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 "lttng-ust-baddr.h"
  58 #include "wait.h"
  59 #include "../libringbuffer/shm.h"
  60 #include "jhash.h"
  61
  62 /*
  63  * All operations within this file are called by the communication
  64  * thread, under ust_lock protection.
  65  */
  66
  67 static CDS_LIST_HEAD(sessions);
  68
  69 struct cds_list_head *_lttng_get_sessions(void)
  70 {
  71         return &sessions;
  72 }
  73
  74 static void _lttng_event_destroy(struct lttng_event *event);
  75
  76 static
  77 void lttng_session_lazy_sync_enablers(struct lttng_session *session);
  78 static
  79 void lttng_session_sync_enablers(struct lttng_session *session);
  80 static
  81 void lttng_enabler_destroy(struct lttng_enabler *enabler);
  82
  83 /*
  84  * Called with ust lock held.
  85  */
  86 int lttng_session_active(void)
  87 {
  88         struct lttng_session *iter;
  89
  90         cds_list_for_each_entry(iter, &sessions, node) {
  91                 if (iter->active)
  92                         return 1;
  93         }
  94         return 0;
  95 }
  96
  97 static
  98 int lttng_loglevel_match(int loglevel,
  99                 unsigned int has_loglevel,
 100                 enum lttng_ust_loglevel_type req_type,
 101                 int req_loglevel)
 102 {
 103         if (req_type == LTTNG_UST_LOGLEVEL_ALL)
 104                 return 1;
 105         if (!has_loglevel)
 106                 loglevel = TRACE_DEFAULT;
 107         switch (req_type) {
 108         case LTTNG_UST_LOGLEVEL_RANGE:
 109                 if (loglevel <= req_loglevel || req_loglevel == -1)
 110                         return 1;
 111                 else
 112                         return 0;
 113         case LTTNG_UST_LOGLEVEL_SINGLE:
 114                 if (loglevel == req_loglevel || req_loglevel == -1)
 115                         return 1;
 116                 else
 117                         return 0;
 118         case LTTNG_UST_LOGLEVEL_ALL:
 119         default:
 120                 return 1;
 121         }
 122 }
 123
 124 void synchronize_trace(void)
 125 {
 126         synchronize_rcu();
 127 }
 128
 129 struct lttng_session *lttng_session_create(void)
 130 {
 131         struct lttng_session *session;
 132         int i;
 133
 134         session = zmalloc(sizeof(struct lttng_session));
 135         if (!session)
 136                 return NULL;
 137         CDS_INIT_LIST_HEAD(&session->chan_head);
 138         CDS_INIT_LIST_HEAD(&session->events_head);
 139         CDS_INIT_LIST_HEAD(&session->enablers_head);
 140         for (i = 0; i < LTTNG_UST_EVENT_HT_SIZE; i++)
 141                 CDS_INIT_HLIST_HEAD(&session->events_ht.table[i]);
 142         cds_list_add(&session->node, &sessions);
 143         return session;
 144 }
 145
 146 /*
 147  * Only used internally at session destruction.
 148  */
 149 static
 150 void _lttng_channel_unmap(struct lttng_channel *lttng_chan)
 151 {
 152         struct channel *chan;
 153         struct lttng_ust_shm_handle *handle;
 154
 155         cds_list_del(&lttng_chan->node);
 156         lttng_destroy_context(lttng_chan->ctx);
 157         chan = lttng_chan->chan;
 158         handle = lttng_chan->handle;
 159         /*
 160          * note: lttng_chan is private data contained within handle. It
 161          * will be freed along with the handle.
 162          */
 163         channel_destroy(chan, handle, 0);
 164 }
 165
 166 static
 167 void register_event(struct lttng_event *event)
 168 {
 169         int ret;
 170         const struct lttng_event_desc *desc;
 171
 172         assert(event->registered == 0);
 173         desc = event->desc;
 174         ret = __tracepoint_probe_register(desc->name,
 175                         desc->probe_callback,
 176                         event, desc->signature);
 177         WARN_ON_ONCE(ret);
 178         if (!ret)
 179                 event->registered = 1;
 180 }
 181
 182 static
 183 void unregister_event(struct lttng_event *event)
 184 {
 185         int ret;
 186         const struct lttng_event_desc *desc;
 187
 188         assert(event->registered == 1);
 189         desc = event->desc;
 190         ret = __tracepoint_probe_unregister(desc->name,
 191                         desc->probe_callback,
 192                         event);
 193         WARN_ON_ONCE(ret);
 194         if (!ret)
 195                 event->registered = 0;
 196 }
 197
 198 /*
 199  * Only used internally at session destruction.
 200  */
 201 static
 202 void _lttng_event_unregister(struct lttng_event *event)
 203 {
 204         if (event->registered)
 205                 unregister_event(event);
 206 }
 207
 208 void lttng_session_destroy(struct lttng_session *session)
 209 {
 210         struct lttng_channel *chan, *tmpchan;
 211         struct lttng_event *event, *tmpevent;
 212         struct lttng_enabler *enabler, *tmpenabler;
 213
 214         CMM_ACCESS_ONCE(session->active) = 0;
 215         cds_list_for_each_entry(event, &session->events_head, node) {
 216                 _lttng_event_unregister(event);
 217         }
 218         synchronize_trace();    /* Wait for in-flight events to complete */
 219         cds_list_for_each_entry_safe(enabler, tmpenabler,
 220                         &session->enablers_head, node)
 221                 lttng_enabler_destroy(enabler);
 222         cds_list_for_each_entry_safe(event, tmpevent,
 223                         &session->events_head, node)
 224                 _lttng_event_destroy(event);
 225         cds_list_for_each_entry_safe(chan, tmpchan, &session->chan_head, node)
 226                 _lttng_channel_unmap(chan);
 227         cds_list_del(&session->node);
 228         free(session);
 229 }
 230
 231 int lttng_session_enable(struct lttng_session *session)
 232 {
 233         int ret = 0;
 234         struct lttng_channel *chan;
 235         int notify_socket;
 236
 237         if (session->active) {
 238                 ret = -EBUSY;
 239                 goto end;
 240         }
 241
 242         notify_socket = lttng_get_notify_socket(session->owner);
 243         if (notify_socket < 0)
 244                 return notify_socket;
 245
 246         /* Set transient enabler state to "enabled" */
 247         session->tstate = 1;
 248         /* We need to sync enablers with session before activation. */
 249         lttng_session_sync_enablers(session);
 250
 251         /*
 252          * Snapshot the number of events per channel to know the type of header
 253          * we need to use.
 254          */
 255         cds_list_for_each_entry(chan, &session->chan_head, node) {
 256                 const struct lttng_ctx *ctx;
 257                 const struct lttng_ctx_field *fields = NULL;
 258                 size_t nr_fields = 0;
 259                 uint32_t chan_id;
 260
 261                 /* don't change it if session stop/restart */
 262                 if (chan->header_type)
 263                         continue;
 264                 ctx = chan->ctx;
 265                 if (ctx) {
 266                         nr_fields = ctx->nr_fields;
 267                         fields = ctx->fields;
 268                 }
 269                 ret = ustcomm_register_channel(notify_socket,
 270                         session->objd,
 271                         chan->objd,
 272                         nr_fields,
 273                         fields,
 274                         &chan_id,
 275                         &chan->header_type);
 276                 if (ret) {
 277                         DBG("Error (%d) registering channel to sessiond", ret);
 278                         return ret;
 279                 }
 280                 if (chan_id != chan->id) {
 281                         DBG("Error: channel registration id (%u) does not match id assigned at creation (%u)",
 282                                 chan_id, chan->id);
 283                         return -EINVAL;
 284                 }
 285         }
 286
 287         /* Set atomically the state to "active" */
 288         CMM_ACCESS_ONCE(session->active) = 1;
 289         CMM_ACCESS_ONCE(session->been_active) = 1;
 290
 291         session->statedump_pending = 1;
 292         lttng_ust_sockinfo_session_enabled(session->owner);
 293 end:
 294         return ret;
 295 }
 296
 297 int lttng_session_disable(struct lttng_session *session)
 298 {
 299         int ret = 0;
 300
 301         if (!session->active) {
 302                 ret = -EBUSY;
 303                 goto end;
 304         }
 305         /* Set atomically the state to "inactive" */
 306         CMM_ACCESS_ONCE(session->active) = 0;
 307
 308         /* Set transient enabler state to "disabled" */
 309         session->tstate = 0;
 310         lttng_session_sync_enablers(session);
 311 end:
 312         return ret;
 313 }
 314
 315 int lttng_channel_enable(struct lttng_channel *channel)
 316 {
 317         int ret = 0;
 318
 319         if (channel->enabled) {
 320                 ret = -EBUSY;
 321                 goto end;
 322         }
 323         /* Set transient enabler state to "enabled" */
 324         channel->tstate = 1;
 325         lttng_session_sync_enablers(channel->session);
 326         /* Set atomically the state to "enabled" */
 327         CMM_ACCESS_ONCE(channel->enabled) = 1;
 328 end:
 329         return ret;
 330 }
 331
 332 int lttng_channel_disable(struct lttng_channel *channel)
 333 {
 334         int ret = 0;
 335
 336         if (!channel->enabled) {
 337                 ret = -EBUSY;
 338                 goto end;
 339         }
 340         /* Set atomically the state to "disabled" */
 341         CMM_ACCESS_ONCE(channel->enabled) = 0;
 342         /* Set transient enabler state to "enabled" */
 343         channel->tstate = 0;
 344         lttng_session_sync_enablers(channel->session);
 345 end:
 346         return ret;
 347 }
 348
 349 /*
 350  * Supports event creation while tracing session is active.
 351  */
 352 static
 353 int lttng_event_create(const struct lttng_event_desc *desc,
 354                 struct lttng_channel *chan)
 355 {
 356         const char *event_name = desc->name;
 357         struct lttng_event *event;
 358         struct lttng_session *session = chan->session;
 359         struct cds_hlist_head *head;
 360         struct cds_hlist_node *node;
 361         int ret = 0;
 362         size_t name_len = strlen(event_name);
 363         uint32_t hash;
 364         int notify_socket, loglevel;
 365         const char *uri;
 366
 367         hash = jhash(event_name, name_len, 0);
 368         head = &chan->session->events_ht.table[hash & (LTTNG_UST_EVENT_HT_SIZE - 1)];
 369         cds_hlist_for_each_entry(event, node, head, hlist) {
 370                 assert(event->desc);
 371                 if (!strncmp(event->desc->name, desc->name,
 372                                         LTTNG_UST_SYM_NAME_LEN - 1)
 373                                 && chan == event->chan) {
 374                         ret = -EEXIST;
 375                         goto exist;
 376                 }
 377         }
 378
 379         notify_socket = lttng_get_notify_socket(session->owner);
 380         if (notify_socket < 0) {
 381                 ret = notify_socket;
 382                 goto socket_error;
 383         }
 384
 385         /*
 386          * Check if loglevel match. Refuse to connect event if not.
 387          */
 388         event = zmalloc(sizeof(struct lttng_event));
 389         if (!event) {
 390                 ret = -ENOMEM;
 391                 goto cache_error;
 392         }
 393         event->chan = chan;
 394
 395         /* Event will be enabled by enabler sync. */
 396         event->enabled = 0;
 397         event->registered = 0;
 398         CDS_INIT_LIST_HEAD(&event->bytecode_runtime_head);
 399         CDS_INIT_LIST_HEAD(&event->enablers_ref_head);
 400         event->desc = desc;
 401
 402         if (desc->loglevel)
 403                 loglevel = *(*event->desc->loglevel);
 404         else
 405                 loglevel = TRACE_DEFAULT;
 406         if (desc->u.ext.model_emf_uri)
 407                 uri = *(desc->u.ext.model_emf_uri);
 408         else
 409                 uri = NULL;
 410
 411         /* Fetch event ID from sessiond */
 412         ret = ustcomm_register_event(notify_socket,
 413                 session->objd,
 414                 chan->objd,
 415                 event_name,
 416                 loglevel,
 417                 desc->signature,
 418                 desc->nr_fields,
 419                 desc->fields,
 420                 uri,
 421                 &event->id);
 422         if (ret < 0) {
 423                 DBG("Error (%d) registering event to sessiond", ret);
 424                 goto sessiond_register_error;
 425         }
 426
 427         /* Populate lttng_event structure before tracepoint registration. */
 428         cmm_smp_wmb();
 429         cds_list_add(&event->node, &chan->session->events_head);
 430         cds_hlist_add_head(&event->hlist, head);
 431         return 0;
 432
 433 sessiond_register_error:
 434         free(event);
 435 cache_error:
 436 socket_error:
 437 exist:
 438         return ret;
 439 }
 440
 441 static
 442 int lttng_desc_match_wildcard_enabler(const struct lttng_event_desc *desc,
 443                 struct lttng_enabler *enabler)
 444 {
 445         int loglevel = 0;
 446         unsigned int has_loglevel = 0;
 447
 448         assert(enabler->type == LTTNG_ENABLER_WILDCARD);
 449         /* Compare excluding final '*' */
 450         if (strncmp(desc->name, enabler->event_param.name,
 451                         strlen(enabler->event_param.name) - 1))
 452                 return 0;
 453         if (desc->loglevel) {
 454                 loglevel = *(*desc->loglevel);
 455                 has_loglevel = 1;
 456         }
 457         if (!lttng_loglevel_match(loglevel,
 458                         has_loglevel,
 459                         enabler->event_param.loglevel_type,
 460                         enabler->event_param.loglevel))
 461                 return 0;
 462         return 1;
 463 }
 464
 465 static
 466 int lttng_desc_match_event_enabler(const struct lttng_event_desc *desc,
 467                 struct lttng_enabler *enabler)
 468 {
 469         int loglevel = 0;
 470         unsigned int has_loglevel = 0;
 471
 472         assert(enabler->type == LTTNG_ENABLER_EVENT);
 473         if (strcmp(desc->name, enabler->event_param.name))
 474                 return 0;
 475         if (desc->loglevel) {
 476                 loglevel = *(*desc->loglevel);
 477                 has_loglevel = 1;
 478         }
 479         if (!lttng_loglevel_match(loglevel,
 480                         has_loglevel,
 481                         enabler->event_param.loglevel_type,
 482                         enabler->event_param.loglevel))
 483                 return 0;
 484         return 1;
 485 }
 486
 487 static
 488 int lttng_desc_match_enabler(const struct lttng_event_desc *desc,
 489                 struct lttng_enabler *enabler)
 490 {
 491         struct lttng_ust_excluder_node *excluder;
 492
 493         /* If event matches with an excluder, return 'does not match' */
 494         cds_list_for_each_entry(excluder, &enabler->excluder_head, node) {
 495                 int count;
 496
 497                 for (count = 0; count < excluder->excluder.count; count++) {
 498                         int found, len;
 499                         char *excluder_name;
 500
 501                         excluder_name = (char *) (excluder->excluder.names)
 502                                         + count * LTTNG_UST_SYM_NAME_LEN;
 503                         len = strnlen(excluder_name, LTTNG_UST_SYM_NAME_LEN);
 504                         if (len > 0 && excluder_name[len - 1] == '*') {
 505                                 found = !strncmp(desc->name, excluder_name,
 506                                                 len - 1);
 507                         } else {
 508                                 found = !strncmp(desc->name, excluder_name,
 509                                                 LTTNG_UST_SYM_NAME_LEN - 1);
 510                         }
 511                         if (found) {
 512                                 return 0;
 513                         }
 514                 }
 515         }
 516         switch (enabler->type) {
 517         case LTTNG_ENABLER_WILDCARD:
 518                 return lttng_desc_match_wildcard_enabler(desc, enabler);
 519         case LTTNG_ENABLER_EVENT:
 520                 return lttng_desc_match_event_enabler(desc, enabler);
 521         default:
 522                 return -EINVAL;
 523         }
 524 }
 525
 526 static
 527 int lttng_event_match_enabler(struct lttng_event *event,
 528                 struct lttng_enabler *enabler)
 529 {
 530         if (lttng_desc_match_enabler(event->desc, enabler)
 531                         && event->chan == enabler->chan)
 532                 return 1;
 533         else
 534                 return 0;
 535 }
 536
 537 static
 538 struct lttng_enabler_ref * lttng_event_enabler_ref(struct lttng_event *event,
 539                 struct lttng_enabler *enabler)
 540 {
 541         struct lttng_enabler_ref *enabler_ref;
 542
 543         cds_list_for_each_entry(enabler_ref,
 544                         &event->enablers_ref_head, node) {
 545                 if (enabler_ref->ref == enabler)
 546                         return enabler_ref;
 547         }
 548         return NULL;
 549 }
 550
 551 /*
 552  * Create struct lttng_event if it is missing and present in the list of
 553  * tracepoint probes.
 554  */
 555 static
 556 void lttng_create_event_if_missing(struct lttng_enabler *enabler)
 557 {
 558         struct lttng_session *session = enabler->chan->session;
 559         struct lttng_probe_desc *probe_desc;
 560         const struct lttng_event_desc *desc;
 561         struct lttng_event *event;
 562         int i;
 563         struct cds_list_head *probe_list;
 564
 565         probe_list = lttng_get_probe_list_head();
 566         /*
 567          * For each probe event, if we find that a probe event matches
 568          * our enabler, create an associated lttng_event if not
 569          * already present.
 570          */
 571         cds_list_for_each_entry(probe_desc, probe_list, head) {
 572                 for (i = 0; i < probe_desc->nr_events; i++) {
 573                         int found = 0, ret;
 574                         struct cds_hlist_head *head;
 575                         struct cds_hlist_node *node;
 576                         const char *event_name;
 577                         size_t name_len;
 578                         uint32_t hash;
 579
 580                         desc = probe_desc->event_desc[i];
 581                         if (!lttng_desc_match_enabler(desc, enabler))
 582                                 continue;
 583                         event_name = desc->name;
 584                         name_len = strlen(event_name);
 585
 586                         /*
 587                          * Check if already created.
 588                          */
 589                         hash = jhash(event_name, name_len, 0);
 590                         head = &session->events_ht.table[hash & (LTTNG_UST_EVENT_HT_SIZE - 1)];
 591                         cds_hlist_for_each_entry(event, node, head, hlist) {
 592                                 if (event->desc == desc
 593                                                 && event->chan == enabler->chan)
 594                                         found = 1;
 595                         }
 596                         if (found)
 597                                 continue;
 598
 599                         /*
 600                          * We need to create an event for this
 601                          * event probe.
 602                          */
 603                         ret = lttng_event_create(probe_desc->event_desc[i],
 604                                         enabler->chan);
 605                         if (ret) {
 606                                 DBG("Unable to create event %s, error %d\n",
 607                                         probe_desc->event_desc[i]->name, ret);
 608                         }
 609                 }
 610         }
 611 }
 612
 613 /*
 614  * Create events associated with an enabler (if not already present),
 615  * and add backward reference from the event to the enabler.
 616  */
 617 static
 618 int lttng_enabler_ref_events(struct lttng_enabler *enabler)
 619 {
 620         struct lttng_session *session = enabler->chan->session;
 621         struct lttng_event *event;
 622
 623         /* First ensure that probe events are created for this enabler. */
 624         lttng_create_event_if_missing(enabler);
 625
 626         /* For each event matching enabler in session event list. */
 627         cds_list_for_each_entry(event, &session->events_head, node) {
 628                 struct lttng_enabler_ref *enabler_ref;
 629
 630                 if (!lttng_event_match_enabler(event, enabler))
 631                         continue;
 632
 633                 enabler_ref = lttng_event_enabler_ref(event, enabler);
 634                 if (!enabler_ref) {
 635                         /*
 636                          * If no backward ref, create it.
 637                          * Add backward ref from event to enabler.
 638                          */
 639                         enabler_ref = zmalloc(sizeof(*enabler_ref));
 640                         if (!enabler_ref)
 641                                 return -ENOMEM;
 642                         enabler_ref->ref = enabler;
 643                         cds_list_add(&enabler_ref->node,
 644                                 &event->enablers_ref_head);
 645                 }
 646
 647                 /*
 648                  * Link filter bytecodes if not linked yet.
 649                  */
 650                 lttng_enabler_event_link_bytecode(event, enabler);
 651
 652                 /* TODO: merge event context. */
 653         }
 654         return 0;
 655 }
 656
 657 /*
 658  * Called at library load: connect the probe on all enablers matching
 659  * this event.
 660  * Called with session mutex held.
 661  */
 662 int lttng_fix_pending_events(void)
 663 {
 664         struct lttng_session *session;
 665
 666         cds_list_for_each_entry(session, &sessions, node) {
 667                 lttng_session_lazy_sync_enablers(session);
 668         }
 669         return 0;
 670 }
 671
 672 /*
 673  * For each session of the owner thread, execute pending statedump.
 674  * Only dump state for the sessions owned by the caller thread, because
 675  * we don't keep ust_lock across the entire iteration.
 676  */
 677 void lttng_handle_pending_statedump(void *owner)
 678 {
 679         struct lttng_session *session;
 680
 681         /* Execute state dump */
 682         lttng_ust_baddr_statedump(owner);
 683
 684         /* Clear pending state dump */
 685         if (ust_lock()) {
 686                 goto end;
 687         }
 688         cds_list_for_each_entry(session, &sessions, node) {
 689                 if (session->owner != owner)
 690                         continue;
 691                 if (!session->statedump_pending)
 692                         continue;
 693                 session->statedump_pending = 0;
 694         }
 695 end:
 696         ust_unlock();
 697         return;
 698 }
 699
 700 /*
 701  * Only used internally at session destruction.
 702  */
 703 static
 704 void _lttng_event_destroy(struct lttng_event *event)
 705 {
 706         struct lttng_enabler_ref *enabler_ref, *tmp_enabler_ref;
 707
 708         cds_list_del(&event->node);
 709         lttng_destroy_context(event->ctx);
 710         lttng_free_event_filter_runtime(event);
 711         /* Free event enabler refs */
 712         cds_list_for_each_entry_safe(enabler_ref, tmp_enabler_ref,
 713                         &event->enablers_ref_head, node)
 714                 free(enabler_ref);
 715         free(event);
 716 }
 717
 718 void lttng_ust_events_exit(void)
 719 {
 720         struct lttng_session *session, *tmpsession;
 721
 722         cds_list_for_each_entry_safe(session, tmpsession, &sessions, node)
 723                 lttng_session_destroy(session);
 724 }
 725
 726 /*
 727  * Enabler management.
 728  */
 729 struct lttng_enabler *lttng_enabler_create(enum lttng_enabler_type type,
 730                 struct lttng_ust_event *event_param,
 731                 struct lttng_channel *chan)
 732 {
 733         struct lttng_enabler *enabler;
 734
 735         enabler = zmalloc(sizeof(*enabler));
 736         if (!enabler)
 737                 return NULL;
 738         enabler->type = type;
 739         CDS_INIT_LIST_HEAD(&enabler->filter_bytecode_head);
 740         CDS_INIT_LIST_HEAD(&enabler->excluder_head);
 741         memcpy(&enabler->event_param, event_param,
 742                 sizeof(enabler->event_param));
 743         enabler->chan = chan;
 744         /* ctx left NULL */
 745         enabler->enabled = 1;
 746         cds_list_add(&enabler->node, &enabler->chan->session->enablers_head);
 747         lttng_session_lazy_sync_enablers(enabler->chan->session);
 748         return enabler;
 749 }
 750
 751 int lttng_enabler_enable(struct lttng_enabler *enabler)
 752 {
 753         enabler->enabled = 1;
 754         lttng_session_lazy_sync_enablers(enabler->chan->session);
 755         return 0;
 756 }
 757
 758 int lttng_enabler_disable(struct lttng_enabler *enabler)
 759 {
 760         enabler->enabled = 0;
 761         lttng_session_lazy_sync_enablers(enabler->chan->session);
 762         return 0;
 763 }
 764
 765 int lttng_enabler_attach_bytecode(struct lttng_enabler *enabler,
 766                 struct lttng_ust_filter_bytecode_node *bytecode)
 767 {
 768         bytecode->enabler = enabler;
 769         cds_list_add_tail(&bytecode->node, &enabler->filter_bytecode_head);
 770         lttng_session_lazy_sync_enablers(enabler->chan->session);
 771         return 0;
 772 }
 773
 774 int lttng_enabler_attach_exclusion(struct lttng_enabler *enabler,
 775                 struct lttng_ust_excluder_node *excluder)
 776 {
 777         excluder->enabler = enabler;
 778         cds_list_add_tail(&excluder->node, &enabler->excluder_head);
 779         lttng_session_lazy_sync_enablers(enabler->chan->session);
 780         return 0;
 781 }
 782
 783 int lttng_attach_context(struct lttng_ust_context *context_param,
 784                 struct lttng_ctx **ctx, struct lttng_session *session)
 785 {
 786         /*
 787          * We cannot attach a context after trace has been started for a
 788          * session because the metadata does not allow expressing this
 789          * information outside of the original channel scope.
 790          */
 791         if (session->been_active)
 792                 return -EPERM;
 793
 794         switch (context_param->ctx) {
 795         case LTTNG_UST_CONTEXT_PTHREAD_ID:
 796                 return lttng_add_pthread_id_to_ctx(ctx);
 797         case LTTNG_UST_CONTEXT_VTID:
 798                 return lttng_add_vtid_to_ctx(ctx);
 799         case LTTNG_UST_CONTEXT_VPID:
 800                 return lttng_add_vpid_to_ctx(ctx);
 801         case LTTNG_UST_CONTEXT_PROCNAME:
 802                 return lttng_add_procname_to_ctx(ctx);
 803         case LTTNG_UST_CONTEXT_IP:
 804                 return lttng_add_ip_to_ctx(ctx);
 805         default:
 806                 return -EINVAL;
 807         }
 808 }
 809
 810 int lttng_enabler_attach_context(struct lttng_enabler *enabler,
 811                 struct lttng_ust_context *context_param)
 812 {
 813 #if 0   // disabled for now.
 814         struct lttng_session *session = enabler->chan->session;
 815         int ret;
 816
 817         ret = lttng_attach_context(context_param, &enabler->ctx,
 818                         session);
 819         if (ret)
 820                 return ret;
 821         lttng_session_lazy_sync_enablers(enabler->chan->session);
 822 #endif
 823         return -ENOSYS;
 824 }
 825
 826 static
 827 void lttng_enabler_destroy(struct lttng_enabler *enabler)
 828 {
 829         struct lttng_ust_filter_bytecode_node *filter_node, *tmp_filter_node;
 830         struct lttng_ust_excluder_node *excluder_node, *tmp_excluder_node;
 831
 832         /* Destroy filter bytecode */
 833         cds_list_for_each_entry_safe(filter_node, tmp_filter_node,
 834                         &enabler->filter_bytecode_head, node) {
 835                 free(filter_node);
 836         }
 837
 838         /* Destroy excluders */
 839         cds_list_for_each_entry_safe(excluder_node, tmp_excluder_node,
 840                         &enabler->excluder_head, node) {
 841                 free(excluder_node);
 842         }
 843
 844         /* Destroy contexts */
 845         lttng_destroy_context(enabler->ctx);
 846
 847         cds_list_del(&enabler->node);
 848         free(enabler);
 849 }
 850
 851 /*
 852  * lttng_session_sync_enablers should be called just before starting a
 853  * session.
 854  */
 855 static
 856 void lttng_session_sync_enablers(struct lttng_session *session)
 857 {
 858         struct lttng_enabler *enabler;
 859         struct lttng_event *event;
 860
 861         cds_list_for_each_entry(enabler, &session->enablers_head, node)
 862                 lttng_enabler_ref_events(enabler);
 863         /*
 864          * For each event, if at least one of its enablers is enabled,
 865          * and its channel and session transient states are enabled, we
 866          * enable the event, else we disable it.
 867          */
 868         cds_list_for_each_entry(event, &session->events_head, node) {
 869                 struct lttng_enabler_ref *enabler_ref;
 870                 struct lttng_bytecode_runtime *runtime;
 871                 int enabled = 0, has_enablers_without_bytecode = 0;
 872
 873                 /* Enable events */
 874                 cds_list_for_each_entry(enabler_ref,
 875                                 &event->enablers_ref_head, node) {
 876                         if (enabler_ref->ref->enabled) {
 877                                 enabled = 1;
 878                                 break;
 879                         }
 880                 }
 881                 /*
 882                  * Enabled state is based on union of enablers, with
 883                  * intesection of session and channel transient enable
 884                  * states.
 885                  */
 886                 enabled = enabled && session->tstate && event->chan->tstate;
 887
 888                 CMM_STORE_SHARED(event->enabled, enabled);
 889                 /*
 890                  * Sync tracepoint registration with event enabled
 891                  * state.
 892                  */
 893                 if (enabled) {
 894                         if (!event->registered)
 895                                 register_event(event);
 896                 } else {
 897                         if (event->registered)
 898                                 unregister_event(event);
 899                 }
 900
 901                 /* Check if has enablers without bytecode enabled */
 902                 cds_list_for_each_entry(enabler_ref,
 903                                 &event->enablers_ref_head, node) {
 904                         if (enabler_ref->ref->enabled
 905                                         && cds_list_empty(&enabler_ref->ref->filter_bytecode_head)) {
 906                                 has_enablers_without_bytecode = 1;
 907                                 break;
 908                         }
 909                 }
 910                 event->has_enablers_without_bytecode =
 911                         has_enablers_without_bytecode;
 912
 913                 /* Enable filters */
 914                 cds_list_for_each_entry(runtime,
 915                                 &event->bytecode_runtime_head, node) {
 916                         lttng_filter_sync_state(runtime);
 917                 }
 918         }
 919 }
 920
 921 /*
 922  * Apply enablers to session events, adding events to session if need
 923  * be. It is required after each modification applied to an active
 924  * session, and right before session "start".
 925  * "lazy" sync means we only sync if required.
 926  */
 927 static
 928 void lttng_session_lazy_sync_enablers(struct lttng_session *session)
 929 {
 930         /* We can skip if session is not active */
 931         if (!session->active)
 932                 return;
 933         lttng_session_sync_enablers(session);
 934 }