linux-stable.git/rust/kernel/sync, 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: introduce `CondVar`

2023-04-21T23:46:45+00:00

This is the traditional condition variable or monitor synchronisation
primitive. It is implemented with C's `wait_queue_head_t`.

It allows users to release a lock and go to sleep while guaranteeing
that notifications won't be missed. This is achieved by enqueuing a wait
entry before releasing the lock.

Cc: Peter Zijlstra 
Cc: Ingo Molnar 
Cc: Will Deacon 
Cc: Waiman Long 
Reviewed-by: Martin Rodriguez Reboredo 
Signed-off-by: Wedson Almeida Filho 
Reviewed-by: Alice Ryhl 
Link: https://lore.kernel.org/r/20230411054543.21278-12-wedsonaf@gmail.com
Signed-off-by: Miguel Ojeda

rust: lock: add `Guard::do_unlocked`

2023-04-21T23:46:30+00:00

It releases the lock, executes some function provided by the caller,
then reacquires the lock. This is preparation for the implementation of
condvars, which will sleep after between unlocking and relocking.

We need an explicit `relock` method for primitives like `SpinLock` that
have an irqsave variant: we use the guard state to determine if the lock
was originally acquired with the regular `lock` function or
`lock_irqsave`.

Reviewed-by: Martin Rodriguez Reboredo 
Signed-off-by: Wedson Almeida Filho 
Link: https://lore.kernel.org/rust-for-linux/20230412121431.41627-1-wedsonaf@gmail.com/
[ Removed the irqsave bits as discussed. ]
Signed-off-by: Miguel Ojeda

rust: sync: introduce `LockedBy`

2023-04-21T22:20:00+00:00

This allows us to have data protected by a lock despite not being
wrapped by it. Access is granted by providing evidence that the lock is
held by the caller.

Reviewed-by: Martin Rodriguez Reboredo 
Signed-off-by: Wedson Almeida Filho 
Reviewed-by: Benno Lossin 
Link: https://lore.kernel.org/r/20230411054543.21278-13-wedsonaf@gmail.com
Signed-off-by: Miguel Ojeda

rust: lock: introduce `SpinLock`

2023-04-21T22:20:00+00:00

This is the `spinlock_t` lock backend and allows Rust code to use the
kernel spinlock idiomatically.

Cc: Peter Zijlstra 
Cc: Ingo Molnar 
Cc: Will Deacon 
Cc: Waiman Long 
Reviewed-by: Martin Rodriguez Reboredo 
Signed-off-by: Wedson Almeida Filho 
Link: https://lore.kernel.org/r/20230419174426.132207-1-wedsonaf@gmail.com
Signed-off-by: Miguel Ojeda