Allow taking address of rcu_read_lock() and rcu_read_unlock()

[urcu.git] / README

diff --git a/README b/README
index 796b9cfcd4dbad1d87775b22e53559dcdf7df7ed..659511f7c46eba7260e1297ae247efceaa88b7bf 100644 (file)
--- a/README
+++ b/README
@@ -24,11 +24,11 @@ BUILDING
 ARCHITECTURES SUPPORTED
 -----------------------
 
-Currently, x86 (i386, i486, i586, i686), x86 64-bit, PowerPC 32/64, S390, S390x
-ARMv7l, Alpha, ia64 and Sparcv9 32/64 are supported. Only tested on Linux so
+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.
 
-ARMv7l depends on running a Linux kernel 2.6.15 or better.
+ARM depends on running a Linux kernel 2.6.15 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:
@@ -38,7 +38,7 @@ supported, with the following exceptions:
   therefore not compatible with liburcu on x86 32-bit (i386, i486, i586, i686).
   The problem has been reported to the gcc community:
     http://www.mail-archive.com/gcc-bugs@gcc.gnu.org/msg281255.html
-- Alpha, ia64 and ARMv7l architectures depend on 4.x gcc with atomic builtins
+- Alpha, ia64 and ARM architectures depend on 4.x gcc with atomic builtins
   support.
 
 
@@ -190,3 +190,24 @@ SMP support
                ./configure --disable-smp-support
 
        theoretically yielding slightly better performance.
+
+Interaction with fork()
+
+       Special care must be taken for applications performing fork() without
+       any following exec(). This is caused by the fact that Linux only clones
+       the thread calling fork(), and thus never replicates any of the other
+       parent thread into the child process. Most liburcu implementations
+       require that all registrations (as reader, defer_rcu and call_rcu
+       threads) should be released before a fork() is performed, except for the
+       rather common scenario where fork() is immediately followed by exec() in
+       the child process. The only implementation not subject to that rule is
+       liburcu-bp, which is designed to handle fork() by calling
+       rcu_bp_before_fork, rcu_bp_after_fork_parent and
+       rcu_bp_after_fork_child.
+
+       Applications that use call_rcu() and that fork() without
+       doing an immediate exec() must take special action.  The parent
+       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().