./configure
make
make install
+ ldconfig
Hints: Forcing 32-bit build:
* CFLAGS="-m32 -g -O2" ./configure
ARCHITECTURES SUPPORTED
-----------------------
-Currently, x86 (i386, i486, i586, i686), x86 64-bit, PowerPC 32/64, S390, S390x
-and Sparcv9 32/64 are supported. Only tested on Linux so far, but should
-theoretically work on other operating systems.
+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.
+
+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:
+
+- 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 4.x gcc with atomic builtins
+ support.
+
QUICK START GUIDE
-----------------
* #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 -DSIGRCU by modifying Makefile.build.inc.
-
-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 does not need to
- reserve a signal number. RCU_MB uses full memory barriers for
- readers. This eliminates the need for signals but results in slower
- reads.
+ * 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>
Usage of liburcu-defer
- * #include <urcu-defer.h>
- * Link with "-lurcu-defer", and also with one of the urcu library
- (either urcu, urcu-bp, urcu-mb or urcu-qsbr).
+ * 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 defer_rcu() within a read-side critical section, because
it may call synchronize_rcu() if the thread queue is full.
- * Provides defer_rcu_ratelimit() primitive, which acts just like
- defer_rcu(), but takes an additional rate limiter callback forcing
- synchronized callback execution of the limiter returns non-zero.
+ 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 API.txt for more details.
+
Being careful with signals
The liburcu library uses signals internally. The signal handler is
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.
+
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.
+
+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().
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