[lttng-dev] [RELEASE] Userspace RCU 0.10.0, 0.9.4, 0.8.10 (EOL)
Mathieu Desnoyers
mathieu.desnoyers at efficios.com
Tue Jun 13 00:16:12 UTC 2017
liburcu is a LGPLv2.1 userspace RCU (read-copy-update) library. This
data synchronization library provides read-side access which scales
linearly with the number of cores. It does so by allowing multiple
copies of a given data structure to live at the same time, and by
monitoring the data structure accesses to detect grace periods after
which memory reclamation is possible.
liburcu-cds provides efficient data structures based on RCU and
lock-free algorithms. Those structures include hash tables, queues,
stacks, and doubly-linked lists.
Version 0.10.0 of liburcu introduces mainly the following changes
over version 0.9.x:
- Introduce a urcu_ref_get_safe API, which can return a failure in
case of reference count overflow,
- Remove RCU caller context restrictions on RCU lock-free hash table
cds_lfht_destroy API:
Up to and including liburcu 0.9.x, the RCU lock-free hash table
required that the destroy function should not be called from
within RCU read-side critical sections. This is caused by the lazy
resize, which uses the call_rcu worker thread, even though all it
really needs is a workqueue/worker thread scheme.
Use the new internal workqueue API instead of call_rcu in rculfhash to
remove this restriction starting from liburcu 0.10.x.
- Allow forcing the use of the sys_membarrier() system call:
When using the default (liburcu.so) and bulletproof (liburcu-bp.so)
flavours of Userspace RCU, kernel support for sys-membarrier is detected
dynamically and stored in the rcu_has_sys_membarrier_memb and
urcu_bp_has_sys_membarrier global variables.
Checking the value of these variables adds a small but measurable overhead
to smp_mb_slave. On systems which support sys-membarrier, it would be
nice to have a way of avoiding that overhead.
Here is the proposed approach: if CONFIG_RCU_FORCE_SYS_MEMBARRIER is
defined then rcu_has_sys_membarrier_memb/urcu_bp_has_sys_membarrier are
replaced with the constant 1, eliminating the overhead in smp_mb_slave.
As a sanity check, support for sys-membarrier is still detected at
startup. A program using liburcu or liburcu-bp compiled with this option
aborts in the library constructor if the membarrier system call is not
supported by the operating system.
- Introduce support for NIOS2 and m68k architectures,
- ARM32: use lighter-weight dmb ish (inner shareable domain) for smp barrier,
- Introduce a --enable-rcu-debug configure option, which builds internal
RCU consistency checks into the library,
Versions 0.9.4 and 0.8.10 introduce an important fix for ARM32: a missing
release barrier was added before uatomic_xchg(). They introduce other minor
fixes.
liburcu 0.8.10 will be the last release of the stable-0.8 series.
liburcu stable-0.8 branch has now reached end of life with the release of
liburcu 0.10.0. Users of liburcu 0.8.x should upgrade to 0.10.x or 0.9.x.
Enjoy!
Mathieu
Project website: http://liburcu.org
Git repository: git://git.liburcu.org/urcu.git
Changelog:
2017-06-12 Userspace RCU 0.10.0
* Bump library soname due to urcu flavor structure change
* Cleanup: use mutex_lock() wrapper in rculfhash
* Use workqueue in rculfhash
* Implement urcu workqueues internal API
* Add support for m68k architecture
* Set -Wall globally in AM_CFLAGS
* Fix: remove double use of PTHREAD_CFLAGS
* Re-add PTHREAD_CFLAGS to global CFLAGS
* Fix: Don't override user variables within the build system
* Add report at the end of configure
* uatomic-api docs: use the third-person singular
* Add --enable-rcu-debug to configure
* ARM32: use dmb ish (inner shareable domain) for smp barriers
* Cleanup: remove cmm_wmb() from rcu_xchg_pointer and rcu_cmpxchg_pointer
* Fix: uatomic arm32: add missing release barrier before uatomic_xchg
* Tests: Add verbose support to test script
* Fix: add missing CONFIG_RCU_FORCE_SYS_MEMBARRIER to urcu/config.h.in
* Allow forcing the use of sys membarrier
* Fix: rcutorture: work-around signal issue on mac os x
* Fix: rcutorture should register thread using call_rcu
* Fix: add missing backslash in Makefile.am
* Fix: Do not use wildcards in include/Makefile.am
* Bump version to 0.10-pre
* Fix: check for rand_r() in compat-rand.h
* Fix: Move rand-compat to private src dir
* Fix: remove AC_FUNC_MALLOC from configure.ac
* Cleanup: Re-organise source dir
* Cleanup: remove leftover manual pthread detection
* Fix: update ax_pthread macro to handle newer clang
* Update library current version due to adding destroy API
* Fix: Use pthread_self to get threadid on OSX
* Fix: examples: use destroy API for queues/stacks
* Update library age due to new stack/queue destroy API
* Fix: tests: invoke destroy APIs for queues/stacks
* Fix: add missing destroy functions to queues/stack APIs
* Fix: add missing __cds_wfcq_init for LGPL API
* Fix: memory leak on hash table destroy
* Fix: Add failover for platforms without nproc
* Fix: use clock_get_time for caa_get_cycles fallback on MacOSX
* Fix: syscall-compat.h MacOSX support
* Fix: Add solaris-build.md to dist
* rculfhash: Documentation: clarify need for grace period before "re-using"
* Port: build shared libraries in Cygwin
* Port: fix compatibility header for Cygwin
* Add GNU Hurd support to syscall-compat.h
* Add support for aarch64_be
* Fix: urcu-bp: re-initialize list head on library exit
* bootstrap: Standardize on autoreconf -vi
* Harmonize bootstrap script across projects
* Fix: examples make distcheck failure
* wfcqueue: add C++ compatibility API
* Fix: CDS_WFCQ_WOULDBLOCK typing for c++
* Fix: configure.ac: check for possibly required libs for clock_gettime
* Support for NIOS2 architecture
* urcu_ref_get_safe: introduce new API
* Fix: handle reference count overflow
* Fix: compat_futex should work-around futex signal-restart kernel bug
* Support for Xeon-Phi with newer MPSS
* sparc64: allocate membarrier system call number
* hppa: allocate membarrier system call number
* Fix build on non-Linux Debian ports
* Fix: urcu-signal: smp_mb_master() needs registry lock
* Fix: rculfhash only needs to include urcu-pointers.h
* Fix: out-of-tree benchmark/regtest
* Fix: add missing regtest and benchmark files to dist tarball
* Fix: add missing run.sh to benchmark makefile
2017-06-12 Userspace RCU 0.9.4
* Fix: Don't override user variables within the build system
* Fix: uatomic arm32: add missing release barrier before uatomic_xchg
* Tests: Add verbose support to test script
2017-12-06 Userspace RCU 0.8.10 (End of Life)
* Fix: Don't override user variables within the build system
* Fix: uatomic arm32: add missing release barrier before uatomic_xchg
* Fix: rcutorture: work-around signal issue on mac os x
* Fix: rcutorture should register thread using call_rcu
* Fix: remove AC_FUNC_MALLOC from configure.ac
* Update library current version due to adding destroy API
* Fix: Use pthread_self to get threadid on OSX
* Fix: examples: use destroy API for queues/stacks
* Update library age due to new stack/queue destroy API
* Fix: tests: invoke destroy APIs for queues/stacks
* Fix: add missing destroy functions to queues/stack APIs
* Fix: memory leak on hash table destroy
* Fix: urcu-bp: re-initialize list head on library exit
* Fix: examples make distcheck failure
* Cleanup: remove unused return value warning from tests
--
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com
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