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