libringbuffer/ring_buffer_backend.c

   1 /*
   2  * ring_buffer_backend.c
   3  *
   4  * Copyright (C) 2005-2010 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   5  *
   6  * Dual LGPL v2.1/GPL v2 license.
   7  */
   8
   9 #include <urcu/arch.h>
  10
  11 #include "ust/core.h"
  12
  13 #include <ust/ringbuffer-config.h>
  14 #include "backend.h"
  15 #include "frontend.h"
  16 #include "smp.h"
  17 #include "shm.h"
  18
  19 /**
  20  * lib_ring_buffer_backend_allocate - allocate a channel buffer
  21  * @config: ring buffer instance configuration
  22  * @buf: the buffer struct
  23  * @size: total size of the buffer
  24  * @num_subbuf: number of subbuffers
  25  * @extra_reader_sb: need extra subbuffer for reader
  26  */
  27 static
  28 int lib_ring_buffer_backend_allocate(const struct lib_ring_buffer_config *config,
  29                                      struct lib_ring_buffer_backend *bufb,
  30                                      size_t size, size_t num_subbuf,
  31                                      int extra_reader_sb,
  32                                      struct shm_handle *handle,
  33                                      struct shm_object *shmobj)
  34 {
  35         struct channel_backend *chanb = &shmp(handle, bufb->chan)->backend;
  36         unsigned long subbuf_size, mmap_offset = 0;
  37         unsigned long num_subbuf_alloc;
  38         unsigned long i;
  39
  40         subbuf_size = chanb->subbuf_size;
  41         num_subbuf_alloc = num_subbuf;
  42
  43         if (extra_reader_sb)
  44                 num_subbuf_alloc++;
  45
  46         align_shm(shmobj, __alignof__(struct lib_ring_buffer_backend_pages_shmp));
  47         set_shmp(bufb->array, zalloc_shm(shmobj,
  48                         sizeof(struct lib_ring_buffer_backend_pages_shmp) * num_subbuf_alloc));
  49         if (unlikely(!shmp(handle, bufb->array)))
  50                 goto array_error;
  51
  52         /*
  53          * This is the largest element (the buffer pages) which needs to
  54          * be aligned on PAGE_SIZE.
  55          */
  56         align_shm(shmobj, PAGE_SIZE);
  57         set_shmp(bufb->memory_map, zalloc_shm(shmobj,
  58                         subbuf_size * num_subbuf_alloc));
  59         if (unlikely(!shmp(handle, bufb->memory_map)))
  60                 goto memory_map_error;
  61
  62         /* Allocate backend pages array elements */
  63         for (i = 0; i < num_subbuf_alloc; i++) {
  64                 align_shm(shmobj, __alignof__(struct lib_ring_buffer_backend_pages));
  65                 set_shmp(shmp(handle, bufb->array)[i].shmp,
  66                         zalloc_shm(shmobj,
  67                                 sizeof(struct lib_ring_buffer_backend_pages)));
  68                 if (!shmp(handle, shmp(handle, bufb->array)[i].shmp))
  69                         goto free_array;
  70         }
  71
  72         /* Allocate write-side subbuffer table */
  73         align_shm(shmobj, __alignof__(struct lib_ring_buffer_backend_subbuffer));
  74         set_shmp(bufb->buf_wsb, zalloc_shm(shmobj,
  75                                 sizeof(struct lib_ring_buffer_backend_subbuffer)
  76                                 * num_subbuf));
  77         if (unlikely(!shmp(handle, bufb->buf_wsb)))
  78                 goto free_array;
  79
  80         for (i = 0; i < num_subbuf; i++)
  81                 shmp(handle, bufb->buf_wsb)[i].id = subbuffer_id(config, 0, 1, i);
  82
  83         /* Assign read-side subbuffer table */
  84         if (extra_reader_sb)
  85                 bufb->buf_rsb.id = subbuffer_id(config, 0, 1,
  86                                                 num_subbuf_alloc - 1);
  87         else
  88                 bufb->buf_rsb.id = subbuffer_id(config, 0, 1, 0);
  89
  90         /* Assign pages to page index */
  91         for (i = 0; i < num_subbuf_alloc; i++) {
  92                 struct shm_ref ref;
  93
  94                 ref.index = bufb->memory_map._ref.index;
  95                 ref.offset = bufb->memory_map._ref.offset;
  96                 ref.offset += i * subbuf_size;
  97
  98                 set_shmp(shmp(handle, shmp(handle, bufb->array)[i].shmp)->p,
  99                          ref);
 100                 if (config->output == RING_BUFFER_MMAP) {
 101                         shmp(handle, shmp(handle, bufb->array)[i].shmp)->mmap_offset = mmap_offset;
 102                         mmap_offset += subbuf_size;
 103                 }
 104         }
 105
 106         return 0;
 107
 108 free_array:
 109         /* bufb->array[i] will be freed by shm teardown */
 110 memory_map_error:
 111         /* bufb->array will be freed by shm teardown */
 112 array_error:
 113         return -ENOMEM;
 114 }
 115
 116 int lib_ring_buffer_backend_create(struct lib_ring_buffer_backend *bufb,
 117                                    struct channel_backend *chanb, int cpu,
 118                                    struct shm_handle *handle,
 119                                    struct shm_object *shmobj)
 120 {
 121         const struct lib_ring_buffer_config *config = chanb->config;
 122
 123         set_shmp(bufb->chan, handle->chan._ref);
 124         bufb->cpu = cpu;
 125
 126         return lib_ring_buffer_backend_allocate(config, bufb, chanb->buf_size,
 127                                                 chanb->num_subbuf,
 128                                                 chanb->extra_reader_sb,
 129                                                 handle, shmobj);
 130 }
 131
 132 void lib_ring_buffer_backend_free(struct lib_ring_buffer_backend *bufb)
 133 {
 134         /* bufb->buf_wsb will be freed by shm teardown */
 135         /* bufb->array[i] will be freed by shm teardown */
 136         /* bufb->array will be freed by shm teardown */
 137         bufb->allocated = 0;
 138 }
 139
 140 void lib_ring_buffer_backend_reset(struct lib_ring_buffer_backend *bufb,
 141                                    struct shm_handle *handle)
 142 {
 143         struct channel_backend *chanb = &shmp(handle, bufb->chan)->backend;
 144         const struct lib_ring_buffer_config *config = chanb->config;
 145         unsigned long num_subbuf_alloc;
 146         unsigned int i;
 147
 148         num_subbuf_alloc = chanb->num_subbuf;
 149         if (chanb->extra_reader_sb)
 150                 num_subbuf_alloc++;
 151
 152         for (i = 0; i < chanb->num_subbuf; i++)
 153                 shmp(handle, bufb->buf_wsb)[i].id = subbuffer_id(config, 0, 1, i);
 154         if (chanb->extra_reader_sb)
 155                 bufb->buf_rsb.id = subbuffer_id(config, 0, 1,
 156                                                 num_subbuf_alloc - 1);
 157         else
 158                 bufb->buf_rsb.id = subbuffer_id(config, 0, 1, 0);
 159
 160         for (i = 0; i < num_subbuf_alloc; i++) {
 161                 /* Don't reset mmap_offset */
 162                 v_set(config, &shmp(handle, shmp(handle, bufb->array)[i].shmp)->records_commit, 0);
 163                 v_set(config, &shmp(handle, shmp(handle, bufb->array)[i].shmp)->records_unread, 0);
 164                 shmp(handle, shmp(handle, bufb->array)[i].shmp)->data_size = 0;
 165                 /* Don't reset backend page and virt addresses */
 166         }
 167         /* Don't reset num_pages_per_subbuf, cpu, allocated */
 168         v_set(config, &bufb->records_read, 0);
 169 }
 170
 171 /*
 172  * The frontend is responsible for also calling ring_buffer_backend_reset for
 173  * each buffer when calling channel_backend_reset.
 174  */
 175 void channel_backend_reset(struct channel_backend *chanb)
 176 {
 177         struct channel *chan = caa_container_of(chanb, struct channel, backend);
 178         const struct lib_ring_buffer_config *config = chanb->config;
 179
 180         /*
 181          * Don't reset buf_size, subbuf_size, subbuf_size_order,
 182          * num_subbuf_order, buf_size_order, extra_reader_sb, num_subbuf,
 183          * priv, notifiers, config, cpumask and name.
 184          */
 185         chanb->start_tsc = config->cb.ring_buffer_clock_read(chan);
 186 }
 187
 188 /**
 189  * channel_backend_init - initialize a channel backend
 190  * @chanb: channel backend
 191  * @name: channel name
 192  * @config: client ring buffer configuration
 193  * @priv: client private data
 194  * @parent: dentry of parent directory, %NULL for root directory
 195  * @subbuf_size: size of sub-buffers (> PAGE_SIZE, power of 2)
 196  * @num_subbuf: number of sub-buffers (power of 2)
 197  * @shm_handle: shared memory handle
 198  *
 199  * Returns channel pointer if successful, %NULL otherwise.
 200  *
 201  * Creates per-cpu channel buffers using the sizes and attributes
 202  * specified.  The created channel buffer files will be named
 203  * name_0...name_N-1.  File permissions will be %S_IRUSR.
 204  *
 205  * Called with CPU hotplug disabled.
 206  */
 207 int channel_backend_init(struct channel_backend *chanb,
 208                          const char *name,
 209                          const struct lib_ring_buffer_config *config,
 210                          void *priv, size_t subbuf_size, size_t num_subbuf,
 211                          struct shm_handle *handle)
 212 {
 213         struct channel *chan = caa_container_of(chanb, struct channel, backend);
 214         unsigned int i;
 215         int ret;
 216         size_t shmsize = 0, bufshmsize = 0, num_subbuf_alloc;
 217
 218         if (!name)
 219                 return -EPERM;
 220
 221         if (!(subbuf_size && num_subbuf))
 222                 return -EPERM;
 223
 224         /* Check that the subbuffer size is larger than a page. */
 225         if (subbuf_size < PAGE_SIZE)
 226                 return -EINVAL;
 227
 228         /*
 229          * Make sure the number of subbuffers and subbuffer size are power of 2.
 230          */
 231         CHAN_WARN_ON(chanb, hweight32(subbuf_size) != 1);
 232         CHAN_WARN_ON(chanb, hweight32(num_subbuf) != 1);
 233
 234         ret = subbuffer_id_check_index(config, num_subbuf);
 235         if (ret)
 236                 return ret;
 237
 238         chanb->priv = priv;
 239         chanb->buf_size = num_subbuf * subbuf_size;
 240         chanb->subbuf_size = subbuf_size;
 241         chanb->buf_size_order = get_count_order(chanb->buf_size);
 242         chanb->subbuf_size_order = get_count_order(subbuf_size);
 243         chanb->num_subbuf_order = get_count_order(num_subbuf);
 244         chanb->extra_reader_sb =
 245                         (config->mode == RING_BUFFER_OVERWRITE) ? 1 : 0;
 246         chanb->num_subbuf = num_subbuf;
 247         strncpy(chanb->name, name, NAME_MAX);
 248         chanb->name[NAME_MAX - 1] = '\0';
 249         chanb->config = config;
 250
 251         /* Per-cpu buffer size: control (prior to backend) */
 252         shmsize = offset_align(shmsize, __alignof__(struct lib_ring_buffer));
 253         shmsize += sizeof(struct lib_ring_buffer);
 254
 255         /* Per-cpu buffer size: backend */
 256         /* num_subbuf + 1 is the worse case */
 257         num_subbuf_alloc = num_subbuf + 1;
 258         shmsize += offset_align(shmsize, __alignof__(struct lib_ring_buffer_backend_pages_shmp));
 259         shmsize += sizeof(struct lib_ring_buffer_backend_pages_shmp) * num_subbuf_alloc;
 260         shmsize += offset_align(bufshmsize, PAGE_SIZE);
 261         shmsize += subbuf_size * num_subbuf_alloc;
 262         shmsize += offset_align(bufshmsize, __alignof__(struct lib_ring_buffer_backend_pages));
 263         shmsize += sizeof(struct lib_ring_buffer_backend_pages) * num_subbuf_alloc;
 264         shmsize += offset_align(bufshmsize, __alignof__(struct lib_ring_buffer_backend_subbuffer));
 265         shmsize += sizeof(struct lib_ring_buffer_backend_subbuffer) * num_subbuf;
 266         /* Per-cpu buffer size: control (after backend) */
 267         shmsize += offset_align(shmsize, __alignof__(struct commit_counters_hot));
 268         shmsize += sizeof(struct commit_counters_hot) * num_subbuf;
 269         shmsize += offset_align(shmsize, __alignof__(struct commit_counters_cold));
 270         shmsize += sizeof(struct commit_counters_cold) * num_subbuf;
 271
 272         if (config->alloc == RING_BUFFER_ALLOC_PER_CPU) {
 273                 struct lib_ring_buffer *buf;
 274                 /*
 275                  * We need to allocate for all possible cpus.
 276                  */
 277                 for_each_possible_cpu(i) {
 278                         struct shm_object *shmobj;
 279
 280                         shmobj = shm_object_table_append(handle->table, shmsize);
 281                         align_shm(shmobj, __alignof__(struct lib_ring_buffer));
 282                         set_shmp(chanb->buf[i].shmp, zalloc_shm(shmobj, sizeof(struct lib_ring_buffer)));
 283                         buf = shmp(handle, chanb->buf[i].shmp);
 284                         if (!buf)
 285                                 goto end;
 286                         ret = lib_ring_buffer_create(buf, chanb, i,
 287                                         handle, shmobj);
 288                         if (ret)
 289                                 goto free_bufs; /* cpu hotplug locked */
 290                 }
 291         } else {
 292                 struct shm_object *shmobj;
 293                 struct lib_ring_buffer *buf;
 294
 295                 shmobj = shm_object_table_append(handle->table, shmsize);
 296                 align_shm(shmobj, __alignof__(struct lib_ring_buffer));
 297                 set_shmp(chanb->buf[0].shmp, zalloc_shm(shmobj, sizeof(struct lib_ring_buffer)));
 298                 buf = shmp(handle, chanb->buf[0].shmp);
 299                 if (!buf)
 300                         goto end;
 301                 ret = lib_ring_buffer_create(buf, chanb, -1,
 302                                         handle, shmobj);
 303                 if (ret)
 304                         goto free_bufs;
 305         }
 306         chanb->start_tsc = config->cb.ring_buffer_clock_read(chan);
 307
 308         return 0;
 309
 310 free_bufs:
 311         if (config->alloc == RING_BUFFER_ALLOC_PER_CPU) {
 312                 for_each_possible_cpu(i) {
 313                         struct lib_ring_buffer *buf = shmp(handle, chanb->buf[i].shmp);
 314
 315                         if (!buf->backend.allocated)
 316                                 continue;
 317                         lib_ring_buffer_free(buf, handle);
 318                 }
 319         }
 320         /* We only free the buffer data upon shm teardown */
 321 end:
 322         return -ENOMEM;
 323 }
 324
 325 /**
 326  * channel_backend_free - destroy the channel
 327  * @chan: the channel
 328  *
 329  * Destroy all channel buffers and frees the channel.
 330  */
 331 void channel_backend_free(struct channel_backend *chanb,
 332                           struct shm_handle *handle)
 333 {
 334         const struct lib_ring_buffer_config *config = chanb->config;
 335         unsigned int i;
 336
 337         if (config->alloc == RING_BUFFER_ALLOC_PER_CPU) {
 338                 for_each_possible_cpu(i) {
 339                         struct lib_ring_buffer *buf = shmp(handle, chanb->buf[i].shmp);
 340
 341                         if (!buf->backend.allocated)
 342                                 continue;
 343                         lib_ring_buffer_free(buf, handle);
 344                 }
 345         } else {
 346                 struct lib_ring_buffer *buf = shmp(handle, chanb->buf[0].shmp);
 347
 348                 CHAN_WARN_ON(chanb, !buf->backend.allocated);
 349                 lib_ring_buffer_free(buf, handle);
 350         }
 351         /* We only free the buffer data upon shm teardown */
 352 }
 353
 354 /**
 355  * lib_ring_buffer_read - read data from ring_buffer_buffer.
 356  * @bufb : buffer backend
 357  * @offset : offset within the buffer
 358  * @dest : destination address
 359  * @len : length to copy to destination
 360  *
 361  * Should be protected by get_subbuf/put_subbuf.
 362  * Returns the length copied.
 363  */
 364 size_t lib_ring_buffer_read(struct lib_ring_buffer_backend *bufb, size_t offset,
 365                             void *dest, size_t len, struct shm_handle *handle)
 366 {
 367         struct channel_backend *chanb = &shmp(handle, bufb->chan)->backend;
 368         const struct lib_ring_buffer_config *config = chanb->config;
 369         ssize_t orig_len;
 370         struct lib_ring_buffer_backend_pages_shmp *rpages;
 371         unsigned long sb_bindex, id;
 372
 373         orig_len = len;
 374         offset &= chanb->buf_size - 1;
 375
 376         if (unlikely(!len))
 377                 return 0;
 378         id = bufb->buf_rsb.id;
 379         sb_bindex = subbuffer_id_get_index(config, id);
 380         rpages = &shmp(handle, bufb->array)[sb_bindex];
 381         /*
 382          * Underlying layer should never ask for reads across
 383          * subbuffers.
 384          */
 385         CHAN_WARN_ON(chanb, offset >= chanb->buf_size);
 386         CHAN_WARN_ON(chanb, config->mode == RING_BUFFER_OVERWRITE
 387                      && subbuffer_id_is_noref(config, id));
 388         memcpy(dest, shmp(handle, shmp(handle, rpages->shmp)->p) + (offset & ~(chanb->subbuf_size - 1)), len);
 389         return orig_len;
 390 }
 391
 392 /**
 393  * lib_ring_buffer_read_cstr - read a C-style string from ring_buffer.
 394  * @bufb : buffer backend
 395  * @offset : offset within the buffer
 396  * @dest : destination address
 397  * @len : destination's length
 398  *
 399  * return string's length
 400  * Should be protected by get_subbuf/put_subbuf.
 401  */
 402 int lib_ring_buffer_read_cstr(struct lib_ring_buffer_backend *bufb, size_t offset,
 403                               void *dest, size_t len, struct shm_handle *handle)
 404 {
 405         struct channel_backend *chanb = &shmp(handle, bufb->chan)->backend;
 406         const struct lib_ring_buffer_config *config = chanb->config;
 407         ssize_t string_len, orig_offset;
 408         char *str;
 409         struct lib_ring_buffer_backend_pages_shmp *rpages;
 410         unsigned long sb_bindex, id;
 411
 412         offset &= chanb->buf_size - 1;
 413         orig_offset = offset;
 414         id = bufb->buf_rsb.id;
 415         sb_bindex = subbuffer_id_get_index(config, id);
 416         rpages = &shmp(handle, bufb->array)[sb_bindex];
 417         /*
 418          * Underlying layer should never ask for reads across
 419          * subbuffers.
 420          */
 421         CHAN_WARN_ON(chanb, offset >= chanb->buf_size);
 422         CHAN_WARN_ON(chanb, config->mode == RING_BUFFER_OVERWRITE
 423                      && subbuffer_id_is_noref(config, id));
 424         str = (char *)shmp(handle, shmp(handle, rpages->shmp)->p) + (offset & ~(chanb->subbuf_size - 1));
 425         string_len = strnlen(str, len);
 426         if (dest && len) {
 427                 memcpy(dest, str, string_len);
 428                 ((char *)dest)[0] = 0;
 429         }
 430         return offset - orig_offset;
 431 }
 432
 433 /**
 434  * lib_ring_buffer_read_offset_address - get address of a buffer location
 435  * @bufb : buffer backend
 436  * @offset : offset within the buffer.
 437  *
 438  * Return the address where a given offset is located (for read).
 439  * Should be used to get the current subbuffer header pointer. Given we know
 440  * it's never on a page boundary, it's safe to write directly to this address,
 441  * as long as the write is never bigger than a page size.
 442  */
 443 void *lib_ring_buffer_read_offset_address(struct lib_ring_buffer_backend *bufb,
 444                                           size_t offset,
 445                                           struct shm_handle *handle)
 446 {
 447         struct lib_ring_buffer_backend_pages_shmp *rpages;
 448         struct channel_backend *chanb = &shmp(handle, bufb->chan)->backend;
 449         const struct lib_ring_buffer_config *config = chanb->config;
 450         unsigned long sb_bindex, id;
 451
 452         offset &= chanb->buf_size - 1;
 453         id = bufb->buf_rsb.id;
 454         sb_bindex = subbuffer_id_get_index(config, id);
 455         rpages = &shmp(handle, bufb->array)[sb_bindex];
 456         CHAN_WARN_ON(chanb, config->mode == RING_BUFFER_OVERWRITE
 457                      && subbuffer_id_is_noref(config, id));
 458         return shmp(handle, shmp(handle, rpages->shmp)->p) + (offset & ~(chanb->subbuf_size - 1));
 459 }
 460
 461 /**
 462  * lib_ring_buffer_offset_address - get address of a location within the buffer
 463  * @bufb : buffer backend
 464  * @offset : offset within the buffer.
 465  *
 466  * Return the address where a given offset is located.
 467  * Should be used to get the current subbuffer header pointer. Given we know
 468  * it's always at the beginning of a page, it's safe to write directly to this
 469  * address, as long as the write is never bigger than a page size.
 470  */
 471 void *lib_ring_buffer_offset_address(struct lib_ring_buffer_backend *bufb,
 472                                      size_t offset,
 473                                      struct shm_handle *handle)
 474 {
 475         size_t sbidx;
 476         struct lib_ring_buffer_backend_pages_shmp *rpages;
 477         struct channel_backend *chanb = &shmp(handle, bufb->chan)->backend;
 478         const struct lib_ring_buffer_config *config = chanb->config;
 479         unsigned long sb_bindex, id;
 480
 481         offset &= chanb->buf_size - 1;
 482         sbidx = offset >> chanb->subbuf_size_order;
 483         id = shmp(handle, bufb->buf_wsb)[sbidx].id;
 484         sb_bindex = subbuffer_id_get_index(config, id);
 485         rpages = &shmp(handle, bufb->array)[sb_bindex];
 486         CHAN_WARN_ON(chanb, config->mode == RING_BUFFER_OVERWRITE
 487                      && subbuffer_id_is_noref(config, id));
 488         return shmp(handle, shmp(handle, rpages->shmp)->p) + (offset & ~(chanb->subbuf_size - 1));
 489 }