+Usage of all urcu libraries
+
+ * Define _LGPL_SOURCE (only) if your code is LGPL or GPL compatible
+ before including the urcu.h or urcu-qsbr.h header. If your application
+ is distributed under another license, function calls will be generated
+ instead of inlines, so your application can link with the library.
+ * Linking with one of the libraries below is always necessary even for
+ LGPL and GPL applications.
+
+Usage of liburcu
+
+ * #include <urcu.h>
+ * Link the application with "-lurcu".
+ * This is the preferred version of the library, in terms of
+ grace-period detection speed, read-side speed and flexibility.
+ Dynamically detects kernel support for sys_membarrier(). Falls back
+ on urcu-mb scheme if support is not present, which has slower
+ read-side.
+
+Usage of liburcu-qsbr
+
+ * #include <urcu-qsbr.h>
+ * Link with "-lurcu-qsbr".
+ * The QSBR flavor of RCU needs to have each reader thread executing
+ rcu_quiescent_state() periodically to progress. rcu_thread_online()
+ and rcu_thread_offline() can be used to mark long periods for which
+ the threads are not active. It provides the fastest read-side at the
+ expense of more intrusiveness in the application code.
+
+Usage of liburcu-mb
+
+ * #include <urcu.h>
+ * Compile any _LGPL_SOURCE code using this library with "-DRCU_MB".
+ * Link with "-lurcu-mb".
+ * This version of the urcu library uses memory barriers on the writer
+ and reader sides. This results in faster grace-period detection, but
+ results in slower reads.
+
+Usage of liburcu-signal
+
+ * #include <urcu-signal.h>
+ * Link the application with "-lurcu-signal".
+ * Version of the library that requires a signal, typically SIGUSR1. Can
+ be overridden with -DSIGRCU by modifying Makefile.build.inc.
+
+Usage of liburcu-bp
+
+ * #include <urcu-bp.h>
+ * Link with "-lurcu-bp".
+ * The BP library flavor stands for "bulletproof". It is specifically
+ designed to help tracing library to hook on applications without
+ requiring to modify these applications. rcu_init(),
+ rcu_register_thread() and rcu_unregister_thread() all become nops.
+ The state is dealt with by the library internally at the expense of
+ read-side and write-side performance.
+