X-Git-Url: http://git.liburcu.org/?p=urcu.git;a=blobdiff_plain;f=README;h=104ef2ab4eb481383b19c89dd7619b077d948680;hp=f7f0dece2249bb764af9932a35cbf1ca57abffa3;hb=53dae82521cfd35f6df58b85bd7f39f2aa20a231;hpb=4cf1675fa5feb3a2e9e9f965e516e55fbf411457 diff --git a/README b/README index f7f0dec..104ef2a 100644 --- a/README +++ b/README @@ -8,6 +8,7 @@ BUILDING ./configure make make install + ldconfig Hints: Forcing 32-bit build: * CFLAGS="-m32 -g -O2" ./configure @@ -28,7 +29,7 @@ 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. +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: @@ -38,8 +39,26 @@ 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 ARM architectures depend on 4.x gcc with atomic builtins - support. +- 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 + +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. QUICK START GUIDE @@ -124,22 +143,37 @@ Writing Usage of liburcu-defer - * #include - * 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 @@ -169,6 +203,15 @@ Interaction with mutexes 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()). + Usage of DEBUG_RCU DEBUG_RCU is used to add internal debugging self-checks to the @@ -204,3 +247,10 @@ Interaction with fork() 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().