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 (!has_loglevel)
 104                 loglevel = TRACE_DEFAULT;
 105         switch (req_type) {
 106         case LTTNG_UST_LOGLEVEL_RANGE:
 107                 if (loglevel <= req_loglevel || req_loglevel == -1)
 108                         return 1;
 109                 else
 110                         return 0;
 111         case LTTNG_UST_LOGLEVEL_SINGLE:
 112                 if (loglevel == req_loglevel || req_loglevel == -1)
 113                         return 1;
 114                 else
 115                         return 0;
 116         case LTTNG_UST_LOGLEVEL_ALL:
 117         default:
 118                 return 1;
 119         }
 120 }
 121
 122 void synchronize_trace(void)
 123 {
 124         synchronize_rcu();
 125 }
 126
 127 struct lttng_session *lttng_session_create(void)
 128 {
 129         struct lttng_session *session;
 130         int i;
 131
 132         session = zmalloc(sizeof(struct lttng_session));
 133         if (!session)
 134                 return NULL;
 135         CDS_INIT_LIST_HEAD(&session->chan_head);
 136         CDS_INIT_LIST_HEAD(&session->events_head);
 137         CDS_INIT_LIST_HEAD(&session->enablers_head);
 138         for (i = 0; i < LTTNG_UST_EVENT_HT_SIZE; i++)
 139                 CDS_INIT_HLIST_HEAD(&session->events_ht.table[i]);
 140         cds_list_add(&session->node, &sessions);
 141         return session;
 142 }
 143
 144 /*
 145  * Only used internally at session destruction.
 146  */
 147 static
 148 void _lttng_channel_unmap(struct lttng_channel *lttng_chan)
 149 {
 150         struct channel *chan;
 151         struct lttng_ust_shm_handle *handle;
 152
 153         cds_list_del(&lttng_chan->node);
 154         lttng_destroy_context(lttng_chan->ctx);
 155         chan = lttng_chan->chan;
 156         handle = lttng_chan->handle;
 157         /*
 158          * note: lttng_chan is private data contained within handle. It
 159          * will be freed along with the handle.
 160          */
 161         channel_destroy(chan, handle, 0);
 162 }
 163
 164 static
 165 void register_event(struct lttng_event *event)
 166 {
 167         int ret;
 168         const struct lttng_event_desc *desc;
 169
 170         assert(event->registered == 0);
 171         desc = event->desc;
 172         ret = __tracepoint_probe_register(desc->name,
 173                         desc->probe_callback,
 174                         event, desc->signature);
 175         WARN_ON_ONCE(ret);
 176         if (!ret)
 177                 event->registered = 1;
 178 }
 179
 180 static
 181 void unregister_event(struct lttng_event *event)
 182 {
 183         int ret;
 184         const struct lttng_event_desc *desc;
 185
 186         assert(event->registered == 1);
 187         desc = event->desc;
 188         ret = __tracepoint_probe_unregister(desc->name,
 189                         desc->probe_callback,
 190                         event);
 191         WARN_ON_ONCE(ret);
 192         if (!ret)
 193                 event->registered = 0;
 194 }
 195
 196 /*
 197  * Only used internally at session destruction.
 198  */
 199 static
 200 void _lttng_event_unregister(struct lttng_event *event)
 201 {
 202         if (event->registered)
 203                 unregister_event(event);
 204 }
 205
 206 void lttng_session_destroy(struct lttng_session *session)
 207 {
 208         struct lttng_channel *chan, *tmpchan;
 209         struct lttng_event *event, *tmpevent;
 210         struct lttng_enabler *enabler, *tmpenabler;
 211
 212         CMM_ACCESS_ONCE(session->active) = 0;
 213         cds_list_for_each_entry(event, &session->events_head, node) {
 214                 _lttng_event_unregister(event);
 215         }
 216         synchronize_trace();    /* Wait for in-flight events to complete */
 217         cds_list_for_each_entry_safe(enabler, tmpenabler,
 218                         &session->enablers_head, node)
 219                 lttng_enabler_destroy(enabler);
 220         cds_list_for_each_entry_safe(event, tmpevent,
 221                         &session->events_head, node)
 222                 _lttng_event_destroy(event);
 223         cds_list_for_each_entry_safe(chan, tmpchan, &session->chan_head, node)
 224                 _lttng_channel_unmap(chan);
 225         cds_list_del(&session->node);
 226         free(session);
 227 }
 228
 229 int lttng_session_enable(struct lttng_session *session)
 230 {
 231         int ret = 0;
 232         struct lttng_channel *chan;
 233         int notify_socket;
 234
 235         if (session->active) {
 236                 ret = -EBUSY;
 237                 goto end;
 238         }
 239
 240         notify_socket = lttng_get_notify_socket(session->owner);
 241         if (notify_socket < 0)
 242                 return notify_socket;
 243
 244         /* Set transient enabler state to "enabled" */
 245         session->tstate = 1;
 246
 247         /*
 248          * Snapshot the number of events per channel to know the type of header
 249          * we need to use.
 250          */
 251         cds_list_for_each_entry(chan, &session->chan_head, node) {
 252                 const struct lttng_ctx *ctx;
 253                 const struct lttng_ctx_field *fields = NULL;
 254                 size_t nr_fields = 0;
 255                 uint32_t chan_id;
 256
 257                 /* don't change it if session stop/restart */
 258                 if (chan->header_type)
 259                         continue;
 260                 ctx = chan->ctx;
 261                 if (ctx) {
 262                         nr_fields = ctx->nr_fields;
 263                         fields = ctx->fields;
 264                 }
 265                 ret = ustcomm_register_channel(notify_socket,
 266                         session->objd,
 267                         chan->objd,
 268                         nr_fields,
 269                         fields,
 270                         &chan_id,
 271                         &chan->header_type);
 272                 if (ret) {
 273                         DBG("Error (%d) registering channel to sessiond", ret);
 274                         return ret;
 275                 }
 276                 if (chan_id != chan->id) {
 277                         DBG("Error: channel registration id (%u) does not match id assigned at creation (%u)",
 278                                 chan_id, chan->id);
 279                         return -EINVAL;
 280                 }
 281         }
 282
 283         /* We need to sync enablers with session before activation. */
 284         lttng_session_sync_enablers(session);
 285
 286         /* Set atomically the state to "active" */
 287         CMM_ACCESS_ONCE(session->active) = 1;
 288         CMM_ACCESS_ONCE(session->been_active) = 1;
 289
 290         session->statedump_pending = 1;
 291         lttng_ust_sockinfo_session_enabled(session->owner);
 292 end:
 293         return ret;
 294 }
 295
 296 int lttng_session_disable(struct lttng_session *session)
 297 {
 298         int ret = 0;
 299
 300         if (!session->active) {
 301                 ret = -EBUSY;
 302                 goto end;
 303         }
 304         /* Set atomically the state to "inactive" */
 305         CMM_ACCESS_ONCE(session->active) = 0;
 306
 307         /* Set transient enabler state to "disabled" */
 308         session->tstate = 0;
 309         lttng_session_sync_enablers(session);
 310 end:
 311         return ret;
 312 }
 313
 314 int lttng_channel_enable(struct lttng_channel *channel)
 315 {
 316         int ret = 0;
 317
 318         if (channel->enabled) {
 319                 ret = -EBUSY;
 320                 goto end;
 321         }
 322         /* Set transient enabler state to "enabled" */
 323         channel->tstate = 1;
 324         lttng_session_sync_enablers(channel->session);
 325         /* Set atomically the state to "enabled" */
 326         CMM_ACCESS_ONCE(channel->enabled) = 1;
 327 end:
 328         return ret;
 329 }
 330
 331 int lttng_channel_disable(struct lttng_channel *channel)
 332 {
 333         int ret = 0;
 334
 335         if (!channel->enabled) {
 336                 ret = -EBUSY;
 337                 goto end;
 338         }
 339         /* Set atomically the state to "disabled" */
 340         CMM_ACCESS_ONCE(channel->enabled) = 0;
 341         /* Set transient enabler state to "enabled" */
 342         channel->tstate = 0;
 343         lttng_session_sync_enablers(channel->session);
 344 end:
 345         return ret;
 346 }
 347
 348 /*
 349  * Supports event creation while tracing session is active.
 350  */
 351 static
 352 int lttng_event_create(const struct lttng_event_desc *desc,
 353                 struct lttng_channel *chan)
 354 {
 355         const char *event_name = desc->name;
 356         struct lttng_event *event;
 357         struct lttng_session *session = chan->session;
 358         struct cds_hlist_head *head;
 359         struct cds_hlist_node *node;
 360         int ret = 0;
 361         size_t name_len = strlen(event_name);
 362         uint32_t hash;
 363         int notify_socket, loglevel;
 364         const char *uri;
 365
 366         hash = jhash(event_name, name_len, 0);
 367         head = &chan->session->events_ht.table[hash & (LTTNG_UST_EVENT_HT_SIZE - 1)];
 368         cds_hlist_for_each_entry(event, node, head, hlist) {
 369                 assert(event->desc);
 370                 if (!strncmp(event->desc->name, desc->name,
 371                                         LTTNG_UST_SYM_NAME_LEN - 1)
 372                                 && chan == event->chan) {
 373                         ret = -EEXIST;
 374                         goto exist;
 375                 }
 376         }
 377
 378         notify_socket = lttng_get_notify_socket(session->owner);
 379         if (notify_socket < 0) {
 380                 ret = notify_socket;
 381                 goto socket_error;
 382         }
 383
 384         /*
 385          * Check if loglevel match. Refuse to connect event if not.
 386          */
 387         event = zmalloc(sizeof(struct lttng_event));
 388         if (!event) {
 389                 ret = -ENOMEM;
 390                 goto cache_error;
 391         }
 392         event->chan = chan;
 393
 394         /* Event will be enabled by enabler sync. */
 395         event->enabled = 0;
 396         event->registered = 0;
 397         CDS_INIT_LIST_HEAD(&event->bytecode_runtime_head);
 398         CDS_INIT_LIST_HEAD(&event->enablers_ref_head);
 399         event->desc = desc;
 400
 401         if (desc->loglevel)
 402                 loglevel = *(*event->desc->loglevel);
 403         else
 404                 loglevel = TRACE_DEFAULT;
 405         if (desc->u.ext.model_emf_uri)
 406                 uri = *(desc->u.ext.model_emf_uri);
 407         else
 408                 uri = NULL;
 409
 410         /* Fetch event ID from sessiond */
 411         ret = ustcomm_register_event(notify_socket,
 412                 session->objd,
 413                 chan->objd,
 414                 event_name,
 415                 loglevel,
 416                 desc->signature,
 417                 desc->nr_fields,
 418                 desc->fields,
 419                 uri,
 420                 &event->id);
 421         if (ret < 0) {
 422                 DBG("Error (%d) registering event to sessiond", ret);
 423                 goto sessiond_register_error;
 424         }
 425
 426         /* Populate lttng_event structure before tracepoint registration. */
 427         cmm_smp_wmb();
 428         cds_list_add(&event->node, &chan->session->events_head);
 429         cds_hlist_add_head(&event->hlist, head);
 430         return 0;
 431
 432 sessiond_register_error:
 433         free(event);
 434 cache_error:
 435 socket_error:
 436 exist:
 437         return ret;
 438 }
 439
 440 static
 441 int lttng_desc_match_wildcard_enabler(const struct lttng_event_desc *desc,
 442                 struct lttng_enabler *enabler)
 443 {
 444         int loglevel = 0;
 445         unsigned int has_loglevel = 0;
 446
 447         assert(enabler->type == LTTNG_ENABLER_WILDCARD);
 448         /* Compare excluding final '*' */
 449         if (strncmp(desc->name, enabler->event_param.name,
 450                         strlen(enabler->event_param.name) - 1))
 451                 return 0;
 452         if (desc->loglevel) {
 453                 loglevel = *(*desc->loglevel);
 454                 has_loglevel = 1;
 455         }
 456         if (!lttng_loglevel_match(loglevel,
 457                         has_loglevel,
 458                         enabler->event_param.loglevel_type,
 459                         enabler->event_param.loglevel))
 460                 return 0;
 461         return 1;
 462 }
 463
 464 static
 465 int lttng_desc_match_event_enabler(const struct lttng_event_desc *desc,
 466                 struct lttng_enabler *enabler)
 467 {
 468         int loglevel = 0;
 469         unsigned int has_loglevel = 0;
 470
 471         assert(enabler->type == LTTNG_ENABLER_EVENT);
 472         if (strcmp(desc->name, enabler->event_param.name))
 473                 return 0;
 474         if (desc->loglevel) {
 475                 loglevel = *(*desc->loglevel);
 476                 has_loglevel = 1;
 477         }
 478         if (!lttng_loglevel_match(loglevel,
 479                         has_loglevel,
 480                         enabler->event_param.loglevel_type,
 481                         enabler->event_param.loglevel))
 482                 return 0;
 483         return 1;
 484 }
 485
 486 static
 487 int lttng_desc_match_enabler(const struct lttng_event_desc *desc,
 488                 struct lttng_enabler *enabler)
 489 {
 490         struct lttng_ust_excluder_node *excluder;
 491
 492         /* If event matches with an excluder, return 'does not match' */
 493         cds_list_for_each_entry(excluder, &enabler->excluder_head, node) {
 494                 int count;
 495
 496                 for (count = 0; count < excluder->excluder.count; count++) {
 497                         int found, len;
 498                         char *excluder_name;
 499
 500                         excluder_name = (char *) (excluder->excluder.names)
 501                                         + count * LTTNG_UST_SYM_NAME_LEN;
 502                         len = strnlen(excluder_name, LTTNG_UST_SYM_NAME_LEN);
 503                         if (len > 0 && excluder_name[len - 1] == '*') {
 504                                 found = !strncmp(desc->name, excluder_name,
 505                                                 len - 1);
 506                         } else {
 507                                 found = !strncmp(desc->name, excluder_name,
 508                                                 LTTNG_UST_SYM_NAME_LEN - 1);
 509                         }
 510                         if (found) {
 511                                 return 0;
 512                         }
 513                 }
 514         }
 515         switch (enabler->type) {
 516         case LTTNG_ENABLER_WILDCARD:
 517                 return lttng_desc_match_wildcard_enabler(desc, enabler);
 518         case LTTNG_ENABLER_EVENT:
 519                 return lttng_desc_match_event_enabler(desc, enabler);
 520         default:
 521                 return -EINVAL;
 522         }
 523 }
 524
 525 static
 526 int lttng_event_match_enabler(struct lttng_event *event,
 527                 struct lttng_enabler *enabler)
 528 {
 529         if (lttng_desc_match_enabler(event->desc, enabler)
 530                         && event->chan == enabler->chan)
 531                 return 1;
 532         else
 533                 return 0;
 534 }
 535
 536 static
 537 struct lttng_enabler_ref * lttng_event_enabler_ref(struct lttng_event *event,
 538                 struct lttng_enabler *enabler)
 539 {
 540         struct lttng_enabler_ref *enabler_ref;
 541
 542         cds_list_for_each_entry(enabler_ref,
 543                         &event->enablers_ref_head, node) {
 544                 if (enabler_ref->ref == enabler)
 545                         return enabler_ref;
 546         }
 547         return NULL;
 548 }
 549
 550 /*
 551  * Create struct lttng_event if it is missing and present in the list of
 552  * tracepoint probes.
 553  */
 554 static
 555 void lttng_create_event_if_missing(struct lttng_enabler *enabler)
 556 {
 557         struct lttng_session *session = enabler->chan->session;
 558         struct lttng_probe_desc *probe_desc;
 559         const struct lttng_event_desc *desc;
 560         struct lttng_event *event;
 561         int i;
 562         struct cds_list_head *probe_list;
 563
 564         probe_list = lttng_get_probe_list_head();
 565         /*
 566          * For each probe event, if we find that a probe event matches
 567          * our enabler, create an associated lttng_event if not
 568          * already present.
 569          */
 570         cds_list_for_each_entry(probe_desc, probe_list, head) {
 571                 for (i = 0; i < probe_desc->nr_events; i++) {
 572                         int found = 0, ret;
 573                         struct cds_hlist_head *head;
 574                         struct cds_hlist_node *node;
 575                         const char *event_name;
 576                         size_t name_len;
 577                         uint32_t hash;
 578
 579                         desc = probe_desc->event_desc[i];
 580                         if (!lttng_desc_match_enabler(desc, enabler))
 581                                 continue;
 582                         event_name = desc->name;
 583                         name_len = strlen(event_name);
 584
 585                         /*
 586                          * Check if already created.
 587                          */
 588                         hash = jhash(event_name, name_len, 0);
 589                         head = &session->events_ht.table[hash & (LTTNG_UST_EVENT_HT_SIZE - 1)];
 590                         cds_hlist_for_each_entry(event, node, head, hlist) {
 591                                 if (event->desc == desc
 592                                                 && event->chan == enabler->chan)
 593                                         found = 1;
 594                         }
 595                         if (found)
 596                                 continue;
 597
 598                         /*
 599                          * We need to create an event for this
 600                          * event probe.
 601                          */
 602                         ret = lttng_event_create(probe_desc->event_desc[i],
 603                                         enabler->chan);
 604                         if (ret) {
 605                                 DBG("Unable to create event %s, error %d\n",
 606                                         probe_desc->event_desc[i]->name, ret);
 607                         }
 608                 }
 609         }
 610 }
 611
 612 /*
 613  * Create events associated with an enabler (if not already present),
 614  * and add backward reference from the event to the enabler.
 615  */
 616 static
 617 int lttng_enabler_ref_events(struct lttng_enabler *enabler)
 618 {
 619         struct lttng_session *session = enabler->chan->session;
 620         struct lttng_event *event;
 621
 622         /* First ensure that probe events are created for this enabler. */
 623         lttng_create_event_if_missing(enabler);
 624
 625         /* For each event matching enabler in session event list. */
 626         cds_list_for_each_entry(event, &session->events_head, node) {
 627                 struct lttng_enabler_ref *enabler_ref;
 628
 629                 if (!lttng_event_match_enabler(event, enabler))
 630                         continue;
 631
 632                 enabler_ref = lttng_event_enabler_ref(event, enabler);
 633                 if (!enabler_ref) {
 634                         /*
 635                          * If no backward ref, create it.
 636                          * Add backward ref from event to enabler.
 637                          */
 638                         enabler_ref = zmalloc(sizeof(*enabler_ref));
 639                         if (!enabler_ref)
 640                                 return -ENOMEM;
 641                         enabler_ref->ref = enabler;
 642                         cds_list_add(&enabler_ref->node,
 643                                 &event->enablers_ref_head);
 644                 }
 645
 646                 /*
 647                  * Link filter bytecodes if not linked yet.
 648                  */
 649                 lttng_enabler_event_link_bytecode(event, enabler);
 650
 651                 /* TODO: merge event context. */
 652         }
 653         return 0;
 654 }
 655
 656 /*
 657  * Called at library load: connect the probe on all enablers matching
 658  * this event.
 659  * Called with session mutex held.
 660  */
 661 int lttng_fix_pending_events(void)
 662 {
 663         struct lttng_session *session;
 664
 665         cds_list_for_each_entry(session, &sessions, node) {
 666                 lttng_session_lazy_sync_enablers(session);
 667         }
 668         return 0;
 669 }
 670
 671 /*
 672  * For each session of the owner thread, execute pending statedump.
 673  * Only dump state for the sessions owned by the caller thread, because
 674  * we don't keep ust_lock across the entire iteration.
 675  */
 676 void lttng_handle_pending_statedump(void *owner)
 677 {
 678         struct lttng_session *session;
 679
 680         /* Execute state dump */
 681         lttng_ust_baddr_statedump(owner);
 682
 683         /* Clear pending state dump */
 684         if (ust_lock()) {
 685                 goto end;
 686         }
 687         cds_list_for_each_entry(session, &sessions, node) {
 688                 if (session->owner != owner)
 689                         continue;
 690                 if (!session->statedump_pending)
 691                         continue;
 692                 session->statedump_pending = 0;
 693         }
 694 end:
 695         ust_unlock();
 696         return;
 697 }
 698
 699 /*
 700  * Only used internally at session destruction.
 701  */
 702 static
 703 void _lttng_event_destroy(struct lttng_event *event)
 704 {
 705         struct lttng_enabler_ref *enabler_ref, *tmp_enabler_ref;
 706
 707         cds_list_del(&event->node);
 708         lttng_destroy_context(event->ctx);
 709         lttng_free_event_filter_runtime(event);
 710         /* Free event enabler refs */
 711         cds_list_for_each_entry_safe(enabler_ref, tmp_enabler_ref,
 712                         &event->enablers_ref_head, node)
 713                 free(enabler_ref);
 714         free(event);
 715 }
 716
 717 void lttng_ust_events_exit(void)
 718 {
 719         struct lttng_session *session, *tmpsession;
 720
 721         cds_list_for_each_entry_safe(session, tmpsession, &sessions, node)
 722                 lttng_session_destroy(session);
 723 }
 724
 725 /*
 726  * Enabler management.
 727  */
 728 struct lttng_enabler *lttng_enabler_create(enum lttng_enabler_type type,
 729                 struct lttng_ust_event *event_param,
 730                 struct lttng_channel *chan)
 731 {
 732         struct lttng_enabler *enabler;
 733
 734         enabler = zmalloc(sizeof(*enabler));
 735         if (!enabler)
 736                 return NULL;
 737         enabler->type = type;
 738         CDS_INIT_LIST_HEAD(&enabler->filter_bytecode_head);
 739         CDS_INIT_LIST_HEAD(&enabler->excluder_head);
 740         memcpy(&enabler->event_param, event_param,
 741                 sizeof(enabler->event_param));
 742         enabler->chan = chan;
 743         /* ctx left NULL */
 744         /*
 745          * The "disable" event create comm field has been added to fix a
 746          * race between event creation (of a started trace) and enabling
 747          * filtering. New session daemon always set the "disable" field
 748          * to 1, and are aware that they need to explicitly enable the
 749          * event. Older session daemon (within same ABI) leave it at 0,
 750          * and therefore we need to enable it here, keeping the original
 751          * racy behavior.
 752          */
 753         enabler->enabled = !event_param->disabled;
 754         cds_list_add(&enabler->node, &enabler->chan->session->enablers_head);
 755         lttng_session_lazy_sync_enablers(enabler->chan->session);
 756         return enabler;
 757 }
 758
 759 int lttng_enabler_enable(struct lttng_enabler *enabler)
 760 {
 761         enabler->enabled = 1;
 762         lttng_session_lazy_sync_enablers(enabler->chan->session);
 763         return 0;
 764 }
 765
 766 int lttng_enabler_disable(struct lttng_enabler *enabler)
 767 {
 768         enabler->enabled = 0;
 769         lttng_session_lazy_sync_enablers(enabler->chan->session);
 770         return 0;
 771 }
 772
 773 int lttng_enabler_attach_bytecode(struct lttng_enabler *enabler,
 774                 struct lttng_ust_filter_bytecode_node *bytecode)
 775 {
 776         bytecode->enabler = enabler;
 777         cds_list_add_tail(&bytecode->node, &enabler->filter_bytecode_head);
 778         lttng_session_lazy_sync_enablers(enabler->chan->session);
 779         return 0;
 780 }
 781
 782 int lttng_enabler_attach_exclusion(struct lttng_enabler *enabler,
 783                 struct lttng_ust_excluder_node *excluder)
 784 {
 785         excluder->enabler = enabler;
 786         cds_list_add_tail(&excluder->node, &enabler->excluder_head);
 787         lttng_session_lazy_sync_enablers(enabler->chan->session);
 788         return 0;
 789 }
 790
 791 int lttng_attach_context(struct lttng_ust_context *context_param,
 792                 struct lttng_ctx **ctx, struct lttng_session *session)
 793 {
 794         /*
 795          * We cannot attach a context after trace has been started for a
 796          * session because the metadata does not allow expressing this
 797          * information outside of the original channel scope.
 798          */
 799         if (session->been_active)
 800                 return -EPERM;
 801
 802         switch (context_param->ctx) {
 803         case LTTNG_UST_CONTEXT_PTHREAD_ID:
 804                 return lttng_add_pthread_id_to_ctx(ctx);
 805         case LTTNG_UST_CONTEXT_VTID:
 806                 return lttng_add_vtid_to_ctx(ctx);
 807         case LTTNG_UST_CONTEXT_VPID:
 808                 return lttng_add_vpid_to_ctx(ctx);
 809         case LTTNG_UST_CONTEXT_PROCNAME:
 810                 return lttng_add_procname_to_ctx(ctx);
 811         case LTTNG_UST_CONTEXT_IP:
 812                 return lttng_add_ip_to_ctx(ctx);
 813         default:
 814                 return -EINVAL;
 815         }
 816 }
 817
 818 int lttng_enabler_attach_context(struct lttng_enabler *enabler,
 819                 struct lttng_ust_context *context_param)
 820 {
 821 #if 0   // disabled for now.
 822         struct lttng_session *session = enabler->chan->session;
 823         int ret;
 824
 825         ret = lttng_attach_context(context_param, &enabler->ctx,
 826                         session);
 827         if (ret)
 828                 return ret;
 829         lttng_session_lazy_sync_enablers(enabler->chan->session);
 830 #endif
 831         return -ENOSYS;
 832 }
 833
 834 static
 835 void lttng_enabler_destroy(struct lttng_enabler *enabler)
 836 {
 837         struct lttng_ust_filter_bytecode_node *filter_node, *tmp_filter_node;
 838         struct lttng_ust_excluder_node *excluder_node, *tmp_excluder_node;
 839
 840         /* Destroy filter bytecode */
 841         cds_list_for_each_entry_safe(filter_node, tmp_filter_node,
 842                         &enabler->filter_bytecode_head, node) {
 843                 free(filter_node);
 844         }
 845
 846         /* Destroy excluders */
 847         cds_list_for_each_entry_safe(excluder_node, tmp_excluder_node,
 848                         &enabler->excluder_head, node) {
 849                 free(excluder_node);
 850         }
 851
 852         /* Destroy contexts */
 853         lttng_destroy_context(enabler->ctx);
 854
 855         cds_list_del(&enabler->node);
 856         free(enabler);
 857 }
 858
 859 /*
 860  * lttng_session_sync_enablers should be called just before starting a
 861  * session.
 862  */
 863 static
 864 void lttng_session_sync_enablers(struct lttng_session *session)
 865 {
 866         struct lttng_enabler *enabler;
 867         struct lttng_event *event;
 868
 869         cds_list_for_each_entry(enabler, &session->enablers_head, node)
 870                 lttng_enabler_ref_events(enabler);
 871         /*
 872          * For each event, if at least one of its enablers is enabled,
 873          * and its channel and session transient states are enabled, we
 874          * enable the event, else we disable it.
 875          */
 876         cds_list_for_each_entry(event, &session->events_head, node) {
 877                 struct lttng_enabler_ref *enabler_ref;
 878                 struct lttng_bytecode_runtime *runtime;
 879                 int enabled = 0, has_enablers_without_bytecode = 0;
 880
 881                 /* Enable events */
 882                 cds_list_for_each_entry(enabler_ref,
 883                                 &event->enablers_ref_head, node) {
 884                         if (enabler_ref->ref->enabled) {
 885                                 enabled = 1;
 886                                 break;
 887                         }
 888                 }
 889                 /*
 890                  * Enabled state is based on union of enablers, with
 891                  * intesection of session and channel transient enable
 892                  * states.
 893                  */
 894                 enabled = enabled && session->tstate && event->chan->tstate;
 895
 896                 CMM_STORE_SHARED(event->enabled, enabled);
 897                 /*
 898                  * Sync tracepoint registration with event enabled
 899                  * state.
 900                  */
 901                 if (enabled) {
 902                         if (!event->registered)
 903                                 register_event(event);
 904                 } else {
 905                         if (event->registered)
 906                                 unregister_event(event);
 907                 }
 908
 909                 /* Check if has enablers without bytecode enabled */
 910                 cds_list_for_each_entry(enabler_ref,
 911                                 &event->enablers_ref_head, node) {
 912                         if (enabler_ref->ref->enabled
 913                                         && cds_list_empty(&enabler_ref->ref->filter_bytecode_head)) {
 914                                 has_enablers_without_bytecode = 1;
 915                                 break;
 916                         }
 917                 }
 918                 event->has_enablers_without_bytecode =
 919                         has_enablers_without_bytecode;
 920
 921                 /* Enable filters */
 922                 cds_list_for_each_entry(runtime,
 923                                 &event->bytecode_runtime_head, node) {
 924                         lttng_filter_sync_state(runtime);
 925                 }
 926         }
 927 }
 928
 929 /*
 930  * Apply enablers to session events, adding events to session if need
 931  * be. It is required after each modification applied to an active
 932  * session, and right before session "start".
 933  * "lazy" sync means we only sync if required.
 934  */
 935 static
 936 void lttng_session_lazy_sync_enablers(struct lttng_session *session)
 937 {
 938         /* We can skip if session is not active */
 939         if (!session->active)
 940                 return;
 941         lttng_session_sync_enablers(session);
 942 }