This patch set adds support for TSAN in liburcu.
* Change since v1
** Adding CMM_SEQ_CST_FENCE memory order to the CMM memory model
The C11 memory model is incompatible with the memory model used by liburcu,
since the semantic of the C11 memory model is based on a happen-before
(acquire/release) relationship of memory accesses, while liburcu is based on
memory barriers and relaxed memory accesses.
To circumvent this, a new memory order called CMM_SEQ_CST_FENCE is
introduced. It implies a CMM_SEQ_CST while emitting a thread fence after the
operation. Operations that were documented as emitting memory barriers
before and after the operation are implemented now in term of this new memory
order to keep compatibility.
However, this model is redundant in some cases and the memory orders were
changed internally in liburcu to simply use the CMM_SEQ_CST.
** Adding cmm_emit_legacy_smp_mb() to queue/stack APIs
The queue/stack APIs document implicit memory barriers before or after
operation. These are now optionally emitted only if
CONFIG_RCU_EMIT_LEGACY_MB is defined in urcu/config.h or manually defined by
the user before including liburcu. That way, users can opt-in even if the
system headers were configured without this feature.
However, users can not opt-out of that feature if configured by the system.
* v1
** Here are the major changes
- Usage of compiler atomic builtins is added to the uatomic API. This is
required for TSAN to understand atomic memory accesses. If the compiler
supports such builtins, they are used by default. User can opt-out and use
the legacy implementation of the uatomic API by using the
`--disable-atomic-builtins' configuration option.
- The CMM memory model is introduced but yet formalized. It tries to be as
close as possible to the C11 memory model while offering primitives such as
cmm_smp_wmb(), cmm_smp_rmb() and cmm_mb() that can't be expressed in it.
For example, cmm_mb() can be used for ordering memory accesses to MMIO
devices, which is out of the scope of the C11 memory model.
- The CMM annotation layer is a new public API that is highly experimental and
not guaranteed to be stable at this stage. It serves the dual purpose of
verifying local (intra-thread) relaxed atomic accesses ordering with a
memory barrier and global (inter-thread) relaxed atomic accesses with a
shared state. The second purpose is necessary for TSAN to understand memory
accesses ordering since it does not fully support thread fence yet.
** CMM annotation example
Consider the following pseudo-code of writer side in synchronize_rcu(). An
acquire group is defined on the stack of the writer. Annotations are made
onto the group to ensure ordering of relaxed memory accesses in reader_state()
before the memory barrier at the end of synchronize_rcu(). It also helps TSAN
to understand that the relaxed accesses in reader_state() act like acquire
accesses because of the memory barrier in synchronize_rcu().
In other words, the purpose of this annotation is to convert a group of
load-acquire memory operations into load-relaxed memory operations followed by
a single memory barrier. This highly benefits weakly ordered architectures by
having a constant number of memory barriers instead of being linearly
proportional to the number of loads. This does not benefit TSO
architectures.
Olivier Dion (12):
configure: Add --disable-atomic-builtins option
urcu/compiler: Use atomic builtins if configured
urcu/arch/generic: Use atomic builtins if configured
urcu/system: Use atomic builtins if configured
urcu/uatomic: Add CMM memory model
urcu-wait: Fix wait state load/store
tests: Use uatomic for accessing global states
benchmark: Use uatomic for accessing global states
tests/unit/test_build: Quiet unused return value
urcu/annotate: Add CMM annotation
Add cmm_emit_legacy_smp_mb()
tests: Add tests for checking race conditions
README.md | 11 ++
configure.ac | 39 ++++
doc/uatomic-api.md | 3 +-
include/Makefile.am | 3 +
include/urcu/annotate.h | 174 ++++++++++++++++++
include/urcu/arch.h | 6 +
include/urcu/arch/generic.h | 37 ++++
include/urcu/compiler.h | 22 ++-
include/urcu/config.h.in | 6 +
include/urcu/static/lfstack.h | 25 ++-
include/urcu/static/pointer.h | 40 ++--
include/urcu/static/rculfqueue.h | 14 +-
include/urcu/static/rculfstack.h | 8 +-
include/urcu/static/urcu-bp.h | 12 +-
include/urcu/static/urcu-common.h | 8 +-
include/urcu/static/urcu-mb.h | 11 +-
include/urcu/static/urcu-memb.h | 26 ++-
include/urcu/static/urcu-qsbr.h | 29 ++-
include/urcu/static/wfcqueue.h | 68 +++----
include/urcu/static/wfqueue.h | 9 +-
include/urcu/static/wfstack.h | 24 ++-
include/urcu/system.h | 21 +++
include/urcu/uatomic.h | 63 ++++++-
include/urcu/uatomic/builtins-generic.h | 170 +++++++++++++++++
include/urcu/uatomic/builtins.h | 79 ++++++++
include/urcu/uatomic/generic.h | 234 ++++++++++++++++++++++++
src/rculfhash.c | 92 ++++++----
src/urcu-bp.c | 17 +-
src/urcu-pointer.c | 9 +-
src/urcu-qsbr.c | 31 +++-
src/urcu-wait.h | 15 +-
src/urcu.c | 24 ++-
tests/benchmark/Makefile.am | 91 ++++-----
tests/benchmark/common-states.c | 1 +
tests/benchmark/common-states.h | 51 ++++++
tests/benchmark/test_mutex.c | 32 +---
tests/benchmark/test_perthreadlock.c | 32 +---
tests/benchmark/test_rwlock.c | 32 +---
tests/benchmark/test_urcu.c | 33 +---
tests/benchmark/test_urcu_assign.c | 33 +---
tests/benchmark/test_urcu_bp.c | 33 +---
tests/benchmark/test_urcu_defer.c | 33 +---
tests/benchmark/test_urcu_gc.c | 34 +---
tests/benchmark/test_urcu_hash.c | 6 +-
tests/benchmark/test_urcu_hash.h | 15 --
tests/benchmark/test_urcu_hash_rw.c | 10 +-
tests/benchmark/test_urcu_hash_unique.c | 10 +-
tests/benchmark/test_urcu_lfq.c | 20 +-
tests/benchmark/test_urcu_lfs.c | 20 +-
tests/benchmark/test_urcu_lfs_rcu.c | 20 +-
tests/benchmark/test_urcu_qsbr.c | 33 +---
tests/benchmark/test_urcu_qsbr_gc.c | 34 +---
tests/benchmark/test_urcu_wfcq.c | 22 +--
tests/benchmark/test_urcu_wfq.c | 20 +-
tests/benchmark/test_urcu_wfs.c | 22 +--
tests/common/api.h | 12 +-
tests/regression/rcutorture.h | 106 +++++++----
tests/unit/test_build.c | 8 +-
tests/unit/test_lfstack.c | 90 +++++++++
tests/unit/test_wfcqueue.c | 119 ++++++++++++
tests/unit/test_wfqueue.c | 91 +++++++++
tests/unit/test_wfstack.c | 90 +++++++++
62 files changed, 1799 insertions(+), 684 deletions(-)
create mode 100644 include/urcu/annotate.h
create mode 100644 include/urcu/uatomic/builtins-generic.h
create mode 100644 include/urcu/uatomic/builtins.h
create mode 100644 tests/benchmark/common-states.c
create mode 100644 tests/benchmark/common-states.h
create mode 100644 tests/unit/test_lfstack.c
create mode 100644 tests/unit/test_wfcqueue.c
create mode 100644 tests/unit/test_wfqueue.c
create mode 100644 tests/unit/test_wfstack.c
--
2.40.1
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