue->attr.loglevel_type = LTTNG_UST_LOGLEVEL_ALL;
 408                 lue->attr.loglevel = -1;        /* Force to -1 */
 409                 break;
 410         case LTTNG_EVENT_LOGLEVEL_RANGE:
 411                 lue->attr.loglevel_type = LTTNG_UST_LOGLEVEL_RANGE;
 412                 lue->attr.loglevel = ev->loglevel;
 413                 break;
 414         case LTTNG_EVENT_LOGLEVEL_SINGLE:
 415                 lue->attr.loglevel_type = LTTNG_UST_LOGLEVEL_SINGLE;
 416                 lue->attr.loglevel = ev->loglevel;
 417                 break;
 418         default:
 419                 ERR("Unknown ust loglevel type (%d)", ev->loglevel_type);
 420                 goto error_free_event;
 421         }
 422
 423         /* Same layout. */
 424         lue->filter_expression = filter_expression;
 425         lue->filter = (struct lttng_ust_filter_bytecode *) filter;
 426         lue->exclusion = (struct lttng_event_exclusion *) exclusion;
 427
 428         /* Init node */
 429         lttng_ht_node_init_str(&lue->node, lue->attr.name);
 430
 431         DBG2("Trace UST event %s, loglevel (%d,%d) created",
 432                 lue->attr.name, lue->attr.loglevel_type,
 433                 lue->attr.loglevel);
 434
 435         return lue;
 436
 437 error_free_event:
 438         free(lue);
 439 error:
 440         return NULL;
 441 }
 442
 443 static
 444 int trace_ust_context_type_event_to_ust(enum lttng_event_context_type type)
 445 {
 446         int utype;
 447
 448         switch (type) {
 449         case LTTNG_EVENT_CONTEXT_VTID:
 450                 utype = LTTNG_UST_CONTEXT_VTID;
 451                 break;
 452         case LTTNG_EVENT_CONTEXT_VPID:
 453                 utype = LTTNG_UST_CONTEXT_VPID;
 454                 break;
 455         case LTTNG_EVENT_CONTEXT_PTHREAD_ID:
 456                 utype = LTTNG_UST_CONTEXT_PTHREAD_ID;
 457                 break;
 458         case LTTNG_EVENT_CONTEXT_PROCNAME:
 459                 utype = LTTNG_UST_CONTEXT_PROCNAME;
 460                 break;
 461         case LTTNG_EVENT_CONTEXT_IP:
 462                 utype = LTTNG_UST_CONTEXT_IP;
 463                 break;
 464         case LTTNG_EVENT_CONTEXT_PERF_THREAD_COUNTER:
 465                 utype = LTTNG_UST_CONTEXT_PERF_THREAD_COUNTER;
 466                 break;
 467         default:
 468                 ERR("Invalid UST context");
 469                 utype = -1;
 470                 break;
 471         }
 472         return utype;
 473 }
 474
 475 /*
 476  * Return 1 if contexts match, 0 otherwise.
 477  */
 478 int trace_ust_match_context(struct ltt_ust_context *uctx,
 479                 struct lttng_event_context *ctx)
 480 {
 481         int utype;
 482
 483         utype = trace_ust_context_type_event_to_ust(ctx->ctx);
 484         if (utype < 0) {
 485                 return 0;
 486         }
 487         if (uctx->ctx.ctx != utype) {
 488                 return 0;
 489         }
 490         switch (utype) {
 491         case LTTNG_UST_CONTEXT_PERF_THREAD_COUNTER:
 492                 if (uctx->ctx.u.perf_counter.type
 493                                 != ctx->u.perf_counter.type) {
 494                         return 0;
 495                 }
 496                 if (uctx->ctx.u.perf_counter.config
 497                                 != ctx->u.perf_counter.config) {
 498                         return 0;
 499                 }
 500                 if (strncmp(uctx->ctx.u.perf_counter.name,
 501                                 ctx->u.perf_counter.name,
 502                                 LTTNG_UST_SYM_NAME_LEN)) {
 503                         return 0;
 504                 }
 505                 break;
 506         default:
 507                 break;
 508
 509         }
 510         return 1;
 511 }
 512
 513 /*
 514  * Allocate and initialize an UST context.
 515  *
 516  * Return pointer to structure or NULL.
 517  */
 518 struct ltt_ust_context *trace_ust_create_context(
 519                 struct lttng_event_context *ctx)
 520 {
 521         struct ltt_ust_context *uctx;
 522         int utype;
 523
 524         assert(ctx);
 525
 526         utype = trace_ust_context_type_event_to_ust(ctx->ctx);
 527         if (utype < 0) {
 528                 return NULL;
 529         }
 530
 531         uctx = zmalloc(sizeof(struct ltt_ust_context));
 532         if (uctx == NULL) {
 533                 PERROR("zmalloc ltt_ust_context");
 534                 goto error;
 535         }
 536
 537         uctx->ctx.ctx = (enum lttng_ust_context_type) utype;
 538         switch (utype) {
 539         case LTTNG_UST_CONTEXT_PERF_THREAD_COUNTER:
 540                 uctx->ctx.u.perf_counter.type = ctx->u.perf_counter.type;
 541                 uctx->ctx.u.perf_counter.config = ctx->u.perf_counter.config;
 542                 strncpy(uctx->ctx.u.perf_counter.name, ctx->u.perf_counter.name,
 543                                 LTTNG_UST_SYM_NAME_LEN);
 544                 uctx->ctx.u.perf_counter.name[LTTNG_UST_SYM_NAME_LEN - 1] = '\0';
 545                 break;
 546         default:
 547                 break;
 548         }
 549         lttng_ht_node_init_ulong(&uctx->node, (unsigned long) uctx->ctx.ctx);
 550
 551         return uctx;
 552
 553 error:
 554         return NULL;
 555 }
 556
 557 /*
 558  * RCU safe free context structure.
 559  */
 560 static void destroy_context_rcu(struct rcu_head *head)
 561 {
 562         struct lttng_ht_node_ulong *node =
 563                 caa_container_of(head, struct lttng_ht_node_ulong, head);
 564         struct ltt_ust_context *ctx =
 565                 caa_container_of(node, struct ltt_ust_context, node);
 566
 567         free(ctx);
 568 }
 569
 570 /*
 571  * Cleanup UST context hash table.
 572  */
 573 static void destroy_contexts(struct lttng_ht *ht)
 574 {
 575         int ret;
 576         struct lttng_ht_node_ulong *node;
 577         struct lttng_ht_iter iter;
 578         struct ltt_ust_context *ctx;
 579
 580         assert(ht);
 581
 582         rcu_read_lock();
 583         cds_lfht_for_each_entry(ht->ht, &iter.iter, node, node) {
 584                 /* Remove from ordered list. */
 585                 ctx = caa_container_of(node, struct ltt_ust_context, node);
 586                 cds_list_del(&ctx->list);
 587                 /* Remove from channel's hash table. */
 588                 ret = lttng_ht_del(ht, &iter);
 589                 if (!ret) {
 590                         call_rcu(&node->head, destroy_context_rcu);
 591                 }
 592         }
 593         rcu_read_unlock();
 594
 595         ht_cleanup_push(ht);
 596 }
 597
 598 /*
 599  * Cleanup ust event structure.
 600  */
 601 void trace_ust_destroy_event(struct ltt_ust_event *event)
 602 {
 603         assert(event);
 604
 605         DBG2("Trace destroy UST event %s", event->attr.name);
 606         free(event->filter_expression);
 607         free(event->filter);
 608         free(event->exclusion);
 609         free(event);
 610 }
 611
 612 /*
 613  * URCU intermediate call to complete destroy event.
 614  */
 615 static void destroy_event_rcu(struct rcu_head *head)
 616 {
 617         struct lttng_ht_node_str *node =
 618                 caa_container_of(head, struct lttng_ht_node_str, head);
 619         struct ltt_ust_event *event =
 620                 caa_container_of(node, struct ltt_ust_event, node);
 621
 622         trace_ust_destroy_event(event);
 623 }
 624
 625 /*
 626  * Cleanup UST events hashtable.
 627  */
 628 static void destroy_events(struct lttng_ht *events)
 629 {
 630         int ret;
 631         struct lttng_ht_node_str *node;
 632         struct lttng_ht_iter iter;
 633
 634         assert(events);
 635
 636         rcu_read_lock();
 637         cds_lfht_for_each_entry(events->ht, &iter.iter, node, node) {
 638                 ret = lttng_ht_del(events, &iter);
 639                 assert(!ret);
 640                 call_rcu(&node->head, destroy_event_rcu);
 641         }
 642         rcu_read_unlock();
 643
 644         ht_cleanup_push(events);
 645 }
 646
 647 /*
 648  * Cleanup ust channel structure.
 649  *
 650  * Should _NOT_ be called with RCU read lock held.
 651  */
 652 static void _trace_ust_destroy_channel(struct ltt_ust_channel *channel)
 653 {
 654         assert(channel);
 655
 656         DBG2("Trace destroy UST channel %s", channel->name);
 657
 658         /* Destroying all events of the channel */
 659         destroy_events(channel->events);
 660         /* Destroying all context of the channel */
 661         destroy_contexts(channel->ctx);
 662
 663         free(channel);
 664 }
 665
 666 /*
 667  * URCU intermediate call to complete destroy channel.
 668  */
 669 static void destroy_channel_rcu(struct rcu_head *head)
 670 {
 671         struct lttng_ht_node_str *node =
 672                 caa_container_of(head, struct lttng_ht_node_str, head);
 673         struct ltt_ust_channel *channel =
 674                 caa_container_of(node, struct ltt_ust_channel, node);
 675
 676         _trace_ust_destroy_channel(channel);
 677 }
 678
 679 void trace_ust_destroy_channel(struct ltt_ust_channel *channel)
 680 {
 681         call_rcu(&channel->node.head, destroy_channel_rcu);
 682 }
 683
 684 /*
 685  * Remove an UST channel from a channel HT.
 686  */
 687 void trace_ust_delete_channel(struct lttng_ht *ht,
 688                 struct ltt_ust_channel *channel)
 689 {
 690         int ret;
 691         struct lttng_ht_iter iter;
 692
 693         assert(ht);
 694         assert(channel);
 695
 696         iter.iter.node = &channel->node.node;
 697         ret = lttng_ht_del(ht, &iter);
 698         assert(!ret);
 699 }
 700
 701 /*
 702  * Iterate over a hash table containing channels and cleanup safely.
 703  */
 704 static void destroy_channels(struct lttng_ht *channels)
 705 {
 706         int ret;
 707         struct lttng_ht_node_str *node;
 708         struct lttng_ht_iter iter;
 709
 710         assert(channels);
 711
 712         rcu_read_lock();
 713
 714         cds_lfht_for_each_entry(channels->ht, &iter.iter, node, node) {
 715                 ret = lttng_ht_del(channels, &iter);
 716                 assert(!ret);
 717                 call_rcu(&node->head, destroy_channel_rcu);
 718         }
 719         rcu_read_unlock();
 720
 721         ht_cleanup_push(channels);
 722 }
 723
 724 /*
 725  * Cleanup UST global domain.
 726  */
 727 static void destroy_domain_global(struct ltt_ust_domain_global *dom)
 728 {
 729         assert(dom);
 730
 731         destroy_channels(dom->channels);
 732 }
 733
 734 /*
 735  * Cleanup ust session structure
 736  *
 737  * Should *NOT* be called with RCU read-side lock held.
 738  */
 739 void trace_ust_destroy_session(struct ltt_ust_session *session)
 740 {
 741         struct agent *agt;
 742         struct buffer_reg_uid *reg, *sreg;
 743         struct lttng_ht_iter iter;
 744
 745         assert(session);
 746
 747         DBG2("Trace UST destroy session %" PRIu64, session->id);
 748
 749         /* Cleaning up UST domain */
 750         destroy_domain_global(&session->domain_global);
 751
 752         cds_lfht_for_each_entry(session->agents->ht, &iter.iter, agt, node.node) {
 753                 lttng_ht_del(session->agents, &iter);
 754                 agent_destroy(agt);
 755         }
 756
 757         /* Cleanup UID buffer registry object(s). */
 758         cds_list_for_each_entry_safe(reg, sreg, &session->buffer_reg_uid_list,
 759                         lnode) {
 760                 cds_list_del(&reg->lnode);
 761                 buffer_reg_uid_remove(reg);
 762                 buffer_reg_uid_destroy(reg, session->consumer);
 763         }
 764
 765         consumer_destroy_output(session->consumer);
 766         consumer_destroy_output(session->tmp_consumer);
 767
 768         free(session);
 769 }