X-Git-Url: https://git.liburcu.org/?p=urcu.git;a=blobdiff_plain;f=README;h=4423fc53821c0c62244481cd8e94d8e4c837fc4f;hp=d454757fceffa30e7622d64dfee07290537bb0ee;hb=0ecb3fde04135d76545ce55d80abea9aef465b54;hpb=c51e75e62494c2f6aae4a88aa4499444716846d7 diff --git a/README b/README index d454757..4423fc5 100644 --- a/README +++ b/README @@ -9,20 +9,36 @@ BUILDING make make install - Note: Forcing 32-bit build: - * CFLAGS=-m32 ./configure + Hints: Forcing 32-bit build: + * CFLAGS="-m32 -g -O2" ./configure Forcing 64-bit build: - * CFLAGS=-m64 ./configure + * CFLAGS="-m64 -g -O2" ./configure + + 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 (only Pentium and +), 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. Also, the restriction against i386 and i486 might go away if we -integrate some of glibc runtime CPU-detection tests. +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. + +Alpha and ia64 architectures are supported, but depend on 4.x gcc with atomic +builtins support. + +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 QUICK START GUIDE ----------------- @@ -40,19 +56,11 @@ Usage of liburcu * #include * 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 - - * #include - * 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. + * 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 @@ -64,13 +72,30 @@ 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 + * 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 + * 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 * 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. @@ -98,11 +123,20 @@ Writing Usage of liburcu-defer * #include - * Link with "-lurcu-defer" - * Provides call_rcu() primitive to enqueue delayed callbacks. Queued + * Link with "-lurcu-defer", and also with one of the urcu library + (either urcu, urcu-bp, urcu-mb or urcu-qsbr). + * 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. + * 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. + * 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. Being careful with signals @@ -125,6 +159,14 @@ Being careful with signals 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 @@ -136,3 +178,13 @@ Usage of DEBUG_YIELD DEBUG_YIELD is used to add random delays in the code for testing purposes. + +SMP support + + By default the library is configured to use synchronization primitives + adequate for SMP systems. On uniprocessor systems, support for SMP + systems can be disabled with: + + ./configure --disable-smp-support + + theoretically yielding slightly better performance.