X-Git-Url: http://git.lttng.org/?a=blobdiff_plain;f=README.md;h=cd24cc53ba0f3887d08c467be033f2e6af6f661d;hb=ed4c6ca597ff4211e1379a650403836fd59e9368;hp=2f088fe4d6f12d58affc05eef7c7f8cc2b7da85d;hpb=0af4b40c1b5d70e25321181f5c437982b132d034;p=userspace-rcu.git diff --git a/README.md b/README.md index 2f088fe..cd24cc5 100644 --- a/README.md +++ b/README.md @@ -38,7 +38,7 @@ Architectures supported Currently, the following architectures are supported: - x86 (i386, i486, i586, i686) - - amd64 / x86_64 + - amd64 / x86\_64 - PowerPC 32/64 - S390, S390x - ARM 32/64 @@ -72,6 +72,9 @@ Should also work on: Linux ARM depends on running a Linux kernel 2.6.15 or better, GCC 4.4 or better. +The C compiler used needs to support at least C99. The C++ compiler used +needs to support at least C++11. + 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: @@ -80,17 +83,20 @@ 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 + - GCC 3.3 cannot match the "xchg" instruction on 32-bit x86 build. - See http://kerneltrap.org/node/7507 + See - 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. + . - Linux aarch64 depends on GCC 5.1 or better because prior versions perform unsafe access to deallocated stack. Clang version 3.0 (based on LLVM 3.0) is supported. +Glibc >= 2.4 should work but the older version we test against is +currently 2.17. + For developers using the Git tree: This source tree is based on the autotools suite from GNU to simplify @@ -100,7 +106,7 @@ compile the git repository tree : - GNU autotools (automake >=1.12, autoconf >=2.69) (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/) + (for more information, go to ) 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 @@ -157,8 +163,8 @@ There are multiple flavors of liburcu available: - `signal`, - `bp`. -The API members start with the prefix "urcu__", where - is the chosen flavor name. +The API members start with the prefix `urcu__`, where +`` is the chosen flavor name. ### Usage of `liburcu-memb` @@ -170,7 +176,7 @@ 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. Use the --disable-sys-membarrier-fallback configure option +read-side. Use the `--disable-sys-membarrier-fallback` configure option to disable the fall back, thus requiring `sys_membarrier()` to be available. This gives a small speedup when `sys_membarrier()` is supported by the kernel, and aborts in the library constructor if not @@ -376,11 +382,12 @@ By default the library is configured with internal debugging self-checks disabled. For always-on debugging self-checks: - ./configure --enable-rcu-debug + + ./configure --enable-rcu-debug For fine grained enabling of debugging self-checks, build -userspace-rcu with DEBUG_RCU defined and compile dependent -applications with DEBUG_RCU defined when necessary. +userspace-rcu with `DEBUG_RCU` defined and compile dependent +applications with `DEBUG_RCU` defined when necessary. Warning: Enabling this feature result in a performance penalty. @@ -407,7 +414,7 @@ theoretically yielding slightly better performance. By default the library is configured with extra debugging checks for lock-free hash table iterator traversal disabled. -Building liburcu with --enable-cds-lfht-iter-debug and rebuilding +Building liburcu with `--enable-cds-lfht-iter-debug` and rebuilding application to match the ABI change allows finding cases where the hash table iterator is re-purposed to be used on a different hash table while still being used to iterate on a hash table. @@ -420,14 +427,42 @@ Make targets ------------ In addition to the usual `make check` target, Userspace RCU features -`make regtest` and `make bench` targets: +`make regtest`, `make short_bench` and `make long_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. + - `make short_bench`: short benchmarks, 3 seconds per test. + - `make long_bench`: long (many hours) benchmarks, 30 seconds per test. + + +Known issues +------------ + +There is an application vs library compatibility issue between +applications built using Userspace RCU 0.10 headers linked against +Userspace RCU 0.11 or 0.12 shared objects. The problem occurs as +follows: + + - An application executable is built with `_LGPL_SOURCE` defined, includes + any of the Userspace RCU 0.10 urcu flavor headers, and is built + without the `-fpic` compiler option. + + - The Userspace RCU 0.10 library shared objects are updated to 0.11 + or 0.12 without rebuilding the application. + + - The application will hang, typically when RCU grace period + (synchronize_rcu) is invoked. + +Some possible work-arounds for this are: + + - Rebuild the application against Userspace RCU 0.11+. + + - Rebuild the application with `-fpic`. + + - Upgrade Userspace RCU to 0.13+ without installing 0.11 nor 0.12. Contacts