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

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Message-ID: <20250130-guard-get-lock-v1-1-8ed87899920a@google.com>
Date: Thu, 30 Jan 2025 11:39:32 +0000
From: Alice Ryhl <aliceryhl@...gle.com>
To: Miguel Ojeda <ojeda@...nel.org>
Cc: 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, Alice Ryhl <aliceryhl@...gle.com>
Subject: [PATCH] rust: sync: add accessor for the lock behind a given guard

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>
---
 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,
-- 
Alice Ryhl <aliceryhl@...gle.com>