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                         DBG("Error (%d) registering channel to sessiond", ret);
 242                         return ret;
 243                 }
 244         }
 245
 246         CMM_ACCESS_ONCE(session->active) = 1;
 247         CMM_ACCESS_ONCE(session->been_active) = 1;
 248 end:
 249         return ret;
 250 }
 251
 252 int lttng_session_disable(struct lttng_session *session)
 253 {
 254         int ret = 0;
 255
 256         if (!session->active) {
 257                 ret = -EBUSY;
 258                 goto end;
 259         }
 260         CMM_ACCESS_ONCE(session->active) = 0;
 261 end:
 262         return ret;
 263 }
 264
 265 int lttng_channel_enable(struct lttng_channel *channel)
 266 {
 267         int old;
 268
 269         if (channel == channel->session->metadata)
 270                 return -EPERM;
 271         old = uatomic_xchg(&channel->enabled, 1);
 272         if (old)
 273                 return -EEXIST;
 274         return 0;
 275 }
 276
 277 int lttng_channel_disable(struct lttng_channel *channel)
 278 {
 279         int old;
 280
 281         if (channel == channel->session->metadata)
 282                 return -EPERM;
 283         old = uatomic_xchg(&channel->enabled, 0);
 284         if (!old)
 285                 return -EEXIST;
 286         return 0;
 287 }
 288
 289 int lttng_event_enable(struct lttng_event *event)
 290 {
 291         int old;
 292
 293         if (event->chan == event->chan->session->metadata)
 294                 return -EPERM;
 295         old = uatomic_xchg(&event->enabled, 1);
 296         if (old)
 297                 return -EEXIST;
 298         return 0;
 299 }
 300
 301 int lttng_event_disable(struct lttng_event *event)
 302 {
 303         int old;
 304
 305         if (event->chan == event->chan->session->metadata)
 306                 return -EPERM;
 307         old = uatomic_xchg(&event->enabled, 0);
 308         if (!old)
 309                 return -EEXIST;
 310         return 0;
 311 }
 312
 313 /*
 314  * Supports event creation while tracing session is active.
 315  */
 316 static
 317 int lttng_event_create(const struct lttng_event_desc *desc,
 318                 struct lttng_channel *chan)
 319 {
 320         const char *event_name = desc->name;
 321         struct lttng_event *event;
 322         struct lttng_session *session = chan->session;
 323         struct cds_hlist_head *head;
 324         struct cds_hlist_node *node;
 325         int ret = 0;
 326         size_t name_len = strlen(event_name);
 327         uint32_t hash;
 328         int notify_socket, loglevel;
 329         const char *uri;
 330
 331         hash = jhash(event_name, name_len, 0);
 332         head = &chan->session->events_ht.table[hash & (LTTNG_UST_EVENT_HT_SIZE - 1)];
 333         cds_hlist_for_each_entry(event, node, head, hlist) {
 334                 assert(event->desc);
 335                 if (!strncmp(event->desc->name,
 336                                 desc->name,
 337                                 LTTNG_UST_SYM_NAME_LEN - 1)) {
 338                         ret = -EEXIST;
 339                         goto exist;
 340                 }
 341         }
 342
 343         notify_socket = lttng_get_notify_socket(session->owner);
 344         if (notify_socket < 0) {
 345                 ret = notify_socket;
 346                 goto socket_error;
 347         }
 348
 349         /*
 350          * Check if loglevel match. Refuse to connect event if not.
 351          */
 352         event = zmalloc(sizeof(struct lttng_event));
 353         if (!event) {
 354                 ret = -ENOMEM;
 355                 goto cache_error;
 356         }
 357         event->chan = chan;
 358
 359         event->enabled = 1;
 360         CDS_INIT_LIST_HEAD(&event->bytecode_runtime_head);
 361         CDS_INIT_LIST_HEAD(&event->enablers_ref_head);
 362         event->desc = desc;
 363
 364         if (desc->loglevel)
 365                 loglevel = *(*event->desc->loglevel);
 366         else
 367                 loglevel = TRACE_DEFAULT;
 368         if (desc->u.ext.model_emf_uri)
 369                 uri = *(desc->u.ext.model_emf_uri);
 370         else
 371                 uri = NULL;
 372
 373         /* Don't register metadata events */
 374         if (session->metadata == chan) {
 375                 event->id = -1U;
 376         } else {
 377                 /* Fetch event ID from sessiond */
 378                 ret = ustcomm_register_event(notify_socket,
 379                         session->objd,
 380                         chan->objd,
 381                         event_name,
 382                         loglevel,
 383                         desc->signature,
 384                         desc->nr_fields,
 385                         desc->fields,
 386                         uri,
 387                         &event->id);
 388                 if (ret < 0) {
 389                         DBG("Error (%d) registering event to sessiond", ret);
 390                         goto sessiond_register_error;
 391                 }
 392         }
 393
 394         /* Populate lttng_event structure before tracepoint registration. */
 395         cmm_smp_wmb();
 396         ret = __tracepoint_probe_register(event_name,
 397                         desc->probe_callback,
 398                         event, desc->signature);
 399         if (ret)
 400                 goto tracepoint_register_error;
 401
 402         cds_list_add(&event->node, &chan->session->events_head);
 403         cds_hlist_add_head(&event->hlist, head);
 404         return 0;
 405
 406 tracepoint_register_error:
 407 sessiond_register_error:
 408         free(event);
 409 cache_error:
 410 socket_error:
 411 exist:
 412         return ret;
 413 }
 414
 415 static
 416 int lttng_desc_match_wildcard_enabler(const struct lttng_event_desc *desc,
 417                 struct lttng_enabler *enabler)
 418 {
 419         int loglevel = 0;
 420         unsigned int has_loglevel;
 421
 422         assert(enabler->type == LTTNG_ENABLER_WILDCARD);
 423         /* Compare excluding final '*' */
 424         if (strncmp(desc->name, enabler->event_param.name,
 425                         strlen(enabler->event_param.name) - 1))
 426                 return 0;
 427         if (desc->loglevel) {
 428                 loglevel = *(*desc->loglevel);
 429                 has_loglevel = 1;
 430         }
 431         if (!lttng_loglevel_match(loglevel,
 432                         has_loglevel,
 433                         enabler->event_param.loglevel_type,
 434                         enabler->event_param.loglevel))
 435                 return 0;
 436         return 1;
 437 }
 438
 439 static
 440 int lttng_desc_match_event_enabler(const struct lttng_event_desc *desc,
 441                 struct lttng_enabler *enabler)
 442 {
 443         int loglevel = 0;
 444         unsigned int has_loglevel = 0;
 445
 446         assert(enabler->type == LTTNG_ENABLER_EVENT);
 447         if (strcmp(desc->name, enabler->event_param.name))
 448                 return 0;
 449         if (desc->loglevel) {
 450                 loglevel = *(*desc->loglevel);
 451                 has_loglevel = 1;
 452         }
 453         if (!lttng_loglevel_match(loglevel,
 454                         has_loglevel,
 455                         enabler->event_param.loglevel_type,
 456                         enabler->event_param.loglevel))
 457                 return 0;
 458         return 1;
 459 }
 460
 461 static
 462 int lttng_desc_match_enabler(const struct lttng_event_desc *desc,
 463                 struct lttng_enabler *enabler)
 464 {
 465         switch (enabler->type) {
 466         case LTTNG_ENABLER_WILDCARD:
 467                 return lttng_desc_match_wildcard_enabler(desc, enabler);
 468         case LTTNG_ENABLER_EVENT:
 469                 return lttng_desc_match_event_enabler(desc, enabler);
 470         default:
 471                 return -EINVAL;
 472         }
 473 }
 474
 475 static
 476 int lttng_event_match_enabler(struct lttng_event *event,
 477                 struct lttng_enabler *enabler)
 478 {
 479         return lttng_desc_match_enabler(event->desc, enabler);
 480 }
 481
 482 static
 483 struct lttng_enabler_ref * lttng_event_enabler_ref(struct lttng_event *event,
 484                 struct lttng_enabler *enabler)
 485 {
 486         struct lttng_enabler_ref *enabler_ref;
 487
 488         cds_list_for_each_entry(enabler_ref,
 489                         &event->enablers_ref_head, node) {
 490                 if (enabler_ref->ref == enabler)
 491                         return enabler_ref;
 492         }
 493         return NULL;
 494 }
 495
 496 /*
 497  * Create struct lttng_event if it is missing and present in the list of
 498  * tracepoint probes.
 499  */
 500 static
 501 void lttng_create_event_if_missing(struct lttng_enabler *enabler)
 502 {
 503         struct lttng_session *session = enabler->chan->session;
 504         struct lttng_probe_desc *probe_desc;
 505         const struct lttng_event_desc *desc;
 506         struct lttng_event *event;
 507         int i;
 508         struct cds_list_head *probe_list;
 509
 510         probe_list = lttng_get_probe_list_head();
 511         /*
 512          * For each probe event, if we find that a probe event matches
 513          * our enabler, create an associated lttng_event if not
 514          * already present.
 515          */
 516         cds_list_for_each_entry(probe_desc, probe_list, head) {
 517                 for (i = 0; i < probe_desc->nr_events; i++) {
 518                         int found = 0, ret;
 519                         struct cds_hlist_head *head;
 520                         struct cds_hlist_node *node;
 521                         const char *event_name;
 522                         size_t name_len;
 523                         uint32_t hash;
 524
 525                         desc = probe_desc->event_desc[i];
 526                         if (!lttng_desc_match_enabler(desc, enabler))
 527                                 continue;
 528                         event_name = desc->name;
 529                         name_len = strlen(event_name);
 530
 531                         /*
 532                          * Check if already created.
 533                          */
 534                         hash = jhash(event_name, name_len, 0);
 535                         head = &session->events_ht.table[hash & (LTTNG_UST_EVENT_HT_SIZE - 1)];
 536                         cds_hlist_for_each_entry(event, node, head, hlist) {
 537                                 if (event->desc == desc)
 538                                         found = 1;
 539                         }
 540                         if (found)
 541                                 continue;
 542
 543                         /*
 544                          * We need to create an event for this
 545                          * event probe.
 546                          */
 547                         ret = lttng_event_create(probe_desc->event_desc[i],
 548                                         enabler->chan);
 549                         if (ret) {
 550                                 DBG("Unable to create event %s, error %d\n",
 551                                         probe_desc->event_desc[i]->name, ret);
 552                         }
 553                 }
 554         }
 555 }
 556
 557 /*
 558  * Create events associated with an enabler (if not already present),
 559  * and add backward reference from the event to the enabler.
 560  */
 561 static
 562 int lttng_enabler_ref_events(struct lttng_enabler *enabler)
 563 {
 564         struct lttng_session *session = enabler->chan->session;
 565         struct lttng_event *event;
 566
 567         /* First ensure that probe events are created for this enabler. */
 568         lttng_create_event_if_missing(enabler);
 569
 570         /* For each event matching enabler in session event list. */
 571         cds_list_for_each_entry(event, &session->events_head, node) {
 572                 struct lttng_enabler_ref *enabler_ref;
 573
 574                 if (!lttng_event_match_enabler(event, enabler))
 575                         continue;
 576
 577                 enabler_ref = lttng_event_enabler_ref(event, enabler);
 578                 if (!enabler_ref) {
 579                         /*
 580                          * If no backward ref, create it.
 581                          * Add backward ref from event to enabler.
 582                          */
 583                         enabler_ref = zmalloc(sizeof(*enabler_ref));
 584                         if (!enabler_ref)
 585                                 return -ENOMEM;
 586                         enabler_ref->ref = enabler;
 587                         cds_list_add(&enabler_ref->node,
 588                                 &event->enablers_ref_head);
 589                 }
 590
 591                 /*
 592                  * Link filter bytecodes if not linked yet.
 593                  */
 594                 lttng_enabler_event_link_bytecode(event, enabler);
 595
 596                 /* TODO: merge event context. */
 597         }
 598         return 0;
 599 }
 600
 601 /*
 602  * Called at library load: connect the probe on all enablers matching
 603  * this event.
 604  * called with session mutex held.
 605  * TODO: currently, for each desc added, we iterate on all event desc
 606  * (inefficient). We should create specific code that only target the
 607  * added desc.
 608  */
 609 int lttng_fix_pending_event_desc(const struct lttng_event_desc *desc)
 610 {
 611         struct lttng_session *session;
 612
 613         cds_list_for_each_entry(session, &sessions, node) {
 614                 lttng_session_lazy_sync_enablers(session);
 615         }
 616         return 0;
 617 }
 618
 619 /*
 620  * Only used internally at session destruction.
 621  */
 622 int _lttng_event_unregister(struct lttng_event *event)
 623 {
 624         return __tracepoint_probe_unregister(event->desc->name,
 625                                           event->desc->probe_callback,
 626                                           event);
 627 }
 628
 629 /*
 630  * Only used internally at session destruction.
 631  */
 632 static
 633 void _lttng_event_destroy(struct lttng_event *event)
 634 {
 635         struct lttng_enabler_ref *enabler_ref, *tmp_enabler_ref;
 636
 637         cds_list_del(&event->node);
 638         lttng_destroy_context(event->ctx);
 639         lttng_free_event_filter_runtime(event);
 640         /* Free event enabler refs */
 641         cds_list_for_each_entry_safe(enabler_ref, tmp_enabler_ref,
 642                         &event->enablers_ref_head, node)
 643                 free(enabler_ref);
 644         free(event);
 645 }
 646
 647 void lttng_ust_events_exit(void)
 648 {
 649         struct lttng_session *session, *tmpsession;
 650
 651         cds_list_for_each_entry_safe(session, tmpsession, &sessions, node)
 652                 lttng_session_destroy(session);
 653 }
 654
 655 /*
 656  * Enabler management.
 657  */
 658 struct lttng_enabler *lttng_enabler_create(enum lttng_enabler_type type,
 659                 struct lttng_ust_event *event_param,
 660                 struct lttng_channel *chan)
 661 {
 662         struct lttng_enabler *enabler;
 663
 664         enabler = zmalloc(sizeof(*enabler));
 665         if (!enabler)
 666                 return NULL;
 667         enabler->type = type;
 668         CDS_INIT_LIST_HEAD(&enabler->filter_bytecode_head);
 669         memcpy(&enabler->event_param, event_param,
 670                 sizeof(enabler->event_param));
 671         enabler->chan = chan;
 672         /* ctx left NULL */
 673         enabler->enabled = 1;
 674         cds_list_add(&enabler->node, &enabler->chan->session->enablers_head);
 675         lttng_session_lazy_sync_enablers(enabler->chan->session);
 676         return enabler;
 677 }
 678
 679 int lttng_enabler_enable(struct lttng_enabler *enabler)
 680 {
 681         enabler->enabled = 1;
 682         lttng_session_lazy_sync_enablers(enabler->chan->session);
 683         return 0;
 684 }
 685
 686 int lttng_enabler_disable(struct lttng_enabler *enabler)
 687 {
 688         if (enabler->chan == enabler->chan->session->metadata)
 689                 return -EPERM;
 690         enabler->enabled = 0;
 691         lttng_session_lazy_sync_enablers(enabler->chan->session);
 692         return 0;
 693 }
 694
 695 int lttng_enabler_attach_bytecode(struct lttng_enabler *enabler,
 696                 struct lttng_ust_filter_bytecode_node *bytecode)
 697 {
 698         bytecode->enabler = enabler;
 699         cds_list_add_tail(&bytecode->node, &enabler->filter_bytecode_head);
 700         lttng_session_lazy_sync_enablers(enabler->chan->session);
 701         return 0;
 702 }
 703
 704 int lttng_attach_context(struct lttng_ust_context *context_param,
 705                 struct lttng_ctx **ctx, struct lttng_session *session)
 706 {
 707         /*
 708          * We cannot attach a context after trace has been started for a
 709          * session because the metadata does not allow expressing this
 710          * information outside of the original channel scope.
 711          */
 712         if (session->been_active)
 713                 return -EPERM;
 714
 715         switch (context_param->ctx) {
 716         case LTTNG_UST_CONTEXT_PTHREAD_ID:
 717                 return lttng_add_pthread_id_to_ctx(ctx);
 718         case LTTNG_UST_CONTEXT_VTID:
 719                 return lttng_add_vtid_to_ctx(ctx);
 720         case LTTNG_UST_CONTEXT_VPID:
 721                 return lttng_add_vpid_to_ctx(ctx);
 722         case LTTNG_UST_CONTEXT_PROCNAME:
 723                 return lttng_add_procname_to_ctx(ctx);
 724         default:
 725                 return -EINVAL;
 726         }
 727 }
 728
 729 int lttng_enabler_attach_context(struct lttng_enabler *enabler,
 730                 struct lttng_ust_context *context_param)
 731 {
 732 #if 0   // disabled for now.
 733         struct lttng_session *session = enabler->chan->session;
 734         int ret;
 735
 736         ret = lttng_attach_context(context_param, &enabler->ctx,
 737                         session);
 738         if (ret)
 739                 return ret;
 740         lttng_session_lazy_sync_enablers(enabler->chan->session);
 741 #endif
 742         return -ENOSYS;
 743 }
 744
 745 static
 746 void lttng_enabler_destroy(struct lttng_enabler *enabler)
 747 {
 748         struct lttng_ust_filter_bytecode_node *filter_node, *tmp_filter_node;
 749
 750         /* Destroy filter bytecode */
 751         cds_list_for_each_entry_safe(filter_node, tmp_filter_node,
 752                         &enabler->filter_bytecode_head, node) {
 753                 free(filter_node);
 754         }
 755
 756         /* Destroy contexts */
 757         lttng_destroy_context(enabler->ctx);
 758
 759         cds_list_del(&enabler->node);
 760         free(enabler);
 761 }
 762
 763 /*
 764  * lttng_session_sync_enablers should be called just before starting a
 765  * session.
 766  */
 767 static
 768 void lttng_session_sync_enablers(struct lttng_session *session)
 769 {
 770         struct lttng_enabler *enabler;
 771         struct lttng_event *event;
 772
 773         cds_list_for_each_entry(enabler, &session->enablers_head, node)
 774                 lttng_enabler_ref_events(enabler);
 775         /*
 776          * For each event, if at least one of its enablers is enabled,
 777          * we enable the event, else we disable it.
 778          */
 779         cds_list_for_each_entry(event, &session->events_head, node) {
 780                 struct lttng_enabler_ref *enabler_ref;
 781                 struct lttng_bytecode_runtime *runtime;
 782                 int enabled = 0, has_enablers_without_bytecode = 0;
 783
 784                 /* Enable events */
 785                 cds_list_for_each_entry(enabler_ref,
 786                                 &event->enablers_ref_head, node) {
 787                         if (enabler_ref->ref->enabled) {
 788                                 enabled = 1;
 789                                 break;
 790                         }
 791                 }
 792                 event->enabled = enabled;
 793
 794                 /* Check if has enablers without bytecode enabled */
 795                 cds_list_for_each_entry(enabler_ref,
 796                                 &event->enablers_ref_head, node) {
 797                         if (enabler_ref->ref->enabled
 798                                         && cds_list_empty(&enabler_ref->ref->filter_bytecode_head)) {
 799                                 has_enablers_without_bytecode = 1;
 800                                 break;
 801                         }
 802                 }
 803                 event->has_enablers_without_bytecode =
 804                         has_enablers_without_bytecode;
 805
 806                 /* Enable filters */
 807                 cds_list_for_each_entry(runtime,
 808                                 &event->bytecode_runtime_head, node) {
 809                         lttng_filter_sync_state(runtime);
 810                 }
 811         }
 812 }
 813
 814 /*
 815  * Apply enablers to session events, adding events to session if need
 816  * be. It is required after each modification applied to an active
 817  * session, and right before session "start".
 818  * "lazy" sync means we only sync if required.
 819  */
 820 static
 821 void lttng_session_lazy_sync_enablers(struct lttng_session *session)
 822 {
 823         /* We can skip if session is not active */
 824         if (!session->active)
 825                 return;
 826         lttng_session_sync_enablers(session);
 827 }