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 "lttng/core.h"
  12
  13 #include <lttng/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 lttng_ust_lib_ring_buffer_config *config,
  29                                      struct lttng_ust_lib_ring_buffer_backend *bufb,
  30                                      size_t size, size_t num_subbuf,
  31                                      int extra_reader_sb,
  32                                      struct lttng_ust_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 lttng_ust_lib_ring_buffer_backend_pages_shmp));
  47         set_shmp(bufb->array, zalloc_shm(shmobj,
  48                         sizeof(struct lttng_ust_lib_ring_buffer_backend_pages_shmp) * num_subbuf_alloc));
  49         if (caa_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 (caa_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 lttng_ust_lib_ring_buffer_backend_pages));
  65                 set_shmp(shmp_index(handle, bufb->array, i)->shmp,
  66                         zalloc_shm(shmobj,
  67                                 sizeof(struct lttng_ust_lib_ring_buffer_backend_pages)));
  68                 if (!shmp(handle, shmp_index(handle, bufb->array, i)->shmp))
  69                         goto free_array;
  70         }
  71
  72         /* Allocate write-side subbuffer table */
  73         align_shm(shmobj, __alignof__(struct lttng_ust_lib_ring_buffer_backend_subbuffer));
  74         set_shmp(bufb->buf_wsb, zalloc_shm(shmobj,
  75                                 sizeof(struct lttng_ust_lib_ring_buffer_backend_subbuffer)
  76                                 * num_subbuf));
  77         if (caa_unlikely(!shmp(handle, bufb->buf_wsb)))
  78                 goto free_array;
  79
  80         for (i = 0; i < num_subbuf; i++)
  81                 shmp_index(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_index(handle, bufb->array, i)->shmp)->p,
  99                          ref);
 100                 if (config->output == RING_BUFFER_MMAP) {
 101                         shmp(handle, shmp_index(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 lttng_ust_lib_ring_buffer_backend *bufb,
 117                                    struct channel_backend *chanb, int cpu,
 118                                    struct lttng_ust_shm_handle *handle,
 119                                    struct shm_object *shmobj)
 120 {
 121         const struct lttng_ust_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_reset(struct lttng_ust_lib_ring_buffer_backend *bufb,
 133                                    struct lttng_ust_shm_handle *handle)
 134 {
 135         struct channel_backend *chanb = &shmp(handle, bufb->chan)->backend;
 136         const struct lttng_ust_lib_ring_buffer_config *config = &chanb->config;
 137         unsigned long num_subbuf_alloc;
 138         unsigned int i;
 139
 140         num_subbuf_alloc = chanb->num_subbuf;
 141         if (chanb->extra_reader_sb)
 142                 num_subbuf_alloc++;
 143
 144         for (i = 0; i < chanb->num_subbuf; i++)
 145                 shmp_index(handle, bufb->buf_wsb, i)->id = subbuffer_id(config, 0, 1, i);
 146         if (chanb->extra_reader_sb)
 147                 bufb->buf_rsb.id = subbuffer_id(config, 0, 1,
 148                                                 num_subbuf_alloc - 1);
 149         else
 150                 bufb->buf_rsb.id = subbuffer_id(config, 0, 1, 0);
 151
 152         for (i = 0; i < num_subbuf_alloc; i++) {
 153                 /* Don't reset mmap_offset */
 154                 v_set(config, &shmp(handle, shmp_index(handle, bufb->array, i)->shmp)->records_commit, 0);
 155                 v_set(config, &shmp(handle, shmp_index(handle, bufb->array, i)->shmp)->records_unread, 0);
 156                 shmp(handle, shmp_index(handle, bufb->array, i)->shmp)->data_size = 0;
 157                 /* Don't reset backend page and virt addresses */
 158         }
 159         /* Don't reset num_pages_per_subbuf, cpu, allocated */
 160         v_set(config, &bufb->records_read, 0);
 161 }
 162
 163 /*
 164  * The frontend is responsible for also calling ring_buffer_backend_reset for
 165  * each buffer when calling channel_backend_reset.
 166  */
 167 void channel_backend_reset(struct channel_backend *chanb)
 168 {
 169         struct channel *chan = caa_container_of(chanb, struct channel, backend);
 170         const struct lttng_ust_lib_ring_buffer_config *config = &chanb->config;
 171
 172         /*
 173          * Don't reset buf_size, subbuf_size, subbuf_size_order,
 174          * num_subbuf_order, buf_size_order, extra_reader_sb, num_subbuf,
 175          * priv, notifiers, config, cpumask and name.
 176          */
 177         chanb->start_tsc = config->cb.ring_buffer_clock_read(chan);
 178 }
 179
 180 /**
 181  * channel_backend_init - initialize a channel backend
 182  * @chanb: channel backend
 183  * @name: channel name
 184  * @config: client ring buffer configuration
 185  * @parent: dentry of parent directory, %NULL for root directory
 186  * @subbuf_size: size of sub-buffers (> PAGE_SIZE, power of 2)
 187  * @num_subbuf: number of sub-buffers (power of 2)
 188  * @lttng_ust_shm_handle: shared memory handle
 189  *
 190  * Returns channel pointer if successful, %NULL otherwise.
 191  *
 192  * Creates per-cpu channel buffers using the sizes and attributes
 193  * specified.  The created channel buffer files will be named
 194  * name_0...name_N-1.  File permissions will be %S_IRUSR.
 195  *
 196  * Called with CPU hotplug disabled.
 197  */
 198 int channel_backend_init(struct channel_backend *chanb,
 199                          const char *name,
 200                          const struct lttng_ust_lib_ring_buffer_config *config,
 201                          size_t subbuf_size, size_t num_subbuf,
 202                          struct lttng_ust_shm_handle *handle)
 203 {
 204         struct channel *chan = caa_container_of(chanb, struct channel, backend);
 205         unsigned int i;
 206         int ret;
 207         size_t shmsize = 0, num_subbuf_alloc;
 208
 209         if (!name)
 210                 return -EPERM;
 211
 212         if (!(subbuf_size && num_subbuf))
 213                 return -EPERM;
 214
 215         /* Check that the subbuffer size is larger than a page. */
 216         if (subbuf_size < PAGE_SIZE)
 217                 return -EINVAL;
 218
 219         /*
 220          * Make sure the number of subbuffers and subbuffer size are power of 2.
 221          */
 222         CHAN_WARN_ON(chanb, hweight32(subbuf_size) != 1);
 223         CHAN_WARN_ON(chanb, hweight32(num_subbuf) != 1);
 224
 225         ret = subbuffer_id_check_index(config, num_subbuf);
 226         if (ret)
 227                 return ret;
 228
 229         chanb->buf_size = num_subbuf * subbuf_size;
 230         chanb->subbuf_size = subbuf_size;
 231         chanb->buf_size_order = get_count_order(chanb->buf_size);
 232         chanb->subbuf_size_order = get_count_order(subbuf_size);
 233         chanb->num_subbuf_order = get_count_order(num_subbuf);
 234         chanb->extra_reader_sb =
 235                         (config->mode == RING_BUFFER_OVERWRITE) ? 1 : 0;
 236         chanb->num_subbuf = num_subbuf;
 237         strncpy(chanb->name, name, NAME_MAX);
 238         chanb->name[NAME_MAX - 1] = '\0';
 239         memcpy(&chanb->config, config, sizeof(*config));
 240
 241         /* Per-cpu buffer size: control (prior to backend) */
 242         shmsize = offset_align(shmsize, __alignof__(struct lttng_ust_lib_ring_buffer));
 243         shmsize += sizeof(struct lttng_ust_lib_ring_buffer);
 244
 245         /* Per-cpu buffer size: backend */
 246         /* num_subbuf + 1 is the worse case */
 247         num_subbuf_alloc = num_subbuf + 1;
 248         shmsize += offset_align(shmsize, __alignof__(struct lttng_ust_lib_ring_buffer_backend_pages_shmp));
 249         shmsize += sizeof(struct lttng_ust_lib_ring_buffer_backend_pages_shmp) * num_subbuf_alloc;
 250         shmsize += offset_align(shmsize, PAGE_SIZE);
 251         shmsize += subbuf_size * num_subbuf_alloc;
 252         shmsize += offset_align(shmsize, __alignof__(struct lttng_ust_lib_ring_buffer_backend_pages));
 253         shmsize += sizeof(struct lttng_ust_lib_ring_buffer_backend_pages) * num_subbuf_alloc;
 254         shmsize += offset_align(shmsize, __alignof__(struct lttng_ust_lib_ring_buffer_backend_subbuffer));
 255         shmsize += sizeof(struct lttng_ust_lib_ring_buffer_backend_subbuffer) * num_subbuf;
 256         /* Per-cpu buffer size: control (after backend) */
 257         shmsize += offset_align(shmsize, __alignof__(struct commit_counters_hot));
 258         shmsize += sizeof(struct commit_counters_hot) * num_subbuf;
 259         shmsize += offset_align(shmsize, __alignof__(struct commit_counters_cold));
 260         shmsize += sizeof(struct commit_counters_cold) * num_subbuf;
 261
 262         if (config->alloc == RING_BUFFER_ALLOC_PER_CPU) {
 263                 struct lttng_ust_lib_ring_buffer *buf;
 264                 /*
 265                  * We need to allocate for all possible cpus.
 266                  */
 267                 for_each_possible_cpu(i) {
 268                         struct shm_object *shmobj;
 269
 270                         shmobj = shm_object_table_append(handle->table, shmsize);
 271                         if (!shmobj)
 272                                 goto end;
 273                         align_shm(shmobj, __alignof__(struct lttng_ust_lib_ring_buffer));
 274                         set_shmp(chanb->buf[i].shmp, zalloc_shm(shmobj, sizeof(struct lttng_ust_lib_ring_buffer)));
 275                         buf = shmp(handle, chanb->buf[i].shmp);
 276                         if (!buf)
 277                                 goto end;
 278                         set_shmp(buf->self, chanb->buf[i].shmp._ref);
 279                         ret = lib_ring_buffer_create(buf, chanb, i,
 280                                         handle, shmobj);
 281                         if (ret)
 282                                 goto free_bufs; /* cpu hotplug locked */
 283                 }
 284         } else {
 285                 struct shm_object *shmobj;
 286                 struct lttng_ust_lib_ring_buffer *buf;
 287
 288                 shmobj = shm_object_table_append(handle->table, shmsize);
 289                 if (!shmobj)
 290                         goto end;
 291                 align_shm(shmobj, __alignof__(struct lttng_ust_lib_ring_buffer));
 292                 set_shmp(chanb->buf[0].shmp, zalloc_shm(shmobj, sizeof(struct lttng_ust_lib_ring_buffer)));
 293                 buf = shmp(handle, chanb->buf[0].shmp);
 294                 if (!buf)
 295                         goto end;
 296                 ret = lib_ring_buffer_create(buf, chanb, -1,
 297                                         handle, shmobj);
 298                 if (ret)
 299                         goto free_bufs;
 300         }
 301         chanb->start_tsc = config->cb.ring_buffer_clock_read(chan);
 302
 303         return 0;
 304
 305 free_bufs:
 306         /* We only free the buffer data upon shm teardown */
 307 end:
 308         return -ENOMEM;
 309 }
 310
 311 /**
 312  * channel_backend_free - destroy the channel
 313  * @chan: the channel
 314  *
 315  * Destroy all channel buffers and frees the channel.
 316  */
 317 void channel_backend_free(struct channel_backend *chanb,
 318                           struct lttng_ust_shm_handle *handle)
 319 {
 320         /* SHM teardown takes care of everything */
 321 }
 322
 323 /**
 324  * lib_ring_buffer_read - read data from ring_buffer_buffer.
 325  * @bufb : buffer backend
 326  * @offset : offset within the buffer
 327  * @dest : destination address
 328  * @len : length to copy to destination
 329  *
 330  * Should be protected by get_subbuf/put_subbuf.
 331  * Returns the length copied.
 332  */
 333 size_t lib_ring_buffer_read(struct lttng_ust_lib_ring_buffer_backend *bufb, size_t offset,
 334                             void *dest, size_t len, struct lttng_ust_shm_handle *handle)
 335 {
 336         struct channel_backend *chanb = &shmp(handle, bufb->chan)->backend;
 337         const struct lttng_ust_lib_ring_buffer_config *config = &chanb->config;
 338         ssize_t orig_len;
 339         struct lttng_ust_lib_ring_buffer_backend_pages_shmp *rpages;
 340         unsigned long sb_bindex, id;
 341
 342         orig_len = len;
 343         offset &= chanb->buf_size - 1;
 344
 345         if (caa_unlikely(!len))
 346                 return 0;
 347         id = bufb->buf_rsb.id;
 348         sb_bindex = subbuffer_id_get_index(config, id);
 349         rpages = shmp_index(handle, bufb->array, sb_bindex);
 350         /*
 351          * Underlying layer should never ask for reads across
 352          * subbuffers.
 353          */
 354         CHAN_WARN_ON(chanb, offset >= chanb->buf_size);
 355         CHAN_WARN_ON(chanb, config->mode == RING_BUFFER_OVERWRITE
 356                      && subbuffer_id_is_noref(config, id));
 357         memcpy(dest, shmp_index(handle, shmp(handle, rpages->shmp)->p, offset & (chanb->subbuf_size - 1)), len);
 358         return orig_len;
 359 }
 360
 361 /**
 362  * lib_ring_buffer_read_cstr - read a C-style string from ring_buffer.
 363  * @bufb : buffer backend
 364  * @offset : offset within the buffer
 365  * @dest : destination address
 366  * @len : destination's length
 367  *
 368  * return string's length
 369  * Should be protected by get_subbuf/put_subbuf.
 370  */
 371 int lib_ring_buffer_read_cstr(struct lttng_ust_lib_ring_buffer_backend *bufb, size_t offset,
 372                               void *dest, size_t len, struct lttng_ust_shm_handle *handle)
 373 {
 374         struct channel_backend *chanb = &shmp(handle, bufb->chan)->backend;
 375         const struct lttng_ust_lib_ring_buffer_config *config = &chanb->config;
 376         ssize_t string_len, orig_offset;
 377         char *str;
 378         struct lttng_ust_lib_ring_buffer_backend_pages_shmp *rpages;
 379         unsigned long sb_bindex, id;
 380
 381         offset &= chanb->buf_size - 1;
 382         orig_offset = offset;
 383         id = bufb->buf_rsb.id;
 384         sb_bindex = subbuffer_id_get_index(config, id);
 385         rpages = shmp_index(handle, bufb->array, sb_bindex);
 386         /*
 387          * Underlying layer should never ask for reads across
 388          * subbuffers.
 389          */
 390         CHAN_WARN_ON(chanb, offset >= chanb->buf_size);
 391         CHAN_WARN_ON(chanb, config->mode == RING_BUFFER_OVERWRITE
 392                      && subbuffer_id_is_noref(config, id));
 393         str = shmp_index(handle, shmp(handle, rpages->shmp)->p, offset & (chanb->subbuf_size - 1));
 394         string_len = strnlen(str, len);
 395         if (dest && len) {
 396                 memcpy(dest, str, string_len);
 397                 ((char *)dest)[0] = 0;
 398         }
 399         return offset - orig_offset;
 400 }
 401
 402 /**
 403  * lib_ring_buffer_read_offset_address - get address of a buffer location
 404  * @bufb : buffer backend
 405  * @offset : offset within the buffer.
 406  *
 407  * Return the address where a given offset is located (for read).
 408  * Should be used to get the current subbuffer header pointer. Given we know
 409  * it's never on a page boundary, it's safe to write directly to this address,
 410  * as long as the write is never bigger than a page size.
 411  */
 412 void *lib_ring_buffer_read_offset_address(struct lttng_ust_lib_ring_buffer_backend *bufb,
 413                                           size_t offset,
 414                                           struct lttng_ust_shm_handle *handle)
 415 {
 416         struct lttng_ust_lib_ring_buffer_backend_pages_shmp *rpages;
 417         struct channel_backend *chanb = &shmp(handle, bufb->chan)->backend;
 418         const struct lttng_ust_lib_ring_buffer_config *config = &chanb->config;
 419         unsigned long sb_bindex, id;
 420
 421         offset &= chanb->buf_size - 1;
 422         id = bufb->buf_rsb.id;
 423         sb_bindex = subbuffer_id_get_index(config, id);
 424         rpages = shmp_index(handle, bufb->array, sb_bindex);
 425         CHAN_WARN_ON(chanb, config->mode == RING_BUFFER_OVERWRITE
 426                      && subbuffer_id_is_noref(config, id));
 427         return shmp_index(handle, shmp(handle, rpages->shmp)->p, offset & (chanb->subbuf_size - 1));
 428 }
 429
 430 /**
 431  * lib_ring_buffer_offset_address - get address of a location within the buffer
 432  * @bufb : buffer backend
 433  * @offset : offset within the buffer.
 434  *
 435  * Return the address where a given offset is located.
 436  * Should be used to get the current subbuffer header pointer. Given we know
 437  * it's always at the beginning of a page, it's safe to write directly to this
 438  * address, as long as the write is never bigger than a page size.
 439  */
 440 void *lib_ring_buffer_offset_address(struct lttng_ust_lib_ring_buffer_backend *bufb,
 441                                      size_t offset,
 442                                      struct lttng_ust_shm_handle *handle)
 443 {
 444         size_t sbidx;
 445         struct lttng_ust_lib_ring_buffer_backend_pages_shmp *rpages;
 446         struct channel_backend *chanb = &shmp(handle, bufb->chan)->backend;
 447         const struct lttng_ust_lib_ring_buffer_config *config = &chanb->config;
 448         unsigned long sb_bindex, id;
 449
 450         offset &= chanb->buf_size - 1;
 451         sbidx = offset >> chanb->subbuf_size_order;
 452         id = shmp_index(handle, bufb->buf_wsb, sbidx)->id;
 453         sb_bindex = subbuffer_id_get_index(config, id);
 454         rpages = shmp_index(handle, bufb->array, sb_bindex);
 455         CHAN_WARN_ON(chanb, config->mode == RING_BUFFER_OVERWRITE
 456                      && subbuffer_id_is_noref(config, id));
 457         return shmp_index(handle, shmp(handle, rpages->shmp)->p, offset & (chanb->subbuf_size - 1));
 458 }