Modernize the concurrent-ruby-ext C extension#1105
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Sounds great, is it ready for review? |
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Not yet, I'll ping you when it is. This is hopefully the first PR of a few to modernize the extension and lay the groundwork for opt-in Ractor support across the atomic primitives. |
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Replace the per-platform CAS and memory-barrier code in `CAtomicReference`, `CAtomicBoolean`, and `CAtomicFixnum` with the helpers in `ruby/atomic.h`, and switch the three classes from the old `DATA_PTR` / `RUBY_NEVER_FREE` pattern to `TypedData_Make_Struct` with proper `dmark`, `dfree`, `dsize`, and (on Ruby >= 2.7) `dcompact`. All atomic primitives (load, set, CAS, exchange) are `static inline` in `atomic_reference.h` and shared across the three classes via a `CR_DEFINE_ATOMIC_DATA_TYPE` macro that keeps the three `rb_data_type_t` definitions in lock-step. Stores publish via `RUBY_ATOMIC_VALUE_SET` (or `__atomic_store_n` on Ruby < 4.0) so the "java volatile" semantics the docstring advertises are preserved across the modernization, and the corresponding `RB_OBJ_WRITTEN` announces the write barrier to the GC. `AtomicReference#get_and_set` now uses a single atomic exchange instead of a CAS retry loop. Each primitive prefers the `ruby/atomic.h` helper when its specific macro is defined and falls back to GCC/Clang `__atomic_*` builtins otherwise, since `RUBY_ATOMIC_PTR_LOAD` only landed in Ruby 3.3 and `RUBY_ATOMIC_VALUE_SET` in 4.0. GC compaction support is gated on `RUBY_API_VERSION_CODE >= 20700` via the `CR_GC_COMPACTION` macro; older Rubies fall back to `rb_gc_mark`. `extconf.rb` drops the `libkern/OSAtomic.h` probe and the `-march` flags, which no longer matter once we're on `ruby/atomic.h` or the compiler atomic builtins. No behavioral change to any public API; the spec suite passes unchanged, including the atomic specs under `GC.stress`.
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Replace the per-platform CAS and memory-barrier code in
CAtomicReference,CAtomicBoolean, andCAtomicFixnumwith the abstractions inruby/atomic.h, and switch the three classes from the oldDATA_PTR/RUBY_NEVER_FREEpattern toTypedData_Make_Structwithdmark,dfree,dsize, and (on Ruby >= 2.7)dcompact. Stores go throughRB_OBJ_WRITEand successful CAS calls fireRB_OBJ_WRITTEN, so write barriers are honored and GC compaction is supported.Two version-gated fallbacks keep us building back to Ruby 2.3:
ruby/atomic.honly became a public extension header in Ruby 3.0, soextconf.rbprobes for it viahave_header. When it isn't available the C code falls back to GCC/Clang__atomic_*builtins.CR_GC_COMPACTIONmacro gated onRUBY_API_VERSION_CODEselects betweenrb_gc_mark_movable/rb_gc_locationplus thedcompactslot and a plainrb_gc_markon older Rubies.extconf.rbalso drops thelibkern/OSAtomic.hprobe and the-marchflags, which no longer matter once we're onruby/atomic.hor the compiler atomic builtins.No behavioral change to any public API; the spec suite passes unchanged, including the atomic specs under
GC.stress.