Version 0.7.17

[userspace-rcu.git] / README

diff --git a/README b/README
index 303c6ec48fc0fd948de29d1bc1319e523d7eadd4..197d8a5573764c14892f9f7ff5bd329b824bbf74 100644 (file)
--- a/README
+++ b/README
@@ -47,6 +47,15 @@ supported, with the following exceptions:
   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
@@ -259,4 +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.