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]", chan, 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                                    struct lttng_kernel_event *event_param,
 206                                    void *filter)
 207 {
 208         struct ltt_event *event;
 209         int ret;
 210
 211         mutex_lock(&sessions_mutex);
 212         if (chan->free_event_id == -1UL)
 213                 goto full;
 214         /*
 215          * This is O(n^2) (for each event, the loop is called at event
 216          * creation). Might require a hash if we have lots of events.
 217          */
 218         list_for_each_entry(event, &chan->session->events, list)
 219                 if (!strcmp(event->desc->name, name))
 220                         goto exist;
 221         event = kmem_cache_zalloc(event_cache, GFP_KERNEL);
 222         if (!event)
 223                 goto cache_error;
 224         event->chan = chan;
 225         event->filter = filter;
 226         event->id = chan->free_event_id++;
 227         event->instrumentation = event_param->instrumentation;
 228         /* Populate ltt_event structure before tracepoint registration. */
 229         smp_wmb();
 230         switch (event_param->instrumentation) {
 231         case LTTNG_KERNEL_TRACEPOINTS:
 232                 event->desc = ltt_event_get(name);
 233                 if (!event->desc)
 234                         goto register_error;
 235                 ret = tracepoint_probe_register(name,
 236                                 event->desc->probe_callback,
 237                                 event);
 238                 if (ret)
 239                         goto register_error;
 240                 break;
 241         case LTTNG_KERNEL_KPROBES:
 242                 ret = lttng_kprobes_register(name,
 243                                 event_param->u.kprobe.symbol_name,
 244                                 event_param->u.kprobe.offset,
 245                                 event_param->u.kprobe.addr,
 246                                 event);
 247                 if (ret)
 248                         goto register_error;
 249                 break;
 250         default:
 251                 WARN_ON_ONCE(1);
 252         }
 253         ret = _ltt_event_metadata_statedump(chan->session, chan, event);
 254         if (ret)
 255                 goto statedump_error;
 256         list_add(&event->list, &chan->session->events);
 257         mutex_unlock(&sessions_mutex);
 258         return event;
 259
 260 statedump_error:
 261         WARN_ON_ONCE(tracepoint_probe_unregister(name,
 262                                 event->desc->probe_callback,
 263                                 event));
 264         ltt_event_put(event->desc);
 265 register_error:
 266         kmem_cache_free(event_cache, event);
 267 cache_error:
 268 exist:
 269 full:
 270         mutex_unlock(&sessions_mutex);
 271         return NULL;
 272 }
 273
 274 /*
 275  * Only used internally at session destruction.
 276  */
 277 int _ltt_event_unregister(struct ltt_event *event)
 278 {
 279         int ret = -EINVAL;
 280
 281         switch (event->instrumentation) {
 282         case LTTNG_KERNEL_TRACEPOINTS:
 283                 ret = tracepoint_probe_unregister(event->desc->name,
 284                                                   event->desc->probe_callback,
 285                                                   event);
 286                 if (ret)
 287                         return ret;
 288                 ltt_event_put(event->desc);
 289                 break;
 290         case LTTNG_KERNEL_KPROBES:
 291                 lttng_kprobes_unregister(event);
 292                 ret = 0;
 293                 break;
 294         default:
 295                 WARN_ON_ONCE(1);
 296         }
 297         return ret;
 298 }
 299
 300 /*
 301  * Used when an event FD is released.
 302  */
 303 int ltt_event_unregister(struct ltt_event *event)
 304 {
 305         int ret;
 306
 307         mutex_lock(&sessions_mutex);
 308         ret = ltt_event_unregister(event);
 309         mutex_unlock(&sessions_mutex);
 310         return ret;
 311 }
 312
 313 /*
 314  * Only used internally at session destruction.
 315  */
 316 static
 317 void _ltt_event_destroy(struct ltt_event *event)
 318 {
 319         ltt_event_put(event->desc);
 320         list_del(&event->list);
 321         kmem_cache_free(event_cache, event);
 322 }
 323
 324 /*
 325  * We have exclusive access to our metadata buffer (protected by the
 326  * sessions_mutex), so we can do racy operations such as looking for
 327  * remaining space left in packet and write, since mutual exclusion
 328  * protects us from concurrent writes.
 329  */
 330 int lttng_metadata_printf(struct ltt_session *session,
 331                           const char *fmt, ...)
 332 {
 333         struct lib_ring_buffer_ctx ctx;
 334         struct ltt_channel *chan = session->metadata;
 335         char *str;
 336         int ret = 0, waitret;
 337         size_t len, reserve_len, pos;
 338         va_list ap;
 339
 340         WARN_ON_ONCE(!ACCESS_ONCE(session->active));
 341
 342         va_start(ap, fmt);
 343         str = kvasprintf(GFP_KERNEL, fmt, ap);
 344         va_end(ap);
 345         if (!str)
 346                 return -ENOMEM;
 347
 348         len = strlen(str);
 349         pos = 0;
 350
 351         for (pos = 0; pos < len; pos += reserve_len) {
 352                 reserve_len = min_t(size_t,
 353                                 chan->ops->packet_avail_size(chan->chan),
 354                                 len - pos);
 355                 lib_ring_buffer_ctx_init(&ctx, chan->chan, NULL, reserve_len,
 356                                          sizeof(char), -1);
 357                 /*
 358                  * We don't care about metadata buffer's records lost
 359                  * count, because we always retry here. Report error if
 360                  * we need to bail out after timeout or being
 361                  * interrupted.
 362                  */
 363                 waitret = wait_event_interruptible_timeout(*chan->ops->get_reader_wait_queue(chan),
 364                         ({
 365                                 ret = chan->ops->event_reserve(&ctx);
 366                                 ret != -ENOBUFS || !ret;
 367                         }),
 368                         msecs_to_jiffies(LTTNG_METADATA_TIMEOUT_MSEC));
 369                 if (!waitret || waitret == -ERESTARTSYS || ret) {
 370                         printk(KERN_WARNING "LTTng: Failure to write metadata to buffers (%s)\n",
 371                                 waitret == -ERESTARTSYS ? "interrupted" :
 372                                         (ret == -ENOBUFS ? "timeout" : "I/O error"));
 373                         if (waitret == -ERESTARTSYS)
 374                                 ret = waitret;
 375                         goto end;
 376                 }
 377                 chan->ops->event_write(&ctx, &str[pos], len);
 378                 chan->ops->event_commit(&ctx);
 379         }
 380 end:
 381         kfree(str);
 382         return ret;
 383 }
 384
 385 static
 386 int _ltt_fields_metadata_statedump(struct ltt_session *session,
 387                                    struct ltt_event *event)
 388 {
 389         const struct lttng_event_desc *desc = event->desc;
 390         int ret = 0;
 391         int i;
 392
 393         for (i = 0; i < desc->nr_fields; i++) {
 394                 const struct lttng_event_field *field = &desc->fields[i];
 395
 396                 switch (field->type.atype) {
 397                 case atype_integer:
 398                         ret = lttng_metadata_printf(session,
 399                                 "               integer { size = %u; align = %u; signed = %u;%s } %s;\n",
 400                                 field->type.u.basic.integer.size,
 401                                 field->type.u.basic.integer.alignment,
 402                                 field->type.u.basic.integer.signedness,
 403 #ifdef __BIG_ENDIAN
 404                                 field->type.u.basic.integer.reverse_byte_order ? " byte_order = le;" : "",
 405 #else
 406                                 field->type.u.basic.integer.reverse_byte_order ? " byte_order = be;" : "",
 407 #endif
 408                                 field->name);
 409                         break;
 410                 case atype_enum:
 411                         ret = lttng_metadata_printf(session,
 412                                 "               %s %s;\n",
 413                                 field->type.u.basic.enumeration.name,
 414                                 field->name);
 415                         break;
 416                 case atype_array:
 417                 {
 418                         const struct lttng_basic_type *elem_type;
 419
 420                         elem_type = &field->type.u.array.elem_type;
 421                         ret = lttng_metadata_printf(session,
 422                                 "               integer { size = %u; align = %u; signed = %u;%s } %s[%u];\n",
 423                                 elem_type->u.basic.integer.size,
 424                                 elem_type->u.basic.integer.alignment,
 425                                 elem_type->u.basic.integer.signedness,
 426 #ifdef __BIG_ENDIAN
 427                                 elem_type->u.basic.integer.reverse_byte_order ? " byte_order = le;" : "",
 428 #else
 429                                 elem_type->u.basic.integer.reverse_byte_order ? " byte_order = be;" : "",
 430 #endif
 431                                 field->name, field->type.u.array.length);
 432                         break;
 433                 }
 434                 case atype_sequence:
 435                 {
 436                         const struct lttng_basic_type *elem_type;
 437                         const struct lttng_basic_type *length_type;
 438
 439                         elem_type = &field->type.u.sequence.elem_type;
 440                         length_type = &field->type.u.sequence.length_type;
 441                         ret = lttng_metadata_printf(session,
 442                                 "               integer { size = %u; align = %u; signed = %u;%s } %s[ integer { size = %u; align = %u; signed = %u;%s } ];\n",
 443                                 elem_type->u.basic.integer.size,
 444                                 elem_type->u.basic.integer.alignment,
 445                                 elem_type->u.basic.integer.signedness,
 446 #ifdef __BIG_ENDIAN
 447                                 elem_type->u.basic.integer.reverse_byte_order ? " byte_order = le;" : "",
 448 #else
 449                                 elem_type->u.basic.integer.reverse_byte_order ? " byte_order = be;" : "",
 450 #endif
 451                                 field->name,
 452                                         length_type->u.basic.integer.size,
 453                                         length_type->u.basic.integer.alignment,
 454                                         length_type->u.basic.integer.signedness,
 455 #ifdef __BIG_ENDIAN
 456                                         length_type->u.basic.integer.reverse_byte_order ? " byte_order = le;" : "",
 457 #else
 458                                         length_type->u.basic.integer.reverse_byte_order ? " byte_order = be;" : ""
 459 #endif
 460                                 );
 461                         break;
 462                 }
 463
 464                 case atype_string:
 465                         ret = lttng_metadata_printf(session,
 466                                 "               string%s %s;\n",
 467                                 field->type.u.basic.string.encoding == lttng_encode_ASCII ?
 468                                         " { encoding = ASCII; }" : "",
 469                                 field->name);
 470                         break;
 471                 default:
 472                         WARN_ON_ONCE(1);
 473                         return -EINVAL;
 474                 }
 475         }
 476         return ret;
 477 }
 478
 479 static
 480 int _ltt_event_metadata_statedump(struct ltt_session *session,
 481                                   struct ltt_channel *chan,
 482                                   struct ltt_event *event)
 483 {
 484         int ret = 0;
 485
 486         if (event->metadata_dumped || !ACCESS_ONCE(session->active))
 487                 return 0;
 488         if (chan == session->metadata)
 489                 return 0;
 490
 491         ret = lttng_metadata_printf(session,
 492                 "event {\n"
 493                 "       name = %s;\n"
 494                 "       id = %u;\n"
 495                 "       stream_id = %u;\n"
 496                 "       event.fields := struct {\n",
 497                 event->desc->name,
 498                 event->id,
 499                 event->chan->id);
 500         if (ret)
 501                 goto end;
 502
 503         ret = _ltt_fields_metadata_statedump(session, event);
 504         if (ret)
 505                 goto end;
 506
 507         /*
 508          * LTTng space reservation can only reserve multiples of the
 509          * byte size.
 510          */
 511         ret = lttng_metadata_printf(session,
 512                 "       };\n"
 513                 "};\n\n");
 514         if (ret)
 515                 goto end;
 516
 517
 518
 519
 520         event->metadata_dumped = 1;
 521 end:
 522         return ret;
 523
 524 }
 525
 526 static
 527 int _ltt_channel_metadata_statedump(struct ltt_session *session,
 528                                     struct ltt_channel *chan)
 529 {
 530         int ret = 0;
 531
 532         if (chan->metadata_dumped || !ACCESS_ONCE(session->active))
 533                 return 0;
 534         if (chan == session->metadata)
 535                 return 0;
 536
 537         WARN_ON_ONCE(!chan->header_type);
 538         ret = lttng_metadata_printf(session,
 539                 "stream {\n"
 540                 "       id = %u;\n"
 541                 "       event.header := %s;\n"
 542                 "       packet.context := struct packet_context;\n"
 543                 "};\n\n",
 544                 chan->id,
 545                 chan->header_type == 1 ? "struct event_header_compact" :
 546                         "struct event_header_large");
 547         if (ret)
 548                 goto end;
 549
 550         chan->metadata_dumped = 1;
 551 end:
 552         return ret;
 553 }
 554
 555 static
 556 int _ltt_stream_packet_context_declare(struct ltt_session *session)
 557 {
 558         return lttng_metadata_printf(session,
 559                 "struct packet_context {\n"
 560                 "       uint64_t timestamp_begin;\n"
 561                 "       uint64_t timestamp_end;\n"
 562                 "       uint32_t events_discarded;\n"
 563                 "       uint32_t content_size;\n"
 564                 "       uint32_t packet_size;\n"
 565                 "       uint32_t cpu_id;\n"
 566                 "};\n"
 567                 );
 568 }
 569
 570 /*
 571  * Compact header:
 572  * id: range: 0 - 30.
 573  * id 31 is reserved to indicate an extended header.
 574  *
 575  * Large header:
 576  * id: range: 0 - 65534.
 577  * id 65535 is reserved to indicate an extended header.
 578  */
 579 static
 580 int _ltt_event_header_declare(struct ltt_session *session)
 581 {
 582         return lttng_metadata_printf(session,
 583         "struct event_header_compact {\n"
 584         "       enum : uint5_t { compact = 0 ... 30, extended = 31 } id;\n"
 585         "       variant <id> {\n"
 586         "               struct {\n"
 587         "                       uint27_t timestamp;\n"
 588         "               } compact;\n"
 589         "               struct {\n"
 590         "                       uint32_t id;\n"
 591         "                       uint64_t timestamp;\n"
 592         "               } extended;\n"
 593         "       } v;\n"
 594         "} align(%u);\n"
 595         "\n"
 596         "struct event_header_large {\n"
 597         "       enum : uint16_t { compact = 0 ... 65534, extended = 65535 } id;\n"
 598         "       variant <id> {\n"
 599         "               struct {\n"
 600         "                       uint32_t timestamp;\n"
 601         "               } compact;\n"
 602         "               struct {\n"
 603         "                       uint32_t id;\n"
 604         "                       uint64_t timestamp;\n"
 605         "               } extended;\n"
 606         "       } v;\n"
 607         "} align(%u);\n\n",
 608         ltt_alignof(uint32_t) * CHAR_BIT,
 609         ltt_alignof(uint16_t) * CHAR_BIT
 610         );
 611 }
 612
 613 /*
 614  * Output metadata into this session's metadata buffers.
 615  */
 616 static
 617 int _ltt_session_metadata_statedump(struct ltt_session *session)
 618 {
 619         char uuid_s[37];
 620         struct ltt_channel *chan;
 621         struct ltt_event *event;
 622         int ret = 0;
 623
 624         if (!ACCESS_ONCE(session->active))
 625                 return 0;
 626         if (session->metadata_dumped)
 627                 goto skip_session;
 628         if (!session->metadata) {
 629                 printk(KERN_WARNING "LTTng: attempt to start tracing, but metadata channel is not found. Operation abort.\n");
 630                 return -EPERM;
 631         }
 632
 633         snprintf(uuid_s, sizeof(uuid_s),
 634                 "%x%x%x%x-%x%x-%x%x-%x%x-%x%x%x%x%x%x",
 635                 uuid_s[0], uuid_s[1], uuid_s[2], uuid_s[3],
 636                 uuid_s[4], uuid_s[5], uuid_s[6], uuid_s[7],
 637                 uuid_s[8], uuid_s[9], uuid_s[10], uuid_s[11],
 638                 uuid_s[12], uuid_s[13], uuid_s[14], uuid_s[15]);
 639
 640         ret = lttng_metadata_printf(session,
 641                 "typealias integer { size = 8; align = %u; signed = false; } := uint8_t;\n"
 642                 "typealias integer { size = 16; align = %u; signed = false; } := uint16_t;\n"
 643                 "typealias integer { size = 32; align = %u; signed = false; } := uint32_t;\n"
 644                 "typealias integer { size = 64; align = %u; signed = false; } := uint64_t;\n"
 645                 "typealias integer { size = 5; align = 1; signed = false; } := uint5_t;\n"
 646                 "typealias integer { size = 27; align = 1; signed = false; } := uint27_t;\n"
 647                 "\n"
 648                 "trace {\n"
 649                 "       major = %u;\n"
 650                 "       minor = %u;\n"
 651                 "       uuid = %s;\n"
 652                 "       byte_order = %s;\n"
 653                 "       packet.header := struct {\n"
 654                 "               uint32_t magic;\n"
 655                 "               uint8_t  uuid[16];\n"
 656                 "               uint32_t stream_id;\n"
 657                 "       };\n",
 658                 "};\n\n",
 659                 ltt_alignof(uint8_t) * CHAR_BIT,
 660                 ltt_alignof(uint32_t) * CHAR_BIT,
 661                 ltt_alignof(uint64_t) * CHAR_BIT,
 662                 CTF_VERSION_MAJOR,
 663                 CTF_VERSION_MINOR,
 664                 uuid_s,
 665 #ifdef __BIG_ENDIAN
 666                 "be"
 667 #else
 668                 "le"
 669 #endif
 670                 );
 671         if (ret)
 672                 goto end;
 673
 674         ret = _ltt_stream_packet_context_declare(session);
 675         if (ret)
 676                 goto end;
 677
 678         ret = _ltt_event_header_declare(session);
 679         if (ret)
 680                 goto end;
 681
 682 skip_session:
 683         list_for_each_entry(chan, &session->chan, list) {
 684                 ret = _ltt_channel_metadata_statedump(session, chan);
 685                 if (ret)
 686                         goto end;
 687         }
 688
 689         list_for_each_entry(event, &session->events, list) {
 690                 ret = _ltt_event_metadata_statedump(session, chan, event);
 691                 if (ret)
 692                         goto end;
 693         }
 694         session->metadata_dumped = 1;
 695 end:
 696         return ret;
 697 }
 698
 699 /**
 700  * ltt_transport_register - LTT transport registration
 701  * @transport: transport structure
 702  *
 703  * Registers a transport which can be used as output to extract the data out of
 704  * LTTng. The module calling this registration function must ensure that no
 705  * trap-inducing code will be executed by the transport functions. E.g.
 706  * vmalloc_sync_all() must be called between a vmalloc and the moment the memory
 707  * is made visible to the transport function. This registration acts as a
 708  * vmalloc_sync_all. Therefore, only if the module allocates virtual memory
 709  * after its registration must it synchronize the TLBs.
 710  */
 711 void ltt_transport_register(struct ltt_transport *transport)
 712 {
 713         /*
 714          * Make sure no page fault can be triggered by the module about to be
 715          * registered. We deal with this here so we don't have to call
 716          * vmalloc_sync_all() in each module's init.
 717          */
 718         wrapper_vmalloc_sync_all();
 719
 720         mutex_lock(&sessions_mutex);
 721         list_add_tail(&transport->node, &ltt_transport_list);
 722         mutex_unlock(&sessions_mutex);
 723 }
 724 EXPORT_SYMBOL_GPL(ltt_transport_register);
 725
 726 /**
 727  * ltt_transport_unregister - LTT transport unregistration
 728  * @transport: transport structure
 729  */
 730 void ltt_transport_unregister(struct ltt_transport *transport)
 731 {
 732         mutex_lock(&sessions_mutex);
 733         list_del(&transport->node);
 734         mutex_unlock(&sessions_mutex);
 735 }
 736 EXPORT_SYMBOL_GPL(ltt_transport_unregister);
 737
 738 static int __init ltt_events_init(void)
 739 {
 740         int ret;
 741
 742         event_cache = KMEM_CACHE(ltt_event, 0);
 743         if (!event_cache)
 744                 return -ENOMEM;
 745         ret = ltt_debugfs_abi_init();
 746         if (ret)
 747                 goto error_abi;
 748         return 0;
 749 error_abi:
 750         kmem_cache_destroy(event_cache);
 751         return ret;
 752 }
 753
 754 module_init(ltt_events_init);
 755
 756 static void __exit ltt_events_exit(void)
 757 {
 758         struct ltt_session *session, *tmpsession;
 759
 760         ltt_debugfs_abi_exit();
 761         list_for_each_entry_safe(session, tmpsession, &sessions, list)
 762                 ltt_session_destroy(session);
 763         kmem_cache_destroy(event_cache);
 764 }
 765
 766 module_exit(ltt_events_exit);
 767
 768 MODULE_LICENSE("GPL and additional rights");
 769 MODULE_AUTHOR("Mathieu Desnoyers <mathieu.desnoyers@efficios.com>");
 770 MODULE_DESCRIPTION("LTTng Events");