The #[must_use] annotation is missing on Lock::try_lock

[Darksonn]

The Guard type for locks is marked with a #[must_use] annotation like this:

linux/rust/kernel/sync/lock.rs

Lines 162 to 163 in 40384c8

	#[must_use = "the lock unlocks immediately when the guard is unused"]
	pub struct Guard<'a, T: ?Sized, B: Backend> {

This means that trying to use Lock::lock without using the return value will result in a warning. However, this warning does not happen with Lock::try_lock, since it returns an Option<Guard<...>> and the Option type is not #[must_use].

linux/rust/kernel/sync/lock.rs

Lines 147 to 154 in 40384c8

	/// Tries to acquire the lock.
	///
	/// Returns a guard that can be used to access the data protected by the lock if successful.
	pub fn try_lock(&self) -> Option<Guard<'_, T, B>> {
	// SAFETY: The constructor of the type calls `init`, so the existence of the object proves
	// that `init` was called.
	unsafe { B::try_lock(self.state.get()).map(|state| Guard::new(self, state)) }
	}

To fix this, add a #[must_use] annotation to Lock::try_lock directly.

---

This requires submitting a proper patch to the LKML and the Rust for Linux mailing list. Please recall to test your changes (including generating the documentation if changed, running the Rust doctests if changed, etc.), to use a proper title for the commit, to sign your commit under the Developer's Certificate of Origin and to add a Suggested-by: tag and a Link: tag to this issue. Please see https://rust-for-linux.com/contributing for details.

Please take this issue only if you are new to the kernel development process and you would like to use it as a test to submit your first patch to the kernel. Please do not take it if you do not plan to make other contributions to the kernel.

[BorisChenCZY]

I'm new to the kernel development and rust also. Can I take this one?

[ojeda]

Of course, please go ahead!

[hz2]

@BorisChenCZY apologizes for not seeing this before submitting the patch, i'm also new to kernel development and would enjoy working on this with you.

i can try to cc you on the current mailing list thread for this patch if you're not already on the mailing list?

[BorisChenCZY]

That would be great. Thanks Regards, Boris

…

On Mon, Dec 9, 2024 at 3:52 AM hz2 ***@***.***> wrote: @BorisChenCZY <https://github.com/BorisChenCZY> apologizes for not seeing this before submitting the patch, i'm also new to kernel development and would enjoy working on this with you. i can try to cc you on the current mailing list thread for this patch if you're not already on the mailing list? — Reply to this email directly, view it on GitHub <#1133 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AEZG25VXLZRUXE4JDMYDBJT2ESPRPAVCNFSM6AAAAABTAAZMFKVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZDKMRWGM2TCNRXGY> . You are receiving this because you were mentioned.Message ID: ***@***.***>

[hz2]

@BorisChenCZY cc'd you into the email chain for the patch, also can find the in the archive