Messages in this thread | | | From | "Andreas Hindborg (Samsung)" <> | Subject | Re: [PATCH] rust: types: make `Opaque` be `!Unpin` | Date | Mon, 03 Jul 2023 11:30:56 +0200 |
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Benno Lossin <benno.lossin@proton.me> writes:
> Adds a `PhantomPinned` field to `Opaque<T>`. This removes the last Rust > guarantee: the assumption that the type `T` can be freely moved. This is > not the case for many types from the C side (e.g. if they contain a > `struct list_head`). This change removes the need to add a > `PhantomPinned` field manually to Rust structs that contain C structs > which must not be moved. > > Signed-off-by: Benno Lossin <benno.lossin@proton.me> > ---
Reviewed-by: Andreas Hindborg <a.hindborg@samsung.com>
> This patch depends on the patch that swaps `UnsafeCell` with > `MaybeUninit` inside `Opaque` [1]. > > [1]: https://lore.kernel.org/rust-for-linux/20230614115328.2825961-1-aliceryhl@google.com/ > --- > rust/kernel/types.rs | 19 ++++++++++++++----- > 1 file changed, 14 insertions(+), 5 deletions(-) > > diff --git a/rust/kernel/types.rs b/rust/kernel/types.rs > index fb41635f1e1f..e664a2beef30 100644 > --- a/rust/kernel/types.rs > +++ b/rust/kernel/types.rs > @@ -6,7 +6,7 @@ > use alloc::boxed::Box; > use core::{ > cell::UnsafeCell, > - marker::PhantomData, > + marker::{PhantomData, PhantomPinned}, > mem::MaybeUninit, > ops::{Deref, DerefMut}, > ptr::NonNull, > @@ -224,17 +224,26 @@ fn drop(&mut self) { > /// > /// This is meant to be used with FFI objects that are never interpreted by Rust code. > #[repr(transparent)] > -pub struct Opaque<T>(UnsafeCell<MaybeUninit<T>>); > +pub struct Opaque<T> { > + value: UnsafeCell<MaybeUninit<T>>, > + _pin: PhantomPinned, > +} > > impl<T> Opaque<T> { > /// Creates a new opaque value. > pub const fn new(value: T) -> Self { > - Self(UnsafeCell::new(MaybeUninit::new(value))) > + Self { > + value: UnsafeCell::new(MaybeUninit::new(value)), > + _pin: PhantomPinned, > + } > } > > /// Creates an uninitialised value. > pub const fn uninit() -> Self { > - Self(UnsafeCell::new(MaybeUninit::uninit())) > + Self { > + value: UnsafeCell::new(MaybeUninit::uninit()), > + _pin: PhantomPinned, > + } > } > > /// Creates a pin-initializer from the given initializer closure. > @@ -258,7 +267,7 @@ pub fn ffi_init(init_func: impl FnOnce(*mut T)) -> impl PinInit<Self> { > > /// Returns a raw pointer to the opaque data. > pub fn get(&self) -> *mut T { > - UnsafeCell::get(&self.0).cast::<T>() > + UnsafeCell::get(&self.value).cast::<T>() > } > > /// Gets the value behind `this`.
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