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