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
 108                                 || (req_loglevel == -1 && loglevel <= TRACE_DEBUG))
 109                         return 1;
 110                 else
 111                         return 0;
 112         case LTTNG_UST_LOGLEVEL_SINGLE:
 113                 if (loglevel == req_loglevel
 114                                 || (req_loglevel == -1 && loglevel <= TRACE_DEBUG))
 115                         return 1;
 116                 else
 117                         return 0;
 118         case LTTNG_UST_LOGLEVEL_ALL:
 119         default:
 120                 if (loglevel <= TRACE_DEBUG)
 121                         return 1;
 122                 else
 123                         return 0;
 124         }
 125 }
 126
 127 void synchronize_trace(void)
 128 {
 129         synchronize_rcu();
 130 }
 131
 132 struct lttng_session *lttng_session_create(void)
 133 {
 134         struct lttng_session *session;
 135         int i;
 136
 137         session = zmalloc(sizeof(struct lttng_session));
 138         if (!session)
 139                 return NULL;
 140         CDS_INIT_LIST_HEAD(&session->chan_head);
 141         CDS_INIT_LIST_HEAD(&session->events_head);
 142         CDS_INIT_LIST_HEAD(&session->enablers_head);
 143         for (i = 0; i < LTTNG_UST_EVENT_HT_SIZE; i++)
 144                 CDS_INIT_HLIST_HEAD(&session->events_ht.table[i]);
 145         cds_list_add(&session->node, &sessions);
 146         return session;
 147 }
 148
 149 /*
 150  * Only used internally at session destruction.
 151  */
 152 static
 153 void _lttng_channel_unmap(struct lttng_channel *lttng_chan)
 154 {
 155         struct channel *chan;
 156         struct lttng_ust_shm_handle *handle;
 157
 158         cds_list_del(&lttng_chan->node);
 159         lttng_destroy_context(lttng_chan->ctx);
 160         chan = lttng_chan->chan;
 161         handle = lttng_chan->handle;
 162         /*
 163          * note: lttng_chan is private data contained within handle. It
 164          * will be freed along with the handle.
 165          */
 166         channel_destroy(chan, handle, 0);
 167 }
 168
 169 static
 170 void register_event(struct lttng_event *event)
 171 {
 172         int ret;
 173         const struct lttng_event_desc *desc;
 174
 175         assert(event->registered == 0);
 176         desc = event->desc;
 177         ret = __tracepoint_probe_register(desc->name,
 178                         desc->probe_callback,
 179                         event, desc->signature);
 180         WARN_ON_ONCE(ret);
 181         if (!ret)
 182                 event->registered = 1;
 183 }
 184
 185 static
 186 void unregister_event(struct lttng_event *event)
 187 {
 188         int ret;
 189         const struct lttng_event_desc *desc;
 190
 191         assert(event->registered == 1);
 192         desc = event->desc;
 193         ret = __tracepoint_probe_unregister(desc->name,
 194                         desc->probe_callback,
 195                         event);
 196         WARN_ON_ONCE(ret);
 197         if (!ret)
 198                 event->registered = 0;
 199 }
 200
 201 /*
 202  * Only used internally at session destruction.
 203  */
 204 static
 205 void _lttng_event_unregister(struct lttng_event *event)
 206 {
 207         if (event->registered)
 208                 unregister_event(event);
 209 }
 210
 211 void lttng_session_destroy(struct lttng_session *session)
 212 {
 213         struct lttng_channel *chan, *tmpchan;
 214         struct lttng_event *event, *tmpevent;
 215         struct lttng_enabler *enabler, *tmpenabler;
 216
 217         CMM_ACCESS_ONCE(session->active) = 0;
 218         cds_list_for_each_entry(event, &session->events_head, node) {
 219                 _lttng_event_unregister(event);
 220         }
 221         synchronize_trace();    /* Wait for in-flight events to complete */
 222         cds_list_for_each_entry_safe(enabler, tmpenabler,
 223                         &session->enablers_head, node)
 224                 lttng_enabler_destroy(enabler);
 225         cds_list_for_each_entry_safe(event, tmpevent,
 226                         &session->events_head, node)
 227                 _lttng_event_destroy(event);
 228         cds_list_for_each_entry_safe(chan, tmpchan, &session->chan_head, node)
 229                 _lttng_channel_unmap(chan);
 230         cds_list_del(&session->node);
 231         free(session);
 232 }
 233
 234 int lttng_session_enable(struct lttng_session *session)
 235 {
 236         int ret = 0;
 237         struct lttng_channel *chan;
 238         int notify_socket;
 239
 240         if (session->active) {
 241                 ret = -EBUSY;
 242                 goto end;
 243         }
 244
 245         notify_socket = lttng_get_notify_socket(session->owner);
 246         if (notify_socket < 0)
 247                 return notify_socket;
 248
 249         /* Set transient enabler state to "enabled" */
 250         session->tstate = 1;
 251
 252         /*
 253          * Snapshot the number of events per channel to know the type of header
 254          * we need to use.
 255          */
 256         cds_list_for_each_entry(chan, &session->chan_head, node) {
 257                 const struct lttng_ctx *ctx;
 258                 const struct lttng_ctx_field *fields = NULL;
 259                 size_t nr_fields = 0;
 260                 uint32_t chan_id;
 261
 262                 /* don't change it if session stop/restart */
 263                 if (chan->header_type)
 264                         continue;
 265                 ctx = chan->ctx;
 266                 if (ctx) {
 267                         nr_fields = ctx->nr_fields;
 268                         fields = ctx->fields;
 269                 }
 270                 ret = ustcomm_register_channel(notify_socket,
 271                         session->objd,
 272                         chan->objd,
 273                         nr_fields,
 274                         fields,
 275                         &chan_id,
 276                         &chan->header_type);
 277                 if (ret) {
 278                         DBG("Error (%d) registering channel to sessiond", ret);
 279                         return ret;
 280                 }
 281                 if (chan_id != chan->id) {
 282                         DBG("Error: channel registration id (%u) does not match id assigned at creation (%u)",
 283                                 chan_id, chan->id);
 284                         return -EINVAL;
 285                 }
 286         }
 287
 288         /* We need to sync enablers with session before activation. */
 289         lttng_session_sync_enablers(session);
 290
 291         /* Set atomically the state to "active" */
 292         CMM_ACCESS_ONCE(session->active) = 1;
 293         CMM_ACCESS_ONCE(session->been_active) = 1;
 294
 295         session->statedump_pending = 1;
 296         lttng_ust_sockinfo_session_enabled(session->owner);
 297 end:
 298         return ret;
 299 }
 300
 301 int lttng_session_disable(struct lttng_session *session)
 302 {
 303         int ret = 0;
 304
 305         if (!session->active) {
 306                 ret = -EBUSY;
 307                 goto end;
 308         }
 309         /* Set atomically the state to "inactive" */
 310         CMM_ACCESS_ONCE(session->active) = 0;
 311
 312         /* Set transient enabler state to "disabled" */
 313         session->tstate = 0;
 314         lttng_session_sync_enablers(session);
 315 end:
 316         return ret;
 317 }
 318
 319 int lttng_channel_enable(struct lttng_channel *channel)
 320 {
 321         int ret = 0;
 322
 323         if (channel->enabled) {
 324                 ret = -EBUSY;
 325                 goto end;
 326         }
 327         /* Set transient enabler state to "enabled" */
 328         channel->tstate = 1;
 329         lttng_session_sync_enablers(channel->session);
 330         /* Set atomically the state to "enabled" */
 331         CMM_ACCESS_ONCE(channel->enabled) = 1;
 332 end:
 333         return ret;
 334 }
 335
 336 int lttng_channel_disable(struct lttng_channel *channel)
 337 {
 338         int ret = 0;
 339
 340         if (!channel->enabled) {
 341                 ret = -EBUSY;
 342                 goto end;
 343         }
 344         /* Set atomically the state to "disabled" */
 345         CMM_ACCESS_ONCE(channel->enabled) = 0;
 346         /* Set transient enabler state to "enabled" */
 347         channel->tstate = 0;
 348         lttng_session_sync_enablers(channel->session);
 349 end:
 350         return ret;
 351 }
 352
 353 /*
 354  * Supports event creation while tracing session is active.
 355  */
 356 static
 357 int lttng_event_create(const struct lttng_event_desc *desc,
 358                 struct lttng_channel *chan)
 359 {
 360         const char *event_name = desc->name;
 361         struct lttng_event *event;
 362         struct lttng_session *session = chan->session;
 363         struct cds_hlist_head *head;
 364         struct cds_hlist_node *node;
 365         int ret = 0;
 366         size_t name_len = strlen(event_name);
 367         uint32_t hash;
 368         int notify_socket, loglevel;
 369         const char *uri;
 370
 371         hash = jhash(event_name, name_len, 0);
 372         head = &chan->session->events_ht.table[hash & (LTTNG_UST_EVENT_HT_SIZE - 1)];
 373         cds_hlist_for_each_entry(event, node, head, hlist) {
 374                 assert(event->desc);
 375                 if (!strncmp(event->desc->name, desc->name,
 376                                         LTTNG_UST_SYM_NAME_LEN - 1)
 377                                 && chan == event->chan) {
 378                         ret = -EEXIST;
 379                         goto exist;
 380                 }
 381         }
 382
 383         notify_socket = lttng_get_notify_socket(session->owner);
 384         if (notify_socket < 0) {
 385                 ret = notify_socket;
 386                 goto socket_error;
 387         }
 388
 389         /*
 390          * Check if loglevel match. Refuse to connect event if not.
 391          */
 392         event = zmalloc(sizeof(struct lttng_event));
 393         if (!event) {
 394                 ret = -ENOMEM;
 395                 goto cache_error;
 396         }
 397         event->chan = chan;
 398
 399         /* Event will be enabled by enabler sync. */
 400         event->enabled = 0;
 401         event->registered = 0;
 402         CDS_INIT_LIST_HEAD(&event->bytecode_runtime_head);
 403         CDS_INIT_LIST_HEAD(&event->enablers_ref_head);
 404         event->desc = desc;
 405
 406         if (desc->loglevel)
 407                 loglevel = *(*event->desc->loglevel);
 408         else
 409                 loglevel = TRACE_DEFAULT;
 410         if (desc->u.ext.model_emf_uri)
 411                 uri = *(desc->u.ext.model_emf_uri);
 412         else
 413                 uri = NULL;
 414
 415         /* Fetch event ID from sessiond */
 416         ret = ustcomm_register_event(notify_socket,
 417                 session->objd,
 418                 chan->objd,
 419                 event_name,
 420                 loglevel,
 421                 desc->signature,
 422                 desc->nr_fields,
 423                 desc->fields,
 424                 uri,
 425                 &event->id);
 426         if (ret < 0) {
 427                 DBG("Error (%d) registering event to sessiond", ret);
 428                 goto sessiond_register_error;
 429         }
 430
 431         /* Populate lttng_event structure before tracepoint registration. */
 432         cmm_smp_wmb();
 433         cds_list_add(&event->node, &chan->session->events_head);
 434         cds_hlist_add_head(&event->hlist, head);
 435         return 0;
 436
 437 sessiond_register_error:
 438         free(event);
 439 cache_error:
 440 socket_error:
 441 exist:
 442         return ret;
 443 }
 444
 445 static
 446 int lttng_desc_match_wildcard_enabler(const struct lttng_event_desc *desc,
 447                 struct lttng_enabler *enabler)
 448 {
 449         int loglevel = 0;
 450         unsigned int has_loglevel = 0;
 451
 452         assert(enabler->type == LTTNG_ENABLER_WILDCARD);
 453         /* Compare excluding final '*' */
 454         if (strncmp(desc->name, enabler->event_param.name,
 455                         strlen(enabler->event_param.name) - 1))
 456                 return 0;
 457         if (desc->loglevel) {
 458                 loglevel = *(*desc->loglevel);
 459                 has_loglevel = 1;
 460         }
 461         if (!lttng_loglevel_match(loglevel,
 462                         has_loglevel,
 463                         enabler->event_param.loglevel_type,
 464                         enabler->event_param.loglevel))
 465                 return 0;
 466         return 1;
 467 }
 468
 469 static
 470 int lttng_desc_match_event_enabler(const struct lttng_event_desc *desc,
 471                 struct lttng_enabler *enabler)
 472 {
 473         int loglevel = 0;
 474         unsigned int has_loglevel = 0;
 475
 476         assert(enabler->type == LTTNG_ENABLER_EVENT);
 477         if (strcmp(desc->name, enabler->event_param.name))
 478                 return 0;
 479         if (desc->loglevel) {
 480                 loglevel = *(*desc->loglevel);
 481                 has_loglevel = 1;
 482         }
 483         if (!lttng_loglevel_match(loglevel,
 484                         has_loglevel,
 485                         enabler->event_param.loglevel_type,
 486                         enabler->event_param.loglevel))
 487                 return 0;
 488         return 1;
 489 }
 490
 491 static
 492 int lttng_desc_match_enabler(const struct lttng_event_desc *desc,
 493                 struct lttng_enabler *enabler)
 494 {
 495         struct lttng_ust_excluder_node *excluder;
 496
 497         /* If event matches with an excluder, return 'does not match' */
 498         cds_list_for_each_entry(excluder, &enabler->excluder_head, node) {
 499                 int count;
 500
 501                 for (count = 0; count < excluder->excluder.count; count++) {
 502                         int found, len;
 503                         char *excluder_name;
 504
 505                         excluder_name = (char *) (excluder->excluder.names)
 506                                         + count * LTTNG_UST_SYM_NAME_LEN;
 507                         len = strnlen(excluder_name, LTTNG_UST_SYM_NAME_LEN);
 508                         if (len > 0 && excluder_name[len - 1] == '*') {
 509                                 found = !strncmp(desc->name, excluder_name,
 510                                                 len - 1);
 511                         } else {
 512                                 found = !strncmp(desc->name, excluder_name,
 513                                                 LTTNG_UST_SYM_NAME_LEN - 1);
 514                         }
 515                         if (found) {
 516                                 return 0;
 517                         }
 518                 }
 519         }
 520         switch (enabler->type) {
 521         case LTTNG_ENABLER_WILDCARD:
 522                 return lttng_desc_match_wildcard_enabler(desc, enabler);
 523         case LTTNG_ENABLER_EVENT:
 524                 return lttng_desc_match_event_enabler(desc, enabler);
 525         default:
 526                 return -EINVAL;
 527         }
 528 }
 529
 530 static
 531 int lttng_event_match_enabler(struct lttng_event *event,
 532                 struct lttng_enabler *enabler)
 533 {
 534         if (lttng_desc_match_enabler(event->desc, enabler)
 535                         && event->chan == enabler->chan)
 536                 return 1;
 537         else
 538                 return 0;
 539 }
 540
 541 static
 542 struct lttng_enabler_ref * lttng_event_enabler_ref(struct lttng_event *event,
 543                 struct lttng_enabler *enabler)
 544 {
 545         struct lttng_enabler_ref *enabler_ref;
 546
 547         cds_list_for_each_entry(enabler_ref,
 548                         &event->enablers_ref_head, node) {
 549                 if (enabler_ref->ref == enabler)
 550                         return enabler_ref;
 551         }
 552         return NULL;
 553 }
 554
 555 /*
 556  * Create struct lttng_event if it is missing and present in the list of
 557  * tracepoint probes.
 558  */
 559 static
 560 void lttng_create_event_if_missing(struct lttng_enabler *enabler)
 561 {
 562         struct lttng_session *session = enabler->chan->session;
 563         struct lttng_probe_desc *probe_desc;
 564         const struct lttng_event_desc *desc;
 565         struct lttng_event *event;
 566         int i;
 567         struct cds_list_head *probe_list;
 568
 569         probe_list = lttng_get_probe_list_head();
 570         /*
 571          * For each probe event, if we find that a probe event matches
 572          * our enabler, create an associated lttng_event if not
 573          * already present.
 574          */
 575         cds_list_for_each_entry(probe_desc, probe_list, head) {
 576                 for (i = 0; i < probe_desc->nr_events; i++) {
 577                         int found = 0, ret;
 578                         struct cds_hlist_head *head;
 579                         struct cds_hlist_node *node;
 580                         const char *event_name;
 581                         size_t name_len;
 582                         uint32_t hash;
 583
 584                         desc = probe_desc->event_desc[i];
 585                         if (!lttng_desc_match_enabler(desc, enabler))
 586                                 continue;
 587                         event_name = desc->name;
 588                         name_len = strlen(event_name);
 589
 590                         /*
 591                          * Check if already created.
 592                          */
 593                         hash = jhash(event_name, name_len, 0);
 594                         head = &session->events_ht.table[hash & (LTTNG_UST_EVENT_HT_SIZE - 1)];
 595                         cds_hlist_for_each_entry(event, node, head, hlist) {
 596                                 if (event->desc == desc
 597                                                 && event->chan == enabler->chan)
 598                                         found = 1;
 599                         }
 600                         if (found)
 601                                 continue;
 602
 603                         /*
 604                          * We need to create an event for this
 605                          * event probe.
 606                          */
 607                         ret = lttng_event_create(probe_desc->event_desc[i],
 608                                         enabler->chan);
 609                         if (ret) {
 610                                 DBG("Unable to create event %s, error %d\n",
 611                                         probe_desc->event_desc[i]->name, ret);
 612                         }
 613                 }
 614         }
 615 }
 616
 617 /*
 618  * Create events associated with an enabler (if not already present),
 619  * and add backward reference from the event to the enabler.
 620  */
 621 static
 622 int lttng_enabler_ref_events(struct lttng_enabler *enabler)
 623 {
 624         struct lttng_session *session = enabler->chan->session;
 625         struct lttng_event *event;
 626
 627         /* First ensure that probe events are created for this enabler. */
 628         lttng_create_event_if_missing(enabler);
 629
 630         /* For each event matching enabler in session event list. */
 631         cds_list_for_each_entry(event, &session->events_head, node) {
 632                 struct lttng_enabler_ref *enabler_ref;
 633
 634                 if (!lttng_event_match_enabler(event, enabler))
 635                         continue;
 636
 637                 enabler_ref = lttng_event_enabler_ref(event, enabler);
 638                 if (!enabler_ref) {
 639                         /*
 640                          * If no backward ref, create it.
 641                          * Add backward ref from event to enabler.
 642                          */
 643                         enabler_ref = zmalloc(sizeof(*enabler_ref));
 644                         if (!enabler_ref)
 645                                 return -ENOMEM;
 646                         enabler_ref->ref = enabler;
 647                         cds_list_add(&enabler_ref->node,
 648                                 &event->enablers_ref_head);
 649                 }
 650
 651                 /*
 652                  * Link filter bytecodes if not linked yet.
 653                  */
 654                 lttng_enabler_event_link_bytecode(event, enabler);
 655
 656                 /* TODO: merge event context. */
 657         }
 658         return 0;
 659 }
 660
 661 /*
 662  * Called at library load: connect the probe on all enablers matching
 663  * this event.
 664  * Called with session mutex held.
 665  */
 666 int lttng_fix_pending_events(void)
 667 {
 668         struct lttng_session *session;
 669
 670         cds_list_for_each_entry(session, &sessions, node) {
 671                 lttng_session_lazy_sync_enablers(session);
 672         }
 673         return 0;
 674 }
 675
 676 /*
 677  * For each session of the owner thread, execute pending statedump.
 678  * Only dump state for the sessions owned by the caller thread, because
 679  * we don't keep ust_lock across the entire iteration.
 680  */
 681 void lttng_handle_pending_statedump(void *owner)
 682 {
 683         struct lttng_session *session;
 684
 685         /* Execute state dump */
 686         lttng_ust_baddr_statedump(owner);
 687
 688         /* Clear pending state dump */
 689         if (ust_lock()) {
 690                 goto end;
 691         }
 692         cds_list_for_each_entry(session, &sessions, node) {
 693                 if (session->owner != owner)
 694                         continue;
 695                 if (!session->statedump_pending)
 696                         continue;
 697                 session->statedump_pending = 0;
 698         }
 699 end:
 700         ust_unlock();
 701         return;
 702 }
 703
 704 /*
 705  * Only used internally at session destruction.
 706  */
 707 static
 708 void _lttng_event_destroy(struct lttng_event *event)
 709 {
 710         struct lttng_enabler_ref *enabler_ref, *tmp_enabler_ref;
 711
 712         cds_list_del(&event->node);
 713         lttng_destroy_context(event->ctx);
 714         lttng_free_event_filter_runtime(event);
 715         /* Free event enabler refs */
 716         cds_list_for_each_entry_safe(enabler_ref, tmp_enabler_ref,
 717                         &event->enablers_ref_head, node)
 718                 free(enabler_ref);
 719         free(event);
 720 }
 721
 722 void lttng_ust_events_exit(void)
 723 {
 724         struct lttng_session *session, *tmpsession;
 725
 726         cds_list_for_each_entry_safe(session, tmpsession, &sessions, node)
 727                 lttng_session_destroy(session);
 728 }
 729
 730 /*
 731  * Enabler management.
 732  */
 733 struct lttng_enabler *lttng_enabler_create(enum lttng_enabler_type type,
 734                 struct lttng_ust_event *event_param,
 735                 struct lttng_channel *chan)
 736 {
 737         struct lttng_enabler *enabler;
 738
 739         enabler = zmalloc(sizeof(*enabler));
 740         if (!enabler)
 741                 return NULL;
 742         enabler->type = type;
 743         CDS_INIT_LIST_HEAD(&enabler->filter_bytecode_head);
 744         CDS_INIT_LIST_HEAD(&enabler->excluder_head);
 745         memcpy(&enabler->event_param, event_param,
 746                 sizeof(enabler->event_param));
 747         enabler->chan = chan;
 748         /* ctx left NULL */
 749         /*
 750          * The "disable" event create comm field has been added to fix a
 751          * race between event creation (of a started trace) and enabling
 752          * filtering. New session daemon always set the "disable" field
 753          * to 1, and are aware that they need to explicitly enable the
 754          * event. Older session daemon (within same ABI) leave it at 0,
 755          * and therefore we need to enable it here, keeping the original
 756          * racy behavior.
 757          */
 758         enabler->enabled = !event_param->disabled;
 759         cds_list_add(&enabler->node, &enabler->chan->session->enablers_head);
 760         lttng_session_lazy_sync_enablers(enabler->chan->session);
 761         return enabler;
 762 }
 763
 764 int lttng_enabler_enable(struct lttng_enabler *enabler)
 765 {
 766         enabler->enabled = 1;
 767         lttng_session_lazy_sync_enablers(enabler->chan->session);
 768         return 0;
 769 }
 770
 771 int lttng_enabler_disable(struct lttng_enabler *enabler)
 772 {
 773         enabler->enabled = 0;
 774         lttng_session_lazy_sync_enablers(enabler->chan->session);
 775         return 0;
 776 }
 777
 778 int lttng_enabler_attach_bytecode(struct lttng_enabler *enabler,
 779                 struct lttng_ust_filter_bytecode_node *bytecode)
 780 {
 781         bytecode->enabler = enabler;
 782         cds_list_add_tail(&bytecode->node, &enabler->filter_bytecode_head);
 783         lttng_session_lazy_sync_enablers(enabler->chan->session);
 784         return 0;
 785 }
 786
 787 int lttng_enabler_attach_exclusion(struct lttng_enabler *enabler,
 788                 struct lttng_ust_excluder_node *excluder)
 789 {
 790         excluder->enabler = enabler;
 791         cds_list_add_tail(&excluder->node, &enabler->excluder_head);
 792         lttng_session_lazy_sync_enablers(enabler->chan->session);
 793         return 0;
 794 }
 795
 796 int lttng_attach_context(struct lttng_ust_context *context_param,
 797                 struct lttng_ctx **ctx, struct lttng_session *session)
 798 {
 799         /*
 800          * We cannot attach a context after trace has been started for a
 801          * session because the metadata does not allow expressing this
 802          * information outside of the original channel scope.
 803          */
 804         if (session->been_active)
 805                 return -EPERM;
 806
 807         switch (context_param->ctx) {
 808         case LTTNG_UST_CONTEXT_PTHREAD_ID:
 809                 return lttng_add_pthread_id_to_ctx(ctx);
 810         case LTTNG_UST_CONTEXT_PERF_THREAD_COUNTER:
 811         {
 812                 struct lttng_ust_perf_counter_ctx *perf_ctx_param;
 813
 814                 perf_ctx_param = &context_param->u.perf_counter;
 815                 return lttng_add_perf_counter_to_ctx(
 816                         perf_ctx_param->type,
 817                         perf_ctx_param->config,
 818                         perf_ctx_param->name,
 819                         ctx);
 820         }
 821         case LTTNG_UST_CONTEXT_VTID:
 822                 return lttng_add_vtid_to_ctx(ctx);
 823         case LTTNG_UST_CONTEXT_VPID:
 824                 return lttng_add_vpid_to_ctx(ctx);
 825         case LTTNG_UST_CONTEXT_PROCNAME:
 826                 return lttng_add_procname_to_ctx(ctx);
 827         case LTTNG_UST_CONTEXT_IP:
 828                 return lttng_add_ip_to_ctx(ctx);
 829         default:
 830                 return -EINVAL;
 831         }
 832 }
 833
 834 int lttng_enabler_attach_context(struct lttng_enabler *enabler,
 835                 struct lttng_ust_context *context_param)
 836 {
 837 #if 0   // disabled for now.
 838         struct lttng_session *session = enabler->chan->session;
 839         int ret;
 840
 841         ret = lttng_attach_context(context_param, &enabler->ctx,
 842                         session);
 843         if (ret)
 844                 return ret;
 845         lttng_session_lazy_sync_enablers(enabler->chan->session);
 846 #endif
 847         return -ENOSYS;
 848 }
 849
 850 static
 851 void lttng_enabler_destroy(struct lttng_enabler *enabler)
 852 {
 853         struct lttng_ust_filter_bytecode_node *filter_node, *tmp_filter_node;
 854         struct lttng_ust_excluder_node *excluder_node, *tmp_excluder_node;
 855
 856         /* Destroy filter bytecode */
 857         cds_list_for_each_entry_safe(filter_node, tmp_filter_node,
 858                         &enabler->filter_bytecode_head, node) {
 859                 free(filter_node);
 860         }
 861
 862         /* Destroy excluders */
 863         cds_list_for_each_entry_safe(excluder_node, tmp_excluder_node,
 864                         &enabler->excluder_head, node) {
 865                 free(excluder_node);
 866         }
 867
 868         /* Destroy contexts */
 869         lttng_destroy_context(enabler->ctx);
 870
 871         cds_list_del(&enabler->node);
 872         free(enabler);
 873 }
 874
 875 /*
 876  * lttng_session_sync_enablers should be called just before starting a
 877  * session.
 878  */
 879 static
 880 void lttng_session_sync_enablers(struct lttng_session *session)
 881 {
 882         struct lttng_enabler *enabler;
 883         struct lttng_event *event;
 884
 885         cds_list_for_each_entry(enabler, &session->enablers_head, node)
 886                 lttng_enabler_ref_events(enabler);
 887         /*
 888          * For each event, if at least one of its enablers is enabled,
 889          * and its channel and session transient states are enabled, we
 890          * enable the event, else we disable it.
 891          */
 892         cds_list_for_each_entry(event, &session->events_head, node) {
 893                 struct lttng_enabler_ref *enabler_ref;
 894                 struct lttng_bytecode_runtime *runtime;
 895                 int enabled = 0, has_enablers_without_bytecode = 0;
 896
 897                 /* Enable events */
 898                 cds_list_for_each_entry(enabler_ref,
 899                                 &event->enablers_ref_head, node) {
 900                         if (enabler_ref->ref->enabled) {
 901                                 enabled = 1;
 902                                 break;
 903                         }
 904                 }
 905                 /*
 906                  * Enabled state is based on union of enablers, with
 907                  * intesection of session and channel transient enable
 908                  * states.
 909                  */
 910                 enabled = enabled && session->tstate && event->chan->tstate;
 911
 912                 CMM_STORE_SHARED(event->enabled, enabled);
 913                 /*
 914                  * Sync tracepoint registration with event enabled
 915                  * state.
 916                  */
 917                 if (enabled) {
 918                         if (!event->registered)
 919                                 register_event(event);
 920                 } else {
 921                         if (event->registered)
 922                                 unregister_event(event);
 923                 }
 924
 925                 /* Check if has enablers without bytecode enabled */
 926                 cds_list_for_each_entry(enabler_ref,
 927                                 &event->enablers_ref_head, node) {
 928                         if (enabler_ref->ref->enabled
 929                                         && cds_list_empty(&enabler_ref->ref->filter_bytecode_head)) {
 930                                 has_enablers_without_bytecode = 1;
 931                                 break;
 932                         }
 933                 }
 934                 event->has_enablers_without_bytecode =
 935                         has_enablers_without_bytecode;
 936
 937                 /* Enable filters */
 938                 cds_list_for_each_entry(runtime,
 939                                 &event->bytecode_runtime_head, node) {
 940                         lttng_filter_sync_state(runtime);
 941                 }
 942         }
 943 }
 944
 945 /*
 946  * Apply enablers to session events, adding events to session if need
 947  * be. It is required after each modification applied to an active
 948  * session, and right before session "start".
 949  * "lazy" sync means we only sync if required.
 950  */
 951 static
 952 void lttng_session_lazy_sync_enablers(struct lttng_session *session)
 953 {
 954         /* We can skip if session is not active */
 955         if (!session->active)
 956                 return;
 957         lttng_session_sync_enablers(session);
 958 }