diff mbox series

[7/7] rust: sync: add support for dispatching on Arc and ArcBorrow.

Message ID 20221228060346.352362-7-wedsonaf@gmail.com
State New
Headers
Series [1/7] rust: sync: add `Arc` for ref-counted allocations |

Commit Message

Wedson Almeida Filho Dec. 28, 2022, 6:03 a.m. UTC 
  Trait objects (`dyn T`) require trait `T` to be "object safe". One of
the requirements for "object safety" is that the receiver have one of
the allowed types. This commit adds `Arc<T>` and `ArcBorrow<'_, T>` to
the list of allowed types.

Signed-off-by: Wedson Almeida Filho <wedsonaf@gmail.com>
---
 rust/kernel/lib.rs      |  1 +
 rust/kernel/sync/arc.rs | 20 ++++++++++++++++++--
 2 files changed, 19 insertions(+), 2 deletions(-)

Comments

Laine Taffin Altman Dec. 28, 2022, 7:24 a.m. UTC | #1 
On Dec 27, 2022, at 10:03 PM, Wedson Almeida Filho <wedsonaf@gmail.com> wrote:
> 
> Trait objects (`dyn T`) require trait `T` to be "object safe". One of
> the requirements for "object safety" is that the receiver have one of
> the allowed types. This commit adds `Arc<T>` and `ArcBorrow<'_, T>` to
> the list of allowed types.
> 
> Signed-off-by: Wedson Almeida Filho <wedsonaf@gmail.com>
> ---
> rust/kernel/lib.rs      |  1 +
> rust/kernel/sync/arc.rs | 20 ++++++++++++++++++--
> 2 files changed, 19 insertions(+), 2 deletions(-)
> 
> diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
> index 4bde65e7b06b..e0b0e953907d 100644
> --- a/rust/kernel/lib.rs
> +++ b/rust/kernel/lib.rs
> @@ -15,6 +15,7 @@
> #![feature(allocator_api)]
> #![feature(coerce_unsized)]
> #![feature(core_ffi_c)]
> +#![feature(dispatch_from_dyn)]
> #![feature(receiver_trait)]
> #![feature(unsize)]
> 
> diff --git a/rust/kernel/sync/arc.rs b/rust/kernel/sync/arc.rs
> index 832bafc74a90..ff73f9240ca1 100644
> --- a/rust/kernel/sync/arc.rs
> +++ b/rust/kernel/sync/arc.rs
> @@ -92,9 +92,15 @@ use core::{
> /// Coercion from `Arc<Example>` to `Arc<dyn MyTrait>`:
> ///
> /// ```
> -/// use kernel::sync::Arc;
> +/// use kernel::sync::{Arc, ArcBorrow};
> +///
> +/// trait MyTrait {
> +///     // Trait has a function whose `self` type is `Arc<Self>`.
> +///     fn example1(self: Arc<Self>) {}
> ///
> -/// trait MyTrait {}
> +///     // Trait has a function whose `self` type is `ArcBorrow<'_, Self>`.
> +///     fn example2(self: ArcBorrow<'_, Self>) {}
> +/// }
> ///
> /// struct Example;
> /// impl MyTrait for Example {}
> @@ -123,6 +129,9 @@ impl<T: ?Sized> core::ops::Receiver for Arc<T> {}
> // dynamically-sized type (DST) `U`.
> impl<T: ?Sized + Unsize<U>, U: ?Sized> core::ops::CoerceUnsized<Arc<U>> for Arc<T> {}
> 
> +// This is to allow `Arc<U>` to be dispatched on when `Arc<T>` can be coerced into `Arc<U>`.
> +impl<T: ?Sized + Unsize<U>, U: ?Sized> core::ops::DispatchFromDyn<Arc<U>> for Arc<T> {}
> +
> // SAFETY: It is safe to send `Arc<T>` to another thread when the underlying `T` is `Sync` because
> // it effectively means sharing `&T` (which is safe because `T` is `Sync`); additionally, it needs
> // `T` to be `Send` because any thread that has an `Arc<T>` may ultimately access `T` directly, for
> @@ -297,6 +306,13 @@ pub struct ArcBorrow<'a, T: ?Sized + 'a> {
> // This is to allow [`ArcBorrow`] (and variants) to be used as the type of `self`.
> impl<T: ?Sized> core::ops::Receiver for ArcBorrow<'_, T> {}
> 
> +// This is to allow `ArcBorrow<U>` to be dispatched on when `ArcBorrow<T>` can be coerced into
> +// `ArcBorrow<U>`.
> +impl<T: ?Sized + Unsize<U>, U: ?Sized> core::ops::DispatchFromDyn<ArcBorrow<'_, U>>
> +    for ArcBorrow<'_, T>

These lifetimes need to be tied together, I think.
`impl<'a, T: ?Sized + Unsize<U> + 'a, U: ?Sized + 'a> core::ops::DispatchFromDyn<ArcBorrow<'a, U>> for ArcBorrow<'a, T>`

> +{
> +}
> +
> impl<T: ?Sized> Clone for ArcBorrow<'_, T> {
>     fn clone(&self) -> Self {
>         *self
> --
> 2.34.1
> 
> 


— Laine Taffin Altman
Alice Ryhl Dec. 28, 2022, 10:04 a.m. UTC | #2 
Reviewed-by: Alice Ryhl <aliceryhl@google.com>

On 12/28/22 07:03, Wedson Almeida Filho wrote:
> Trait objects (`dyn T`) require trait `T` to be "object safe". One of
> the requirements for "object safety" is that the receiver have one of
> the allowed types. This commit adds `Arc<T>` and `ArcBorrow<'_, T>` to
> the list of allowed types.
> 
> Signed-off-by: Wedson Almeida Filho <wedsonaf@gmail.com>
> ---
>   rust/kernel/lib.rs      |  1 +
>   rust/kernel/sync/arc.rs | 20 ++++++++++++++++++--
>   2 files changed, 19 insertions(+), 2 deletions(-)
> 
> diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
> index 4bde65e7b06b..e0b0e953907d 100644
> --- a/rust/kernel/lib.rs
> +++ b/rust/kernel/lib.rs
> @@ -15,6 +15,7 @@
>   #![feature(allocator_api)]
>   #![feature(coerce_unsized)]
>   #![feature(core_ffi_c)]
> +#![feature(dispatch_from_dyn)]
>   #![feature(receiver_trait)]
>   #![feature(unsize)]
>   
> diff --git a/rust/kernel/sync/arc.rs b/rust/kernel/sync/arc.rs
> index 832bafc74a90..ff73f9240ca1 100644
> --- a/rust/kernel/sync/arc.rs
> +++ b/rust/kernel/sync/arc.rs
> @@ -92,9 +92,15 @@ use core::{
>   /// Coercion from `Arc<Example>` to `Arc<dyn MyTrait>`:
>   ///
>   /// ```
> -/// use kernel::sync::Arc;
> +/// use kernel::sync::{Arc, ArcBorrow};
> +///
> +/// trait MyTrait {
> +///     // Trait has a function whose `self` type is `Arc<Self>`.
> +///     fn example1(self: Arc<Self>) {}
>   ///
> -/// trait MyTrait {}
> +///     // Trait has a function whose `self` type is `ArcBorrow<'_, Self>`.
> +///     fn example2(self: ArcBorrow<'_, Self>) {}
> +/// }
>   ///
>   /// struct Example;
>   /// impl MyTrait for Example {}
> @@ -123,6 +129,9 @@ impl<T: ?Sized> core::ops::Receiver for Arc<T> {}
>   // dynamically-sized type (DST) `U`.
>   impl<T: ?Sized + Unsize<U>, U: ?Sized> core::ops::CoerceUnsized<Arc<U>> for Arc<T> {}
>   
> +// This is to allow `Arc<U>` to be dispatched on when `Arc<T>` can be coerced into `Arc<U>`.
> +impl<T: ?Sized + Unsize<U>, U: ?Sized> core::ops::DispatchFromDyn<Arc<U>> for Arc<T> {}
> +
>   // SAFETY: It is safe to send `Arc<T>` to another thread when the underlying `T` is `Sync` because
>   // it effectively means sharing `&T` (which is safe because `T` is `Sync`); additionally, it needs
>   // `T` to be `Send` because any thread that has an `Arc<T>` may ultimately access `T` directly, for
> @@ -297,6 +306,13 @@ pub struct ArcBorrow<'a, T: ?Sized + 'a> {
>   // This is to allow [`ArcBorrow`] (and variants) to be used as the type of `self`.
>   impl<T: ?Sized> core::ops::Receiver for ArcBorrow<'_, T> {}
>   
> +// This is to allow `ArcBorrow<U>` to be dispatched on when `ArcBorrow<T>` can be coerced into
> +// `ArcBorrow<U>`.
> +impl<T: ?Sized + Unsize<U>, U: ?Sized> core::ops::DispatchFromDyn<ArcBorrow<'_, U>>
> +    for ArcBorrow<'_, T>
> +{
> +}
> +
>   impl<T: ?Sized> Clone for ArcBorrow<'_, T> {
>       fn clone(&self) -> Self {
>           *self
Gary Guo Dec. 31, 2022, 7:51 p.m. UTC | #3 
On Tue, 27 Dec 2022 23:24:37 -0800
Laine Taffin Altman <alexanderaltman@me.com> wrote:

> > +// This is to allow `ArcBorrow<U>` to be dispatched on when `ArcBorrow<T>` can be coerced into
> > +// `ArcBorrow<U>`.
> > +impl<T: ?Sized + Unsize<U>, U: ?Sized> core::ops::DispatchFromDyn<ArcBorrow<'_, U>>
> > +    for ArcBorrow<'_, T>  
> 
> These lifetimes need to be tied together, I think.
> `impl<'a, T: ?Sized + Unsize<U> + 'a, U: ?Sized + 'a> core::ops::DispatchFromDyn<ArcBorrow<'a, U>> for ArcBorrow<'a, T>`

I don't think this is necessary, libcore has the following code
(https://doc.rust-lang.org/stable/src/core/ops/unsize.rs.html#123):

impl<'a, T: ?Sized + Unsize<U>, U: ?Sized> core::ops::DispatchFromDyn<&'a U> for &'a T {}

which should be equivalent to Wedson's lifetime elided version.

Best,
Gary
Gary Guo Dec. 31, 2022, 7:52 p.m. UTC | #4 
On Wed, 28 Dec 2022 06:03:46 +0000
Wedson Almeida Filho <wedsonaf@gmail.com> wrote:

> Trait objects (`dyn T`) require trait `T` to be "object safe". One of
> the requirements for "object safety" is that the receiver have one of
> the allowed types. This commit adds `Arc<T>` and `ArcBorrow<'_, T>` to
> the list of allowed types.
> 
> Signed-off-by: Wedson Almeida Filho <wedsonaf@gmail.com>

Reviewed-by: Gary Guo <gary@garyguo.net>

> ---
>  rust/kernel/lib.rs      |  1 +
>  rust/kernel/sync/arc.rs | 20 ++++++++++++++++++--
>  2 files changed, 19 insertions(+), 2 deletions(-)
> 
> diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
> index 4bde65e7b06b..e0b0e953907d 100644
> --- a/rust/kernel/lib.rs
> +++ b/rust/kernel/lib.rs
> @@ -15,6 +15,7 @@
>  #![feature(allocator_api)]
>  #![feature(coerce_unsized)]
>  #![feature(core_ffi_c)]
> +#![feature(dispatch_from_dyn)]
>  #![feature(receiver_trait)]
>  #![feature(unsize)]
>  
> diff --git a/rust/kernel/sync/arc.rs b/rust/kernel/sync/arc.rs
> index 832bafc74a90..ff73f9240ca1 100644
> --- a/rust/kernel/sync/arc.rs
> +++ b/rust/kernel/sync/arc.rs
> @@ -92,9 +92,15 @@ use core::{
>  /// Coercion from `Arc<Example>` to `Arc<dyn MyTrait>`:
>  ///
>  /// ```
> -/// use kernel::sync::Arc;
> +/// use kernel::sync::{Arc, ArcBorrow};
> +///
> +/// trait MyTrait {
> +///     // Trait has a function whose `self` type is `Arc<Self>`.
> +///     fn example1(self: Arc<Self>) {}
>  ///
> -/// trait MyTrait {}
> +///     // Trait has a function whose `self` type is `ArcBorrow<'_, Self>`.
> +///     fn example2(self: ArcBorrow<'_, Self>) {}
> +/// }
>  ///
>  /// struct Example;
>  /// impl MyTrait for Example {}
> @@ -123,6 +129,9 @@ impl<T: ?Sized> core::ops::Receiver for Arc<T> {}
>  // dynamically-sized type (DST) `U`.
>  impl<T: ?Sized + Unsize<U>, U: ?Sized> core::ops::CoerceUnsized<Arc<U>> for Arc<T> {}
>  
> +// This is to allow `Arc<U>` to be dispatched on when `Arc<T>` can be coerced into `Arc<U>`.
> +impl<T: ?Sized + Unsize<U>, U: ?Sized> core::ops::DispatchFromDyn<Arc<U>> for Arc<T> {}
> +
>  // SAFETY: It is safe to send `Arc<T>` to another thread when the underlying `T` is `Sync` because
>  // it effectively means sharing `&T` (which is safe because `T` is `Sync`); additionally, it needs
>  // `T` to be `Send` because any thread that has an `Arc<T>` may ultimately access `T` directly, for
> @@ -297,6 +306,13 @@ pub struct ArcBorrow<'a, T: ?Sized + 'a> {
>  // This is to allow [`ArcBorrow`] (and variants) to be used as the type of `self`.
>  impl<T: ?Sized> core::ops::Receiver for ArcBorrow<'_, T> {}
>  
> +// This is to allow `ArcBorrow<U>` to be dispatched on when `ArcBorrow<T>` can be coerced into
> +// `ArcBorrow<U>`.
> +impl<T: ?Sized + Unsize<U>, U: ?Sized> core::ops::DispatchFromDyn<ArcBorrow<'_, U>>
> +    for ArcBorrow<'_, T>
> +{
> +}
> +
>  impl<T: ?Sized> Clone for ArcBorrow<'_, T> {
>      fn clone(&self) -> Self {
>          *self
Vincenzo Palazzo Jan. 4, 2023, 4:26 p.m. UTC | #5 
On Wed Dec 28, 2022 at 7:03 AM CET, Wedson Almeida Filho wrote:
> Trait objects (`dyn T`) require trait `T` to be "object safe". One of
> the requirements for "object safety" is that the receiver have one of
> the allowed types. This commit adds `Arc<T>` and `ArcBorrow<'_, T>` to
> the list of allowed types.
>
> Signed-off-by: Wedson Almeida Filho <wedsonaf@gmail.com>

Reviewed-by: Vincenzo Palazzo <vincenzopalazzodev@gmail.com>
> ---
>  rust/kernel/lib.rs      |  1 +
>  rust/kernel/sync/arc.rs | 20 ++++++++++++++++++--
>  2 files changed, 19 insertions(+), 2 deletions(-)
>
> diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
> index 4bde65e7b06b..e0b0e953907d 100644
> --- a/rust/kernel/lib.rs
> +++ b/rust/kernel/lib.rs
> @@ -15,6 +15,7 @@
>  #![feature(allocator_api)]
>  #![feature(coerce_unsized)]
>  #![feature(core_ffi_c)]
> +#![feature(dispatch_from_dyn)]
>  #![feature(receiver_trait)]
>  #![feature(unsize)]
>  
> diff --git a/rust/kernel/sync/arc.rs b/rust/kernel/sync/arc.rs
> index 832bafc74a90..ff73f9240ca1 100644
> --- a/rust/kernel/sync/arc.rs
> +++ b/rust/kernel/sync/arc.rs
> @@ -92,9 +92,15 @@ use core::{
>  /// Coercion from `Arc<Example>` to `Arc<dyn MyTrait>`:
>  ///
>  /// ```
> -/// use kernel::sync::Arc;
> +/// use kernel::sync::{Arc, ArcBorrow};
> +///
> +/// trait MyTrait {
> +///     // Trait has a function whose `self` type is `Arc<Self>`.
> +///     fn example1(self: Arc<Self>) {}
>  ///
> -/// trait MyTrait {}
> +///     // Trait has a function whose `self` type is `ArcBorrow<'_, Self>`.
> +///     fn example2(self: ArcBorrow<'_, Self>) {}
> +/// }
>  ///
>  /// struct Example;
>  /// impl MyTrait for Example {}
> @@ -123,6 +129,9 @@ impl<T: ?Sized> core::ops::Receiver for Arc<T> {}
>  // dynamically-sized type (DST) `U`.
>  impl<T: ?Sized + Unsize<U>, U: ?Sized> core::ops::CoerceUnsized<Arc<U>> for Arc<T> {}
>  
> +// This is to allow `Arc<U>` to be dispatched on when `Arc<T>` can be coerced into `Arc<U>`.
> +impl<T: ?Sized + Unsize<U>, U: ?Sized> core::ops::DispatchFromDyn<Arc<U>> for Arc<T> {}
> +
>  // SAFETY: It is safe to send `Arc<T>` to another thread when the underlying `T` is `Sync` because
>  // it effectively means sharing `&T` (which is safe because `T` is `Sync`); additionally, it needs
>  // `T` to be `Send` because any thread that has an `Arc<T>` may ultimately access `T` directly, for
> @@ -297,6 +306,13 @@ pub struct ArcBorrow<'a, T: ?Sized + 'a> {
>  // This is to allow [`ArcBorrow`] (and variants) to be used as the type of `self`.
>  impl<T: ?Sized> core::ops::Receiver for ArcBorrow<'_, T> {}
>  
> +// This is to allow `ArcBorrow<U>` to be dispatched on when `ArcBorrow<T>` can be coerced into
> +// `ArcBorrow<U>`.
> +impl<T: ?Sized + Unsize<U>, U: ?Sized> core::ops::DispatchFromDyn<ArcBorrow<'_, U>>
> +    for ArcBorrow<'_, T>
> +{
> +}
> +
>  impl<T: ?Sized> Clone for ArcBorrow<'_, T> {
>      fn clone(&self) -> Self {
>          *self
> -- 
> 2.34.1
diff mbox series

Patch

diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index 4bde65e7b06b..e0b0e953907d 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -15,6 +15,7 @@ 
 #![feature(allocator_api)]
 #![feature(coerce_unsized)]
 #![feature(core_ffi_c)]
+#![feature(dispatch_from_dyn)]
 #![feature(receiver_trait)]
 #![feature(unsize)]
 
diff --git a/rust/kernel/sync/arc.rs b/rust/kernel/sync/arc.rs
index 832bafc74a90..ff73f9240ca1 100644
--- a/rust/kernel/sync/arc.rs
+++ b/rust/kernel/sync/arc.rs
@@ -92,9 +92,15 @@  use core::{
 /// Coercion from `Arc<Example>` to `Arc<dyn MyTrait>`:
 ///
 /// ```
-/// use kernel::sync::Arc;
+/// use kernel::sync::{Arc, ArcBorrow};
+///
+/// trait MyTrait {
+///     // Trait has a function whose `self` type is `Arc<Self>`.
+///     fn example1(self: Arc<Self>) {}
 ///
-/// trait MyTrait {}
+///     // Trait has a function whose `self` type is `ArcBorrow<'_, Self>`.
+///     fn example2(self: ArcBorrow<'_, Self>) {}
+/// }
 ///
 /// struct Example;
 /// impl MyTrait for Example {}
@@ -123,6 +129,9 @@  impl<T: ?Sized> core::ops::Receiver for Arc<T> {}
 // dynamically-sized type (DST) `U`.
 impl<T: ?Sized + Unsize<U>, U: ?Sized> core::ops::CoerceUnsized<Arc<U>> for Arc<T> {}
 
+// This is to allow `Arc<U>` to be dispatched on when `Arc<T>` can be coerced into `Arc<U>`.
+impl<T: ?Sized + Unsize<U>, U: ?Sized> core::ops::DispatchFromDyn<Arc<U>> for Arc<T> {}
+
 // SAFETY: It is safe to send `Arc<T>` to another thread when the underlying `T` is `Sync` because
 // it effectively means sharing `&T` (which is safe because `T` is `Sync`); additionally, it needs
 // `T` to be `Send` because any thread that has an `Arc<T>` may ultimately access `T` directly, for
@@ -297,6 +306,13 @@  pub struct ArcBorrow<'a, T: ?Sized + 'a> {
 // This is to allow [`ArcBorrow`] (and variants) to be used as the type of `self`.
 impl<T: ?Sized> core::ops::Receiver for ArcBorrow<'_, T> {}
 
+// This is to allow `ArcBorrow<U>` to be dispatched on when `ArcBorrow<T>` can be coerced into
+// `ArcBorrow<U>`.
+impl<T: ?Sized + Unsize<U>, U: ?Sized> core::ops::DispatchFromDyn<ArcBorrow<'_, U>>
+    for ArcBorrow<'_, T>
+{
+}
+
 impl<T: ?Sized> Clone for ArcBorrow<'_, T> {
     fn clone(&self) -> Self {
         *self