libringbuffer/ring_buffer_iterator.c

   1 /*
   2  * ring_buffer_iterator.c
   3  *
   4  * (C) Copyright 2010 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   5  *
   6  * Ring buffer and channel iterators. Get each event of a channel in order. Uses
   7  * a prio heap for per-cpu buffers, giving a O(log(NR_CPUS)) algorithmic
   8  * complexity for the "get next event" operation.
   9  *
  10  * Author:
  11  *      Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
  12  *
  13  * Dual LGPL v2.1/GPL v2 license.
  14  */
  15
  16 #include "iterator.h"
  17
  18 /*
  19  * Safety factor taking into account internal kernel interrupt latency.
  20  * Assuming 250ms worse-case latency.
  21  */
  22 #define MAX_SYSTEM_LATENCY      250
  23
  24 /*
  25  * Maximum delta expected between trace clocks. At most 1 jiffy delta.
  26  */
  27 #define MAX_CLOCK_DELTA         (jiffies_to_usecs(1) * 1000)
  28
  29 /**
  30  * lib_ring_buffer_get_next_record - Get the next record in a buffer.
  31  * @chan: channel
  32  * @buf: buffer
  33  *
  34  * Returns the size of the event read, -EAGAIN if buffer is empty, -ENODATA if
  35  * buffer is empty and finalized. The buffer must already be opened for reading.
  36  */
  37 ssize_t lib_ring_buffer_get_next_record(struct channel *chan,
  38                                         struct lib_ring_buffer *buf)
  39 {
  40         const struct lib_ring_buffer_config *config = chan->backend.config;
  41         struct lib_ring_buffer_iter *iter = &buf->iter;
  42         int ret;
  43
  44 restart:
  45         switch (iter->state) {
  46         case ITER_GET_SUBBUF:
  47                 ret = lib_ring_buffer_get_next_subbuf(buf);
  48                 if (ret && !ACCESS_ONCE(buf->finalized)
  49                     && config->alloc == RING_BUFFER_ALLOC_GLOBAL) {
  50                         /*
  51                          * Use "pull" scheme for global buffers. The reader
  52                          * itself flushes the buffer to "pull" data not visible
  53                          * to readers yet. Flush current subbuffer and re-try.
  54                          *
  55                          * Per-CPU buffers rather use a "push" scheme because
  56                          * the IPI needed to flush all CPU's buffers is too
  57                          * costly. In the "push" scheme, the reader waits for
  58                          * the writer periodic deferrable timer to flush the
  59                          * buffers (keeping track of a quiescent state
  60                          * timestamp). Therefore, the writer "pushes" data out
  61                          * of the buffers rather than letting the reader "pull"
  62                          * data from the buffer.
  63                          */
  64                         lib_ring_buffer_switch_slow(buf, SWITCH_ACTIVE);
  65                         ret = lib_ring_buffer_get_next_subbuf(buf);
  66                 }
  67                 if (ret)
  68                         return ret;
  69                 iter->consumed = buf->cons_snapshot;
  70                 iter->data_size = lib_ring_buffer_get_read_data_size(config, buf);
  71                 iter->read_offset = iter->consumed;
  72                 /* skip header */
  73                 iter->read_offset += config->cb.subbuffer_header_size();
  74                 iter->state = ITER_TEST_RECORD;
  75                 goto restart;
  76         case ITER_TEST_RECORD:
  77                 if (iter->read_offset - iter->consumed >= iter->data_size) {
  78                         iter->state = ITER_PUT_SUBBUF;
  79                 } else {
  80                         CHAN_WARN_ON(chan, !config->cb.record_get);
  81                         config->cb.record_get(config, chan, buf,
  82                                               iter->read_offset,
  83                                               &iter->header_len,
  84                                               &iter->payload_len,
  85                                               &iter->timestamp);
  86                         iter->read_offset += iter->header_len;
  87                         subbuffer_consume_record(config, &buf->backend);
  88                         iter->state = ITER_NEXT_RECORD;
  89                         return iter->payload_len;
  90                 }
  91                 goto restart;
  92         case ITER_NEXT_RECORD:
  93                 iter->read_offset += iter->payload_len;
  94                 iter->state = ITER_TEST_RECORD;
  95                 goto restart;
  96         case ITER_PUT_SUBBUF:
  97                 lib_ring_buffer_put_next_subbuf(buf);
  98                 iter->state = ITER_GET_SUBBUF;
  99                 goto restart;
 100         default:
 101                 CHAN_WARN_ON(chan, 1);  /* Should not happen */
 102                 return -EPERM;
 103         }
 104 }
 105 EXPORT_SYMBOL_GPL(lib_ring_buffer_get_next_record);
 106
 107 static int buf_is_higher(void *a, void *b)
 108 {
 109         struct lib_ring_buffer *bufa = a;
 110         struct lib_ring_buffer *bufb = b;
 111
 112         /* Consider lowest timestamps to be at the top of the heap */
 113         return (bufa->iter.timestamp < bufb->iter.timestamp);
 114 }
 115
 116 static
 117 void lib_ring_buffer_get_empty_buf_records(const struct lib_ring_buffer_config *config,
 118                                            struct channel *chan)
 119 {
 120         struct lttng_ptr_heap *heap = &chan->iter.heap;
 121         struct lib_ring_buffer *buf, *tmp;
 122         ssize_t len;
 123
 124         list_for_each_entry_safe(buf, tmp, &chan->iter.empty_head,
 125                                  iter.empty_node) {
 126                 len = lib_ring_buffer_get_next_record(chan, buf);
 127
 128                 /*
 129                  * Deal with -EAGAIN and -ENODATA.
 130                  * len >= 0 means record contains data.
 131                  * -EBUSY should never happen, because we support only one
 132                  * reader.
 133                  */
 134                 switch (len) {
 135                 case -EAGAIN:
 136                         /* Keep node in empty list */
 137                         break;
 138                 case -ENODATA:
 139                         /*
 140                          * Buffer is finalized. Don't add to list of empty
 141                          * buffer, because it has no more data to provide, ever.
 142                          */
 143                         list_del(&buf->iter.empty_node);
 144                         break;
 145                 case -EBUSY:
 146                         CHAN_WARN_ON(chan, 1);
 147                         break;
 148                 default:
 149                         /*
 150                          * Insert buffer into the heap, remove from empty buffer
 151                          * list.
 152                          */
 153                         CHAN_WARN_ON(chan, len < 0);
 154                         list_del(&buf->iter.empty_node);
 155                         CHAN_WARN_ON(chan, lttng_heap_insert(heap, buf));
 156                 }
 157         }
 158 }
 159
 160 static
 161 void lib_ring_buffer_wait_for_qs(const struct lib_ring_buffer_config *config,
 162                                  struct channel *chan)
 163 {
 164         u64 timestamp_qs;
 165         unsigned long wait_msecs;
 166
 167         /*
 168          * No need to wait if no empty buffers are present.
 169          */
 170         if (list_empty(&chan->iter.empty_head))
 171                 return;
 172
 173         timestamp_qs = config->cb.ring_buffer_clock_read(chan);
 174         /*
 175          * We need to consider previously empty buffers.
 176          * Do a get next buf record on each of them. Add them to
 177          * the heap if they have data. If at least one of them
 178          * don't have data, we need to wait for
 179          * switch_timer_interval + MAX_SYSTEM_LATENCY (so we are sure the
 180          * buffers have been switched either by the timer or idle entry) and
 181          * check them again, adding them if they have data.
 182          */
 183         lib_ring_buffer_get_empty_buf_records(config, chan);
 184
 185         /*
 186          * No need to wait if no empty buffers are present.
 187          */
 188         if (list_empty(&chan->iter.empty_head))
 189                 return;
 190
 191         /*
 192          * We need to wait for the buffer switch timer to run. If the
 193          * CPU is idle, idle entry performed the switch.
 194          * TODO: we could optimize further by skipping the sleep if all
 195          * empty buffers belong to idle or offline cpus.
 196          */
 197         wait_msecs = jiffies_to_msecs(chan->switch_timer_interval);
 198         wait_msecs += MAX_SYSTEM_LATENCY;
 199         msleep(wait_msecs);
 200         lib_ring_buffer_get_empty_buf_records(config, chan);
 201         /*
 202          * Any buffer still in the empty list here cannot possibly
 203          * contain an event with a timestamp prior to "timestamp_qs".
 204          * The new quiescent state timestamp is the one we grabbed
 205          * before waiting for buffer data.  It is therefore safe to
 206          * ignore empty buffers up to last_qs timestamp for fusion
 207          * merge.
 208          */
 209         chan->iter.last_qs = timestamp_qs;
 210 }
 211
 212 /**
 213  * channel_get_next_record - Get the next record in a channel.
 214  * @chan: channel
 215  * @ret_buf: the buffer in which the event is located (output)
 216  *
 217  * Returns the size of new current event, -EAGAIN if all buffers are empty,
 218  * -ENODATA if all buffers are empty and finalized. The channel must already be
 219  * opened for reading.
 220  */
 221
 222 ssize_t channel_get_next_record(struct channel *chan,
 223                                 struct lib_ring_buffer **ret_buf)
 224 {
 225         const struct lib_ring_buffer_config *config = chan->backend.config;
 226         struct lib_ring_buffer *buf;
 227         struct lttng_ptr_heap *heap;
 228         ssize_t len;
 229
 230         if (config->alloc == RING_BUFFER_ALLOC_GLOBAL) {
 231                 *ret_buf = channel_get_ring_buffer(config, chan, 0);
 232                 return lib_ring_buffer_get_next_record(chan, *ret_buf);
 233         }
 234
 235         heap = &chan->iter.heap;
 236
 237         /*
 238          * get next record for topmost buffer.
 239          */
 240         buf = lttng_heap_maximum(heap);
 241         if (buf) {
 242                 len = lib_ring_buffer_get_next_record(chan, buf);
 243                 /*
 244                  * Deal with -EAGAIN and -ENODATA.
 245                  * len >= 0 means record contains data.
 246                  */
 247                 switch (len) {
 248                 case -EAGAIN:
 249                         buf->iter.timestamp = 0;
 250                         list_add(&buf->iter.empty_node, &chan->iter.empty_head);
 251                         /* Remove topmost buffer from the heap */
 252                         CHAN_WARN_ON(chan, lttng_heap_remove(heap) != buf);
 253                         break;
 254                 case -ENODATA:
 255                         /*
 256                          * Buffer is finalized. Remove buffer from heap and
 257                          * don't add to list of empty buffer, because it has no
 258                          * more data to provide, ever.
 259                          */
 260                         CHAN_WARN_ON(chan, lttng_heap_remove(heap) != buf);
 261                         break;
 262                 case -EBUSY:
 263                         CHAN_WARN_ON(chan, 1);
 264                         break;
 265                 default:
 266                         /*
 267                          * Reinsert buffer into the heap. Note that heap can be
 268                          * partially empty, so we need to use
 269                          * lttng_heap_replace_max().
 270                          */
 271                         CHAN_WARN_ON(chan, len < 0);
 272                         CHAN_WARN_ON(chan, lttng_heap_replace_max(heap, buf) != buf);
 273                         break;
 274                 }
 275         }
 276
 277         buf = lttng_heap_maximum(heap);
 278         if (!buf || buf->iter.timestamp > chan->iter.last_qs) {
 279                 /*
 280                  * Deal with buffers previously showing no data.
 281                  * Add buffers containing data to the heap, update
 282                  * last_qs.
 283                  */
 284                 lib_ring_buffer_wait_for_qs(config, chan);
 285         }
 286
 287         *ret_buf = buf = lttng_heap_maximum(heap);
 288         if (buf) {
 289                 /*
 290                  * If this warning triggers, you probably need to check your
 291                  * system interrupt latency. Typical causes: too many printk()
 292                  * output going to a serial console with interrupts off.
 293                  * Allow for MAX_CLOCK_DELTA ns timestamp delta going backward.
 294                  * Observed on SMP KVM setups with trace_clock().
 295                  */
 296                 if (chan->iter.last_timestamp
 297                     > (buf->iter.timestamp + MAX_CLOCK_DELTA)) {
 298                         printk(KERN_WARNING "ring_buffer: timestamps going "
 299                                "backward. Last time %llu ns, cpu %d, "
 300                                "current time %llu ns, cpu %d, "
 301                                "delta %llu ns.\n",
 302                                chan->iter.last_timestamp, chan->iter.last_cpu,
 303                                buf->iter.timestamp, buf->backend.cpu,
 304                                chan->iter.last_timestamp - buf->iter.timestamp);
 305                         CHAN_WARN_ON(chan, 1);
 306                 }
 307                 chan->iter.last_timestamp = buf->iter.timestamp;
 308                 chan->iter.last_cpu = buf->backend.cpu;
 309                 return buf->iter.payload_len;
 310         } else {
 311                 /* Heap is empty */
 312                 if (list_empty(&chan->iter.empty_head))
 313                         return -ENODATA;        /* All buffers finalized */
 314                 else
 315                         return -EAGAIN;         /* Temporarily empty */
 316         }
 317 }
 318 EXPORT_SYMBOL_GPL(channel_get_next_record);
 319
 320 static
 321 void lib_ring_buffer_iterator_init(struct channel *chan, struct lib_ring_buffer *buf)
 322 {
 323         if (buf->iter.allocated)
 324                 return;
 325
 326         buf->iter.allocated = 1;
 327         if (chan->iter.read_open && !buf->iter.read_open) {
 328                 CHAN_WARN_ON(chan, lib_ring_buffer_open_read(buf) != 0);
 329                 buf->iter.read_open = 1;
 330         }
 331
 332         /* Add to list of buffers without any current record */
 333         if (chan->backend.config->alloc == RING_BUFFER_ALLOC_PER_CPU)
 334                 list_add(&buf->iter.empty_node, &chan->iter.empty_head);
 335 }
 336
 337 #ifdef CONFIG_HOTPLUG_CPU
 338 static
 339 int __cpuinit channel_iterator_cpu_hotplug(struct notifier_block *nb,
 340                                            unsigned long action,
 341                                            void *hcpu)
 342 {
 343         unsigned int cpu = (unsigned long)hcpu;
 344         struct channel *chan = container_of(nb, struct channel,
 345                                             hp_iter_notifier);
 346         struct lib_ring_buffer *buf = per_cpu_ptr(chan->backend.buf, cpu);
 347         const struct lib_ring_buffer_config *config = chan->backend.config;
 348
 349         if (!chan->hp_iter_enable)
 350                 return NOTIFY_DONE;
 351
 352         CHAN_WARN_ON(chan, config->alloc == RING_BUFFER_ALLOC_GLOBAL);
 353
 354         switch (action) {
 355         case CPU_DOWN_FAILED:
 356         case CPU_DOWN_FAILED_FROZEN:
 357         case CPU_ONLINE:
 358         case CPU_ONLINE_FROZEN:
 359                 lib_ring_buffer_iterator_init(chan, buf);
 360                 return NOTIFY_OK;
 361         default:
 362                 return NOTIFY_DONE;
 363         }
 364 }
 365 #endif
 366
 367 int channel_iterator_init(struct channel *chan)
 368 {
 369         const struct lib_ring_buffer_config *config = chan->backend.config;
 370         struct lib_ring_buffer *buf;
 371
 372         if (config->alloc == RING_BUFFER_ALLOC_PER_CPU) {
 373                 int cpu, ret;
 374
 375                 INIT_LIST_HEAD(&chan->iter.empty_head);
 376                 ret = lttng_heap_init(&chan->iter.heap,
 377                                 num_possible_cpus(),
 378                                 GFP_KERNEL, buf_is_higher);
 379                 if (ret)
 380                         return ret;
 381                 /*
 382                  * In case of non-hotplug cpu, if the ring-buffer is allocated
 383                  * in early initcall, it will not be notified of secondary cpus.
 384                  * In that off case, we need to allocate for all possible cpus.
 385                  */
 386 #ifdef CONFIG_HOTPLUG_CPU
 387                 chan->hp_iter_notifier.notifier_call =
 388                         channel_iterator_cpu_hotplug;
 389                 chan->hp_iter_notifier.priority = 10;
 390                 register_cpu_notifier(&chan->hp_iter_notifier);
 391                 get_online_cpus();
 392                 for_each_online_cpu(cpu) {
 393                         buf = per_cpu_ptr(chan->backend.buf, cpu);
 394                         lib_ring_buffer_iterator_init(chan, buf);
 395                 }
 396                 chan->hp_iter_enable = 1;
 397                 put_online_cpus();
 398 #else
 399                 for_each_possible_cpu(cpu) {
 400                         buf = per_cpu_ptr(chan->backend.buf, cpu);
 401                         lib_ring_buffer_iterator_init(chan, buf);
 402                 }
 403 #endif
 404         } else {
 405                 buf = channel_get_ring_buffer(config, chan, 0);
 406                 lib_ring_buffer_iterator_init(chan, buf);
 407         }
 408         return 0;
 409 }
 410
 411 void channel_iterator_unregister_notifiers(struct channel *chan)
 412 {
 413         const struct lib_ring_buffer_config *config = chan->backend.config;
 414
 415         if (config->alloc == RING_BUFFER_ALLOC_PER_CPU) {
 416                 chan->hp_iter_enable = 0;
 417                 unregister_cpu_notifier(&chan->hp_iter_notifier);
 418         }
 419 }
 420
 421 void channel_iterator_free(struct channel *chan)
 422 {
 423         const struct lib_ring_buffer_config *config = chan->backend.config;
 424
 425         if (config->alloc == RING_BUFFER_ALLOC_PER_CPU)
 426                 lttng_heap_free(&chan->iter.heap);
 427 }
 428
 429 int lib_ring_buffer_iterator_open(struct lib_ring_buffer *buf)
 430 {
 431         struct channel *chan = buf->backend.chan;
 432         const struct lib_ring_buffer_config *config = chan->backend.config;
 433         CHAN_WARN_ON(chan, config->output != RING_BUFFER_ITERATOR);
 434         return lib_ring_buffer_open_read(buf);
 435 }
 436 EXPORT_SYMBOL_GPL(lib_ring_buffer_iterator_open);
 437
 438 /*
 439  * Note: Iterators must not be mixed with other types of outputs, because an
 440  * iterator can leave the buffer in "GET" state, which is not consistent with
 441  * other types of output (mmap, splice, raw data read).
 442  */
 443 void lib_ring_buffer_iterator_release(struct lib_ring_buffer *buf)
 444 {
 445         lib_ring_buffer_release_read(buf);
 446 }
 447 EXPORT_SYMBOL_GPL(lib_ring_buffer_iterator_release);
 448
 449 int channel_iterator_open(struct channel *chan)
 450 {
 451         const struct lib_ring_buffer_config *config = chan->backend.config;
 452         struct lib_ring_buffer *buf;
 453         int ret = 0, cpu;
 454
 455         CHAN_WARN_ON(chan, config->output != RING_BUFFER_ITERATOR);
 456
 457         if (config->alloc == RING_BUFFER_ALLOC_PER_CPU) {
 458                 get_online_cpus();
 459                 /* Allow CPU hotplug to keep track of opened reader */
 460                 chan->iter.read_open = 1;
 461                 for_each_channel_cpu(cpu, chan) {
 462                         buf = channel_get_ring_buffer(config, chan, cpu);
 463                         ret = lib_ring_buffer_iterator_open(buf);
 464                         if (ret)
 465                                 goto error;
 466                         buf->iter.read_open = 1;
 467                 }
 468                 put_online_cpus();
 469         } else {
 470                 buf = channel_get_ring_buffer(config, chan, 0);
 471                 ret = lib_ring_buffer_iterator_open(buf);
 472         }
 473         return ret;
 474 error:
 475         /* Error should always happen on CPU 0, hence no close is required. */
 476         CHAN_WARN_ON(chan, cpu != 0);
 477         put_online_cpus();
 478         return ret;
 479 }
 480 EXPORT_SYMBOL_GPL(channel_iterator_open);
 481
 482 void channel_iterator_release(struct channel *chan)
 483 {
 484         const struct lib_ring_buffer_config *config = chan->backend.config;
 485         struct lib_ring_buffer *buf;
 486         int cpu;
 487
 488         if (config->alloc == RING_BUFFER_ALLOC_PER_CPU) {
 489                 get_online_cpus();
 490                 for_each_channel_cpu(cpu, chan) {
 491                         buf = channel_get_ring_buffer(config, chan, cpu);
 492                         if (buf->iter.read_open) {
 493                                 lib_ring_buffer_iterator_release(buf);
 494                                 buf->iter.read_open = 0;
 495                         }
 496                 }
 497                 chan->iter.read_open = 0;
 498                 put_online_cpus();
 499         } else {
 500                 buf = channel_get_ring_buffer(config, chan, 0);
 501                 lib_ring_buffer_iterator_release(buf);
 502         }
 503 }
 504 EXPORT_SYMBOL_GPL(channel_iterator_release);
 505
 506 void lib_ring_buffer_iterator_reset(struct lib_ring_buffer *buf)
 507 {
 508         struct channel *chan = buf->backend.chan;
 509
 510         if (buf->iter.state != ITER_GET_SUBBUF)
 511                 lib_ring_buffer_put_next_subbuf(buf);
 512         buf->iter.state = ITER_GET_SUBBUF;
 513         /* Remove from heap (if present). */
 514         if (lttng_heap_cherrypick(&chan->iter.heap, buf))
 515                 list_add(&buf->iter.empty_node, &chan->iter.empty_head);
 516         buf->iter.timestamp = 0;
 517         buf->iter.header_len = 0;
 518         buf->iter.payload_len = 0;
 519         buf->iter.consumed = 0;
 520         buf->iter.read_offset = 0;
 521         buf->iter.data_size = 0;
 522         /* Don't reset allocated and read_open */
 523 }
 524
 525 void channel_iterator_reset(struct channel *chan)
 526 {
 527         const struct lib_ring_buffer_config *config = chan->backend.config;
 528         struct lib_ring_buffer *buf;
 529         int cpu;
 530
 531         /* Empty heap, put into empty_head */
 532         while ((buf = lttng_heap_remove(&chan->iter.heap)) != NULL)
 533                 list_add(&buf->iter.empty_node, &chan->iter.empty_head);
 534
 535         for_each_channel_cpu(cpu, chan) {
 536                 buf = channel_get_ring_buffer(config, chan, cpu);
 537                 lib_ring_buffer_iterator_reset(buf);
 538         }
 539         /* Don't reset read_open */
 540         chan->iter.last_qs = 0;
 541         chan->iter.last_timestamp = 0;
 542         chan->iter.last_cpu = 0;
 543         chan->iter.len_left = 0;
 544 }
 545
 546 /*
 547  * Ring buffer payload extraction read() implementation.
 548  */
 549 static
 550 ssize_t channel_ring_buffer_file_read(struct file *filp,
 551                                       char __user *user_buf,
 552                                       size_t count,
 553                                       loff_t *ppos,
 554                                       struct channel *chan,
 555                                       struct lib_ring_buffer *buf,
 556                                       int fusionmerge)
 557 {
 558         const struct lib_ring_buffer_config *config = chan->backend.config;
 559         size_t read_count = 0, read_offset;
 560         ssize_t len;
 561
 562         might_sleep();
 563         if (!access_ok(VERIFY_WRITE, user_buf, count))
 564                 return -EFAULT;
 565
 566         /* Finish copy of previous record */
 567         if (*ppos != 0) {
 568                 if (read_count < count) {
 569                         len = chan->iter.len_left;
 570                         read_offset = *ppos;
 571                         if (config->alloc == RING_BUFFER_ALLOC_PER_CPU
 572                             && fusionmerge)
 573                                 buf = lttng_heap_maximum(&chan->iter.heap);
 574                         CHAN_WARN_ON(chan, !buf);
 575                         goto skip_get_next;
 576                 }
 577         }
 578
 579         while (read_count < count) {
 580                 size_t copy_len, space_left;
 581
 582                 if (fusionmerge)
 583                         len = channel_get_next_record(chan, &buf);
 584                 else
 585                         len = lib_ring_buffer_get_next_record(chan, buf);
 586 len_test:
 587                 if (len < 0) {
 588                         /*
 589                          * Check if buffer is finalized (end of file).
 590                          */
 591                         if (len == -ENODATA) {
 592                                 /* A 0 read_count will tell about end of file */
 593                                 goto nodata;
 594                         }
 595                         if (filp->f_flags & O_NONBLOCK) {
 596                                 if (!read_count)
 597                                         read_count = -EAGAIN;
 598                                 goto nodata;
 599                         } else {
 600                                 int error;
 601
 602                                 /*
 603                                  * No data available at the moment, return what
 604                                  * we got.
 605                                  */
 606                                 if (read_count)
 607                                         goto nodata;
 608
 609                                 /*
 610                                  * Wait for returned len to be >= 0 or -ENODATA.
 611                                  */
 612                                 if (fusionmerge)
 613                                         error = wait_event_interruptible(
 614                                           chan->read_wait,
 615                                           ((len = channel_get_next_record(chan,
 616                                                 &buf)), len != -EAGAIN));
 617                                 else
 618                                         error = wait_event_interruptible(
 619                                           buf->read_wait,
 620                                           ((len = lib_ring_buffer_get_next_record(
 621                                                   chan, buf)), len != -EAGAIN));
 622                                 CHAN_WARN_ON(chan, len == -EBUSY);
 623                                 if (error) {
 624                                         read_count = error;
 625                                         goto nodata;
 626                                 }
 627                                 CHAN_WARN_ON(chan, len < 0 && len != -ENODATA);
 628                                 goto len_test;
 629                         }
 630                 }
 631                 read_offset = buf->iter.read_offset;
 632 skip_get_next:
 633                 space_left = count - read_count;
 634                 if (len <= space_left) {
 635                         copy_len = len;
 636                         chan->iter.len_left = 0;
 637                         *ppos = 0;
 638                 } else {
 639                         copy_len = space_left;
 640                         chan->iter.len_left = len - copy_len;
 641                         *ppos = read_offset + copy_len;
 642                 }
 643                 if (__lib_ring_buffer_copy_to_user(&buf->backend, read_offset,
 644                                                &user_buf[read_count],
 645                                                copy_len)) {
 646                         /*
 647                          * Leave the len_left and ppos values at their current
 648                          * state, as we currently have a valid event to read.
 649                          */
 650                         return -EFAULT;
 651                 }
 652                 read_count += copy_len;
 653         };
 654         return read_count;
 655
 656 nodata:
 657         *ppos = 0;
 658         chan->iter.len_left = 0;
 659         return read_count;
 660 }
 661
 662 /**
 663  * lib_ring_buffer_file_read - Read buffer record payload.
 664  * @filp: file structure pointer.
 665  * @buffer: user buffer to read data into.
 666  * @count: number of bytes to read.
 667  * @ppos: file read position.
 668  *
 669  * Returns a negative value on error, or the number of bytes read on success.
 670  * ppos is used to save the position _within the current record_ between calls
 671  * to read().
 672  */
 673 static
 674 ssize_t lib_ring_buffer_file_read(struct file *filp,
 675                                   char __user *user_buf,
 676                                   size_t count,
 677                                   loff_t *ppos)
 678 {
 679         struct inode *inode = filp->f_dentry->d_inode;
 680         struct lib_ring_buffer *buf = inode->i_private;
 681         struct channel *chan = buf->backend.chan;
 682
 683         return channel_ring_buffer_file_read(filp, user_buf, count, ppos,
 684                                              chan, buf, 0);
 685 }
 686
 687 /**
 688  * channel_file_read - Read channel record payload.
 689  * @filp: file structure pointer.
 690  * @buffer: user buffer to read data into.
 691  * @count: number of bytes to read.
 692  * @ppos: file read position.
 693  *
 694  * Returns a negative value on error, or the number of bytes read on success.
 695  * ppos is used to save the position _within the current record_ between calls
 696  * to read().
 697  */
 698 static
 699 ssize_t channel_file_read(struct file *filp,
 700                           char __user *user_buf,
 701                           size_t count,
 702                           loff_t *ppos)
 703 {
 704         struct inode *inode = filp->f_dentry->d_inode;
 705         struct channel *chan = inode->i_private;
 706         const struct lib_ring_buffer_config *config = chan->backend.config;
 707
 708         if (config->alloc == RING_BUFFER_ALLOC_PER_CPU)
 709                 return channel_ring_buffer_file_read(filp, user_buf, count,
 710                                                      ppos, chan, NULL, 1);
 711         else {
 712                 struct lib_ring_buffer *buf =
 713                         channel_get_ring_buffer(config, chan, 0);
 714                 return channel_ring_buffer_file_read(filp, user_buf, count,
 715                                                      ppos, chan, buf, 0);
 716         }
 717 }
 718
 719 static
 720 int lib_ring_buffer_file_open(struct inode *inode, struct file *file)
 721 {
 722         struct lib_ring_buffer *buf = inode->i_private;
 723         int ret;
 724
 725         ret = lib_ring_buffer_iterator_open(buf);
 726         if (ret)
 727                 return ret;
 728
 729         file->private_data = buf;
 730         ret = nonseekable_open(inode, file);
 731         if (ret)
 732                 goto release_iter;
 733         return 0;
 734
 735 release_iter:
 736         lib_ring_buffer_iterator_release(buf);
 737         return ret;
 738 }
 739
 740 static
 741 int lib_ring_buffer_file_release(struct inode *inode, struct file *file)
 742 {
 743         struct lib_ring_buffer *buf = inode->i_private;
 744
 745         lib_ring_buffer_iterator_release(buf);
 746         return 0;
 747 }
 748
 749 static
 750 int channel_file_open(struct inode *inode, struct file *file)
 751 {
 752         struct channel *chan = inode->i_private;
 753         int ret;
 754
 755         ret = channel_iterator_open(chan);
 756         if (ret)
 757                 return ret;
 758
 759         file->private_data = chan;
 760         ret = nonseekable_open(inode, file);
 761         if (ret)
 762                 goto release_iter;
 763         return 0;
 764
 765 release_iter:
 766         channel_iterator_release(chan);
 767         return ret;
 768 }
 769
 770 static
 771 int channel_file_release(struct inode *inode, struct file *file)
 772 {
 773         struct channel *chan = inode->i_private;
 774
 775         channel_iterator_release(chan);
 776         return 0;
 777 }
 778
 779 const struct file_operations channel_payload_file_operations = {
 780         .open = channel_file_open,
 781         .release = channel_file_release,
 782         .read = channel_file_read,
 783         .llseek = lib_ring_buffer_no_llseek,
 784 };
 785 EXPORT_SYMBOL_GPL(channel_payload_file_operations);
 786
 787 const struct file_operations lib_ring_buffer_payload_file_operations = {
 788         .open = lib_ring_buffer_file_open,
 789         .release = lib_ring_buffer_file_release,
 790         .read = lib_ring_buffer_file_read,
 791         .llseek = lib_ring_buffer_no_llseek,
 792 };
 793 EXPORT_SYMBOL_GPL(lib_ring_buffer_payload_file_operations);