Merge branch 'urcu/ht-shrink'

[urcu.git] / README

diff --git a/README b/README
index 1e76f2d1b098bb9579d573fcf8f36211c3c7c5f9..104ef2ab4eb481383b19c89dd7619b077d948680 100644 (file)
--- a/README
+++ b/README
@@ -29,7 +29,7 @@ Currently, x86 (i386, i486, i586, i686), x86 64-bit, PowerPC 32/64, S390, S390x,
 ARM, Alpha, ia64 and Sparcv9 32/64 are supported. Only tested on Linux so
 far, but should theoretically work on other operating systems.
 
-ARM depends on running a Linux kernel 2.6.15 or better.
+ARM depends on running a Linux kernel 2.6.15 or better, GCC 4.4 or better.
 
 The gcc compiler versions 3.3, 3.4, 4.0, 4.1, 4.2, 4.3, 4.4 and 4.5 are
 supported, with the following exceptions:
@@ -41,8 +41,24 @@ supported, with the following exceptions:
     http://www.mail-archive.com/gcc-bugs@gcc.gnu.org/msg281255.html
 - gcc 3.3 cannot match the "xchg" instruction on 32-bit x86 build.
   See: http://kerneltrap.org/node/7507
-- Alpha, ia64 and ARM architectures depend on 4.x gcc with atomic builtins
-  support.
+- Alpha, ia64 and ARM architectures depend on gcc 4.x with atomic builtins
+  support. For ARM this was introduced with gcc 4.4:
+    http://gcc.gnu.org/gcc-4.4/changes.html
+
+For developers using the git tree:
+
+This source tree is based on the autotools suite from GNU to simplify
+portability. Here are some things you should have on your system in order to
+compile the git repository tree :
+
+- GNU autotools (automake >=1.10, autoconf >=2.50, autoheader >=2.50)
+  (make sure your system wide "automake" points to a recent version!)
+- GNU Libtool >=2.2
+  (for more information, go to http://www.gnu.org/software/autoconf/)
+
+If you get the tree from the repository, you will need to use the "bootstrap"
+script in the root of the tree. It calls all the GNU tools needed to prepare the
+tree configuration.
 
 
 QUICK START GUIDE
@@ -187,6 +203,15 @@ Interaction with mutexes
        mutex in its dependency chain) should not be acquired from within a RCU
        read-side critical section.
 
+       This is especially important to understand in the context of the
+       QSBR flavor: a registered reader thread being "online" by
+       default should be considered as within a RCU read-side critical
+       section unless explicitly put "offline". Therefore, if
+       synchronize_rcu() is called with a mutex held, this mutex, as
+       well as any mutex which has this mutex in its dependency chain
+       should only be taken when the RCU reader thread is "offline"
+       (this can be performed by calling rcu_thread_offline()).
+
 Usage of DEBUG_RCU
 
        DEBUG_RCU is used to add internal debugging self-checks to the