X-Git-Url: https://git.lttng.org/?a=blobdiff_plain;f=README;h=f9af1eb483d83d3cee27625efc0eaa5c48dbbe3e;hb=fb6e510b9ae45b9b984b4646b4be6b9d7a2bbf7c;hp=71cf729598bd8e5e9223246a3b5562bbaa017dd5;hpb=9fb223da744aff7501107d09d7502c2baadc421f;p=urcu.git

diff --git a/README b/README
index 71cf729..f9af1eb 100644
--- a/README
+++ b/README
@@ -29,15 +29,34 @@ 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 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,
+	define CONFIG_URCU_AVOID_SIGNALS at compile-time.
 
-	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 sit in a signal handler. 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 CONFIG_URCU_AVOID_SIGNALS
+
+	CONFIG_URCU_AVOID_SIGNALS uses full SMP barriers for readers. This
+	eliminates the need for signals but results in slower reads.
+
+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.
-