to user-space. The library "liblttng-ust" enables tracing of
applications and libraries.
-.SH "USAGE"
+.SH "USAGE WITH TRACEF"
+.PP
+The simplest way to add instrumentation to your code is by far the
+tracef() API. To do it, in a nutshell:
+
+1) #include <lttng/tracef.h>
+
+2) /* in your code, use like a printf */
+ tracef("my message, this integer %d", 1234);
+
+3) Link your program against liblttng-ust.so.
+
+4) Enable UST events when tracing with the following sequence of commands
+ from lttng-tools:
+
+ lttng create
+ lttng enable-event -u -a
+ lttng start
+ [... run your program ...]
+ lttng stop
+ lttng view
+
+That's it!
+
+If you want to have more flexibility and control on the event names,
+payload typing, etc, you can continue reading on and use the tracepoints
+below. "tracef()" is there for quick and dirty ad hoc instrumentation,
+whereas tracepoint.h is meant for thorough instrumentation of a code
+base to be integrated with an upstream project.
+.PP
+
+.SH "USAGE WITH TRACEPOINT"
.PP
The simple way to generate the lttng-ust tracepoint probes is to use the
lttng-gen-tp(1) tool. See the lttng-gen-tp(1) manpage for explanation.
nicely to an unsigned long type.
.PP
-.SH "BASE ADDRESS STATEDUMP"
+.SH "BASE ADDRESS STATEDUMP (Experimental feature)"
.PP
+Warning: This is an experimental feature known to cause deadlocks when the
+traced application uses fork, clone or daemon. Only use it for debugging and
+testing. Do NOT use it in production.
+
If an application that uses liblttng-ust.so becomes part of a session,
information about its currently loaded shared objects will be traced to the
session at session-enable time. To record this information, the following event
.IP "ust_baddr_statedump:soinfo"
This event is used to trace a currently loaded shared object. The base address
(where the dynamic linker has placed the shared object) is recorded in the
-baddr-field. The path to the shared object gets recorded in the sopath-field
-(as string). The file size of the loaded object (in bytes) is recorded to the
-size-field and its time of last modification (in seconds since Epoch) is
-recorded in the mtime-field.
-.PP
-If the event above is enabled, a series of ust_baddr_statedump:soinfo events is
-recorded at session-enable time, that represents the state of currently loaded
-shared objects (of the traced application). If this information gets combined
-with the lttng-ust-dl(3) instrumentation, all aspects of dynamic loading that
-are relevant for symbol and linenumber-lookup are traced by LTTng.
+"baddr" field. The path to the shared object gets recorded in the
+"sopath" field (as string). The file size of the loaded object (in
+bytes) is recorded to the "size" field and its time of last modification
+(in seconds since Epoch) is recorded in the "mtime" field.
+.PP
+If the event above is enabled, a series of "ust_baddr_statedump:soinfo"
+events is recorded at session-enable time. It represents the state of
+currently loaded shared objects for the traced process. If this
+information gets combined with the lttng-ust-dl(3) instrumentation, all
+aspects of dynamic loading that are relevant for symbol and
+line number lookup are traced by LTTng.
.PP
.SH "ENVIRONMENT VARIABLES"
recommended for applications with time constraints on the process
startup time.
.PP
-.IP "LTTNG_UST_WITHOUT_BADDR_STATEDUMP"
-Prevent liblttng-ust to perform a base-address statedump on session-enable.
+.IP "LTTNG_UST_WITH_EXPERIMENTAL_BADDR_STATEDUMP"
+Experimentally allow liblttng-ust to perform a base-address statedump on session-enable.
.PP
.SH "SEE ALSO"