X-Git-Url: https://git.lttng.org/?a=blobdiff_plain;f=doc%2Fman%2Flttng-ust.3;h=c92d3ca7b17415891fa7706f2824a0d17189895e;hb=7bf3e91619acb136eeb30410e59ed558429cd15c;hp=5effb9f5a3b8b5c63f27cc686bd2a5daa46f0eeb;hpb=77ca1460d75b4f364aeb2002673569c69e59ecc8;p=lttng-ust.git diff --git a/doc/man/lttng-ust.3 b/doc/man/lttng-ust.3 index 5effb9f5..c92d3ca7 100644 --- a/doc/man/lttng-ust.3 +++ b/doc/man/lttng-ust.3 @@ -40,11 +40,11 @@ focus on the various types that can be recorded into a trace event: TRACEPOINT_EVENT( /* * provider name, not a variable but a string starting with a - * letter and containing either letters, numbers or underscores. + * letter and containing either letters, numbers or underscores. * Needs to be the same as TRACEPOINT_PROVIDER. Needs to * follow the namespacing guide-lines in lttng/tracepoint.h: - * - * Must be included before include tracepoint provider + * + * Must be included before include tracepoint provider * ex.: project_event * ex.: project_component_event * @@ -59,19 +59,19 @@ TRACEPOINT_EVENT( /* * tracepoint name, same format as sample provider. Does not * need to be declared before. in this case the name is - * "message" + * "message" */ message, /* - * TP_ARGS macro contains the arguments passed for the tracepoint + * TP_ARGS macro contains the arguments passed for the tracepoint * it is in the following format * TP_ARGS(type1, name1, type2, name2, ... type10, name10) - * where there can be from zero to ten elements. - * typeN is the datatype, such as int, struct or double **. + * where there can be from zero to ten elements. + * typeN is the datatype, such as int, struct or double **. * name is the variable name (in "int myInt" the name would be - * myint) + * myint) * TP_ARGS() is valid to mean no arguments * TP_ARGS(void) is valid too */ @@ -80,7 +80,7 @@ TRACEPOINT_EVENT( double, doublearg, float, floatarg), /* - * TP_FIELDS describes how to write the fields of the trace event. + * TP_FIELDS describes how to write the fields of the trace event. * You can put expressions in the "argument expression" area, * typically using the input arguments from TP_ARGS. */ @@ -109,27 +109,34 @@ TRACEPOINT_EVENT( /* * ctf_array: a statically-sized array. * args: (type, field name, argument expression, value) - */ + */ ctf_array(long, arrfield1, values, 3) /* * ctf_array_text: a statically-sized array, printed as * a string. No need to be terminated by a null * character. - */ + * Behavior is undefined if "text" argument is NULL. + */ ctf_array_text(char, arrfield2, text, 10) /* * ctf_sequence: a dynamically-sized array. * args: (type, field name, argument expression, * type of length expression, length expression) - */ + * The "type of length expression" needs to be an + * unsigned type. As a reminder, "unsigned char" should + * be preferred to "char", since the signedness of + * "char" is implementation-defined. + * Behavior is undefined if "text" argument is NULL. + */ ctf_sequence(char, seqfield1, text, size_t, textlen) /* * ctf_sequence_text: a dynamically-sized array, printed * as string. No need to be null-terminated. + * Behavior is undefined if "text" argument is NULL. */ ctf_sequence_text(char, seqfield2, text, size_t, textlen) @@ -137,6 +144,7 @@ TRACEPOINT_EVENT( /* * ctf_string: null-terminated string. * args: (field name, argument expression) + * Behavior is undefined if "text" argument is NULL. */ ctf_string(stringfield, text) @@ -148,6 +156,11 @@ TRACEPOINT_EVENT( ctf_float(double, doublefield, doublearg) ) ) + +There can be an arbitrary number of tracepoint providers within an +application, but they must each have their own provider name. Duplicate +provider names are not allowed. + .fi .SH "ASSIGNING LOGLEVEL TO EVENTS" @@ -168,54 +181,54 @@ declared before declaring a TRACEPOINT_LOGLEVEL. The loglevels go from 0 to 14. Higher numbers imply the most verbosity (higher event throughput expected. - + Loglevels 0 through 6, and loglevel 14, match syslog(3) loglevels semantic. Loglevels 7 through 13 offer more fine-grained selection of debug information. - + TRACE_EMERG 0 system is unusable - + TRACE_ALERT 1 action must be taken immediately - + TRACE_CRIT 2 critical conditions - + TRACE_ERR 3 error conditions - + TRACE_WARNING 4 warning conditions - + TRACE_NOTICE 5 normal, but significant, condition - + TRACE_INFO 6 informational message - + TRACE_DEBUG_SYSTEM 7 debug information with system-level scope (set of programs) - + TRACE_DEBUG_PROGRAM 8 debug information with program-level scope (set of processes) - + TRACE_DEBUG_PROCESS 9 debug information with process-level scope (set of modules) - + TRACE_DEBUG_MODULE 10 debug information with module (executable/library) scope (set of units) - + TRACE_DEBUG_UNIT 11 debug information with compilation unit scope (set of functions) - + TRACE_DEBUG_FUNCTION 12 debug information with function-level scope - + TRACE_DEBUG_LINE 13 debug information with line-level scope (TRACEPOINT_EVENT default) - + TRACE_DEBUG 14 debug-level message (trace_printf default) @@ -264,8 +277,10 @@ carefully: library with "\-llttng-ust". - Include the tracepoint provider header into all C files using the provider. - - Example: - - tests/hello/ hello.c tp.c ust_tests_hello.h Makefile.example + - Examples: + - doc/examples/easy-ust/ sample.c sample_component_provider.h tp.c + Makefile + - doc/examples/hello-static-lib/ hello.c tp.c ust_test_hello.h Makefile 2) Compile the Tracepoint Provider separately from the application, using dynamic linking: @@ -283,7 +298,7 @@ carefully: needed. Another way is to dlopen the tracepoint probe when needed by the application. - Example: - - doc/examples/demo demo.c tp*.c ust_tests_demo*.h demo-trace + - doc/examples/demo demo.c tp*.c ust_tests_demo*.h demo-trace Makefile - Note about dlclose() usage: it is not safe to use dlclose on a provider shared object that is being actively used for tracing due @@ -363,10 +378,23 @@ startup time. lttng-gen-tp(1), lttng(1), babeltrace(1), lttng-ust-cyg-profile(3), lttng-sessiond(8) .PP + +.SH "COMPATIBILITY" + +.PP +Older lttng-ust libraries reject more recent, and incompatible, probe +providers. Newer lttng-ust librairies accept older probe providers, even +though some newer features might not be available with those providers. +.PP + .SH "BUGS" .PP -No known bugs at this point. +LTTng-UST 2.0 and 2.1 lttng-ust libraries do not check for probe +provider version compatibility. This can lead to out-of-bound accesses +when using a more recent probe provider with an older lttng-ust library. +These error only trigger when tracing is active. This issue has been +fixed in LTTng-UST 2.2. If you encounter any issues or usability problem, please report it on our mailing list to help improve this