src/common/kernel-consumer/kernel-consumer.c

   1 /*
   2  * Copyright (C) 2011 - Julien Desfossez <julien.desfossez@polymtl.ca>
   3  *                      Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License, version 2 only,
   7  * as published by the Free Software Foundation.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License along
  15  * with this program; if not, write to the Free Software Foundation, Inc.,
  16  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  17  */
  18
  19 #define _GNU_SOURCE
  20 #include <assert.h>
  21 #include <poll.h>
  22 #include <pthread.h>
  23 #include <stdlib.h>
  24 #include <string.h>
  25 #include <sys/mman.h>
  26 #include <sys/socket.h>
  27 #include <sys/types.h>
  28 #include <unistd.h>
  29 #include <sys/stat.h>
  30
  31 #include <common/common.h>
  32 #include <common/kernel-ctl/kernel-ctl.h>
  33 #include <common/sessiond-comm/sessiond-comm.h>
  34 #include <common/compat/fcntl.h>
  35
  36 #include "kernel-consumer.h"
  37
  38 extern struct lttng_consumer_global_data consumer_data;
  39 extern int consumer_poll_timeout;
  40 extern volatile int consumer_quit;
  41
  42 /*
  43  * Mmap the ring buffer, read it and write the data to the tracefile.
  44  *
  45  * Returns the number of bytes written
  46  */
  47 ssize_t lttng_kconsumer_on_read_subbuffer_mmap(
  48                 struct lttng_consumer_local_data *ctx,
  49                 struct lttng_consumer_stream *stream, unsigned long len)
  50 {
  51         unsigned long mmap_offset;
  52         ssize_t ret = 0;
  53         off_t orig_offset = stream->out_fd_offset;
  54         int fd = stream->wait_fd;
  55         int outfd = stream->out_fd;
  56
  57         /* get the offset inside the fd to mmap */
  58         ret = kernctl_get_mmap_read_offset(fd, &mmap_offset);
  59         if (ret != 0) {
  60                 errno = -ret;
  61                 perror("kernctl_get_mmap_read_offset");
  62                 goto end;
  63         }
  64
  65         while (len > 0) {
  66                 ret = write(outfd, stream->mmap_base + mmap_offset, len);
  67                 if (ret >= len) {
  68                         len = 0;
  69                 } else if (ret < 0) {
  70                         errno = -ret;
  71                         perror("Error in file write");
  72                         goto end;
  73                 }
  74                 /* This won't block, but will start writeout asynchronously */
  75                 lttng_sync_file_range(outfd, stream->out_fd_offset, ret,
  76                                 SYNC_FILE_RANGE_WRITE);
  77                 stream->out_fd_offset += ret;
  78         }
  79
  80         lttng_consumer_sync_trace_file(stream, orig_offset);
  81
  82         goto end;
  83
  84 end:
  85         return ret;
  86 }
  87
  88 /*
  89  * Splice the data from the ring buffer to the tracefile.
  90  *
  91  * Returns the number of bytes spliced.
  92  */
  93 ssize_t lttng_kconsumer_on_read_subbuffer_splice(
  94                 struct lttng_consumer_local_data *ctx,
  95                 struct lttng_consumer_stream *stream, unsigned long len)
  96 {
  97         ssize_t ret = 0;
  98         loff_t offset = 0;
  99         off_t orig_offset = stream->out_fd_offset;
 100         int fd = stream->wait_fd;
 101         int outfd = stream->out_fd;
 102
 103         while (len > 0) {
 104                 DBG("splice chan to pipe offset %lu (fd : %d)",
 105                                 (unsigned long)offset, fd);
 106                 ret = splice(fd, &offset, ctx->consumer_thread_pipe[1], NULL, len,
 107                                 SPLICE_F_MOVE | SPLICE_F_MORE);
 108                 DBG("splice chan to pipe ret %zd", ret);
 109                 if (ret < 0) {
 110                         errno = -ret;
 111                         perror("Error in relay splice");
 112                         goto splice_error;
 113                 }
 114
 115                 ret = splice(ctx->consumer_thread_pipe[0], NULL, outfd, NULL, ret,
 116                                 SPLICE_F_MOVE | SPLICE_F_MORE);
 117                 DBG("splice pipe to file %zd", ret);
 118                 if (ret < 0) {
 119                         errno = -ret;
 120                         perror("Error in file splice");
 121                         goto splice_error;
 122                 }
 123                 len -= ret;
 124                 /* This won't block, but will start writeout asynchronously */
 125                 lttng_sync_file_range(outfd, stream->out_fd_offset, ret,
 126                                 SYNC_FILE_RANGE_WRITE);
 127                 stream->out_fd_offset += ret;
 128         }
 129         lttng_consumer_sync_trace_file(stream, orig_offset);
 130
 131         goto end;
 132
 133 splice_error:
 134         /* send the appropriate error description to sessiond */
 135         switch(ret) {
 136         case EBADF:
 137                 lttng_consumer_send_error(ctx, CONSUMERD_SPLICE_EBADF);
 138                 break;
 139         case EINVAL:
 140                 lttng_consumer_send_error(ctx, CONSUMERD_SPLICE_EINVAL);
 141                 break;
 142         case ENOMEM:
 143                 lttng_consumer_send_error(ctx, CONSUMERD_SPLICE_ENOMEM);
 144                 break;
 145         case ESPIPE:
 146                 lttng_consumer_send_error(ctx, CONSUMERD_SPLICE_ESPIPE);
 147                 break;
 148         }
 149
 150 end:
 151         return ret;
 152 }
 153
 154 /*
 155  * Take a snapshot for a specific fd
 156  *
 157  * Returns 0 on success, < 0 on error
 158  */
 159 int lttng_kconsumer_take_snapshot(struct lttng_consumer_local_data *ctx,
 160                 struct lttng_consumer_stream *stream)
 161 {
 162         int ret = 0;
 163         int infd = stream->wait_fd;
 164
 165         ret = kernctl_snapshot(infd);
 166         if (ret != 0) {
 167                 errno = -ret;
 168                 perror("Getting sub-buffer snapshot.");
 169         }
 170
 171         return ret;
 172 }
 173
 174 /*
 175  * Get the produced position
 176  *
 177  * Returns 0 on success, < 0 on error
 178  */
 179 int lttng_kconsumer_get_produced_snapshot(
 180                 struct lttng_consumer_local_data *ctx,
 181                 struct lttng_consumer_stream *stream,
 182                 unsigned long *pos)
 183 {
 184         int ret;
 185         int infd = stream->wait_fd;
 186
 187         ret = kernctl_snapshot_get_produced(infd, pos);
 188         if (ret != 0) {
 189                 errno = -ret;
 190                 perror("kernctl_snapshot_get_produced");
 191         }
 192
 193         return ret;
 194 }
 195
 196 int lttng_kconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
 197                 int sock, struct pollfd *consumer_sockpoll)
 198 {
 199         ssize_t ret;
 200         struct lttcomm_consumer_msg msg;
 201
 202         ret = lttcomm_recv_unix_sock(sock, &msg, sizeof(msg));
 203         if (ret != sizeof(msg)) {
 204                 lttng_consumer_send_error(ctx, CONSUMERD_ERROR_RECV_CMD);
 205                 return ret;
 206         }
 207         if (msg.cmd_type == LTTNG_CONSUMER_STOP) {
 208                 return -ENOENT;
 209         }
 210
 211         switch (msg.cmd_type) {
 212         case LTTNG_CONSUMER_ADD_CHANNEL:
 213         {
 214                 struct lttng_consumer_channel *new_channel;
 215
 216                 DBG("consumer_add_channel %d", msg.u.channel.channel_key);
 217                 new_channel = consumer_allocate_channel(msg.u.channel.channel_key,
 218                                 -1, -1,
 219                                 msg.u.channel.mmap_len,
 220                                 msg.u.channel.max_sb_size);
 221                 if (new_channel == NULL) {
 222                         lttng_consumer_send_error(ctx, CONSUMERD_OUTFD_ERROR);
 223                         goto end_nosignal;
 224                 }
 225                 if (ctx->on_recv_channel != NULL) {
 226                         ret = ctx->on_recv_channel(new_channel);
 227                         if (ret == 0) {
 228                                 consumer_add_channel(new_channel);
 229                         } else if (ret < 0) {
 230                                 goto end_nosignal;
 231                         }
 232                 } else {
 233                         consumer_add_channel(new_channel);
 234                 }
 235                 goto end_nosignal;
 236         }
 237         case LTTNG_CONSUMER_ADD_STREAM:
 238         {
 239                 struct lttng_consumer_stream *new_stream;
 240                 int fd;
 241
 242                 /* block */
 243                 if (lttng_consumer_poll_socket(consumer_sockpoll) < 0) {
 244                         return -EINTR;
 245                 }
 246                 ret = lttcomm_recv_fds_unix_sock(sock, &fd, 1);
 247                 if (ret != sizeof(fd)) {
 248                         lttng_consumer_send_error(ctx, CONSUMERD_ERROR_RECV_FD);
 249                         return ret;
 250                 }
 251
 252                 DBG("consumer_add_stream %s (%d)", msg.u.stream.path_name,
 253                         fd);
 254                 new_stream = consumer_allocate_stream(msg.u.stream.channel_key,
 255                                 msg.u.stream.stream_key,
 256                                 fd, fd,
 257                                 msg.u.stream.state,
 258                                 msg.u.stream.mmap_len,
 259                                 msg.u.stream.output,
 260                                 msg.u.stream.path_name,
 261                                 msg.u.stream.uid,
 262                                 msg.u.stream.gid);
 263                 if (new_stream == NULL) {
 264                         lttng_consumer_send_error(ctx, CONSUMERD_OUTFD_ERROR);
 265                         goto end;
 266                 }
 267                 if (ctx->on_recv_stream != NULL) {
 268                         ret = ctx->on_recv_stream(new_stream);
 269                         if (ret == 0) {
 270                                 consumer_add_stream(new_stream);
 271                         } else if (ret < 0) {
 272                                 goto end;
 273                         }
 274                 } else {
 275                         consumer_add_stream(new_stream);
 276                 }
 277                 break;
 278         }
 279         case LTTNG_CONSUMER_UPDATE_STREAM:
 280         {
 281                 if (ctx->on_update_stream != NULL) {
 282                         ret = ctx->on_update_stream(msg.u.stream.stream_key, msg.u.stream.state);
 283                         if (ret == 0) {
 284                                 consumer_change_stream_state(msg.u.stream.stream_key, msg.u.stream.state);
 285                         } else if (ret < 0) {
 286                                 goto end;
 287                         }
 288                 } else {
 289                         consumer_change_stream_state(msg.u.stream.stream_key,
 290                                 msg.u.stream.state);
 291                 }
 292                 break;
 293         }
 294         default:
 295                 break;
 296         }
 297 end:
 298         /*
 299          * Wake-up the other end by writing a null byte in the pipe
 300          * (non-blocking). Important note: Because writing into the
 301          * pipe is non-blocking (and therefore we allow dropping wakeup
 302          * data, as long as there is wakeup data present in the pipe
 303          * buffer to wake up the other end), the other end should
 304          * perform the following sequence for waiting:
 305          * 1) empty the pipe (reads).
 306          * 2) perform update operation.
 307          * 3) wait on the pipe (poll).
 308          */
 309         do {
 310                 ret = write(ctx->consumer_poll_pipe[1], "", 1);
 311         } while (ret == -1UL && errno == EINTR);
 312 end_nosignal:
 313         return 0;
 314 }
 315
 316 /*
 317  * Consume data on a file descriptor and write it on a trace file.
 318  */
 319 ssize_t lttng_kconsumer_read_subbuffer(struct lttng_consumer_stream *stream,
 320                 struct lttng_consumer_local_data *ctx)
 321 {
 322         unsigned long len;
 323         int err;
 324         ssize_t ret = 0;
 325         int infd = stream->wait_fd;
 326
 327         DBG("In read_subbuffer (infd : %d)", infd);
 328         /* Get the next subbuffer */
 329         err = kernctl_get_next_subbuf(infd);
 330         if (err != 0) {
 331                 /*
 332                  * This is a debug message even for single-threaded consumer,
 333                  * because poll() have more relaxed criterions than get subbuf,
 334                  * so get_subbuf may fail for short race windows where poll()
 335                  * would issue wakeups.
 336                  */
 337                 DBG("Reserving sub buffer failed (everything is normal, "
 338                                 "it is due to concurrency)");
 339                 goto end;
 340         }
 341
 342         switch (stream->output) {
 343                 case LTTNG_EVENT_SPLICE:
 344                         /* read the whole subbuffer */
 345                         err = kernctl_get_padded_subbuf_size(infd, &len);
 346                         if (err != 0) {
 347                                 errno = -ret;
 348                                 perror("Getting sub-buffer len failed.");
 349                                 goto end;
 350                         }
 351
 352                         /* splice the subbuffer to the tracefile */
 353                         ret = lttng_consumer_on_read_subbuffer_splice(ctx, stream, len);
 354                         if (ret < 0) {
 355                                 /*
 356                                  * display the error but continue processing to try
 357                                  * to release the subbuffer
 358                                  */
 359                                 ERR("Error splicing to tracefile");
 360                         }
 361                         break;
 362                 case LTTNG_EVENT_MMAP:
 363                         /* read the used subbuffer size */
 364                         err = kernctl_get_padded_subbuf_size(infd, &len);
 365                         if (err != 0) {
 366                                 errno = -ret;
 367                                 perror("Getting sub-buffer len failed.");
 368                                 goto end;
 369                         }
 370                         /* write the subbuffer to the tracefile */
 371                         ret = lttng_consumer_on_read_subbuffer_mmap(ctx, stream, len);
 372                         if (ret < 0) {
 373                                 /*
 374                                  * display the error but continue processing to try
 375                                  * to release the subbuffer
 376                                  */
 377                                 ERR("Error writing to tracefile");
 378                         }
 379                         break;
 380                 default:
 381                         ERR("Unknown output method");
 382                         ret = -1;
 383         }
 384
 385         err = kernctl_put_next_subbuf(infd);
 386         if (err != 0) {
 387                 errno = -ret;
 388                 if (errno == EFAULT) {
 389                         perror("Error in unreserving sub buffer\n");
 390                 } else if (errno == EIO) {
 391                         /* Should never happen with newer LTTng versions */
 392                         perror("Reader has been pushed by the writer, last sub-buffer corrupted.");
 393                 }
 394                 goto end;
 395         }
 396
 397 end:
 398         return ret;
 399 }
 400
 401 int lttng_kconsumer_on_recv_stream(struct lttng_consumer_stream *stream)
 402 {
 403         int ret;
 404
 405         /* Opening the tracefile in write mode */
 406         if (stream->path_name != NULL) {
 407                 ret = run_as_open(stream->path_name,
 408                                 O_WRONLY|O_CREAT|O_TRUNC,
 409                                 S_IRWXU|S_IRWXG|S_IRWXO,
 410                                 stream->uid, stream->gid);
 411                 if (ret < 0) {
 412                         ERR("Opening %s", stream->path_name);
 413                         perror("open");
 414                         goto error;
 415                 }
 416                 stream->out_fd = ret;
 417         }
 418
 419         if (stream->output == LTTNG_EVENT_MMAP) {
 420                 /* get the len of the mmap region */
 421                 unsigned long mmap_len;
 422
 423                 ret = kernctl_get_mmap_len(stream->wait_fd, &mmap_len);
 424                 if (ret != 0) {
 425                         errno = -ret;
 426                         perror("kernctl_get_mmap_len");
 427                         goto error_close_fd;
 428                 }
 429                 stream->mmap_len = (size_t) mmap_len;
 430
 431                 stream->mmap_base = mmap(NULL, stream->mmap_len,
 432                                 PROT_READ, MAP_PRIVATE, stream->wait_fd, 0);
 433                 if (stream->mmap_base == MAP_FAILED) {
 434                         perror("Error mmaping");
 435                         ret = -1;
 436                         goto error_close_fd;
 437                 }
 438         }
 439
 440         /* we return 0 to let the library handle the FD internally */
 441         return 0;
 442
 443 error_close_fd:
 444         {
 445                 int err;
 446
 447                 err = close(stream->out_fd);
 448                 assert(!err);
 449         }
 450 error:
 451         return ret;
 452 }
 453