kernel/
sync.rs

1// SPDX-License-Identifier: GPL-2.0
2
3//! Synchronisation primitives.
4//!
5//! This module contains the kernel APIs related to synchronisation that have been ported or
6//! wrapped for usage by Rust code in the kernel.
7
8use crate::prelude::*;
9use crate::types::Opaque;
10use pin_init;
11
12mod arc;
13pub mod aref;
14pub mod atomic;
15pub mod barrier;
16pub mod completion;
17mod condvar;
18pub mod lock;
19mod locked_by;
20pub mod poll;
21pub mod rcu;
22mod refcount;
23mod set_once;
24
25pub use arc::{Arc, ArcBorrow, UniqueArc};
26pub use completion::Completion;
27pub use condvar::{new_condvar, CondVar, CondVarTimeoutResult};
28pub use lock::global::{global_lock, GlobalGuard, GlobalLock, GlobalLockBackend, GlobalLockedBy};
29pub use lock::mutex::{new_mutex, Mutex, MutexGuard};
30pub use lock::spinlock::{new_spinlock, SpinLock, SpinLockGuard};
31pub use locked_by::LockedBy;
32pub use refcount::Refcount;
33pub use set_once::SetOnce;
34
35/// Represents a lockdep class. It's a wrapper around C's `lock_class_key`.
36#[repr(transparent)]
37#[pin_data(PinnedDrop)]
38pub struct LockClassKey {
39    #[pin]
40    inner: Opaque<bindings::lock_class_key>,
41}
42
43// SAFETY: `bindings::lock_class_key` is designed to be used concurrently from multiple threads and
44// provides its own synchronization.
45unsafe impl Sync for LockClassKey {}
46
47impl LockClassKey {
48    /// Initializes a dynamically allocated lock class key. In the common case of using a
49    /// statically allocated lock class key, the static_lock_class! macro should be used instead.
50    ///
51    /// # Examples
52    /// ```
53    /// # use kernel::alloc::KBox;
54    /// # use kernel::types::ForeignOwnable;
55    /// # use kernel::sync::{LockClassKey, SpinLock};
56    /// # use pin_init::stack_pin_init;
57    ///
58    /// let key = KBox::pin_init(LockClassKey::new_dynamic(), GFP_KERNEL)?;
59    /// let key_ptr = key.into_foreign();
60    ///
61    /// {
62    ///     stack_pin_init!(let num: SpinLock<u32> = SpinLock::new(
63    ///         0,
64    ///         c"my_spinlock",
65    ///         // SAFETY: `key_ptr` is returned by the above `into_foreign()`, whose
66    ///         // `from_foreign()` has not yet been called.
67    ///         unsafe { <Pin<KBox<LockClassKey>> as ForeignOwnable>::borrow(key_ptr) }
68    ///     ));
69    /// }
70    ///
71    /// // SAFETY: We dropped `num`, the only use of the key, so the result of the previous
72    /// // `borrow` has also been dropped. Thus, it's safe to use from_foreign.
73    /// unsafe { drop(<Pin<KBox<LockClassKey>> as ForeignOwnable>::from_foreign(key_ptr)) };
74    ///
75    /// # Ok::<(), Error>(())
76    /// ```
77    pub fn new_dynamic() -> impl PinInit<Self> {
78        pin_init!(Self {
79            // SAFETY: lockdep_register_key expects an uninitialized block of memory
80            inner <- Opaque::ffi_init(|slot| unsafe { bindings::lockdep_register_key(slot) })
81        })
82    }
83
84    pub(crate) fn as_ptr(&self) -> *mut bindings::lock_class_key {
85        self.inner.get()
86    }
87}
88
89#[pinned_drop]
90impl PinnedDrop for LockClassKey {
91    fn drop(self: Pin<&mut Self>) {
92        // SAFETY: self.as_ptr was registered with lockdep and self is pinned, so the address
93        // hasn't changed. Thus, it's safe to pass to unregister.
94        unsafe { bindings::lockdep_unregister_key(self.as_ptr()) }
95    }
96}
97
98/// Defines a new static lock class and returns a pointer to it.
99#[doc(hidden)]
100#[macro_export]
101macro_rules! static_lock_class {
102    () => {{
103        static CLASS: $crate::sync::LockClassKey =
104            // Lockdep expects uninitialized memory when it's handed a statically allocated `struct
105            // lock_class_key`.
106            //
107            // SAFETY: `LockClassKey` transparently wraps `Opaque` which permits uninitialized
108            // memory.
109            unsafe { ::core::mem::MaybeUninit::uninit().assume_init() };
110        $crate::prelude::Pin::static_ref(&CLASS)
111    }};
112}
113
114/// Returns the given string, if one is provided, otherwise generates one based on the source code
115/// location.
116#[doc(hidden)]
117#[macro_export]
118macro_rules! optional_name {
119    () => {
120        $crate::c_str!(::core::concat!(::core::file!(), ":", ::core::line!()))
121    };
122    ($name:literal) => {
123        $crate::c_str!($name)
124    };
125}
kernel/sync.rs

kernel/
sync.rs
