- (see tracepoint.h and tests/hello/tp.h).
- - Link application with -lust.
- - (TODO: start tracing with the "lttng" command from lttng-tools)
-
- Note: libust debug can be activated by either of the following means:
- - Setting the environment variable "UST_DEBUG" when launching the
- application.
- - Compiling libust with -DUST_DEBUG.
+ See lttng/tracepoint.h, and examples.
+ - Either compile the Tracepoint probes with the application:
+ - Use "-I." for the compilation unit containing the tracepoint
+ provider include (e.g. tp.c).
+ - Link application with "-ldl -llttng-ust".
+ - Example:
+ tests/hello/ hello.c tp.c ust_tests_hello.h Makefile.example
+ - Or compile the Tracepoint probes separately from the application,
+ using dynamic linking:
+ - Compile the tracepoint provider with "-I.".
+ - Link the tracepoint provider with "-llttng-ust".
+ - Link application with "-ldl".
+ - Set a LD_PRELOAD environment to preload the tracepoint provider
+ shared object before starting the application when tracing is
+ needed.
+ - Example:
+ - tests/demo/ demo.c tp*.c ust_tests_demo*.h demo-trace
+ - 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.
+ - Enable instrumentation and control tracing with the "lttng" command
+ from lttng-tools. See lttng-tools doc/quickstart.txt.
+
+ENVIRONMENT VARIABLES:
+
+ - liblttng-ust debug can be activated by setting the environment variable
+ "LTTNG_UST_DEBUG" when launching the application. It can also be enabled
+ at compile-time by compiling libust with -DLTTNG_UST_DEBUG.
+
+ - The environment variable "LTTNG_UST_REGISTER_TIMEOUT" can be used to
+ specify how long the applications should wait for sessiond
+ "registration done" command before proceeding to execute the main
+ program. The default is 3000ms (3 seconds). The timeout value is
+ specified in milliseconds. The value 0 means "don't wait". The value
+ -1 means "wait forever". Setting this environment variable to 0 is
+ recommended for applications with time constraints on the process
+ startup time.