#atomic #polyfill #xtensa

archived no-std atomic-polyfill

Atomic polyfills, for targets where they're not available

5 releases (stable)

1.0.3 Jul 11, 2023
1.0.2 Mar 12, 2023
1.0.1 Aug 12, 2022
0.1.11 Nov 29, 2022
0.1.2 Mar 28, 2021
Download history 78092/week @ 2023-08-09 83204/week @ 2023-08-16 75847/week @ 2023-08-23 71220/week @ 2023-08-30 71529/week @ 2023-09-06 79595/week @ 2023-09-13 82770/week @ 2023-09-20 83910/week @ 2023-09-27 82050/week @ 2023-10-04 81959/week @ 2023-10-11 93378/week @ 2023-10-18 80206/week @ 2023-10-25 84007/week @ 2023-11-01 91867/week @ 2023-11-08 107674/week @ 2023-11-15 58046/week @ 2023-11-22

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Used in 765 crates (19 directly)


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Use portable-atomic instead. It supports many more architectures and more efficient ways of emulating atomics.

portable-atomic with the critical-section feature is a drop-in replacement. It uses the critical-section crate to ensure locking, just like atomic-polyfill.

However, if your chip is single-core, you might want to enable the unsafe-assume-single-core feature instead. It makes portable-atomic emulate atomics by disabling interrupts. It is faster than using a critical-section implementation that disables interrupts, because it allows disabling them only on CAS operations, not in load/store operations.

If you're writing a library, add a dependency on portable-atomic but do NOT enable any feature on it. Let the end user of your library enable the right features for their target. If you enable features, you're taking their choice away.



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 are two "levels" of polyfilling:

  • Native: No polyfilling is performed, the native core::sync::atomic::AtomicXX is reexported.
  • Full: Both load/store and compare-and-set operations are polyfilled.

Polyfilling requires a critical-section implementation for the current target. Check the critical-section README for details.

Target support

The right polyfill level is automatically picked based on the target and the atomic width:

Target Level Level for u64/i64
thumbv4t Full Full
thumbv6m Full Full
thumbv7*, thumbv8* Native Full
riscv32imc Full Full
riscv32imac Native Full
xtensa-*-espidf Native Native
xtensa-esp32-* Native Full
xtensa-esp32s2-* Full Full
xtensa-esp32s3-* Native Full
xtensa-esp8266-* Full Full
AVR Full Full

For targets not listed above, atomic-polyfill assumes nothing and reexports core::sync::atomic::*. No polyfilling is done. PRs for polyfilling more targets are welcome :)

Minimum Supported Rust Version (MSRV)

MSRV is currently Rust 1.54. MSRV may be upgraded at any new patch release as long as latest stable Rust is supported.


This work is licensed under either of

at your option.


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.