libringbuffer/ring_buffer_backend.c

   1 /*
   2  * ring_buffer_backend.c
   3  *
   4  * Copyright (C) 2005-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   5  *
   6  * This library is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU Lesser General Public
   8  * License as published by the Free Software Foundation; only
   9  * version 2.1 of the License.
  10  *
  11  * This library is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  14  * Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General Public
  17  * License along with this library; if not, write to the Free Software
  18  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  19  */
  20
  21 #define _GNU_SOURCE
  22 #include <unistd.h>
  23 #include <urcu/arch.h>
  24 #include <limits.h>
  25
  26 #include <lttng/ringbuffer-config.h>
  27 #include "vatomic.h"
  28 #include "backend.h"
  29 #include "frontend.h"
  30 #include "smp.h"
  31 #include "shm.h"
  32
  33 /**
  34  * lib_ring_buffer_backend_allocate - allocate a channel buffer
  35  * @config: ring buffer instance configuration
  36  * @buf: the buffer struct
  37  * @size: total size of the buffer
  38  * @num_subbuf: number of subbuffers
  39  * @extra_reader_sb: need extra subbuffer for reader
  40  */
  41 static
  42 int lib_ring_buffer_backend_allocate(const struct lttng_ust_lib_ring_buffer_config *config,
  43                                      struct lttng_ust_lib_ring_buffer_backend *bufb,
  44                                      size_t size, size_t num_subbuf,
  45                                      int extra_reader_sb,
  46                                      struct lttng_ust_shm_handle *handle,
  47                                      struct shm_object *shmobj)
  48 {
  49         struct channel_backend *chanb = &shmp(handle, bufb->chan)->backend;
  50         unsigned long subbuf_size, mmap_offset = 0;
  51         unsigned long num_subbuf_alloc;
  52         unsigned long i;
  53         long page_size;
  54
  55         subbuf_size = chanb->subbuf_size;
  56         num_subbuf_alloc = num_subbuf;
  57
  58         if (extra_reader_sb)
  59                 num_subbuf_alloc++;
  60
  61         page_size = sysconf(_SC_PAGE_SIZE);
  62         if (page_size <= 0) {
  63                 goto page_size_error;
  64         }
  65
  66         align_shm(shmobj, __alignof__(struct lttng_ust_lib_ring_buffer_backend_pages_shmp));
  67         set_shmp(bufb->array, zalloc_shm(shmobj,
  68                         sizeof(struct lttng_ust_lib_ring_buffer_backend_pages_shmp) * num_subbuf_alloc));
  69         if (caa_unlikely(!shmp(handle, bufb->array)))
  70                 goto array_error;
  71
  72         /*
  73          * This is the largest element (the buffer pages) which needs to
  74          * be aligned on page size.
  75          */
  76         align_shm(shmobj, page_size);
  77         set_shmp(bufb->memory_map, zalloc_shm(shmobj,
  78                         subbuf_size * num_subbuf_alloc));
  79         if (caa_unlikely(!shmp(handle, bufb->memory_map)))
  80                 goto memory_map_error;
  81
  82         /* Allocate backend pages array elements */
  83         for (i = 0; i < num_subbuf_alloc; i++) {
  84                 align_shm(shmobj, __alignof__(struct lttng_ust_lib_ring_buffer_backend_pages));
  85                 set_shmp(shmp_index(handle, bufb->array, i)->shmp,
  86                         zalloc_shm(shmobj,
  87                                 sizeof(struct lttng_ust_lib_ring_buffer_backend_pages)));
  88                 if (!shmp(handle, shmp_index(handle, bufb->array, i)->shmp))
  89                         goto free_array;
  90         }
  91
  92         /* Allocate write-side subbuffer table */
  93         align_shm(shmobj, __alignof__(struct lttng_ust_lib_ring_buffer_backend_subbuffer));
  94         set_shmp(bufb->buf_wsb, zalloc_shm(shmobj,
  95                                 sizeof(struct lttng_ust_lib_ring_buffer_backend_subbuffer)
  96                                 * num_subbuf));
  97         if (caa_unlikely(!shmp(handle, bufb->buf_wsb)))
  98                 goto free_array;
  99
 100         for (i = 0; i < num_subbuf; i++)
 101                 shmp_index(handle, bufb->buf_wsb, i)->id = subbuffer_id(config, 0, 1, i);
 102
 103         /* Assign read-side subbuffer table */
 104         if (extra_reader_sb)
 105                 bufb->buf_rsb.id = subbuffer_id(config, 0, 1,
 106                                                 num_subbuf_alloc - 1);
 107         else
 108                 bufb->buf_rsb.id = subbuffer_id(config, 0, 1, 0);
 109
 110         /* Assign pages to page index */
 111         for (i = 0; i < num_subbuf_alloc; i++) {
 112                 struct shm_ref ref;
 113
 114                 ref.index = bufb->memory_map._ref.index;
 115                 ref.offset = bufb->memory_map._ref.offset;
 116                 ref.offset += i * subbuf_size;
 117
 118                 set_shmp(shmp(handle, shmp_index(handle, bufb->array, i)->shmp)->p,
 119                          ref);
 120                 if (config->output == RING_BUFFER_MMAP) {
 121                         shmp(handle, shmp_index(handle, bufb->array, i)->shmp)->mmap_offset = mmap_offset;
 122                         mmap_offset += subbuf_size;
 123                 }
 124         }
 125
 126         return 0;
 127
 128 free_array:
 129         /* bufb->array[i] will be freed by shm teardown */
 130 memory_map_error:
 131         /* bufb->array will be freed by shm teardown */
 132 array_error:
 133 page_size_error:
 134         return -ENOMEM;
 135 }
 136
 137 int lib_ring_buffer_backend_create(struct lttng_ust_lib_ring_buffer_backend *bufb,
 138                                    struct channel_backend *chanb, int cpu,
 139                                    struct lttng_ust_shm_handle *handle,
 140                                    struct shm_object *shmobj)
 141 {
 142         const struct lttng_ust_lib_ring_buffer_config *config = &chanb->config;
 143
 144         set_shmp(bufb->chan, handle->chan._ref);
 145         bufb->cpu = cpu;
 146
 147         return lib_ring_buffer_backend_allocate(config, bufb, chanb->buf_size,
 148                                                 chanb->num_subbuf,
 149                                                 chanb->extra_reader_sb,
 150                                                 handle, shmobj);
 151 }
 152
 153 void lib_ring_buffer_backend_reset(struct lttng_ust_lib_ring_buffer_backend *bufb,
 154                                    struct lttng_ust_shm_handle *handle)
 155 {
 156         struct channel_backend *chanb = &shmp(handle, bufb->chan)->backend;
 157         const struct lttng_ust_lib_ring_buffer_config *config = &chanb->config;
 158         unsigned long num_subbuf_alloc;
 159         unsigned int i;
 160
 161         num_subbuf_alloc = chanb->num_subbuf;
 162         if (chanb->extra_reader_sb)
 163                 num_subbuf_alloc++;
 164
 165         for (i = 0; i < chanb->num_subbuf; i++)
 166                 shmp_index(handle, bufb->buf_wsb, i)->id = subbuffer_id(config, 0, 1, i);
 167         if (chanb->extra_reader_sb)
 168                 bufb->buf_rsb.id = subbuffer_id(config, 0, 1,
 169                                                 num_subbuf_alloc - 1);
 170         else
 171                 bufb->buf_rsb.id = subbuffer_id(config, 0, 1, 0);
 172
 173         for (i = 0; i < num_subbuf_alloc; i++) {
 174                 /* Don't reset mmap_offset */
 175                 v_set(config, &shmp(handle, shmp_index(handle, bufb->array, i)->shmp)->records_commit, 0);
 176                 v_set(config, &shmp(handle, shmp_index(handle, bufb->array, i)->shmp)->records_unread, 0);
 177                 shmp(handle, shmp_index(handle, bufb->array, i)->shmp)->data_size = 0;
 178                 /* Don't reset backend page and virt addresses */
 179         }
 180         /* Don't reset num_pages_per_subbuf, cpu, allocated */
 181         v_set(config, &bufb->records_read, 0);
 182 }
 183
 184 /*
 185  * The frontend is responsible for also calling ring_buffer_backend_reset for
 186  * each buffer when calling channel_backend_reset.
 187  */
 188 void channel_backend_reset(struct channel_backend *chanb)
 189 {
 190         struct channel *chan = caa_container_of(chanb, struct channel, backend);
 191         const struct lttng_ust_lib_ring_buffer_config *config = &chanb->config;
 192
 193         /*
 194          * Don't reset buf_size, subbuf_size, subbuf_size_order,
 195          * num_subbuf_order, buf_size_order, extra_reader_sb, num_subbuf,
 196          * priv, notifiers, config, cpumask and name.
 197          */
 198         chanb->start_tsc = config->cb.ring_buffer_clock_read(chan);
 199 }
 200
 201 /**
 202  * channel_backend_init - initialize a channel backend
 203  * @chanb: channel backend
 204  * @name: channel name
 205  * @config: client ring buffer configuration
 206  * @parent: dentry of parent directory, %NULL for root directory
 207  * @subbuf_size: size of sub-buffers (> page size, power of 2)
 208  * @num_subbuf: number of sub-buffers (power of 2)
 209  * @lttng_ust_shm_handle: shared memory handle
 210  *
 211  * Returns channel pointer if successful, %NULL otherwise.
 212  *
 213  * Creates per-cpu channel buffers using the sizes and attributes
 214  * specified.  The created channel buffer files will be named
 215  * name_0...name_N-1.  File permissions will be %S_IRUSR.
 216  *
 217  * Called with CPU hotplug disabled.
 218  */
 219 int channel_backend_init(struct channel_backend *chanb,
 220                          const char *name,
 221                          const struct lttng_ust_lib_ring_buffer_config *config,
 222                          size_t subbuf_size, size_t num_subbuf,
 223                          struct lttng_ust_shm_handle *handle)
 224 {
 225         struct channel *chan = caa_container_of(chanb, struct channel, backend);
 226         unsigned int i;
 227         int ret;
 228         size_t shmsize = 0, num_subbuf_alloc;
 229         long page_size;
 230
 231         if (!name)
 232                 return -EPERM;
 233
 234         page_size = sysconf(_SC_PAGE_SIZE);
 235         if (page_size <= 0) {
 236                 return -ENOMEM;
 237         }
 238         /* Check that the subbuffer size is larger than a page. */
 239         if (subbuf_size < page_size)
 240                 return -EINVAL;
 241
 242         /*
 243          * Make sure the number of subbuffers and subbuffer size are
 244          * power of 2, and nonzero.
 245          */
 246         if (!subbuf_size || (subbuf_size & (subbuf_size - 1)))
 247                 return -EINVAL;
 248         if (!num_subbuf || (num_subbuf & (num_subbuf - 1)))
 249                 return -EINVAL;
 250         /*
 251          * Overwrite mode buffers require at least 2 subbuffers per
 252          * buffer.
 253          */
 254         if (config->mode == RING_BUFFER_OVERWRITE && num_subbuf < 2)
 255                 return -EINVAL;
 256
 257         ret = subbuffer_id_check_index(config, num_subbuf);
 258         if (ret)
 259                 return ret;
 260
 261         chanb->buf_size = num_subbuf * subbuf_size;
 262         chanb->subbuf_size = subbuf_size;
 263         chanb->buf_size_order = get_count_order(chanb->buf_size);
 264         chanb->subbuf_size_order = get_count_order(subbuf_size);
 265         chanb->num_subbuf_order = get_count_order(num_subbuf);
 266         chanb->extra_reader_sb =
 267                         (config->mode == RING_BUFFER_OVERWRITE) ? 1 : 0;
 268         chanb->num_subbuf = num_subbuf;
 269         strncpy(chanb->name, name, NAME_MAX);
 270         chanb->name[NAME_MAX - 1] = '\0';
 271         memcpy(&chanb->config, config, sizeof(*config));
 272
 273         /* Per-cpu buffer size: control (prior to backend) */
 274         shmsize = offset_align(shmsize, __alignof__(struct lttng_ust_lib_ring_buffer));
 275         shmsize += sizeof(struct lttng_ust_lib_ring_buffer);
 276
 277         /* Per-cpu buffer size: backend */
 278         /* num_subbuf + 1 is the worse case */
 279         num_subbuf_alloc = num_subbuf + 1;
 280         shmsize += offset_align(shmsize, __alignof__(struct lttng_ust_lib_ring_buffer_backend_pages_shmp));
 281         shmsize += sizeof(struct lttng_ust_lib_ring_buffer_backend_pages_shmp) * num_subbuf_alloc;
 282         shmsize += offset_align(shmsize, page_size);
 283         shmsize += subbuf_size * num_subbuf_alloc;
 284         shmsize += offset_align(shmsize, __alignof__(struct lttng_ust_lib_ring_buffer_backend_pages));
 285         shmsize += sizeof(struct lttng_ust_lib_ring_buffer_backend_pages) * num_subbuf_alloc;
 286         shmsize += offset_align(shmsize, __alignof__(struct lttng_ust_lib_ring_buffer_backend_subbuffer));
 287         shmsize += sizeof(struct lttng_ust_lib_ring_buffer_backend_subbuffer) * num_subbuf;
 288         /* Per-cpu buffer size: control (after backend) */
 289         shmsize += offset_align(shmsize, __alignof__(struct commit_counters_hot));
 290         shmsize += sizeof(struct commit_counters_hot) * num_subbuf;
 291         shmsize += offset_align(shmsize, __alignof__(struct commit_counters_cold));
 292         shmsize += sizeof(struct commit_counters_cold) * num_subbuf;
 293
 294         if (config->alloc == RING_BUFFER_ALLOC_PER_CPU) {
 295                 struct lttng_ust_lib_ring_buffer *buf;
 296                 /*
 297                  * We need to allocate for all possible cpus.
 298                  */
 299                 for_each_possible_cpu(i) {
 300                         struct shm_object *shmobj;
 301
 302                         shmobj = shm_object_table_alloc(handle->table, shmsize,
 303                                         SHM_OBJECT_SHM);
 304                         if (!shmobj)
 305                                 goto end;
 306                         align_shm(shmobj, __alignof__(struct lttng_ust_lib_ring_buffer));
 307                         set_shmp(chanb->buf[i].shmp, zalloc_shm(shmobj, sizeof(struct lttng_ust_lib_ring_buffer)));
 308                         buf = shmp(handle, chanb->buf[i].shmp);
 309                         if (!buf)
 310                                 goto end;
 311                         set_shmp(buf->self, chanb->buf[i].shmp._ref);
 312                         ret = lib_ring_buffer_create(buf, chanb, i,
 313                                         handle, shmobj);
 314                         if (ret)
 315                                 goto free_bufs; /* cpu hotplug locked */
 316                 }
 317         } else {
 318                 struct shm_object *shmobj;
 319                 struct lttng_ust_lib_ring_buffer *buf;
 320
 321                 shmobj = shm_object_table_alloc(handle->table, shmsize,
 322                                         SHM_OBJECT_SHM);
 323                 if (!shmobj)
 324                         goto end;
 325                 align_shm(shmobj, __alignof__(struct lttng_ust_lib_ring_buffer));
 326                 set_shmp(chanb->buf[0].shmp, zalloc_shm(shmobj, sizeof(struct lttng_ust_lib_ring_buffer)));
 327                 buf = shmp(handle, chanb->buf[0].shmp);
 328                 if (!buf)
 329                         goto end;
 330                 set_shmp(buf->self, chanb->buf[0].shmp._ref);
 331                 ret = lib_ring_buffer_create(buf, chanb, -1,
 332                                         handle, shmobj);
 333                 if (ret)
 334                         goto free_bufs;
 335         }
 336         chanb->start_tsc = config->cb.ring_buffer_clock_read(chan);
 337
 338         return 0;
 339
 340 free_bufs:
 341         /* We only free the buffer data upon shm teardown */
 342 end:
 343         return -ENOMEM;
 344 }
 345
 346 /**
 347  * channel_backend_free - destroy the channel
 348  * @chan: the channel
 349  *
 350  * Destroy all channel buffers and frees the channel.
 351  */
 352 void channel_backend_free(struct channel_backend *chanb,
 353                           struct lttng_ust_shm_handle *handle)
 354 {
 355         /* SHM teardown takes care of everything */
 356 }
 357
 358 /**
 359  * lib_ring_buffer_read - read data from ring_buffer_buffer.
 360  * @bufb : buffer backend
 361  * @offset : offset within the buffer
 362  * @dest : destination address
 363  * @len : length to copy to destination
 364  *
 365  * Should be protected by get_subbuf/put_subbuf.
 366  * Returns the length copied.
 367  */
 368 size_t lib_ring_buffer_read(struct lttng_ust_lib_ring_buffer_backend *bufb, size_t offset,
 369                             void *dest, size_t len, struct lttng_ust_shm_handle *handle)
 370 {
 371         struct channel_backend *chanb = &shmp(handle, bufb->chan)->backend;
 372         const struct lttng_ust_lib_ring_buffer_config *config = &chanb->config;
 373         ssize_t orig_len;
 374         struct lttng_ust_lib_ring_buffer_backend_pages_shmp *rpages;
 375         unsigned long sb_bindex, id;
 376         void *src;
 377
 378         orig_len = len;
 379         offset &= chanb->buf_size - 1;
 380
 381         if (caa_unlikely(!len))
 382                 return 0;
 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         src = shmp_index(handle, shmp(handle, rpages->shmp)->p,
 394                         offset & (chanb->subbuf_size - 1));
 395         if (caa_unlikely(!src))
 396                 return 0;
 397         memcpy(dest, src, len);
 398         return orig_len;
 399 }
 400
 401 /**
 402  * lib_ring_buffer_read_cstr - read a C-style string from ring_buffer.
 403  * @bufb : buffer backend
 404  * @offset : offset within the buffer
 405  * @dest : destination address
 406  * @len : destination's length
 407  *
 408  * Return string's length, or -EINVAL on error.
 409  * Should be protected by get_subbuf/put_subbuf.
 410  * Destination length should be at least 1 to hold '\0'.
 411  */
 412 int lib_ring_buffer_read_cstr(struct lttng_ust_lib_ring_buffer_backend *bufb, size_t offset,
 413                               void *dest, size_t len, struct lttng_ust_shm_handle *handle)
 414 {
 415         struct channel_backend *chanb = &shmp(handle, bufb->chan)->backend;
 416         const struct lttng_ust_lib_ring_buffer_config *config = &chanb->config;
 417         ssize_t string_len, orig_offset;
 418         char *str;
 419         struct lttng_ust_lib_ring_buffer_backend_pages_shmp *rpages;
 420         unsigned long sb_bindex, id;
 421
 422         if (caa_unlikely(!len))
 423                 return -EINVAL;
 424         offset &= chanb->buf_size - 1;
 425         orig_offset = offset;
 426         id = bufb->buf_rsb.id;
 427         sb_bindex = subbuffer_id_get_index(config, id);
 428         rpages = shmp_index(handle, bufb->array, sb_bindex);
 429         /*
 430          * Underlying layer should never ask for reads across
 431          * subbuffers.
 432          */
 433         CHAN_WARN_ON(chanb, offset >= chanb->buf_size);
 434         CHAN_WARN_ON(chanb, config->mode == RING_BUFFER_OVERWRITE
 435                      && subbuffer_id_is_noref(config, id));
 436         str = shmp_index(handle, shmp(handle, rpages->shmp)->p, offset & (chanb->subbuf_size - 1));
 437         if (caa_unlikely(!str))
 438                 return -EINVAL;
 439         string_len = strnlen(str, len);
 440         if (dest && len) {
 441                 memcpy(dest, str, string_len);
 442                 ((char *)dest)[0] = 0;
 443         }
 444         return offset - orig_offset;
 445 }
 446
 447 /**
 448  * lib_ring_buffer_read_offset_address - get address of a buffer location
 449  * @bufb : buffer backend
 450  * @offset : offset within the buffer.
 451  *
 452  * Return the address where a given offset is located (for read).
 453  * Should be used to get the current subbuffer header pointer. Given we know
 454  * it's never on a page boundary, it's safe to read/write directly
 455  * from/to this address, as long as the read/write is never bigger than
 456  * a page size.
 457  */
 458 void *lib_ring_buffer_read_offset_address(struct lttng_ust_lib_ring_buffer_backend *bufb,
 459                                           size_t offset,
 460                                           struct lttng_ust_shm_handle *handle)
 461 {
 462         struct lttng_ust_lib_ring_buffer_backend_pages_shmp *rpages;
 463         struct channel_backend *chanb = &shmp(handle, bufb->chan)->backend;
 464         const struct lttng_ust_lib_ring_buffer_config *config = &chanb->config;
 465         unsigned long sb_bindex, id;
 466
 467         offset &= chanb->buf_size - 1;
 468         id = bufb->buf_rsb.id;
 469         sb_bindex = subbuffer_id_get_index(config, id);
 470         rpages = shmp_index(handle, bufb->array, sb_bindex);
 471         CHAN_WARN_ON(chanb, config->mode == RING_BUFFER_OVERWRITE
 472                      && subbuffer_id_is_noref(config, id));
 473         return shmp_index(handle, shmp(handle, rpages->shmp)->p, offset & (chanb->subbuf_size - 1));
 474 }
 475
 476 /**
 477  * lib_ring_buffer_offset_address - get address of a location within the buffer
 478  * @bufb : buffer backend
 479  * @offset : offset within the buffer.
 480  *
 481  * Return the address where a given offset is located.
 482  * Should be used to get the current subbuffer header pointer. Given we know
 483  * it's always at the beginning of a page, it's safe to write directly to this
 484  * address, as long as the write is never bigger than a page size.
 485  */
 486 void *lib_ring_buffer_offset_address(struct lttng_ust_lib_ring_buffer_backend *bufb,
 487                                      size_t offset,
 488                                      struct lttng_ust_shm_handle *handle)
 489 {
 490         size_t sbidx;
 491         struct lttng_ust_lib_ring_buffer_backend_pages_shmp *rpages;
 492         struct channel_backend *chanb = &shmp(handle, bufb->chan)->backend;
 493         const struct lttng_ust_lib_ring_buffer_config *config = &chanb->config;
 494         unsigned long sb_bindex, id;
 495
 496         offset &= chanb->buf_size - 1;
 497         sbidx = offset >> chanb->subbuf_size_order;
 498         id = shmp_index(handle, bufb->buf_wsb, sbidx)->id;
 499         sb_bindex = subbuffer_id_get_index(config, id);
 500         rpages = shmp_index(handle, bufb->array, sb_bindex);
 501         CHAN_WARN_ON(chanb, config->mode == RING_BUFFER_OVERWRITE
 502                      && subbuffer_id_is_noref(config, id));
 503         return shmp_index(handle, shmp(handle, rpages->shmp)->p, offset & (chanb->subbuf_size - 1));
 504 }