-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
+ ./bootstrap (skip if using tarball)
+ ./configure
+ make
+ make install
+ Hints: Forcing 32-bit build:
+ * CFLAGS="-m32 -g -O2" ./configure
- Mathieu Desnoyers
+ Forcing 64-bit build:
+ * CFLAGS="-m64 -g -O2" ./configure
+
+ Forcing a 32-bit build with 386 backward compatibility:
+ * CFLAGS="-m32 -g -O2" ./configure --host=i386-pc-linux-gnu
+
+ Forcing a 32-bit build for Sparcv9 (typical for Sparc v9)
+ * CFLAGS="-m32 -Wa,-Av9a -g -O2" ./configure
+
+ARCHITECTURES SUPPORTED
+-----------------------
+
+Currently, x86 (i386, i486, i586, i686), x86 64-bit, PowerPC 32/64, S390, S390x
+and Sparcv9 32/64 are supported. Only tested on Linux so far, but should
+theoretically work on other operating systems.
+
+QUICK START GUIDE
+-----------------
+
+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, both in terms of speed
+ and flexibility. Requires a signal, typically SIGUSR1. Can be
+ overridden with -DSIGURCU by modifying Makefile.build.inc.
+
+Usage of liburcu-mb
+
+ * #include <urcu.h>
+ * Compile any _LGPL_SOURCE code using this library with "-DURCU_MB".
+ * Link with "-lurcu-mb".
+ * This version of the urcu library does not need to
+ reserve a signal number. URCU_MB uses full memory barriers for
+ readers. This eliminates the need for signals but results in slower
+ reads.
+
+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-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. urcu_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.
+
+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(). Unregistration
+ must be performed before exiting the thread by using
+ rcu_unregister_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.
+
+Usage of liburcu-defer
+
+ * #include <urcu-defer.h>
+ * Link with "-lurcu-defer", and also with one of the urcu library
+ (either urcu, urcu-bp, urcu-mb or urcu-qsbr).
+ * Provides defer_rcu() primitive to enqueue delayed callbacks. Queued
+ callbacks are executed in batch periodically after a grace period.
+ Do _not_ use defer_rcu() within a read-side critical section, because
+ it may call synchronize_rcu() if the thread queue is full.
+ * Provides defer_rcu_ratelimit() primitive, which acts just like
+ defer_rcu(), but takes an additional rate limiter callback forcing
+ synchronized callback execution of the limiter returns non-zero.
+ * Requires that rcu_defer_barrier() must be called in library destructor
+ if a library queues callbacks and is expected to be unloaded with
+ dlclose().
+ * Its API is currently experimental. It may change in future library
+ releases.
+
+Being careful with signals
+
+ The liburcu 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). The liburcu-mb and liburcu-qsbr versions of the Userspace RCU
+ library do not require any signal.
+
+ Read-side critical sections 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().
+
+ Read-side critical sections are _not_ allowed in a signal handler with
+ liburcu-qsbr, unless signals are disabled explicitly around each
+ rcu_quiescent_state() calls, when threads are put offline and around
+ calls to synchronize_rcu(). Even then, we do not recommend it.
+
+Usage of DEBUG_RCU
+
+ DEBUG_RCU is used to add internal debugging self-checks to the
+ RCU library. This define adds a performance penalty 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.
+
+SMP support
+
+ By default the library is configured to use synchronization primitives
+ adequate for SMP systems. On uniprocessor systems, support for SMP
+ systems can be disabled with:
+
+ ./configure --disable-smp-support
+
+ theoretically yielding slightly better performance.