atomic-polyfill
This crate polyfills atomics on targets where they're not available, using critical sections. It is intended to be a drop-in replacement for core::sync::atomic.
There is three "levels" of polyfilling:
- Native: No polyfilling is performed, the native
core::sync::atomic::AtomicXXis reexported. - CAS: Only compare-and-set operations are polyfilled, while loads and stores are native.
- Full: Both load/store and compare-and-set operations are polyfilled.
Target support
The right polyfill level is automatically picked based on the target and the atomic width:
| Target | Level | Level for u64/i64 |
|---|---|---|
| thumbv6m | CAS | Full |
| thumbv7*, thumbv8* | Native | Full |
| riscv32imc | Full1 | Full |
| riscv32imac | Native | Full |
| Other2 | Native | Native |
1: The hardware is capable of supporting atomic load/stores up to 32 bits, so this could be "CAS" instead of "Full". However, support for this is missing in Rust. See discussion here.
2: atomic-polyfill assumes unknown targets have full native support. This may not be true, in which case the
build may fail. PRs for polyfilling more targets are welcome :)
Note: polyfill is based on critical sections using the critical-section crate. The default implementation is based on disabling all interrupts, so it's unsound on multi-core targets. It is possible to supply a custom
critical section implementation, check the critical-section docs for details.
License
This work is licensed under either of
- Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
- MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)
at your option.
Contribution
Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.