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
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
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.