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