./configure
make
make install
+ ldconfig
Hints: Forcing 32-bit build:
* CFLAGS="-m32 -g -O2" ./configure
Forcing 64-bit build:
* CFLAGS="-m64 -g -O2" ./configure
- Forcing a 32-bit build with down to 386 compatibility:
- * CFLAGS="-m32 -g -O2" ./configure --target=i386-pc-linux-gnu
+ Forcing a 32-bit build with 386 backward compatibility:
+ * CFLAGS="-m32 -g -O2" ./configure --host=i386-pc-linux-gnu
+
+ Forcing a 32-bit build for Sparcv9 (typical for Sparc v9)
+ * CFLAGS="-m32 -Wa,-Av9a -g -O2" ./configure
+
ARCHITECTURES SUPPORTED
-----------------------
-Currently, x86 (i386, i486, i586, i686), x86 64, PowerPC 32/64 and S390 are
-supported. The current use of sys_futex() makes it Linux-dependent, although
-this portability limitation might go away in a near future by using the pthread
-cond vars.
+Currently, Linux x86 (i386, i486, i586, i686), x86 64-bit, PowerPC 32/64,
+S390, S390x, ARM, MIPS, Alpha, ia64 and Sparcv9 32/64 are supported.
+Tested on Linux, FreeBSD 8.2/8.3/9.0/9.1/10.0 i386/amd64, and Cygwin.
+Should also work on: Android, NetBSD 5, OpenBSD, Darwin (more testing
+needed before claiming support for these OS).
+
+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:
+
+- gcc 3.3 and 3.4 have a bug that prevents them from generating volatile
+ accesses to offsets in a TLS structure on 32-bit x86. These versions are
+ 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
+- 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 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.
+
+
+API
+---
+
+See the relevant API documentation files in doc/. The APIs provided by
+Userspace RCU are, by prefix:
+
+- rcu_ : Read-Copy Update (see doc/rcu-api.txt)
+- cmm_ : Concurrent Memory Model
+- caa_ : Concurrent Architecture Abstraction
+- cds_ : Concurrent Data Structures (see doc/cds-api.txt)
+- uatomic_: Userspace Atomic (see doc/uatomic-api.txt)
+
QUICK START GUIDE
-----------------
instead of inlines, so your application can link with the library.
* Linking with one of the libraries below is always necessary even for
LGPL and GPL applications.
+ * Define URCU_INLINE_SMALL_FUNCTIONS before including Userspace RCU
+ headers if you want Userspace RCU to inline small functions (10
+ lines or less) into the application. It can be used by applications
+ distributed under any kind of license, and does *not* make the
+ application a derived work of Userspace RCU.
-Usage of liburcu
+ Those small inlined functions are guaranteed to match the library
+ content as long as the library major version is unchanged.
+ Therefore, the application *must* be compiled with headers matching
+ the library major version number. Applications using
+ URCU_INLINE_SMALL_FUNCTIONS may be unable to use debugging
+ features of Userspace RCU without being recompiled.
- * #include <urcu.h>
- * Link the application with "-lurcu".
- * This is the preferred version of the library, both in terms of speed
- and flexibility. Requires a signal, typically SIGUSR1. Can be
- overridden with -DSIGURCU by modifying Makefile.build.inc.
-Usage of liburcu-mb
+Usage of liburcu
* #include <urcu.h>
- * Compile any _LGPL_SOURCE code using this library with "-DURCU_MB".
- * Link with "-lurcu-mb".
- * This version of the urcu library does not need to
- reserve a signal number. URCU_MB uses full memory barriers for
- readers. This eliminates the need for signals but results in slower
- reads.
+ * Link the application with "-lurcu".
+ * This is the preferred version of the library, in terms of
+ grace-period detection speed, read-side speed and flexibility.
+ Dynamically detects kernel support for sys_membarrier(). Falls back
+ on urcu-mb scheme if support is not present, which has slower
+ read-side.
Usage of liburcu-qsbr
the threads are not active. It provides the fastest read-side at the
expense of more intrusiveness in the application code.
+Usage of liburcu-mb
+
+ * #include <urcu.h>
+ * Compile any _LGPL_SOURCE code using this library with "-DRCU_MB".
+ * Link with "-lurcu-mb".
+ * This version of the urcu library uses memory barriers on the writer
+ and reader sides. This results in faster grace-period detection, but
+ results in slower reads.
+
+Usage of liburcu-signal
+
+ * #include <urcu.h>
+ * Compile any _LGPL_SOURCE code using this library with "-DRCU_SIGNAL".
+ * Link the application with "-lurcu-signal".
+ * Version of the library that requires a signal, typically SIGUSR1. Can
+ be overridden with -DSIGRCU by modifying Makefile.build.inc.
+
Usage of liburcu-bp
* #include <urcu-bp.h>
* Link with "-lurcu-bp".
* The BP library flavor stands for "bulletproof". It is specifically
designed to help tracing library to hook on applications without
- requiring to modify these applications. urcu_init(),
+ requiring to modify these applications. rcu_init(),
rcu_register_thread() and rcu_unregister_thread() all become nops.
The state is dealt with by the library internally at the expense of
read-side and write-side performance.
Usage of liburcu-defer
- * #include <urcu-defer.h>
- * Link with "-lurcu-defer"
- * Provides call_rcu() primitive to enqueue delayed callbacks. Queued
+ * Follow instructions for either liburcu, liburcu-qsbr,
+ liburcu-mb, liburcu-signal, or liburcu-bp above.
+ The liburcu-defer functionality is pulled into each of
+ those library modules.
+ * Provides defer_rcu() primitive to enqueue delayed callbacks. Queued
callbacks are executed in batch periodically after a grace period.
- Do _not_ use call_rcu() within a read-side critical section, because
+ Do _not_ use defer_rcu() within a read-side critical section, because
it may call synchronize_rcu() if the thread queue is full.
+ This can lead to deadlock or worse.
+ * Requires that rcu_defer_barrier() must be called in library destructor
+ if a library queues callbacks and is expected to be unloaded with
+ dlclose().
+ * Its API is currently experimental. It may change in future library
+ releases.
+
+Usage of urcu-call-rcu
+
+ * Follow instructions for either liburcu, liburcu-qsbr,
+ liburcu-mb, liburcu-signal, or liburcu-bp above.
+ The urcu-call-rcu functionality is provided for each of
+ these library modules.
+ * Provides the call_rcu() primitive to enqueue delayed callbacks
+ in a manner similar to defer_rcu(), but without ever delaying
+ for a grace period. On the other hand, call_rcu()'s best-case
+ overhead is not quite as good as that of defer_rcu().
+ * Provides call_rcu() to allow asynchronous handling of 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 rcu-api.txt in userspace-rcu documentation for more details.
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
rcu_quiescent_state() calls, when threads are put offline and around
calls to synchronize_rcu(). Even then, we do not recommend it.
+Interaction with mutexes
+
+ One must be careful to do not cause deadlocks due to interaction of
+ synchronize_rcu() and RCU read-side with mutexes. If synchronize_rcu()
+ is called with a mutex held, this mutex (or any mutex which has this
+ 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()).
+
+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().
+ 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.
+
Usage of DEBUG_RCU
DEBUG_RCU is used to add internal debugging self-checks to the
./configure --disable-smp-support
theoretically yielding slightly better performance.
+
+MAKE TARGETS
+------------
+
+In addition to the usual "make check" target, Userspace RCU features
+"make regtest" and "make bench" targets.
+
+make check: Short tests, meant to be run when rebuilding or porting
+ Userspace RCU.
+
+make regtest: Long (many hours) test, meant to be run when modifying
+ Userspace RCU or porting it to a new architecture or
+ operating system.
+
+make bench: Long (many hours) benchmarks.
+
+CONTACTS
+--------
+
+You can contact the maintainers on the following mailing list:
+lttng-dev@lists.lttng.org
projects / urcu.git / blobdiff