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