On Wed, Feb 05, 2025 at 08:30:50PM +0000, Benno Lossin wrote:
> On 05.02.25 20:59, Mitchell Levy wrote:
> > diff --git a/rust/kernel/sync/lock.rs b/rust/kernel/sync/lock.rs
> > index 41dcddac69e2..119e5f569bdb 100644
> > --- a/rust/kernel/sync/lock.rs
> > +++ b/rust/kernel/sync/lock.rs
> > @@ -7,12 +7,9 @@
> >
> > use super::LockClassKey;
> > use crate::{
> > - init::PinInit,
> > - pin_init,
> > - str::CStr,
> > - types::{NotThreadSafe, Opaque, ScopeGuard},
> > + init::PinInit, pin_init, str::CStr, types::NotThreadSafe, types::Opaque, types::ScopeGuard,
> > };
> > -use core::{cell::UnsafeCell, marker::PhantomPinned};
> > +use core::{cell::UnsafeCell, marker::PhantomPinned, pin::Pin};
> > use macros::pin_data;
> >
> > pub mod mutex;
> > @@ -121,7 +118,7 @@ unsafe impl<T: ?Sized + Send, B: Backend> Sync for Lock<T, B> {}
> >
> > impl<T, B: Backend> Lock<T, B> {
> > /// Constructs a new lock initialiser.
> > - pub fn new(t: T, name: &'static CStr, key: &'static LockClassKey) -> impl PinInit<Self> {
> > + pub fn new(t: T, name: &'static CStr, key: Pin<&'static LockClassKey>) -> impl PinInit<Self> {
>
> Static references do not need `Pin`, since `Pin::static_ref` [1] exists,
> so you can just as well not add the `Pin` here and the other places
> where you have `Pin<&'static T>`.
>
You're right about `Pin` not needed for 'static. However, the
`Pin<&'static LockClassKey>` signature is the intermediate state, and
eventually we will need to support initializing a lock (and others) with
a dynamically allocated `LockClassKey`, and when that is available, the
type of `key` will become `Pin<&'a LockClassKey>`, so `Pin` is needed.
So I would like to keep this patch as it is. Works for you?
Regards,
Boqun
> The reasoning is that since the data lives for `'static` at that
> location, it will never move (since it is borrowed for `'static` after
> all).
>
> [1]: https://doc.rust-lang.org/std/pin/struct.Pin.html#method.static_ref
>
> ---
> Cheers,
> Benno
>
> > pin_init!(Self {
> > data: UnsafeCell::new(t),
> > _pin: PhantomPinned,
> > diff --git a/rust/kernel/sync/lock/global.rs b/rust/kernel/sync/lock/global.rs
> > index 480ee724e3cc..d65f94b5caf2 100644
> > --- a/rust/kernel/sync/lock/global.rs
> > +++ b/rust/kernel/sync/lock/global.rs
> > @@ -13,6 +13,7 @@
> > use core::{
> > cell::UnsafeCell,
> > marker::{PhantomData, PhantomPinned},
> > + pin::Pin,
> > };
> >
> > /// Trait implemented for marker types for global locks.
>
>
