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1 | lttng-ust(3) |
2 | ============ | |
3 | :object-type: library | |
4 | ||
5 | ||
6 | NAME | |
7 | ---- | |
8 | lttng-ust - LTTng user space tracing | |
9 | ||
10 | ||
11 | SYNOPSIS | |
12 | -------- | |
13 | [verse] | |
14 | *#include <lttng/tracepoint.h>* | |
15 | ||
16 | [verse] | |
17 | #define *TRACEPOINT_ENUM*('prov_name', 'enum_name', 'mappings') | |
18 | #define *TRACEPOINT_EVENT*('prov_name', 't_name', 'args', 'fields') | |
19 | #define *TRACEPOINT_EVENT_CLASS*('prov_name', 'class_name', | |
20 | 'args', 'fields') | |
21 | #define *TRACEPOINT_EVENT_INSTANCE*('prov_name', 'class_name', | |
22 | 't_name', 'args') | |
23 | #define *TRACEPOINT_LOGLEVEL*('prov_name', 't_name', 'level') | |
24 | #define *ctf_array*('int_type', 'field_name', 'expr', 'count') | |
25 | #define *ctf_array_nowrite*('int_type', 'field_name', 'expr', 'count') | |
26 | #define *ctf_array_text*(char, 'field_name', 'expr', 'count') | |
27 | #define *ctf_array_text_nowrite*(char, 'field_name', 'expr', 'count') | |
28 | #define *ctf_enum*('prov_name', 'enum_name', 'int_type', 'field_name', 'expr') | |
29 | #define *ctf_enum_nowrite*('prov_name', 'enum_name', 'int_type', | |
30 | 'field_name', 'expr') | |
31 | #define *ctf_enum_value*('label', 'value') | |
32 | #define *ctf_enum_range*('label', 'start', 'end') | |
33 | #define *ctf_float*('float_type', 'field_name', 'expr') | |
34 | #define *ctf_float_nowrite*('float_type', 'field_name', 'expr') | |
35 | #define *ctf_integer*('int_type', 'field_name', 'expr') | |
36 | #define *ctf_integer_hex*('int_type', 'field_name', 'expr') | |
37 | #define *ctf_integer_network*('int_type', 'field_name', 'expr') | |
38 | #define *ctf_integer_network_hex*('int_type', 'field_name', 'expr') | |
39 | #define *ctf_integer_nowrite*('int_type', 'field_name', 'expr') | |
40 | #define *ctf_sequence*('int_type', 'field_name', 'expr', 'len_type', 'len_expr') | |
41 | #define *ctf_sequence_nowrite*('int_type', 'field_name', 'expr', | |
42 | 'len_type', 'len_expr') | |
43 | #define *ctf_sequence_text*(char, 'field_name', 'expr', 'len_type', 'len_expr') | |
44 | #define *ctf_sequence_text_nowrite*(char, 'field_name', 'expr', | |
45 | 'len_type', 'len_expr') | |
46 | #define *ctf_string*('field_name', 'expr') | |
47 | #define *ctf_string_nowrite*('field_name', 'expr') | |
48 | #define *do_tracepoint*('prov_name', 't_name', ...) | |
49 | #define *tracepoint*('prov_name', 't_name', ...) | |
50 | #define *tracepoint_enabled*('prov_name', 't_name') | |
51 | ||
52 | Link with `-llttng-ust -ldl`, following this man page. | |
53 | ||
54 | ||
55 | DESCRIPTION | |
56 | ----------- | |
57 | The http://lttng.org/[_Linux Trace Toolkit: next generation_] is an open | |
58 | source software package used for correlated tracing of the Linux kernel, | |
59 | user applications, and user libraries. | |
60 | ||
61 | LTTng-UST is the user space tracing component of the LTTng project. It | |
62 | is a port to user space of the low-overhead tracing capabilities of the | |
63 | LTTng Linux kernel tracer. The `liblttng-ust` library is used to trace | |
64 | user applications and libraries. | |
65 | ||
66 | NOTE: This man page is about the `liblttng-ust` library. The LTTng-UST | |
67 | project also provides Java and Python packages to trace applications | |
68 | written in those languages. How to instrument and trace Java and Python | |
69 | applications is documented in | |
70 | http://lttng.org/docs/[the online LTTng documentation]. | |
71 | ||
72 | There are three ways to use `liblttng-ust`: | |
73 | ||
74 | * Using the man:tracef(3) API, which is similar to man:printf(3). | |
75 | * Using the man:tracelog(3) API, which is man:tracef(3) with | |
76 | a log level parameter. | |
77 | * Defining your own tracepoints. See the | |
78 | <<creating-tp,Creating a tracepoint provider>> section below. | |
79 | ||
80 | ||
81 | [[creating-tp]] | |
82 | Creating a tracepoint provider | |
83 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
84 | Creating a tracepoint provider is the first step of using | |
85 | `liblttng-ust`. The next steps are: | |
86 | ||
87 | * <<tracepoint,Instrumenting your application with `tracepoint()` calls>> | |
88 | * Building your application with LTTng-UST support, either | |
89 | <<build-static,statically>> or <<build-dynamic,dynamically>>. | |
90 | ||
91 | A *tracepoint provider* is a compiled object containing the event | |
92 | probes corresponding to your custom tracepoint definitions. A tracepoint | |
93 | provider contains the code to get the size of an event and to serialize | |
94 | it, amongst other things. | |
95 | ||
96 | To create a tracepoint provider, start with the following | |
97 | _tracepoint provider header_ template: | |
98 | ||
99 | ------------------------------------------------------------------------ | |
100 | #undef TRACEPOINT_PROVIDER | |
101 | #define TRACEPOINT_PROVIDER my_provider | |
102 | ||
103 | #undef TRACEPOINT_INCLUDE | |
104 | #define TRACEPOINT_INCLUDE "./tp.h" | |
105 | ||
106 | #if !defined(_TP_H) || defined(TRACEPOINT_HEADER_MULTI_READ) | |
107 | #define _TP_H | |
108 | ||
109 | #include <lttng/tracepoint.h> | |
110 | ||
111 | /* | |
112 | * TRACEPOINT_EVENT(), TRACEPOINT_EVENT_CLASS(), | |
113 | * TRACEPOINT_EVENT_INSTANCE(), TRACEPOINT_LOGLEVEL(), | |
114 | * and `TRACEPOINT_ENUM()` are used here. | |
115 | */ | |
116 | ||
117 | #endif /* _TP_H */ | |
118 | ||
119 | #include <lttng/tracepoint-event.h> | |
120 | ------------------------------------------------------------------------ | |
121 | ||
122 | In this template, the tracepoint provider is named `my_provider` | |
123 | (`TRACEPOINT_PROVIDER` definition). The file needs to bear the | |
124 | name of the `TRACEPOINT_INCLUDE` definition (`tp.h` in this case). | |
125 | Between `#include <lttng/tracepoint.h>` and `#endif` go | |
126 | the invocations of the <<tracepoint-event,`TRACEPOINT_EVENT()`>>, | |
127 | <<tracepoint-event-class,`TRACEPOINT_EVENT_CLASS()`>>, | |
128 | <<tracepoint-event-class,`TRACEPOINT_EVENT_INSTANCE()`>>, | |
129 | <<tracepoint-loglevel,`TRACEPOINT_LOGLEVEL()`>>, and | |
130 | <<tracepoint-enum,`TRACEPOINT_ENUM()`>> macros. | |
131 | ||
132 | NOTE: You can avoid writing the prologue and epilogue boilerplate in the | |
133 | template file above by using the man:lttng-gen-tp(1) tool shipped with | |
134 | LTTng-UST. | |
135 | ||
136 | The tracepoint provider header file needs to be included in a source | |
137 | file which looks like this: | |
138 | ||
139 | ------------------------------------------------------------------------ | |
140 | #define TRACEPOINT_CREATE_PROBES | |
141 | ||
142 | #include "tp.h" | |
143 | ------------------------------------------------------------------------ | |
144 | ||
145 | Together, those two files (let's call them `tp.h` and `tp.c`) form the | |
146 | tracepoint provider sources, ready to be compiled. | |
147 | ||
148 | You can create multiple tracepoint providers to be used in a single | |
149 | application, but each one must have its own header file. | |
150 | ||
151 | The <<tracepoint-event,`TRACEPOINT_EVENT()` usage>> section below | |
152 | shows how to use the `TRACEPOINT_EVENT()` macro to define the actual | |
153 | tracepoints in the tracepoint provider header file. | |
154 | ||
155 | See the <<example,EXAMPLE>> section below for a complete example. | |
156 | ||
157 | ||
158 | [[tracepoint-event]] | |
159 | `TRACEPOINT_EVENT()` usage | |
160 | ~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
161 | The `TRACEPOINT_EVENT()` macro is used in a template provider | |
162 | header file (see the <<creating-tp,Creating a tracepoint provider>> | |
163 | section above) to define LTTng-UST tracepoints. | |
164 | ||
165 | The `TRACEPOINT_EVENT()` usage template is as follows: | |
166 | ||
167 | ------------------------------------------------------------------------ | |
168 | TRACEPOINT_EVENT( | |
169 | /* Tracepoint provider name */ | |
170 | my_provider, | |
171 | ||
172 | /* Tracepoint/event name */ | |
173 | my_tracepoint, | |
174 | ||
175 | /* List of tracepoint arguments (input) */ | |
176 | TP_ARGS( | |
177 | ... | |
178 | ), | |
179 | ||
180 | /* List of fields of eventual event (output) */ | |
181 | TP_FIELDS( | |
182 | ... | |
183 | ) | |
184 | ) | |
185 | ------------------------------------------------------------------------ | |
186 | ||
187 | The `TP_ARGS()` macro contains the input arguments of the tracepoint. | |
188 | Those arguments can be used in the argument expressions of the output | |
189 | fields defined in `TP_FIELDS()`. | |
190 | ||
191 | The format of the `TP_ARGS()` parameters is: C type, then argument name; | |
192 | repeat as needed, up to ten times. For example: | |
193 | ||
194 | ------------------------------------------------------------------------ | |
195 | TP_ARGS( | |
196 | int, my_int, | |
197 | const char *, my_string, | |
198 | FILE *, my_file, | |
199 | double, my_float, | |
200 | struct my_data *, my_data | |
201 | ) | |
202 | ------------------------------------------------------------------------ | |
203 | ||
204 | The `TP_FIELDS()` macro contains the output fields of the tracepoint, | |
205 | that is, the actual data that can be recorded in the payload of an | |
206 | event emitted by this tracepoint. | |
207 | ||
208 | The `TP_FIELDS()` macro contains a list of `ctf_*()` macros | |
209 | :not: separated by commas. The available macros are documented in the | |
210 | <<ctf-macros,Available `ctf_*()` field type macros>> section below. | |
211 | ||
212 | ||
213 | [[ctf-macros]] | |
214 | Available `ctf_*()` field type macros | |
215 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
216 | This section documents the available `ctf_*()` macros that can be | |
217 | inserted in the `TP_FIELDS()` macro of the | |
218 | <<tracepoint-event,`TRACEPOINT_EVENT()` macro>>. | |
219 | ||
220 | Standard integer, displayed in base 10: | |
221 | ||
222 | [verse] | |
223 | *ctf_integer*('int_type', 'field_name', 'expr') | |
224 | *ctf_integer_nowrite*('int_type', 'field_name', 'expr') | |
225 | ||
226 | Standard integer, displayed in base 16: | |
227 | ||
228 | [verse] | |
229 | *ctf_integer_hex*('int_type', 'field_name', 'expr') | |
230 | ||
231 | Integer in network byte order (big endian), displayed in base 10: | |
232 | ||
233 | [verse] | |
234 | *ctf_integer_network*('int_type', 'field_name', 'expr') | |
235 | ||
236 | Integer in network byte order, displayed in base 16: | |
237 | ||
238 | [verse] | |
239 | *ctf_integer_network_hex*('int_type', 'field_name', 'expr') | |
240 | ||
241 | Floating point number: | |
242 | ||
243 | [verse] | |
244 | *ctf_float*('float_type', 'field_name', 'expr') | |
245 | *ctf_float_nowrite*('float_type', 'field_name', 'expr') | |
246 | ||
247 | Null-terminated string: | |
248 | ||
249 | [verse] | |
250 | *ctf_string*('field_name', 'expr') | |
251 | *ctf_string_nowrite*('field_name', 'expr') | |
252 | ||
253 | Statically-sized array of integers: | |
254 | ||
255 | [verse] | |
256 | *ctf_array*('int_type', 'field_name', 'expr', 'count') | |
257 | *ctf_array_nowrite*('int_type', 'field_name', 'expr', 'count') | |
258 | ||
259 | Statically-sized array, printed as text; no need to be null-terminated: | |
260 | ||
261 | [verse] | |
262 | *ctf_array_text*(char, 'field_name', 'expr', 'count') | |
263 | *ctf_array_text_nowrite*(char, 'field_name', 'expr', 'count') | |
264 | ||
265 | Dynamically-sized array of integers: | |
266 | ||
267 | [verse] | |
268 | *ctf_sequence*('int_type', 'field_name', 'expr', 'len_type', 'len_expr') | |
269 | *ctf_sequence_nowrite*('int_type', 'field_name', 'expr', 'len_type', 'len_expr') | |
270 | ||
271 | Dynamically-sized array, displayed as text; no need to be null-terminated: | |
272 | ||
273 | [verse] | |
274 | *ctf_sequence_text*(char, 'field_name', 'expr', 'len_type', 'len_expr') | |
275 | *ctf_sequence_text_nowrite*(char, 'field_name', 'expr', 'len_type', 'len_expr') | |
276 | ||
277 | Enumeration. The enumeration field must be defined before using this | |
278 | macro with the `TRACEPOINT_ENUM()` macro. See the | |
279 | <<tracepoint-enum,`TRACEPOINT_ENUM()` usage>> section for more | |
280 | information. | |
281 | ||
282 | [verse] | |
283 | *ctf_enum*('prov_name', 'enum_name', 'int_type', 'field_name', 'expr') | |
284 | *ctf_enum_nowrite*('prov_name', 'enum_name', 'int_type', 'field_name', 'expr') | |
285 | ||
286 | The parameters are: | |
287 | ||
288 | 'int_type':: | |
289 | Integer C type. The size of this type determines the size of the | |
290 | integer/enumeration field. | |
291 | ||
292 | 'float_type':: | |
293 | Float C type (`float` or `double`). The size of this type determines | |
294 | the size of the floating point number field. | |
295 | ||
296 | 'field_name':: | |
297 | Event field name (C identifier syntax, :not: a literal string). | |
298 | ||
299 | 'expr':: | |
300 | C expression resulting in the field's value. This expression can | |
301 | use one or more arguments passed to the tracepoint. The arguments | |
302 | of a given tracepoint are defined in the `TP_ARGS()` macro (see | |
303 | the <<creating-tp,Creating a tracepoint provider>> section above). | |
304 | ||
305 | 'count':: | |
306 | Number of elements in array/sequence. This must be known at | |
307 | compile time. | |
308 | ||
309 | 'len_type':: | |
310 | Unsigned integer C type of sequence's length. | |
311 | ||
312 | 'len_expr':: | |
313 | C expression resulting in the sequence's length. This expression | |
314 | can use one or more arguments passed to the tracepoint. | |
315 | ||
316 | 'prov_name':: | |
317 | Tracepoint provider name. This must be the same as the tracepoint | |
318 | provider name used in a previous field definition. | |
319 | ||
320 | 'enum_name':: | |
321 | Name of an enumeration field previously defined with the | |
322 | `TRACEPOINT_ENUM()` macro. See the | |
323 | <<tracepoint-enum,`TRACEPOINT_ENUM()` usage>> section for more | |
324 | information. | |
325 | ||
326 | The `_nowrite` versions omit themselves from the recorded trace, but are | |
327 | otherwise identical. Their primary purpose is to make some of the | |
328 | event context available to the event filters without having to commit | |
329 | the data to sub-buffers. See man:lttng-enable-event(1) to learn more | |
330 | about dynamic event filtering. | |
331 | ||
332 | See the <<example,EXAMPLE>> section below for a complete example. | |
333 | ||
334 | ||
335 | [[tracepoint-enum]] | |
336 | `TRACEPOINT_ENUM()` usage | |
337 | ~~~~~~~~~~~~~~~~~~~~~~~~~ | |
338 | An enumeration field is a list of mappings between an integers, or a | |
339 | range of integers, and strings (sometimes called _labels_ or | |
340 | _enumerators_). Enumeration fields can be used to have a more compact | |
341 | trace when the possible values for a field are limited. | |
342 | ||
343 | An enumeration field is defined with the `TRACEPOINT_ENUM()` macro: | |
344 | ||
345 | ------------------------------------------------------------------------ | |
346 | TRACEPOINT_ENUM( | |
347 | /* Tracepoint provider name */ | |
348 | my_provider, | |
349 | ||
350 | /* Enumeration name (unique in the whole tracepoint provider) */ | |
351 | my_enum, | |
352 | ||
353 | /* Enumeration mappings */ | |
354 | TP_ENUM_VALUES( | |
355 | ... | |
356 | ) | |
357 | ) | |
358 | ------------------------------------------------------------------------ | |
359 | ||
360 | `TP_ENUM_VALUES()` contains a list of enumeration mappings, :not: | |
361 | separated by commas. Two macros can be used in the `TP_ENUM_VALUES()`: | |
362 | `ctf_enum_value()` and `ctf_enum_range()`. | |
363 | ||
364 | `ctf_enum_value()` is a single value mapping: | |
365 | ||
366 | [verse] | |
367 | *ctf_enum_value*('label', 'value') | |
368 | ||
369 | This macro maps the given 'label' string to the value 'value'. | |
370 | ||
371 | `ctf_enum_range()` is a range mapping: | |
372 | ||
373 | [verse] | |
374 | *ctf_enum_range*('label', 'start', 'end') | |
375 | ||
376 | This macro maps the given 'label' string to the range of integers from | |
377 | 'start' to 'end', inclusively. Range mappings may overlap, but the | |
378 | behaviour is implementation-defined: each trace reader handles | |
379 | overlapping ranges as it wishes. | |
380 | ||
381 | See the <<example,EXAMPLE>> section below for a complete example. | |
382 | ||
383 | ||
384 | [[tracepoint-event-class]] | |
385 | `TRACEPOINT_EVENT_CLASS()` usage | |
386 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
387 | A *tracepoint class* is a class of tracepoints sharing the | |
388 | same field types and names. A tracepoint instance is one instance of | |
389 | such a declared tracepoint class, with its own event name. | |
390 | ||
391 | LTTng-UST creates one event serialization function per tracepoint | |
392 | class. Using `TRACEPOINT_EVENT()` creates one tracepoint class per | |
393 | tracepoint definition, whereas using `TRACEPOINT_EVENT_CLASS()` and | |
394 | `TRACEPOINT_EVENT_INSTANCE()` creates one tracepoint class, and one or | |
395 | more tracepoint instances of this class. In other words, many | |
396 | tracepoints can reuse the same serialization code. Reusing the same | |
397 | code, when possible, can reduce cache pollution, thus improve | |
398 | performance. | |
399 | ||
400 | The `TRACEPOINT_EVENT_CLASS()` macro accepts the same parameters as | |
401 | the `TRACEPOINT_EVENT()` macro, except that instead of an event name, | |
402 | its second parameter is the _tracepoint class name_: | |
403 | ||
404 | ------------------------------------------------------------------------ | |
405 | TRACEPOINT_EVENT_CLASS( | |
406 | /* Tracepoint provider name */ | |
407 | my_provider, | |
408 | ||
409 | /* Tracepoint class name */ | |
410 | my_tracepoint_class, | |
411 | ||
412 | /* List of tracepoint arguments (input) */ | |
413 | TP_ARGS( | |
414 | ... | |
415 | ), | |
416 | ||
417 | /* List of fields of eventual event (output) */ | |
418 | TP_FIELDS( | |
419 | ... | |
420 | ) | |
421 | ) | |
422 | ------------------------------------------------------------------------ | |
423 | ||
424 | Once the tracepoint class is defined, you can create as many tracepoint | |
425 | instances as needed: | |
426 | ||
427 | ------------------------------------------------------------------------- | |
428 | TRACEPOINT_EVENT_INSTANCE( | |
429 | /* Tracepoint provider name */ | |
430 | my_provider, | |
431 | ||
432 | /* Tracepoint class name */ | |
433 | my_tracepoint_class, | |
434 | ||
435 | /* Tracepoint/event name */ | |
436 | my_tracepoint, | |
437 | ||
438 | /* List of tracepoint arguments (input) */ | |
439 | TP_ARGS( | |
440 | ... | |
441 | ) | |
442 | ) | |
443 | ------------------------------------------------------------------------ | |
444 | ||
445 | As you can see, the `TRACEPOINT_EVENT_INSTANCE()` does not contain | |
446 | the `TP_FIELDS()` macro, because they are defined at the | |
447 | `TRACEPOINT_EVENT_CLASS()` level. | |
448 | ||
449 | See the <<example,EXAMPLE>> section below for a complete example. | |
450 | ||
451 | ||
452 | [[tracepoint-loglevel]] | |
453 | `TRACEPOINT_LOGLEVEL()` usage | |
454 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
455 | Optionally, a *log level* can be assigned to a defined tracepoint. | |
456 | Assigning different levels of severity to tracepoints can be useful: | |
457 | when controlling tracing sessions, you can choose to only enable | |
458 | events falling into a specific log level range using the | |
459 | nloption:--loglevel and nloption:--loglevel-only options of the | |
460 | man:lttng-enable-event(1) command. | |
461 | ||
462 | Log levels are assigned to tracepoints that are already defined using | |
463 | the `TRACEPOINT_LOGLEVEL()` macro. The latter must be used after having | |
464 | used `TRACEPOINT_EVENT()` or `TRACEPOINT_EVENT_INSTANCE()` for a given | |
465 | tracepoint. The `TRACEPOINT_LOGLEVEL()` macro is used as follows: | |
466 | ||
467 | ------------------------------------------------------------------------ | |
468 | TRACEPOINT_LOGLEVEL( | |
469 | /* Tracepoint provider name */ | |
470 | my_provider, | |
471 | ||
472 | /* Tracepoint/event name */ | |
473 | my_tracepoint, | |
474 | ||
475 | /* Log level */ | |
476 | TRACE_INFO | |
477 | ) | |
478 | ------------------------------------------------------------------------ | |
479 | ||
480 | The available log level definitions are: | |
481 | ||
482 | include::log-levels.txt[] | |
483 | ||
484 | See the <<example,EXAMPLE>> section below for a complete example. | |
485 | ||
486 | ||
487 | [[tracepoint]] | |
488 | Instrumenting your application | |
489 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
490 | Once the tracepoint provider is created (see the | |
491 | <<creating-tp,Creating a tracepoint provider>> section above), you can | |
492 | instrument your application with the defined tracepoints thanks to the | |
493 | `tracepoint()` macro: | |
494 | ||
495 | [verse] | |
496 | #define *tracepoint*('prov_name', 't_name', ...) | |
497 | ||
498 | With: | |
499 | ||
500 | 'prov_name':: | |
501 | Tracepoint provider name. | |
502 | ||
503 | 't_name':: | |
504 | Tracepoint/event name. | |
505 | ||
506 | `...`:: | |
507 | Tracepoint arguments, if any. | |
508 | ||
509 | Make sure to include the tracepoint provider header file anywhere you | |
510 | use `tracepoint()` for this provider. | |
511 | ||
512 | NOTE: Even though LTTng-UST supports `tracepoint()` call site duplicates | |
513 | having the same provider and tracepoint names, it is recommended to use | |
514 | a provider/tracepoint name pair only once within the application source | |
515 | code to help map events back to their call sites when analyzing the | |
516 | trace. | |
517 | ||
518 | Sometimes, arguments to the tracepoint are expensive to compute (take | |
519 | call stack, for example). To avoid the computation when the tracepoint | |
520 | is disabled, you can use the `tracepoint_enabled()` and | |
521 | `do_tracepoint()` macros: | |
522 | ||
523 | [verse] | |
524 | #define *tracepoint_enabled*('prov_name', 't_name') | |
525 | #define *do_tracepoint*('prov_name', 't_name', ...) | |
526 | ||
527 | `tracepoint_enabled()` returns a non-zero value if the tracepoint | |
528 | named 't_name' from the provider named 'prov_name' is enabled at | |
529 | run time. | |
530 | ||
531 | `do_tracepoint()` is like `tracepoint()`, except that it doesn't check | |
532 | if the tracepoint is enabled. Using `tracepoint()` with | |
533 | `tracepoint_enabled()` is dangerous since `tracepoint()` also contains | |
534 | the `tracepoint_enabled()` check, thus a race condition is possible | |
535 | in this situation: | |
536 | ||
537 | ------------------------------------------------------------------------ | |
538 | if (tracepoint_enabled(my_provider, my_tracepoint)) { | |
539 | stuff = prepare_stuff(); | |
540 | } | |
541 | ||
542 | tracepoint(my_provider, my_tracepoint, stuff); | |
543 | ------------------------------------------------------------------------ | |
544 | ||
545 | If the tracepoint is enabled after the condition, then `stuff` is not | |
546 | prepared: the emitted event will either contain wrong data, or the | |
547 | whole application could crash (segmentation fault, for example). | |
548 | ||
549 | NOTE: Neither `tracepoint_enabled()` nor `do_tracepoint()` have | |
550 | a `STAP_PROBEV()` call, so if you need it, you should emit this call | |
551 | yourself. | |
552 | ||
553 | ||
554 | [[build-static]] | |
555 | Statically linking the tracepoint provider | |
556 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
557 | With the static linking method, compiled tracepoint providers are copied | |
558 | into the target application. | |
559 | ||
560 | Define `TRACEPOINT_DEFINE` definition below the | |
561 | `TRACEPOINT_CREATE_PROBES` definition in the tracepoint provider | |
562 | source: | |
563 | ||
564 | ------------------------------------------------------------------------ | |
565 | #define TRACEPOINT_CREATE_PROBES | |
566 | #define TRACEPOINT_DEFINE | |
567 | ||
568 | #include "tp.h" | |
569 | ------------------------------------------------------------------------ | |
570 | ||
571 | Create the tracepoint provider object file: | |
572 | ||
573 | [role="term"] | |
574 | -------------- | |
575 | cc -c -I. tp.c | |
576 | -------------- | |
577 | ||
578 | NOTE: Although an application instrumented with LTTng-UST tracepoints | |
579 | can be compiled with a C++ compiler, tracepoint probes should be | |
580 | compiled with a C compiler. | |
581 | ||
582 | At this point, you _can_ archive this tracepoint provider object file, | |
583 | possibly with other object files of your application or with other | |
584 | tracepoint provider object files, as a static library: | |
585 | ||
586 | [role="term"] | |
587 | --------------- | |
588 | ar rc tp.a tp.o | |
589 | --------------- | |
590 | ||
591 | Using a static library does have the advantage of centralising the | |
592 | tracepoint providers objects so they can be shared between multiple | |
593 | applications. This way, when the tracepoint provider is modified, the | |
594 | source code changes don't have to be patched into each application's | |
595 | source code tree. The applications need to be relinked after each | |
596 | change, but need not to be otherwise recompiled (unless the tracepoint | |
597 | provider's API changes). | |
598 | ||
599 | Then, link your application with this object file (or with the static | |
600 | library containing it) and with `liblttng-ust` and `libdl` | |
601 | (`libc` on a BSD system): | |
602 | ||
603 | [role="term"] | |
604 | ------------------------------------- | |
605 | cc -o app tp.o app.o -llttng-ust -ldl | |
606 | ------------------------------------- | |
607 | ||
608 | ||
609 | [[build-dynamic]] | |
610 | Dynamically loading the tracepoint provider | |
611 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
612 | The second approach to package the tracepoint provider is to use the | |
613 | dynamic loader: the library and its member functions are explicitly | |
614 | sought, loaded at run time. | |
615 | ||
616 | In this scenario, the tracepoint provider is compiled as a shared | |
617 | object. | |
618 | ||
619 | The process to create the tracepoint provider shared object is pretty | |
620 | much the same as the <<build-static,static linking method>>, except | |
621 | that: | |
622 | ||
623 | * Since the tracepoint provider is not part of the application, | |
624 | `TRACEPOINT_DEFINE` must be defined, for each tracepoint | |
625 | provider, in exactly one source file of the | |
626 | _application_ | |
627 | * `TRACEPOINT_PROBE_DYNAMIC_LINKAGE` must be defined next | |
628 | to `TRACEPOINT_DEFINE` | |
629 | ||
630 | Regarding `TRACEPOINT_DEFINE` and `TRACEPOINT_PROBE_DYNAMIC_LINKAGE`, | |
631 | the recommended practice is to use a separate C source file in your | |
632 | application to define them, then include the tracepoint provider header | |
633 | files afterwards. For example, as `tp-define.c`: | |
634 | ||
635 | ------------------------------------------------------------------------ | |
636 | #define TRACEPOINT_DEFINE | |
637 | #define TRACEPOINT_PROBE_DYNAMIC_LINKAGE | |
638 | ||
639 | #include "tp.h" | |
640 | ------------------------------------------------------------------------ | |
641 | ||
642 | The tracepoint provider object file used to create the shared library is | |
643 | built like it is using the static linking method, but with the | |
644 | nloption:-fpic option: | |
645 | ||
646 | [role="term"] | |
647 | -------------------- | |
648 | cc -c -fpic -I. tp.c | |
649 | -------------------- | |
650 | ||
651 | It is then linked as a shared library like this: | |
652 | ||
653 | [role="term"] | |
654 | ------------------------------------------------------- | |
655 | cc -shared -Wl,--no-as-needed -o tp.so tp.o -llttng-ust | |
656 | ------------------------------------------------------- | |
657 | ||
658 | This tracepoint provider shared object isn't linked with the user | |
659 | application: it must be loaded manually. This is why the application is | |
660 | built with no mention of this tracepoint provider, but still needs | |
661 | libdl: | |
662 | ||
663 | [role="term"] | |
664 | -------------------------------- | |
665 | cc -o app app.o tp-define.o -ldl | |
666 | -------------------------------- | |
667 | ||
668 | There are two ways to dynamically load the tracepoint provider shared | |
669 | object: | |
670 | ||
671 | * Load it manually from the application using man:dlopen(3) | |
672 | * Make the dynamic loader load it with the `LD_PRELOAD` | |
673 | environment variable (see man:ld.so(8)) | |
674 | ||
675 | If the application does not dynamically load the tracepoint provider | |
676 | shared object using one of the methods above, tracing is disabled for | |
677 | this application, and the events are not listed in the output of | |
678 | man:lttng-list(1). | |
679 | ||
680 | Note that it is not safe to use man:dlclose(3) on a tracepoint provider | |
681 | shared object that is being actively used for tracing, due to a lack of | |
682 | reference counting from LTTng-UST to the shared object. | |
683 | ||
684 | For example, statically linking a tracepoint provider to a shared object | |
685 | which is to be dynamically loaded by an application (a plugin, for | |
686 | example) is not safe: the shared object, which contains the tracepoint | |
687 | provider, could be dynamically closed (man:dlclose(3)) at any time by | |
688 | the application. | |
689 | ||
690 | To instrument a shared object, either: | |
691 | ||
692 | * Statically link the tracepoint provider to the application, or | |
693 | * Build the tracepoint provider as a shared object (following the | |
694 | procedure shown in this section), and preload it when tracing is | |
695 | needed using the `LD_PRELOAD` environment variable. | |
696 | ||
697 | ||
698 | Using LTTng-UST with daemons | |
699 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
700 | Some extra care is needed when using `liblttng-ust` with daemon | |
701 | applications that call man:fork(2), man:clone(2), or BSD's man:rfork(2) | |
702 | without a following man:exec(3) family system call. The library | |
703 | `liblttng-ust-fork.so` needs to be preloaded before starting the | |
704 | application with the `LD_PRELOAD` environment variable (see | |
705 | man:ld.so(8)). | |
706 | ||
707 | ||
708 | Context information | |
709 | ~~~~~~~~~~~~~~~~~~~ | |
710 | Context information can be prepended by the LTTng-UST tracer before | |
711 | each event, or before specific events. | |
712 | ||
713 | Context fields can be added to specific channels using | |
714 | man:lttng-add-context(1). | |
715 | ||
716 | The following context fields are supported by LTTng-UST: | |
717 | ||
718 | `cpu_id`:: | |
719 | CPU ID. | |
720 | + | |
721 | NOTE: This context field is always enabled, and it cannot be added | |
722 | with man:lttng-add-context(1). Its main purpose is to be used for | |
723 | dynamic event filtering. See man:lttng-enable-event(1) for more | |
724 | information about event filtering. | |
725 | ||
726 | `ip`:: | |
727 | Instruction pointer: enables recording the exact address from which | |
728 | an event was emitted. This context field can be used to | |
729 | reverse-lookup the source location that caused the event | |
730 | to be emitted. | |
731 | ||
732 | +perf:thread:COUNTER+:: | |
733 | perf counter named 'COUNTER'. Use `lttng add-context --list` to | |
734 | list the available perf counters. | |
735 | + | |
736 | Only available on IA-32 and x86-64 architectures. | |
737 | ||
738 | `pthread_id`:: | |
739 | POSIX thread identifier. Can be used on architectures where | |
740 | `pthread_t` maps nicely to an `unsigned long` type. | |
741 | ||
742 | `procname`:: | |
743 | Thread name, as set by man:exec(3) or man:prctl(2). It is | |
744 | recommended that programs set their thread name with man:prctl(2) | |
745 | before hitting the first tracepoint for that thread. | |
746 | ||
747 | `vpid`:: | |
748 | Virtual process ID: process ID as seen from the point of view of | |
749 | the process namespace. | |
750 | ||
751 | `vtid`:: | |
752 | Virtual thread ID: thread ID as seen from the point of view of | |
753 | the process namespace. | |
754 | ||
755 | ||
174434f5 | 756 | [[state-dump]] |
4ddbd0b7 PP |
757 | LTTng-UST state dump |
758 | ~~~~~~~~~~~~~~~~~~~~ | |
759 | If an application that uses `liblttng-ust` becomes part of a tracing | |
760 | session, information about its currently loaded shared objects, their | |
0c3c03e0 | 761 | build IDs, and their debug link information are emitted as events |
4ddbd0b7 PP |
762 | by the tracer. |
763 | ||
764 | The following LTTng-UST state dump events exist and must be enabled | |
765 | to record application state dumps. | |
766 | ||
767 | `lttng_ust_statedump:start`:: | |
768 | Emitted when the state dump begins. | |
769 | + | |
770 | This event has no fields. | |
771 | ||
772 | `lttng_ust_statedump:end`:: | |
773 | Emitted when the state dump ends. Once this event is emitted, it | |
774 | is guaranteed that, for a given process, the state dump is | |
775 | complete. | |
776 | + | |
777 | This event has no fields. | |
778 | ||
6488ae4c | 779 | `lttng_ust_statedump:bin_info`:: |
f5eb039d AB |
780 | Emitted when information about a currently loaded executable or |
781 | shared object is found. | |
4ddbd0b7 PP |
782 | + |
783 | Fields: | |
784 | + | |
785 | [options="header"] | |
f5eb039d | 786 | |================================================================== |
4ddbd0b7 | 787 | | Field name | Description |
f5eb039d AB |
788 | | `baddr` | Base address of loaded executable |
789 | | `memsz` | Size of loaded executable in memory | |
6488ae4c | 790 | | `path` | Path to loaded executable file |
f5eb039d AB |
791 | | `is_pic` | Whether the executable is |
792 | position-independent code | |
793 | |================================================================== | |
4ddbd0b7 PP |
794 | |
795 | `lttng_ust_statedump:build_id`:: | |
796 | Emitted when a build ID is found in a currently loaded shared | |
797 | library. See | |
798 | https://sourceware.org/gdb/onlinedocs/gdb/Separate-Debug-Files.html[Debugging Information in Separate Files] | |
799 | for more information about build IDs. | |
800 | + | |
801 | Fields: | |
802 | + | |
803 | [options="header"] | |
804 | |============================================================== | |
805 | | Field name | Description | |
806 | | `baddr` | Base address of loaded library | |
807 | | `build_id` | Build ID | |
808 | |============================================================== | |
809 | ||
810 | `lttng_ust_statedump:debug_link`:: | |
811 | Emitted when debug link information is found in a currently loaded | |
812 | shared library. See | |
813 | https://sourceware.org/gdb/onlinedocs/gdb/Separate-Debug-Files.html[Debugging Information in Separate Files] | |
814 | for more information about debug links. | |
815 | + | |
816 | Fields: | |
817 | + | |
818 | [options="header"] | |
819 | |============================================================== | |
820 | | Field name | Description | |
821 | | `baddr` | Base address of loaded library | |
822 | | `crc` | Debug link file's CRC | |
823 | | `filename` | Debug link file name | |
824 | |============================================================== | |
825 | ||
826 | ||
827 | [[example]] | |
828 | EXAMPLE | |
829 | ------- | |
830 | NOTE: A few examples are available in the | |
831 | https://github.com/lttng/lttng-ust/tree/master/doc/examples[`doc/examples`] | |
832 | directory of LTTng-UST's source tree. | |
833 | ||
834 | This example shows all the features documented in the previous | |
835 | sections. The <<build-static,static linking>> method is chosen here | |
836 | to link the application with the tracepoint provider. | |
837 | ||
885adac8 PP |
838 | You can compile the source files and link them together statically |
839 | like this: | |
840 | ||
841 | [role="term"] | |
842 | ------------------------------------- | |
843 | cc -c -I. tp.c | |
844 | cc -c app.c | |
845 | cc -o app tp.o app.o -llttng-ust -ldl | |
846 | ------------------------------------- | |
847 | ||
00665d8e PP |
848 | Using the man:lttng(1) tool, create an LTTng tracing session, enable |
849 | all the events of this tracepoint provider, and start tracing: | |
850 | ||
851 | [role="term"] | |
852 | ---------------------------------------------- | |
853 | lttng create my-session | |
854 | lttng enable-event --userspace 'my_provider:*' | |
855 | lttng start | |
856 | ---------------------------------------------- | |
857 | ||
858 | You may also enable specific events: | |
859 | ||
860 | [role="term"] | |
861 | ---------------------------------------------------------- | |
862 | lttng enable-event --userspace my_provider:big_event | |
863 | lttng enable-event --userspace my_provider:event_instance2 | |
864 | ---------------------------------------------------------- | |
865 | ||
866 | Run the application: | |
867 | ||
868 | [role="term"] | |
869 | -------------------- | |
870 | ./app some arguments | |
871 | -------------------- | |
872 | ||
873 | Stop the current tracing session and inspect the recorded events: | |
874 | ||
875 | [role="term"] | |
876 | ---------- | |
877 | lttng stop | |
878 | lttng view | |
879 | ---------- | |
880 | ||
885adac8 PP |
881 | |
882 | Tracepoint provider header file | |
883 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
884 | `tp.h`: | |
4ddbd0b7 PP |
885 | |
886 | ------------------------------------------------------------------------ | |
887 | #undef TRACEPOINT_PROVIDER | |
888 | #define TRACEPOINT_PROVIDER my_provider | |
889 | ||
890 | #undef TRACEPOINT_INCLUDE | |
891 | #define TRACEPOINT_INCLUDE "./tp.h" | |
892 | ||
893 | #if !defined(_TP_H) || defined(TRACEPOINT_HEADER_MULTI_READ) | |
894 | #define _TP_H | |
895 | ||
896 | #include <lttng/tracepoint.h> | |
897 | #include <stdio.h> | |
898 | ||
899 | #include "app.h" | |
900 | ||
901 | TRACEPOINT_EVENT( | |
902 | my_provider, | |
903 | simple_event, | |
904 | TP_ARGS( | |
905 | int, my_integer_arg, | |
906 | const char *, my_string_arg | |
907 | ), | |
908 | TP_FIELDS( | |
909 | ctf_string(argc, my_string_arg) | |
910 | ctf_integer(int, argv, my_integer_arg) | |
911 | ) | |
912 | ) | |
913 | ||
914 | TRACEPOINT_ENUM( | |
915 | my_provider, | |
916 | my_enum, | |
917 | TP_ENUM_VALUES( | |
918 | ctf_enum_value("ZERO", 0) | |
919 | ctf_enum_value("ONE", 1) | |
920 | ctf_enum_value("TWO", 2) | |
921 | ctf_enum_range("A RANGE", 52, 125) | |
922 | ctf_enum_value("ONE THOUSAND", 1000) | |
923 | ) | |
924 | ) | |
925 | ||
926 | TRACEPOINT_EVENT( | |
927 | my_provider, | |
928 | big_event, | |
929 | TP_ARGS( | |
930 | int, my_integer_arg, | |
931 | const char *, my_string_arg, | |
932 | FILE *, stream, | |
933 | double, flt_arg, | |
934 | int *, array_arg | |
935 | ), | |
936 | TP_FIELDS( | |
937 | ctf_integer(int, int_field1, my_integer_arg * 2) | |
938 | ctf_integer_hex(long int, stream_pos, ftell(stream)) | |
939 | ctf_float(double, float_field, flt_arg) | |
940 | ctf_string(string_field, my_string_arg) | |
941 | ctf_array(int, array_field, array_arg, 7) | |
942 | ctf_array_text(char, array_text_field, array_arg, 5) | |
943 | ctf_sequence(int, seq_field, array_arg, int, | |
944 | my_integer_arg / 10) | |
945 | ctf_sequence_text(char, seq_text_field, array_arg, | |
946 | int, my_integer_arg / 5) | |
947 | ctf_enum(my_provider, my_enum, int, | |
948 | enum_field, array_arg[1]) | |
949 | ) | |
950 | ) | |
951 | ||
952 | TRACEPOINT_LOGLEVEL(my_provider, big_event, TRACE_WARNING) | |
953 | ||
954 | TRACEPOINT_EVENT_CLASS( | |
955 | my_provider, | |
956 | my_tracepoint_class, | |
957 | TP_ARGS( | |
958 | int, my_integer_arg, | |
959 | struct app_struct *, app_struct_arg | |
960 | ), | |
961 | TP_FIELDS( | |
962 | ctf_integer(int, a, my_integer_arg) | |
963 | ctf_integer(unsigned long, b, app_struct_arg->b) | |
964 | ctf_string(c, app_struct_arg->c) | |
965 | ) | |
966 | ) | |
967 | ||
968 | TRACEPOINT_EVENT_INSTANCE( | |
969 | my_provider, | |
970 | my_tracepoint_class, | |
971 | event_instance1, | |
972 | TP_ARGS( | |
973 | int, my_integer_arg, | |
974 | struct app_struct *, app_struct_arg | |
975 | ) | |
976 | ) | |
977 | ||
978 | TRACEPOINT_EVENT_INSTANCE( | |
979 | my_provider, | |
980 | my_tracepoint_class, | |
981 | event_instance2, | |
982 | TP_ARGS( | |
983 | int, my_integer_arg, | |
984 | struct app_struct *, app_struct_arg | |
985 | ) | |
986 | ) | |
987 | ||
988 | TRACEPOINT_LOGLEVEL(my_provider, event_instance2, TRACE_INFO) | |
989 | ||
990 | TRACEPOINT_EVENT_INSTANCE( | |
991 | my_provider, | |
992 | my_tracepoint_class, | |
993 | event_instance3, | |
994 | TP_ARGS( | |
995 | int, my_integer_arg, | |
996 | struct app_struct *, app_struct_arg | |
997 | ) | |
998 | ) | |
999 | ||
1000 | #endif /* _TP_H */ | |
1001 | ||
1002 | #include <lttng/tracepoint-event.h> | |
1003 | ------------------------------------------------------------------------ | |
1004 | ||
885adac8 PP |
1005 | |
1006 | Tracepoint provider source file | |
1007 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
1008 | `tp.c`: | |
4ddbd0b7 PP |
1009 | |
1010 | ------------------------------------------------------------------------ | |
1011 | #define TRACEPOINT_CREATE_PROBES | |
1012 | #define TRACEPOINT_DEFINE | |
1013 | ||
1014 | #include "tp.h" | |
1015 | ------------------------------------------------------------------------ | |
1016 | ||
885adac8 PP |
1017 | |
1018 | Application header file | |
1019 | ~~~~~~~~~~~~~~~~~~~~~~~ | |
1020 | `app.h`: | |
4ddbd0b7 PP |
1021 | |
1022 | ------------------------------------------------------------------------ | |
1023 | #ifndef _APP_H | |
1024 | #define _APP_H | |
1025 | ||
1026 | struct app_struct { | |
1027 | unsigned long b; | |
1028 | const char *c; | |
1029 | double d; | |
1030 | }; | |
1031 | ||
1032 | #endif /* _APP_H */ | |
1033 | ------------------------------------------------------------------------ | |
1034 | ||
885adac8 PP |
1035 | |
1036 | Application source file | |
1037 | ~~~~~~~~~~~~~~~~~~~~~~~ | |
1038 | `app.c`: | |
4ddbd0b7 PP |
1039 | |
1040 | ------------------------------------------------------------------------ | |
1041 | #include <stdlib.h> | |
1042 | #include <stdio.h> | |
1043 | ||
1044 | #include "tp.h" | |
1045 | #include "app.h" | |
1046 | ||
1047 | static int array_of_ints[] = { | |
1048 | 100, -35, 1, 23, 14, -6, 28, 1001, -3000, | |
1049 | }; | |
1050 | ||
1051 | int main(int argc, char* argv[]) | |
1052 | { | |
1053 | FILE *stream; | |
1054 | struct app_struct app_struct; | |
1055 | ||
1056 | tracepoint(my_provider, simple_event, argc, argv[0]); | |
1057 | stream = fopen("/tmp/app.txt", "w"); | |
1058 | ||
1059 | if (!stream) { | |
1060 | fprintf(stderr, | |
1061 | "Error: Cannot open /tmp/app.txt for writing\n"); | |
1062 | return EXIT_FAILURE; | |
1063 | } | |
1064 | ||
1065 | if (fprintf(stream, "0123456789") != 10) { | |
1066 | fclose(stream); | |
1067 | fprintf(stderr, "Error: Cannot write to /tmp/app.txt\n"); | |
1068 | return EXIT_FAILURE; | |
1069 | } | |
1070 | ||
1071 | tracepoint(my_provider, big_event, 35, "hello tracepoint", | |
1072 | stream, -3.14, array_of_ints); | |
1073 | fclose(stream); | |
1074 | app_struct.b = argc; | |
1075 | app_struct.c = "[the string]"; | |
1076 | tracepoint(my_provider, event_instance1, 23, &app_struct); | |
1077 | app_struct.b = argc * 5; | |
1078 | app_struct.c = "[other string]"; | |
1079 | tracepoint(my_provider, event_instance2, 17, &app_struct); | |
1080 | app_struct.b = 23; | |
1081 | app_struct.c = "nothing"; | |
1082 | tracepoint(my_provider, event_instance3, -52, &app_struct); | |
1083 | ||
1084 | return EXIT_SUCCESS; | |
1085 | } | |
1086 | ------------------------------------------------------------------------ | |
1087 | ||
4ddbd0b7 | 1088 | |
174434f5 PP |
1089 | ENVIRONMENT VARIABLES |
1090 | --------------------- | |
0ce82328 | 1091 | `LTTNG_HOME`:: |
14dd1c6f PP |
1092 | Alternative user's home directory. This variable is useful when the |
1093 | user running the instrumented application has a non-writable home | |
0ce82328 PP |
1094 | directory. |
1095 | + | |
1096 | Unix sockets used for the communication between `liblttng-ust` and the | |
1097 | LTTng session and consumer daemons (part of the LTTng-tools project) | |
1098 | are located in a specific directory under `$LTTNG_HOME` (or `$HOME` if | |
1099 | `$LTTNG_HOME` is not set). | |
1100 | ||
62c2f155 PP |
1101 | `LTTNG_UST_CLOCK_PLUGIN`:: |
1102 | Path to the shared object which acts as the clock override plugin. | |
1103 | An example of such a plugin can be found in the LTTng-UST | |
1104 | documentation under | |
1105 | https://github.com/lttng/lttng-ust/tree/master/doc/examples/clock-override[`examples/clock-override`]. | |
1106 | ||
174434f5 | 1107 | `LTTNG_UST_DEBUG`:: |
14dd1c6f | 1108 | Activates `liblttng-ust`'s debug and error output if set to `1`. |
174434f5 | 1109 | |
62c2f155 PP |
1110 | `LTTNG_UST_GETCPU_PLUGIN`:: |
1111 | Path to the shared object which acts as the `getcpu()` override | |
1112 | plugin. An example of such a plugin can be found in the LTTng-UST | |
1113 | documentation under | |
1114 | https://github.com/lttng/lttng-ust/tree/master/doc/examples/getcpu-override[`examples/getcpu-override`]. | |
1115 | ||
174434f5 | 1116 | `LTTNG_UST_REGISTER_TIMEOUT`:: |
14dd1c6f PP |
1117 | Waiting time for the _registration done_ session daemon command |
1118 | before proceeding to execute the main program (milliseconds). | |
174434f5 | 1119 | + |
14dd1c6f PP |
1120 | The value `0` means _do not wait_. The value `-1` means _wait forever_. |
1121 | Setting this environment variable to `0` is recommended for applications | |
174434f5 PP |
1122 | with time constraints on the process startup time. |
1123 | + | |
2b4444ce | 1124 | Default: {lttng_ust_register_timeout}. |
174434f5 PP |
1125 | |
1126 | `LTTNG_UST_WITHOUT_BADDR_STATEDUMP`:: | |
14dd1c6f PP |
1127 | Prevents `liblttng-ust` from performing a base address state dump |
1128 | (see the <<state-dump,LTTng-UST state dump>> section above) if | |
1129 | set to `1`. | |
174434f5 | 1130 | |
174434f5 | 1131 | |
4ddbd0b7 PP |
1132 | include::common-footer.txt[] |
1133 | ||
1134 | include::common-copyrights.txt[] | |
1135 | ||
1136 | include::common-authors.txt[] | |
1137 | ||
1138 | ||
1139 | SEE ALSO | |
1140 | -------- | |
1141 | man:tracef(3), | |
1142 | man:tracelog(3), | |
1143 | man:lttng-gen-tp(1), | |
1144 | man:lttng-ust-dl(3), | |
1145 | man:lttng-ust-cyg-profile(3), | |
1146 | man:lttng(1), | |
1147 | man:lttng-enable-event(1), | |
1148 | man:lttng-list(1), | |
1149 | man:lttng-add-context(1), | |
1150 | man:babeltrace(1), | |
1151 | man:dlopen(3), | |
1152 | man:ld.so(8) |