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Message-ID: <20230614115328.2825961-1-aliceryhl@google.com>
Date: Wed, 14 Jun 2023 11:53:28 +0000
From: Alice Ryhl <aliceryhl@...gle.com>
To: rust-for-linux@...r.kernel.org
Cc: Miguel Ojeda <ojeda@...nel.org>,
Wedson Almeida Filho <wedsonaf@...il.com>,
Alex Gaynor <alex.gaynor@...il.com>,
Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>,
"Björn Roy Baron" <bjorn3_gh@...tonmail.com>,
Benno Lossin <benno.lossin@...ton.me>,
Alice Ryhl <aliceryhl@...gle.com>,
linux-kernel@...r.kernel.org, patches@...ts.linux.dev
Subject: [PATCH] rust: make `UnsafeCell` the outer type in `Opaque`
When combining `UnsafeCell` with `MaybeUninit`, it is idiomatic to use
`UnsafeCell` as the outer type. Intuitively, this is because a
`MaybeUninit<T>` might not contain a `T`, but we always want the effect
of the `UnsafeCell`, even if the inner value is uninitialized.
Now, strictly speaking, this doesn't really make a difference. The
compiler will always apply the `UnsafeCell` effect even if the inner
value is uninitialized. But I think we should follow the convention
here.
Signed-off-by: Alice Ryhl <aliceryhl@...gle.com>
---
rust/kernel/types.rs | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/rust/kernel/types.rs b/rust/kernel/types.rs
index 1e5380b16ed5..fb41635f1e1f 100644
--- a/rust/kernel/types.rs
+++ b/rust/kernel/types.rs
@@ -224,17 +224,17 @@ 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>(MaybeUninit<UnsafeCell<T>>);
+pub struct Opaque<T>(UnsafeCell<MaybeUninit<T>>);
impl<T> Opaque<T> {
/// Creates a new opaque value.
pub const fn new(value: T) -> Self {
- Self(MaybeUninit::new(UnsafeCell::new(value)))
+ Self(UnsafeCell::new(MaybeUninit::new(value)))
}
/// Creates an uninitialised value.
pub const fn uninit() -> Self {
- Self(MaybeUninit::uninit())
+ Self(UnsafeCell::new(MaybeUninit::uninit()))
}
/// Creates a pin-initializer from the given initializer closure.
@@ -258,7 +258,7 @@ 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::raw_get(self.0.as_ptr())
+ UnsafeCell::get(&self.0).cast::<T>()
}
/// Gets the value behind `this`.
@@ -266,7 +266,7 @@ pub fn get(&self) -> *mut T {
/// This function is useful to get access to the value without creating intermediate
/// references.
pub const fn raw_get(this: *const Self) -> *mut T {
- UnsafeCell::raw_get(this.cast::<UnsafeCell<T>>())
+ UnsafeCell::raw_get(this.cast::<UnsafeCell<MaybeUninit<T>>>()).cast::<T>()
}
}
base-commit: d2e3115d717197cb2bc020dd1f06b06538474ac3
--
2.41.0.162.gfafddb0af9-goog
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