linux-kernel - Re: [PATCH] rust: sync: add accessor for the lock behind a given guard

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Message-ID: <87zfj8eczd.fsf@kloenk.dev>
Date: Thu, 30 Jan 2025 12:51:34 +0100
From: Fiona Behrens <me@...enk.dev>
To: Alice Ryhl <aliceryhl@...gle.com>
Cc: Miguel Ojeda <ojeda@...nel.org>,  Boqun Feng <boqun.feng@...il.com>,
  Gary Guo <gary@...yguo.net>,  Björn Roy Baron
 <bjorn3_gh@...tonmail.com>,  Benno Lossin <benno.lossin@...ton.me>,
  Andreas Hindborg <a.hindborg@...nel.org>,  Trevor Gross
 <tmgross@...ch.edu>,  Peter Zijlstra <peterz@...radead.org>,  Ingo Molnar
 <mingo@...hat.com>,  Will Deacon <will@...nel.org>,  Waiman Long
 <longman@...hat.com>,  rust-for-linux@...r.kernel.org,
  linux-kernel@...r.kernel.org
Subject: Re: [PATCH] rust: sync: add accessor for the lock behind a given guard

Alice Ryhl <aliceryhl@...gle.com> writes:

> Binder has some methods where the caller provides a lock guard, and
> Binder needs to be able to assert that the guard is associated with the
> right lock. To enable this, add an accessor to obtain a reference to the
> underlying lock that you can pass to `ptr::eq`.
>
> Signed-off-by: Alice Ryhl <aliceryhl@...gle.com>

Reviewed-by: Fiona Behrens <me@...enk.dev>

> ---
>  rust/kernel/sync/lock.rs | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/rust/kernel/sync/lock.rs b/rust/kernel/sync/lock.rs
> index 41dcddac69e2..681d67275b49 100644
> --- a/rust/kernel/sync/lock.rs
> +++ b/rust/kernel/sync/lock.rs
> @@ -169,7 +169,12 @@ pub struct Guard<'a, T: ?Sized, B: Backend> {
>  // SAFETY: `Guard` is sync when the data protected by the lock is also sync.
>  unsafe impl<T: Sync + ?Sized, B: Backend> Sync for Guard<'_, T, B> {}
>  
> -impl<T: ?Sized, B: Backend> Guard<'_, T, B> {
> +impl<'a, T: ?Sized, B: Backend> Guard<'a, T, B> {
> +    /// Returns the lock that this guard originates from.
> +    pub fn lock(&self) -> &'a Lock<T, B> {
> +        self.lock
> +    }
> +
>      pub(crate) fn do_unlocked<U>(&mut self, cb: impl FnOnce() -> U) -> U {
>          // SAFETY: The caller owns the lock, so it is safe to unlock it.
>          unsafe { B::unlock(self.lock.state.get(), &self.state) };
>
> ---
> base-commit: ceff0757f5dafb5be5205988171809c877b1d3e3
> change-id: 20250130-guard-get-lock-dd5452793d9a
>
> Best regards,