linux-kernel - Re: [PATCH 2/3] rust: sync: Assert Lock::is

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Message-ID: <Zz5384uaZdsL306c@tardis.local>
Date: Wed, 20 Nov 2024 15:59:47 -0800
From: Boqun Feng <boqun.feng@...il.com>
To: Lyude Paul <lyude@...hat.com>
Cc: rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org,
	Miguel Ojeda <ojeda@...nel.org>,
	Alex Gaynor <alex.gaynor@...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>,
	Alice Ryhl <aliceryhl@...gle.com>, Trevor Gross <tmgross@...ch.edu>,
	Martin Rodriguez Reboredo <yakoyoku@...il.com>,
	Valentin Obst <kernel@...entinobst.de>,
	Filipe Xavier <felipe_life@...e.com>
Subject: Re: [PATCH 2/3] rust: sync: Assert Lock::is_locked in Guard::new for
 debug builds

On Wed, Nov 20, 2024 at 05:30:42PM -0500, Lyude Paul wrote:
> Since we're allowing code to unsafely claim that it's acquired a lock
> let's use the new Lock::is_locked() function so that when debug assertions
> are enabled, we can verify that the lock has actually been acquired.
> 
> Signed-off-by: Lyude Paul <lyude@...hat.com>
> ---
>  rust/kernel/sync/lock.rs | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/rust/kernel/sync/lock.rs b/rust/kernel/sync/lock.rs
> index 542f846ac02b2..0a7f2ed767423 100644
> --- a/rust/kernel/sync/lock.rs
> +++ b/rust/kernel/sync/lock.rs
> @@ -244,10 +244,17 @@ fn drop(&mut self) {
>  impl<'a, T: ?Sized, B: Backend> Guard<'a, T, B> {
>      /// Constructs a new immutable lock guard.
>      ///
> +    /// # Panics
> +    ///
> +    /// This function will panic if debug assertions are enabled and `lock` is not actually
> +    /// acquired.
> +    ///
>      /// # Safety
>      ///
>      /// The caller must ensure that it owns the lock.
>      pub unsafe fn new(lock: &'a Lock<T, B>, state: B::GuardState) -> Self {
> +        debug_assert!(lock.is_locked());

You should just use lockdep_assert_held() here, and there's no need for
new_unchecked().

Regards,
Boqun

> +
>          Self {
>              lock,
>              state,
> -- 
> 2.47.0
>