rust: lock: introduce Mutex

This is the `struct mutex` lock backend and allows Rust code to use the
kernel mutex idiomatically.

Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Will Deacon <will@kernel.org>
Cc: Waiman Long <longman@redhat.com>
Reviewed-by: Martin Rodriguez Reboredo <yakoyoku@gmail.com>
Signed-off-by: Wedson Almeida Filho <walmeida@microsoft.com>
Link: https://lore.kernel.org/r/20230411054543.21278-3-wedsonaf@gmail.com
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
This commit is contained in:
Wedson Almeida Filho 2023-04-11 02:45:33 -03:00 committed by Miguel Ojeda
parent 76d4bd591e
commit 6d20d629c6
4 changed files with 128 additions and 0 deletions

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@ -22,6 +22,7 @@
#include <linux/build_bug.h>
#include <linux/err.h>
#include <linux/refcount.h>
#include <linux/mutex.h>
__noreturn void rust_helper_BUG(void)
{
@ -29,6 +30,12 @@ __noreturn void rust_helper_BUG(void)
}
EXPORT_SYMBOL_GPL(rust_helper_BUG);
void rust_helper_mutex_lock(struct mutex *lock)
{
mutex_lock(lock);
}
EXPORT_SYMBOL_GPL(rust_helper_mutex_lock);
refcount_t rust_helper_REFCOUNT_INIT(int n)
{
return (refcount_t)REFCOUNT_INIT(n);

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@ -11,6 +11,7 @@ mod arc;
pub mod lock;
pub use arc::{Arc, ArcBorrow, UniqueArc};
pub use lock::mutex::Mutex;
/// Represents a lockdep class. It's a wrapper around C's `lock_class_key`.
#[repr(transparent)]

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@ -10,6 +10,8 @@ use crate::{bindings, init::PinInit, pin_init, str::CStr, types::Opaque};
use core::{cell::UnsafeCell, marker::PhantomData, marker::PhantomPinned};
use macros::pin_data;
pub mod mutex;
/// The "backend" of a lock.
///
/// It is the actual implementation of the lock, without the need to repeat patterns used in all

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@ -0,0 +1,118 @@
// SPDX-License-Identifier: GPL-2.0
//! A kernel mutex.
//!
//! This module allows Rust code to use the kernel's `struct mutex`.
use crate::bindings;
/// Creates a [`Mutex`] initialiser with the given name and a newly-created lock class.
///
/// It uses the name if one is given, otherwise it generates one based on the file name and line
/// number.
#[macro_export]
macro_rules! new_mutex {
($inner:expr $(, $name:literal)? $(,)?) => {
$crate::sync::Mutex::new(
$inner, $crate::optional_name!($($name)?), $crate::static_lock_class!())
};
}
/// A mutual exclusion primitive.
///
/// Exposes the kernel's [`struct mutex`]. When multiple threads attempt to lock the same mutex,
/// only one at a time is allowed to progress, the others will block (sleep) until the mutex is
/// unlocked, at which point another thread will be allowed to wake up and make progress.
///
/// Since it may block, [`Mutex`] needs to be used with care in atomic contexts.
///
/// Instances of [`Mutex`] need a lock class and to be pinned. The recommended way to create such
/// instances is with the [`pin_init`](crate::pin_init) and [`new_mutex`] macros.
///
/// # Examples
///
/// The following example shows how to declare, allocate and initialise a struct (`Example`) that
/// contains an inner struct (`Inner`) that is protected by a mutex.
///
/// ```
/// use kernel::{init::InPlaceInit, init::PinInit, new_mutex, pin_init, sync::Mutex};
///
/// struct Inner {
/// a: u32,
/// b: u32,
/// }
///
/// #[pin_data]
/// struct Example {
/// c: u32,
/// #[pin]
/// d: Mutex<Inner>,
/// }
///
/// impl Example {
/// fn new() -> impl PinInit<Self> {
/// pin_init!(Self {
/// c: 10,
/// d <- new_mutex!(Inner { a: 20, b: 30 }),
/// })
/// }
/// }
///
/// // Allocate a boxed `Example`.
/// let e = Box::pin_init(Example::new())?;
/// assert_eq!(e.c, 10);
/// assert_eq!(e.d.lock().a, 20);
/// assert_eq!(e.d.lock().b, 30);
/// ```
///
/// The following example shows how to use interior mutability to modify the contents of a struct
/// protected by a mutex despite only having a shared reference:
///
/// ```
/// use kernel::sync::Mutex;
///
/// struct Example {
/// a: u32,
/// b: u32,
/// }
///
/// fn example(m: &Mutex<Example>) {
/// let mut guard = m.lock();
/// guard.a += 10;
/// guard.b += 20;
/// }
/// ```
///
/// [`struct mutex`]: ../../../../include/linux/mutex.h
pub type Mutex<T> = super::Lock<T, MutexBackend>;
/// A kernel `struct mutex` lock backend.
pub struct MutexBackend;
// SAFETY: The underlying kernel `struct mutex` object ensures mutual exclusion.
unsafe impl super::Backend for MutexBackend {
type State = bindings::mutex;
type GuardState = ();
unsafe fn init(
ptr: *mut Self::State,
name: *const core::ffi::c_char,
key: *mut bindings::lock_class_key,
) {
// SAFETY: The safety requirements ensure that `ptr` is valid for writes, and `name` and
// `key` are valid for read indefinitely.
unsafe { bindings::__mutex_init(ptr, name, key) }
}
unsafe fn lock(ptr: *mut Self::State) -> Self::GuardState {
// SAFETY: The safety requirements of this function ensure that `ptr` points to valid
// memory, and that it has been initialised before.
unsafe { bindings::mutex_lock(ptr) };
}
unsafe fn unlock(ptr: *mut Self::State, _guard_state: &Self::GuardState) {
// SAFETY: The safety requirements of this function ensure that `ptr` is valid and that the
// caller is the owner of the mutex.
unsafe { bindings::mutex_unlock(ptr) };
}
}