lttng-ring-buffer-client.h

   1 /* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only)
   2  *
   3  * lttng-ring-buffer-client.h
   4  *
   5  * LTTng lib ring buffer client template.
   6  *
   7  * Copyright (C) 2010-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   8  */
   9
  10 #include <linux/module.h>
  11 #include <linux/types.h>
  12 #include <lttng/bitfield.h>
  13 #include <wrapper/trace-clock.h>
  14 #include <lttng/lttng-events.h>
  15 #include <lttng/lttng-tracer.h>
  16 #include <ringbuffer/frontend_types.h>
  17
  18 #define LTTNG_COMPACT_EVENT_BITS        5
  19 #define LTTNG_COMPACT_TSC_BITS          27
  20
  21 static struct lttng_transport lttng_relay_transport;
  22
  23 /*
  24  * Keep the natural field alignment for _each field_ within this structure if
  25  * you ever add/remove a field from this header. Packed attribute is not used
  26  * because gcc generates poor code on at least powerpc and mips. Don't ever
  27  * let gcc add padding between the structure elements.
  28  *
  29  * The guarantee we have with timestamps is that all the events in a
  30  * packet are included (inclusive) within the begin/end timestamps of
  31  * the packet. Another guarantee we have is that the "timestamp begin",
  32  * as well as the event timestamps, are monotonically increasing (never
  33  * decrease) when moving forward in a stream (physically). But this
  34  * guarantee does not apply to "timestamp end", because it is sampled at
  35  * commit time, which is not ordered with respect to space reservation.
  36  */
  37
  38 struct packet_header {
  39         /* Trace packet header */
  40         uint32_t magic;                 /*
  41                                          * Trace magic number.
  42                                          * contains endianness information.
  43                                          */
  44         uint8_t uuid[16];
  45         uint32_t stream_id;
  46         uint64_t stream_instance_id;
  47
  48         struct {
  49                 /* Stream packet context */
  50                 uint64_t timestamp_begin;       /* Cycle count at subbuffer start */
  51                 uint64_t timestamp_end;         /* Cycle count at subbuffer end */
  52                 uint64_t content_size;          /* Size of data in subbuffer */
  53                 uint64_t packet_size;           /* Subbuffer size (include padding) */
  54                 uint64_t packet_seq_num;        /* Packet sequence number */
  55                 unsigned long events_discarded; /*
  56                                                  * Events lost in this subbuffer since
  57                                                  * the beginning of the trace.
  58                                                  * (may overflow)
  59                                                  */
  60                 uint32_t cpu_id;                /* CPU id associated with stream */
  61                 uint8_t header_end;             /* End of header */
  62         } ctx;
  63 };
  64
  65 struct lttng_client_ctx {
  66         size_t packet_context_len;
  67         size_t event_context_len;
  68 };
  69
  70 static inline notrace u64 lib_ring_buffer_clock_read(struct channel *chan)
  71 {
  72         return trace_clock_read64();
  73 }
  74
  75 static inline
  76 size_t ctx_get_aligned_size(size_t offset, struct lttng_ctx *ctx,
  77                 size_t ctx_len)
  78 {
  79         size_t orig_offset = offset;
  80
  81         if (likely(!ctx))
  82                 return 0;
  83         offset += lib_ring_buffer_align(offset, ctx->largest_align);
  84         offset += ctx_len;
  85         return offset - orig_offset;
  86 }
  87
  88 static inline
  89 void ctx_get_struct_size(struct lttng_ctx *ctx, size_t *ctx_len,
  90                 struct lttng_channel *chan, struct lib_ring_buffer_ctx *bufctx)
  91 {
  92         int i;
  93         size_t offset = 0;
  94
  95         if (likely(!ctx)) {
  96                 *ctx_len = 0;
  97                 return;
  98         }
  99         for (i = 0; i < ctx->nr_fields; i++) {
 100                 if (ctx->fields[i].get_size)
 101                         offset += ctx->fields[i].get_size(offset);
 102                 if (ctx->fields[i].get_size_arg)
 103                         offset += ctx->fields[i].get_size_arg(offset,
 104                                         &ctx->fields[i], bufctx, chan);
 105         }
 106         *ctx_len = offset;
 107 }
 108
 109 static inline
 110 void ctx_record(struct lib_ring_buffer_ctx *bufctx,
 111                 struct lttng_channel *chan,
 112                 struct lttng_ctx *ctx)
 113 {
 114         int i;
 115
 116         if (likely(!ctx))
 117                 return;
 118         lib_ring_buffer_align_ctx(bufctx, ctx->largest_align);
 119         for (i = 0; i < ctx->nr_fields; i++)
 120                 ctx->fields[i].record(&ctx->fields[i], bufctx, chan);
 121 }
 122
 123 /*
 124  * record_header_size - Calculate the header size and padding necessary.
 125  * @config: ring buffer instance configuration
 126  * @chan: channel
 127  * @offset: offset in the write buffer
 128  * @pre_header_padding: padding to add before the header (output)
 129  * @ctx: reservation context
 130  *
 131  * Returns the event header size (including padding).
 132  *
 133  * The payload must itself determine its own alignment from the biggest type it
 134  * contains.
 135  */
 136 static __inline__
 137 size_t record_header_size(const struct lib_ring_buffer_config *config,
 138                                  struct channel *chan, size_t offset,
 139                                  size_t *pre_header_padding,
 140                                  struct lib_ring_buffer_ctx *ctx,
 141                                  struct lttng_client_ctx *client_ctx)
 142 {
 143         struct lttng_channel *lttng_chan = channel_get_private(chan);
 144         struct lttng_probe_ctx *lttng_probe_ctx = ctx->priv;
 145         struct lttng_event *event = lttng_probe_ctx->event;
 146         size_t orig_offset = offset;
 147         size_t padding;
 148
 149         switch (lttng_chan->header_type) {
 150         case 1: /* compact */
 151                 padding = lib_ring_buffer_align(offset, lttng_alignof(uint32_t));
 152                 offset += padding;
 153                 if (!(ctx->rflags & (RING_BUFFER_RFLAG_FULL_TSC | LTTNG_RFLAG_EXTENDED))) {
 154                         offset += sizeof(uint32_t);     /* id and timestamp */
 155                 } else {
 156                         /* Minimum space taken by LTTNG_COMPACT_EVENT_BITS id */
 157                         offset += (LTTNG_COMPACT_EVENT_BITS + CHAR_BIT - 1) / CHAR_BIT;
 158                         /* Align extended struct on largest member */
 159                         offset += lib_ring_buffer_align(offset, lttng_alignof(uint64_t));
 160                         offset += sizeof(uint32_t);     /* id */
 161                         offset += lib_ring_buffer_align(offset, lttng_alignof(uint64_t));
 162                         offset += sizeof(uint64_t);     /* timestamp */
 163                 }
 164                 break;
 165         case 2: /* large */
 166                 padding = lib_ring_buffer_align(offset, lttng_alignof(uint16_t));
 167                 offset += padding;
 168                 offset += sizeof(uint16_t);
 169                 if (!(ctx->rflags & (RING_BUFFER_RFLAG_FULL_TSC | LTTNG_RFLAG_EXTENDED))) {
 170                         offset += lib_ring_buffer_align(offset, lttng_alignof(uint32_t));
 171                         offset += sizeof(uint32_t);     /* timestamp */
 172                 } else {
 173                         /* Align extended struct on largest member */
 174                         offset += lib_ring_buffer_align(offset, lttng_alignof(uint64_t));
 175                         offset += sizeof(uint32_t);     /* id */
 176                         offset += lib_ring_buffer_align(offset, lttng_alignof(uint64_t));
 177                         offset += sizeof(uint64_t);     /* timestamp */
 178                 }
 179                 break;
 180         default:
 181                 padding = 0;
 182                 WARN_ON_ONCE(1);
 183         }
 184         offset += ctx_get_aligned_size(offset, lttng_chan->ctx,
 185                         client_ctx->packet_context_len);
 186         offset += ctx_get_aligned_size(offset, event->ctx,
 187                         client_ctx->event_context_len);
 188
 189         *pre_header_padding = padding;
 190         return offset - orig_offset;
 191 }
 192
 193 #include <ringbuffer/api.h>
 194
 195 static
 196 void lttng_write_event_header_slow(const struct lib_ring_buffer_config *config,
 197                                  struct lib_ring_buffer_ctx *ctx,
 198                                  uint32_t event_id);
 199
 200 /*
 201  * lttng_write_event_header
 202  *
 203  * Writes the event header to the offset (already aligned on 32-bits).
 204  *
 205  * @config: ring buffer instance configuration
 206  * @ctx: reservation context
 207  * @event_id: event ID
 208  */
 209 static __inline__
 210 void lttng_write_event_header(const struct lib_ring_buffer_config *config,
 211                             struct lib_ring_buffer_ctx *ctx,
 212                             uint32_t event_id)
 213 {
 214         struct lttng_channel *lttng_chan = channel_get_private(ctx->chan);
 215         struct lttng_probe_ctx *lttng_probe_ctx = ctx->priv;
 216         struct lttng_event *event = lttng_probe_ctx->event;
 217
 218         if (unlikely(ctx->rflags))
 219                 goto slow_path;
 220
 221         switch (lttng_chan->header_type) {
 222         case 1: /* compact */
 223         {
 224                 uint32_t id_time = 0;
 225
 226                 bt_bitfield_write(&id_time, uint32_t,
 227                                 0,
 228                                 LTTNG_COMPACT_EVENT_BITS,
 229                                 event_id);
 230                 bt_bitfield_write(&id_time, uint32_t,
 231                                 LTTNG_COMPACT_EVENT_BITS,
 232                                 LTTNG_COMPACT_TSC_BITS,
 233                                 ctx->tsc);
 234                 lib_ring_buffer_write(config, ctx, &id_time, sizeof(id_time));
 235                 break;
 236         }
 237         case 2: /* large */
 238         {
 239                 uint32_t timestamp = (uint32_t) ctx->tsc;
 240                 uint16_t id = event_id;
 241
 242                 lib_ring_buffer_write(config, ctx, &id, sizeof(id));
 243                 lib_ring_buffer_align_ctx(ctx, lttng_alignof(uint32_t));
 244                 lib_ring_buffer_write(config, ctx, &timestamp, sizeof(timestamp));
 245                 break;
 246         }
 247         default:
 248                 WARN_ON_ONCE(1);
 249         }
 250
 251         ctx_record(ctx, lttng_chan, lttng_chan->ctx);
 252         ctx_record(ctx, lttng_chan, event->ctx);
 253         lib_ring_buffer_align_ctx(ctx, ctx->largest_align);
 254
 255         return;
 256
 257 slow_path:
 258         lttng_write_event_header_slow(config, ctx, event_id);
 259 }
 260
 261 static
 262 void lttng_write_event_header_slow(const struct lib_ring_buffer_config *config,
 263                                  struct lib_ring_buffer_ctx *ctx,
 264                                  uint32_t event_id)
 265 {
 266         struct lttng_channel *lttng_chan = channel_get_private(ctx->chan);
 267         struct lttng_probe_ctx *lttng_probe_ctx = ctx->priv;
 268         struct lttng_event *event = lttng_probe_ctx->event;
 269
 270         switch (lttng_chan->header_type) {
 271         case 1: /* compact */
 272                 if (!(ctx->rflags & (RING_BUFFER_RFLAG_FULL_TSC | LTTNG_RFLAG_EXTENDED))) {
 273                         uint32_t id_time = 0;
 274
 275                         bt_bitfield_write(&id_time, uint32_t,
 276                                         0,
 277                                         LTTNG_COMPACT_EVENT_BITS,
 278                                         event_id);
 279                         bt_bitfield_write(&id_time, uint32_t,
 280                                         LTTNG_COMPACT_EVENT_BITS,
 281                                         LTTNG_COMPACT_TSC_BITS, ctx->tsc);
 282                         lib_ring_buffer_write(config, ctx, &id_time, sizeof(id_time));
 283                 } else {
 284                         uint8_t id = 0;
 285                         uint64_t timestamp = ctx->tsc;
 286
 287                         bt_bitfield_write(&id, uint8_t,
 288                                         0,
 289                                         LTTNG_COMPACT_EVENT_BITS,
 290                                         31);
 291                         lib_ring_buffer_write(config, ctx, &id, sizeof(id));
 292                         /* Align extended struct on largest member */
 293                         lib_ring_buffer_align_ctx(ctx, lttng_alignof(uint64_t));
 294                         lib_ring_buffer_write(config, ctx, &event_id, sizeof(event_id));
 295                         lib_ring_buffer_align_ctx(ctx, lttng_alignof(uint64_t));
 296                         lib_ring_buffer_write(config, ctx, &timestamp, sizeof(timestamp));
 297                 }
 298                 break;
 299         case 2: /* large */
 300         {
 301                 if (!(ctx->rflags & (RING_BUFFER_RFLAG_FULL_TSC | LTTNG_RFLAG_EXTENDED))) {
 302                         uint32_t timestamp = (uint32_t) ctx->tsc;
 303                         uint16_t id = event_id;
 304
 305                         lib_ring_buffer_write(config, ctx, &id, sizeof(id));
 306                         lib_ring_buffer_align_ctx(ctx, lttng_alignof(uint32_t));
 307                         lib_ring_buffer_write(config, ctx, &timestamp, sizeof(timestamp));
 308                 } else {
 309                         uint16_t id = 65535;
 310                         uint64_t timestamp = ctx->tsc;
 311
 312                         lib_ring_buffer_write(config, ctx, &id, sizeof(id));
 313                         /* Align extended struct on largest member */
 314                         lib_ring_buffer_align_ctx(ctx, lttng_alignof(uint64_t));
 315                         lib_ring_buffer_write(config, ctx, &event_id, sizeof(event_id));
 316                         lib_ring_buffer_align_ctx(ctx, lttng_alignof(uint64_t));
 317                         lib_ring_buffer_write(config, ctx, &timestamp, sizeof(timestamp));
 318                 }
 319                 break;
 320         }
 321         default:
 322                 WARN_ON_ONCE(1);
 323         }
 324         ctx_record(ctx, lttng_chan, lttng_chan->ctx);
 325         ctx_record(ctx, lttng_chan, event->ctx);
 326         lib_ring_buffer_align_ctx(ctx, ctx->largest_align);
 327 }
 328
 329 static const struct lib_ring_buffer_config client_config;
 330
 331 static u64 client_ring_buffer_clock_read(struct channel *chan)
 332 {
 333         return lib_ring_buffer_clock_read(chan);
 334 }
 335
 336 static
 337 size_t client_record_header_size(const struct lib_ring_buffer_config *config,
 338                                  struct channel *chan, size_t offset,
 339                                  size_t *pre_header_padding,
 340                                  struct lib_ring_buffer_ctx *ctx,
 341                                  void *client_ctx)
 342 {
 343         return record_header_size(config, chan, offset,
 344                                   pre_header_padding, ctx, client_ctx);
 345 }
 346
 347 /**
 348  * client_packet_header_size - called on buffer-switch to a new sub-buffer
 349  *
 350  * Return header size without padding after the structure. Don't use packed
 351  * structure because gcc generates inefficient code on some architectures
 352  * (powerpc, mips..)
 353  */
 354 static size_t client_packet_header_size(void)
 355 {
 356         return offsetof(struct packet_header, ctx.header_end);
 357 }
 358
 359 static void client_buffer_begin(struct lib_ring_buffer *buf, u64 tsc,
 360                                 unsigned int subbuf_idx)
 361 {
 362         struct channel *chan = buf->backend.chan;
 363         struct packet_header *header =
 364                 (struct packet_header *)
 365                         lib_ring_buffer_offset_address(&buf->backend,
 366                                 subbuf_idx * chan->backend.subbuf_size);
 367         struct lttng_channel *lttng_chan = channel_get_private(chan);
 368         struct lttng_session *session = lttng_chan->session;
 369
 370         header->magic = CTF_MAGIC_NUMBER;
 371         memcpy(header->uuid, session->uuid.b, sizeof(session->uuid));
 372         header->stream_id = lttng_chan->id;
 373         header->stream_instance_id = buf->backend.cpu;
 374         header->ctx.timestamp_begin = tsc;
 375         header->ctx.timestamp_end = 0;
 376         header->ctx.content_size = ~0ULL; /* for debugging */
 377         header->ctx.packet_size = ~0ULL;
 378         header->ctx.packet_seq_num = chan->backend.num_subbuf * \
 379                                      buf->backend.buf_cnt[subbuf_idx].seq_cnt + \
 380                                      subbuf_idx;
 381         header->ctx.events_discarded = 0;
 382         header->ctx.cpu_id = buf->backend.cpu;
 383 }
 384
 385 /*
 386  * offset is assumed to never be 0 here : never deliver a completely empty
 387  * subbuffer. data_size is between 1 and subbuf_size.
 388  */
 389 static void client_buffer_end(struct lib_ring_buffer *buf, u64 tsc,
 390                               unsigned int subbuf_idx, unsigned long data_size)
 391 {
 392         struct channel *chan = buf->backend.chan;
 393         struct packet_header *header =
 394                 (struct packet_header *)
 395                         lib_ring_buffer_offset_address(&buf->backend,
 396                                 subbuf_idx * chan->backend.subbuf_size);
 397         unsigned long records_lost = 0;
 398
 399         header->ctx.timestamp_end = tsc;
 400         header->ctx.content_size =
 401                 (uint64_t) data_size * CHAR_BIT;                /* in bits */
 402         header->ctx.packet_size =
 403                 (uint64_t) PAGE_ALIGN(data_size) * CHAR_BIT;    /* in bits */
 404         records_lost += lib_ring_buffer_get_records_lost_full(&client_config, buf);
 405         records_lost += lib_ring_buffer_get_records_lost_wrap(&client_config, buf);
 406         records_lost += lib_ring_buffer_get_records_lost_big(&client_config, buf);
 407         header->ctx.events_discarded = records_lost;
 408 }
 409
 410 static int client_buffer_create(struct lib_ring_buffer *buf, void *priv,
 411                                 int cpu, const char *name)
 412 {
 413         return 0;
 414 }
 415
 416 static void client_buffer_finalize(struct lib_ring_buffer *buf, void *priv, int cpu)
 417 {
 418 }
 419
 420 static struct packet_header *client_packet_header(
 421                 const struct lib_ring_buffer_config *config,
 422                 struct lib_ring_buffer *buf)
 423 {
 424         return lib_ring_buffer_read_offset_address(&buf->backend, 0);
 425 }
 426
 427 static int client_timestamp_begin(const struct lib_ring_buffer_config *config,
 428                 struct lib_ring_buffer *buf,
 429                 uint64_t *timestamp_begin)
 430 {
 431         struct packet_header *header = client_packet_header(config, buf);
 432         *timestamp_begin = header->ctx.timestamp_begin;
 433
 434         return 0;
 435 }
 436
 437 static int client_timestamp_end(const struct lib_ring_buffer_config *config,
 438                         struct lib_ring_buffer *buf,
 439                         uint64_t *timestamp_end)
 440 {
 441         struct packet_header *header = client_packet_header(config, buf);
 442         *timestamp_end = header->ctx.timestamp_end;
 443
 444         return 0;
 445 }
 446
 447 static int client_events_discarded(const struct lib_ring_buffer_config *config,
 448                         struct lib_ring_buffer *buf,
 449                         uint64_t *events_discarded)
 450 {
 451         struct packet_header *header = client_packet_header(config, buf);
 452         *events_discarded = header->ctx.events_discarded;
 453
 454         return 0;
 455 }
 456
 457 static int client_content_size(const struct lib_ring_buffer_config *config,
 458                         struct lib_ring_buffer *buf,
 459                         uint64_t *content_size)
 460 {
 461         struct packet_header *header = client_packet_header(config, buf);
 462         *content_size = header->ctx.content_size;
 463
 464         return 0;
 465 }
 466
 467 static int client_packet_size(const struct lib_ring_buffer_config *config,
 468                         struct lib_ring_buffer *buf,
 469                         uint64_t *packet_size)
 470 {
 471         struct packet_header *header = client_packet_header(config, buf);
 472         *packet_size = header->ctx.packet_size;
 473
 474         return 0;
 475 }
 476
 477 static int client_stream_id(const struct lib_ring_buffer_config *config,
 478                         struct lib_ring_buffer *buf,
 479                         uint64_t *stream_id)
 480 {
 481         struct channel *chan = buf->backend.chan;
 482         struct lttng_channel *lttng_chan = channel_get_private(chan);
 483
 484         *stream_id = lttng_chan->id;
 485         return 0;
 486 }
 487
 488 static int client_current_timestamp(const struct lib_ring_buffer_config *config,
 489                 struct lib_ring_buffer *bufb,
 490                 uint64_t *ts)
 491 {
 492         *ts = config->cb.ring_buffer_clock_read(bufb->backend.chan);
 493
 494         return 0;
 495 }
 496
 497 static int client_sequence_number(const struct lib_ring_buffer_config *config,
 498                         struct lib_ring_buffer *buf,
 499                         uint64_t *seq)
 500 {
 501         struct packet_header *header = client_packet_header(config, buf);
 502
 503         *seq = header->ctx.packet_seq_num;
 504
 505         return 0;
 506 }
 507
 508 static
 509 int client_instance_id(const struct lib_ring_buffer_config *config,
 510                 struct lib_ring_buffer *buf,
 511                 uint64_t *id)
 512 {
 513         *id = buf->backend.cpu;
 514
 515         return 0;
 516 }
 517
 518 static const struct lib_ring_buffer_config client_config = {
 519         .cb.ring_buffer_clock_read = client_ring_buffer_clock_read,
 520         .cb.record_header_size = client_record_header_size,
 521         .cb.subbuffer_header_size = client_packet_header_size,
 522         .cb.buffer_begin = client_buffer_begin,
 523         .cb.buffer_end = client_buffer_end,
 524         .cb.buffer_create = client_buffer_create,
 525         .cb.buffer_finalize = client_buffer_finalize,
 526
 527         .tsc_bits = LTTNG_COMPACT_TSC_BITS,
 528         .alloc = RING_BUFFER_ALLOC_PER_CPU,
 529         .sync = RING_BUFFER_SYNC_PER_CPU,
 530         .mode = RING_BUFFER_MODE_TEMPLATE,
 531         .backend = RING_BUFFER_PAGE,
 532         .output = RING_BUFFER_OUTPUT_TEMPLATE,
 533         .oops = RING_BUFFER_OOPS_CONSISTENCY,
 534         .ipi = RING_BUFFER_IPI_BARRIER,
 535         .wakeup = RING_BUFFER_WAKEUP_BY_TIMER,
 536 };
 537
 538 static
 539 void release_priv_ops(void *priv_ops)
 540 {
 541         module_put(THIS_MODULE);
 542 }
 543
 544 static
 545 void lttng_channel_destroy(struct channel *chan)
 546 {
 547         channel_destroy(chan);
 548 }
 549
 550 static
 551 struct channel *_channel_create(const char *name,
 552                                 struct lttng_channel *lttng_chan, void *buf_addr,
 553                                 size_t subbuf_size, size_t num_subbuf,
 554                                 unsigned int switch_timer_interval,
 555                                 unsigned int read_timer_interval)
 556 {
 557         struct channel *chan;
 558
 559         chan = channel_create(&client_config, name, lttng_chan, buf_addr,
 560                               subbuf_size, num_subbuf, switch_timer_interval,
 561                               read_timer_interval);
 562         if (chan) {
 563                 /*
 564                  * Ensure this module is not unloaded before we finish
 565                  * using lttng_relay_transport.ops.
 566                  */
 567                 if (!try_module_get(THIS_MODULE)) {
 568                         printk(KERN_WARNING "LTT : Can't lock transport module.\n");
 569                         goto error;
 570                 }
 571                 chan->backend.priv_ops = &lttng_relay_transport.ops;
 572                 chan->backend.release_priv_ops = release_priv_ops;
 573         }
 574         return chan;
 575
 576 error:
 577         lttng_channel_destroy(chan);
 578         return NULL;
 579 }
 580
 581 static
 582 struct lib_ring_buffer *lttng_buffer_read_open(struct channel *chan)
 583 {
 584         struct lib_ring_buffer *buf;
 585         int cpu;
 586
 587         for_each_channel_cpu(cpu, chan) {
 588                 buf = channel_get_ring_buffer(&client_config, chan, cpu);
 589                 if (!lib_ring_buffer_open_read(buf))
 590                         return buf;
 591         }
 592         return NULL;
 593 }
 594
 595 static
 596 int lttng_buffer_has_read_closed_stream(struct channel *chan)
 597 {
 598         struct lib_ring_buffer *buf;
 599         int cpu;
 600
 601         for_each_channel_cpu(cpu, chan) {
 602                 buf = channel_get_ring_buffer(&client_config, chan, cpu);
 603                 if (!atomic_long_read(&buf->active_readers))
 604                         return 1;
 605         }
 606         return 0;
 607 }
 608
 609 static
 610 void lttng_buffer_read_close(struct lib_ring_buffer *buf)
 611 {
 612         lib_ring_buffer_release_read(buf);
 613 }
 614
 615 static
 616 int lttng_event_reserve(struct lib_ring_buffer_ctx *ctx,
 617                       uint32_t event_id)
 618 {
 619         struct lttng_channel *lttng_chan = channel_get_private(ctx->chan);
 620         struct lttng_probe_ctx *lttng_probe_ctx = ctx->priv;
 621         struct lttng_event *event = lttng_probe_ctx->event;
 622         struct lttng_client_ctx client_ctx;
 623         int ret, cpu;
 624
 625         cpu = lib_ring_buffer_get_cpu(&client_config);
 626         if (unlikely(cpu < 0))
 627                 return -EPERM;
 628         ctx->cpu = cpu;
 629
 630         /* Compute internal size of context structures. */
 631         ctx_get_struct_size(lttng_chan->ctx, &client_ctx.packet_context_len, lttng_chan, ctx);
 632         ctx_get_struct_size(event->ctx, &client_ctx.event_context_len, lttng_chan, ctx);
 633
 634         switch (lttng_chan->header_type) {
 635         case 1: /* compact */
 636                 if (event_id > 30)
 637                         ctx->rflags |= LTTNG_RFLAG_EXTENDED;
 638                 break;
 639         case 2: /* large */
 640                 if (event_id > 65534)
 641                         ctx->rflags |= LTTNG_RFLAG_EXTENDED;
 642                 break;
 643         default:
 644                 WARN_ON_ONCE(1);
 645         }
 646
 647         ret = lib_ring_buffer_reserve(&client_config, ctx, &client_ctx);
 648         if (unlikely(ret))
 649                 goto put;
 650         lib_ring_buffer_backend_get_pages(&client_config, ctx,
 651                         &ctx->backend_pages);
 652         lttng_write_event_header(&client_config, ctx, event_id);
 653         return 0;
 654 put:
 655         lib_ring_buffer_put_cpu(&client_config);
 656         return ret;
 657 }
 658
 659 static
 660 void lttng_event_commit(struct lib_ring_buffer_ctx *ctx)
 661 {
 662         lib_ring_buffer_commit(&client_config, ctx);
 663         lib_ring_buffer_put_cpu(&client_config);
 664 }
 665
 666 static
 667 void lttng_event_write(struct lib_ring_buffer_ctx *ctx, const void *src,
 668                      size_t len)
 669 {
 670         lib_ring_buffer_write(&client_config, ctx, src, len);
 671 }
 672
 673 static
 674 void lttng_event_write_from_user(struct lib_ring_buffer_ctx *ctx,
 675                                const void __user *src, size_t len)
 676 {
 677         lib_ring_buffer_copy_from_user_inatomic(&client_config, ctx, src, len);
 678 }
 679
 680 static
 681 void lttng_event_memset(struct lib_ring_buffer_ctx *ctx,
 682                 int c, size_t len)
 683 {
 684         lib_ring_buffer_memset(&client_config, ctx, c, len);
 685 }
 686
 687 static
 688 void lttng_event_strcpy(struct lib_ring_buffer_ctx *ctx, const char *src,
 689                 size_t len)
 690 {
 691         lib_ring_buffer_strcpy(&client_config, ctx, src, len, '#');
 692 }
 693
 694 static
 695 void lttng_event_strcpy_from_user(struct lib_ring_buffer_ctx *ctx,
 696                 const char __user *src, size_t len)
 697 {
 698         lib_ring_buffer_strcpy_from_user_inatomic(&client_config, ctx, src,
 699                         len, '#');
 700 }
 701
 702 static
 703 wait_queue_head_t *lttng_get_writer_buf_wait_queue(struct channel *chan, int cpu)
 704 {
 705         struct lib_ring_buffer *buf = channel_get_ring_buffer(&client_config,
 706                                         chan, cpu);
 707         return &buf->write_wait;
 708 }
 709
 710 static
 711 wait_queue_head_t *lttng_get_hp_wait_queue(struct channel *chan)
 712 {
 713         return &chan->hp_wait;
 714 }
 715
 716 static
 717 int lttng_is_finalized(struct channel *chan)
 718 {
 719         return lib_ring_buffer_channel_is_finalized(chan);
 720 }
 721
 722 static
 723 int lttng_is_disabled(struct channel *chan)
 724 {
 725         return lib_ring_buffer_channel_is_disabled(chan);
 726 }
 727
 728 static struct lttng_transport lttng_relay_transport = {
 729         .name = "relay-" RING_BUFFER_MODE_TEMPLATE_STRING,
 730         .owner = THIS_MODULE,
 731         .ops = {
 732                 .channel_create = _channel_create,
 733                 .channel_destroy = lttng_channel_destroy,
 734                 .buffer_read_open = lttng_buffer_read_open,
 735                 .buffer_has_read_closed_stream =
 736                         lttng_buffer_has_read_closed_stream,
 737                 .buffer_read_close = lttng_buffer_read_close,
 738                 .event_reserve = lttng_event_reserve,
 739                 .event_commit = lttng_event_commit,
 740                 .event_write = lttng_event_write,
 741                 .event_write_from_user = lttng_event_write_from_user,
 742                 .event_memset = lttng_event_memset,
 743                 .event_strcpy = lttng_event_strcpy,
 744                 .event_strcpy_from_user = lttng_event_strcpy_from_user,
 745                 .packet_avail_size = NULL,      /* Would be racy anyway */
 746                 .get_writer_buf_wait_queue = lttng_get_writer_buf_wait_queue,
 747                 .get_hp_wait_queue = lttng_get_hp_wait_queue,
 748                 .is_finalized = lttng_is_finalized,
 749                 .is_disabled = lttng_is_disabled,
 750                 .timestamp_begin = client_timestamp_begin,
 751                 .timestamp_end = client_timestamp_end,
 752                 .events_discarded = client_events_discarded,
 753                 .content_size = client_content_size,
 754                 .packet_size = client_packet_size,
 755                 .stream_id = client_stream_id,
 756                 .current_timestamp = client_current_timestamp,
 757                 .sequence_number = client_sequence_number,
 758                 .instance_id = client_instance_id,
 759         },
 760 };
 761
 762 static int __init lttng_ring_buffer_client_init(void)
 763 {
 764         lttng_transport_register(&lttng_relay_transport);
 765         return 0;
 766 }
 767
 768 module_init(lttng_ring_buffer_client_init);
 769
 770 static void __exit lttng_ring_buffer_client_exit(void)
 771 {
 772         lttng_transport_unregister(&lttng_relay_transport);
 773 }
 774
 775 module_exit(lttng_ring_buffer_client_exit);
 776
 777 MODULE_LICENSE("GPL and additional rights");
 778 MODULE_AUTHOR("Mathieu Desnoyers <mathieu.desnoyers@efficios.com>");
 779 MODULE_DESCRIPTION("LTTng ring buffer " RING_BUFFER_MODE_TEMPLATE_STRING
 780                    " client");
 781 MODULE_VERSION(__stringify(LTTNG_MODULES_MAJOR_VERSION) "."
 782         __stringify(LTTNG_MODULES_MINOR_VERSION) "."
 783         __stringify(LTTNG_MODULES_PATCHLEVEL_VERSION)
 784         LTTNG_MODULES_EXTRAVERSION);