embedded-alloc Use critical-section for heap locking.

This uses critical_section::with instead of cortex_m::interrupt::free to acquire a critical section. This allows customizing the critical section implementation, to make it sound for multicore chips for example.

This is a breaking change, so it'll require a 0.5 release.

Interestingly this makes the crate not cortex-m specific anymore. Perhaps it could be renamed to something more general?

TODO

[x] Wait for cortex-m 0.7.6 release https://github.com/rust-embedded/cortex-m/pull/449

Aug 12 '22 13:08 Dirbaio

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @thalesfragoso (or someone else) soon.

Please see the contribution instructions for more information.

Aug 12 '22 13:08 rust-highfive

Maybe it should be embedded-alloc in line with other crates in this org?

Aug 12 '22 13:08 jonathanpallant

Maybe add a critical-section feature upstream to linked_list_allocator instead?

Sep 04 '22 14:09 reitermarkus

Having customizable critical sections also benefits the use case of the nRF softdevice (which requires users never to turn off interrupts completely).

If this requires an API change, it might be worth considering whether that change could also be used for non-critical-section exclusitivness. A concrete setup I have in mind is always failing attempts to allocate from interrupts (which in setups without context switching would mean that little to no is needed; of course, if critical_section also allows such a null-implementation, all the better).