118 lines · rust
1// SPDX-License-Identifier: GPL-2.02 3//! A kernel spinlock.4//!5//! This module allows Rust code to use the kernel's `spinlock_t`.6 7/// Creates a [`SpinLock`] initialiser with the given name and a newly-created lock class.8///9/// It uses the name if one is given, otherwise it generates one based on the file name and line10/// number.11#[macro_export]12macro_rules! new_spinlock {13 ($inner:expr $(, $name:literal)? $(,)?) => {14 $crate::sync::SpinLock::new(15 $inner, $crate::optional_name!($($name)?), $crate::static_lock_class!())16 };17}18pub use new_spinlock;19 20/// A spinlock.21///22/// Exposes the kernel's [`spinlock_t`]. When multiple CPUs attempt to lock the same spinlock, only23/// one at a time is allowed to progress, the others will block (spinning) until the spinlock is24/// unlocked, at which point another CPU will be allowed to make progress.25///26/// Instances of [`SpinLock`] need a lock class and to be pinned. The recommended way to create such27/// instances is with the [`pin_init`](crate::pin_init) and [`new_spinlock`] macros.28///29/// # Examples30///31/// The following example shows how to declare, allocate and initialise a struct (`Example`) that32/// contains an inner struct (`Inner`) that is protected by a spinlock.33///34/// ```35/// use kernel::sync::{new_spinlock, SpinLock};36///37/// struct Inner {38/// a: u32,39/// b: u32,40/// }41///42/// #[pin_data]43/// struct Example {44/// c: u32,45/// #[pin]46/// d: SpinLock<Inner>,47/// }48///49/// impl Example {50/// fn new() -> impl PinInit<Self> {51/// pin_init!(Self {52/// c: 10,53/// d <- new_spinlock!(Inner { a: 20, b: 30 }),54/// })55/// }56/// }57///58/// // Allocate a boxed `Example`.59/// let e = Box::pin_init(Example::new(), GFP_KERNEL)?;60/// assert_eq!(e.c, 10);61/// assert_eq!(e.d.lock().a, 20);62/// assert_eq!(e.d.lock().b, 30);63/// # Ok::<(), Error>(())64/// ```65///66/// The following example shows how to use interior mutability to modify the contents of a struct67/// protected by a spinlock despite only having a shared reference:68///69/// ```70/// use kernel::sync::SpinLock;71///72/// struct Example {73/// a: u32,74/// b: u32,75/// }76///77/// fn example(m: &SpinLock<Example>) {78/// let mut guard = m.lock();79/// guard.a += 10;80/// guard.b += 20;81/// }82/// ```83///84/// [`spinlock_t`]: srctree/include/linux/spinlock.h85pub type SpinLock<T> = super::Lock<T, SpinLockBackend>;86 87/// A kernel `spinlock_t` lock backend.88pub struct SpinLockBackend;89 90// SAFETY: The underlying kernel `spinlock_t` object ensures mutual exclusion. `relock` uses the91// default implementation that always calls the same locking method.92unsafe impl super::Backend for SpinLockBackend {93 type State = bindings::spinlock_t;94 type GuardState = ();95 96 unsafe fn init(97 ptr: *mut Self::State,98 name: *const core::ffi::c_char,99 key: *mut bindings::lock_class_key,100 ) {101 // SAFETY: The safety requirements ensure that `ptr` is valid for writes, and `name` and102 // `key` are valid for read indefinitely.103 unsafe { bindings::__spin_lock_init(ptr, name, key) }104 }105 106 unsafe fn lock(ptr: *mut Self::State) -> Self::GuardState {107 // SAFETY: The safety requirements of this function ensure that `ptr` points to valid108 // memory, and that it has been initialised before.109 unsafe { bindings::spin_lock(ptr) }110 }111 112 unsafe fn unlock(ptr: *mut Self::State, _guard_state: &Self::GuardState) {113 // SAFETY: The safety requirements of this function ensure that `ptr` is valid and that the114 // caller is the owner of the spinlock.115 unsafe { bindings::spin_unlock(ptr) }116 }117}118