linux/rust/kernel/sync/arc.rs, branch v6.4

rust: sync: add functions for initializing `UniqueArc>`

2023-04-12T16:41:05Z

Add two functions `init_with` and `pin_init_with` to `UniqueArc>` to initialize the memory of already allocated `UniqueArc`s. This is useful when you want to allocate memory check some condition inside of a context where allocation is forbidden and then conditionally initialize an object. Signed-off-by: Benno Lossin Reviewed-by: Gary Guo Reviewed-by: Alice Ryhl Reviewed-by: Andreas Hindborg Link: https://lore.kernel.org/r/20230408122429.1103522-16-y86-dev@protonmail.com Signed-off-by: Miguel Ojeda

rust: sync: reduce stack usage of `UniqueArc::try_new_uninit`

2023-04-12T16:41:05Z

`UniqueArc::try_new_uninit` calls `Arc::try_new(MaybeUninit::uninit())`. This results in the uninitialized memory being placed on the stack, which may be arbitrarily large due to the generic `T` and thus could cause a stack overflow for large types. Change the implementation to use the pin-init API which enables in-place initialization. In particular it avoids having to first construct and then move the uninitialized memory from the stack into the final location. Signed-off-by: Benno Lossin Reviewed-by: Alice Ryhl Reviewed-by: Gary Guo Reviewed-by: Andreas Hindborg Link: https://lore.kernel.org/r/20230408122429.1103522-15-y86-dev@protonmail.com Signed-off-by: Miguel Ojeda

rust: init/sync: add `InPlaceInit` trait to pin-initialize smart pointers

2023-04-12T16:41:05Z

The `InPlaceInit` trait that provides two functions, for initializing using `PinInit` and `Init`. It is implemented by `Arc`, `UniqueArc` and `Box`. Signed-off-by: Benno Lossin Reviewed-by: Alice Ryhl Reviewed-by: Gary Guo Reviewed-by: Andreas Hindborg Link: https://lore.kernel.org/r/20230408122429.1103522-9-y86-dev@protonmail.com Signed-off-by: Miguel Ojeda

rust: sync: change error type of constructor functions

2023-04-12T16:41:05Z

Change the error type of the constructors of `Arc` and `UniqueArc` to be `AllocError` instead of `Error`. This makes the API more clear as to what can go wrong when calling `try_new` or its variants. Signed-off-by: Benno Lossin Reviewed-by: Andreas Hindborg Reviewed-by: Alice Ryhl Reviewed-by: Gary Guo Link: https://lore.kernel.org/r/20230408122429.1103522-4-y86-dev@protonmail.com Signed-off-by: Miguel Ojeda

rust: sync: arc: Add UniqueArc::assume_init()

2023-04-12T16:41:04Z

We can already create `UniqueArc>` instances with `UniqueArc::try_new_uninit()` and write to them with `write()`. Add the missing unsafe `assume_init()` function to promote it to `UniqueArc`, so users can do piece-wise initialization of the contents instead of doing it all at once as long as they keep the invariants (the same requirements as `MaybeUninit::assume_init()`). This mirrors the std `Arc::assume_init()` function. In the kernel, since we have `UniqueArc`, arguably this only belongs there since most use cases will initialize it immediately after creating it, before demoting it to `Arc` to share it. [ Miguel: The "Rust pin-init API for pinned initialization of structs" patch series [1] from Benno Lossin contains a very similar patch: rust: sync: add `assume_init` to `UniqueArc` Adds the `assume_init` function to `UniqueArc>` that unsafely assumes the value to be initialized and yields a value of type `UniqueArc`. This function is used when manually initializing the pointee of an `UniqueArc`. To make that patch a noop and thus drop it, I adjusted the `SAFETY` comment here to be the same as in the current latest version of that series (v7). I have also brought the `Reviewed-by`s there into here, and reworded the `Co-authored-by` into `Co-developed-by`. ] Link: https://lore.kernel.org/r/20230408122429.1103522-5-y86-dev@protonmail.com [1] Co-developed-by: Benno Lossin Signed-off-by: Benno Lossin Signed-off-by: Asahi Lina Reviewed-by: Gary Guo Reviewed-by: Wedson Almeida Filho Reviewed-by: Andreas Hindborg Reviewed-by: Alice Ryhl Link: https://lore.kernel.org/r/20230224-rust-arc-v2-2-5c97a865b276@asahilina.net Signed-off-by: Miguel Ojeda

rust: sync: arc: Implement Arc::downcast()

2023-04-10T21:55:43Z

This mirrors the standard library's alloc::sync::Arc::downcast(). Based on the Rust standard library implementation, ver 1.62.0, licensed under "Apache-2.0 OR MIT", from: https://github.com/rust-lang/rust/tree/1.62.0/library/alloc/src For copyright details, please see: https://github.com/rust-lang/rust/blob/1.62.0/COPYRIGHT Reviewed-by: Martin Rodriguez Reboredo Reviewed-by: Andreas Hindborg Reviewed-by: Vincenzo Palazzo Reviewed-by: Gary Guo Signed-off-by: Asahi Lina Link: https://lore.kernel.org/r/20230224-rust-arc-v2-1-5c97a865b276@asahilina.net [ Moved `mod std_vendor;` up. ] Signed-off-by: Miguel Ojeda

rust: sync: impl {Debug,Display} for {Unique,}Arc

2023-04-10T03:05:39Z

This allows printing the inner data of `Arc` and its friends if the inner data implements `Display` or `Debug`. It's useful for logging and debugging purpose. Signed-off-by: Boqun Feng Reviewed-by: Vincenzo Palazzo Reviewed-by: Gary Guo Reviewed-by: Andreas Hindborg Reviewed-by: Björn Roy Baron Link: https://lore.kernel.org/r/20230207185216.1314638-2-boqun.feng@gmail.com Signed-off-by: Miguel Ojeda

rust: types: implement `ForeignOwnable` for `Arc`

2023-02-07T10:24:24Z

This allows us to hand ownership of Rust ref-counted objects to the C side of the kernel. Signed-off-by: Wedson Almeida Filho Reviewed-by: Gary Guo Reviewed-by: Vincenzo Palazzo Reviewed-by: Alice Ferrazzi Reviewed-by: Andreas Hindborg Signed-off-by: Miguel Ojeda

rust: sync: add support for dispatching on Arc and ArcBorrow.

2023-01-16T22:48:06Z

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` and `ArcBorrow<'_, T>` to the list of allowed types. Signed-off-by: Wedson Almeida Filho Reviewed-by: Alice Ryhl Reviewed-by: Gary Guo Reviewed-by: Vincenzo Palazzo Acked-by: Boqun Feng Signed-off-by: Miguel Ojeda

rust: sync: introduce `UniqueArc`

2023-01-16T22:48:06Z

Since `Arc` does not allow mutating `T` directly (i.e., without inner mutability), it is currently not possible to do some initialisation of `T` post construction but before being shared. `UniqueArc` addresses this problem essentially being an `Arc` that has a refcount of 1 and is therefore writable. Once initialisation is completed, it can be transitioned (without failure paths) into an `Arc`. Suggested-by: Gary Guo Signed-off-by: Wedson Almeida Filho Reviewed-by: Alice Ryhl Reviewed-by: Gary Guo Reviewed-by: Vincenzo Palazzo Acked-by: Boqun Feng Signed-off-by: Miguel Ojeda