ltt-events.c

   1 /*
   2  * ltt-events.c
   3  *
   4  * Copyright 2010 (c) - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   5  *
   6  * Holds LTTng per-session event registry.
   7  */
   8
   9 #include <linux/module.h>
  10 #include <linux/list.h>
  11 #include <linux/mutex.h>
  12 #include <linux/sched.h>
  13 #include <linux/slab.h>
  14 #include <linux/jiffies.h>
  15 #include <linux/uuid.h>
  16 #include "wrapper/vmalloc.h"    /* for wrapper_vmalloc_sync_all() */
  17 #include "ltt-events.h"
  18 #include "ltt-tracer.h"
  19
  20 static LIST_HEAD(sessions);
  21 static LIST_HEAD(ltt_transport_list);
  22 static DEFINE_MUTEX(sessions_mutex);
  23 static struct kmem_cache *event_cache;
  24
  25 static void _ltt_event_destroy(struct ltt_event *event);
  26 static int _ltt_event_unregister(struct ltt_event *event);
  27 static
  28 int _ltt_event_metadata_statedump(struct ltt_session *session,
  29                                   struct ltt_channel *chan,
  30                                   struct ltt_event *event);
  31 static
  32 int _ltt_session_metadata_statedump(struct ltt_session *session);
  33
  34
  35 static
  36 void synchronize_trace(void)
  37 {
  38         synchronize_sched();
  39 #ifdef CONFIG_PREEMPT_RT
  40         synchronize_rcu();
  41 #endif
  42 }
  43
  44 struct ltt_session *ltt_session_create(void)
  45 {
  46         struct ltt_session *session;
  47
  48         mutex_lock(&sessions_mutex);
  49         session = kzalloc(sizeof(struct ltt_session), GFP_KERNEL);
  50         if (!session)
  51                 return NULL;
  52         INIT_LIST_HEAD(&session->chan);
  53         INIT_LIST_HEAD(&session->events);
  54         uuid_le_gen(&session->uuid);
  55         list_add(&session->list, &sessions);
  56         mutex_unlock(&sessions_mutex);
  57         return session;
  58 }
  59
  60 void ltt_session_destroy(struct ltt_session *session)
  61 {
  62         struct ltt_channel *chan, *tmpchan;
  63         struct ltt_event *event, *tmpevent;
  64         int ret;
  65
  66         mutex_lock(&sessions_mutex);
  67         ACCESS_ONCE(session->active) = 0;
  68         list_for_each_entry(event, &session->events, list) {
  69                 ret = _ltt_event_unregister(event);
  70                 WARN_ON(ret);
  71         }
  72         synchronize_trace();    /* Wait for in-flight events to complete */
  73         list_for_each_entry_safe(event, tmpevent, &session->events, list)
  74                 _ltt_event_destroy(event);
  75         list_for_each_entry_safe(chan, tmpchan, &session->chan, list)
  76                 _ltt_channel_destroy(chan);
  77         list_del(&session->list);
  78         mutex_unlock(&sessions_mutex);
  79         kfree(session);
  80 }
  81
  82 int ltt_session_start(struct ltt_session *session)
  83 {
  84         int ret = 0;
  85         struct ltt_channel *chan;
  86
  87         mutex_lock(&sessions_mutex);
  88         if (session->active) {
  89                 ret = -EBUSY;
  90                 goto end;
  91         }
  92
  93         /*
  94          * Snapshot the number of events per channel to know the type of header
  95          * we need to use.
  96          */
  97         list_for_each_entry(chan, &session->chan, list) {
  98                 if (chan->header_type)
  99                         continue;               /* don't change it if session stop/restart */
 100                 if (chan->free_event_id < 31)
 101                         chan->header_type = 1;  /* compact */
 102                 else
 103                         chan->header_type = 2;  /* large */
 104         }
 105
 106         ACCESS_ONCE(session->active) = 1;
 107         synchronize_trace();    /* Wait for in-flight events to complete */
 108         ret = _ltt_session_metadata_statedump(session);
 109         if (ret) {
 110                 ACCESS_ONCE(session->active) = 0;
 111                 synchronize_trace();    /* Wait for in-flight events to complete */
 112         }
 113 end:
 114         mutex_unlock(&sessions_mutex);
 115         return ret;
 116 }
 117
 118 int ltt_session_stop(struct ltt_session *session)
 119 {
 120         int ret = 0;
 121
 122         mutex_lock(&sessions_mutex);
 123         if (!session->active) {
 124                 ret = -EBUSY;
 125                 goto end;
 126         }
 127         ACCESS_ONCE(session->active) = 0;
 128         synchronize_trace();    /* Wait for in-flight events to complete */
 129 end:
 130         mutex_unlock(&sessions_mutex);
 131         return ret;
 132 }
 133
 134 static struct ltt_transport *ltt_transport_find(const char *name)
 135 {
 136         struct ltt_transport *transport;
 137
 138         list_for_each_entry(transport, &ltt_transport_list, node) {
 139                 if (!strcmp(transport->name, name))
 140                         return transport;
 141         }
 142         return NULL;
 143 }
 144
 145 struct ltt_channel *ltt_channel_create(struct ltt_session *session,
 146                                        const char *transport_name,
 147                                        void *buf_addr,
 148                                        size_t subbuf_size, size_t num_subbuf,
 149                                        unsigned int switch_timer_interval,
 150                                        unsigned int read_timer_interval)
 151 {
 152         struct ltt_channel *chan;
 153         struct ltt_transport *transport;
 154
 155         mutex_lock(&sessions_mutex);
 156         if (session->active) {
 157                 printk(KERN_WARNING "LTTng refusing to add channel to active session\n");
 158                 goto active;    /* Refuse to add channel to active session */
 159         }
 160         transport = ltt_transport_find(transport_name);
 161         if (!transport) {
 162                 printk(KERN_WARNING "LTTng transport %s not found\n",
 163                        transport_name);
 164                 goto notransport;
 165         }
 166         chan = kzalloc(sizeof(struct ltt_channel), GFP_KERNEL);
 167         if (!chan)
 168                 goto nomem;
 169         chan->session = session;
 170         init_waitqueue_head(&chan->notify_wait);
 171         chan->chan = transport->ops.channel_create("[lttng]", session, buf_addr,
 172                         subbuf_size, num_subbuf, switch_timer_interval,
 173                         read_timer_interval);
 174         if (!chan->chan)
 175                 goto create_error;
 176         chan->id = session->free_chan_id++;
 177         chan->ops = &transport->ops;
 178         list_add(&chan->list, &session->chan);
 179         mutex_unlock(&sessions_mutex);
 180         return chan;
 181
 182 create_error:
 183         kfree(chan);
 184 nomem:
 185 notransport:
 186 active:
 187         mutex_unlock(&sessions_mutex);
 188         return NULL;
 189 }
 190
 191 /*
 192  * Only used internally at session destruction.
 193  */
 194 void _ltt_channel_destroy(struct ltt_channel *chan)
 195 {
 196         chan->ops->channel_destroy(chan->chan);
 197         list_del(&chan->list);
 198         kfree(chan);
 199 }
 200
 201 /*
 202  * Supports event creation while tracing session is active.
 203  */
 204 struct ltt_event *ltt_event_create(struct ltt_channel *chan, char *name,
 205                                    enum instrum_type itype,
 206                                    const struct lttng_event_desc *event_desc,
 207                                    void *filter)
 208 {
 209         struct ltt_event *event;
 210         int ret;
 211
 212         mutex_lock(&sessions_mutex);
 213         if (chan->free_event_id == -1UL)
 214                 goto full;
 215         /*
 216          * This is O(n^2) (for each event, the loop is called at event
 217          * creation). Might require a hash if we have lots of events.
 218          */
 219         list_for_each_entry(event, &chan->session->events, list)
 220                 if (!strcmp(event->desc->name, name))
 221                         goto exist;
 222         event = kmem_cache_zalloc(event_cache, GFP_KERNEL);
 223         if (!event)
 224                 goto cache_error;
 225         event->chan = chan;
 226         event->desc = event_desc;
 227         event->filter = filter;
 228         event->id = chan->free_event_id++;
 229         event->itype = itype;
 230         /* Populate ltt_event structure before tracepoint registration. */
 231         smp_wmb();
 232         switch (itype) {
 233         case INSTRUM_TRACEPOINTS:
 234                 ret = tracepoint_probe_register(name, event_desc->probe_callback,
 235                                                 event);
 236                 if (ret)
 237                         goto register_error;
 238                 break;
 239         default:
 240                 WARN_ON_ONCE(1);
 241         }
 242         ret = _ltt_event_metadata_statedump(chan->session, chan, event);
 243         if (ret)
 244                 goto statedump_error;
 245         list_add(&event->list, &chan->session->events);
 246         mutex_unlock(&sessions_mutex);
 247         return event;
 248
 249 statedump_error:
 250         WARN_ON_ONCE(tracepoint_probe_unregister(name, event_desc->probe_callback,
 251                                                  event));
 252 register_error:
 253         kmem_cache_free(event_cache, event);
 254 cache_error:
 255 exist:
 256 full:
 257         mutex_unlock(&sessions_mutex);
 258         return NULL;
 259 }
 260
 261 /*
 262  * Only used internally at session destruction.
 263  */
 264 int _ltt_event_unregister(struct ltt_event *event)
 265 {
 266         int ret = -EINVAL;
 267
 268         switch (event->itype) {
 269         case INSTRUM_TRACEPOINTS:
 270                 ret = tracepoint_probe_unregister(event->desc->name,
 271                                                   event->desc->probe_callback,
 272                                                   event);
 273                 if (ret)
 274                         return ret;
 275                 break;
 276         default:
 277                 WARN_ON_ONCE(1);
 278         }
 279         return ret;
 280 }
 281
 282 /*
 283  * Used when an event FD is released.
 284  */
 285 int ltt_event_unregister(struct ltt_event *event)
 286 {
 287         int ret;
 288
 289         mutex_lock(&sessions_mutex);
 290         ret = ltt_event_unregister(event);
 291         mutex_unlock(&sessions_mutex);
 292         return ret;
 293 }
 294
 295 /*
 296  * Only used internally at session destruction.
 297  */
 298 static
 299 void _ltt_event_destroy(struct ltt_event *event)
 300 {
 301         ltt_event_put(event->desc);
 302         list_del(&event->list);
 303         kmem_cache_free(event_cache, event);
 304 }
 305
 306 /*
 307  * We have exclusive access to our metadata buffer (protected by the
 308  * sessions_mutex), so we can do racy operations such as looking for
 309  * remaining space left in packet and write, since mutual exclusion
 310  * protects us from concurrent writes.
 311  */
 312 int lttng_metadata_printf(struct ltt_session *session,
 313                           const char *fmt, ...)
 314 {
 315         struct lib_ring_buffer_ctx ctx;
 316         struct ltt_channel *chan = session->metadata;
 317         char *str;
 318         int ret = 0, waitret;
 319         size_t len, reserve_len, pos;
 320         va_list ap;
 321
 322         WARN_ON_ONCE(!ACCESS_ONCE(session->active));
 323
 324         va_start(ap, fmt);
 325         str = kvasprintf(GFP_KERNEL, fmt, ap);
 326         va_end(ap);
 327         if (!str)
 328                 return -ENOMEM;
 329
 330         len = strlen(str);
 331         pos = 0;
 332
 333         for (pos = 0; pos < len; pos += reserve_len) {
 334                 reserve_len = min_t(size_t,
 335                                 chan->ops->packet_avail_size(chan->chan),
 336                                 len - pos);
 337                 lib_ring_buffer_ctx_init(&ctx, chan->chan, NULL, reserve_len,
 338                                          sizeof(char), -1);
 339                 /*
 340                  * We don't care about metadata buffer's records lost
 341                  * count, because we always retry here. Report error if
 342                  * we need to bail out after timeout or being
 343                  * interrupted.
 344                  */
 345                 waitret = wait_event_interruptible_timeout(*chan->ops->get_reader_wait_queue(chan),
 346                         ({
 347                                 ret = chan->ops->event_reserve(&ctx);
 348                                 ret != -ENOBUFS || !ret;
 349                         }),
 350                         msecs_to_jiffies(LTTNG_METADATA_TIMEOUT_MSEC));
 351                 if (!waitret || waitret == -ERESTARTSYS || ret) {
 352                         printk(KERN_WARNING "LTTng: Failure to write metadata to buffers (%s)\n",
 353                                 waitret == -ERESTARTSYS ? "interrupted" :
 354                                         (ret == -ENOBUFS ? "timeout" : "I/O error"));
 355                         if (waitret == -ERESTARTSYS)
 356                                 ret = waitret;
 357                         goto end;
 358                 }
 359                 chan->ops->event_write(&ctx, &str[pos], len);
 360                 chan->ops->event_commit(&ctx);
 361         }
 362 end:
 363         kfree(str);
 364         return ret;
 365 }
 366
 367 static
 368 int _ltt_fields_metadata_statedump(struct ltt_session *session,
 369                                    struct ltt_event *event)
 370 {
 371         const struct lttng_event_desc *desc = event->desc;
 372         int ret = 0;
 373         int i;
 374
 375         for (i = 0; i < desc->nr_fields; i++) {
 376                 const struct lttng_event_field *field = &desc->fields[i];
 377
 378                 switch (field->type.atype) {
 379                 case atype_integer:
 380                         ret = lttng_metadata_printf(session,
 381                                 "               integer { size = %u; align = %u; signed = %u;%s } %s;\n",
 382                                 field->type.u.basic.integer.size,
 383                                 field->type.u.basic.integer.alignment,
 384                                 field->type.u.basic.integer.signedness,
 385 #ifdef __BIG_ENDIAN
 386                                 field->type.u.basic.integer.reverse_byte_order ? " byte_order = le;" : "",
 387 #else
 388                                 field->type.u.basic.integer.reverse_byte_order ? " byte_order = be;" : "",
 389 #endif
 390                                 field->name);
 391                         break;
 392                 case atype_enum:
 393                         ret = lttng_metadata_printf(session,
 394                                 "               %s %s;\n",
 395                                 field->type.u.basic.enumeration.name,
 396                                 field->name);
 397                         break;
 398                 case atype_array:
 399                 {
 400                         const struct lttng_basic_type *elem_type;
 401
 402                         elem_type = &field->type.u.array.elem_type;
 403                         ret = lttng_metadata_printf(session,
 404                                 "               integer { size = %u; align = %u; signed = %u;%s } %s[%u];\n",
 405                                 elem_type->u.basic.integer.size,
 406                                 elem_type->u.basic.integer.alignment,
 407                                 elem_type->u.basic.integer.signedness,
 408 #ifdef __BIG_ENDIAN
 409                                 elem_type->u.basic.integer.reverse_byte_order ? " byte_order = le;" : "",
 410 #else
 411                                 elem_type->u.basic.integer.reverse_byte_order ? " byte_order = be;" : "",
 412 #endif
 413                                 field->name, field->type.u.array.length);
 414                         break;
 415                 }
 416                 case atype_sequence:
 417                 {
 418                         const struct lttng_basic_type *elem_type;
 419                         const struct lttng_basic_type *length_type;
 420
 421                         elem_type = &field->type.u.sequence.elem_type;
 422                         length_type = &field->type.u.sequence.length_type;
 423                         ret = lttng_metadata_printf(session,
 424                                 "               integer { size = %u; align = %u; signed = %u;%s } %s[ integer { size = %u; align = %u; signed = %u;%s } ];\n",
 425                                 elem_type->u.basic.integer.size,
 426                                 elem_type->u.basic.integer.alignment,
 427                                 elem_type->u.basic.integer.signedness,
 428 #ifdef __BIG_ENDIAN
 429                                 elem_type->u.basic.integer.reverse_byte_order ? " byte_order = le;" : "",
 430 #else
 431                                 elem_type->u.basic.integer.reverse_byte_order ? " byte_order = be;" : "",
 432 #endif
 433                                 field->name,
 434                                         length_type->u.basic.integer.size,
 435                                         length_type->u.basic.integer.alignment,
 436                                         length_type->u.basic.integer.signedness,
 437 #ifdef __BIG_ENDIAN
 438                                         length_type->u.basic.integer.reverse_byte_order ? " byte_order = le;" : "",
 439 #else
 440                                         length_type->u.basic.integer.reverse_byte_order ? " byte_order = be;" : ""
 441 #endif
 442                                 );
 443                         break;
 444                 }
 445
 446                 case atype_string:
 447                         ret = lttng_metadata_printf(session,
 448                                 "               string%s %s;\n",
 449                                 field->type.u.basic.string.encoding == lttng_encode_ASCII ?
 450                                         " { encoding = ASCII; }" : "",
 451                                 field->name);
 452                         break;
 453                 default:
 454                         WARN_ON_ONCE(1);
 455                         return -EINVAL;
 456                 }
 457         }
 458         return ret;
 459 }
 460
 461 static
 462 int _ltt_event_metadata_statedump(struct ltt_session *session,
 463                                   struct ltt_channel *chan,
 464                                   struct ltt_event *event)
 465 {
 466         int ret = 0;
 467
 468         if (event->metadata_dumped || !ACCESS_ONCE(session->active))
 469                 return 0;
 470         if (chan == session->metadata)
 471                 return 0;
 472
 473         ret = lttng_metadata_printf(session,
 474                 "event {\n"
 475                 "       name = %s;\n"
 476                 "       id = %u;\n"
 477                 "       stream_id = %u;\n"
 478                 "       event.fields := struct {\n",
 479                 event->desc->name,
 480                 event->id,
 481                 event->chan->id);
 482         if (ret)
 483                 goto end;
 484
 485         ret = _ltt_fields_metadata_statedump(session, event);
 486         if (ret)
 487                 goto end;
 488
 489         /*
 490          * LTTng space reservation can only reserve multiples of the
 491          * byte size.
 492          */
 493         ret = lttng_metadata_printf(session,
 494                 "       } aligned(%u);\n"
 495                 "};\n\n", ltt_get_header_alignment());
 496         if (ret)
 497                 goto end;
 498
 499
 500
 501
 502         event->metadata_dumped = 1;
 503 end:
 504         return ret;
 505
 506 }
 507
 508 static
 509 int _ltt_channel_metadata_statedump(struct ltt_session *session,
 510                                     struct ltt_channel *chan)
 511 {
 512         int ret = 0;
 513
 514         if (chan->metadata_dumped || !ACCESS_ONCE(session->active))
 515                 return 0;
 516         if (chan == session->metadata)
 517                 return 0;
 518
 519         WARN_ON_ONCE(!chan->header_type);
 520         ret = lttng_metadata_printf(session,
 521                 "stream {\n"
 522                 "       id = %u;\n"
 523                 "       event.header := %s;\n",
 524                 "};\n\n",
 525                 chan->id,
 526                 chan->header_type == 1 ? "struct event_header_compact" :
 527                         "struct event_header_large");
 528         if (ret)
 529                 goto end;
 530
 531         chan->metadata_dumped = 1;
 532 end:
 533         return ret;
 534 }
 535
 536 /*
 537  * Output metadata into this session's metadata buffers.
 538  */
 539 static
 540 int _ltt_session_metadata_statedump(struct ltt_session *session)
 541 {
 542         char uuid_s[37];
 543         struct ltt_channel *chan;
 544         struct ltt_event *event;
 545         int ret = 0;
 546
 547         if (!ACCESS_ONCE(session->active))
 548                 return 0;
 549         if (session->metadata_dumped)
 550                 goto skip_session;
 551         if (!session->metadata) {
 552                 printk(KERN_WARNING "LTTng: attempt to start tracing, but metadata channel is not found. Operation abort.\n");
 553                 return -EPERM;
 554         }
 555
 556         snprintf(uuid_s, sizeof(uuid_s),
 557                 "%x%x%x%x-%x%x-%x%x-%x%x-%x%x%x%x%x%x",
 558                 uuid_s[0], uuid_s[1], uuid_s[2], uuid_s[3],
 559                 uuid_s[4], uuid_s[5], uuid_s[6], uuid_s[7],
 560                 uuid_s[8], uuid_s[9], uuid_s[10], uuid_s[11],
 561                 uuid_s[12], uuid_s[13], uuid_s[14], uuid_s[15]);
 562
 563         ret = lttng_metadata_printf(session,
 564                 "typealias integer {size = 8; align = %u; signed = false; } := uint8_t;\n"
 565                 "typealias integer {size = 32; align = %u; signed = false; } := uint32_t;\n"
 566                 "typealias integer {size = 64; align = %u; signed = false; } := uint64_t;\n"
 567                 "\n"
 568                 "trace {\n"
 569                 "       major = %u;\n"
 570                 "       minor = %u;\n"
 571                 "       uuid = %s;\n"
 572                 "       byte_order = %s;\n"
 573                 "       packet.header := struct {\n"
 574                 "               uint32_t magic;\n"
 575                 "               uint8_t  uuid[16];\n"
 576                 "               uint32_t stream_id;\n"
 577                 "               uint64_t timestamp_begin;\n"
 578                 "               uint64_t timestamp_end;\n"
 579                 "               uint32_t content_size;\n"
 580                 "               uint32_t packet_size;\n"
 581                 "               uint32_t events_lost;\n"
 582                 "       };\n",
 583                 "};\n\n",
 584                 ltt_alignof(uint8_t) * CHAR_BIT,
 585                 ltt_alignof(uint32_t) * CHAR_BIT,
 586                 ltt_alignof(uint64_t) * CHAR_BIT,
 587                 CTF_VERSION_MAJOR,
 588                 CTF_VERSION_MINOR,
 589                 uuid_s,
 590 #ifdef __BIG_ENDIAN
 591                 "be"
 592 #else
 593                 "le"
 594 #endif
 595                 );
 596         if (ret)
 597                 goto end;
 598
 599 skip_session:
 600         list_for_each_entry(chan, &session->chan, list) {
 601                 ret = _ltt_channel_metadata_statedump(session, chan);
 602                 if (ret)
 603                         goto end;
 604         }
 605
 606         list_for_each_entry(event, &session->events, list) {
 607                 ret = _ltt_event_metadata_statedump(session, chan, event);
 608                 if (ret)
 609                         goto end;
 610         }
 611         session->metadata_dumped = 1;
 612 end:
 613         return ret;
 614 }
 615
 616 /**
 617  * ltt_transport_register - LTT transport registration
 618  * @transport: transport structure
 619  *
 620  * Registers a transport which can be used as output to extract the data out of
 621  * LTTng. The module calling this registration function must ensure that no
 622  * trap-inducing code will be executed by the transport functions. E.g.
 623  * vmalloc_sync_all() must be called between a vmalloc and the moment the memory
 624  * is made visible to the transport function. This registration acts as a
 625  * vmalloc_sync_all. Therefore, only if the module allocates virtual memory
 626  * after its registration must it synchronize the TLBs.
 627  */
 628 void ltt_transport_register(struct ltt_transport *transport)
 629 {
 630         /*
 631          * Make sure no page fault can be triggered by the module about to be
 632          * registered. We deal with this here so we don't have to call
 633          * vmalloc_sync_all() in each module's init.
 634          */
 635         wrapper_vmalloc_sync_all();
 636
 637         mutex_lock(&sessions_mutex);
 638         list_add_tail(&transport->node, &ltt_transport_list);
 639         mutex_unlock(&sessions_mutex);
 640 }
 641 EXPORT_SYMBOL_GPL(ltt_transport_register);
 642
 643 /**
 644  * ltt_transport_unregister - LTT transport unregistration
 645  * @transport: transport structure
 646  */
 647 void ltt_transport_unregister(struct ltt_transport *transport)
 648 {
 649         mutex_lock(&sessions_mutex);
 650         list_del(&transport->node);
 651         mutex_unlock(&sessions_mutex);
 652 }
 653 EXPORT_SYMBOL_GPL(ltt_transport_unregister);
 654
 655 static int __init ltt_events_init(void)
 656 {
 657         int ret;
 658
 659         event_cache = KMEM_CACHE(ltt_event, 0);
 660         if (!event_cache)
 661                 return -ENOMEM;
 662         ret = ltt_debugfs_abi_init();
 663         if (ret)
 664                 goto error_abi;
 665         return 0;
 666 error_abi:
 667         kmem_cache_destroy(event_cache);
 668         return ret;
 669 }
 670
 671 module_init(ltt_events_init);
 672
 673 static void __exit ltt_events_exit(void)
 674 {
 675         struct ltt_session *session, *tmpsession;
 676
 677         ltt_debugfs_abi_exit();
 678         list_for_each_entry_safe(session, tmpsession, &sessions, list)
 679                 ltt_session_destroy(session);
 680         kmem_cache_destroy(event_cache);
 681 }
 682
 683 module_exit(ltt_events_exit);
 684
 685 MODULE_LICENSE("GPL and additional rights");
 686 MODULE_AUTHOR("Mathieu Desnoyers <mathieu.desnoyers@efficios.com>");
 687 MODULE_DESCRIPTION("LTTng Events");