From: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Date: Tue, 19 Mar 2013 20:43:32 +0000 (-0400)
Subject: Remove mention of locking issues associated with dlopen usage
X-Git-Tag: v2.1.2~3
X-Git-Url: https://git.lttng.org/?a=commitdiff_plain;h=5ce002183cf11c88ab35b2d5bcd39556e824f374;p=lttng-ust.git

Remove mention of locking issues associated with dlopen usage

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 <jeremie.galarneau@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
---

diff --git a/README b/README
index 5de1885a..1ff23f69 100644
--- a/README
+++ b/README
@@ -78,7 +78,7 @@ 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:
@@ -100,6 +100,10 @@ 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