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

[Alice Ryhl]

On Tue, Nov 19, 2024 at 5:24 PM Tamir Duberstein <tamird@xxxxxxxxx> wrote:
>
> On Mon, Nov 18, 2024 at 5:18 PM Boqun Feng <boqun.feng@xxxxxxxxx> 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.

You can use _nts: NotThreadSafe. The type in question has landed in
6.13 and is available in Linus's tree since yesterday.

Alice