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Message-ID: <20250307232717.1759087-12-boqun.feng@gmail.com>
Date: Fri, 7 Mar 2025 15:27:01 -0800
From: Boqun Feng <boqun.feng@...il.com>
To: Ingo Molnar <mingo@...nel.org>,
Peter Zijlstra <peterz@...radead.org>
Cc: Will Deacon <will@...nel.org>,
Waiman Long <longman@...hat.com>,
linux-kernel@...r.kernel.org,
Mitchell Levy <levymitchell0@...il.com>,
Benno Lossin <benno.lossin@...ton.me>,
Boqun Feng <boqun.feng@...il.com>,
Miguel Ojeda <ojeda@...nel.org>,
Alex Gaynor <alex.gaynor@...il.com>,
Gary Guo <gary@...yguo.net>,
Björn Roy Baron <bjorn3_gh@...tonmail.com>,
Andreas Hindborg <a.hindborg@...nel.org>,
Alice Ryhl <aliceryhl@...gle.com>,
Trevor Gross <tmgross@...ch.edu>,
Ingo Molnar <mingo@...hat.com>,
Danilo Krummrich <dakr@...nel.org>,
Wedson Almeida Filho <wedsonaf@...il.com>,
Christian Brauner <brauner@...nel.org>,
Lyude Paul <lyude@...hat.com>,
Martin Rodriguez Reboredo <yakoyoku@...il.com>,
Konstantin Andrikopoulos <kernel@...dragore.io>,
Roland Xu <mu001999@...look.com>,
rust-for-linux@...r.kernel.org (open list:RUST)
Subject: [PATCH locking 11/11] rust: lockdep: Use Pin for all LockClassKey usages
From: Mitchell Levy <levymitchell0@...il.com>
Reintroduce dynamically-allocated LockClassKeys such that they are
automatically (de)registered. Require that all usages of LockClassKeys
ensure that they are Pin'd.
Currently, only `'static` LockClassKeys are supported, so Pin is
redundant. However, it is intended that dynamically-allocated
LockClassKeys will eventually be supported, so using Pin from the outset
will make that change simpler.
Closes: https://github.com/Rust-for-Linux/linux/issues/1102
Suggested-by: Benno Lossin <benno.lossin@...ton.me>
Suggested-by: Boqun Feng <boqun.feng@...il.com>
Signed-off-by: Mitchell Levy <levymitchell0@...il.com>
Reviewed-by: Benno Lossin <benno.lossin@...ton.me>
Signed-off-by: Boqun Feng <boqun.feng@...il.com>
Link: https://lore.kernel.org/r/20250207-rust-lockdep-v4-2-7a50a7e88656@gmail.com
---
rust/helpers/helpers.c | 1 +
rust/helpers/sync.c | 13 ++++++++
rust/kernel/sync.rs | 57 +++++++++++++++++++++++++++++++--
rust/kernel/sync/condvar.rs | 5 ++-
rust/kernel/sync/lock.rs | 4 +--
rust/kernel/sync/lock/global.rs | 5 +--
rust/kernel/sync/poll.rs | 2 +-
rust/kernel/workqueue.rs | 2 +-
8 files changed, 77 insertions(+), 12 deletions(-)
create mode 100644 rust/helpers/sync.c
diff --git a/rust/helpers/helpers.c b/rust/helpers/helpers.c
index 0640b7e115be..4c1a10a419cf 100644
--- a/rust/helpers/helpers.c
+++ b/rust/helpers/helpers.c
@@ -30,6 +30,7 @@
#include "signal.c"
#include "slab.c"
#include "spinlock.c"
+#include "sync.c"
#include "task.c"
#include "uaccess.c"
#include "vmalloc.c"
diff --git a/rust/helpers/sync.c b/rust/helpers/sync.c
new file mode 100644
index 000000000000..ff7e68b48810
--- /dev/null
+++ b/rust/helpers/sync.c
@@ -0,0 +1,13 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/lockdep.h>
+
+void rust_helper_lockdep_register_key(struct lock_class_key *k)
+{
+ lockdep_register_key(k);
+}
+
+void rust_helper_lockdep_unregister_key(struct lock_class_key *k)
+{
+ lockdep_unregister_key(k);
+}
diff --git a/rust/kernel/sync.rs b/rust/kernel/sync.rs
index 16eab9138b2b..4104bc26471a 100644
--- a/rust/kernel/sync.rs
+++ b/rust/kernel/sync.rs
@@ -5,6 +5,8 @@
//! This module contains the kernel APIs related to synchronisation that have been ported or
//! wrapped for usage by Rust code in the kernel.
+use crate::pin_init;
+use crate::prelude::*;
use crate::types::Opaque;
mod arc;
@@ -23,15 +25,64 @@
/// Represents a lockdep class. It's a wrapper around C's `lock_class_key`.
#[repr(transparent)]
-pub struct LockClassKey(Opaque<bindings::lock_class_key>);
+#[pin_data(PinnedDrop)]
+pub struct LockClassKey {
+ #[pin]
+ inner: Opaque<bindings::lock_class_key>,
+}
// SAFETY: `bindings::lock_class_key` is designed to be used concurrently from multiple threads and
// provides its own synchronization.
unsafe impl Sync for LockClassKey {}
impl LockClassKey {
+ /// Initializes a dynamically allocated lock class key. In the common case of using a
+ /// statically allocated lock class key, the static_lock_class! macro should be used instead.
+ ///
+ /// # Example
+ /// ```
+ /// # use kernel::{c_str, stack_pin_init};
+ /// # use kernel::alloc::KBox;
+ /// # use kernel::types::ForeignOwnable;
+ /// # use kernel::sync::{LockClassKey, SpinLock};
+ ///
+ /// let key = KBox::pin_init(LockClassKey::new_dynamic(), GFP_KERNEL)?;
+ /// let key_ptr = key.into_foreign();
+ ///
+ /// {
+ /// stack_pin_init!(let num: SpinLock<u32> = SpinLock::new(
+ /// 0,
+ /// c_str!("my_spinlock"),
+ /// // SAFETY: `key_ptr` is returned by the above `into_foreign()`, whose
+ /// // `from_foreign()` has not yet been called.
+ /// unsafe { <Pin<KBox<LockClassKey>> as ForeignOwnable>::borrow(key_ptr) }
+ /// ));
+ /// }
+ ///
+ /// // SAFETY: We dropped `num`, the only use of the key, so the result of the previous
+ /// // `borrow` has also been dropped. Thus, it's safe to use from_foreign.
+ /// unsafe { drop(<Pin<KBox<LockClassKey>> as ForeignOwnable>::from_foreign(key_ptr)) };
+ ///
+ /// # Ok::<(), Error>(())
+ /// ```
+ pub fn new_dynamic() -> impl PinInit<Self> {
+ pin_init!(Self {
+ // SAFETY: lockdep_register_key expects an uninitialized block of memory
+ inner <- Opaque::ffi_init(|slot| unsafe { bindings::lockdep_register_key(slot) })
+ })
+ }
+
pub(crate) fn as_ptr(&self) -> *mut bindings::lock_class_key {
- self.0.get()
+ self.inner.get()
+ }
+}
+
+#[pinned_drop]
+impl PinnedDrop for LockClassKey {
+ fn drop(self: Pin<&mut Self>) {
+ // SAFETY: self.as_ptr was registered with lockdep and self is pinned, so the address
+ // hasn't changed. Thus, it's safe to pass to unregister.
+ unsafe { bindings::lockdep_unregister_key(self.as_ptr()) }
}
}
@@ -44,7 +95,7 @@ macro_rules! static_lock_class {
// SAFETY: lockdep expects uninitialized memory when it's handed a statically allocated
// lock_class_key
unsafe { ::core::mem::MaybeUninit::uninit().assume_init() };
- &CLASS
+ $crate::prelude::Pin::static_ref(&CLASS)
}};
}
diff --git a/rust/kernel/sync/condvar.rs b/rust/kernel/sync/condvar.rs
index 5c1e546a26c3..fbf68ada582f 100644
--- a/rust/kernel/sync/condvar.rs
+++ b/rust/kernel/sync/condvar.rs
@@ -17,8 +17,7 @@
time::Jiffies,
types::Opaque,
};
-use core::marker::PhantomPinned;
-use core::ptr;
+use core::{marker::PhantomPinned, pin::Pin, ptr};
use macros::pin_data;
/// Creates a [`CondVar`] initialiser with the given name and a newly-created lock class.
@@ -103,7 +102,7 @@ unsafe impl Sync for CondVar {}
impl CondVar {
/// Constructs a new condvar initialiser.
- pub fn new(name: &'static CStr, key: &'static LockClassKey) -> impl PinInit<Self> {
+ pub fn new(name: &'static CStr, key: Pin<&'static LockClassKey>) -> impl PinInit<Self> {
pin_init!(Self {
_pin: PhantomPinned,
// SAFETY: `slot` is valid while the closure is called and both `name` and `key` have
diff --git a/rust/kernel/sync/lock.rs b/rust/kernel/sync/lock.rs
index f53e87d04cd2..360a10a9216d 100644
--- a/rust/kernel/sync/lock.rs
+++ b/rust/kernel/sync/lock.rs
@@ -12,7 +12,7 @@
str::CStr,
types::{NotThreadSafe, Opaque, ScopeGuard},
};
-use core::{cell::UnsafeCell, marker::PhantomPinned};
+use core::{cell::UnsafeCell, marker::PhantomPinned, pin::Pin};
use macros::pin_data;
pub mod mutex;
@@ -129,7 +129,7 @@ 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: &'static LockClassKey) -> impl PinInit<Self> {
+ pub fn new(t: T, name: &'static CStr, key: Pin<&'static LockClassKey>) -> impl PinInit<Self> {
pin_init!(Self {
data: UnsafeCell::new(t),
_pin: PhantomPinned,
diff --git a/rust/kernel/sync/lock/global.rs b/rust/kernel/sync/lock/global.rs
index 480ee724e3cc..d65f94b5caf2 100644
--- a/rust/kernel/sync/lock/global.rs
+++ b/rust/kernel/sync/lock/global.rs
@@ -13,6 +13,7 @@
use core::{
cell::UnsafeCell,
marker::{PhantomData, PhantomPinned},
+ pin::Pin,
};
/// Trait implemented for marker types for global locks.
@@ -26,7 +27,7 @@ pub trait GlobalLockBackend {
/// The backend used for this global lock.
type Backend: Backend + 'static;
/// The class for this global lock.
- fn get_lock_class() -> &'static LockClassKey;
+ fn get_lock_class() -> Pin<&'static LockClassKey>;
}
/// Type used for global locks.
@@ -270,7 +271,7 @@ impl $crate::sync::lock::GlobalLockBackend for $name {
type Item = $valuety;
type Backend = $crate::global_lock_inner!(backend $kind);
- fn get_lock_class() -> &'static $crate::sync::LockClassKey {
+ fn get_lock_class() -> Pin<&'static $crate::sync::LockClassKey> {
$crate::static_lock_class!()
}
}
diff --git a/rust/kernel/sync/poll.rs b/rust/kernel/sync/poll.rs
index d5f17153b424..c4934f82d68b 100644
--- a/rust/kernel/sync/poll.rs
+++ b/rust/kernel/sync/poll.rs
@@ -89,7 +89,7 @@ pub struct PollCondVar {
impl PollCondVar {
/// Constructs a new condvar initialiser.
- pub fn new(name: &'static CStr, key: &'static LockClassKey) -> impl PinInit<Self> {
+ pub fn new(name: &'static CStr, key: Pin<&'static LockClassKey>) -> impl PinInit<Self> {
pin_init!(Self {
inner <- CondVar::new(name, key),
})
diff --git a/rust/kernel/workqueue.rs b/rust/kernel/workqueue.rs
index 0cd100d2aefb..6b6f3ad08951 100644
--- a/rust/kernel/workqueue.rs
+++ b/rust/kernel/workqueue.rs
@@ -369,7 +369,7 @@ unsafe impl<T: ?Sized, const ID: u64> Sync for Work<T, ID> {}
impl<T: ?Sized, const ID: u64> Work<T, ID> {
/// Creates a new instance of [`Work`].
#[inline]
- pub fn new(name: &'static CStr, key: &'static LockClassKey) -> impl PinInit<Self>
+ pub fn new(name: &'static CStr, key: Pin<&'static LockClassKey>) -> impl PinInit<Self>
where
T: WorkItem<ID>,
{
--
2.47.1
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