linux-kernel - [tip: locking/core] rust: lock: Pin the inner data

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Message-ID: <176104292876.2601451.485431159015446694.tip-bot2@tip-bot2>
Date: Tue, 21 Oct 2025 10:35:28 -0000
From: "tip-bot2 for Daniel Almeida" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Benno Lossin <lossin@...nel.org>, Boqun Feng <boqun.feng@...il.com>,
 Daniel Almeida <daniel.almeida@...labora.com>,
 "Peter Zijlstra (Intel)" <peterz@...radead.org>,
 Alice Ryhl <aliceryhl@...gle.com>, x86@...nel.org,
 linux-kernel@...r.kernel.org
Subject: [tip: locking/core] rust: lock: Pin the inner data

The following commit has been merged into the locking/core branch of tip:

Commit-ID:     2497a7116ff9a051d0e78885a27a52213bc2841d
Gitweb:        https://git.kernel.org/tip/2497a7116ff9a051d0e78885a27a52213bc2841d
Author:        Daniel Almeida <daniel.almeida@...labora.com>
AuthorDate:    Fri, 19 Sep 2025 11:12:40 +02:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Tue, 21 Oct 2025 12:31:55 +02:00

rust: lock: Pin the inner data

In preparation to support Lock<T> where T is pinned, the first thing
that needs to be done is to structurally pin the 'data' member. This
switches the 't' parameter in Lock<T>::new() to take in an impl
PinInit<T> instead of a plain T. This in turn uses the blanket
implementation "impl PinInit<T> for T".

Subsequent patches will touch on Guard<T>.

Suggested-by: Benno Lossin <lossin@...nel.org>
Suggested-by: Boqun Feng <boqun.feng@...il.com>
Signed-off-by: Daniel Almeida <daniel.almeida@...labora.com>
Signed-off-by: Boqun Feng <boqun.feng@...il.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Reviewed-by: Benno Lossin <lossin@...nel.org>
Reviewed-by: Alice Ryhl <aliceryhl@...gle.com>
Link: https://github.com/Rust-for-Linux/linux/issues/1181
---
 rust/kernel/sync/lock.rs | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/rust/kernel/sync/lock.rs b/rust/kernel/sync/lock.rs
index b482f34..9242790 100644
--- a/rust/kernel/sync/lock.rs
+++ b/rust/kernel/sync/lock.rs
@@ -11,7 +11,7 @@ use crate::{
     types::{NotThreadSafe, Opaque, ScopeGuard},
 };
 use core::{cell::UnsafeCell, marker::PhantomPinned, pin::Pin};
-use pin_init::{pin_data, pin_init, PinInit};
+use pin_init::{pin_data, pin_init, PinInit, Wrapper};
 
 pub mod mutex;
 pub mod spinlock;
@@ -115,6 +115,7 @@ pub struct Lock<T: ?Sized, B: Backend> {
     _pin: PhantomPinned,
 
     /// The data protected by the lock.
+    #[pin]
     pub(crate) data: UnsafeCell<T>,
 }
 
@@ -127,9 +128,13 @@ unsafe impl<T: ?Sized + Send, B: Backend> Sync for Lock<T, B> {}
 
 impl<T, B: Backend> Lock<T, B> {
     /// Constructs a new lock initialiser.
-    pub fn new(t: T, name: &'static CStr, key: Pin<&'static LockClassKey>) -> impl PinInit<Self> {
+    pub fn new(
+        t: impl PinInit<T>,
+        name: &'static CStr,
+        key: Pin<&'static LockClassKey>,
+    ) -> impl PinInit<Self> {
         pin_init!(Self {
-            data: UnsafeCell::new(t),
+            data <- UnsafeCell::pin_init(t),
             _pin: PhantomPinned,
             // SAFETY: `slot` is valid while the closure is called and both `name` and `key` have
             // static lifetimes so they live indefinitely.