Re: [PATCH v9 2/2] rust: xarray: Add an abstraction for XArray

[Tamir Duberstein <tamird@gmail.com>]

On Mon, Nov 18, 2024 at 5:18 PM Boqun Feng <boqun.feng@gmail.com> wrote:
>
> On Mon, Nov 18, 2024 at 11:33:36AM -0500, Tamir Duberstein wrote:
> [...]
> > +
> > +/// A lock guard.
> > +///
> > +/// The lock is unlocked when the guard goes out of scope.
> > +#[must_use = "the lock unlocks immediately when the guard is unused"]
> > +pub struct Guard<'a, T: ForeignOwnable> {
> > +    xa: &'a XArray<T>,
> > +}
>
> `Guard` would be `Send` if `XArray<T>` is `Sync`, however, it's
> incorrect since `Guard` represents an xa_lock() held, and that's a
> spin_lock, so cannot be dropped on another thread/context. `Guard`
> should probably be marked as `!Send`. Or am I missing something subtle
> here?

I didn't know about this requirement, thanks for calling it out. I
have added `_not_send: PhantomData<*mut ()>` in v10.