From 13fb2d2c14d49d2e5457df7b5f02e99e979464c3 Mon Sep 17 00:00:00 2001 From: =?utf8?q?J=C3=A9r=C3=A9mie=20Galarneau?= Date: Tue, 19 Mar 2013 16:43:32 -0400 Subject: [PATCH] Remove mention of locking issues associated with dlopen usage MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit This notice has been removed from the README as part of revision b834dead. Add a warning relating to dlclose() usage detailed in issue 447 in both the man page and the README file. Signed-off-by: Jérémie Galarneau Signed-off-by: Mathieu Desnoyers --- README | 6 +++++- doc/man/lttng-ust.3 | 14 +++++++------- 2 files changed, 12 insertions(+), 8 deletions(-) diff --git a/README b/README index 55c72df7..390a719b 100644 --- a/README +++ b/README @@ -75,7 +75,7 @@ USAGE: - 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.* + - tests/hello/ hello.c tp.c ust_tests_hello.h Makefile.example.* 2) Compile the Tracepoint Provider separately from the application, using dynamic linking: @@ -97,6 +97,10 @@ USAGE: - Enable instrumentation and control tracing with the "lttng" command from lttng-tools. See lttng-tools doc/quickstart.txt. + - 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. ENVIRONMENT VARIABLES: diff --git a/doc/man/lttng-ust.3 b/doc/man/lttng-ust.3 index 08927c64..7cc3bfde 100644 --- a/doc/man/lttng-ust.3 +++ b/doc/man/lttng-ust.3 @@ -265,7 +265,7 @@ carefully: - 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 + - tests/hello/ hello.c tp.c ust_tests_hello.h Makefile.example 2) Compile the Tracepoint Provider separately from the application, using dynamic linking: @@ -280,15 +280,15 @@ carefully: - 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 - - 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 -- 2.34.1