src/bin/lttng/commands/enable_channels.c

   1 /*
   2  * Copyright (C) 2011 - David Goulet <david.goulet@polymtl.ca>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License, version 2 only,
   6  * as published by the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11  * GNU General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU General Public License along
  14  * with this program; if not, write to the Free Software Foundation, Inc.,
  15  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  16  */
  17
  18 #define _LGPL_SOURCE
  19 #include <popt.h>
  20 #include <stdio.h>
  21 #include <stdlib.h>
  22 #include <string.h>
  23 #include <sys/stat.h>
  24 #include <sys/types.h>
  25 #include <unistd.h>
  26 #include <inttypes.h>
  27 #include <assert.h>
  28 #include <ctype.h>
  29
  30 #include <common/sessiond-comm/sessiond-comm.h>
  31 #include <common/utils.h>
  32 #include <common/mi-lttng.h>
  33
  34 #include "../command.h"
  35 #include "../utils.h"
  36
  37
  38 static struct lttng_channel chan_opts;
  39 static char *opt_channels;
  40 static int opt_kernel;
  41 static char *opt_session_name;
  42 static int opt_userspace;
  43 static char *opt_output;
  44 static int opt_buffer_uid;
  45 static int opt_buffer_pid;
  46 static int opt_buffer_global;
  47 static struct {
  48         bool set;
  49         uint32_t interval;
  50 } opt_monitor_timer;
  51
  52 static struct mi_writer *writer;
  53
  54 #ifdef LTTNG_EMBED_HELP
  55 static const char help_msg[] =
  56 #include <lttng-enable-channel.1.h>
  57 ;
  58 #endif
  59
  60 enum {
  61         OPT_HELP = 1,
  62         OPT_DISCARD,
  63         OPT_OVERWRITE,
  64         OPT_SUBBUF_SIZE,
  65         OPT_NUM_SUBBUF,
  66         OPT_SWITCH_TIMER,
  67         OPT_MONITOR_TIMER,
  68         OPT_READ_TIMER,
  69         OPT_USERSPACE,
  70         OPT_LIST_OPTIONS,
  71         OPT_TRACEFILE_SIZE,
  72         OPT_TRACEFILE_COUNT,
  73 };
  74
  75 static struct lttng_handle *handle;
  76
  77 const char *output_mmap = "mmap";
  78 const char *output_splice = "splice";
  79
  80 static struct poptOption long_options[] = {
  81         /* longName, shortName, argInfo, argPtr, value, descrip, argDesc */
  82         {"help",           'h', POPT_ARG_NONE, 0, OPT_HELP, 0, 0},
  83         {"session",        's', POPT_ARG_STRING, &opt_session_name, 0, 0, 0},
  84         {"kernel",         'k', POPT_ARG_VAL, &opt_kernel, 1, 0, 0},
  85         {"userspace",      'u', POPT_ARG_NONE, 0, OPT_USERSPACE, 0, 0},
  86         {"discard",        0,   POPT_ARG_NONE, 0, OPT_DISCARD, 0, 0},
  87         {"overwrite",      0,   POPT_ARG_NONE, 0, OPT_OVERWRITE, 0, 0},
  88         {"subbuf-size",    0,   POPT_ARG_STRING, 0, OPT_SUBBUF_SIZE, 0, 0},
  89         {"num-subbuf",     0,   POPT_ARG_INT, 0, OPT_NUM_SUBBUF, 0, 0},
  90         {"switch-timer",   0,   POPT_ARG_INT, 0, OPT_SWITCH_TIMER, 0, 0},
  91         {"monitor-timer",  0,   POPT_ARG_INT, 0, OPT_MONITOR_TIMER, 0, 0},
  92         {"read-timer",     0,   POPT_ARG_INT, 0, OPT_READ_TIMER, 0, 0},
  93         {"list-options",   0, POPT_ARG_NONE, NULL, OPT_LIST_OPTIONS, NULL, NULL},
  94         {"output",         0,   POPT_ARG_STRING, &opt_output, 0, 0, 0},
  95         {"buffers-uid",    0,   POPT_ARG_VAL, &opt_buffer_uid, 1, 0, 0},
  96         {"buffers-pid",    0,   POPT_ARG_VAL, &opt_buffer_pid, 1, 0, 0},
  97         {"buffers-global", 0,   POPT_ARG_VAL, &opt_buffer_global, 1, 0, 0},
  98         {"tracefile-size", 'C',   POPT_ARG_INT, 0, OPT_TRACEFILE_SIZE, 0, 0},
  99         {"tracefile-count", 'W',   POPT_ARG_INT, 0, OPT_TRACEFILE_COUNT, 0, 0},
 100         {0, 0, 0, 0, 0, 0, 0}
 101 };
 102
 103 /*
 104  * Set default attributes depending on those already defined from the command
 105  * line.
 106  */
 107 static void set_default_attr(struct lttng_domain *dom)
 108 {
 109         struct lttng_channel_attr default_attr;
 110
 111         memset(&default_attr, 0, sizeof(default_attr));
 112
 113         /* Set attributes */
 114         lttng_channel_set_default_attr(dom, &default_attr);
 115
 116         if (chan_opts.attr.overwrite == -1) {
 117                 chan_opts.attr.overwrite = default_attr.overwrite;
 118         }
 119         if (chan_opts.attr.subbuf_size == -1) {
 120                 chan_opts.attr.subbuf_size = default_attr.subbuf_size;
 121         }
 122         if (chan_opts.attr.num_subbuf == -1) {
 123                 chan_opts.attr.num_subbuf = default_attr.num_subbuf;
 124         }
 125         if (chan_opts.attr.switch_timer_interval == -1) {
 126                 chan_opts.attr.switch_timer_interval = default_attr.switch_timer_interval;
 127         }
 128         if (chan_opts.attr.read_timer_interval == -1) {
 129                 chan_opts.attr.read_timer_interval = default_attr.read_timer_interval;
 130         }
 131         if ((int) chan_opts.attr.output == -1) {
 132                 chan_opts.attr.output = default_attr.output;
 133         }
 134         if (chan_opts.attr.tracefile_count == -1) {
 135                 chan_opts.attr.tracefile_count = default_attr.tracefile_count;
 136         }
 137         if (chan_opts.attr.tracefile_size == -1) {
 138                 chan_opts.attr.tracefile_size = default_attr.tracefile_size;
 139         }
 140 }
 141
 142 /*
 143  * Adding channel using the lttng API.
 144  */
 145 static int enable_channel(char *session_name)
 146 {
 147         struct lttng_channel *channel = NULL;
 148         int ret = CMD_SUCCESS, warn = 0, error = 0, success = 0;
 149         char *channel_name;
 150         struct lttng_domain dom;
 151
 152         memset(&dom, 0, sizeof(dom));
 153
 154         /* Create lttng domain */
 155         if (opt_kernel) {
 156                 dom.type = LTTNG_DOMAIN_KERNEL;
 157                 dom.buf_type = LTTNG_BUFFER_GLOBAL;
 158                 if (opt_buffer_uid || opt_buffer_pid) {
 159                         ERR("Buffer type not supported for domain -k");
 160                         ret = CMD_ERROR;
 161                         goto error;
 162                 }
 163         } else if (opt_userspace) {
 164                 dom.type = LTTNG_DOMAIN_UST;
 165                 if (opt_buffer_pid) {
 166                         dom.buf_type = LTTNG_BUFFER_PER_PID;
 167                 } else {
 168                         if (opt_buffer_global) {
 169                                 ERR("Buffer type not supported for domain -u");
 170                                 ret = CMD_ERROR;
 171                                 goto error;
 172                         }
 173                         dom.buf_type = LTTNG_BUFFER_PER_UID;
 174                 }
 175         } else {
 176                 /* Checked by the caller. */
 177                 assert(0);
 178         }
 179
 180         set_default_attr(&dom);
 181
 182         if (chan_opts.attr.tracefile_size == 0 && chan_opts.attr.tracefile_count) {
 183                 ERR("Missing option --tracefile-size. "
 184                                 "A file count without a size won't do anything.");
 185                 ret = CMD_ERROR;
 186                 goto error;
 187         }
 188
 189         if ((chan_opts.attr.tracefile_size > 0) &&
 190                         (chan_opts.attr.tracefile_size < chan_opts.attr.subbuf_size)) {
 191                 WARN("Tracefile size rounded up from (%" PRIu64 ") to subbuffer size (%" PRIu64 ")",
 192                                 chan_opts.attr.tracefile_size, chan_opts.attr.subbuf_size);
 193                 chan_opts.attr.tracefile_size = chan_opts.attr.subbuf_size;
 194         }
 195
 196         /* Setting channel output */
 197         if (opt_output) {
 198                 if (!strncmp(output_mmap, opt_output, strlen(output_mmap))) {
 199                         chan_opts.attr.output = LTTNG_EVENT_MMAP;
 200                 } else if (!strncmp(output_splice, opt_output, strlen(output_splice))) {
 201                         chan_opts.attr.output = LTTNG_EVENT_SPLICE;
 202                 } else {
 203                         ERR("Unknown output type %s. Possible values are: %s, %s\n",
 204                                         opt_output, output_mmap, output_splice);
 205                         ret = CMD_ERROR;
 206                         goto error;
 207                 }
 208         }
 209
 210         handle = lttng_create_handle(session_name, &dom);
 211         if (handle == NULL) {
 212                 ret = -1;
 213                 goto error;
 214         }
 215
 216         /* Mi open channels element */
 217         if (lttng_opt_mi) {
 218                 assert(writer);
 219                 ret = mi_lttng_channels_open(writer);
 220                 if (ret) {
 221                         ret = CMD_ERROR;
 222                         goto error;
 223                 }
 224         }
 225
 226         /* Strip channel list (format: chan1,chan2,...) */
 227         channel_name = strtok(opt_channels, ",");
 228         while (channel_name != NULL) {
 229                 void *extended_ptr;
 230
 231                 /* Validate channel name's length */
 232                 if (strlen(channel_name) >= NAME_MAX) {
 233                         ERR("Channel name is too long (max. %zu characters)",
 234                                         sizeof(chan_opts.name) - 1);
 235                         error = 1;
 236                         goto skip_enable;
 237                 }
 238
 239                 /*
 240                  * A dynamically-allocated channel is used in order to allow
 241                  * the configuration of extended attributes (post-2.9).
 242                  */
 243                 channel = lttng_channel_create(&dom);
 244                 if (!channel) {
 245                         ERR("Unable to create channel object");
 246                         error = 1;
 247                         goto error;
 248                 }
 249
 250                 /* Copy channel name */
 251                 strcpy(channel->name, channel_name);
 252                 channel->enabled = 1;
 253                 extended_ptr = channel->attr.extended.ptr;
 254                 memcpy(&channel->attr, &chan_opts.attr, sizeof(chan_opts.attr));
 255                 channel->attr.extended.ptr = extended_ptr;
 256                 if (opt_monitor_timer.set) {
 257                         ret = lttng_channel_set_monitor_timer_interval(channel,
 258                                         opt_monitor_timer.interval);
 259                         if (ret) {
 260                                 ERR("Failed to set the channel's monitor timer interval");
 261                                 error = 1;
 262                                 goto error;
 263                         }
 264                 }
 265
 266                 DBG("Enabling channel %s", channel_name);
 267
 268                 ret = lttng_enable_channel(handle, channel);
 269                 if (ret < 0) {
 270                         success = 0;
 271                         switch (-ret) {
 272                         case LTTNG_ERR_KERN_CHAN_EXIST:
 273                         case LTTNG_ERR_UST_CHAN_EXIST:
 274                         case LTTNG_ERR_CHAN_EXIST:
 275                                 WARN("Channel %s: %s (session %s)", channel_name,
 276                                                 lttng_strerror(ret), session_name);
 277                                 warn = 1;
 278                                 break;
 279                         case LTTNG_ERR_INVALID_CHANNEL_NAME:
 280                                 ERR("Invalid channel name: \"%s\". "
 281                                     "Channel names may not start with '.', and "
 282                                     "may not contain '/'.", channel_name);
 283                                 error = 1;
 284                                 break;
 285                         default:
 286                                 ERR("Channel %s: %s (session %s)", channel_name,
 287                                                 lttng_strerror(ret), session_name);
 288                                 error = 1;
 289                                 break;
 290                         }
 291                 } else {
 292                         MSG("%s channel %s enabled for session %s",
 293                                         get_domain_str(dom.type), channel_name, session_name);
 294                         success = 1;
 295                 }
 296
 297 skip_enable:
 298                 if (lttng_opt_mi) {
 299                         /* Mi print the channel element and leave it open */
 300                         ret = mi_lttng_channel(writer, channel, 1);
 301                         if (ret) {
 302                                 ret = CMD_ERROR;
 303                                 goto error;
 304                         }
 305
 306                         /* Individual Success ? */
 307                         ret = mi_lttng_writer_write_element_bool(writer,
 308                                         mi_lttng_element_command_success, success);
 309                         if (ret) {
 310                                 ret = CMD_ERROR;
 311                                 goto error;
 312                         }
 313
 314                         /* Close channel element */
 315                         ret = mi_lttng_writer_close_element(writer);
 316                         if (ret) {
 317                                 ret = CMD_ERROR;
 318                                 goto error;
 319                         }
 320                 }
 321
 322                 /* Next channel */
 323                 channel_name = strtok(NULL, ",");
 324                 lttng_channel_destroy(channel);
 325                 channel = NULL;
 326         }
 327
 328         if (lttng_opt_mi) {
 329                 /* Close channels element */
 330                 ret = mi_lttng_writer_close_element(writer);
 331                 if (ret) {
 332                         ret = CMD_ERROR;
 333                         goto error;
 334                 }
 335         }
 336
 337         ret = CMD_SUCCESS;
 338
 339 error:
 340         if (channel) {
 341                 lttng_channel_destroy(channel);
 342         }
 343         /* If more important error happen bypass the warning */
 344         if (!ret && warn) {
 345                 ret = CMD_WARNING;
 346         }
 347         /* If more important error happen bypass the warning */
 348         if (!ret && error) {
 349                 ret = CMD_ERROR;
 350         }
 351
 352         lttng_destroy_handle(handle);
 353
 354         return ret;
 355 }
 356
 357 /*
 358  * Default value for channel configuration.
 359  */
 360 static void init_channel_config(void)
 361 {
 362         /*
 363          * Put -1 everywhere so we can identify those set by the command line and
 364          * those needed to be set by the default values.
 365          */
 366         memset(&chan_opts.attr, -1, sizeof(chan_opts.attr));
 367         chan_opts.attr.extended.ptr = NULL;
 368 }
 369
 370 /*
 371  * Add channel to trace session
 372  */
 373 int cmd_enable_channels(int argc, const char **argv)
 374 {
 375         int opt, ret = CMD_SUCCESS, command_ret = CMD_SUCCESS, success = 1;
 376         static poptContext pc;
 377         char *session_name = NULL;
 378         char *opt_arg = NULL;
 379
 380         init_channel_config();
 381
 382         pc = poptGetContext(NULL, argc, argv, long_options, 0);
 383         poptReadDefaultConfig(pc, 0);
 384
 385         while ((opt = poptGetNextOpt(pc)) != -1) {
 386                 switch (opt) {
 387                 case OPT_HELP:
 388                         SHOW_HELP();
 389                         goto end;
 390                 case OPT_DISCARD:
 391                         chan_opts.attr.overwrite = 0;
 392                         DBG("Channel set to discard");
 393                         break;
 394                 case OPT_OVERWRITE:
 395                         chan_opts.attr.overwrite = 1;
 396                         DBG("Channel set to overwrite");
 397                         break;
 398                 case OPT_SUBBUF_SIZE:
 399                 {
 400                         uint64_t rounded_size;
 401                         int order;
 402
 403                         /* Parse the size */
 404                         opt_arg = poptGetOptArg(pc);
 405                         if (utils_parse_size_suffix(opt_arg, &chan_opts.attr.subbuf_size) < 0 || !chan_opts.attr.subbuf_size) {
 406                                 ERR("Wrong value in --subbuf-size parameter: %s", opt_arg);
 407                                 ret = CMD_ERROR;
 408                                 goto end;
 409                         }
 410
 411                         order = get_count_order_u64(chan_opts.attr.subbuf_size);
 412                         assert(order >= 0);
 413                         rounded_size = 1ULL << order;
 414                         if (rounded_size < chan_opts.attr.subbuf_size) {
 415                                 ERR("The subbuf size (%" PRIu64 ") is rounded and overflows!",
 416                                                 chan_opts.attr.subbuf_size);
 417                                 ret = CMD_ERROR;
 418                                 goto end;
 419                         }
 420
 421                         if (rounded_size != chan_opts.attr.subbuf_size) {
 422                                 WARN("The subbuf size (%" PRIu64 ") is rounded to the next power of 2 (%" PRIu64 ")",
 423                                                 chan_opts.attr.subbuf_size, rounded_size);
 424                                 chan_opts.attr.subbuf_size = rounded_size;
 425                         }
 426
 427                         /* Should now be power of 2 */
 428                         assert(!((chan_opts.attr.subbuf_size - 1) & chan_opts.attr.subbuf_size));
 429
 430                         DBG("Channel subbuf size set to %" PRIu64, chan_opts.attr.subbuf_size);
 431                         break;
 432                 }
 433                 case OPT_NUM_SUBBUF:
 434                 {
 435                         uint64_t rounded_size;
 436                         int order;
 437
 438                         errno = 0;
 439                         opt_arg = poptGetOptArg(pc);
 440                         chan_opts.attr.num_subbuf = strtoull(opt_arg, NULL, 0);
 441                         if (errno != 0 || !chan_opts.attr.num_subbuf || !isdigit(opt_arg[0])) {
 442                                 ERR("Wrong value in --num-subbuf parameter: %s", opt_arg);
 443                                 ret = CMD_ERROR;
 444                                 goto end;
 445                         }
 446
 447                         order = get_count_order_u64(chan_opts.attr.num_subbuf);
 448                         assert(order >= 0);
 449                         rounded_size = 1ULL << order;
 450                         if (rounded_size < chan_opts.attr.num_subbuf) {
 451                                 ERR("The number of subbuffers (%" PRIu64 ") is rounded and overflows!",
 452                                                 chan_opts.attr.num_subbuf);
 453                                 ret = CMD_ERROR;
 454                                 goto end;
 455                         }
 456
 457                         if (rounded_size != chan_opts.attr.num_subbuf) {
 458                                 WARN("The number of subbuffers (%" PRIu64 ") is rounded to the next power of 2 (%" PRIu64 ")",
 459                                                 chan_opts.attr.num_subbuf, rounded_size);
 460                                 chan_opts.attr.num_subbuf = rounded_size;
 461                         }
 462
 463                         /* Should now be power of 2 */
 464                         assert(!((chan_opts.attr.num_subbuf - 1) & chan_opts.attr.num_subbuf));
 465
 466                         DBG("Channel subbuf num set to %" PRIu64, chan_opts.attr.num_subbuf);
 467                         break;
 468                 }
 469                 case OPT_SWITCH_TIMER:
 470                 {
 471                         unsigned long v;
 472
 473                         errno = 0;
 474                         opt_arg = poptGetOptArg(pc);
 475                         v = strtoul(opt_arg, NULL, 0);
 476                         if (errno != 0 || !isdigit(opt_arg[0])) {
 477                                 ERR("Wrong value in --switch-timer parameter: %s", opt_arg);
 478                                 ret = CMD_ERROR;
 479                                 goto end;
 480                         }
 481                         if (v != (uint32_t) v) {
 482                                 ERR("32-bit overflow in --switch-timer parameter: %s", opt_arg);
 483                                 ret = CMD_ERROR;
 484                                 goto end;
 485                         }
 486                         chan_opts.attr.switch_timer_interval = (uint32_t) v;
 487                         DBG("Channel switch timer interval set to %d", chan_opts.attr.switch_timer_interval);
 488                         break;
 489                 }
 490                 case OPT_READ_TIMER:
 491                 {
 492                         unsigned long v;
 493
 494                         errno = 0;
 495                         opt_arg = poptGetOptArg(pc);
 496                         v = strtoul(opt_arg, NULL, 0);
 497                         if (errno != 0 || !isdigit(opt_arg[0])) {
 498                                 ERR("Wrong value in --read-timer parameter: %s", opt_arg);
 499                                 ret = CMD_ERROR;
 500                                 goto end;
 501                         }
 502                         if (v != (uint32_t) v) {
 503                                 ERR("32-bit overflow in --read-timer parameter: %s", opt_arg);
 504                                 ret = CMD_ERROR;
 505                                 goto end;
 506                         }
 507                         chan_opts.attr.read_timer_interval = (uint32_t) v;
 508                         DBG("Channel read timer interval set to %d", chan_opts.attr.read_timer_interval);
 509                         break;
 510                 }
 511                 case OPT_MONITOR_TIMER:
 512                 {
 513                         unsigned long v;
 514
 515                         errno = 0;
 516                         opt_arg = poptGetOptArg(pc);
 517                         v = strtoul(opt_arg, NULL, 0);
 518                         if (errno != 0 || !isdigit(opt_arg[0])) {
 519                                 ERR("Wrong value in --monitor-timer parameter: %s", opt_arg);
 520                                 ret = CMD_ERROR;
 521                                 goto end;
 522                         }
 523                         if (v != (uint32_t) v) {
 524                                 ERR("32-bit overflow in --monitor-timer parameter: %s", opt_arg);
 525                                 ret = CMD_ERROR;
 526                                 goto end;
 527                         }
 528                         opt_monitor_timer.interval = (uint32_t) v;
 529                         opt_monitor_timer.set = true;
 530                         DBG("Channel monitor timer interval set to %d", opt_monitor_timer.interval);
 531                         break;
 532                 }
 533                 case OPT_USERSPACE:
 534                         opt_userspace = 1;
 535                         break;
 536                 case OPT_TRACEFILE_SIZE:
 537                         opt_arg = poptGetOptArg(pc);
 538                         if (utils_parse_size_suffix(opt_arg, &chan_opts.attr.tracefile_size) < 0) {
 539                                 ERR("Wrong value in --tracefile-size parameter: %s", opt_arg);
 540                                 ret = CMD_ERROR;
 541                                 goto end;
 542                         }
 543                         DBG("Maximum tracefile size set to %" PRIu64,
 544                                         chan_opts.attr.tracefile_size);
 545                         break;
 546                 case OPT_TRACEFILE_COUNT:
 547                 {
 548                         unsigned long v;
 549
 550                         errno = 0;
 551                         opt_arg = poptGetOptArg(pc);
 552                         v = strtoul(opt_arg, NULL, 0);
 553                         if (errno != 0 || !isdigit(opt_arg[0])) {
 554                                 ERR("Wrong value in --tracefile-count parameter: %s", opt_arg);
 555                                 ret = CMD_ERROR;
 556                                 goto end;
 557                         }
 558                         if (v != (uint32_t) v) {
 559                                 ERR("32-bit overflow in --tracefile-count parameter: %s", opt_arg);
 560                                 ret = CMD_ERROR;
 561                                 goto end;
 562                         }
 563                         chan_opts.attr.tracefile_count = (uint32_t) v;
 564                         DBG("Maximum tracefile count set to %" PRIu64,
 565                                         chan_opts.attr.tracefile_count);
 566                         break;
 567                 }
 568                 case OPT_LIST_OPTIONS:
 569                         list_cmd_options(stdout, long_options);
 570                         goto end;
 571                 default:
 572                         ret = CMD_UNDEFINED;
 573                         goto end;
 574                 }
 575         }
 576
 577         ret = print_missing_or_multiple_domains(opt_kernel + opt_userspace);
 578         if (ret) {
 579                 ret = CMD_ERROR;
 580                 goto end;
 581         }
 582
 583         /* Mi check */
 584         if (lttng_opt_mi) {
 585                 writer = mi_lttng_writer_create(fileno(stdout), lttng_opt_mi);
 586                 if (!writer) {
 587                         ret = -LTTNG_ERR_NOMEM;
 588                         goto end;
 589                 }
 590
 591                 /* Open command element */
 592                 ret = mi_lttng_writer_command_open(writer,
 593                                 mi_lttng_element_command_enable_channels);
 594                 if (ret) {
 595                         ret = CMD_ERROR;
 596                         goto end;
 597                 }
 598
 599                 /* Open output element */
 600                 ret = mi_lttng_writer_open_element(writer,
 601                                 mi_lttng_element_command_output);
 602                 if (ret) {
 603                         ret = CMD_ERROR;
 604                         goto end;
 605                 }
 606         }
 607
 608         opt_channels = (char*) poptGetArg(pc);
 609         if (opt_channels == NULL) {
 610                 ERR("Missing channel name.\n");
 611                 ret = CMD_ERROR;
 612                 success = 0;
 613                 goto mi_closing;
 614         }
 615
 616         if (!opt_session_name) {
 617                 session_name = get_session_name();
 618                 if (session_name == NULL) {
 619                         command_ret = CMD_ERROR;
 620                         success = 0;
 621                         goto mi_closing;
 622                 }
 623         } else {
 624                 session_name = opt_session_name;
 625         }
 626
 627         command_ret = enable_channel(session_name);
 628         if (command_ret) {
 629                 success = 0;
 630         }
 631
 632 mi_closing:
 633         /* Mi closing */
 634         if (lttng_opt_mi) {
 635                 /* Close  output element */
 636                 ret = mi_lttng_writer_close_element(writer);
 637                 if (ret) {
 638                         goto end;
 639                 }
 640
 641                 /* Success ? */
 642                 ret = mi_lttng_writer_write_element_bool(writer,
 643                                 mi_lttng_element_command_success, success);
 644                 if (ret) {
 645                         goto end;
 646                 }
 647
 648                 /* Command element close */
 649                 ret = mi_lttng_writer_command_close(writer);
 650                 if (ret) {
 651                         goto end;
 652                 }
 653         }
 654
 655 end:
 656         /* Mi clean-up */
 657         if (writer && mi_lttng_writer_destroy(writer)) {
 658                 /* Preserve original error code */
 659                 ret = ret ? ret : LTTNG_ERR_MI_IO_FAIL;
 660         }
 661
 662         if (!opt_session_name && session_name) {
 663                 free(session_name);
 664         }
 665
 666         /* Overwrite ret if an error occurred when enable_channel */
 667         ret = command_ret ? command_ret : ret;
 668         poptFreeContext(pc);
 669         return ret;
 670 }