linux-stable.git/rust/kernel/sync/arc.rs, branch linux-6.5.y

rust: delete `ForeignOwnable::borrow_mut`

2023-08-04T15:10:50+00:00

We discovered that the current design of `borrow_mut` is problematic.
This patch removes it until a better solution can be found.

Specifically, the current design gives you access to a `&mut T`, which
lets you change where the `ForeignOwnable` points (e.g., with
`core::mem::swap`). No upcoming user of this API intended to make that
possible, making all of them unsound.

Signed-off-by: Alice Ryhl 
Reviewed-by: Gary Guo 
Reviewed-by: Benno Lossin 
Reviewed-by: Martin Rodriguez Reboredo 
Fixes: 0fc4424d24a2 ("rust: types: introduce `ForeignOwnable`")
Link: https://lore.kernel.org/r/20230706094615.3080784-1-aliceryhl@google.com
Signed-off-by: Miguel Ojeda

rust: sync: reword the `Arc` safety comment for `Sync`

2023-05-31T16:53:10+00:00

The safety comment on `impl Sync for Arc` references the Send safety
comment. This commit avoids that in case the two comments drift apart in
the future.

Suggested-by: Andreas Hindborg 
Signed-off-by: Alice Ryhl 
Reviewed-by: Andreas Hindborg 
Reviewed-by: Boqun Feng 
Reviewed-by: Martin Rodriguez Reboredo 
Reviewed-by: Benno Lossin 
Link: https://lore.kernel.org/r/20230531145939.3714886-3-aliceryhl@google.com
Signed-off-by: Miguel Ojeda

rust: sync: reword the `Arc` safety comment for `Send`

2023-05-31T16:53:10+00:00

The safety comment on `impl Send for Arc` talks about "directly"
accessing the value, when it really means "accessing the value with a
mutable reference". This commit clarifies that.

Suggested-by: Boqun Feng 
Signed-off-by: Alice Ryhl 
Reviewed-by: Andreas Hindborg 
Reviewed-by: Boqun Feng 
Reviewed-by: Gary Guo 
Reviewed-by: Martin Rodriguez Reboredo 
Reviewed-by: Benno Lossin 
Link: https://lore.kernel.org/r/20230531145939.3714886-2-aliceryhl@google.com
Signed-off-by: Miguel Ojeda

rust: sync: implement `AsRef` for `Arc`

2023-05-31T16:53:10+00:00

This trait lets you use `Arc` in code that is generic over smart
pointer types.

The `AsRef` trait should be implemented on all smart pointers. The
standard library also implements it on the ordinary `Arc`.

Co-developed-by: Wedson Almeida Filho 
Signed-off-by: Wedson Almeida Filho 
Signed-off-by: Alice Ryhl 
Reviewed-by: Martin Rodriguez Reboredo 
Reviewed-by: Benno Lossin 
Reviewed-by: Gary Guo 
Reviewed-by: Andreas Hindborg 
Link: https://lore.kernel.org/r/20230517200814.3157916-2-aliceryhl@google.com
Signed-off-by: Miguel Ojeda

rust: sync: add `Arc::ptr_eq`

2023-05-31T16:53:10+00:00

Add a method for comparing whether two `Arc` pointers reference the same
underlying object.

This comparison can already be done by getting a reference to the inner
values and comparing whether the references have the same address.
However, writing `Arc::ptr_eq(a, b)` is generally less error-prone than
doing the same check on the references, since you might otherwise
accidentally compare the two `&Arc` references instead, which wont
work because those are pointers to pointers to the inner value, when you
just want to compare the pointers to the inner value.

Also, this method might optimize better because getting a reference to
the inner value involves offsetting the pointer, which this method does
not need to do.

Co-developed-by: Wedson Almeida Filho 
Signed-off-by: Wedson Almeida Filho 
Signed-off-by: Alice Ryhl 
Reviewed-by: Benno Lossin 
Reviewed-by: Gary Guo 
Reviewed-by: Martin Rodriguez Reboredo 
Reviewed-by: Andreas Hindborg 
Link: https://lore.kernel.org/r/20230517200814.3157916-1-aliceryhl@google.com
Signed-off-by: Miguel Ojeda

rust: arc: fix intra-doc link in `Arc::init`

2023-05-31T14:12:06+00:00

`Arc::init` refers to `Arc::pin_init` via an intra-doc link
using the text `pin_init`, rather than more explicitly, which makes
`rustdoc` point it to the `pin_init!` macro instead.

This is required for the compiler upgrade since the newer `rustdoc`
would trigger the `broken_intra_doc_links` lint [1], but in this case
the macro was not the intended target to begin with, and so the actual
fix is to make it point to the right place, regardless of the upgrade.

Thus make it more explicit.

Fixes: 92c4a1e7e81c ("rust: init/sync: add `InPlaceInit` trait to pin-initialize smart pointers")
Link: https://github.com/rust-lang/rust/issues/106142 [1]
Reviewed-by: Gary Guo 
Reviewed-by: Benno Lossin 
Reviewed-by: Martin Rodriguez Reboredo 
Reviewed-by: Björn Roy Baron 
Tested-by: Ariel Miculas 
Tested-by: David Gow 
Tested-by: Boqun Feng 
Link: https://lore.kernel.org/r/20230418214347.324156-3-ojeda@kernel.org
Signed-off-by: Miguel Ojeda

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

2023-04-12T16:41:05+00:00

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`

2023-04-12T16:41:05+00:00

`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

2023-04-12T16:41:05+00:00

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

2023-04-12T16:41:05+00:00

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