.TH "LTTNG-UST" "3" "February 16, 2012" "" ""
.SH "NAME"
-lttng-ust \(em Linux Trace Toolkit Next Generation User-Space Tracer
+lttng-ust \(em Linux Trace Toolkit Next Generation User-Space Tracer 2.x
.SH "SYNOPSIS"
.SH "DESCRIPTION"
.PP
-LTTng-UST, the Linux Trace Toolkit Next Generation Userspace Tracer, is
+LTTng-UST, the Linux Trace Toolkit Next Generation Userspace Tracer, is a
port of the low-overhead tracing capabilities of the LTTng kernel tracer
to user-space. The library "liblttng-ust" enables tracing of
applications and libraries.
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
*
/*
* 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
*/
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.
*/
/*
* 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)
/*
* ctf_string: null-terminated string.
* args: (field name, argument expression)
+ * Behavior is undefined if "text" argument is NULL.
*/
ctf_string(stringfield, text)
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"
TRACEPOINT_LOGLEVEL(< [com_company_]project[_component] >,
< event >, < loglevel_name >)
- The first field is the provider name, the second field is the name of
+The first field is the provider name, the second field is the name of
the tracepoint, and the third field is the loglevel name. A
TRACEPOINT_EVENT should be declared prior to the the TRACEPOINT_LOGLEVEL
for a given tracepoint name. The TRACEPOINT_PROVIDER must be already
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)
As a call to the tracepoint. It will only be activated when requested by
lttng(1) through lttng-sessiond(8).
+Even though LTTng-UST supports tracepoint() call site duplicates having
+the same provider and event name, it is recommended to use a
+provider event name pair only once within the source code to help
+map events back to their call sites when analyzing the trace.
.fi
.SH "BUILDING/LINKING THE TRACEPOINT PROVIDER"
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:
- Link application with "\-ldl".
- Set a LD_PRELOAD environment to preload the tracepoint provider
shared object before starting the application when tracing is
- needed.
+ needed. Another way is to dlopen the tracepoint probe when needed
+ by the application.
- Example:
- - tests/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 dlopen() usage: due to locking side-effects due to the
- way libc lazily resolves Thread-Local Storage (TLS) symbols when a
- library is dlopen'd, linking the tracepoint probe or liblttng-ust
- with dlopen() is discouraged. They should be linked with the
- application using "\-llibname" or loaded with LD_PRELOAD.
+ - Note about dlclose() usage: it is not safe to use dlclose on a
+ provider shared object that is being actively used for tracing due
+ to a lack of reference counting from lttng-ust to the used shared
+ object.
- Enable instrumentation and control tracing with the "lttng" command
from lttng-tools. See lttng-tools doc/quickstart.txt.
- Note for C++ support: although an application instrumented with
.fi
+.SH "CONTEXT"
+
+.PP
+Context information can be prepended by the tracer before each, or some,
+events. The following context information is supported by LTTng-UST:
+.PP
+
+.PP
+.IP "vtid"
+Virtual thread ID: thread ID as seen from the point of view of the
+process namespace.
+.PP
+
+.PP
+.IP "vpid"
+Virtual process ID: process ID as seen from the point of view of the
+process namespace.
+.PP
+
+.PP
+.IP "procname"
+Thread name, as set by exec() or prctl(). It is recommended that
+programs set their thread name with prctl() before hitting the first
+tracepoint for that thread.
+.PP
+
+.PP
+.IP "pthread_id"
+Pthread identifier. Can be used on architectures where pthread_t maps
+nicely to an unsigned long type.
+.PP
+
.SH "ENVIRONMENT VARIABLES"
.PP
.SH "SEE ALSO"
.PP
-lttng-gen-tp(1), lttng(1), babeltrace(1), lttng-sessiond(8)
+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 libraries accept older probe providers, even
+though some newer features might not be available with those providers.
+.PP
+
.SH "BUGS"
.PP
-No knows 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 <lttng-dev@lists.lttng.org> to help improve this
projects / lttng-ust.git / blobdiff