Fix: liblttng-ust-fork Makefile flags mismatch

[lttng-ust.git] / README

diff --git a/README b/README
index e2b52aa026f74a3ff598c774bc034baefe01c5aa..71bae95b6d62303a9261a754dbefc44c3897a008 100644 (file)
--- a/README
+++ b/README
@@ -16,7 +16,7 @@ PREREQUISITES:
   - liburcu
     Userspace RCU library, by Mathieu Desnoyers and Paul E. McKenney
 
-    -> This release depends on liburcu v0.6.6
+    -> This release depends on liburcu v0.7.2
 
       * Debian/Ubuntu package: liburcu-dev
       * Website:  http://lttng.org/urcu
@@ -24,6 +24,9 @@ PREREQUISITES:
       * GitWeb:   http://lttng.org/cgi-bin/gitweb.cgi?p=userspace-rcu.git;a=summary
       * Git:      git://lttng.org/userspace-rcu.git
 
+  - libuuid (for Linux)
+      * Debian/Ubuntu package: libuuid1, uuid-dev
+
 For developers using the git tree:
 
 This source tree is based on the autotools suite from GNU to simplify
@@ -67,15 +70,15 @@ USAGE:
       "TRACEPOINT_DEFINE" and include the tracepoint provider.
     - Use "-I." for the compilation unit containing the tracepoint
       provider include (e.g. tp.c).
-    - Link application with "-ldl".
+    - Link application with "-ldl" on Linux, with "-lc" on BSD.
     - If building the provider directly into the application,
       link the application with "-llttng-ust".
     - If building a static library for the provider, link the static
-      library with "-lllttng-ust".
+      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
+      - tests/hello/  hello.c tp.c ust_tests_hello.h Makefile.example.*
 
   2) Compile the Tracepoint Provider separately from the application,
      using dynamic linking:
@@ -87,20 +90,20 @@ USAGE:
       files that use the provider.
     - Compile the tracepoint provider with "-I.".
     - Link the tracepoint provider with "-llttng-ust".
-    - Link application with "-ldl".
+    - Link application with "-ldl" on Linux, "-lc" on BSD.
     - 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.
   - 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:
 
@@ -117,6 +120,10 @@ ENVIRONMENT VARIABLES:
     recommended for applications with time constraints on the process
     startup time.
 
+  - The compilation flag "-DLTTNG_UST_DEBUG_VALGRIND" should be enabled
+    at build time to allow liblttng-ust to be used with valgrind
+    (side-effect: disables per-cpu buffering).
+
 
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