liblttng-ust/lttng-events.c

   1 /*
   2  * lttng-events.c
   3  *
   4  * Holds LTTng per-session event registry.
   5  *
   6  * Copyright (C) 2010-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   7  *
   8  * This library is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU Lesser General Public
  10  * License as published by the Free Software Foundation; only
  11  * version 2.1 of the License.
  12  *
  13  * This library is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  16  * Lesser General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU Lesser General Public
  19  * License along with this library; if not, write to the Free Software
  20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  21  */
  22
  23 #define _GNU_SOURCE
  24 #include <stdio.h>
  25 #include <urcu/list.h>
  26 #include <urcu/hlist.h>
  27 #include <pthread.h>
  28 #include <errno.h>
  29 #include <sys/shm.h>
  30 #include <sys/ipc.h>
  31 #include <stdint.h>
  32 #include <stddef.h>
  33 #include <inttypes.h>
  34 #include <time.h>
  35 #include <lttng/ust-endian.h>
  36 #include "clock.h"
  37
  38 #include <urcu-bp.h>
  39 #include <urcu/compiler.h>
  40 #include <urcu/uatomic.h>
  41 #include <urcu/arch.h>
  42
  43 #include <lttng/tracepoint.h>
  44 #include <lttng/ust-events.h>
  45
  46 #include <usterr-signal-safe.h>
  47 #include <helper.h>
  48 #include <ust-ctl.h>
  49 #include <ust-comm.h>
  50 #include "error.h"
  51 #include "compat.h"
  52 #include "lttng-ust-uuid.h"
  53
  54 #include "tracepoint-internal.h"
  55 #include "lttng-tracer.h"
  56 #include "lttng-tracer-core.h"
  57 #include "wait.h"
  58 #include "../libringbuffer/shm.h"
  59 #include "jhash.h"
  60
  61 /*
  62  * The sessions mutex is the centralized mutex across UST tracing
  63  * control and probe registration. All operations within this file are
  64  * called by the communication thread, under ust_lock protection.
  65  */
  66 static pthread_mutex_t sessions_mutex = PTHREAD_MUTEX_INITIALIZER;
  67
  68 void ust_lock(void)
  69 {
  70         pthread_mutex_lock(&sessions_mutex);
  71 }
  72
  73 void ust_unlock(void)
  74 {
  75         pthread_mutex_unlock(&sessions_mutex);
  76 }
  77
  78 static CDS_LIST_HEAD(sessions);
  79
  80 static void _lttng_event_destroy(struct lttng_event *event);
  81
  82 static
  83 void lttng_session_lazy_sync_enablers(struct lttng_session *session);
  84 static
  85 void lttng_session_sync_enablers(struct lttng_session *session);
  86 static
  87 void lttng_enabler_destroy(struct lttng_enabler *enabler);
  88
  89 /*
  90  * Called with ust lock held.
  91  */
  92 int lttng_session_active(void)
  93 {
  94         struct lttng_session *iter;
  95
  96         cds_list_for_each_entry(iter, &sessions, node) {
  97                 if (iter->active)
  98                         return 1;
  99         }
 100         return 0;
 101 }
 102
 103 static
 104 int lttng_loglevel_match(int loglevel,
 105                 unsigned int has_loglevel,
 106                 enum lttng_ust_loglevel_type req_type,
 107                 int req_loglevel)
 108 {
 109         if (req_type == LTTNG_UST_LOGLEVEL_ALL)
 110                 return 1;
 111         if (!has_loglevel)
 112                 loglevel = TRACE_DEFAULT;
 113         switch (req_type) {
 114         case LTTNG_UST_LOGLEVEL_RANGE:
 115                 if (loglevel <= req_loglevel || req_loglevel == -1)
 116                         return 1;
 117                 else
 118                         return 0;
 119         case LTTNG_UST_LOGLEVEL_SINGLE:
 120                 if (loglevel == req_loglevel || req_loglevel == -1)
 121                         return 1;
 122                 else
 123                         return 0;
 124         case LTTNG_UST_LOGLEVEL_ALL:
 125         default:
 126                 return 1;
 127         }
 128 }
 129
 130 void synchronize_trace(void)
 131 {
 132         synchronize_rcu();
 133 }
 134
 135 struct lttng_session *lttng_session_create(void)
 136 {
 137         struct lttng_session *session;
 138         int i;
 139
 140         session = zmalloc(sizeof(struct lttng_session));
 141         if (!session)
 142                 return NULL;
 143         CDS_INIT_LIST_HEAD(&session->chan_head);
 144         CDS_INIT_LIST_HEAD(&session->events_head);
 145         CDS_INIT_LIST_HEAD(&session->enablers_head);
 146         for (i = 0; i < LTTNG_UST_EVENT_HT_SIZE; i++)
 147                 CDS_INIT_HLIST_HEAD(&session->events_ht.table[i]);
 148         cds_list_add(&session->node, &sessions);
 149         return session;
 150 }
 151
 152 /*
 153  * Only used internally at session destruction.
 154  */
 155 static
 156 void _lttng_channel_unmap(struct lttng_channel *lttng_chan)
 157 {
 158         struct channel *chan;
 159         struct lttng_ust_shm_handle *handle;
 160
 161         cds_list_del(&lttng_chan->node);
 162         lttng_destroy_context(lttng_chan->ctx);
 163         chan = lttng_chan->chan;
 164         handle = lttng_chan->handle;
 165         /*
 166          * note: lttng_chan is private data contained within handle. It
 167          * will be freed along with the handle.
 168          */
 169         channel_destroy(chan, handle, 0);
 170 }
 171
 172 static
 173 void register_event(struct lttng_event *event)
 174 {
 175         int ret;
 176         const struct lttng_event_desc *desc;
 177
 178         assert(event->registered == 0);
 179         desc = event->desc;
 180         ret = __tracepoint_probe_register(desc->name,
 181                         desc->probe_callback,
 182                         event, desc->signature);
 183         WARN_ON_ONCE(ret);
 184         if (!ret)
 185                 event->registered = 1;
 186 }
 187
 188 static
 189 void unregister_event(struct lttng_event *event)
 190 {
 191         int ret;
 192         const struct lttng_event_desc *desc;
 193
 194         assert(event->registered == 1);
 195         desc = event->desc;
 196         ret = __tracepoint_probe_unregister(desc->name,
 197                         desc->probe_callback,
 198                         event);
 199         WARN_ON_ONCE(ret);
 200         if (!ret)
 201                 event->registered = 0;
 202 }
 203
 204 /*
 205  * Only used internally at session destruction.
 206  */
 207 static
 208 void _lttng_event_unregister(struct lttng_event *event)
 209 {
 210         if (event->registered)
 211                 unregister_event(event);
 212 }
 213
 214 void lttng_session_destroy(struct lttng_session *session)
 215 {
 216         struct lttng_channel *chan, *tmpchan;
 217         struct lttng_event *event, *tmpevent;
 218         struct lttng_enabler *enabler, *tmpenabler;
 219
 220         CMM_ACCESS_ONCE(session->active) = 0;
 221         cds_list_for_each_entry(event, &session->events_head, node) {
 222                 _lttng_event_unregister(event);
 223         }
 224         synchronize_trace();    /* Wait for in-flight events to complete */
 225         cds_list_for_each_entry_safe(enabler, tmpenabler,
 226                         &session->enablers_head, node)
 227                 lttng_enabler_destroy(enabler);
 228         cds_list_for_each_entry_safe(event, tmpevent,
 229                         &session->events_head, node)
 230                 _lttng_event_destroy(event);
 231         cds_list_for_each_entry_safe(chan, tmpchan, &session->chan_head, node)
 232                 _lttng_channel_unmap(chan);
 233         cds_list_del(&session->node);
 234         free(session);
 235 }
 236
 237 int lttng_session_enable(struct lttng_session *session)
 238 {
 239         int ret = 0;
 240         struct lttng_channel *chan;
 241         int notify_socket;
 242
 243         if (session->active) {
 244                 ret = -EBUSY;
 245                 goto end;
 246         }
 247
 248         notify_socket = lttng_get_notify_socket(session->owner);
 249         if (notify_socket < 0)
 250                 return notify_socket;
 251
 252         /* Set transient enabler state to "enabled" */
 253         session->tstate = 1;
 254         /* We need to sync enablers with session before activation. */
 255         lttng_session_sync_enablers(session);
 256
 257         /*
 258          * Snapshot the number of events per channel to know the type of header
 259          * we need to use.
 260          */
 261         cds_list_for_each_entry(chan, &session->chan_head, node) {
 262                 const struct lttng_ctx *ctx;
 263                 const struct lttng_event_field *fields = NULL;
 264                 size_t nr_fields = 0;
 265
 266                 /* don't change it if session stop/restart */
 267                 if (chan->header_type)
 268                         continue;
 269                 ctx = chan->ctx;
 270                 if (ctx) {
 271                         nr_fields = ctx->nr_fields;
 272                         fields = &ctx->fields->event_field;
 273                 }
 274                 ret = ustcomm_register_channel(notify_socket,
 275                         session->objd,
 276                         chan->objd,
 277                         nr_fields,
 278                         fields,
 279                         &chan->id,
 280                         &chan->header_type);
 281                 if (ret) {
 282                         DBG("Error (%d) registering channel to sessiond", ret);
 283                         return ret;
 284                 }
 285         }
 286
 287         /* Set atomically the state to "active" */
 288         CMM_ACCESS_ONCE(session->active) = 1;
 289         CMM_ACCESS_ONCE(session->been_active) = 1;
 290 end:
 291         return ret;
 292 }
 293
 294 int lttng_session_disable(struct lttng_session *session)
 295 {
 296         int ret = 0;
 297
 298         if (!session->active) {
 299                 ret = -EBUSY;
 300                 goto end;
 301         }
 302         /* Set atomically the state to "inactive" */
 303         CMM_ACCESS_ONCE(session->active) = 0;
 304
 305         /* Set transient enabler state to "disabled" */
 306         session->tstate = 0;
 307         lttng_session_sync_enablers(session);
 308 end:
 309         return ret;
 310 }
 311
 312 int lttng_channel_enable(struct lttng_channel *channel)
 313 {
 314         int ret = 0;
 315
 316         if (channel->enabled) {
 317                 ret = -EBUSY;
 318                 goto end;
 319         }
 320         /* Set transient enabler state to "enabled" */
 321         channel->tstate = 1;
 322         lttng_session_sync_enablers(channel->session);
 323         /* Set atomically the state to "enabled" */
 324         CMM_ACCESS_ONCE(channel->enabled) = 1;
 325 end:
 326         return ret;
 327 }
 328
 329 int lttng_channel_disable(struct lttng_channel *channel)
 330 {
 331         int ret = 0;
 332
 333         if (!channel->enabled) {
 334                 ret = -EBUSY;
 335                 goto end;
 336         }
 337         /* Set atomically the state to "disabled" */
 338         CMM_ACCESS_ONCE(channel->enabled) = 0;
 339         /* Set transient enabler state to "enabled" */
 340         channel->tstate = 0;
 341         lttng_session_sync_enablers(channel->session);
 342 end:
 343         return ret;
 344 }
 345
 346 /*
 347  * Supports event creation while tracing session is active.
 348  */
 349 static
 350 int lttng_event_create(const struct lttng_event_desc *desc,
 351                 struct lttng_channel *chan)
 352 {
 353         const char *event_name = desc->name;
 354         struct lttng_event *event;
 355         struct lttng_session *session = chan->session;
 356         struct cds_hlist_head *head;
 357         struct cds_hlist_node *node;
 358         int ret = 0;
 359         size_t name_len = strlen(event_name);
 360         uint32_t hash;
 361         int notify_socket, loglevel;
 362         const char *uri;
 363
 364         hash = jhash(event_name, name_len, 0);
 365         head = &chan->session->events_ht.table[hash & (LTTNG_UST_EVENT_HT_SIZE - 1)];
 366         cds_hlist_for_each_entry(event, node, head, hlist) {
 367                 assert(event->desc);
 368                 if (!strncmp(event->desc->name,
 369                                 desc->name,
 370                                 LTTNG_UST_SYM_NAME_LEN - 1)) {
 371                         ret = -EEXIST;
 372                         goto exist;
 373                 }
 374         }
 375
 376         notify_socket = lttng_get_notify_socket(session->owner);
 377         if (notify_socket < 0) {
 378                 ret = notify_socket;
 379                 goto socket_error;
 380         }
 381
 382         /*
 383          * Check if loglevel match. Refuse to connect event if not.
 384          */
 385         event = zmalloc(sizeof(struct lttng_event));
 386         if (!event) {
 387                 ret = -ENOMEM;
 388                 goto cache_error;
 389         }
 390         event->chan = chan;
 391
 392         /* Event will be enabled by enabler sync. */
 393         event->enabled = 0;
 394         event->registered = 0;
 395         CDS_INIT_LIST_HEAD(&event->bytecode_runtime_head);
 396         CDS_INIT_LIST_HEAD(&event->enablers_ref_head);
 397         event->desc = desc;
 398
 399         if (desc->loglevel)
 400                 loglevel = *(*event->desc->loglevel);
 401         else
 402                 loglevel = TRACE_DEFAULT;
 403         if (desc->u.ext.model_emf_uri)
 404                 uri = *(desc->u.ext.model_emf_uri);
 405         else
 406                 uri = NULL;
 407
 408         /* Fetch event ID from sessiond */
 409         ret = ustcomm_register_event(notify_socket,
 410                 session->objd,
 411                 chan->objd,
 412                 event_name,
 413                 loglevel,
 414                 desc->signature,
 415                 desc->nr_fields,
 416                 desc->fields,
 417                 uri,
 418                 &event->id);
 419         if (ret < 0) {
 420                 DBG("Error (%d) registering event to sessiond", ret);
 421                 goto sessiond_register_error;
 422         }
 423
 424         /* Populate lttng_event structure before tracepoint registration. */
 425         cmm_smp_wmb();
 426         cds_list_add(&event->node, &chan->session->events_head);
 427         cds_hlist_add_head(&event->hlist, head);
 428         return 0;
 429
 430 sessiond_register_error:
 431         free(event);
 432 cache_error:
 433 socket_error:
 434 exist:
 435         return ret;
 436 }
 437
 438 static
 439 int lttng_desc_match_wildcard_enabler(const struct lttng_event_desc *desc,
 440                 struct lttng_enabler *enabler)
 441 {
 442         int loglevel = 0;
 443         unsigned int has_loglevel = 0;
 444
 445         assert(enabler->type == LTTNG_ENABLER_WILDCARD);
 446         /* Compare excluding final '*' */
 447         if (strncmp(desc->name, enabler->event_param.name,
 448                         strlen(enabler->event_param.name) - 1))
 449                 return 0;
 450         if (desc->loglevel) {
 451                 loglevel = *(*desc->loglevel);
 452                 has_loglevel = 1;
 453         }
 454         if (!lttng_loglevel_match(loglevel,
 455                         has_loglevel,
 456                         enabler->event_param.loglevel_type,
 457                         enabler->event_param.loglevel))
 458                 return 0;
 459         return 1;
 460 }
 461
 462 static
 463 int lttng_desc_match_event_enabler(const struct lttng_event_desc *desc,
 464                 struct lttng_enabler *enabler)
 465 {
 466         int loglevel = 0;
 467         unsigned int has_loglevel = 0;
 468
 469         assert(enabler->type == LTTNG_ENABLER_EVENT);
 470         if (strcmp(desc->name, enabler->event_param.name))
 471                 return 0;
 472         if (desc->loglevel) {
 473                 loglevel = *(*desc->loglevel);
 474                 has_loglevel = 1;
 475         }
 476         if (!lttng_loglevel_match(loglevel,
 477                         has_loglevel,
 478                         enabler->event_param.loglevel_type,
 479                         enabler->event_param.loglevel))
 480                 return 0;
 481         return 1;
 482 }
 483
 484 static
 485 int lttng_desc_match_enabler(const struct lttng_event_desc *desc,
 486                 struct lttng_enabler *enabler)
 487 {
 488         switch (enabler->type) {
 489         case LTTNG_ENABLER_WILDCARD:
 490                 return lttng_desc_match_wildcard_enabler(desc, enabler);
 491         case LTTNG_ENABLER_EVENT:
 492                 return lttng_desc_match_event_enabler(desc, enabler);
 493         default:
 494                 return -EINVAL;
 495         }
 496 }
 497
 498 static
 499 int lttng_event_match_enabler(struct lttng_event *event,
 500                 struct lttng_enabler *enabler)
 501 {
 502         return lttng_desc_match_enabler(event->desc, enabler);
 503 }
 504
 505 static
 506 struct lttng_enabler_ref * lttng_event_enabler_ref(struct lttng_event *event,
 507                 struct lttng_enabler *enabler)
 508 {
 509         struct lttng_enabler_ref *enabler_ref;
 510
 511         cds_list_for_each_entry(enabler_ref,
 512                         &event->enablers_ref_head, node) {
 513                 if (enabler_ref->ref == enabler)
 514                         return enabler_ref;
 515         }
 516         return NULL;
 517 }
 518
 519 /*
 520  * Create struct lttng_event if it is missing and present in the list of
 521  * tracepoint probes.
 522  */
 523 static
 524 void lttng_create_event_if_missing(struct lttng_enabler *enabler)
 525 {
 526         struct lttng_session *session = enabler->chan->session;
 527         struct lttng_probe_desc *probe_desc;
 528         const struct lttng_event_desc *desc;
 529         struct lttng_event *event;
 530         int i;
 531         struct cds_list_head *probe_list;
 532
 533         probe_list = lttng_get_probe_list_head();
 534         /*
 535          * For each probe event, if we find that a probe event matches
 536          * our enabler, create an associated lttng_event if not
 537          * already present.
 538          */
 539         cds_list_for_each_entry(probe_desc, probe_list, head) {
 540                 for (i = 0; i < probe_desc->nr_events; i++) {
 541                         int found = 0, ret;
 542                         struct cds_hlist_head *head;
 543                         struct cds_hlist_node *node;
 544                         const char *event_name;
 545                         size_t name_len;
 546                         uint32_t hash;
 547
 548                         desc = probe_desc->event_desc[i];
 549                         if (!lttng_desc_match_enabler(desc, enabler))
 550                                 continue;
 551                         event_name = desc->name;
 552                         name_len = strlen(event_name);
 553
 554                         /*
 555                          * Check if already created.
 556                          */
 557                         hash = jhash(event_name, name_len, 0);
 558                         head = &session->events_ht.table[hash & (LTTNG_UST_EVENT_HT_SIZE - 1)];
 559                         cds_hlist_for_each_entry(event, node, head, hlist) {
 560                                 if (event->desc == desc)
 561                                         found = 1;
 562                         }
 563                         if (found)
 564                                 continue;
 565
 566                         /*
 567                          * We need to create an event for this
 568                          * event probe.
 569                          */
 570                         ret = lttng_event_create(probe_desc->event_desc[i],
 571                                         enabler->chan);
 572                         if (ret) {
 573                                 DBG("Unable to create event %s, error %d\n",
 574                                         probe_desc->event_desc[i]->name, ret);
 575                         }
 576                 }
 577         }
 578 }
 579
 580 /*
 581  * Create events associated with an enabler (if not already present),
 582  * and add backward reference from the event to the enabler.
 583  */
 584 static
 585 int lttng_enabler_ref_events(struct lttng_enabler *enabler)
 586 {
 587         struct lttng_session *session = enabler->chan->session;
 588         struct lttng_event *event;
 589
 590         /* First ensure that probe events are created for this enabler. */
 591         lttng_create_event_if_missing(enabler);
 592
 593         /* For each event matching enabler in session event list. */
 594         cds_list_for_each_entry(event, &session->events_head, node) {
 595                 struct lttng_enabler_ref *enabler_ref;
 596
 597                 if (!lttng_event_match_enabler(event, enabler))
 598                         continue;
 599
 600                 enabler_ref = lttng_event_enabler_ref(event, enabler);
 601                 if (!enabler_ref) {
 602                         /*
 603                          * If no backward ref, create it.
 604                          * Add backward ref from event to enabler.
 605                          */
 606                         enabler_ref = zmalloc(sizeof(*enabler_ref));
 607                         if (!enabler_ref)
 608                                 return -ENOMEM;
 609                         enabler_ref->ref = enabler;
 610                         cds_list_add(&enabler_ref->node,
 611                                 &event->enablers_ref_head);
 612                 }
 613
 614                 /*
 615                  * Link filter bytecodes if not linked yet.
 616                  */
 617                 lttng_enabler_event_link_bytecode(event, enabler);
 618
 619                 /* TODO: merge event context. */
 620         }
 621         return 0;
 622 }
 623
 624 /*
 625  * Called at library load: connect the probe on all enablers matching
 626  * this event.
 627  * called with session mutex held.
 628  * TODO: currently, for each desc added, we iterate on all event desc
 629  * (inefficient). We should create specific code that only target the
 630  * added desc.
 631  */
 632 int lttng_fix_pending_event_desc(const struct lttng_event_desc *desc)
 633 {
 634         struct lttng_session *session;
 635
 636         cds_list_for_each_entry(session, &sessions, node) {
 637                 lttng_session_lazy_sync_enablers(session);
 638         }
 639         return 0;
 640 }
 641
 642 /*
 643  * Only used internally at session destruction.
 644  */
 645 static
 646 void _lttng_event_destroy(struct lttng_event *event)
 647 {
 648         struct lttng_enabler_ref *enabler_ref, *tmp_enabler_ref;
 649
 650         cds_list_del(&event->node);
 651         lttng_destroy_context(event->ctx);
 652         lttng_free_event_filter_runtime(event);
 653         /* Free event enabler refs */
 654         cds_list_for_each_entry_safe(enabler_ref, tmp_enabler_ref,
 655                         &event->enablers_ref_head, node)
 656                 free(enabler_ref);
 657         free(event);
 658 }
 659
 660 void lttng_ust_events_exit(void)
 661 {
 662         struct lttng_session *session, *tmpsession;
 663
 664         cds_list_for_each_entry_safe(session, tmpsession, &sessions, node)
 665                 lttng_session_destroy(session);
 666 }
 667
 668 /*
 669  * Enabler management.
 670  */
 671 struct lttng_enabler *lttng_enabler_create(enum lttng_enabler_type type,
 672                 struct lttng_ust_event *event_param,
 673                 struct lttng_channel *chan)
 674 {
 675         struct lttng_enabler *enabler;
 676
 677         enabler = zmalloc(sizeof(*enabler));
 678         if (!enabler)
 679                 return NULL;
 680         enabler->type = type;
 681         CDS_INIT_LIST_HEAD(&enabler->filter_bytecode_head);
 682         memcpy(&enabler->event_param, event_param,
 683                 sizeof(enabler->event_param));
 684         enabler->chan = chan;
 685         /* ctx left NULL */
 686         enabler->enabled = 1;
 687         cds_list_add(&enabler->node, &enabler->chan->session->enablers_head);
 688         lttng_session_lazy_sync_enablers(enabler->chan->session);
 689         return enabler;
 690 }
 691
 692 int lttng_enabler_enable(struct lttng_enabler *enabler)
 693 {
 694         enabler->enabled = 1;
 695         lttng_session_lazy_sync_enablers(enabler->chan->session);
 696         return 0;
 697 }
 698
 699 int lttng_enabler_disable(struct lttng_enabler *enabler)
 700 {
 701         enabler->enabled = 0;
 702         lttng_session_lazy_sync_enablers(enabler->chan->session);
 703         return 0;
 704 }
 705
 706 int lttng_enabler_attach_bytecode(struct lttng_enabler *enabler,
 707                 struct lttng_ust_filter_bytecode_node *bytecode)
 708 {
 709         bytecode->enabler = enabler;
 710         cds_list_add_tail(&bytecode->node, &enabler->filter_bytecode_head);
 711         lttng_session_lazy_sync_enablers(enabler->chan->session);
 712         return 0;
 713 }
 714
 715 int lttng_attach_context(struct lttng_ust_context *context_param,
 716                 struct lttng_ctx **ctx, struct lttng_session *session)
 717 {
 718         /*
 719          * We cannot attach a context after trace has been started for a
 720          * session because the metadata does not allow expressing this
 721          * information outside of the original channel scope.
 722          */
 723         if (session->been_active)
 724                 return -EPERM;
 725
 726         switch (context_param->ctx) {
 727         case LTTNG_UST_CONTEXT_PTHREAD_ID:
 728                 return lttng_add_pthread_id_to_ctx(ctx);
 729         case LTTNG_UST_CONTEXT_VTID:
 730                 return lttng_add_vtid_to_ctx(ctx);
 731         case LTTNG_UST_CONTEXT_VPID:
 732                 return lttng_add_vpid_to_ctx(ctx);
 733         case LTTNG_UST_CONTEXT_PROCNAME:
 734                 return lttng_add_procname_to_ctx(ctx);
 735         default:
 736                 return -EINVAL;
 737         }
 738 }
 739
 740 int lttng_enabler_attach_context(struct lttng_enabler *enabler,
 741                 struct lttng_ust_context *context_param)
 742 {
 743 #if 0   // disabled for now.
 744         struct lttng_session *session = enabler->chan->session;
 745         int ret;
 746
 747         ret = lttng_attach_context(context_param, &enabler->ctx,
 748                         session);
 749         if (ret)
 750                 return ret;
 751         lttng_session_lazy_sync_enablers(enabler->chan->session);
 752 #endif
 753         return -ENOSYS;
 754 }
 755
 756 static
 757 void lttng_enabler_destroy(struct lttng_enabler *enabler)
 758 {
 759         struct lttng_ust_filter_bytecode_node *filter_node, *tmp_filter_node;
 760
 761         /* Destroy filter bytecode */
 762         cds_list_for_each_entry_safe(filter_node, tmp_filter_node,
 763                         &enabler->filter_bytecode_head, node) {
 764                 free(filter_node);
 765         }
 766
 767         /* Destroy contexts */
 768         lttng_destroy_context(enabler->ctx);
 769
 770         cds_list_del(&enabler->node);
 771         free(enabler);
 772 }
 773
 774 /*
 775  * lttng_session_sync_enablers should be called just before starting a
 776  * session.
 777  */
 778 static
 779 void lttng_session_sync_enablers(struct lttng_session *session)
 780 {
 781         struct lttng_enabler *enabler;
 782         struct lttng_event *event;
 783
 784         cds_list_for_each_entry(enabler, &session->enablers_head, node)
 785                 lttng_enabler_ref_events(enabler);
 786         /*
 787          * For each event, if at least one of its enablers is enabled,
 788          * and its channel and session transient states are enabled, we
 789          * enable the event, else we disable it.
 790          */
 791         cds_list_for_each_entry(event, &session->events_head, node) {
 792                 struct lttng_enabler_ref *enabler_ref;
 793                 struct lttng_bytecode_runtime *runtime;
 794                 int enabled = 0, has_enablers_without_bytecode = 0;
 795
 796                 /* Enable events */
 797                 cds_list_for_each_entry(enabler_ref,
 798                                 &event->enablers_ref_head, node) {
 799                         if (enabler_ref->ref->enabled) {
 800                                 enabled = 1;
 801                                 break;
 802                         }
 803                 }
 804                 /*
 805                  * Enabled state is based on union of enablers, with
 806                  * intesection of session and channel transient enable
 807                  * states.
 808                  */
 809                 enabled = enabled && session->tstate && event->chan->tstate;
 810
 811                 CMM_STORE_SHARED(event->enabled, enabled);
 812                 /*
 813                  * Sync tracepoint registration with event enabled
 814                  * state.
 815                  */
 816                 if (enabled) {
 817                         if (!event->registered)
 818                                 register_event(event);
 819                 } else {
 820                         if (event->registered)
 821                                 unregister_event(event);
 822                 }
 823
 824                 /* Check if has enablers without bytecode enabled */
 825                 cds_list_for_each_entry(enabler_ref,
 826                                 &event->enablers_ref_head, node) {
 827                         if (enabler_ref->ref->enabled
 828                                         && cds_list_empty(&enabler_ref->ref->filter_bytecode_head)) {
 829                                 has_enablers_without_bytecode = 1;
 830                                 break;
 831                         }
 832                 }
 833                 event->has_enablers_without_bytecode =
 834                         has_enablers_without_bytecode;
 835
 836                 /* Enable filters */
 837                 cds_list_for_each_entry(runtime,
 838                                 &event->bytecode_runtime_head, node) {
 839                         lttng_filter_sync_state(runtime);
 840                 }
 841         }
 842 }
 843
 844 /*
 845  * Apply enablers to session events, adding events to session if need
 846  * be. It is required after each modification applied to an active
 847  * session, and right before session "start".
 848  * "lazy" sync means we only sync if required.
 849  */
 850 static
 851 void lttng_session_lazy_sync_enablers(struct lttng_session *session)
 852 {
 853         /* We can skip if session is not active */
 854         if (!session->active)
 855                 return;
 856         lttng_session_sync_enablers(session);
 857 }