Update portable-atomic to 1

[taiki-e]

The main change in this release is adding an optional critical-section feature¹ to support custom critical section implementations with rust-embedded's critical-section crate. (taiki-e/portable-atomic#51) This allows portable-atomic to provide atomic CAS on multicore systems that do not have native atomic CAS instructions.

portable-atomic is not used in spin's public API and the (cfg) interfaces of portable-atomic 0.3 and portable-atomic 1.x are compatible, so this update should not be a breaking change. (taiki-e/portable-atomic#61 (comment))

Footnotes

1. This is a feature, not a cfg; critical-section 1.x doesn't provide the default or opt-in potentially unsound implementation (unlike critical-section 0.x where the implementation for single-core was enabled by default), and users must implement the critical-section implementation that sound for their system by implementing an unsafe trait (or to use the crate that provides such an implementation). So, we have determined that it is okay to treat this as a safe feature. ↩

[zesterer]

Thanks!

[zesterer]

Did you need this in a release?