X-Git-Url: https://git.liburcu.org/?a=blobdiff_plain;f=README;h=93c0a742cedda21928f5333f93737409819f0908;hb=7ac06cef7a7d9394332837edc5c0e9595286a5fc;hp=71cf729598bd8e5e9223246a3b5562bbaa017dd5;hpb=9fb223da744aff7501107d09d7502c2baadc421f;p=urcu.git

diff --git a/README b/README
index 71cf729..93c0a74 100644
--- a/README
+++ b/README
@@ -1,4 +1,4 @@
-Userspace RCU Implementatation
+Userspace RCU Implementation
 by Mathieu Desnoyers and Paul E. McKenney
 
 BUILDING
@@ -29,15 +29,54 @@ Writing
 	After, synchronize_rcu() must be called. When it returns, the old
 	values are not in usage anymore.
 
+Being careful with signals
 
-Usage of DEBUG_FULL_MB
+	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.
 
-	DEBUG_FULL_MB uses full SMP barriers for readers. This eliminates the
-	need for signals but results in slower reads.
+	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.
 
+