-build instructions for userspace-rcu library :
+Userspace RCU Implementation
+by Mathieu Desnoyers and Paul E. McKenney
-make pthreads-x86
-or
-make pthreads-ppc
+BUILDING
+--------
-make
-make install
+ make
+ make install
+
-Usage :
+QUICK START GUIDE
+-----------------
-Registration of _each thread_ calling read-side critical sections must be done
-with rcu_register_thread() before using rcu_read_lock()/rcu_read_unlock().
+Initialization
+
+ Each thread that has reader critical sections (that uses
+ rcu_read_lock()/rcu_read_unlock() must first register to the URCU
+ library. This is done by calling rcu_register_thread().
+
+Reading
+
+ Reader critical sections must be protected by locating them between
+ calls to rcu_read_lock() and rcu_read_unlock(). Inside that lock,
+ rcu_dereference() may be called to read an RCU protected pointer.
+
+Writing
+
+ rcu_assign_pointer() and rcu_xchg_pointer() may be called anywhere.
+ After, synchronize_rcu() must be called. When it returns, the old
+ values are not in usage anymore.
+
+Being careful with signals
+
+ The urcu library uses signals internally. The signal handler is
+ registered with the SA_RESTART flag. However, these signals may cause
+ some non-restartable system calls to fail with errno = EINTR. Care
+ should be taken to restart system calls manually if they fail with this
+ error. A list of non-restartable system calls may be found in
+ signal(7). To ensure the Userspace RCU library does not use signals,
+ see "Usage of liburcu-mb" below.
+
+ Read-side critical sections can are allowed in a signal handler with
+ liburcu and liburcu-mb. Be careful, however, to disable these signals
+ between thread creation and calls to rcu_register_thread(), because a
+ signal handler nesting on an unregistered thread would not be allowed to
+ call rcu_read_lock().
+
+Usage of liburcu
+
+ This is the preferred version of the library, both in terms of speed and
+ flexibility. Define _LGPL_SOURCE if your code is LGPL or GPL (otherwise
+ function calls will be generated instead of inlines). Use the urcu.h
+ header. Link the application with "-lurcu".
+
+Usage of liburcu-mb
+
+ Compile code with "-DCONFIG_URCU_AVOID_SIGNALS" and link with
+ "-lurcu-mb" to use a version of the urcu library which does not need to
+ reserve a signal number. CONFIG_URCU_AVOID_SIGNALS uses full SMP
+ barriers for readers. This eliminates the need for signals but results
+ in slower reads.
+
+Usage of liburcu-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. Link with "-lurcu-qsbr" and use urcu-qsbr.h.
+
+Usage of DEBUG_RCU
+
+ DEBUG_RCU is used to add internal debugging self-checks to the
+ RCU library. This define adds a performance penality when enabled.
+ Can be enabled by uncommenting the corresponding line in
+ Makefile.build.inc.
+
+Usage of DEBUG_YIELD
+
+ DEBUG_YIELD is used to add random delays in the code for testing
+ purposes.
-Unregistration should be performed with rcu_unregister_thread() before exiting
-the thread.
- Mathieu Desnoyers