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 <lttng/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_ctx_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;
 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
 297         session->statedump_pending = 1;
 298         lttng_ust_sockinfo_session_enabled(session->owner);
 299 end:
 300         return ret;
 301 }
 302
 303 int lttng_session_disable(struct lttng_session *session)
 304 {
 305         int ret = 0;
 306
 307         if (!session->active) {
 308                 ret = -EBUSY;
 309                 goto end;
 310         }
 311         /* Set atomically the state to "inactive" */
 312         CMM_ACCESS_ONCE(session->active) = 0;
 313
 314         /* Set transient enabler state to "disabled" */
 315         session->tstate = 0;
 316         lttng_session_sync_enablers(session);
 317 end:
 318         return ret;
 319 }
 320
 321 int lttng_channel_enable(struct lttng_channel *channel)
 322 {
 323         int ret = 0;
 324
 325         if (channel->enabled) {
 326                 ret = -EBUSY;
 327                 goto end;
 328         }
 329         /* Set transient enabler state to "enabled" */
 330         channel->tstate = 1;
 331         lttng_session_sync_enablers(channel->session);
 332         /* Set atomically the state to "enabled" */
 333         CMM_ACCESS_ONCE(channel->enabled) = 1;
 334 end:
 335         return ret;
 336 }
 337
 338 int lttng_channel_disable(struct lttng_channel *channel)
 339 {
 340         int ret = 0;
 341
 342         if (!channel->enabled) {
 343                 ret = -EBUSY;
 344                 goto end;
 345         }
 346         /* Set atomically the state to "disabled" */
 347         CMM_ACCESS_ONCE(channel->enabled) = 0;
 348         /* Set transient enabler state to "enabled" */
 349         channel->tstate = 0;
 350         lttng_session_sync_enablers(channel->session);
 351 end:
 352         return ret;
 353 }
 354
 355 /*
 356  * Supports event creation while tracing session is active.
 357  */
 358 static
 359 int lttng_event_create(const struct lttng_event_desc *desc,
 360                 struct lttng_channel *chan)
 361 {
 362         const char *event_name = desc->name;
 363         struct lttng_event *event;
 364         struct lttng_session *session = chan->session;
 365         struct cds_hlist_head *head;
 366         struct cds_hlist_node *node;
 367         int ret = 0;
 368         size_t name_len = strlen(event_name);
 369         uint32_t hash;
 370         int notify_socket, loglevel;
 371         const char *uri;
 372
 373         hash = jhash(event_name, name_len, 0);
 374         head = &chan->session->events_ht.table[hash & (LTTNG_UST_EVENT_HT_SIZE - 1)];
 375         cds_hlist_for_each_entry(event, node, head, hlist) {
 376                 assert(event->desc);
 377                 if (!strncmp(event->desc->name, desc->name,
 378                                         LTTNG_UST_SYM_NAME_LEN - 1)
 379                                 && chan == event->chan) {
 380                         ret = -EEXIST;
 381                         goto exist;
 382                 }
 383         }
 384
 385         notify_socket = lttng_get_notify_socket(session->owner);
 386         if (notify_socket < 0) {
 387                 ret = notify_socket;
 388                 goto socket_error;
 389         }
 390
 391         /*
 392          * Check if loglevel match. Refuse to connect event if not.
 393          */
 394         event = zmalloc(sizeof(struct lttng_event));
 395         if (!event) {
 396                 ret = -ENOMEM;
 397                 goto cache_error;
 398         }
 399         event->chan = chan;
 400
 401         /* Event will be enabled by enabler sync. */
 402         event->enabled = 0;
 403         event->registered = 0;
 404         CDS_INIT_LIST_HEAD(&event->bytecode_runtime_head);
 405         CDS_INIT_LIST_HEAD(&event->enablers_ref_head);
 406         event->desc = desc;
 407
 408         if (desc->loglevel)
 409                 loglevel = *(*event->desc->loglevel);
 410         else
 411                 loglevel = TRACE_DEFAULT;
 412         if (desc->u.ext.model_emf_uri)
 413                 uri = *(desc->u.ext.model_emf_uri);
 414         else
 415                 uri = NULL;
 416
 417         /* Fetch event ID from sessiond */
 418         ret = ustcomm_register_event(notify_socket,
 419                 session->objd,
 420                 chan->objd,
 421                 event_name,
 422                 loglevel,
 423                 desc->signature,
 424                 desc->nr_fields,
 425                 desc->fields,
 426                 uri,
 427                 &event->id);
 428         if (ret < 0) {
 429                 DBG("Error (%d) registering event to sessiond", ret);
 430                 goto sessiond_register_error;
 431         }
 432
 433         /* Populate lttng_event structure before tracepoint registration. */
 434         cmm_smp_wmb();
 435         cds_list_add(&event->node, &chan->session->events_head);
 436         cds_hlist_add_head(&event->hlist, head);
 437         return 0;
 438
 439 sessiond_register_error:
 440         free(event);
 441 cache_error:
 442 socket_error:
 443 exist:
 444         return ret;
 445 }
 446
 447 static
 448 int lttng_desc_match_wildcard_enabler(const struct lttng_event_desc *desc,
 449                 struct lttng_enabler *enabler)
 450 {
 451         int loglevel = 0;
 452         unsigned int has_loglevel = 0;
 453
 454         assert(enabler->type == LTTNG_ENABLER_WILDCARD);
 455         /* Compare excluding final '*' */
 456         if (strncmp(desc->name, enabler->event_param.name,
 457                         strlen(enabler->event_param.name) - 1))
 458                 return 0;
 459         if (desc->loglevel) {
 460                 loglevel = *(*desc->loglevel);
 461                 has_loglevel = 1;
 462         }
 463         if (!lttng_loglevel_match(loglevel,
 464                         has_loglevel,
 465                         enabler->event_param.loglevel_type,
 466                         enabler->event_param.loglevel))
 467                 return 0;
 468         return 1;
 469 }
 470
 471 static
 472 int lttng_desc_match_event_enabler(const struct lttng_event_desc *desc,
 473                 struct lttng_enabler *enabler)
 474 {
 475         int loglevel = 0;
 476         unsigned int has_loglevel = 0;
 477
 478         assert(enabler->type == LTTNG_ENABLER_EVENT);
 479         if (strcmp(desc->name, enabler->event_param.name))
 480                 return 0;
 481         if (desc->loglevel) {
 482                 loglevel = *(*desc->loglevel);
 483                 has_loglevel = 1;
 484         }
 485         if (!lttng_loglevel_match(loglevel,
 486                         has_loglevel,
 487                         enabler->event_param.loglevel_type,
 488                         enabler->event_param.loglevel))
 489                 return 0;
 490         return 1;
 491 }
 492
 493 static
 494 int lttng_desc_match_enabler(const struct lttng_event_desc *desc,
 495                 struct lttng_enabler *enabler)
 496 {
 497         struct lttng_ust_excluder_node *excluder;
 498
 499         /* If event matches with an excluder, return 'does not match' */
 500         cds_list_for_each_entry(excluder, &enabler->excluder_head, node) {
 501                 int count;
 502
 503                 for (count = 0; count < excluder->excluder.count; count++) {
 504                         int found, len;
 505                         char *excluder_name;
 506
 507                         excluder_name = (char *) (excluder->excluder.names)
 508                                         + count * LTTNG_UST_SYM_NAME_LEN;
 509                         len = strnlen(excluder_name, LTTNG_UST_SYM_NAME_LEN);
 510                         if (len > 0 && excluder_name[len - 1] == '*') {
 511                                 found = !strncmp(desc->name, excluder_name,
 512                                                 len - 1);
 513                         } else {
 514                                 found = !strncmp(desc->name, excluder_name,
 515                                                 LTTNG_UST_SYM_NAME_LEN - 1);
 516                         }
 517                         if (found) {
 518                                 return 0;
 519                         }
 520                 }
 521         }
 522         switch (enabler->type) {
 523         case LTTNG_ENABLER_WILDCARD:
 524                 return lttng_desc_match_wildcard_enabler(desc, enabler);
 525         case LTTNG_ENABLER_EVENT:
 526                 return lttng_desc_match_event_enabler(desc, enabler);
 527         default:
 528                 return -EINVAL;
 529         }
 530 }
 531
 532 static
 533 int lttng_event_match_enabler(struct lttng_event *event,
 534                 struct lttng_enabler *enabler)
 535 {
 536         if (lttng_desc_match_enabler(event->desc, enabler)
 537                         && event->chan == enabler->chan)
 538                 return 1;
 539         else
 540                 return 0;
 541 }
 542
 543 static
 544 struct lttng_enabler_ref * lttng_event_enabler_ref(struct lttng_event *event,
 545                 struct lttng_enabler *enabler)
 546 {
 547         struct lttng_enabler_ref *enabler_ref;
 548
 549         cds_list_for_each_entry(enabler_ref,
 550                         &event->enablers_ref_head, node) {
 551                 if (enabler_ref->ref == enabler)
 552                         return enabler_ref;
 553         }
 554         return NULL;
 555 }
 556
 557 /*
 558  * Create struct lttng_event if it is missing and present in the list of
 559  * tracepoint probes.
 560  */
 561 static
 562 void lttng_create_event_if_missing(struct lttng_enabler *enabler)
 563 {
 564         struct lttng_session *session = enabler->chan->session;
 565         struct lttng_probe_desc *probe_desc;
 566         const struct lttng_event_desc *desc;
 567         struct lttng_event *event;
 568         int i;
 569         struct cds_list_head *probe_list;
 570
 571         probe_list = lttng_get_probe_list_head();
 572         /*
 573          * For each probe event, if we find that a probe event matches
 574          * our enabler, create an associated lttng_event if not
 575          * already present.
 576          */
 577         cds_list_for_each_entry(probe_desc, probe_list, head) {
 578                 for (i = 0; i < probe_desc->nr_events; i++) {
 579                         int found = 0, ret;
 580                         struct cds_hlist_head *head;
 581                         struct cds_hlist_node *node;
 582                         const char *event_name;
 583                         size_t name_len;
 584                         uint32_t hash;
 585
 586                         desc = probe_desc->event_desc[i];
 587                         if (!lttng_desc_match_enabler(desc, enabler))
 588                                 continue;
 589                         event_name = desc->name;
 590                         name_len = strlen(event_name);
 591
 592                         /*
 593                          * Check if already created.
 594                          */
 595                         hash = jhash(event_name, name_len, 0);
 596                         head = &session->events_ht.table[hash & (LTTNG_UST_EVENT_HT_SIZE - 1)];
 597                         cds_hlist_for_each_entry(event, node, head, hlist) {
 598                                 if (event->desc == desc
 599                                                 && event->chan == enabler->chan)
 600                                         found = 1;
 601                         }
 602                         if (found)
 603                                 continue;
 604
 605                         /*
 606                          * We need to create an event for this
 607                          * event probe.
 608                          */
 609                         ret = lttng_event_create(probe_desc->event_desc[i],
 610                                         enabler->chan);
 611                         if (ret) {
 612                                 DBG("Unable to create event %s, error %d\n",
 613                                         probe_desc->event_desc[i]->name, ret);
 614                         }
 615                 }
 616         }
 617 }
 618
 619 /*
 620  * Create events associated with an enabler (if not already present),
 621  * and add backward reference from the event to the enabler.
 622  */
 623 static
 624 int lttng_enabler_ref_events(struct lttng_enabler *enabler)
 625 {
 626         struct lttng_session *session = enabler->chan->session;
 627         struct lttng_event *event;
 628
 629         /* First ensure that probe events are created for this enabler. */
 630         lttng_create_event_if_missing(enabler);
 631
 632         /* For each event matching enabler in session event list. */
 633         cds_list_for_each_entry(event, &session->events_head, node) {
 634                 struct lttng_enabler_ref *enabler_ref;
 635
 636                 if (!lttng_event_match_enabler(event, enabler))
 637                         continue;
 638
 639                 enabler_ref = lttng_event_enabler_ref(event, enabler);
 640                 if (!enabler_ref) {
 641                         /*
 642                          * If no backward ref, create it.
 643                          * Add backward ref from event to enabler.
 644                          */
 645                         enabler_ref = zmalloc(sizeof(*enabler_ref));
 646                         if (!enabler_ref)
 647                                 return -ENOMEM;
 648                         enabler_ref->ref = enabler;
 649                         cds_list_add(&enabler_ref->node,
 650                                 &event->enablers_ref_head);
 651                 }
 652
 653                 /*
 654                  * Link filter bytecodes if not linked yet.
 655                  */
 656                 lttng_enabler_event_link_bytecode(event, enabler);
 657
 658                 /* TODO: merge event context. */
 659         }
 660         return 0;
 661 }
 662
 663 /*
 664  * Called at library load: connect the probe on all enablers matching
 665  * this event.
 666  * Called with session mutex held.
 667  */
 668 int lttng_fix_pending_events(void)
 669 {
 670         struct lttng_session *session;
 671
 672         cds_list_for_each_entry(session, &sessions, node) {
 673                 lttng_session_lazy_sync_enablers(session);
 674         }
 675         return 0;
 676 }
 677
 678 /*
 679  * Called after session enable: For each session, execute pending statedumps.
 680  */
 681 int lttng_handle_pending_statedumps(t_statedump_func_ptr statedump_func_ptr)
 682 {
 683         struct lttng_session *session;
 684
 685         cds_list_for_each_entry(session, &sessions, node) {
 686                 if (session->statedump_pending) {
 687                         session->statedump_pending = 0;
 688                         statedump_func_ptr(session);
 689                 }
 690         }
 691         return 0;
 692 }
 693
 694 /*
 695  * Only used internally at session destruction.
 696  */
 697 static
 698 void _lttng_event_destroy(struct lttng_event *event)
 699 {
 700         struct lttng_enabler_ref *enabler_ref, *tmp_enabler_ref;
 701
 702         cds_list_del(&event->node);
 703         lttng_destroy_context(event->ctx);
 704         lttng_free_event_filter_runtime(event);
 705         /* Free event enabler refs */
 706         cds_list_for_each_entry_safe(enabler_ref, tmp_enabler_ref,
 707                         &event->enablers_ref_head, node)
 708                 free(enabler_ref);
 709         free(event);
 710 }
 711
 712 void lttng_ust_events_exit(void)
 713 {
 714         struct lttng_session *session, *tmpsession;
 715
 716         cds_list_for_each_entry_safe(session, tmpsession, &sessions, node)
 717                 lttng_session_destroy(session);
 718 }
 719
 720 /*
 721  * Enabler management.
 722  */
 723 struct lttng_enabler *lttng_enabler_create(enum lttng_enabler_type type,
 724                 struct lttng_ust_event *event_param,
 725                 struct lttng_channel *chan)
 726 {
 727         struct lttng_enabler *enabler;
 728
 729         enabler = zmalloc(sizeof(*enabler));
 730         if (!enabler)
 731                 return NULL;
 732         enabler->type = type;
 733         CDS_INIT_LIST_HEAD(&enabler->filter_bytecode_head);
 734         CDS_INIT_LIST_HEAD(&enabler->excluder_head);
 735         memcpy(&enabler->event_param, event_param,
 736                 sizeof(enabler->event_param));
 737         enabler->chan = chan;
 738         /* ctx left NULL */
 739         enabler->enabled = 1;
 740         cds_list_add(&enabler->node, &enabler->chan->session->enablers_head);
 741         lttng_session_lazy_sync_enablers(enabler->chan->session);
 742         return enabler;
 743 }
 744
 745 int lttng_enabler_enable(struct lttng_enabler *enabler)
 746 {
 747         enabler->enabled = 1;
 748         lttng_session_lazy_sync_enablers(enabler->chan->session);
 749         return 0;
 750 }
 751
 752 int lttng_enabler_disable(struct lttng_enabler *enabler)
 753 {
 754         enabler->enabled = 0;
 755         lttng_session_lazy_sync_enablers(enabler->chan->session);
 756         return 0;
 757 }
 758
 759 int lttng_enabler_attach_bytecode(struct lttng_enabler *enabler,
 760                 struct lttng_ust_filter_bytecode_node *bytecode)
 761 {
 762         bytecode->enabler = enabler;
 763         cds_list_add_tail(&bytecode->node, &enabler->filter_bytecode_head);
 764         lttng_session_lazy_sync_enablers(enabler->chan->session);
 765         return 0;
 766 }
 767
 768 int lttng_enabler_attach_exclusion(struct lttng_enabler *enabler,
 769                 struct lttng_ust_excluder_node *excluder)
 770 {
 771         excluder->enabler = enabler;
 772         cds_list_add_tail(&excluder->node, &enabler->excluder_head);
 773         lttng_session_lazy_sync_enablers(enabler->chan->session);
 774         return 0;
 775 }
 776
 777 int lttng_attach_context(struct lttng_ust_context *context_param,
 778                 struct lttng_ctx **ctx, struct lttng_session *session)
 779 {
 780         /*
 781          * We cannot attach a context after trace has been started for a
 782          * session because the metadata does not allow expressing this
 783          * information outside of the original channel scope.
 784          */
 785         if (session->been_active)
 786                 return -EPERM;
 787
 788         switch (context_param->ctx) {
 789         case LTTNG_UST_CONTEXT_PTHREAD_ID:
 790                 return lttng_add_pthread_id_to_ctx(ctx);
 791         case LTTNG_UST_CONTEXT_VTID:
 792                 return lttng_add_vtid_to_ctx(ctx);
 793         case LTTNG_UST_CONTEXT_VPID:
 794                 return lttng_add_vpid_to_ctx(ctx);
 795         case LTTNG_UST_CONTEXT_PROCNAME:
 796                 return lttng_add_procname_to_ctx(ctx);
 797         case LTTNG_UST_CONTEXT_IP:
 798                 return lttng_add_ip_to_ctx(ctx);
 799         default:
 800                 return -EINVAL;
 801         }
 802 }
 803
 804 int lttng_enabler_attach_context(struct lttng_enabler *enabler,
 805                 struct lttng_ust_context *context_param)
 806 {
 807 #if 0   // disabled for now.
 808         struct lttng_session *session = enabler->chan->session;
 809         int ret;
 810
 811         ret = lttng_attach_context(context_param, &enabler->ctx,
 812                         session);
 813         if (ret)
 814                 return ret;
 815         lttng_session_lazy_sync_enablers(enabler->chan->session);
 816 #endif
 817         return -ENOSYS;
 818 }
 819
 820 static
 821 void lttng_enabler_destroy(struct lttng_enabler *enabler)
 822 {
 823         struct lttng_ust_filter_bytecode_node *filter_node, *tmp_filter_node;
 824         struct lttng_ust_excluder_node *excluder_node, *tmp_excluder_node;
 825
 826         /* Destroy filter bytecode */
 827         cds_list_for_each_entry_safe(filter_node, tmp_filter_node,
 828                         &enabler->filter_bytecode_head, node) {
 829                 free(filter_node);
 830         }
 831
 832         /* Destroy excluders */
 833         cds_list_for_each_entry_safe(excluder_node, tmp_excluder_node,
 834                         &enabler->excluder_head, node) {
 835                 free(excluder_node);
 836         }
 837
 838         /* Destroy contexts */
 839         lttng_destroy_context(enabler->ctx);
 840
 841         cds_list_del(&enabler->node);
 842         free(enabler);
 843 }
 844
 845 /*
 846  * lttng_session_sync_enablers should be called just before starting a
 847  * session.
 848  */
 849 static
 850 void lttng_session_sync_enablers(struct lttng_session *session)
 851 {
 852         struct lttng_enabler *enabler;
 853         struct lttng_event *event;
 854
 855         cds_list_for_each_entry(enabler, &session->enablers_head, node)
 856                 lttng_enabler_ref_events(enabler);
 857         /*
 858          * For each event, if at least one of its enablers is enabled,
 859          * and its channel and session transient states are enabled, we
 860          * enable the event, else we disable it.
 861          */
 862         cds_list_for_each_entry(event, &session->events_head, node) {
 863                 struct lttng_enabler_ref *enabler_ref;
 864                 struct lttng_bytecode_runtime *runtime;
 865                 int enabled = 0, has_enablers_without_bytecode = 0;
 866
 867                 /* Enable events */
 868                 cds_list_for_each_entry(enabler_ref,
 869                                 &event->enablers_ref_head, node) {
 870                         if (enabler_ref->ref->enabled) {
 871                                 enabled = 1;
 872                                 break;
 873                         }
 874                 }
 875                 /*
 876                  * Enabled state is based on union of enablers, with
 877                  * intesection of session and channel transient enable
 878                  * states.
 879                  */
 880                 enabled = enabled && session->tstate && event->chan->tstate;
 881
 882                 CMM_STORE_SHARED(event->enabled, enabled);
 883                 /*
 884                  * Sync tracepoint registration with event enabled
 885                  * state.
 886                  */
 887                 if (enabled) {
 888                         if (!event->registered)
 889                                 register_event(event);
 890                 } else {
 891                         if (event->registered)
 892                                 unregister_event(event);
 893                 }
 894
 895                 /* Check if has enablers without bytecode enabled */
 896                 cds_list_for_each_entry(enabler_ref,
 897                                 &event->enablers_ref_head, node) {
 898                         if (enabler_ref->ref->enabled
 899                                         && cds_list_empty(&enabler_ref->ref->filter_bytecode_head)) {
 900                                 has_enablers_without_bytecode = 1;
 901                                 break;
 902                         }
 903                 }
 904                 event->has_enablers_without_bytecode =
 905                         has_enablers_without_bytecode;
 906
 907                 /* Enable filters */
 908                 cds_list_for_each_entry(runtime,
 909                                 &event->bytecode_runtime_head, node) {
 910                         lttng_filter_sync_state(runtime);
 911                 }
 912         }
 913 }
 914
 915 /*
 916  * Apply enablers to session events, adding events to session if need
 917  * be. It is required after each modification applied to an active
 918  * session, and right before session "start".
 919  * "lazy" sync means we only sync if required.
 920  */
 921 static
 922 void lttng_session_lazy_sync_enablers(struct lttng_session *session)
 923 {
 924         /* We can skip if session is not active */
 925         if (!session->active)
 926                 return;
 927         lttng_session_sync_enablers(session);
 928 }