From: Benno Lossin <benno.lossin@proton.me>
To: Miguel Ojeda <ojeda@kernel.org>,
Wedson Almeida Filho <wedsonaf@gmail.com>,
Alex Gaynor <alex.gaynor@gmail.com>
Cc: "Boqun Feng" <boqun.feng@gmail.com>,
"Gary Guo" <gary@garyguo.net>,
"Björn Roy Baron" <bjorn3_gh@protonmail.com>,
"Benno Lossin" <benno.lossin@proton.me>,
"Alice Ryhl" <aliceryhl@google.com>,
"Andreas Hindborg" <nmi@metaspace.dk>,
rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org,
patches@lists.linux.dev
Subject: [PATCH] rust: types: make `Opaque` be `!Unpin`
Date: Fri, 30 Jun 2023 15:03:23 +0000 [thread overview]
Message-ID: <20230630150216.109789-1-benno.lossin@proton.me> (raw)
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>
---
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`.
--
2.41.0
next reply other threads:[~2023-06-30 15:03 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-30 15:03 Benno Lossin [this message]
2023-06-30 15:32 ` [PATCH] rust: types: make `Opaque` be `!Unpin` Alice Ryhl
2023-06-30 17:52 ` Gary Guo
2023-07-03 9:30 ` Andreas Hindborg (Samsung)
2023-08-09 23:21 ` Miguel Ojeda
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