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