include/lttng/lttng.h

   1 /*
   2  * lttng.h
   3  *
   4  * Linux Trace Toolkit Control Library Header File
   5  *
   6  * Copyright (C) 2011 - David Goulet <david.goulet@polymtl.ca>
   7  *
   8  * This library is free software; you can redistribute it and/or modify it
   9  * under the terms of the GNU Lesser General Public License, version 2.1 only,
  10  * as published by the Free Software Foundation.
  11  *
  12  * This library is distributed in the hope that it will be useful, but WITHOUT
  13  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  14  * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
  15  * for more details.
  16  *
  17  * You should have received a copy of the GNU Lesser General Public License
  18  * along with this library; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  20  */
  21
  22 #ifndef LTTNG_H
  23 #define LTTNG_H
  24
  25 #include <limits.h>
  26 #include <stdint.h>
  27 #include <sys/types.h>
  28
  29 /* Error codes that can be returned by API calls */
  30 #include <lttng/lttng-error.h>
  31
  32 #ifdef __cplusplus
  33 extern "C" {
  34 #endif
  35
  36 /*
  37  * Event symbol length. Copied from LTTng kernel ABI.
  38  */
  39 #define LTTNG_SYMBOL_NAME_LEN             256
  40
  41 /*
  42  * Every lttng_event_* structure both apply to kernel event and user-space
  43  * event.
  44  */
  45
  46 /*
  47  * Domain types: the different possible tracers.
  48  */
  49 enum lttng_domain_type {
  50         LTTNG_DOMAIN_KERNEL                   = 1,      /* Linux Kernel tracer. */
  51         LTTNG_DOMAIN_UST                      = 2,      /* Global Userspace tracer. */
  52         LTTNG_DOMAIN_JUL                      = 3,      /* Java Util Logging. */
  53 };
  54
  55 /*
  56  * Instrumentation type of tracing event.
  57  */
  58 enum lttng_event_type {
  59         LTTNG_EVENT_ALL                       = -1,
  60         LTTNG_EVENT_TRACEPOINT                = 0,
  61         LTTNG_EVENT_PROBE                     = 1,
  62         LTTNG_EVENT_FUNCTION                  = 2,
  63         LTTNG_EVENT_FUNCTION_ENTRY            = 3,
  64         LTTNG_EVENT_NOOP                      = 4,
  65         LTTNG_EVENT_SYSCALL                   = 5,
  66 };
  67
  68 /*
  69  * Loglevel information.
  70  */
  71 enum lttng_loglevel_type {
  72         LTTNG_EVENT_LOGLEVEL_ALL              = 0,
  73         LTTNG_EVENT_LOGLEVEL_RANGE            = 1,
  74         LTTNG_EVENT_LOGLEVEL_SINGLE           = 2,
  75 };
  76
  77 /*
  78  * Available loglevels.
  79  */
  80 enum lttng_loglevel {
  81         LTTNG_LOGLEVEL_EMERG                  = 0,
  82         LTTNG_LOGLEVEL_ALERT                  = 1,
  83         LTTNG_LOGLEVEL_CRIT                   = 2,
  84         LTTNG_LOGLEVEL_ERR                    = 3,
  85         LTTNG_LOGLEVEL_WARNING                = 4,
  86         LTTNG_LOGLEVEL_NOTICE                 = 5,
  87         LTTNG_LOGLEVEL_INFO                   = 6,
  88         LTTNG_LOGLEVEL_DEBUG_SYSTEM           = 7,
  89         LTTNG_LOGLEVEL_DEBUG_PROGRAM          = 8,
  90         LTTNG_LOGLEVEL_DEBUG_PROCESS          = 9,
  91         LTTNG_LOGLEVEL_DEBUG_MODULE           = 10,
  92         LTTNG_LOGLEVEL_DEBUG_UNIT             = 11,
  93         LTTNG_LOGLEVEL_DEBUG_FUNCTION         = 12,
  94         LTTNG_LOGLEVEL_DEBUG_LINE             = 13,
  95         LTTNG_LOGLEVEL_DEBUG                  = 14,
  96 };
  97
  98 /*
  99  * LTTng consumer mode
 100  */
 101 enum lttng_event_output {
 102         LTTNG_EVENT_SPLICE                    = 0,
 103         LTTNG_EVENT_MMAP                      = 1,
 104 };
 105
 106 /* Event context possible type */
 107 enum lttng_event_context_type {
 108         LTTNG_EVENT_CONTEXT_PID               = 0,
 109         LTTNG_EVENT_CONTEXT_PERF_COUNTER      = 1,
 110         LTTNG_EVENT_CONTEXT_PROCNAME          = 2,
 111         LTTNG_EVENT_CONTEXT_PRIO              = 3,
 112         LTTNG_EVENT_CONTEXT_NICE              = 4,
 113         LTTNG_EVENT_CONTEXT_VPID              = 5,
 114         LTTNG_EVENT_CONTEXT_TID               = 6,
 115         LTTNG_EVENT_CONTEXT_VTID              = 7,
 116         LTTNG_EVENT_CONTEXT_PPID              = 8,
 117         LTTNG_EVENT_CONTEXT_VPPID             = 9,
 118         LTTNG_EVENT_CONTEXT_PTHREAD_ID        = 10,
 119         LTTNG_EVENT_CONTEXT_HOSTNAME          = 11,
 120         LTTNG_EVENT_CONTEXT_IP                = 12,
 121 };
 122
 123 enum lttng_calibrate_type {
 124         LTTNG_CALIBRATE_FUNCTION              = 0,
 125 };
 126
 127 /* Health component for the health check function. */
 128 enum lttng_health_component {
 129         LTTNG_HEALTH_CMD,
 130         LTTNG_HEALTH_APP_MANAGE,
 131         LTTNG_HEALTH_APP_REG,
 132         LTTNG_HEALTH_KERNEL,
 133         LTTNG_HEALTH_CONSUMER,
 134         LTTNG_HEALTH_HT_CLEANUP,
 135         LTTNG_HEALTH_APP_MANAGE_NOTIFY,
 136         LTTNG_HEALTH_APP_REG_DISPATCH,
 137         LTTNG_HEALTH_ALL,
 138 };
 139
 140 /* Buffer type for a specific domain. */
 141 enum lttng_buffer_type {
 142         LTTNG_BUFFER_PER_PID,   /* Only supported by UST being the default. */
 143         LTTNG_BUFFER_PER_UID,   /* Only supported by UST. */
 144         LTTNG_BUFFER_GLOBAL,    /* Only supported by the Kernel. */
 145 };
 146
 147 /*
 148  * The structures should be initialized to zero before use.
 149  */
 150 #define LTTNG_DOMAIN_PADDING1              12
 151 #define LTTNG_DOMAIN_PADDING2              LTTNG_SYMBOL_NAME_LEN + 32
 152 struct lttng_domain {
 153         enum lttng_domain_type type;
 154         enum lttng_buffer_type buf_type;
 155         char padding[LTTNG_DOMAIN_PADDING1];
 156
 157         union {
 158                 pid_t pid;
 159                 char exec_name[NAME_MAX];
 160                 char padding[LTTNG_DOMAIN_PADDING2];
 161         } attr;
 162 };
 163
 164 /*
 165  * Perf counter attributes
 166  *
 167  * The structures should be initialized to zero before use.
 168  */
 169 #define LTTNG_PERF_EVENT_PADDING1          16
 170 struct lttng_event_perf_counter_ctx {
 171         uint32_t type;
 172         uint64_t config;
 173         char name[LTTNG_SYMBOL_NAME_LEN];
 174
 175         char padding[LTTNG_PERF_EVENT_PADDING1];
 176 };
 177
 178 /*
 179  * Event/channel context
 180  *
 181  * The structures should be initialized to zero before use.
 182  */
 183 #define LTTNG_EVENT_CONTEXT_PADDING1       16
 184 #define LTTNG_EVENT_CONTEXT_PADDING2       LTTNG_SYMBOL_NAME_LEN + 32
 185 struct lttng_event_context {
 186         enum lttng_event_context_type ctx;
 187         char padding[LTTNG_EVENT_CONTEXT_PADDING1];
 188
 189         union {
 190                 struct lttng_event_perf_counter_ctx perf_counter;
 191                 char padding[LTTNG_EVENT_CONTEXT_PADDING2];
 192         } u;
 193 };
 194
 195 /*
 196  * Event probe.
 197  *
 198  * Either addr is used or symbol_name and offset.
 199  *
 200  * The structures should be initialized to zero before use.
 201  */
 202 #define LTTNG_EVENT_PROBE_PADDING1         16
 203 struct lttng_event_probe_attr {
 204         uint64_t addr;
 205
 206         uint64_t offset;
 207         char symbol_name[LTTNG_SYMBOL_NAME_LEN];
 208
 209         char padding[LTTNG_EVENT_PROBE_PADDING1];
 210 };
 211
 212 /*
 213  * Function tracer
 214  *
 215  * The structures should be initialized to zero before use.
 216  */
 217 #define LTTNG_EVENT_FUNCTION_PADDING1      16
 218 struct lttng_event_function_attr {
 219         char symbol_name[LTTNG_SYMBOL_NAME_LEN];
 220
 221         char padding[LTTNG_EVENT_FUNCTION_PADDING1];
 222 };
 223
 224 /*
 225  * Generic lttng event
 226  *
 227  * The structures should be initialized to zero before use.
 228  */
 229 #define LTTNG_EVENT_PADDING1               15
 230 #define LTTNG_EVENT_PADDING2               LTTNG_SYMBOL_NAME_LEN + 32
 231 struct lttng_event {
 232         enum lttng_event_type type;
 233         char name[LTTNG_SYMBOL_NAME_LEN];
 234
 235         enum lttng_loglevel_type loglevel_type;
 236         int loglevel;
 237
 238         int32_t enabled;        /* Does not apply: -1 */
 239         pid_t pid;
 240         unsigned char filter;   /* filter enabled ? */
 241
 242         char padding[LTTNG_EVENT_PADDING1];
 243
 244         /* Per event type configuration */
 245         union {
 246                 struct lttng_event_probe_attr probe;
 247                 struct lttng_event_function_attr ftrace;
 248
 249                 char padding[LTTNG_EVENT_PADDING2];
 250         } attr;
 251 };
 252
 253 enum lttng_event_field_type {
 254         LTTNG_EVENT_FIELD_OTHER                 = 0,
 255         LTTNG_EVENT_FIELD_INTEGER               = 1,
 256         LTTNG_EVENT_FIELD_ENUM                  = 2,
 257         LTTNG_EVENT_FIELD_FLOAT                 = 3,
 258         LTTNG_EVENT_FIELD_STRING                = 4,
 259 };
 260
 261 #define LTTNG_EVENT_FIELD_PADDING       LTTNG_SYMBOL_NAME_LEN + 32
 262 struct lttng_event_field {
 263         char field_name[LTTNG_SYMBOL_NAME_LEN];
 264         enum lttng_event_field_type type;
 265         char padding[LTTNG_EVENT_FIELD_PADDING];
 266         struct lttng_event event;
 267         int nowrite;
 268 };
 269
 270 /*
 271  * Tracer channel attributes. For both kernel and user-space.
 272  *
 273  * The structures should be initialized to zero before use.
 274  */
 275 #define LTTNG_CHANNEL_ATTR_PADDING1        LTTNG_SYMBOL_NAME_LEN + 12
 276 struct lttng_channel_attr {
 277         int overwrite;                      /* 1: overwrite, 0: discard */
 278         uint64_t subbuf_size;               /* bytes */
 279         uint64_t num_subbuf;                /* power of 2 */
 280         unsigned int switch_timer_interval; /* usec */
 281         unsigned int read_timer_interval;   /* usec */
 282         enum lttng_event_output output;     /* splice, mmap */
 283         /* LTTng 2.1 padding limit */
 284         uint64_t tracefile_size;            /* bytes */
 285         uint64_t tracefile_count;           /* number of tracefiles */
 286         /* LTTng 2.3 padding limit */
 287         unsigned int live_timer_interval;   /* usec */
 288
 289         char padding[LTTNG_CHANNEL_ATTR_PADDING1];
 290 };
 291
 292 /*
 293  * Channel information structure. For both kernel and user-space.
 294  *
 295  * The structures should be initialized to zero before use.
 296  */
 297 #define LTTNG_CHANNEL_PADDING1             16
 298 struct lttng_channel {
 299         char name[LTTNG_SYMBOL_NAME_LEN];
 300         uint32_t enabled;
 301         struct lttng_channel_attr attr;
 302
 303         char padding[LTTNG_CHANNEL_PADDING1];
 304 };
 305
 306 #define LTTNG_CALIBRATE_PADDING1           16
 307 struct lttng_calibrate {
 308         enum lttng_calibrate_type type;
 309
 310         char padding[LTTNG_CALIBRATE_PADDING1];
 311 };
 312
 313 /*
 314  * Basic session information.
 315  *
 316  * This is an 'output data' meaning that it only comes *from* the session
 317  * daemon *to* the lttng client. It's basically a 'human' representation of
 318  * tracing entities (here a session).
 319  *
 320  * The structures should be initialized to zero before use.
 321  */
 322 #define LTTNG_SESSION_PADDING1             12
 323 struct lttng_session {
 324         char name[NAME_MAX];
 325         /* The path where traces are written */
 326         char path[PATH_MAX];
 327         uint32_t enabled;       /* enabled/started: 1, disabled/stopped: 0 */
 328         uint32_t snapshot_mode;
 329         unsigned int live_timer_interval;       /* usec */
 330
 331         char padding[LTTNG_SESSION_PADDING1];
 332 };
 333
 334 /*
 335  * Handle used as a context for commands.
 336  *
 337  * The structures should be initialized to zero before use.
 338  */
 339 #define LTTNG_HANDLE_PADDING1              16
 340 struct lttng_handle {
 341         char session_name[NAME_MAX];
 342         struct lttng_domain domain;
 343
 344         char padding[LTTNG_HANDLE_PADDING1];
 345 };
 346
 347 /*
 348  * Public LTTng control API
 349  *
 350  * For functions having an lttng domain type as parameter, if a bad value is
 351  * given, NO default is applied and an error is returned.
 352  *
 353  * On success, all functions of the API return 0 or the size of the allocated
 354  * array (in bytes).
 355  *
 356  * On error, a negative value is returned being a specific lttng-tools error
 357  * code which can be humanly interpreted with lttng_strerror(err).
 358  *
 359  * Exceptions to this are noted below.
 360  */
 361
 362 /*
 363  * Create a handle used as a context for every request made to the library.
 364  *
 365  * This handle contains the session name and lttng domain on which the command
 366  * will be executed.
 367  * The returned pointer will be NULL in case of malloc() error.
 368  */
 369 extern struct lttng_handle *lttng_create_handle(const char *session_name,
 370                 struct lttng_domain *domain);
 371
 372 /*
 373  * Destroy an handle.
 374  *
 375  * It free(3) the data pointer returned by lttng_create_handle(), rendering it
 376  * unusable.
 377  */
 378 extern void lttng_destroy_handle(struct lttng_handle *handle);
 379
 380 /*
 381  * Create a tracing session using a name and an optional URL.
 382  *
 383  * If _url_ is NULL, no consumer is created for the session. The name can't be
 384  * NULL here.
 385  */
 386 extern int lttng_create_session(const char *name, const char *url);
 387
 388 /*
 389  * Create a tracing session that will exclusively be used for snapshot meaning
 390  * the session will be in no output mode and every channel enabled for that
 391  * session will be set in overwrite mode and in mmap output since splice is not
 392  * supported.
 393  *
 394  * If an url is given, it will be used to create a default snapshot output
 395  * using it as a destination. If NULL, no output will be defined and an
 396  * add-output call will be needed.
 397  *
 398  * Name can't be NULL.
 399  */
 400 extern int lttng_create_session_snapshot(const char *name,
 401                 const char *snapshot_url);
 402
 403 /*
 404  * Create a session exclusively used for live reading.
 405  *
 406  * In this mode, the switch-timer parameter is forced for each UST channel, a
 407  * live-switch-timer is enabled for kernel channels, manually setting
 408  * switch-timer is forbidden. Synchronization beacons are sent to the relayd,
 409  * indexes are sent and metadata is checked for each packet.
 410  *
 411  * Returns LTTNG_OK on success or a negative error code.
 412  */
 413 extern int lttng_create_session_live(const char *name, const char *url,
 414                 unsigned int timer_interval);
 415
 416 /*
 417  * Destroy a tracing session.
 418  *
 419  * The session will not be usable anymore, tracing will be stopped for all
 420  * registered traces, and the tracing buffers will be flushed.
 421  *
 422  * The name can't be NULL here.
 423  */
 424 extern int lttng_destroy_session(const char *name);
 425
 426 /*
 427  * List all the tracing sessions.
 428  *
 429  * Return the size (number of entries) of the "lttng_session" array. Caller
 430  * must free(3).
 431  */
 432 extern int lttng_list_sessions(struct lttng_session **sessions);
 433
 434 /*
 435  * List the registered domain(s) of a session.
 436  *
 437  * Return the size (number of entries) of the "lttng_domain" array. Caller
 438  * must free(3).
 439  */
 440 extern int lttng_list_domains(const char *session_name,
 441                 struct lttng_domain **domains);
 442
 443 /*
 444  * List the channel(s) of a session.
 445  *
 446  * Return the size (number of entries) of the "lttng_channel" array. Caller
 447  * must free(3).
 448  */
 449 extern int lttng_list_channels(struct lttng_handle *handle,
 450                 struct lttng_channel **channels);
 451
 452 /*
 453  * List the event(s) of a session channel.
 454  *
 455  * Return the size (number of entries) of the "lttng_event" array.
 456  * Caller must free(3).
 457  */
 458 extern int lttng_list_events(struct lttng_handle *handle,
 459                 const char *channel_name, struct lttng_event **events);
 460
 461 /*
 462  * List the available tracepoints of a specific lttng domain.
 463  *
 464  * Return the size (number of entries) of the "lttng_event" array.
 465  * Caller must free(3).
 466  */
 467 extern int lttng_list_tracepoints(struct lttng_handle *handle,
 468                 struct lttng_event **events);
 469
 470 /*
 471  * List the available tracepoints fields of a specific lttng domain.
 472  *
 473  * Return the size (number of entries) of the "lttng_event_field" array.
 474  * Caller must free(3).
 475  */
 476 extern int lttng_list_tracepoint_fields(struct lttng_handle *handle,
 477                 struct lttng_event_field **fields);
 478
 479 /*
 480  * Check if a session daemon is alive.
 481  *
 482  * Return 1 if alive or 0 if not. On error returns a negative value.
 483  */
 484 extern int lttng_session_daemon_alive(void);
 485
 486 /*
 487  * Set the tracing group for the *current* flow of execution.
 488  *
 489  * On success, returns 0 else a negative value on error being a lttng error
 490  * code found in lttng-error.h
 491  */
 492 extern int lttng_set_tracing_group(const char *name);
 493
 494 /*
 495  * Return a human-readable error message for an lttng-tools error code.
 496  *
 497  * Parameter MUST be a negative value or else you'll get a generic message.
 498  */
 499 extern const char *lttng_strerror(int code);
 500
 501 /*
 502  * This call registers an "outside consumer" for a session and an lttng domain.
 503  * No consumer will be spawned and all fds/commands will go through the socket
 504  * path given (socket_path).
 505  *
 506  * NOTE: At the moment, if you use the liblttng-kconsumer, you can only use the
 507  * command socket. The error socket is not supported yet for roaming consumers.
 508  */
 509 extern int lttng_register_consumer(struct lttng_handle *handle,
 510                 const char *socket_path);
 511
 512 /*
 513  * Start tracing for *all* registered traces (kernel and user-space).
 514  */
 515 extern int lttng_start_tracing(const char *session_name);
 516
 517 /*
 518  * Stop tracing for *all* registered traces (kernel and user-space).
 519  *
 520  * This call will wait for data availability for each domain of the session so
 521  * this can take an abritrary amount of time. However, when returning you have
 522  * the guarantee that the data is ready to be read and analyse. Use the
 523  * _no_wait call below to avoid this behavior.
 524  *
 525  * The session_name can't be NULL.
 526  */
 527 extern int lttng_stop_tracing(const char *session_name);
 528
 529 /*
 530  * Behave exactly like lttng_stop_tracing but does not wait for data
 531  * availability.
 532  */
 533 extern int lttng_stop_tracing_no_wait(const char *session_name);
 534
 535 /*
 536  * Add context to event(s) for a specific channel (or for all).
 537  *
 538  * If channel_name is NULL, a lookup of the event's channel is done. If both
 539  * are NULL, the context is applied to all events of all channels.
 540  *
 541  * Note that whatever event_name value is, a context can not be added to an
 542  * event, so we just ignore it for now.
 543  */
 544 extern int lttng_add_context(struct lttng_handle *handle,
 545                 struct lttng_event_context *ctx, const char *event_name,
 546                 const char *channel_name);
 547
 548 /*
 549  * Create or enable an event (or events) for a channel.
 550  *
 551  * If the event you are trying to enable does not exist, it will be created,
 552  * else it is enabled.
 553  * If channel_name is NULL, the default channel is used (channel0).
 554  *
 555  * The handle and ev params can not be NULL.
 556  */
 557 extern int lttng_enable_event(struct lttng_handle *handle,
 558                 struct lttng_event *ev, const char *channel_name);
 559
 560 /*
 561  * Create or enable an event with a specific filter.
 562  *
 563  * If the event you are trying to enable does not exist, it will be created,
 564  * else it is enabled.
 565  * If ev is NULL, all events are enabled with that filter.
 566  * If channel_name is NULL, the default channel is used (channel0) and created
 567  * if not found.
 568  * If filter_expression is NULL, an event without associated filter is
 569  * created.
 570  */
 571 extern int lttng_enable_event_with_filter(struct lttng_handle *handle,
 572                 struct lttng_event *event, const char *channel_name,
 573                 const char *filter_expression);
 574
 575 /*
 576  * Create or enable a channel.
 577  *
 578  * The chan and handle params can not be NULL.
 579  */
 580 extern int lttng_enable_channel(struct lttng_handle *handle,
 581                 struct lttng_channel *chan);
 582
 583 /*
 584  * Disable event(s) of a channel and domain.
 585  *
 586  * If name is NULL, all events are disabled.
 587  * If channel_name is NULL, the default channel is used (channel0).
 588  */
 589 extern int lttng_disable_event(struct lttng_handle *handle,
 590                 const char *name, const char *channel_name);
 591
 592 /*
 593  * Disable channel.
 594  *
 595  */
 596 extern int lttng_disable_channel(struct lttng_handle *handle,
 597                 const char *name);
 598
 599 /*
 600  * Calibrate LTTng overhead.
 601  *
 602  * The chan and handle params can not be NULL.
 603  */
 604 extern int lttng_calibrate(struct lttng_handle *handle,
 605                 struct lttng_calibrate *calibrate);
 606
 607 /*
 608  * Set the default channel attributes for a specific domain and an allocated
 609  * lttng_channel_attr pointer.
 610  *
 611  * If one or both arguments are NULL, nothing happens.
 612  */
 613 extern void lttng_channel_set_default_attr(struct lttng_domain *domain,
 614                 struct lttng_channel_attr *attr);
 615
 616 /*
 617  * Set URL for a consumer for a session and domain.
 618  *
 619  * Both data and control URL must be defined. If both URLs are the same, only
 620  * the control URL is used even for network streaming.
 621  *
 622  * Default port are 5342 and 5343 respectively for control and data which uses
 623  * the TCP protocol.
 624  */
 625 extern int lttng_set_consumer_url(struct lttng_handle *handle,
 626                 const char *control_url, const char *data_url);
 627
 628 /*
 629  * Enable the consumer for a session and domain.
 630  */
 631 extern LTTNG_DEPRECATED("This call is now obsolete.")
 632 int lttng_enable_consumer(struct lttng_handle *handle);
 633
 634 /*
 635  * Disable consumer for a session and domain.
 636  */
 637 extern LTTNG_DEPRECATED("This call is now obsolete.")
 638 int lttng_disable_consumer(struct lttng_handle *handle);
 639
 640 /*
 641  * Check session daemon health for a specific component.
 642  *
 643  * Return 0 if health is OK or 1 if BAD. A returned value of -1 indicate that
 644  * the control library was not able to connect to the session daemon health
 645  * socket.
 646  *
 647  * Any other positive value is an lttcomm error which can be translate with
 648  * lttng_strerror().
 649  *
 650  * Please see lttng-health-check(3) man page for more information.
 651  */
 652 extern LTTNG_DEPRECATED("This call is now obsolete.")
 653 int lttng_health_check(enum lttng_health_component c);
 654
 655 /*
 656  * For a given session name, this call checks if the data is ready to be read
 657  * or is still being extracted by the consumer(s) (pending) hence not ready to
 658  * be used by any readers.
 659  *
 660  * Return 0 if there is _no_ data pending in the buffers thus having a
 661  * guarantee that the data can be read safely. Else, return 1 if there is still
 662  * traced data is pending. On error, a negative value is returned and readable
 663  * by lttng_strerror().
 664  */
 665 extern int lttng_data_pending(const char *session_name);
 666
 667 #ifdef __cplusplus
 668 }
 669 #endif
 670
 671 #endif /* LTTNG_H */