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    SubjectRe: [PATCH v3 06/13] rust: lock: add support for `Lock::lock_irqsave`
    On 4/8/23 04:53, Wedson Almeida Filho wrote:
    > From: Wedson Almeida Filho <walmeida@microsoft.com>
    >
    > This allows locks like spinlocks and raw spinlocks to expose a
    > `lock_irqsave` variant in Rust that corresponds to the C version.
    >
    > Signed-off-by: Wedson Almeida Filho <walmeida@microsoft.com>
    > ---
    > v1 -> v2: No changes
    > v2 -> v3: No changes
    >
    > rust/kernel/sync/lock.rs | 38 ++++++++++++++++++++++++++++++++++++++
    > 1 file changed, 38 insertions(+)
    >
    > diff --git a/rust/kernel/sync/lock.rs b/rust/kernel/sync/lock.rs
    > index df43dff5af5c..690429561f0e 100644
    > --- a/rust/kernel/sync/lock.rs
    > +++ b/rust/kernel/sync/lock.rs
    > @@ -57,6 +57,29 @@ pub unsafe trait Backend {
    > unsafe fn unlock(ptr: *mut Self::State, guard_state: &Self::GuardState);
    > }
    >
    > +/// The "backend" of a lock that supports the irq-save variant.
    > +///
    > +/// # Safety
    > +///
    > +/// The same requirements wrt mutual exclusion in [`Backend`] apply for acquiring the lock via
    > +/// [`IrqSaveBackend::lock_irqsave`].
    > +///
    > +/// Additionally, when [`IrqSaveBackend::lock_irqsave`] is used to acquire the lock, implementers
    > +/// must disable interrupts on lock, and restore interrupt state on unlock. Implementers may use
    > +/// [`Backend::GuardState`] to store state needed to keep track of the interrupt state.
    > +pub unsafe trait IrqSaveBackend: Backend {
    > + /// Acquires the lock, making the caller its owner.
    > + ///
    > + /// Before acquiring the lock, it disables interrupts, and returns the previous interrupt state
    > + /// as its guard state so that the guard can restore it when it is dropped.
    > + ///
    > + /// # Safety
    > + ///
    > + /// Callers must ensure that [`Backend::init`] has been previously called.
    > + #[must_use]
    > + unsafe fn lock_irqsave(ptr: *mut Self::State) -> Self::GuardState;
    > +}
    > +
    > /// A mutual exclusion primitive.
    > ///
    > /// Exposes one of the kernel locking primitives. Which one is exposed depends on the lock banckend
    > @@ -111,6 +134,21 @@ impl<T: ?Sized, B: Backend> Lock<T, B> {
    > }
    > }
    >
    > +impl<T: ?Sized, B: IrqSaveBackend> Lock<T, B> {
    > + /// Acquires the lock and gives the caller access to the data protected by it.
    > + ///
    > + /// Before acquiring the lock, it disables interrupts. When the guard is dropped, the interrupt
    > + /// state (either enabled or disabled) is restored to its state before
    > + /// [`lock_irqsave`](Self::lock_irqsave) was called.
    > + pub fn lock_irqsave(&self) -> Guard<'_, T, B> {
    > + // SAFETY: The constructor of the type calls `init`, so the existence of the object proves
    > + // that `init` was called.
    > + let state = unsafe { B::lock_irqsave(self.state.get()) };
    > + // SAFETY: The lock was just acquired.
    > + unsafe { Guard::new(self, state) }
    > + }
    > +}
    > +
    > /// A lock guard.
    > ///
    > /// Allows mutual exclusion primitives that implement the `Backend` trait to automatically unlock

    Reviewed-by: Martin Rodriguez Reboredo <yakoyoku@gmail.com>

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