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 /*
  27  * Necessary to include the fixed width type limits on glibc versions older
  28  * than 2.18 when building with a C++ compiler.
  29  */
  30 #ifndef __STDC_LIMIT_MACROS
  31 #define __STDC_LIMIT_MACROS
  32 #include <stdint.h>
  33 #undef __STDC_LIMIT_MACROS
  34 #else /* #ifndef __STDC_LIMIT_MACROS */
  35 #include <stdint.h>
  36 #endif /* #else #ifndef __STDC_LIMIT_MACROS */
  37 #include <sys/types.h>
  38
  39 /* Error codes that can be returned by API calls */
  40 #include <lttng/lttng-error.h>
  41
  42 #ifdef __cplusplus
  43 extern "C" {
  44 #endif
  45
  46 /*
  47  * Event symbol length. Copied from LTTng kernel ABI.
  48  */
  49 #define LTTNG_SYMBOL_NAME_LEN             256
  50
  51 /*
  52  * Every lttng_event_* structure both apply to kernel event and user-space
  53  * event.
  54  */
  55
  56 /*
  57  * Domain types: the different possible tracers.
  58  */
  59 enum lttng_domain_type {
  60         LTTNG_DOMAIN_KERNEL                   = 1,
  61         LTTNG_DOMAIN_UST                      = 2,
  62
  63         /*
  64          * For now, the domains below are not implemented. However, we keep them
  65          * here in order to retain their enum values for future development. Note
  66          * that it is on the roadmap to implement them.
  67          *
  68         LTTNG_DOMAIN_UST_EXEC_NAME            = 3,
  69         LTTNG_DOMAIN_UST_PID                  = 4,
  70         LTTNG_DOMAIN_UST_PID_FOLLOW_CHILDREN  = 5,
  71         */
  72 };
  73
  74 /*
  75  * Instrumentation type of tracing event.
  76  */
  77 enum lttng_event_type {
  78         LTTNG_EVENT_ALL                       = -1,
  79         LTTNG_EVENT_TRACEPOINT                = 0,
  80         LTTNG_EVENT_PROBE                     = 1,
  81         LTTNG_EVENT_FUNCTION                  = 2,
  82         LTTNG_EVENT_FUNCTION_ENTRY            = 3,
  83         LTTNG_EVENT_NOOP                      = 4,
  84         LTTNG_EVENT_SYSCALL                   = 5,
  85 };
  86
  87 /*
  88  * Loglevel information.
  89  */
  90 enum lttng_loglevel_type {
  91         LTTNG_EVENT_LOGLEVEL_ALL              = 0,
  92         LTTNG_EVENT_LOGLEVEL_RANGE            = 1,
  93         LTTNG_EVENT_LOGLEVEL_SINGLE           = 2,
  94 };
  95
  96 /*
  97  * Available loglevels.
  98  */
  99 enum lttng_loglevel {
 100         LTTNG_LOGLEVEL_EMERG                  = 0,
 101         LTTNG_LOGLEVEL_ALERT                  = 1,
 102         LTTNG_LOGLEVEL_CRIT                   = 2,
 103         LTTNG_LOGLEVEL_ERR                    = 3,
 104         LTTNG_LOGLEVEL_WARNING                = 4,
 105         LTTNG_LOGLEVEL_NOTICE                 = 5,
 106         LTTNG_LOGLEVEL_INFO                   = 6,
 107         LTTNG_LOGLEVEL_DEBUG_SYSTEM           = 7,
 108         LTTNG_LOGLEVEL_DEBUG_PROGRAM          = 8,
 109         LTTNG_LOGLEVEL_DEBUG_PROCESS          = 9,
 110         LTTNG_LOGLEVEL_DEBUG_MODULE           = 10,
 111         LTTNG_LOGLEVEL_DEBUG_UNIT             = 11,
 112         LTTNG_LOGLEVEL_DEBUG_FUNCTION         = 12,
 113         LTTNG_LOGLEVEL_DEBUG_LINE             = 13,
 114         LTTNG_LOGLEVEL_DEBUG                  = 14,
 115 };
 116
 117 /*
 118  * LTTng consumer mode
 119  */
 120 enum lttng_event_output {
 121         LTTNG_EVENT_SPLICE                    = 0,
 122         LTTNG_EVENT_MMAP                      = 1,
 123 };
 124
 125 /* Event context possible type */
 126 enum lttng_event_context_type {
 127         LTTNG_EVENT_CONTEXT_PID               = 0,
 128         LTTNG_EVENT_CONTEXT_PERF_COUNTER      = 1,
 129         LTTNG_EVENT_CONTEXT_PROCNAME          = 2,
 130         LTTNG_EVENT_CONTEXT_PRIO              = 3,
 131         LTTNG_EVENT_CONTEXT_NICE              = 4,
 132         LTTNG_EVENT_CONTEXT_VPID              = 5,
 133         LTTNG_EVENT_CONTEXT_TID               = 6,
 134         LTTNG_EVENT_CONTEXT_VTID              = 7,
 135         LTTNG_EVENT_CONTEXT_PPID              = 8,
 136         LTTNG_EVENT_CONTEXT_VPPID             = 9,
 137         LTTNG_EVENT_CONTEXT_PTHREAD_ID        = 10,
 138         LTTNG_EVENT_CONTEXT_HOSTNAME          = 11,
 139         LTTNG_EVENT_CONTEXT_IP                = 12,
 140 };
 141
 142 enum lttng_calibrate_type {
 143         LTTNG_CALIBRATE_FUNCTION              = 0,
 144 };
 145
 146 /* Health component for the health check function. */
 147 enum lttng_health_component {
 148         LTTNG_HEALTH_CMD,
 149         LTTNG_HEALTH_APP_MANAGE,
 150         LTTNG_HEALTH_APP_REG,
 151         LTTNG_HEALTH_KERNEL,
 152         LTTNG_HEALTH_CONSUMER,
 153         LTTNG_HEALTH_HT_CLEANUP,
 154         LTTNG_HEALTH_APP_MANAGE_NOTIFY,
 155         LTTNG_HEALTH_APP_REG_DISPATCH,
 156         LTTNG_HEALTH_ALL,
 157 };
 158
 159 /* Buffer type for a specific domain. */
 160 enum lttng_buffer_type {
 161         LTTNG_BUFFER_PER_PID,   /* Only supported by UST being the default. */
 162         LTTNG_BUFFER_PER_UID,   /* Only supported by UST. */
 163         LTTNG_BUFFER_GLOBAL,    /* Only supported by the Kernel. */
 164 };
 165
 166 /*
 167  * The structures should be initialized to zero before use.
 168  */
 169 #define LTTNG_DOMAIN_PADDING1              12
 170 #define LTTNG_DOMAIN_PADDING2              LTTNG_SYMBOL_NAME_LEN + 32
 171 struct lttng_domain {
 172         enum lttng_domain_type type;
 173         enum lttng_buffer_type buf_type;
 174         char padding[LTTNG_DOMAIN_PADDING1];
 175
 176         union {
 177                 pid_t pid;
 178                 char exec_name[NAME_MAX];
 179                 char padding[LTTNG_DOMAIN_PADDING2];
 180         } attr;
 181 };
 182
 183 /*
 184  * Perf counter attributes
 185  *
 186  * The structures should be initialized to zero before use.
 187  */
 188 #define LTTNG_PERF_EVENT_PADDING1          16
 189 struct lttng_event_perf_counter_ctx {
 190         uint32_t type;
 191         uint64_t config;
 192         char name[LTTNG_SYMBOL_NAME_LEN];
 193
 194         char padding[LTTNG_PERF_EVENT_PADDING1];
 195 };
 196
 197 /*
 198  * Event/channel context
 199  *
 200  * The structures should be initialized to zero before use.
 201  */
 202 #define LTTNG_EVENT_CONTEXT_PADDING1       16
 203 #define LTTNG_EVENT_CONTEXT_PADDING2       LTTNG_SYMBOL_NAME_LEN + 32
 204 struct lttng_event_context {
 205         enum lttng_event_context_type ctx;
 206         char padding[LTTNG_EVENT_CONTEXT_PADDING1];
 207
 208         union {
 209                 struct lttng_event_perf_counter_ctx perf_counter;
 210                 char padding[LTTNG_EVENT_CONTEXT_PADDING2];
 211         } u;
 212 };
 213
 214 /*
 215  * Event probe.
 216  *
 217  * Either addr is used or symbol_name and offset.
 218  *
 219  * The structures should be initialized to zero before use.
 220  */
 221 #define LTTNG_EVENT_PROBE_PADDING1         16
 222 struct lttng_event_probe_attr {
 223         uint64_t addr;
 224
 225         uint64_t offset;
 226         char symbol_name[LTTNG_SYMBOL_NAME_LEN];
 227
 228         char padding[LTTNG_EVENT_PROBE_PADDING1];
 229 };
 230
 231 /*
 232  * Function tracer
 233  *
 234  * The structures should be initialized to zero before use.
 235  */
 236 #define LTTNG_EVENT_FUNCTION_PADDING1      16
 237 struct lttng_event_function_attr {
 238         char symbol_name[LTTNG_SYMBOL_NAME_LEN];
 239
 240         char padding[LTTNG_EVENT_FUNCTION_PADDING1];
 241 };
 242
 243 /*
 244  * Generic lttng event
 245  *
 246  * The structures should be initialized to zero before use.
 247  */
 248 #define LTTNG_EVENT_PADDING1               15
 249 #define LTTNG_EVENT_PADDING2               LTTNG_SYMBOL_NAME_LEN + 32
 250 struct lttng_event {
 251         enum lttng_event_type type;
 252         char name[LTTNG_SYMBOL_NAME_LEN];
 253
 254         enum lttng_loglevel_type loglevel_type;
 255         int loglevel;
 256
 257         int32_t enabled;        /* Does not apply: -1 */
 258         pid_t pid;
 259         unsigned char filter;   /* filter enabled ? */
 260
 261         char padding[LTTNG_EVENT_PADDING1];
 262
 263         /* Per event type configuration */
 264         union {
 265                 struct lttng_event_probe_attr probe;
 266                 struct lttng_event_function_attr ftrace;
 267
 268                 char padding[LTTNG_EVENT_PADDING2];
 269         } attr;
 270 };
 271
 272 enum lttng_event_field_type {
 273         LTTNG_EVENT_FIELD_OTHER                 = 0,
 274         LTTNG_EVENT_FIELD_INTEGER               = 1,
 275         LTTNG_EVENT_FIELD_ENUM                  = 2,
 276         LTTNG_EVENT_FIELD_FLOAT                 = 3,
 277         LTTNG_EVENT_FIELD_STRING                = 4,
 278 };
 279
 280 #define LTTNG_EVENT_FIELD_PADDING       LTTNG_SYMBOL_NAME_LEN + 32
 281 struct lttng_event_field {
 282         char field_name[LTTNG_SYMBOL_NAME_LEN];
 283         enum lttng_event_field_type type;
 284         char padding[LTTNG_EVENT_FIELD_PADDING];
 285         struct lttng_event event;
 286         int nowrite;
 287 };
 288
 289 /*
 290  * Tracer channel attributes. For both kernel and user-space.
 291  *
 292  * The structures should be initialized to zero before use.
 293  */
 294 #define LTTNG_CHANNEL_ATTR_PADDING1        LTTNG_SYMBOL_NAME_LEN + 16
 295 struct lttng_channel_attr {
 296         int overwrite;                      /* 1: overwrite, 0: discard */
 297         uint64_t subbuf_size;               /* bytes */
 298         uint64_t num_subbuf;                /* power of 2 */
 299         unsigned int switch_timer_interval; /* usec */
 300         unsigned int read_timer_interval;   /* usec */
 301         enum lttng_event_output output;     /* splice, mmap */
 302         /* LTTng 2.1 padding limit */
 303         uint64_t tracefile_size;            /* bytes */
 304         uint64_t tracefile_count;           /* number of tracefiles */
 305
 306         char padding[LTTNG_CHANNEL_ATTR_PADDING1];
 307 };
 308
 309 /*
 310  * Channel information structure. For both kernel and user-space.
 311  *
 312  * The structures should be initialized to zero before use.
 313  */
 314 #define LTTNG_CHANNEL_PADDING1             16
 315 struct lttng_channel {
 316         char name[LTTNG_SYMBOL_NAME_LEN];
 317         uint32_t enabled;
 318         struct lttng_channel_attr attr;
 319
 320         char padding[LTTNG_CHANNEL_PADDING1];
 321 };
 322
 323 #define LTTNG_CALIBRATE_PADDING1           16
 324 struct lttng_calibrate {
 325         enum lttng_calibrate_type type;
 326
 327         char padding[LTTNG_CALIBRATE_PADDING1];
 328 };
 329
 330 /*
 331  * Basic session information.
 332  *
 333  * This is an 'output data' meaning that it only comes *from* the session
 334  * daemon *to* the lttng client. It's basically a 'human' representation of
 335  * tracing entities (here a session).
 336  *
 337  * The structures should be initialized to zero before use.
 338  */
 339 #define LTTNG_SESSION_PADDING1             12
 340 struct lttng_session {
 341         char name[NAME_MAX];
 342         /* The path where traces are written */
 343         char path[PATH_MAX];
 344         uint32_t enabled;       /* enabled/started: 1, disabled/stopped: 0 */
 345         uint32_t snapshot_mode;
 346
 347         char padding[LTTNG_SESSION_PADDING1];
 348 };
 349
 350 /*
 351  * Handle used as a context for commands.
 352  *
 353  * The structures should be initialized to zero before use.
 354  */
 355 #define LTTNG_HANDLE_PADDING1              16
 356 struct lttng_handle {
 357         char session_name[NAME_MAX];
 358         struct lttng_domain domain;
 359
 360         char padding[LTTNG_HANDLE_PADDING1];
 361 };
 362
 363 /*
 364  * Public LTTng control API
 365  *
 366  * For functions having an lttng domain type as parameter, if a bad value is
 367  * given, NO default is applied and an error is returned.
 368  *
 369  * On success, all functions of the API return 0 or the size of the allocated
 370  * array (in bytes).
 371  *
 372  * On error, a negative value is returned being a specific lttng-tools error
 373  * code which can be humanly interpreted with lttng_strerror(err).
 374  *
 375  * Exceptions to this are noted below.
 376  */
 377
 378 /*
 379  * Create a handle used as a context for every request made to the library.
 380  *
 381  * This handle contains the session name and lttng domain on which the command
 382  * will be executed.
 383  * The returned pointer will be NULL in case of malloc() error.
 384  */
 385 extern struct lttng_handle *lttng_create_handle(const char *session_name,
 386                 struct lttng_domain *domain);
 387
 388 /*
 389  * Destroy an handle.
 390  *
 391  * It free(3) the data pointer returned by lttng_create_handle(), rendering it
 392  * unusable.
 393  */
 394 extern void lttng_destroy_handle(struct lttng_handle *handle);
 395
 396 /*
 397  * Create a tracing session using a name and an optional URL.
 398  *
 399  * If _url_ is NULL, no consumer is created for the session. The name can't be
 400  * NULL here.
 401  */
 402 extern int lttng_create_session(const char *name, const char *url);
 403
 404 /*
 405  * Create a tracing session that will exclusively be used for snapshot meaning
 406  * the session will be in no output mode and every channel enabled for that
 407  * session will be set in overwrite mode and in mmap output since splice is not
 408  * supported.
 409  *
 410  * If an url is given, it will be used to create a default snapshot output
 411  * using it as a destination. If NULL, no output will be defined and an
 412  * add-output call will be needed.
 413  *
 414  * Name can't be NULL.
 415  */
 416 extern int lttng_create_session_snapshot(const char *name,
 417                 const char *snapshot_url);
 418
 419 /*
 420  * Destroy a tracing session.
 421  *
 422  * The session will not be usable anymore, tracing will be stopped for all
 423  * registered traces, and the tracing buffers will be flushed.
 424  *
 425  * The name can't be NULL here.
 426  */
 427 extern int lttng_destroy_session(const char *name);
 428
 429 /*
 430  * List all the tracing sessions.
 431  *
 432  * Return the size (number of entries) of the "lttng_session" array. Caller
 433  * must free(3).
 434  */
 435 extern int lttng_list_sessions(struct lttng_session **sessions);
 436
 437 /*
 438  * List the registered domain(s) of a session.
 439  *
 440  * Return the size (number of entries) of the "lttng_domain" array. Caller
 441  * must free(3).
 442  */
 443 extern int lttng_list_domains(const char *session_name,
 444                 struct lttng_domain **domains);
 445
 446 /*
 447  * List the channel(s) of a session.
 448  *
 449  * Return the size (number of entries) of the "lttng_channel" array. Caller
 450  * must free(3).
 451  */
 452 extern int lttng_list_channels(struct lttng_handle *handle,
 453                 struct lttng_channel **channels);
 454
 455 /*
 456  * List the event(s) of a session channel.
 457  *
 458  * Return the size (number of entries) of the "lttng_event" array.
 459  * Caller must free(3).
 460  */
 461 extern int lttng_list_events(struct lttng_handle *handle,
 462                 const char *channel_name, struct lttng_event **events);
 463
 464 /*
 465  * List the available tracepoints of a specific lttng domain.
 466  *
 467  * Return the size (number of entries) of the "lttng_event" array.
 468  * Caller must free(3).
 469  */
 470 extern int lttng_list_tracepoints(struct lttng_handle *handle,
 471                 struct lttng_event **events);
 472
 473 /*
 474  * List the available tracepoints fields of a specific lttng domain.
 475  *
 476  * Return the size (number of entries) of the "lttng_event_field" array.
 477  * Caller must free(3).
 478  */
 479 extern int lttng_list_tracepoint_fields(struct lttng_handle *handle,
 480                 struct lttng_event_field **fields);
 481
 482 /*
 483  * Check if a session daemon is alive.
 484  *
 485  * Return 1 if alive or 0 if not. On error returns a negative value.
 486  */
 487 extern int lttng_session_daemon_alive(void);
 488
 489 /*
 490  * Set the tracing group for the *current* flow of execution.
 491  *
 492  * On success, returns 0 else a negative value on error being a lttng error
 493  * code found in lttng-error.h
 494  */
 495 extern int lttng_set_tracing_group(const char *name);
 496
 497 /*
 498  * Return a human-readable error message for an lttng-tools error code.
 499  *
 500  * Parameter MUST be a negative value or else you'll get a generic message.
 501  */
 502 extern const char *lttng_strerror(int code);
 503
 504 /*
 505  * This call registers an "outside consumer" for a session and an lttng domain.
 506  * No consumer will be spawned and all fds/commands will go through the socket
 507  * path given (socket_path).
 508  *
 509  * NOTE: At the moment, if you use the liblttng-kconsumer, you can only use the
 510  * command socket. The error socket is not supported yet for roaming consumers.
 511  */
 512 extern int lttng_register_consumer(struct lttng_handle *handle,
 513                 const char *socket_path);
 514
 515 /*
 516  * Start tracing for *all* registered traces (kernel and user-space).
 517  */
 518 extern int lttng_start_tracing(const char *session_name);
 519
 520 /*
 521  * Stop tracing for *all* registered traces (kernel and user-space).
 522  *
 523  * This call will wait for data availability for each domain of the session so
 524  * this can take an abritrary amount of time. However, when returning you have
 525  * the guarantee that the data is ready to be read and analyse. Use the
 526  * _no_wait call below to avoid this behavior.
 527  *
 528  * The session_name can't be NULL.
 529  */
 530 extern int lttng_stop_tracing(const char *session_name);
 531
 532 /*
 533  * Behave exactly like lttng_stop_tracing but does not wait for data
 534  * availability.
 535  */
 536 extern int lttng_stop_tracing_no_wait(const char *session_name);
 537
 538 /*
 539  * Add context to event(s) for a specific channel (or for all).
 540  *
 541  * If channel_name is NULL, a lookup of the event's channel is done. If both
 542  * are NULL, the context is applied to all events of all channels.
 543  *
 544  * Note that whatever event_name value is, a context can not be added to an
 545  * event, so we just ignore it for now.
 546  */
 547 extern int lttng_add_context(struct lttng_handle *handle,
 548                 struct lttng_event_context *ctx, const char *event_name,
 549                 const char *channel_name);
 550
 551 /*
 552  * Create or enable an event (or events) for a channel.
 553  *
 554  * If the event you are trying to enable does not exist, it will be created,
 555  * else it is enabled.
 556  * If channel_name is NULL, the default channel is used (channel0).
 557  *
 558  * The handle and ev params can not be NULL.
 559  */
 560 extern int lttng_enable_event(struct lttng_handle *handle,
 561                 struct lttng_event *ev, const char *channel_name);
 562
 563 /*
 564  * Create or enable an event with a specific filter.
 565  *
 566  * If the event you are trying to enable does not exist, it will be created,
 567  * else it is enabled.
 568  * If ev is NULL, all events are enabled with that filter.
 569  * If channel_name is NULL, the default channel is used (channel0) and created
 570  * if not found.
 571  * If filter_expression is NULL, an event without associated filter is
 572  * created.
 573  */
 574 extern int lttng_enable_event_with_filter(struct lttng_handle *handle,
 575                 struct lttng_event *event, const char *channel_name,
 576                 const char *filter_expression);
 577
 578 /*
 579  * Create or enable a channel.
 580  *
 581  * The chan and handle params can not be NULL.
 582  */
 583 extern int lttng_enable_channel(struct lttng_handle *handle,
 584                 struct lttng_channel *chan);
 585
 586 /*
 587  * Disable event(s) of a channel and domain.
 588  *
 589  * If name is NULL, all events are disabled.
 590  * If channel_name is NULL, the default channel is used (channel0).
 591  */
 592 extern int lttng_disable_event(struct lttng_handle *handle,
 593                 const char *name, const char *channel_name);
 594
 595 /*
 596  * Disable channel.
 597  *
 598  */
 599 extern int lttng_disable_channel(struct lttng_handle *handle,
 600                 const char *name);
 601
 602 /*
 603  * Calibrate LTTng overhead.
 604  *
 605  * The chan and handle params can not be NULL.
 606  */
 607 extern int lttng_calibrate(struct lttng_handle *handle,
 608                 struct lttng_calibrate *calibrate);
 609
 610 /*
 611  * Set the default channel attributes for a specific domain and an allocated
 612  * lttng_channel_attr pointer.
 613  *
 614  * If one or both arguments are NULL, nothing happens.
 615  */
 616 extern void lttng_channel_set_default_attr(struct lttng_domain *domain,
 617                 struct lttng_channel_attr *attr);
 618
 619 /*
 620  * Set URL for a consumer for a session and domain.
 621  *
 622  * Both data and control URL must be defined. If both URLs are the same, only
 623  * the control URL is used even for network streaming.
 624  *
 625  * Default port are 5342 and 5343 respectively for control and data which uses
 626  * the TCP protocol.
 627  */
 628 extern int lttng_set_consumer_url(struct lttng_handle *handle,
 629                 const char *control_url, const char *data_url);
 630
 631 /*
 632  * Enable the consumer for a session and domain.
 633  */
 634 extern LTTNG_DEPRECATED("This call is now obsolete.")
 635 int lttng_enable_consumer(struct lttng_handle *handle);
 636
 637 /*
 638  * Disable consumer for a session and domain.
 639  */
 640 extern LTTNG_DEPRECATED("This call is now obsolete.")
 641 int lttng_disable_consumer(struct lttng_handle *handle);
 642
 643 /*
 644  * Check session daemon health for a specific component.
 645  *
 646  * Return 0 if health is OK or 1 if BAD. A returned value of -1 indicate that
 647  * the control library was not able to connect to the session daemon health
 648  * socket.
 649  *
 650  * Any other positive value is an lttcomm error which can be translate with
 651  * lttng_strerror().
 652  *
 653  * Please see lttng-health-check(3) man page for more information.
 654  */
 655 extern int lttng_health_check(enum lttng_health_component c);
 656
 657 /*
 658  * For a given session name, this call checks if the data is ready to be read
 659  * or is still being extracted by the consumer(s) (pending) hence not ready to
 660  * be used by any readers.
 661  *
 662  * Return 0 if there is _no_ data pending in the buffers thus having a
 663  * guarantee that the data can be read safely. Else, return 1 if there is still
 664  * traced data is pending. On error, a negative value is returned and readable
 665  * by lttng_strerror().
 666  */
 667 extern int lttng_data_pending(const char *session_name);
 668
 669 #ifdef __cplusplus
 670 }
 671 #endif
 672
 673 #endif /* LTTNG_H */