X-Git-Url: https://git.lttng.org/?p=urcu.git;a=blobdiff_plain;f=README;h=e5c04b179cae49d202a49809d09a76f714ada711;hp=d71bbe7597e1fb893cd13742cbb16f6e7ef61e1c;hb=074d8438a30f7da8ae12eb94caff69c37fb576bd;hpb=c97ae6eb5bf6baea503d9df98e8376c0bd36b629

diff --git a/README b/README
index d71bbe7..e5c04b1 100644
--- a/README
+++ b/README
@@ -1,21 +1,62 @@
-Userspace RCU Implementatation
+Userspace RCU Implementation
 by Mathieu Desnoyers and Paul E. McKenney
 
 BUILDING
 --------
 
 	make
+	#force 32-bit build with: make -f Makefile32
+	#force 64-bit build with: make -f Makefile64
 	make install
 	
 
 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.
+
 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().
+	library. This is done by calling rcu_register_thread(). Unregistration
+	must be performed before exiting the thread by using
+	rcu_unregister_thread().
 
 Reading
 
@@ -26,18 +67,47 @@ Reading
 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 DEBUG_FULL_MB
-
-	DEBUG_FULL_MB uses full SMP barriers for readers. This eliminates the
-	need for signals but results in slower reads.
-
+	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"
+	* Provides call_rcu() primitive to enqueue delayed callbacks. Queued
+	  callbacks are executed in batch periodically after a grace period.
+	  Do _not_ use call_rcu() within a read-side critical section, because
+	  it may call synchronize_rcu() if the thread queue is full.
+
+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.
-