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