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