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                 uint32_t chan_id;
 266
 267                 /* don't change it if session stop/restart */
 268                 if (chan->header_type)
 269                         continue;
 270                 ctx = chan->ctx;
 271                 if (ctx) {
 272                         nr_fields = ctx->nr_fields;
 273                         fields = &ctx->fields->event_field;
 274                 }
 275                 ret = ustcomm_register_channel(notify_socket,
 276                         session->objd,
 277                         chan->objd,
 278                         nr_fields,
 279                         fields,
 280                         &chan_id,
 281                         &chan->header_type);
 282                 if (ret) {
 283                         DBG("Error (%d) registering channel to sessiond", ret);
 284                         return ret;
 285                 }
 286                 if (chan_id != chan->id) {
 287                         DBG("Error: channel registration id (%u) does not match id assigned at creation (%u)",
 288                                 chan_id, chan->id);
 289                         return -EINVAL;
 290                 }
 291         }
 292
 293         /* Set atomically the state to "active" */
 294         CMM_ACCESS_ONCE(session->active) = 1;
 295         CMM_ACCESS_ONCE(session->been_active) = 1;
 296 end:
 297         return ret;
 298 }
 299
 300 int lttng_session_disable(struct lttng_session *session)
 301 {
 302         int ret = 0;
 303
 304         if (!session->active) {
 305                 ret = -EBUSY;
 306                 goto end;
 307         }
 308         /* Set atomically the state to "inactive" */
 309         CMM_ACCESS_ONCE(session->active) = 0;
 310
 311         /* Set transient enabler state to "disabled" */
 312         session->tstate = 0;
 313         lttng_session_sync_enablers(session);
 314 end:
 315         return ret;
 316 }
 317
 318 int lttng_channel_enable(struct lttng_channel *channel)
 319 {
 320         int ret = 0;
 321
 322         if (channel->enabled) {
 323                 ret = -EBUSY;
 324                 goto end;
 325         }
 326         /* Set transient enabler state to "enabled" */
 327         channel->tstate = 1;
 328         lttng_session_sync_enablers(channel->session);
 329         /* Set atomically the state to "enabled" */
 330         CMM_ACCESS_ONCE(channel->enabled) = 1;
 331 end:
 332         return ret;
 333 }
 334
 335 int lttng_channel_disable(struct lttng_channel *channel)
 336 {
 337         int ret = 0;
 338
 339         if (!channel->enabled) {
 340                 ret = -EBUSY;
 341                 goto end;
 342         }
 343         /* Set atomically the state to "disabled" */
 344         CMM_ACCESS_ONCE(channel->enabled) = 0;
 345         /* Set transient enabler state to "enabled" */
 346         channel->tstate = 0;
 347         lttng_session_sync_enablers(channel->session);
 348 end:
 349         return ret;
 350 }
 351
 352 /*
 353  * Supports event creation while tracing session is active.
 354  */
 355 static
 356 int lttng_event_create(const struct lttng_event_desc *desc,
 357                 struct lttng_channel *chan)
 358 {
 359         const char *event_name = desc->name;
 360         struct lttng_event *event;
 361         struct lttng_session *session = chan->session;
 362         struct cds_hlist_head *head;
 363         struct cds_hlist_node *node;
 364         int ret = 0;
 365         size_t name_len = strlen(event_name);
 366         uint32_t hash;
 367         int notify_socket, loglevel;
 368         const char *uri;
 369
 370         hash = jhash(event_name, name_len, 0);
 371         head = &chan->session->events_ht.table[hash & (LTTNG_UST_EVENT_HT_SIZE - 1)];
 372         cds_hlist_for_each_entry(event, node, head, hlist) {
 373                 assert(event->desc);
 374                 if (!strncmp(event->desc->name,
 375                                 desc->name,
 376                                 LTTNG_UST_SYM_NAME_LEN - 1)) {
 377                         ret = -EEXIST;
 378                         goto exist;
 379                 }
 380         }
 381
 382         notify_socket = lttng_get_notify_socket(session->owner);
 383         if (notify_socket < 0) {
 384                 ret = notify_socket;
 385                 goto socket_error;
 386         }
 387
 388         /*
 389          * Check if loglevel match. Refuse to connect event if not.
 390          */
 391         event = zmalloc(sizeof(struct lttng_event));
 392         if (!event) {
 393                 ret = -ENOMEM;
 394                 goto cache_error;
 395         }
 396         event->chan = chan;
 397
 398         /* Event will be enabled by enabler sync. */
 399         event->enabled = 0;
 400         event->registered = 0;
 401         CDS_INIT_LIST_HEAD(&event->bytecode_runtime_head);
 402         CDS_INIT_LIST_HEAD(&event->enablers_ref_head);
 403         event->desc = desc;
 404
 405         if (desc->loglevel)
 406                 loglevel = *(*event->desc->loglevel);
 407         else
 408                 loglevel = TRACE_DEFAULT;
 409         if (desc->u.ext.model_emf_uri)
 410                 uri = *(desc->u.ext.model_emf_uri);
 411         else
 412                 uri = NULL;
 413
 414         /* Fetch event ID from sessiond */
 415         ret = ustcomm_register_event(notify_socket,
 416                 session->objd,
 417                 chan->objd,
 418                 event_name,
 419                 loglevel,
 420                 desc->signature,
 421                 desc->nr_fields,
 422                 desc->fields,
 423                 uri,
 424                 &event->id);
 425         if (ret < 0) {
 426                 DBG("Error (%d) registering event to sessiond", ret);
 427                 goto sessiond_register_error;
 428         }
 429
 430         /* Populate lttng_event structure before tracepoint registration. */
 431         cmm_smp_wmb();
 432         cds_list_add(&event->node, &chan->session->events_head);
 433         cds_hlist_add_head(&event->hlist, head);
 434         return 0;
 435
 436 sessiond_register_error:
 437         free(event);
 438 cache_error:
 439 socket_error:
 440 exist:
 441         return ret;
 442 }
 443
 444 static
 445 int lttng_desc_match_wildcard_enabler(const struct lttng_event_desc *desc,
 446                 struct lttng_enabler *enabler)
 447 {
 448         int loglevel = 0;
 449         unsigned int has_loglevel = 0;
 450
 451         assert(enabler->type == LTTNG_ENABLER_WILDCARD);
 452         /* Compare excluding final '*' */
 453         if (strncmp(desc->name, enabler->event_param.name,
 454                         strlen(enabler->event_param.name) - 1))
 455                 return 0;
 456         if (desc->loglevel) {
 457                 loglevel = *(*desc->loglevel);
 458                 has_loglevel = 1;
 459         }
 460         if (!lttng_loglevel_match(loglevel,
 461                         has_loglevel,
 462                         enabler->event_param.loglevel_type,
 463                         enabler->event_param.loglevel))
 464                 return 0;
 465         return 1;
 466 }
 467
 468 static
 469 int lttng_desc_match_event_enabler(const struct lttng_event_desc *desc,
 470                 struct lttng_enabler *enabler)
 471 {
 472         int loglevel = 0;
 473         unsigned int has_loglevel = 0;
 474
 475         assert(enabler->type == LTTNG_ENABLER_EVENT);
 476         if (strcmp(desc->name, enabler->event_param.name))
 477                 return 0;
 478         if (desc->loglevel) {
 479                 loglevel = *(*desc->loglevel);
 480                 has_loglevel = 1;
 481         }
 482         if (!lttng_loglevel_match(loglevel,
 483                         has_loglevel,
 484                         enabler->event_param.loglevel_type,
 485                         enabler->event_param.loglevel))
 486                 return 0;
 487         return 1;
 488 }
 489
 490 static
 491 int lttng_desc_match_enabler(const struct lttng_event_desc *desc,
 492                 struct lttng_enabler *enabler)
 493 {
 494         switch (enabler->type) {
 495         case LTTNG_ENABLER_WILDCARD:
 496                 return lttng_desc_match_wildcard_enabler(desc, enabler);
 497         case LTTNG_ENABLER_EVENT:
 498                 return lttng_desc_match_event_enabler(desc, enabler);
 499         default:
 500                 return -EINVAL;
 501         }
 502 }
 503
 504 static
 505 int lttng_event_match_enabler(struct lttng_event *event,
 506                 struct lttng_enabler *enabler)
 507 {
 508         return lttng_desc_match_enabler(event->desc, enabler);
 509 }
 510
 511 static
 512 struct lttng_enabler_ref * lttng_event_enabler_ref(struct lttng_event *event,
 513                 struct lttng_enabler *enabler)
 514 {
 515         struct lttng_enabler_ref *enabler_ref;
 516
 517         cds_list_for_each_entry(enabler_ref,
 518                         &event->enablers_ref_head, node) {
 519                 if (enabler_ref->ref == enabler)
 520                         return enabler_ref;
 521         }
 522         return NULL;
 523 }
 524
 525 /*
 526  * Create struct lttng_event if it is missing and present in the list of
 527  * tracepoint probes.
 528  */
 529 static
 530 void lttng_create_event_if_missing(struct lttng_enabler *enabler)
 531 {
 532         struct lttng_session *session = enabler->chan->session;
 533         struct lttng_probe_desc *probe_desc;
 534         const struct lttng_event_desc *desc;
 535         struct lttng_event *event;
 536         int i;
 537         struct cds_list_head *probe_list;
 538
 539         probe_list = lttng_get_probe_list_head();
 540         /*
 541          * For each probe event, if we find that a probe event matches
 542          * our enabler, create an associated lttng_event if not
 543          * already present.
 544          */
 545         cds_list_for_each_entry(probe_desc, probe_list, head) {
 546                 for (i = 0; i < probe_desc->nr_events; i++) {
 547                         int found = 0, ret;
 548                         struct cds_hlist_head *head;
 549                         struct cds_hlist_node *node;
 550                         const char *event_name;
 551                         size_t name_len;
 552                         uint32_t hash;
 553
 554                         desc = probe_desc->event_desc[i];
 555                         if (!lttng_desc_match_enabler(desc, enabler))
 556                                 continue;
 557                         event_name = desc->name;
 558                         name_len = strlen(event_name);
 559
 560                         /*
 561                          * Check if already created.
 562                          */
 563                         hash = jhash(event_name, name_len, 0);
 564                         head = &session->events_ht.table[hash & (LTTNG_UST_EVENT_HT_SIZE - 1)];
 565                         cds_hlist_for_each_entry(event, node, head, hlist) {
 566                                 if (event->desc == desc)
 567                                         found = 1;
 568                         }
 569                         if (found)
 570                                 continue;
 571
 572                         /*
 573                          * We need to create an event for this
 574                          * event probe.
 575                          */
 576                         ret = lttng_event_create(probe_desc->event_desc[i],
 577                                         enabler->chan);
 578                         if (ret) {
 579                                 DBG("Unable to create event %s, error %d\n",
 580                                         probe_desc->event_desc[i]->name, ret);
 581                         }
 582                 }
 583         }
 584 }
 585
 586 /*
 587  * Create events associated with an enabler (if not already present),
 588  * and add backward reference from the event to the enabler.
 589  */
 590 static
 591 int lttng_enabler_ref_events(struct lttng_enabler *enabler)
 592 {
 593         struct lttng_session *session = enabler->chan->session;
 594         struct lttng_event *event;
 595
 596         /* First ensure that probe events are created for this enabler. */
 597         lttng_create_event_if_missing(enabler);
 598
 599         /* For each event matching enabler in session event list. */
 600         cds_list_for_each_entry(event, &session->events_head, node) {
 601                 struct lttng_enabler_ref *enabler_ref;
 602
 603                 if (!lttng_event_match_enabler(event, enabler))
 604                         continue;
 605
 606                 enabler_ref = lttng_event_enabler_ref(event, enabler);
 607                 if (!enabler_ref) {
 608                         /*
 609                          * If no backward ref, create it.
 610                          * Add backward ref from event to enabler.
 611                          */
 612                         enabler_ref = zmalloc(sizeof(*enabler_ref));
 613                         if (!enabler_ref)
 614                                 return -ENOMEM;
 615                         enabler_ref->ref = enabler;
 616                         cds_list_add(&enabler_ref->node,
 617                                 &event->enablers_ref_head);
 618                 }
 619
 620                 /*
 621                  * Link filter bytecodes if not linked yet.
 622                  */
 623                 lttng_enabler_event_link_bytecode(event, enabler);
 624
 625                 /* TODO: merge event context. */
 626         }
 627         return 0;
 628 }
 629
 630 /*
 631  * Called at library load: connect the probe on all enablers matching
 632  * this event.
 633  * called with session mutex held.
 634  * TODO: currently, for each desc added, we iterate on all event desc
 635  * (inefficient). We should create specific code that only target the
 636  * added desc.
 637  */
 638 int lttng_fix_pending_event_desc(const struct lttng_event_desc *desc)
 639 {
 640         struct lttng_session *session;
 641
 642         cds_list_for_each_entry(session, &sessions, node) {
 643                 lttng_session_lazy_sync_enablers(session);
 644         }
 645         return 0;
 646 }
 647
 648 /*
 649  * Only used internally at session destruction.
 650  */
 651 static
 652 void _lttng_event_destroy(struct lttng_event *event)
 653 {
 654         struct lttng_enabler_ref *enabler_ref, *tmp_enabler_ref;
 655
 656         cds_list_del(&event->node);
 657         lttng_destroy_context(event->ctx);
 658         lttng_free_event_filter_runtime(event);
 659         /* Free event enabler refs */
 660         cds_list_for_each_entry_safe(enabler_ref, tmp_enabler_ref,
 661                         &event->enablers_ref_head, node)
 662                 free(enabler_ref);
 663         free(event);
 664 }
 665
 666 void lttng_ust_events_exit(void)
 667 {
 668         struct lttng_session *session, *tmpsession;
 669
 670         cds_list_for_each_entry_safe(session, tmpsession, &sessions, node)
 671                 lttng_session_destroy(session);
 672 }
 673
 674 /*
 675  * Enabler management.
 676  */
 677 struct lttng_enabler *lttng_enabler_create(enum lttng_enabler_type type,
 678                 struct lttng_ust_event *event_param,
 679                 struct lttng_channel *chan)
 680 {
 681         struct lttng_enabler *enabler;
 682
 683         enabler = zmalloc(sizeof(*enabler));
 684         if (!enabler)
 685                 return NULL;
 686         enabler->type = type;
 687         CDS_INIT_LIST_HEAD(&enabler->filter_bytecode_head);
 688         memcpy(&enabler->event_param, event_param,
 689                 sizeof(enabler->event_param));
 690         enabler->chan = chan;
 691         /* ctx left NULL */
 692         enabler->enabled = 1;
 693         cds_list_add(&enabler->node, &enabler->chan->session->enablers_head);
 694         lttng_session_lazy_sync_enablers(enabler->chan->session);
 695         return enabler;
 696 }
 697
 698 int lttng_enabler_enable(struct lttng_enabler *enabler)
 699 {
 700         enabler->enabled = 1;
 701         lttng_session_lazy_sync_enablers(enabler->chan->session);
 702         return 0;
 703 }
 704
 705 int lttng_enabler_disable(struct lttng_enabler *enabler)
 706 {
 707         enabler->enabled = 0;
 708         lttng_session_lazy_sync_enablers(enabler->chan->session);
 709         return 0;
 710 }
 711
 712 int lttng_enabler_attach_bytecode(struct lttng_enabler *enabler,
 713                 struct lttng_ust_filter_bytecode_node *bytecode)
 714 {
 715         bytecode->enabler = enabler;
 716         cds_list_add_tail(&bytecode->node, &enabler->filter_bytecode_head);
 717         lttng_session_lazy_sync_enablers(enabler->chan->session);
 718         return 0;
 719 }
 720
 721 int lttng_attach_context(struct lttng_ust_context *context_param,
 722                 struct lttng_ctx **ctx, struct lttng_session *session)
 723 {
 724         /*
 725          * We cannot attach a context after trace has been started for a
 726          * session because the metadata does not allow expressing this
 727          * information outside of the original channel scope.
 728          */
 729         if (session->been_active)
 730                 return -EPERM;
 731
 732         switch (context_param->ctx) {
 733         case LTTNG_UST_CONTEXT_PTHREAD_ID:
 734                 return lttng_add_pthread_id_to_ctx(ctx);
 735         case LTTNG_UST_CONTEXT_VTID:
 736                 return lttng_add_vtid_to_ctx(ctx);
 737         case LTTNG_UST_CONTEXT_VPID:
 738                 return lttng_add_vpid_to_ctx(ctx);
 739         case LTTNG_UST_CONTEXT_PROCNAME:
 740                 return lttng_add_procname_to_ctx(ctx);
 741         default:
 742                 return -EINVAL;
 743         }
 744 }
 745
 746 int lttng_enabler_attach_context(struct lttng_enabler *enabler,
 747                 struct lttng_ust_context *context_param)
 748 {
 749 #if 0   // disabled for now.
 750         struct lttng_session *session = enabler->chan->session;
 751         int ret;
 752
 753         ret = lttng_attach_context(context_param, &enabler->ctx,
 754                         session);
 755         if (ret)
 756                 return ret;
 757         lttng_session_lazy_sync_enablers(enabler->chan->session);
 758 #endif
 759         return -ENOSYS;
 760 }
 761
 762 static
 763 void lttng_enabler_destroy(struct lttng_enabler *enabler)
 764 {
 765         struct lttng_ust_filter_bytecode_node *filter_node, *tmp_filter_node;
 766
 767         /* Destroy filter bytecode */
 768         cds_list_for_each_entry_safe(filter_node, tmp_filter_node,
 769                         &enabler->filter_bytecode_head, node) {
 770                 free(filter_node);
 771         }
 772
 773         /* Destroy contexts */
 774         lttng_destroy_context(enabler->ctx);
 775
 776         cds_list_del(&enabler->node);
 777         free(enabler);
 778 }
 779
 780 /*
 781  * lttng_session_sync_enablers should be called just before starting a
 782  * session.
 783  */
 784 static
 785 void lttng_session_sync_enablers(struct lttng_session *session)
 786 {
 787         struct lttng_enabler *enabler;
 788         struct lttng_event *event;
 789
 790         cds_list_for_each_entry(enabler, &session->enablers_head, node)
 791                 lttng_enabler_ref_events(enabler);
 792         /*
 793          * For each event, if at least one of its enablers is enabled,
 794          * and its channel and session transient states are enabled, we
 795          * enable the event, else we disable it.
 796          */
 797         cds_list_for_each_entry(event, &session->events_head, node) {
 798                 struct lttng_enabler_ref *enabler_ref;
 799                 struct lttng_bytecode_runtime *runtime;
 800                 int enabled = 0, has_enablers_without_bytecode = 0;
 801
 802                 /* Enable events */
 803                 cds_list_for_each_entry(enabler_ref,
 804                                 &event->enablers_ref_head, node) {
 805                         if (enabler_ref->ref->enabled) {
 806                                 enabled = 1;
 807                                 break;
 808                         }
 809                 }
 810                 /*
 811                  * Enabled state is based on union of enablers, with
 812                  * intesection of session and channel transient enable
 813                  * states.
 814                  */
 815                 enabled = enabled && session->tstate && event->chan->tstate;
 816
 817                 CMM_STORE_SHARED(event->enabled, enabled);
 818                 /*
 819                  * Sync tracepoint registration with event enabled
 820                  * state.
 821                  */
 822                 if (enabled) {
 823                         if (!event->registered)
 824                                 register_event(event);
 825                 } else {
 826                         if (event->registered)
 827                                 unregister_event(event);
 828                 }
 829
 830                 /* Check if has enablers without bytecode enabled */
 831                 cds_list_for_each_entry(enabler_ref,
 832                                 &event->enablers_ref_head, node) {
 833                         if (enabler_ref->ref->enabled
 834                                         && cds_list_empty(&enabler_ref->ref->filter_bytecode_head)) {
 835                                 has_enablers_without_bytecode = 1;
 836                                 break;
 837                         }
 838                 }
 839                 event->has_enablers_without_bytecode =
 840                         has_enablers_without_bytecode;
 841
 842                 /* Enable filters */
 843                 cds_list_for_each_entry(runtime,
 844                                 &event->bytecode_runtime_head, node) {
 845                         lttng_filter_sync_state(runtime);
 846                 }
 847         }
 848 }
 849
 850 /*
 851  * Apply enablers to session events, adding events to session if need
 852  * be. It is required after each modification applied to an active
 853  * session, and right before session "start".
 854  * "lazy" sync means we only sync if required.
 855  */
 856 static
 857 void lttng_session_lazy_sync_enablers(struct lttng_session *session)
 858 {
 859         /* We can skip if session is not active */
 860         if (!session->active)
 861                 return;
 862         lttng_session_sync_enablers(session);
 863 }