Re: [PATCH v8 5/6] rust: ww_mutex: add Mutex, AcquireCtx and MutexGuard

[Alice Ryhl <aliceryhl@google.com>]

On Wed, Dec 03, 2025 at 02:23:14PM -0300, Daniel Almeida wrote:
> 
> 
> > On 3 Dec 2025, at 10:26, Alice Ryhl <aliceryhl@google.com> wrote:
> > 
> > On Mon, Dec 01, 2025 at 01:28:54PM +0300, Onur Özkan wrote:
> >> Yeah :(. We could get rid of them easily by keeping the class that was
> >> passed to the constructor functions but that becomes a problem for the
> >> from_raw implementations.
> >> 
> >> I think the best solution would be to expose ww_class type from
> >> ww_acquire_ctx and ww_mutex unconditionally (right now it depends on
> >> DEBUG_WW_MUTEXES). That way we can just access the class and verify
> >> that the mutex and acquire_ctx classes match.
> >> 
> >> What do you think? I can submit a patch for the C-side implementation.
> >> It should be straightforward and shouldn't have any runtime impact.
> > 
> > I think there is a better solution. We can create a different type for
> > every single class, like how rust/kernel/sync/lock/global.rs creates a
> > different type for every single mutex. Then, you know that the classes
> > are the same since the class is part of the type.
> 
> I don’t think this would work with the from_raw() functions. What class
> would you assign then? I think this is precisely what sparked the current
> solution.

There can be a way to create a type for a C-defined class, and
from_raw() can require that you don't use the same Rust type for
different C classes.

Alice