Re: [PATCH v1 0/2] Add atomic bool support

[Gary Guo <gary@garyguo.net>]

On Tue, 30 Dec 2025 13:50:26 +0900
FUJITA Tomonori <fujita.tomonori@gmail.com> wrote:

> This adds `bool` support to the Rust LKMM atomics.
> 
> Rust specifies that `bool` has size 1 and alignment 1 [1], so it can
> be represented using an `i8` backing type.
> 
> Since `bool` only permits the bit patterns 0x00 and 0x01, the first
> patch also documents an additional safety preconditions for unsafe
> `Atomic::<T>::from_ptr`.
> 
> `from_ptr()` exists to operate on C-side storage so I don't think it
> makes sense for bool. We could restrict from_ptr() via a marker trait.

The C-side does have `bool` type, too (`_Bool` has been there since C99 and
we have typedef'd it to `bool`). User might still want to perform relaxed
load/store on these C-side bool storage.

I think it's fine to leave out this line too (given Boqun also points out
that the additional safety precondition is not needed for `from_ptr).

Best,
Gary

> 
> [1] https://doc.rust-lang.org/reference/types/boolean.html
> 
> 
> FUJITA Tomonori (2):
>   rust: sync: atomic: Add atomic bool support via i8 representation
>   rust: sync: atomic: Add atomic bool tests
> 
>  rust/kernel/sync/atomic.rs           |  1 +
>  rust/kernel/sync/atomic/internal.rs  |  8 ++++++++
>  rust/kernel/sync/atomic/predefine.rs | 27 +++++++++++++++++++++++++++
>  3 files changed, 36 insertions(+)
> 
> base-commit: 13ade169e801a423bc1a5a5c3c6ac680a144a608