X-Git-Url: http://git.liburcu.org/?p=userspace-rcu.git;a=blobdiff_plain;f=README;h=197d8a5573764c14892f9f7ff5bd329b824bbf74;hp=e3800faad2d10cc5789c0a622c14f5ade9962ae1;hb=refs%2Fheads%2Fstable-0.7;hpb=cc558521e7bc8767bc78c93436cd4af3c6c84edd

diff --git a/README b/README
index e3800fa..197d8a5 100644
--- a/README
+++ b/README
@@ -25,11 +25,13 @@ BUILDING
 ARCHITECTURES SUPPORTED
 -----------------------
 
-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.
+Currently, Linux x86 (i386, i486, i586, i686), x86 64-bit, PowerPC 32/64,
+S390, S390x, ARM, Alpha, ia64 and Sparcv9 32/64 are supported. Tested on
+Linux, FreeBSD 8.2/9.0, and Cygwin. Should also work on: Android, NetBSD 5,
+OpenBSD, Darwin (more testing needed before claiming support for these OS).
 
-ARM depends on running a Linux kernel 2.6.15 or better.
+Linux 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 +43,36 @@ 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
+
+Clang version 3.0 (based on LLVM 3.0) is supported.
+
+Building on MacOS X (Darwin) requires a work-around for processor
+detection:
+  # 32-bit
+  ./configure --build=i686-apple-darwin11
+  # 64-bit
+  ./configure --build=x86_64-apple-darwin11
+
+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.
+
+Test scripts provided in the tests/ directory of the source tree depend
+on "bash" and the "seq" program.
 
 
 QUICK START GUIDE
@@ -156,7 +186,7 @@ Usage of urcu-call-rcu
 	  grace periods.  A number of additional functions are provided
 	  to manage the helper threads used by call_rcu(), but reasonable
 	  defaults are used if these additional functions are not invoked.
-	  See API.txt for more details.
+	  See rcu-api.txt in userspace-rcu documentation for more details.
 
 Being careful with signals
 
@@ -168,11 +198,12 @@ Being careful with signals
 	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
+	Read-side critical sections are allowed in a signal handler,
+	except those setup with sigaltstack(2), 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().
+	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
@@ -237,4 +268,24 @@ Interaction with fork()
 	must invoke call_rcu_before_fork() before the fork() and
 	call_rcu_after_fork_parent() after the fork().  The child
 	process must invoke call_rcu_after_fork_child().
-	These three APIs are suitable for passing to pthread_atfork().
+	Even though these three APIs are suitable for passing to
+	pthread_atfork(), use of pthread_atfork() is *STRONGLY
+	DISCOURAGED* for programs calling the glibc memory allocator
+	(malloc(), calloc(), free(), ...) within call_rcu callbacks.
+	This is due to limitations in the way glibc memory allocator
+	handles calls to the memory allocator from concurrent threads
+	while the pthread_atfork() handlers are executing.
+	Combining e.g.:
+	* call to free() from callbacks executed within call_rcu worker
+	  threads,
+	* executing call_rcu atfork handlers within the glibc pthread
+	  atfork mechanism,
+	will sometimes trigger interesting process hangs. This usually
+	hangs on a memory allocator lock within glibc.
+
+Thread Local Storage (TLS)
+
+	Userspace RCU can fall back on pthread_getspecific() to emulate
+	TLS variables on systems where it is not available. This behavior
+	can be forced by specifying --disable-compiler-tls as configure
+	argument.